Association between anti-F. hepatica antibody levels in milk and production losses in dairy cows

Water temperature and microenvironmental factors predict the presence and detection of the snail host of Fasciola hepatica in Andean Patagonia

The transmission of Fasciola hepatica occurs only where there are -or recently were- aquatic or amphibious snails of the Lymnaeidae family, the intermediate host of this parasite. Direct detection of these snails is time-consuming and imprecise, hindering accurate and detailed mapping of transmission risk. To identify which microenvironmental factors could be used as proxies for the occurrence of the lymnaeid snail Galba viator, a major intermediate host in South America, a total of 183 1-m2 quadrants across diverse water bodies in an endemic area in Andean Patagonia were manually timed-searched for snails and microenvironmental variables were registered. Data was analyzed using a Bayesian hierarchical occupancy model that assessed the effects of the microenvironmental variables on the presence of snails while considering imperfect snail detection. The model estimated that G. viator predominantly inhabits shallow aquatic environments, in the presence of grasses, where snails of the genus Biomphalaria are also detected, and with scarce tree canopy cover. Physical factors affecting occupancy presumably act as proxies for the average water temperature, while the temperature at the time of sampling was found to affect snail detectability. The identified variables are easy, fast, and inexpensive to measure, and can complement management decisions and risk maps based on coarser remote-sensing data, particularly relevant in a context of growing resistance to anthelminthic drugs.

Bayesian hierarchical modelling of the geospatial distribution of fasciolosis in dairy cattle and the impact on production: Application to the main milk-producing region (Galicia) in Spain

Fasciolosis caused by Fasciola hepatica is a common parasitic infection among cattle in many countries. Although infected adult cows rarely show overt clinical signs, milk production may be impaired. Thus, significant production losses may occur in dairy herds with a high prevalence of fasciolosis. In this study, Bayesian hierarchical modelling was used to estimate the geospatial distribution of dairy cattle fasciolosis and its impact on milk production. The study was conducted in Galicia, the main milk producing region in Spain and a geographically heterogeneous area. The aims were: 1) to model the geospatial distribution of fasciolosis in dairy herds in the study area, 2) to identify clusters of herds with a high prevalence of fasciolosis, and 3) to assess the effect of fasciolosis on milk yield and quality. A large number of dairy cattle farms (n = 4907), of which 1660 provided production records, were surveyed. Fasciola infection status was determined by applying the MM3-SERO ELISA test to bulk tank milk samples. A high probability of infection was predicted in several zones, particularly in the centre, northeast and southeast of Galicia. Conversely, the predicted probability was very low in some parts of the northwest of the region. Infections with high within-herd prevalence (> 25% lactating cows infected) predominated. High within-herd prevalence was associated with loss of milk production (-1.387 kg/cow/ day, on average). No association between Fasciola infection and either milk fat or protein content was observed. This study has generated the first maps of the spatial distribution of the probability of Fasciola infection in dairy cattle herds in Galicia. The maps presented here can be used for reference purposes, enabling the design of better targeted fasciolosis control programmes in the region. Use of Bayesian hierarchical statistical analysis enabled us to ascertain the uncertainty of the predictions and to account for the spatial autocorrelation in the data. It also enabled us to generate maps showing the residual spatial variation in milk production, a topic that may deserve more detailed study.

Random forest classification as a tool in epidemiological modelling: Identification of farm-specific characteristics relevant for the occurrence of Fasciola hepatica on German dairy farms

Fasciola hepatica is an internal parasite of both human and veterinary relevance. In order to control fasciolosis, a multitude of attempts to predict the risk of infection such as risk maps or forecasting models have been developed. These attempts mainly focused on the influence of geo-climatic and meteorological features. Predicting bovine fasciolosis on farm level taking into account farm-specific settings yet remains challenging. In the present study, a new methodology for this purpose, a data-driven machine learning approach using a random forest classification algorithm was applied to a cross-sectional data set of farm characteristics, management regimes, and farmer aspects within two structurally different dairying regions in Germany in order to identify factors relevant for the occurrence of F. hepatica that could predict farm-level bulk tank milk positivity. The resulting models identified farm-specific key aspects in regard to the presence of F. hepatica. In study region North, farm-level production parameters (farm-level milk yield, farm-level milk fat, farm-level milk protein), leg hygiene, body condition (prevalence of overconditioned and underconditioned cows, respectively) and pasture access were identified as features relevant in regard to farm-level F. hepatica positivity. In study region South, pasture access together with farm-level lameness prevalence, farm-level prevalence of hock lesions, herd size, parity, and farm-level milk fat appeared to be important covariates. The stratification of the analysis by study region allows for the extrapolation of the results to similar settings of dairy husbandry. The local, region-specific modelling of F. hepatica presence in this work contributes to the understanding of on-farm aspects of F. hepatica appearance. The applied technique represents a novel approach in this context to model epidemiological data on fasciolosis which allows for the identification of farms at risk and together with additional findings in regard to the epidemiology of fasciolosis, can facilitate risk assessment and deepen our understanding of on-farm drivers of the occurrence of F. hepatica.

A scoping review of the testing of bulk tank milk to detect nonbacterial pathogens or herd exposure to nonbacterial pathogens in dairy cattle

In this scoping review, we characterized the literature reporting on the testing of bulk milk samples to detect microorganisms other than bacteria that can cause diseases in dairy cattle, including viruses, helminths, algae, and protozoa. A search strategy was completed by screening databases, conference proceedings, animal health agency websites, disease surveillance program websites, and handbooks of cattle-related diagnostic tests for potentially relevant articles. Two reviewers independently screened articles in English, Portuguese, or Spanish; original studies reporting on the testing of farm-level, unprocessed bulk milk samples for presence of pathogens or specific antibodies against agents other than bacteria that can cause diseases in cows were retained. From all studies, we used spreadsheets to extract relevant information, including pathogen screened, test used, and country of origin of bulk milk samples. Additionally, for studies reporting sufficient data to estimate test characteristics, we extracted detailed information about herd eligibility, testing protocol, and herd-level infection definition. A total of 8,829 records were identified, from which 1,592 were retained and assessed for eligibility, and 306 were included. Bovine viral diarrhea virus, Fasciola hepatica, Ostertagia ostertagi, and bovine herpesvirus 1 were the most frequently screened agents, reported from 107, 45, 45, and 33 studies, respectively. Sensitivity of bulk milk ELISA to detect herds with animals infected by bovine herpesvirus 1 ranged from 2 to 100%, and was affected mostly by antigen selection, cut-off adopted, herd vaccination status, and seroprevalence of lactating cows. Bulk milk ELISA had very high specificity to detect herds free of bovine leukemia virus, and varying sensitivity to detect herds with infected animals, which depended on the within-herd seroprevalence of lactating cattle. As for bovine viral diarrhea virus, in general, the sensitivity of bulk milk ELISA was moderate to high (>80%) when infection status was defined based on presence of persistently infected cattle or a high proportion of seropositive lactating cattle. Nevertheless, bulk milk ELISA was not able to distinguish infected and noninfected herds based on presence of seropositive unvaccinated weanlings. The PCR or quantitative PCR protocols employed had very low sensitivities (<40%) and very high specificities (>95%) to classify bovine viral diarrhea virus infection status of dairy herds. Sensitivity and specificity of bulk milk ELISA to classify herds with regards to presence of F. hepatica- or O. ostertagi-parasitized cattle were generally high and driven mostly by the definition of herd infection status. Conversely, bulk milk ELISA demonstrated varying characteristics to detect herds with or without Dictyocaulus viviparus-parasitized cattle, depending primarily on the antigen selected and presence of cattle with clinical signs of lungworm infection.

A survey for antibodies against Fasciola hepatica in cattle and sheep in finland indicates a low level of exposure

BACKGROUND

Fasciolosis is a parasitic infection caused by the liver fluke Fasciola hepatica that can have a major economic impact on livestock industry. The prevalence of the disease has recently been increasing in many North European countries. The objective of this study was to determine the prevalence of antibody against F. hepatica in Finnish cattle herds and sheep flocks during 2019 by using a commercial enzyme-linked immunosorbent assay (ELISA). Randomly selected bulk tank milk samples were obtained from 660 dairy herds. Blood samples were collected at slaughterhouses from 1944 suckler cows from 309 herds and from 1120 sheep from 95 flocks.

RESULTS

Antibodies against F. hepatica were found in 0.45% (95% confidence interval (CI): 0.15-1.33) of the dairy herds and 0.97% (95% CI: 0.33-2.82) of the suckler cow herds. The seropositive herds were located in eastern and central Finland. None of the sampled sheep flocks tested had antibodies against F. hepatica (95% CI: 0-3.89). The results of the assays were compared with meat inspection data received from the slaughterhouses. All positive herds also had liver condemnations due to F. hepatica based on the meat inspection reports.

CONCLUSIONS

Compared to other North European countries, the prevalence of fasciolosis in Finland can be considered low, and according to meat inspection reports, there are no indications of the prevalence increasing in Finland.

Identification and prevalence of fluke infection in yak and Tibetan sheep around Qinghai Lake, China

Liver flukes (Fasciola spp.) and rumen flukes (Paramphistomum spp.) are significant parasites in livestock worldwide, and Fasciola spp. are considered an important zoonotic parasite. To our knowledge, there are no reports on fluke species identification and epidemiological prevalence in yak and Tibetan sheep around Qinghai Lake, China. Therefore, this study aimed to identify the major fluke species and determine the prevalence of fluke infections among yak and Tibetan sheep in this area. A total of 307 fecal samples were collected and fluke eggs identified using morphology and molecular methods. Our study is the first to display that the predominant fluke species were F. hepatica and P. leydeni in yak and Tibetan sheep around Qinghai Lake. The overall prevalence of fluke infections in yak and Tibetan sheep was 57.7% (177/307). Specifically, the prevalences of F. hepatica and P. leydeni were 15.0% (46/307) and 31.6% (97/307), respectively, and the co-infection of both species was 11.1% (34/307). No significant difference existed in the prevalence of overall fluke infection between yak and Tibetan sheep (p < 0.05). However, F. hepatica prevalence was significantly different in yak and Tibetan sheep (p < 0.05) but not P. leydeni. The findings of this study provide useful information about the current status of natural fluke invasion in yak and Tibetan sheep around Qinghai Lake, which could be important for monitoring and controlling these parasites in the region.

To treat or not to treat: diagnostic thresholds in subclinical helminth infections of cattle

Helminth infections of cattle place significant burdens on livestock production and farm economic efficiency. Heavy infections are relatively easy to detect and treat with anthelmintics. However, subclinical infections have major but often hidden impacts on animals, necessitating more refined diagnostics to detect them and ideally inform farmers about the likely impact of anthelmintic treatment on animal and herd performance. Here, we review recent advances in diagnosing three major cattle helminth infections - gastrointestinal nematodes (GINs), liver flukes, and lungworms - and the search for subclinical infection thresholds to guide treatment decisions. Combining refined diagnostic thresholds with farm-specific information on grazing systems and animal history enables farmers to tailor helminth treatments to specific epidemiological circumstances, thereby limiting anthelmintic resistance (AR) and boosting agricultural efficiency and food security.

A major locus confers triclabendazole resistance in Fasciola hepatica and shows dominant inheritance

Fasciola hepatica infection is responsible for substantial economic losses in livestock worldwide and poses a threat to human health in endemic areas. The mainstay of control in livestock and the only drug licenced for use in humans is triclabendazole (TCBZ). TCBZ resistance has been reported on every continent and threatens effective control of fasciolosis in many parts of the world. To date, understanding the genetic mechanisms underlying TCBZ resistance has been limited to studies of candidate genes, based on assumptions of their role in drug action. Taking an alternative approach, we combined a genetic cross with whole-genome sequencing to localise a ~3.2Mbp locus within the 1.2Gbp F. hepatica genome that confers TCBZ resistance. We validated this locus independently using bulk segregant analysis of F. hepatica populations and showed that it is the target of drug selection in the field. We genotyped individual parasites and tracked segregation and reassortment of SNPs to show that TCBZ resistance exhibits Mendelian inheritance and is conferred by a dominant allele. We defined gene content within this locus to pinpoint genes involved in membrane transport, (e.g. ATP-binding cassette family B, ABCB1), transmembrane signalling and signal transduction (e.g. GTP-Ras-adenylyl cyclase and EGF-like protein), DNA/RNA binding and transcriptional regulation (e.g. SANT/Myb-like DNA-binding domain protein) and drug storage and sequestration (e.g. fatty acid binding protein, FABP) as prime candidates for conferring TCBZ resistance. This study constitutes the first experimental cross and genome-wide approach for any heritable trait in F. hepatica and is key to understanding the evolution of drug resistance in Fasciola spp. to inform deployment of efficacious anthelmintic treatments in the field.

Milk tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), interferon (IFN-γ) and oxidative stress markers as new indicators for fascioliasis in dairy water buffaloes

Sixty Bubaline milk samples with corresponding blood samples were obtained from flocks at random in Cairo and Giza Governorates. The aerobic bacteria & somatic cells were counted and evaluated the physicochemical parameters of milk. Both milk and serum of buffaloes' were evaluated for tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interferon (IFN-ɤ) by quantitative real-time PCR protocol, and oxidative stress markers were measured spectrophotometrically. There was a significant difference (p < 0.05) between the mean values of whole milk physicochemical aspects except the moisture % & pH values were recorded for infested and non-infested animals. For F. gigantica infested animals, the milk TNF-α, IL-1β, interferon IFN-γ, malondialdehyde (MDA), and total antioxidant capacity (TAC) values were 17.5 ± 0.67, 18.5 ± 0.71, 19.25 ± 0.74, 7.75 ± 0.29, and 1.1 ± 0.04, respectively (lesser than serum values) with a significant difference (p < 0.05) between positive and negative samples for both examined serum and milk samples. There was also a significant (p < 0.05) negative relationship between MSCC & fat% and protein%, while a significant (p < 0.05) positive relationship between MSCC and the investigated milk cytokines in F. gigantica infested animals. This study is considered one of the fewest investigations of milk cytokines and oxidative stress markers in buffaloes fascioliasis diagnosis. Meanwhile, monitoring these genes modification that is active in the milk-producing gland is significant to typify the act technicality of the inherited immunity that helps the progress of schemes to retain the udder health.

Estimating the burden of multiple endemic diseases and health conditions using Bayes’ Theorem: A conditional probability model applied to UK dairy cattle

The Global Burden of Animal Diseases (GBADs) is an international collaboration aiming, in part, to measure and improve societal outcomes from livestock. One GBADs objective is to estimate the economic impact of endemic diseases in livestock. However, if individual disease impact estimates are linearly aggregated without consideration for associations among diseases, there is the potential to double count impacts, overestimating the total burden. Accordingly, the authors propose a method to adjust an array of individual disease impact estimates so that they may be aggregated without overlap. Using Bayes’ Theorem, conditional probabilities were derived from inter-disease odds ratios in the literature. These conditional probabilities were used to calculate the excess probability of disease among animals with associated conditions, or the probability of disease overlap given the odds of coinfection, which were then used to adjust disease impact estimates so that they may be aggregated. The aggregate impacts, or the yield, fertility, and mortality gaps due to disease, were then attributed and valued, generating disease-specific losses. The approach was illustrated using an example dairy cattle system with input values and supporting parameters from the UK, with 13 diseases and health conditions endemic to UK dairy cattle: cystic ovary, disease caused by gastrointestinal nematodes, displaced abomasum, dystocia, fasciolosis, lameness, mastitis, metritis, milk fever, neosporosis, paratuberculosis, retained placenta, and subclinical ketosis. The diseases and conditions modelled resulted in total adjusted losses of £ 404/cow/year, equivalent to herd-level losses of £ 60,000/year. Unadjusted aggregation methods suggested losses 14–61% greater. Although lameness was identified as the costliest condition (28% of total losses), variations in the prevalence of fasciolosis, neosporosis, and paratuberculosis (only a combined 22% of total losses) were nearly as impactful individually as variations in the prevalence of lameness. The results suggest that from a disease control policy perspective, the costliness of a disease may not always be the best indicator of the investment its control warrants; the costliness rankings varied across approaches and total losses were found to be surprisingly sensitive to variations in the prevalence of relatively uncostly diseases. This approach allows for disease impact estimates to be aggregated without double counting. It can be applied to any livestock system in any region with any set of endemic diseases, and can be updated as new prevalence, impact, and disease association data become available. This approach also provides researchers and policymakers an alternative tool to rank prevention priorities.

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Three approaches to impact aggregation for multiple endemic diseases explored.

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Flexible method proposed to avoid double counting impacts within a livestock system.

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Illustrated using 13 endemic diseases and health conditions in UK dairy cattle.

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Provides an alternative perspective on ranking disease prevention priorities.

Field evaluation of the enhanced MM3-COPRO ELISA test for the diagnosis of Fasciola hepatica infection in sheep

Fasciolosis is a severe zoonosis responsible for major economic losses in livestock. The enhanced MM3-COPRO test (eMM3-COPRO) and the commercial version BIO K 201 (Bio-X Diagnostics, Rochefort, Belgium) are widely used as immunodiagnostic tools for the specific detection of coproantigens released by Fasciola during the late prepatent and patent stages of infection. However, performance of the eMM3-COPRO has never been evaluated under field conditions. To address this gap, a large number of ovine faecal samples, collected in a region where fasciolosis is endemic (Galicia, NW Spain), were analyzed. Two groups of sheep flocks were selected according to the Fasciola infection status: ‘Fasciola-free’ and ‘Fasciola-infected’ flocks. ‘Fasciola-free’ flocks were seronegative flocks with no history of fasciolosis detected by either coproscopy or necropsy in the last 5 years. Faecal samples from these sheep were used to calculate a cut-off value for infection (OD = 0.021). The cut-off was calculated using a bootstrap resampling method that enables estimation of the sampling distribution of the statistical parameters without making assumptions about the underlying data distribution. ‘Fasciola-infected’ flocks were characterized by high seroprevalence, a history of fasciolosis and periodical treatment with flukicides. Samples from these flocks were used to estimate the diagnostic accuracy of the eMM3-COPRO relative to coproscopy, which although limited by poor sensitivity is the only reference test available for diagnosing fasciolosis in vivo. To overcome this limitation, all animals classified positive by eMM3-COPRO were treated with triclabendazole and then retested. The eMM3-COPRO displayed higher sensitivity than coproscopy, as it detected coproantigens in all samples with positive coproscopy and in 12% of samples with negative coproscopy. The test also proved highly specific as coproantigens disappeared after the treatment. The eMM3-COPRO was less time consuming than coproscopy, particularly when the procedure involved numerous samples, and showed promise as a tool for monitoring flukicide efficacy.

Occurrence and Distribution of Fasciolosis in a Cohort of Ovine Livestock Restricted to a Mountain Plateau in Central Portugal

Simple Summary

Fasciola hepatica is a parasite that affects ruminants. This study evaluated the occurrence of fasciolosis in ovine livestock from central Portugal during a 2-year period. Positive animals were found in most locations and in both years (19.6% and 18.5% seropositive in the first year and second year, respectively). Correct anthelmintic treatment could further reduce egg elimination and pasture contamination.

Abstract

Fasciola hepatica is a parasite that is widespread in Europe, having been reported in ruminants of several European countries and causing an important economic impact. This study ascertained the occurrence and distribution of fasciolosis in Portuguese ovine livestock by assessing F. hepatica IgG antibodies in a cohort of confined sheep from a high-altitude region of central Portugal in a 2-year period. Positive animals were found in most locations and in both years, with 18 of the 92 animals (19.6% [95% confidence interval CI: 12.03–19.15]) and 17 of the same 92 animals (18.5% [95% CI: 11.15–27.93]) showing to be seropositive in the first year and second year, respectively (p = 0.85). Pasture contamination by F. hepatica eggs could be reduced by thorough anthelmintic treatments.

Milk As a New Diagnostic Tool for Rapid Detection of Fascioliasis in Dairy Goats Using Excretory/Secretory Antigen

PURPOSE

Fascioliasis is a serious livestock illness of particular importance for dairy goats; the objectives of this study were to describe effects of F. gigantica on milk composition and to use this information to estimate economic damages linked with Fasciola spp. infections. Furthermore, the study sought to standardize the use of milk instead of serum for early diagnosis of fascioliasis in dairy goats.

METHODS

One-hundred samples of goat milk along with corresponding blood samples were obtained at random from flocks in Cairo and Giza Governorates. The ELISA and DOT-ELISA were performed in both serum and milk of dairy goats.

RESULTS

Total mesophilic count (mean value) was 2.12 × 10⁶ ± 1.63 × 10⁵ CFU/ml in enzyme-linked immunosorbent assay (ELISA) positive samples and 1.46 × 10⁴ ± 8.58 × 10² CFU/ml in ELISA-negative samples. The mean values were significantly different (P < 0.05). The mean values of percentages of fat, SNF, protein, salts, lactose, pH, and MSCC/ml in ELISA-positive samples were 2.3 ± 0.17, 8.21 ± 0.63, 3.08 ± 0.18, 0.90 ± 0.06, 3.64 ± 0.28, 6.93 + 0.53, and 1.18 × 10⁶ ± 9.07 × 10⁴ cells/ml, respectively. A significant difference (P < 0.05) between the mean values of two composition parameters, i.e., percent of fat and MSCC/ml in ELISA-positive and -negative samples, for Fasciola gigantica was observed. The antigen used for the diagnosis of F. gigantica was excretory/secretory (E/S) antigen. The dilutions of (E/S) concentrations after checkerboard titration for indirect ELISA were 20 μg/ml protein and for dot-ELISA, 300 ng/μl. Sera dilution was 1:100 in the two tests, and milk dilution was 1:50 for indirect ELISA, and 1:25 for dot-ELISA. The two tests were performed using known F. gigantica positive and negative goat sera and known rat hyper immunized negative and positive sera against E/S antigen of F. gigantica as well as known sera for paramphistomes without F. gigantica infection. The cutoff values in indirect ELISA were 0.45 for sera and 0.35 for milk.

CONCLUSION

The application of different serological technique in goat farms reveals a good test in rapid diagnosis of fascioliasis especially the uses of dot ELISA when using the milk instead of the serum.

Hepatic biomarkers and coprology as indicators of clinical bovine fasciolosis in Chad

Background and Aim:

Fasciolosis is a cosmopolitan parasitic disease of food-producing animals and is typically caused by digenetic trematodes, Fasciola gigantica and Fasciola hepatica. It has a direct negative impact on the liver and consequently affects liver metabolism. It has indirect effects, including lowered milk production and effects on quality and general health conditions leading to extensive economic losses. This study aimed to focus on the link between clinical fasciolosis and some biochemical analysis of the hepatic profile of cattle in Chad.

Materials and Methods:

This study was initiated in response to emerging complaints from dairy cattle owners detecting a bitter milk cream and butter taste. Furthermore, those animals had shown poor health conditions by presenting with diarrhea. Preliminary surveillance for possible causes was performed, including fecal and serum biochemical analyses and clinical observation to diagnose the possible disease.

Results:

The results obtained, including the finding of parasite stages during the coprological examination, confirmed the role of fasciolosis. The independent sample t-test indicated highly significantly altered values of all biochemical liver indicators in the infected animals. All animals were treated with two doses of rafoxanide (3 mg/kg b.w.) S/C, at 21 days intervals, with vitamin supplements, mineral mixtures, and food additives. Surprisingly, the main complaint was restored after treatment. This is another evident clue of fasciolosis. To the best of our knowledge, this is the first recent study that diagnosed fasciolosis in Chad.

Conclusion:

This study emphasized the importance of fasciolosis, its negative impact on milk taste, and the necessity for veterinary advice regarding routine examination and prophylactic measures, especially before autumn, to minimize economic losses. However, regardless of the small sample size, this study could serve as a cornerstone for future studies on evaluating the accurate epidemiological status of fasciolosis in Chad. This study reported a close association between the alteration of liver enzymes and total protein levels in fasciolosis and the bitter milk cream taste, which could be used as a diagnostic tool for fasciolosis.

The influence of liver fluke infection on production in sheep and cattle: a meta-analysis

Liver flukes (Fasciola spp.) are important parasites of ruminant livestock worldwide, causing profound damage to animal health and productivity. Many reviews have discussed the results of decades of research on the impact of fluke on livestock traits such as weight gain and milk production, but there have been no known attempts to collate previous research in a quantitative manner or to determine the factors that vary between studies that find substantial effects of fluke and others concluding that effects of fluke are negligible. Here, we use meta-analysis to provide quantitative "global" estimates of the impact of liver fluke on animal performance, and to identify elements of study design ("moderators") that influence variation between studies in their outcome. A literature search provided 233 comparisons of performance in fluke-infected and uninfected animals. We standardised these data as log response ratios and calculated effect size variances to weight studies by the accuracy of their estimates. We performed multi-level meta-analysis to estimate effects of fluke infection on daily weight gain, live weight, carcass weight, total weight gain and milk production. There were statistically-supported negative effects of fluke infection on daily weight gain, live weight and carcass weight (9%, 6% and 0.6% reductions, respectively), but not on total weight gain or milk production. A mixed-effects meta-analysis revealed that studies of younger animals found more severe effects of fluke on weight gain and that effects on live weight increased with time since infection. Limitations to the data that could be analysed, including a lack of statistical reporting in older papers and variation in the outcome variables measured, may have explained the relatively limited influence of modifiers that we detected. Our results provide, to our knowledge, the first quantitative estimate of the impact of liver fluke on performance across studies and highlight some elements of study design that can influence conclusions.

Evidence of population structuring following population genetic analyses of Fasciola hepatica from Argentina

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320 Argentinian Fasciola hepatica were genotyped using a panel of microsatellites.

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Overall there was high genotypic richness: 263 distinct genotypes were identified.

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Population structuring of F. hepatica was evident across Argentina.

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Within these sub-populations there is largely random mating.

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Transmission of clonemates occurs: clonal parasites accounted for 26.6% of all parasites.

Fasciola hepatica, the liver fluke, is a trematode parasite that causes disease of economic importance in livestock. As a zoonosis this parasite also poses a risk to human health in areas where it is endemic. Population genetic studies can reveal the mechanisms responsible for genetic structuring (non-panmixia) within parasite populations and provide valuable insights into population dynamics, which in turn enables theoretical predictions of evolutionary dynamics such as the evolution of drug resistance. Here we genotyped 320 F. hepatica collected from 14 definitive hosts from four provinces in Argentina. STRUCTURE analysis indicated three population clusters, and principal coordinate analysis confirmed this, showing population clustering across provinces. Similarly, pairwise F_ST values amongst all four provinces were significant, with standardised pairwise F_ST (F′_ST) ranging from 0.0754 to 0.6327. Therefore, population genetic structure was evident across these four provinces in Argentina. However, there was no evidence of deviation from Hardy–Weinberg equilibrium, so it appears that within these sub-populations there is largely random mating. We identified 263 unique genotypes, which gave a clonal diversity of 82%. Parasites with identical genotypes, clones, accounted for 26.6% of the parasites studied and were found in 12 of the 14 hosts studied, suggesting some clonemate transmission.

Association between milk yield and milk anti-Fasciola hepatica antibody levels, and the utility of bulk tank milk samples for assessing within-herd prevalence on organic dairy farms

Fasciola hepatica is an important disease of livestock that is responsible for substantial economic losses worldwide. Estimates of the impact of infection on milk yield vary, likely reflecting different geographical locations, farm-level management, and diagnostic methods. Measuring anti-Fasciola antibodies on bulk tank milk (BTM) by ELISA provides a convenient herd-level diagnosis, but the utility of this test remains unclear. Therefore, we evaluated the utility of BTM ELISA test results in Danish organic dairy farms, including estimating the association between 305 day energy corrected milk yield (305d ECM) and F. hepatica infection both at individual and herd level. BTM samples from 218 organic farms were analysed using IDEXX ELISA and subsequently the farmers were interviewed during spring 2016 with the aim of characterising their management practices. The corresponding farm-level production data covering the period 2014-2017 were collected from the Danish national cattle registry. In the following year, 284 individual milk samples (4-7 per herd) along with BTM samples were collected from a subset of the same herds (n = 55). Linear mixed models were used to estimate the association between milk production and ELISA value at both individual and farm levels, and a generalised additive model was used to assess the relationship between within-herd prevalence and BTM ELISA. A dichotomised BTM result with positive outcome was associated with a reduction of 580.5 kg in average 305d ECM, and a positive outcome on individual-level ELISA was associated with a 919.5 kg reduction in milk yield for cows in their third or later lactations. A strong relationship between quantitative BTM ELISA sample to positive percentage (S/P%) and apparent within-herd prevalence based on dichotomised individual-level milk ELISA was also observed, although this relationship was non-linear in nature. We conclude that a useful indication of the within-herd prevalence of infection can be obtained from BTM ELISA following categorisation as negative, low, medium or high according to S/P% cut-offs of approximately 30, 80, and 150. This approach represents a cheap and useful diagnostic tool for monitoring the long-term success of control strategies for F. hepatica infections on a dairy farm.

Current Challenges for Fasciolicide Treatment in Ruminant Livestock

Pharmacological treatment remains essential to control fasciolosis in areas where infection is endemic. However, there are major constraints to treating food-producing animals. Of particular concern is the lack of flukicides for treating early Fasciola infections in ruminant livestock in some countries. In addition, the information provided in package leaflets, particularly regarding withdrawal periods, is often incomplete, confusing, and/or contradictory. International regulatory bodies should harmonize the use of flukicides in livestock in favor of fairer, safer international trade. In addition, monitoring the efficacy of fasciolicides on farms is also essential to minimize the spread of drug-resistant populations of Fasciola. The current situation regarding flukicide formulations in the European Union and other, non-European countries is analyzed in this review paper.

Differences in the antibody response to adult Fasciola hepatica excretory/secretory products in experimentally and naturally infected cattle and sheep

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Antibody response is different in animals experimentally and naturally infected with F. hepatica.

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Experimentally infected animals specifically recognised cathepsin proteins.

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Naturally infected animals showed poor recognition of a recombinant cathepsin L1.

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Antibody response of naturally infected animals is against multiple antigens.

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Diagnostic tests based on a single antigen may not be suitable for use in field.

Fasciola hepatica (the liver fluke) is a common, global parasite of livestock. It can be highly pathogenic and has health and welfare implications for infected individuals. Typically, in ruminants, infections are sub-clinical, but if undiagnosed, they can lead to significant production losses. Accurate diagnosis is crucial to identify infection. Antibody detection ELISAs are commonly used to diagnose infection due to their high sensitivity and specificity and are typically based on native fluke excretory/secretory (ES) products or cathepsin L1 (CL1), the immunodominant antigen within ES products. These tests have been developed based on the antibody response of experimentally infected animals; however, this response has not been well characterised in naturally infected animals. We compared the antibody recognition of a recombinant CL1 (rCL1) antigen and native adult fluke ES products. Whilst samples from experimentally infected animals showed strong recognition of rCL1, serum antibodies from naturally infected animals did not. These results were confirmed by peptide array. Immunoblotting sera against ES products showed that experimentally infected animals had a strong, specific response to CL1/CL2 proteins whilst antibodies from naturally infected animals recognised multiple proteins and had a variable response to CL1/CL2. Mass spectrometry of proteins separated by 2D SDS PAGE, identified several antigens recognised by serum antibodies from a naturally infected cow, including cathepsins L1, L2 and L5, glutathione S-transferase and a dihydrolipoyl dehydrogenase. Overall, these results show that the antibody response in naturally infected animals to adult fluke ES products is qualitatively different to experimentally infected animals. This suggests that a diagnostic test based on CL1 alone may not be appropriate for diagnosis of natural F. hepatica infections in sheep and cattle.

Selective flukicide treatment of non-lactating cows and the corresponding production impact of Fasciola hepatica in dairy herds in Sweden

A control strategy against Fasciola hepatica infection based on selective treatment of non-lactating animals was evaluated in four Swedish dairy herds. The study was conducted over the course of two consecutive seasons in moderately to highly F. hepatica infected herds with robotic milking, where heifers and dry cows received an oral drench with albendazole (10 mg/kg) during three visits in January, February and March in both 2017 and 2018. This resulted in an anthelmintic coverage between 38 % and 58 % of the animals. Furthermore, on each visit, the infection status of all dewormed animals along with 15 randomly selected milking cows were monitored by detection of F. hepatica coproantigens. Individual milk samples were also collected quarterly from the whole herds for measurements of individual antibody levels against the parasite using milk ELISA. In addition, individual data on milk yield and quality were collected on a monthly basis between 2016 and 2018. To further study the impact of the infection on milk production, truly F. hepatica positive and negative cows in the first lactation were identified based on the results from coproantigen and milk ELISA assays. Total F. hepatica coproantigen prevalence in the herds varied between 28 % and 85 % in the first year, and between 27 % and 68 % in the second year of the study. We found that two years of treatments resulted in a significant decrease of coproantigen-positivity especially on the two most heavily infected farms. These results were confirmed by a similar drop in within-herd prevalences obtained by milk ELISA results. The infection had a significant negative impact on milk yields in untreated F. hepatica positive cows. No consistent long-term effect was observed at the herd level probably due to the influx of animals infected before puberty and/or adult animals that were re-infected at dry-off. This is the first study of the effects of F. hepatica infection on milk yield and quality in dairy herds in Sweden.

Serodiagnosis of Fasciola gigantica Infection in Buffaloes with Native Cathepsin-L Proteases and Recombinant Cathepsin L1-D

AIM

Serodiagnosis of Fasciola gigantica natural infection in buffaloes with recombinant cathepsin L1-D and native cathepsin-L protease antigens.

METHODS

The recombinant cat L1-D antigen was expressed in prokaryotic expression system and native cathepsin-L proteases were purified by alcoholic fractionation from adult F. gigantica flukes. Buffaloes (n  = 325) were screened for anti-Fasciola antibodies with the above antigens in immunoglobulin-G-enzyme linked immunosorbent assay (IgG-ELISA).

RESULTS

The recombinant cat L1-D antigen showed positive reactivity with 101/122 necropsy positive animals but 21/122 necropsy confirmed positive animals were negative in this ELISA (sensitivity 82.8%). However, 30/203 (14.8%) necropsy negative animals for Fasciola were seropositive with specificity of 85.2%. With native cat-L protease, 104/122 necropsy confirmed positive animals were ELISA positive but 18/122 necropsy positive animals were seronegative, thereby depicting the sensitivity of 85.2%. But ELISA with this antigen showed 27/203 (13.3%) necropsy negative animals as positive (specificity 86.7%).

CONCLUSIONS

Comparative evaluation of both the antigens showed that they are suitable for serodiagnosis of F. gigantica infection in buffalo herds.

The Epidemiology and Control of Liver Flukes in Cattle and Sheep

Fasciola hepatica, Fasciola gigantica, and Fascioloides magna are liver flukes causing disease in cattle and sheep. Damage to the liver due to F hepatica and F gigantica results in clinical disease and/or production losses. F magna seems to have little effect in cattle but causes high mortality in sheep. The fluke life cycle involves an aquatic or amphibious snail intermediate host and thus requires suitable moisture and temperature conditions. F magna requires the presence of deer. Drug treatment is the mainstay of control and needs to be applied considering the life cycle and epidemiology of the parasite.

Occurrence of fluke infection in beef cattle around Phayao Lake, Phayao, Thailand

Background and Aim:

Ruminant flukes, including Fasciola spp. and Paramphistomum spp., are recognized as the significant parasites in livestock worldwide. Cattle infected by these fluke results in slower growth rate and productivity losses contributing to economic losses. In case of Fasciola spp., the parasite is considered as an important zoonotic parasite. This study aimed to investigate the prevalence of fluke invasion in beef cattle around Phayao Lake, Phayao, Thailand, between January 2019 and June 2019.

Materials and Methods:

A total of 311 fecal samples from beef cows reared nearby Phayao Lake were examined for the presence of fluke eggs by formalin-ethyl acetate sedimentation and subsequently identified by morphology together with methylene blue staining.

Results:

The overall prevalence of fluke invasion in beef cattle around Phayao Lake was 33.8% (105/311). The prevalence of rumen fluke and liver fluke was 25.4% (79/311) and 8.4% (26/311), respectively. Mixed infection of both species was found at 1.9% (6/311).

Conclusion:

Age of cattle was observed to be associated with invasion rate of all flukes, particularly in the ages over 4 years, which was the highest group of invasion. However, other risk factors, including gender, breed, and location of animals, were not found to be related. This study provides the current status of natural fluke invasion among the beef cattle in Phayao, Thailand, which could be critical for designing the control program of these parasites.

Determination of the prevalence and intensity of Fasciola hepatica infection in dairy cattle from six irrigation regions of Victoria, South-eastern Australia, further identifying significant triclabendazole resistance on three properties

Fasciola hepatica (liver fluke) is a widespread parasite infection of livestock in Victoria, South-eastern Australia, where high rainfall and a mild climate is suitable for the main intermediate host Austropeplea tomentosa. The aims of this study were to quantify the prevalence and intensity of F. hepatica in dairy cattle in the irrigated dairy regions of Victoria and determine if triclabendazole resistance was present in infected herds. Cattle in 83 herds from the following six irrigation regions were tested for F. hepatica: Macalister Irrigation District (MID), Upper Murray (UM), Murray Valley (MV), Central Goulburn (CG), Torrumbarry (TIA) and Loddon Valley (LV). Twenty cattle from each herd were tested using the F. hepatica faecal egg count (FEC) as well as the coproantigen ELISA (cELISA). The mean individual animal true prevalence of F. hepatica across all regions was 39 % (95 % credible interval [CrI] 27%-51%) by FEC and 39 % (95 % CrI 27%-50%) by cELISA with the highest true prevalence (75-80 %) found in the MID. Our results show that 46 % of the herds that took part in this study were likely to experience fluke-associated production losses, based on observations that herd productivity is impaired when the true within-herd prevalence is > 25 %. Using the FEC and cELISA reduction tests, triclabendazole resistance was assessed on 3 herds in total (2 from the 83 in the study; and 1 separate herd that did not take part in the prevalence study) and resistance was confirmed in all 3 herds. This study has confirmed that F. hepatica is endemic in several dairy regions in Victoria: triclabendazole resistance may be contributing to the high prevalence in some herds. From our analysis, we estimate that the state-wide economic loss associated with fasciolosis is in the order of AUD 129 million (range AUD 38-193 million) per year or about AUD 50,000 (range AUD 15,000-75,000) per herd per year.

Fasciola hepatica seroprevalence in Northern German dairy herds and associations with milk production parameters and milk ketone bodies

Infections with the liver fluke Fasciola hepatica remain a serious problem in dairy herds causing significant production losses. In sheep, a strong relationship between F. hepatica infections and an increase in serum ketone bodies due to reduced feed intake and liver damage was demonstrated. We hypothesized that F. hepatica infections might contribute to an increase in milk ketone bodies in dairy herds. Thus, the objective of the study was to estimate the association between F. hepatica bulk tank milk (BTM) antibodies and milk production parameters (milk yield, milk protein, fat yield), somatic cell count (SCC) and the milk ketone bodies ß-hydroxybutyrate (BHB) and acetone, inferred from Fourier transform infrared (FTIR) spectrometry, via linear mixed model analysis. A further aim was to follow up the F. hepatica seroprevalence in dairy herds in the northern German region East Frisia. We collected BTM samples between October and December from 1022 herds in 2017 and 1318 herds in 2018. Overall, 33.1 % of the herds tested positive in 2017 and 37.0 % in 2018, showing decreased F. hepatica seroprevalences compared to prior seroprevalence studies in the same region in 2010, 2008 and 2006 (> 45 % positive herds). We estimated a significant negative association (P < 0.001) between herd F. hepatica infection category and average milk yield with a loss of -1.62 kg per cow per day in strongly infected herds compared to BTM ELISA negative herds. Moreover, F. hepatica infection category had a significant effect on herd average milk protein and fat yield (P < 0.001), showing a decrease of 0.06 kg for both parameters from BTM ELISA negative herds to strongly infected herds. No significant association with milk SCC was found (P = 0.664). Regarding ketone bodies, we estimated significant higher average BHB values in strongly infected herds compared to the other three infection categories in the model analysis (P = 0.002). The association between F. hepatica infection category and acetone values was not significant (P = 0.079). Besides primary ketosis, fasciolosis should be considered as differential diagnosis in dairy herds with increased BHB values.

Comparison of four commercially available ELISA kits for diagnosis of Fasciola hepatica in Irish cattle

Background

Fasciola hepatica is a liver parasite of mammals and it results in poor welfare outcomes and economic losses in ruminants. While faecal egg count is the test most commonly used for diagnosis, it does not indicate presence of migrating immature stages. Serological techniques increase sensitivity at all stages of the liver fluke infection. The aim of this study was to compare four commercially available ELISA tests for the diagnosis of F. hepatica. For this purpose, we tested three sample types; (i) known F. hepatica status sera from an experimental infection for the comparison of sensitivities and specificities, (ii) sera from pre- and post-flukicide-treated (albendazole, closantel, nitroxynil and triclabendazole) beef cattle to contrast the differences of seropositivity before and after treatment, and (iii) bulk tank milk samples from dairy herds sampled during high and low F. hepatica exposure periods for assessing seasonal variations with the four tests available. Samples were tested using ELISA kits supplied by four manufacturers (Ildana Biotech, IDEXX, Svanova, and Bio-X). Samples were analysed simultaneously and in duplicate.

Results

In the control population Ildana, IDEXX and Bio-X presented 100% sensitivity (Se) and specificity (Sp), Svanovir presented a Se of 59% and a Sp of 96%. In flukicide-treated beef cattle, kits highlighted decreasing antibody levels 90 days post-treatment in variable degrees. Finally, bulk milk showed a significant decrease in ELISA value between high and low fluke exposure periods with all tests studied.

Conclusions

Se and Sp found in the present study, confirm that Ildana, IDEXX and Bio-X are accurate for the detection of F. hepatica exposure in Irish cattle. Svanovir Se and Sp in this population, indicate that a larger study is necessary to confirm this test characteristic in Irish herds. In post-treatment use, Bio-X showed a consistent and significant decrease of ELISA value in all groups treated, denoting to be a reliable tool for assessing treatment effect at 90 days post-treatment. Finally, all tests showed to be a reliable tool for the F. hepatica monitoring of high and low exposure seasons, using bulk tank milk samples.

Allele substitution and dominance effects of CD166/ALCAM gene polymorphisms for endoparasite resistance and test-day traits in a small cattle population using logistic regression analyses

The study investigated the effects of four single-nucleotide polymorphisms (SNPs) in the activated leukocyte cell adhesion molecule (ALCAM) gene on liver fluke (Fasciola hepatica) infections (FH-INF), gastrointestinal nematode infections (GIN-INF) and disease indicator traits [e.g. somatic cell score (SCS), fat-to-protein ratio (FPR)] in German dual-purpose cattle (DSN). A genome-wide association study inferred the chip SNP ALCAMc.73+32791A>G as a candidate for F. hepatica resistance in DSN. Because of the crucial function of ALCAM in immune responses, SNPs in the gene might influence further resistance and performance traits. Causal mutations were identified in exon 9 (ALCAMc.1017T>C) and intron 9 (ALCAMc.1104+10T>A, ALCAMc.1104+85T>C) in a selective subset of 94 DSN cows. We applied logistic regression analyses for the association between SNP genotypes with residuals for endoparasite traits (rINF-FH, rGIN-INF) and estimated breeding values (EBVs) for test-day traits. The probability of the heterozygous genotype was estimated in dependency of the target trait. Allele substitution effects for rFH-INF were significant for all four loci. The T allele of the SNPs ALCAMc.1017T>C and ALCAMc.1104+85T>C was the favourable allele when improving resistance against FH-INF. Significant allele substitution for rGIN-INF was only found for the chip SNP ALCAMc.73+32791A>G. We identified significant associations between the SNPs with EBVs for milk fat%, protein% and FPR. Dominance effects for the EBVs of test-day traits ranged from 0.00 to 0.47 SD and were in the direction of improved resistance for rFH-INF. We estimated favourable dominance effects from same genotypes for rFH-INF and FPR, but dominance effects were antagonistic between rFH-INF and SCS.

High prevalence, potential economic impact, and risk factors of Fasciola hepatica in dairy herds in tropical, dry and temperate climate regions in Mexico

The aims of this study were to determine the prevalence of fasciolosis in cattle herds and its influence on production in order to identify potential risk factors in different climate regions and risk indices in three states of Mexico. The levels of anti-F. hepatica IgG1 antibodies were determined using an indirect ELISA. A total of 837 farm owners or managers answered the questionnaire. The total prevalence of the parasite over the period of January to March 2017 was 63.56%. The highest percentages of positive herds for the categories were found in Hidalgo state (88.33%), the no-risk classification (69.55%) and the temperate climate (76.53%). Overall, the production losses were approximately 0.51 to 1.00 kg of milk per parasitized cow per day. The annual costs of milk production loss per farm were estimated to range from US$2218.39 to US$6424.51, followed by anthelmintic treatment for young stock (US$67.68) and adult cows (US$209.47). Using multivariate logistic regression analysis, six final models were constructed for potential association with the ELISA results and were supported by the climatic, environmental and management factors. The results indicate that different factors were significantly associated with an increased risk of infection for each model.

Genome-wide association study of endo-parasite phenotypes using imputed whole-genome sequence data in dairy and beef cattle

BACKGROUND

Quantitative genetic studies suggest the existence of variation at the genome level that affects the ability of cattle to resist to parasitic diseases. The objective of the current study was to identify regions of the bovine genome that are associated with resistance to endo-parasites.

METHODS

Individual cattle records were available for Fasciola hepatica-damaged liver from 18 abattoirs. Deregressed estimated breeding values (EBV) for F. hepatica-damaged liver were generated for genotyped animals with a record for F. hepatica-damaged liver and for genotyped sires with a least one progeny record for F. hepatica-damaged liver; 3702 animals were available. In addition, individual cow records for antibody response to F. hepatica on 6388 genotyped dairy cows, antibody response to Ostertagia ostertagi on 8334 genotyped dairy cows and antibody response to Neospora caninum on 4597 genotyped dairy cows were adjusted for non-genetic effects. Genotypes were imputed to whole-sequence; after edits, 14,190,141 single nucleotide polymorphisms (SNPs) and 16,603,644 SNPs were available for cattle with deregressed EBV for F. hepatica-damaged liver and cows with an antibody response to a parasitic disease, respectively. Association analyses were undertaken using linear regression on one SNP at a time, in which a genomic relationship matrix accounted for the relationships between animals.

RESULTS

Genomic regions for F. hepatica-damaged liver were located on Bos taurus autosomes (BTA) 1, 8, 11, 16, 17 and 18; each region included at least one SNP with a p value lower than 10^-6. Five SNPs were identified as significant (q value < 0.05) for antibody response to N. caninum and were located on BTA21 or 25. For antibody response to F. hepatica and O. ostertagi, six and nine quantitative trait loci (QTL) regions that included at least one SNP with a p value lower than 10^-6 were identified, respectively. Gene set enrichment analysis revealed a significant association between functional annotations related to the olfactory system and QTL that were suggestively associated with endo-parasite phenotypes.

CONCLUSIONS

A number of novel genomic regions were suggestively associated with endo-parasite phenotypes across the bovine genome and two genomic regions on BTA21 and 25 were associated with antibody response to N. caninum.

Genome-wide associations and functional gene analyses for endoparasite resistance in an endangered population of native German Black Pied cattle

Background

Gastrointestinal nematodes (GIN), liver flukes (Fasciola hepatica) and bovine lungworms (Dictyocaulus viviparus) are the most important parasitic agents in pastured dairy cattle. Endoparasite infections are associated with reduced milk production and detrimental impacts on female fertility, contributing to economic losses in affected farms. In quantitative-genetic studies, the heritabilities for GIN and F. hepatica were moderate, encouraging studies on genomic scales. Genome-wide association studies (GWAS) based on dense single nucleotide polymorphism (SNP) marker panels allow exploration of the underlying genomic architecture of complex disease traits. The current GWAS combined the identification of potential candidate genes with pathway analyses to obtain deeper insights into bovine immune response and the mechanisms of resistance against endoparasite infections.

Results

A 2-step approach was applied to infer genome-wide associations in an endangered dual-purpose cattle subpopulation [Deutsches Schwarzbuntes Niederungsrind (DSN)] with a limited number of phenotypic records. First, endoparasite traits from a population of 1166 Black and White dairy cows [including Holstein Friesian (HF) and DSN] naturally infected with GIN, F. hepatica and D. viviparus were precorrected for fixed effects using linear mixed models. Afterwards, the precorrected phenotypes were the dependent traits (rFEC-GIN, rFEC-FH, and rFLC-DV) in GWAS based on 423,654 SNPs from 148 DSN cows. We identified 44 SNPs above the genome-wide significance threshold (p_Bonf = 4.47 × 10^− 7), and 145 associations surpassed the chromosome-wide significance threshold (range: 7.47 × 10^− 6 on BTA 1 to 2.18 × 10^− 5 on BTA 28). The associated SNPs identified were annotated to 23 candidate genes. The DAVID analysis inferred four pathways as being related to immune response mechanisms or involved in host-parasite interactions. SNP effect correlations considering specific chromosome segments indicate that breeding for resistance to GIN or F. hepatica as measured by fecal egg counts is genetically associated with a higher risk for udder infections.

Conclusions

We detected a large number of loci with small to moderate effects for endoparasite resistance. The potential candidate genes regulating resistance identified were pathogen-specific. Genetic antagonistic associations between disease resistance and productivity were specific for specific chromosome segments. The 2-step approach was a valid methodological approach to infer genetic mechanisms in an endangered breed with a limited number of phenotypic records.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5659-4) contains supplementary material, which is available to authorized users.

Patent infections with Fasciola hepatica and paramphistomes (Calicophoron daubneyi) in dairy cows and association of fasciolosis with individual milk production and fertility parameters

Infections with the liver fluke Fasciola hepatica may result in considerable economic losses in the dairy livestock industry worldwide. Infections have been associated with detrimental impacts on milk production and milk quality as well as reduced fertility. However, most related data rely on examinations on herd level and the rather few studies on individual cow level are based solely on antibodies as measure for F. hepatica infections. This entails the risk of including false-positives as anti-F. hepatica antibodies persist for months even if the infection is cleared. Therefore, the presented study aimed to overcome this issue by assessing the association between F. hepatica infections measured via faecal egg counts (FEC) and milk production as well as fertility parameters in individual dairy cows. In total, 2006 faecal samples from 1166 Black and White dairy cows from 17 small and medium-sized German grassland farms were examined in July and September 2015. The relationship between patent F. hepatica infections and the milk production parameters milk yield, milk protein content, milk fat content and somatic cell score (SCS) was assessed in a linear mixed model using test-day records of individual cows. Patent F. hepatica infections were found on 35.3% (7/17) of farms with an individual cow prevalence of 10.1% (97/963) in July and 9.1% (95/1036) in September. Patent rumen fluke infections were detected on 17.6% (3/17) farms with an individual cow prevalence of 0.4% (4/963) in July and 0.7% (9/1036) in September. No significant association was found between F. hepatica infection status and either SCS as an indicator of udder health or milk production parameters, despite 0.06 and 0.10% lower values for milk protein and fat content in patently infected cows. Linear mixed models and generalized linear mixed models were established to estimate the impact of fasciolosis on the fertility parameters calving to first service (CTFS), calving interval (CI), success in first insemination (SFI) and 56-day nonreturn rate (NRR56). A significantly higher average CTFS of 4.69 days was detected in F. hepatica infected cows (P = 0.025), but no significant relationship was found for the other fertility parameters.

In-plate recapturing of a dual-tagged recombinant Fasciola antigen (FhLAP) by a monoclonal antibody (US9) prevents non-specific binding in ELISA

Recombinant proteins expressed in E. coli are frequently purified by immobilized metal affinity chromatography (IMAC). By means of this technique, tagged proteins containing a polyhistidine sequence can be obtained up to 95% pure in a single step, but some host proteins also bind with great affinity to metal ions and contaminate the sample. A way to overcome this problem is to include a second tag that is recognized by a preexistent monoclonal antibody (mAb) in the gene encoding the target protein, allowing further purification. With this strategy, the recombinant protein can be directly used as target in capture ELISA using plates sensitized with the corresponding mAb. As a proof of concept, in this study we engineered a Trichinella-derived tag (MTFSVPIS, recognized by mAb US9) into a His-tagged recombinant Fasciola antigen (rFhLAP) to make a new chimeric recombinant protein (rUS9-FhLAP), and tested its specificity in capture and indirect ELISAs with sera from sheep and cattle. FhLAP was selected since it was previously reported to be immunogenic in ruminants and is expressed in soluble form in E. coli, which anticipates a higher contamination by host proteins than proteins expressed in inclusion bodies. Our results showed that a large number of sera from non-infected ruminants (mainly cattle) reacted in indirect ELISA with rUS9-FhLAP after single-step purification by IMAC, but that this reactivity disappeared testing the same antigen in capture ELISA with mAb US9. These results demonstrate that the 6XHis and US9 tags can be combined when double purification of recombinant proteins is required.

Little genetic variability in resilience among cattle exists for a range of performance traits across herds in Ireland differing in Fasciola hepatica prevalence

It is anticipated that in the future, livestock will be exposed to a greater risk of infection from parasitic diseases. Therefore, future breeding strategies for livestock, which are generally long-term strategies for change, should target animals adaptable to environments with a high parasitic load. Covariance components were estimated in the present study for a selection of dairy and beef performance traits over herd-years differing in Fasciola hepatica load using random regression sire models. Herd-year prevalence of F. hepatica was determined by using F. hepatica-damaged liver phenotypes which were recorded in abattoirs nationally. The data analyzed consisted up to 83,821 lactation records from dairy cows for a range of milk production and fertility traits, as well as 105,054 young animals with carcass-related information obtained at slaughter. Reaction norms for individual sires were derived from the random regression coefficients. The heritability and additive genetic standard deviations for all traits analyzed remained relatively constant as herd-year F. hepatica prevalence gradient increased up to a prevalence level of 0.7; although there was a large increase in heritability and additive genetic standard deviation for milk and fertility traits in the observed F. hepatica prevalence levels >0.7, only 5% of the data existed in herd-year prevalence levels >0.7. Very little rescaling, therefore, exists across differing herd-year F. hepatica prevalence levels. Within-trait genetic correlations among the performance traits across different herd-year F. hepatica prevalence levels were less than unity for all traits. Nevertheless, within-trait genetic correlations for milk production and carcass traits were all >0.8 for F. hepatica prevalence levels between 0.2 and 0.8. The lowest estimate of within-trait genetic correlations for the different fertility traits ranged from -0.03 (SE = 1.09) in age of first calving to 0.54 (SE = 0.22) for calving to first service interval. Therefore, there was reranking of sires for fertility traits across different F. hepatica prevalence levels. In conclusion, there was little or no genetic variability in sensitivity to F. hepatica prevalence levels among cattle for milk production and carcass traits. But, some genetic variability in sensitivity among dairy cows did exist for fertility traits measured across herds differing in F. hepatica prevalence.

Risk factors for the presence of Fasciola hepatica antibodies in bulk-milk samples and their association with milk production decreases, in Cuban dairy cattle

Background

Worldwide, Fasciola hepatica infection causes high production losses in the livestock industry. Recently, studies have analyzed the association between measurements of F. hepatica infection intensity and herd management practices. The aim of the present study, the first of its kind in a subtropical region, was to evaluate associations between F. hepatica bulk-tank milk ELISA results with herd management factors and milk yield in dairy herds, in Camagüey, Cuba. The SVANOVIR® F. hepatica-AB ELISA was used to measure F. hepatica antibody levels in a random sample of 516 dairy herds during the period of May–July of 2014. Farm management practice data were collected using a questionnaire.

Results

With 82% of the herds testing positive, the results indicate that F. hepatica is very widespread in this area. Reductions in milk production of 18 and 32% were observed in herds with Optical Density Ratios (ODR) of 0.3–0.6 and > 0.6, respectively, when compared to herds with ODR <  0.3. Overall, the longer the milking cows were put out to pasture, the higher the levels of anti-parasite antibodies. Co-grazing with sheep and goats also significantly increased the risk of high ODR.

Conclusions

Our data show a widespread occurrence of the parasite as well as a major potential impact of the infection on the Cuban development goal of becoming self-sufficient in milk production. Our risk factor analysis suggests that the prevention of infection around water sources, and the separation of cattle from small ruminants could be useful control measures. This is the first epidemiological survey of F. hepatica abundance, and associated reductions in milk yield, in dairy herds in Cuba.

Development and validation of a protocol to identify and recruit participants into a large scale study on liver fluke in cattle

Background

Liver fluke infection caused by the parasite Fasciola hepatica is a major cause of production losses to the cattle industry in the UK. To investigate farm-level risk factors for fluke infection, a randomised method to recruit an appropriate number of herds from a defined geographical area into the study was required. The approach and hurdles that were encountered in designing and implementing this study are described. The county of Shropshire, England, was selected for the study because of the variation between farms in exposure to fluke infection observed in an earlier study.

Results

From a sampling list of 569 holdings in Shropshire randomly drawn from the RADAR cattle population dataset, 396 (69.6%) holdings were successfully contacted by telephone and asked if they would be interested in taking part in the study. Of 296 farmers who agreed to receive information packs by post, 195 (65.9%) agreed to take part in the study. Over the period October 2014 – April 2015 visits were made to 100 dairy and 95 non-dairy herds. During the farm visits 40 faecal samples +/− bulk-tank milk samples were collected and a questionnaire administered. Composite faecal samples were analysed for the presence of F. hepatica eggs by sedimentation and bulk tank milk samples were tested with an antibody ELISA for F. hepatica. Forty-five (49%) of non-dairy herds were positive for liver fluke infection as determined by the finding of one or more fluke eggs, while 36 (36%) dairy herds had fluke positive faecal samples and 41 (41%) dairy herds were positive for F. hepatica antibody. Eighty-seven (45.8%) farmers said that they monitored their cattle for liver fluke infection and 118 (62.1%) reported that they used flukicide drugs in their cattle.

Conclusions

Using a protocol of contacting farmers directly by telephone and subsequently sending information by post, 79% of the target sample size was successfully recruited into the study. A dataset of farm-specific information on possible risk factors for liver fluke infection and corresponding liver-fluke infection status was generated for the development of statistical models to identify risk factors for liver fluke infection at the farm-level.

Seasonal variation of Fasciola hepatica antibodies in dairy herds in Northern Ireland measured by bulk tank milk ELISA

Bovine fasciolosis, caused by the infection of the trematode parasite Fasciola hepatica, remains a problem in dairy herds causing significant production losses. In this study, bulk milk tank samples were utilised to generate a comprehensive survey of the variation in liver fluke exposure over the four seasons of 2016 in Northern Ireland (NI). Samples were tested using an antibody ELISA test; within-herd prevalence levels were categorised relative to sample-to-positive ratio (S/P%). Overall, 1494 herds (~ 50% of all active dairy farms in NI) were sampled. In total, 5750 samples were tested with 91% of herds having a sample result for each season. The proportion of herds with evidence of liver fluke exposure was very high across the year, with 93.03% of all bulk milk samples having some indication of liver fluke antibody presence. A high proportion of samples (2187/5750; 38.03%) fell within the highest infection class (indicating high within-herd prevalence). There was significant seasonal variation in the mean S/P%. A multivariable random effect ordinal logit model suggested that the greatest probability of being in a higher infection class was in winter, whilst the lowest was recorded during summer. There was a significant negative association between increasing herd liver fluke infection class and herd size. Furthermore, there was significant variation in infection levels across regions of Northern Ireland, with higher infection levels in northern administrative areas. This study demonstrates the very high liver fluke exposure in this region of Europe, and that risk is not equally distributed spatially or across seasons in dairy herds.

Herd-level seroprevalence of Fasciola hepatica and Ostertagia ostertagi infection in dairy cattle population in the central and northeastern Poland

Background

Fasciola hepatica and Ostertagia ostertagi infections are widespread in cattle population of Europe, however data on their prevalence in Poland are only fragmentary. Therefore, the cross-sectional study was carried out to determine the herd-level seroprevalence of F. hepatica and O. ostertagi infection in dairy cattle population in the central and north-eastern provinces Poland, and to identify basic local risk factors for these infections. In total, 598 herds were enrolled, 394 (65.9%) in the north-eastern province and 204 (34.1%) in the central province. In each herd the questionnaire survey was conducted and bulk-tank milk (BTM) sample was collected and screened using two indirect immunoenzymatic tests. Optical density ratio (ODR) was regarded as the quantitative proxy of exposure to either of the two parasites.

Results

Both Fasciola and Ostertagia ELISA ODR in the north-eastern province was significantly higher than ODR in the central province. At the cut-off value of ODR = 0.27 the true herd-level seroprevalence of F. hepatica was 79.6% (95% CI: 74.0%, 84.3%) in the north-eastern province and 13.0% (95% CI: 5.3%, 21.7%) in the central province. At the cut-off of ODR = 0.50151 of 188 herds (80.3%, 95% CI: 74.1%, 85.4%) were seropositive for O. ostertagi in the north-eastern province and only 70 of 136 herds (51.5%, 95% CI: 43.1%, 59.7%) were seropositive in the central province. Location of a herd in the north-eastern province, longer grazing period practiced in a herd and > 50%-share of grazing grass in roughage were all positively related to the increase in exposure to both parasites. Moreover, the use of hay or haylage as main roughage proved to be positively related to the increase in exposure to F. hepatica.

Conclusions

F. hepatica and O. ostertagi are widespread in cattle population in Poland, however their occurrence at a herd-level varies between different regions of Poland. This diversity can only partly be explained by different herd management, and appears linked to environmental and climate conditions typical for these regions.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1455-7) contains supplementary material, which is available to authorized users.

Comparison of recombinant cathepsins L1, L2, and L5 as ELISA targets for serodiagnosis of bovine and ovine fascioliasis

Infections caused by Fasciola hepatica are of great importance in the veterinary field, as they cause important economic losses to livestock producers. Serodiagnostic methods, typically ELISA (with either native or recombinant antigens), are often used for early diagnosis. The use of native antigens, as in the MM3-SERO ELISA (commercialized as BIO K 211, BIO-X Diagnostics), continues to be beneficial in terms of sensitivity and specificity; however, there is interest in developing ELISA tests based on recombinant antigens to avoid the need to culture parasites. Of the antigens secreted by adult flukes, recombinant procathepsin L1 (rFhpCL1) is the most commonly tested in ELISA to date. However, although adult flukes produce three different clades of CLs (FhCL1, FhCL2, and FhCL5), to our knowledge, the diagnostic value of recombinant FhCL2 and FhCL5 has not yet been investigated. In the present study, we developed and tested three indirect ELISAs using rFhpCL1, rFhpCL2, and rFhpCL5 and evaluated their recognition by sera from sheep and cattle naturally infected with F. hepatica. Although the overall antibody response to these three rFhpCLs was similar, some animals displayed preferential recognition for particular rFhpCLs. Moreover, for cattle sera, the highest sensitivity was obtained using rFhpCL2 (97%), being equal for both rFhpCL1 and rFhpCL5 (87.9%), after adjusting cut-offs for maximum specificity. By contrast, for sheep sera, the sensitivity was 100% for the three rFhpCLs. Finally, the presence of truncated and/or partially unfolded molecules in antigen preparations is postulated as a possible source of cross-reactivity.

Genetic correlations between endo-parasite phenotypes and economically important traits in dairy and beef cattle

Parasitic diseases have economic consequences in cattle production systems. Although breeding for parasite resistance can complement current control practices to reduce the prevalence globally, there is little knowledge of the implications of such a strategy on other performance traits. Records on individual animal antibody responses to Fasciola hepatica, Ostertagia ostertagi, and Neospora caninum were available from cows in 68 dairy herds (study herds); national abattoir data on F. hepatica-damaged livers were also available from dairy and beef cattle. After data edits, 9,271 dairy cows remained in the study herd dataset, whereas 19,542 dairy cows and 68,048 young dairy and beef animals had a record for the presence or absence of F. hepatica-damaged liver in the national dataset. Milk, reproductive, and carcass phenotypes were also available for a proportion of these animals as well as their contemporaries. Linear mixed models were used to estimate variance components of antibody responses to the three parasites; covariance components were estimated between the parasite phenotypes and economically important traits. Heritability of antibody responses to the different parasites, when treated as a continuous trait, ranged from 0.07 (O. ostertagi) to 0.13 (F. hepatica), whereas the coefficient of genetic variation ranged from 4% (O. ostertagi) to 20% (F. hepatica). The antibody response to N. caninum was genetically correlated with the antibody response to both F. hepatica (-0.29) and O. ostertagi (-0.67); a moderately positive genetic correlation existed between the antibody response to F. hepatica and O. ostertagi (0.66). Genetic correlations between the parasite phenotypes and the milk production traits were all close to zero (-0.14 to 0.10), as were the genetic correlations between F. hepatica-damaged livers and the carcass traits of carcass weight, conformation, and fat score evaluated in cows and young animals (0.00 to 0.16). The genetic correlation between F. hepatica-damaged livers in cows and milk somatic cell score was 0.32 (SE = 0.20). Antibody responses to F. hepatica and O. ostertagi had favorable genetic correlations with fertility traits, but conversely, antibody response to N. caninum and F. hepatica-damaged livers were unfavorably genetically correlated with fertility. This study provides the necessary information to undertake national multitrait genetic evaluations for parasite phenotypes.

Accuracy of a diagnostic model based on serum biochemical parameters in detecting cows at an increased risk of chronic fascioliasis

In adult cattle Fasciola hepatica infection usually follows a chronic subclinical course, and reduces both the milk yield and milk quality, resulting in considerable financial losses. Effective control of the disease is based on reliable identification of asymptomatically infected individuals, which now requires special parasitological or serological diagnostic tests. It is also known that F. hepatica infection induces alterations in some serum biochemical parameters. Therefore, the study was conducted to develop a model based on serum biochemical parameters allowing to identify cows at higher risk of chronic fascioliasis. Six hundred sixty eight adult dairy cows from 97 herds located in central and northeastern Poland were clinically examined, and blood and fecal samples from them were collected for a routine monitoring of fascioliasis and metabolic profile. Using the combination of fecal sedimentation test and indirect ELISA based on excretory/secretory products 203 cows, apparently healthy in clinical examination, were definitively classed as affected by (47 cows, 23.2%) or free from (156 cows, 76.8%) chronic fascioliasis. Their serum was screened for the activity of 4 enzymes (γ-glutamyl transpeptidase, glutamate dehydrogenase, aspartate aminotransferase, creatine kinase) and concentration of 18 other components (total bilirubin, total protein, albumin, globulin, urea, glucose, non-esterified fatty acids, β-hydroxybutyrate, sodium, potassium, chloride, calcium, magnesium, copper, zinc, iron, selenium, and haptoglobin). Logistic regression analysis was used to build 4 multivariable models allowing for identification of cows at risk of chronic fascioliasis. Then, the accuracy was compared between the models using the area under the receiver operating characteristic curve (AUROC), and an optimal cut-off value was determined for the most accurate model using Youden J index. The most accurate proved to be the model based on glutamate dehydrogenase activity and globulin, urea (all three positively linked with risk of chronic fascioliasis), and selenium concentration (negatively linked) adjusted by the access to pasture and cow's age. At the optimal cut-off of 0.37 this model had sensitivity of 85.1% (CI 95%:72.3%, 92.6%), specificity of 90.4% (CI 95%:84.7%, 94.1%), positive likelihood ratio of 8.8 (CI 95%:5.4, 14.5), and negative likelihood ratio of 0.16 (CI 95%:0.08, 0.33). This model performed significantly better than model including only γ-glutamyl transpeptidase or model including both γ-glutamyl transpeptidase and aspartate aminotransferase (both also adjusted by the access to pasture and cow's age), and was the only model which performed significantly better than the basic model based solely on the access to pasture and cow's age.

Fasciola spp: Mapping of the MF6 epitope and antigenic analysis of the MF6p/HDM family of heme-binding proteins

MF6p/FhHDM-1 is a small cationic heme-binding protein which is recognized by the monoclonal antibody (mAb) MF6, and abundantly present in parenchymal cells and secreted antigens of Fasciola hepatica. Orthologs of this protein (MF6p/HDMs) also exist in other causal agents of important foodborne trematodiasis, such as Clonorchis sinensis, Opisthorchis viverrini and Paragonimus westermani. Considering that MF6p/FhHDM-1 is relevant for heme homeostasis in Fasciola and was reported to have immunomodulatory properties, this protein is expected to be a useful target for vaccination. Thus, in this study we mapped the epitope recognized by mAb MF6 and evaluated its antigenicity in sheep. The sequence of the MF6p/FhHDM-1 ortholog from F. gigantica (MF6p/FgHDM-1) was also reported. By means of ELISA inhibitions with overlapping synthetic peptides, we determined that the epitope recognized by mAb MF6 is located within the C-terminal moiety of MF6p/FhHDM-1, which is the most conserved region of MF6p/HDMs. By immunoblotting analysis of parasite extracts and ELISA inhibitions with synthetic peptides we also determined that mAb MF6 reacted with the same intensity with F. hepatica and F. gigantica, and in decreasing order of intensity with C. sinensis, O.viverrini and P. westermani orthologs. On the contrary, mAb MF6 showed no reactivity against Dicrocoelium dendriticum and Schistosoma mansoni. The study of the recognition of peptides covering different regions of MF6p/FhHDM-1 by sera from immunized sheep revealed that the C-terminal moiety is the most antigenic, thus being of potential interest for vaccination. We also demonstrated that the production of antibodies to MF6p/FhHDM-1 in sheep infected by F. hepatica occurs relatively early and follows the same pattern as those produced against L-cathepsins.

Farm-level risk factors for Fasciola hepatica infection in Danish dairy cattle as evaluated by two diagnostic methods

Background

The prevalence of bovine fasciolosis in Denmark is increasing but appropriate guidelines for control are currently lacking. In order to help develop a control strategy for liver fluke, a risk factor study of farm management factors was conducted and the utility of bulk tank milk (BTM ELISA) as a tool for diagnosis in Danish dairy cattle farms was assessed.

Methods

This case-control study aimed to identify farm-level risk factors for fasciolosis in Danish dairy farms (> 50 animals slaughtered in 2013) using two diagnostic methods: recordings of liver condemnation at slaughter, and farm-level Fasciola hepatica antibody levels in BTM. A case farm was defined as having a minimum of 3 incidents of liver condemnation due to liver fluke at slaughter (in any age group) during 2013, and control farms were located within 10 km of at least one case farm and had no history of liver condemnation due to liver fluke during 2011–2013. The selected farmers were interviewed over telephone about grazing and control practices, and BTM from these farms was collected and analysed by ELISA in 2014. The final complete dataset consisting of 131 case and 63 control farms was analysed using logistic regression.

Results

Heifers grazing on wet pastures, dry cows grazing on wet pastures, herd size, breed and concurrent beef cattle production were identified as risk factors associated with being classified as a case farm. With the categorised BTM ELISA result as the response variable, heifers grazing on wet pastures, dry cows grazing on wet pastures, and purchase of cows were identified as risk factors. Within the case and control groups, 74.8 and 12.7% of farms were positive for fasciolosis on BTM ELISA, respectively. The differences are likely to be related to the detection limit of the farm-level prevalence by the BTM ELISA test, time span between slaughter data and BTM, and the relatively low sensitivity of liver inspection at slaughter.

Conclusions

Control of bovine fasciolosis in Denmark should target heifers and dry cows through grazing management and appropriate anthelmintic treatment, and BTM ELISA can be a useful diagnostic tool for fasciolosis in Danish dairy farms.

Electronic supplementary material

The online version of this article (10.1186/s13071-017-2504-y) contains supplementary material, which is available to authorized users.

Patent gastrointestinal nematode infections in organically and conventionally pastured dairy cows and their impact on individual milk and fertility parameters

Infections with gastrointestinal nematodes (GIN) can lead to production losses and impacts on product quality in affected cows, which has mainly been demonstrated during deworming experiments or via herd-level measurements. Here, a field study was carried out to explore the association between GIN infection status and milk production as well as fertility parameters in individual dairy cows. Different selection lines of Black and White cows were included in the study, which were distributed among 17 small and medium-sized organic and conventional German grassland farms. Faecal samples of 1166 dairy cows were examined twice, in July and September 2015. Nematode eggs were found in the faeces of 473 (40.6%) cows. As expected, strongylid eggs (Trichostrongylidae or Oesophagostomum and Bunostomum spp., respectively) were the predominant morphotype, followed by Strongyloides papillosus and Capillaria spp. eggs. In July, cows kept under organic conditions had a significantly lower GIN prevalence in comparison to cows kept on conventional farms. Faecal egg counts were generally low, with the highest value in September and an arithmetic mean of 11.3 eggs per gram faeces (EPG) for all observations. The relationships between GIN infection status and milk yield (kg milk/cow/day), milk protein content (%) and milk fat content (%) for each first test-day record after parasitological assessment were estimated by using linear mixed models. Milk protein content was estimated 0.05% lower in GIN positive compared to GIN negative cows, whereas no significant effect on milk yield or milk fat content was observed. The impact of GIN infection status on success in first insemination (SFI) was estimated by using a threshold model. No significant association was demonstrated between GIN infection status and SFI. Unexpectedly, the fertility parameter days from calving-to-first-service (CTFS) showed a significantly shorter average interval in GIN positive cows. However, these data on reproductive performance need to be considered preliminary as long-term studies are needed to allow a firm prediction of the impact of GIN infection status on dairy cow fertility parameters.

Helminth infections on organic dairy farms in Spain

The aim of this study was to assess the prevalence of the major helminth infections affecting organic dairy cattle in northern Spain. Milk and faecal samples were obtained from 443 milking cows. Ostertagia ostertargi and Fasciola hepatica exposure was assessed by detection of specific antibodies in milk samples and F. hepatica infection was diagnosed by the detection of coproantigens in faecal samples. Dictyocaulus viviparus and Calicophoron daubneyi infections were diagnosed by conventional coprological techniques. The prevalence of infections caused by F. hepatica was considerable low, but similar to data reported from conventional farming in the same area. The prevalence rate of C. daubneyi infection was higher than previous data mirroring an increase of the prevalence that was also reported in other European countries in recent years. Specific antibodies against O. ostertargi were detected in all herds and the median levels of antibodies, determined by ELISA, exceeded the thresholds indicating milk production losses. The prevalence of D. viviparus was almost negligible. For each parasite, an ordinal logistic-regression analysis was used to assess the risk of infection by taking into account the administration of effective anthelmintics and the number of lactations. Treatment of cows with fasciolicides decreased the risk of F. hepatica infection in multiparous cows, whereas treatment with oxiclozanide or albendazol did not decrease the risk of C. daubneyi infection or O. ostertargi exposure, respectively. The study findings demonstrate that helminth infection in organic dairy farming is similar or even lower than previous data reported from conventional farming. Special attention should be paid to the impact of these infections on milk production.

Associations between fasciolosis and milk production, and the impact of anthelmintic treatment in dairy herds

Liver fluke is a ubiquitous parasite that causes extensive production losses in cattle and is a zoonosis. The aims of this study were to determine the prevalence of fasciolosis in 178 dairy cattle herds in Styria (federal state of Austria) and its influence on production, to detect the risk factors for infection, and to explore effective strategies in management and control. A questionnaire on farm management, prophylaxis, and therapy was developed and applied. Furthermore, production parameters (milk yield, milk protein content, butter fat content, non-return rate 90, calving to conception interval, service period) were recorded for 2014 and 2015, and a commercial ELISA for detection of Fasciola hepatica antibodies was applied in bulk tank milk in March 2014 and March 2015. Analysis of bulk tank milk samples showed a prevalence of 61.3% in 2014 and 45.5% in 2015. No associations could be found between F. hepatica exposure and farm structure or pasture management. Farms with highly positive (optical density ratio (ODR) ≥ 0.6 and lying above the upper interquartile range) antibody levels had a significantly lower annual milk yield of 438 kg per cow per year (p = 0.045), butterfat content of 0.091% (p = 0.004), and milk protein content of 0.046% (p = 0.024). However, fertility parameters were not significantly associated with liver fluke exposure. Anthelmintic treatment led to significantly lower antibody levels in the subsequent year (p = 0.042) and had a significant influence on protein content in milk (p = 0.003). This study highlighted the importance of fasciolosis in Austria and its influence on milk production and the need for veterinary advice regarding prophylactic measures to reduce economic losses.

Combining Slaughterhouse Surveillance Data with Cattle Tracing Scheme and Environmental Data to Quantify Environmental Risk Factors for Liver Fluke in Cattle

Liver fluke infection causes serious disease (fasciolosis) in cattle and sheep in many regions of the world, resulting in production losses and additional economic consequences due to condemnation of the liver at slaughter. Liver fluke depends on mud snails as an intermediate host and infect livestock when ingested through grazing. Therefore, environmental factors play important roles in infection risk and climate change is likely to modify this. Here, we demonstrate how slaughterhouse data can be integrated with other data, including animal movement and climate variables to identify environmental risk factors for liver fluke in cattle in Scotland. We fitted a generalized linear mixed model to the data, with exposure-weighted random and fixed effects, an approach which takes into account the amount of time cattle spent at different locations, exposed to different levels of risk. This enabled us to identify an increased risk of liver fluke with increased animal age, rainfall, and temperature and for farms located further to the West, in excess of the risk associated with a warmer, wetter climate. This model explained 45% of the variability in liver fluke between farms, suggesting that the unexplained 55% was due to factors not included in the model, such as differences in on-farm management and presence of wet habitats. This approach demonstrates the value of statistically integrating routinely recorded slaughterhouse data with other pre-existing data, creating a powerful approach to quantify disease risks in production animals. Furthermore, this approach can be used to better quantify the impact of projected climate change on liver fluke risk for future studies.

Decision making on helminths in cattle: diagnostics, economics and human behaviour

Helminth infections of cattle affect productivity in all classes of stock, and are amongst the most important production-limiting diseases of grazing ruminants. Over the last decade, there has been a shift in focus in the diagnosis of these infections from merely detecting presence/absence of infection towards detecting its impact on production. This has been facilitated by studies observing consistent negative correlations between helminth diagnostic test results and measures of productivity. Veterinarians are increasingly challenged to consider the economic aspects of their work, and the use of these tests should now be integrated in economic evaluation frameworks for improved decision making. In this paper, we review recent insights in the farm-specific economic impact of helminth infections on dairy cattle farms as well as in farmer attitudes and behaviour regarding helminth control. Combining better economic impact assessments of helminth infections together with a deeper understanding of the non-economic factors that drive a farmer’s animal health decisions should result in more effective control strategies and increased farmer satisfaction.

Rapid Enhanced MM3-COPRO ELISA for Detection of Fasciola Coproantigens

ELISA-based methods of detecting Fasciola cathepsins in feces are powerful techniques for diagnosing infections by F. hepatica and F. gigantica. In the last decade, the in-house MM3-COPRO ELISA and its commercial version BIO K 201 (BIO X Diagnostics, Belgium) have been recognized as useful tools for detecting early infections by such trematodes and for monitoring the efficacy of anthelmintic treatments in human and animal species, as they provide some advantages over classic fecal egg counts. However, the sensitivity of MM3-COPRO ELISA can sometimes be compromised by the high variability in the concentration of cathepsins in fecal samples throughout the biological cycle of Fasciola (mainly in cattle) and by differences in the between-batch performance of peroxidase-labeled anti-mouse IgG polyclonal antibodies. To prevent such problems, we investigated whether the incorporation of a commercial streptavidin-polymerized horseradish peroxidase conjugate, in order to reveal bound biotinylated monoclonal antibody MM3, can improve the sensitivity of the MM3-COPRO ELISA. We observed that inclusion of this reagent shifted the previous detection limit of the assay from 0.6 ng/mL to 150 pg/mL and that the modified test is able to identify infection in cows harboring only one fluke. Moreover, we demonstrated that maximal OD values can be achieved with short incubations (30 min each step) at RT with shaking, rather than standard incubations, which significantly accelerates the diagnostic procedure. Finally, we did not find a significant correlation between coproantigen concentration and parasite burden in cattle, which may be due to the low parasite burden (1–10 adult flukes) of the animals used in the present study. As the usefulness of the classic MM3-COPRO test for detecting animal and human infections has already been demonstrated, it is expected that the improvements reported in this study will add new insights into the diagnosis and control of fasciolosis.

We have previously reported how the combined use of mAb MM3 with polyclonal antibodies obtained from rabbit immunized with Fasciola hepatica excretory-secretory antigens led to the development of the in-house MM3-COPRO ELISA and its commercial version BIO K 201 (BIO X Diagnostics, Belgium), which are widely used to detect human and animal infections caused by F. hepatica. After more than a decade in use, both tests have proven to be useful tools for specifically detecting Fasciola infections, although it has also been found that: i) the conditions of use of the commercial test in some field studies did not enable the sensitivity obtained with the in-house test to be reached, and ii) the batches of the secondary reagent (peroxidase-labeled anti-mouse antibodies) currently available for use in the in-house test do not perform the same as previous batches. To solve these problems, we provide data showing that the incorporation of an enhancement system consisting of streptavidin-polymerized horseradish peroxidase conjugate greatly improved the sensitivity of the MM3-COPRO ELISA and enabled reduction of the incubation time. These modifications enabled the detectability of the assay to be 150 pg/mL, thus enabling detection of infection in animals harboring only one fluke.