Is gastrointestinal strongyle faecal egg count influenced by hour of sample collection and worm burden in goats?

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.): Third edition of the guideline for evaluating efficacy of anthelmintics in ruminants (bovine, ovine, caprine)

This guideline is aimed at those who are involved in the assessment of anthelmintic efficacy in ruminant livestock species (bovine, ovine and caprine). The intent is to provide a framework that can be adopted worldwide for the testing of anthelmintics in ruminants, such that studies carried out in different countries can be compared and thereby unnecessary duplication can be reduced. Recommendations are made for the selection, housing and feeding of study animals, the type of studies required, the method used to conduct those studies, the assessment of results and the standards for defining anthelmintic efficacy.

Variation in allele frequencies in benzimidazole resistant and susceptible isolates of Haemonchus contortus during patent infection in lambs

We evaluated the variation in the frequency of benzimidazole (BZ) resistance-associated alleles at codons 200, 167 and 368 (F200Y, F167Y, V368L) of the β-tubulin isotype 1 gene during the patent period in isolates of Haemonchus contortus susceptible and resistant to BZ using pyrosequencing. Four lambs 5-6 months old were infected with 5000-6000 infective third-stage larvae (L3) of the susceptible MHco1 and the multi-resistant MHco4 isolates, respectively. Faecal samples were collected 28-times during 20-90 days post-infection (dpi). Coprocultures were subsequently prepared to produce L3 for genotyping. The frequency of the resistant allele (TAC) at codon 200 in MHco1 was lowest at 43 and 76 dpi with at each time point 0% and highest at 36 dpi with 10.85%, with a mean of 6.47% ± 2.39 and a coefficient of variation of 37.01%. The frequency of the TAC at codon 200 in MHco4 was lowest at 76 dpi with 25.6% and highest at 90 dpi with 49.25%, with a mean of 35.7% ± 4.42 and a coefficient of variation of 12.39%. No resistance alleles were detected in MHco1 at either codon 167 or 368. For MHco4 isolate, resistance alleles were detected only on codon 167 with a mean of 8.00% ± 4.83 and a mean coefficient of variation of 60.40%. Our results demonstrate the considerable variation in the frequency of resistant alleles in the susceptible and resistant isolates during the patent period. This variation should be considered when testing for the presence of BZ resistance in populations of gastrointestinal parasites, especially those with a low frequency of TAC.

Haemonchus contortus Parasitism in Intensively Managed Cross-Limousin Beef Calves: Effects on Feed Conversion and Carcass Characteristics and Potential Associations with Climatic Conditions

The objectives of the study were: (a) to study the effect of Haemonchus spp. on the growth performance characteristics of fattening calves, (b) to assess any potential effects on carcass characteristics and (c) to investigate the potential role of climatic conditions in the process of the infection. The study was conducted for 201 days in an intensively managed cross-Limousin herd. The animals were divided into two equal groups: those receiving anthelmintic treatment (AT) and the untreated (C) controls. The same nutritional regime was applied to both groups and the feed consumption was calculated daily. Standard parasitological examinations were performed at weekly intervals. At slaughter, carcasses were weighed and assessed for conformation and fat cover classes. Climatic variables were obtained for the location of the farm and a temperature-humidity index was calculated. Before anthelmintic treatment with ivermectin, there was no difference in parasitic burdens between the two groups: 544 (AT) vs. 554 (C) epg, whilst after it, counts were 0 and 450–700 epg, respectively, with over 96% of larvae identified as Haemonchus spp. and, later, confirmed as Haemonchus contortus. It was concluded that treated animals had a higher average total bodyweight gain, higher feed conversion ratio and carcass yield of superior quality than controls. There was a difference between the two groups in the pattern of reduction of dry matter intake as the temperature-humidity index increased.

A note on the relationship between fecal larval excretion and Protostrongylus rufescens lungworm burden in sheep

The examination of feces for stages of parasitic helminths is the most widely used methodology for the intravital diagnosis in domestic animals of patent endoparasitism including pulmonary nematode infections. Although there is only little information on the relationship of lungworm larval excretion and corresponding parasite burdens, fecal larval counts are used as indirect measure ("biomarker") for the intensity of infection, for instance in anthelmintic efficacy studies. To assess the relationship between fecal larval and Protostrongylus rufescens parasite counts in sheep, log-transformed data of 14 naturally infected animals were analyzed. The larval excretion of the sheep was monitored in approximately weekly intervals over 6 weeks before lungworm recovery. Analyses were performed on the larval counts (at a single time point or counts averaged over several consecutive time points) relating to parasite counts. Fecal larval counts and the P. rufescens nematode burden (range, 17 to 406) were significantly and strongly correlated (p < 0.05 for all analyses; Spearman's r > 0.6) with the number of larvae excreted increasing with increasing lungworm burden. Subsequently performed regression analysis demonstrated a statistically significant strong linear relationship between P. rufescens worm and fecal larval counts (p < 0.01 for all analyses; R², range 0.5094 to 0.8150). Analyses based on larval counts averaged over two or more consecutive time points resulted in higher Spearman's r and R² compared with analyses based on single time point larval counts. Despite of some variability, the analyses indicate that fecal larval counts can be regarded as a useful measure of the P. rufescens burden in sheep.

Anthelmintic resistance in ruminants: challenges and solutions

Anthelmintic resistance (AR) is a growing concern for effective parasite control in farmed ruminants globally. Combatting AR will require intensified and integrated research efforts in the development of innovative diagnostic tests to detect helminth infections and AR, sustainable anthelmintic treatment strategies and the development of complementary control approaches such as vaccination and plant-based control. It will also require a better understanding of socio-economic drivers of anthelmintic treatment decisions, in order to support a behavioural shift and develop targeted communication strategies that promote the uptake of evidence-based sustainable solutions. Here, we review the state-of-the-art in these different fields of research activity related to AR in helminths of livestock ruminants in Europe and beyond. We conclude that in the advent of new challenges and solutions emerging from continuing spread of AR and intensified research efforts, respectively, there is a strong need for transnational multi-actor initiatives. These should involve all key stakeholders to develop indicators of infection and sustainable control, set targets and promote good practices to achieve them.

Quantitative Monitoring of Selected Groups of Parasites in Domestic Ruminants: A Comparative Review

Parasites have had a significant impact on domestic ruminant health and production for a long time, but the emerging threat of drug resistance urgently requires an improved approach to parasite monitoring and control activities. The study reviewed the international literature to analyze the different proposals for the sampling approach and the quantitative estimation of parasite burdens in groups of animals. Moreover, the use of thresholds to decide when and which animal to treat was also investigated. The findings of the study highlighted the presence of a wide-ranging literature on quantitative monitoring for gastrointestinal nematodes (GIN), while more limited data were found for coccidia, and no specific indications were reported for tapeworms. Concerning liver flukes, bronchopulmonary nematodes (BPN) and permanent ectoparasites (lice and mange mites), the diagnostic process is usually aimed at the detection of the parasite rather than at the burden estimation. The main research gaps that need further investigation were also highlighted. For some groups of parasites (e.g., GIN and coccidia) the quantitative approach requires an improved standardization, while its usefulness needs to be confirmed for others (e.g., BPN and lice). The development of practical guidelines for monitoring is also encouraged.

Immunopathological Response, Histological Changes, Parasitic Burden, and Egg Output in Sheep Naturally Infected by Dicrocoelium dendriticum

Simple Summary

Dicrocoelium dendriticum, commonly known as the lancet liver fluke, is a liver parasite that affects ruminants and occasionally other species, including humans. The aim of this study was to investigate the histological modification and the phenotype of inflammatory cells in the livers of sheep naturally infected with D.dendriticum and the correlation of these variables with the parasitic burden, egg output, and gross appearance of the liver. We studied twenty-four sheep selected on the basis of positive D. dendriticum fecal egg counts. Gross and histological modifications of the liver and the number of adult D. dendriticum worms were examined. Macroscopically, the livers were swollen with thickened bile ducts, cholangitis, and fibrosis. Histologically, we observed leucocyte infiltration, bile duct hyperplasia, and fibrosis. Lesions were present in different degrees of severity and were scored. A significant positive association was observed between the number of adult worms recovered from the liver, egg per gram, macroscopic lesions, fibrosis, and bile duct hyperplasia. A significant negative association was observed among these variables and the degree of leukocyte infiltration. The immunohistochemical examination showed a CD3+ predominant cell population in all assessed animals. These findings allow us to better understand the complex mechanism of the host–parasite interaction, in relation to the egg output and parasitic burden in dicrocoeliosis.

Abstract

The aim of this study was to investigate the correlation between infection by Dicrocoelium dendriticum (class Trematoda) and the animal host response in terms of macroscopic lesions, the immunopathological response, and histological changes in the livers of naturally infected sheep. Twenty-four sheep were selected on the basis of positive D. dendriticum fecal egg counts (FECs). Gross and histological injuries were scored. A positive significant association was observed between the number of adult worms recovered from the liver, FEC, macroscopic lesions, fibrosis, and bile duct hyperplasia. A significant negative association was observed among these variables and the degree of leukocyte infiltration. In addition, immunophenotyping of the inflammatory cells was carried out using primary antibodies against T cell epitopes (CD3+, CD4+, and CD8+), B cell epitopes (CD79α), and the ionized calcium-binding adapter molecule 1 (IBA-1) antigen. Independently of the severity of the D. dendriticum infection, the predominant cell population was CD3-positive and associated with lesser numbers of CD79α- and Iba-I-positive cells. An increase in Iba-1-positive cells was observed in the livers of animals with a high worm burden. Our results provide a reference basis to better understand the local immune response in sheep naturally infected by D. dendriticum in relation to the FEC and parasitic burden.

Interaction between abomasal blood feeder Haemonchus contortus and intestinal mucosal browser Trichostrongylus colubriformis during co-infection in Boer goats

This study was conducted to investigate potential interactions between the abomasal blood feeder Haemonchus contortus and the intestinal mucosal browser Trichostrongylus colubriformis among deliberately infected Boer goats. Faecal and blood samples were collected twice a week for eight weeks from 25 parasite-naïve goats. Correlation analysis and multiple linear regression models were conducted to explore the association between phenotypic variables and variables taken at necropsy. Positive associations were identified between total FEC and log T. colubriformis number (r = 0.62, p < 0.05) as well as between IgA and peripheral eosinophil counts (r = 0.65, p < 0.05). A negative correlation was observed between T. colubriformis and log H. contortus number (r=-0.56, p < 0.05). Multiple linear regression models show that H. contortus and T. colubriformis interacted with each other. T. colubriformis appeared to contribute more significantly to the variation of FEC than H. contortus. Co-infection induced an IgA response which was only effective against T. colubriformis but not protective against H. contortus infection. This could be seen via significant associations of IgA with both nematode species but with the effect of IgA differing for H. contortus and T. colubriformis. In this study, H. contortus infection was not detrimental to the goats with no observed impact on PCV. This could be because the growth of T. colubriformis as represented by its length was associated with reduced number and composite burden of H. contortus during co-infection, or possibly due to low infection dosage. Improved understanding of the impact of H. contortus and T. colubriformis and their interaction from natural co-infection studies is beneficial for a better understanding of the goat-parasite interaction and its potential impacts on the health and productivity of animals.

Seasonality of helminth infection in wild red deer varies between individuals and between parasite taxa

Parasitism in wild mammals can vary according to myriad intrinsic and extrinsic factors, many of which vary seasonally. However, seasonal variation in parasitism is rarely studied using repeated samples from known individuals. Here we used a wild population of individually recognized red deer (Cervus elaphus) on the Isle of Rum to quantify seasonality and intrinsic factors affecting gastrointestinal helminth parasitism over the course of a year. We collected 1020 non-invasive faecal samples from 328 known individuals which we then analysed for propagules of three helminth taxa: strongyle nematodes, the common liver fluke Fasciola hepatica and the tissue nematode Elaphostrongylus cervi. Zero-inflated Poisson models were used to investigate how season, age and sex were associated with parasite prevalence and count intensity, while Poisson models were used to quantify individual repeatability within and between sampling seasons. Parasite intensity and prevalence varied according to all investigated factors, with opposing seasonality, age profiles and sex biases between parasite taxa. Repeatability was moderate, decreased between seasons and varied between parasites; both F. hepatica and E. cervi showed significant between-season repeatability, while strongyle nematode counts were only repeatable within-season and showed no repeatability within individuals across the year.

Genetic variation in and relationships among faecal worm eggs recorded in different seasons of the year at the Tygerhoek farm in South Africa

Gastrointestinal nematodes result in severe economic and production losses to the sheep industry. An increase in resistance of the nematodes to chemicals used for control, as well as a demand of consumers for meat products free from chemicals, has fostered research on alternative control strategies. Breeding for resistance to nematodes offers an alternative to control parasitism but its effectiveness depends on genetic variation in faecal worm egg count (FWEC), an indirect measure of parasite resistance. A historic dataset of FWEC from four Merino lines subjected to natural parasite challenge was used to estimate genetic parameters for FWEC in three seasons (autumn, winter and spring) using a repeated records animal model, followed by a three-trait animal model analysis treating FWEC in different seasons as separate traits. The effects of selection line, birth year, sex, the sex x birth year interaction, season and the season x year interaction were significant when using 4994 records recorded from 1997 to 2000 (p < 0.001). The heritability of log-transformed FWEC amounted to 0.09 ± 0.02, with no contribution from the animal permanent environmental variance to the between animal variation across seasons. Three-trait heritability estimates for log-transformed FWEC amounted to 0.07 ± 0.05 in autumn, 0.13 ± 0.05 in winter and 0.19 ± 0.05 in spring. These results suggest sufficient genetic variation in FWEC to support selection for lower log-transformed FWEC. However, the best time to record data for selection is after the break of the season in winter and in spring, when sheep are stimulated by a greater intake of infective larvae from the pasture after the first rains. Genetic correlations among FWEC in the respective seasons were moderate to high, ranging from 0.55 to 0.89. Phenotypic correlations, on the other hand, were significant but lower in magnitude, ranging from 0.09 to 0.16. These results provide useful information for developing strategies for the genetic improvement of ovine resistance to gastrointestinal nematodes under Mediterranean conditions in South Africa by using FWEC as an indicator trait.

Diagnosis, Treatment and Management of Haemonchus contortus in Small Ruminants

Haemonchus contortus is a highly pathogenic, blood-feeding nematode of small ruminants, and a significant cause of mortalities worldwide. Haemonchosis is a particularly significant threat in tropical, subtropical and warm temperate regions, where warm and moist conditions favour the free-living stages, but periodic outbreaks occur more widely during periods of transient environmental favourability. The clinical diagnosis of haemonchosis is based mostly on the detection of anaemia in association with a characteristic epidemiological picture, and confirmed at postmortem by the finding of large numbers of H. contortus in the abomasum. The detection of impending haemonchosis relies chiefly on periodic monitoring for anaemia, including through the 'FAMACHA' conjunctival-colour index, or through faecal worm egg counts and other laboratory procedures. A range of anthelmintics for use against H. contortus is available, but in most endemic situations anthelmintic resistance significantly limits the available treatment options. Effective preventative programmes vary depending on environments and enterprise types, and according to the scale of the haemonchosis risk and the local epidemiology of infections, but should aim to prevent disease outbreaks while maintaining anthelmintic efficacy. Appropriate strategies include animal management programmes to avoid excessive H. contortus challenge, genetic and nutritional approaches to enhance resistance and resilience to infection, and the monitoring of H. contortus infection on an individual animal or flock basis. Specific strategies to manage anthelmintic resistance centre on the appropriate use of effective anthelmintics, and refugia-based treatment schedules. Alternative approaches, such as biological control, may also prove useful, and vaccination against H. contortus appears to have significant potential in control programmes.

Effect of gastro-intestinal nematode infection on sheep performance: a systematic review and meta-analysis

Background

Gastrointestinal nematode (GIN) infections are common in domestic sheep and impact directly and indirectly on the health of infected animals as well as on the associated economic production. In this study, we aim at summarizing the current knowledge on the influence of GIN infections on sheep production by conducting a systematic review. A subsequent meta-analysis of relevant studies was performed to provide an estimate of the effect of GIN infections on weight gain, wool production and milk yield.

Methods

A literature search was performed on the CAB, Pubmed and Web of Science database for the period 1960–2012. Inclusion criteria were: 1) Measurement of at least one production parameter. 2) Comparison between groups of sheep with different nematode burdens. 3) Same conditions regarding all aspects except parasite burden between groups. 4) Quantitative measurements of one or more production traits.

Results

Altogether, 88 studies describing 218 trials were included in this review. The majority of studies (86 %) reported that GIN infections had a negative effect on production but this was reported to be statistically significant in only 43 % of the studies. Meta-analysis indicated that performances of sheep infected with nematodes was 85, 90 and 78 % of the performance in uninfected individuals for weight gain, wool production and milk yield respectively. Our results suggest a possible reporting bias or small study effect for the estimation of the impact of GIN infections on weight gain. Finally, a general linear model provided an estimate for the decrease in weight gain in relation to the increase in faecal egg count of nematodes.

Conclusion

This study underlines the importance of GIN infections for sheep production and highlights the need to improve parasite management in sheep, in particular in face of challenges such as anthelmintic resistance.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-015-1164-z) contains supplementary material, which is available to authorized users.

Bovine fasciolosis: prevalence, relationship between faecal egg count and worm burden and its economic impact due to liver condemnation at Rudsar abattoir, Northern Iran

The present study was conducted to evaluate the prevalence of Fasciola hepatica, the economic losses from liver condemnation and the relationship between burden of F. hepatica in liver and EPG of F. hepatica in Rudsar city (north of Iran). Between May 2011 and May 2012, a total of 680 slaughtered cattle were examined for the presence of F. hepatica in the liver. Data collected were analyzed by the sex, age, season and breed of the animals. In this study 137 cattle (20.14 %) were found to be positive for F. hepatica. The mean fluke burden in the affected livers was 14 ± 2 flukes per liver. There were no seasonal and age-related differences (P > 0.05) in prevalence of F. hepatica, but there was a statistically significant association (P < 0.05) between the prevalence with breed and sex and a high prevalence of F. hepatica was observed in indigenous and female cattle. The financial loss due to liver condemnation almost was estimated to be 2,750 USD. To study the relationship between burden of F. hepatica in liver and EPG of F. hepatica, faeces collected from rectum of cattles in slaughterhouse were examined by McMaster egg- counting technique. The abundance (worm burden) of F. hepatica in contaminated liver was classified in three group, group A, <10 worms/liver, in group B, 10-30 worms/liver and in group C, >30 worms/liver. In this groups (A-C) EPG of F. hepatica was 156, 240 and 620 respectively. There was a strong relationship between EPG and burden of worm in the liver.

Histopathological, histochemical and immunohistochemical findings of the small intestine in goats naturally infected by Trichostrongylus colubriformis

Gastrointestinal (GI) strongyle infection remains one of the main constraints to goat production worldwide. Samples of small intestine from 15 Syrian goats naturally infected with Trichostrongylus colubriformis were examined by routine histology, histochemistry and immunohistochemistry to describe the histological changes and the phenotypes of inflammatory cellular components of the mucosa. Results indicated that the immune response to infection by T. colubriformis was characterized by an increased rate of the severity of the histologic lesions, an increase rate of T cell lymphocytes recruitment to the intestinal mucosa and quantitative and qualitative changes in the histochemical composition of mucin in goblet cells.

The potential of Elephantorrhiza elephantina as an anthelminthic in goats

Elephantorrhiza elephantina Bruch. Skeels. is used by farmers in the Eastern Cape Province to control helminths in goats. An in vitro study revealed efficacy of its fractions against adult Haemonchus contortus. This study was conducted to validate efficacy of fractions in vivo, on gastrointestinal nematodes in naturally infected goats. A total of 36 goats (18 males and 18 females) between ages of 8 and 12 months were used; these were randomly assigned to six treatments (A-F). For treatments A and B, goats received Prodose orange® (Albendazole 1.92 % m/v, closantel 3.94 % mv) at 2 ml/10 kg and distilled water at 0.5 ml/kg per os, respectively, whereas those under treatments C to E received aqueous fractions of E. elephantina at concentrations of 12. 5, 25, 50 and 75 mg/ml, dosed at 2 ml/10 kg. On days 1, 28 and 56, faecal samples were collected for faecal egg counts (FEC) and larval count, blood samples taken for packed cell volume (PCV) and body weights recorded to assess weight changes. The aqueous fraction caused highest the total faecal egg count reductions (TFECR) % of 81.7 %, 96.8 % and 98.6 % at doses of 25, 50 and 75 mg/kg, respectively, on day 56. This was comparable to the commercial drug Prodose orange®, which caused TFECR% of 94.9 % at the same time. The fraction also caused reduction of Haemonchus contortus and strongyloides larvae at all dose levels, but these were not significantly different (P > 0.05) to the negative control. There was an increase in body weights of animals at dose concentrations of 25, 50 and 75 mg/kg. Animals receiving the fraction had weight increases of between 3 and 4 kg by end of experiment (over 56 days), but those drenched with Prodose orange ® gained by less than 2 kg. The fraction also increased PCV levels at all doses on days 28 and 56 and this was comparable to the group on commercial drug. The reductions of FEC and worm larvae, as well as increase in PCVs are indicative that E. elephantina posses some antihelmintic properties against gastrointestinal parasites in goats. With a minimum dose concentration of 25 mg/ml being effective, this means that farmers can use little material. Increase in weight gain revealed in this study may indicate that the plant may have some nutritional value; further study is therefore called for to validate the plant for its nutritive value.