Influence of sex and reproductive status on susceptibility of ruminants to nematode parasitism

Gastrointestinal Parasite Infections and Environmental Sustainability of the Ovine Sector: Eimeria spp. Infections and Nitrogen and Phosphorus Excretions in Dairy Sheep in Italy

In sheep farming, gastrointestinal parasites can be responsible for significant reductions in animal health and production. Nitrogen (N) and phosphorus (P) fecal excretions are the main determining factors for N2O emissions from manure management and may pose other environmental problems, such as the acidification and eutrophication of natural habitats. By using the Mini-FLOTAC technique on fecal samples from sheep of different ages and physiological status from 19 dairy sheep farms in Tuscany (central Italy), gastrointestinal parasite infections were evaluated. The animal N and P fecal contents were also assessed, with the aim of evaluating possible relationships between the identified parasites and the environmental sustainability of the examined farms. The obtained results showed that Eimeria spp. (86.36%) and gastrointestinal strongyle (54.55%) infections are prevalent in the examined farms. Moreover, significantly higher (p ≤ 0.05) P and Eimeria oocyst/gram-of-feces (OPG) values were found in fecal samples from animals < 1 year of age, and a significant (p ≤ 0.05) positive correlation resulted between N content and Eimeria OPG in fecal samples from animals in the first month of lactation. The findings from this study suggest for the first time that Eimeria spp. infections may have an impact on the environmental sustainability of sheep farming.

Nestedness and beta diversity of gastrointestinal helminth communities in common warthogs, Phacochoerus africanus (Suidae), at 2 localities in South Africa

Few studies have investigated the ecological interactions between wild species of Suidae and their parasites, leaving our knowledge concerning this host–parasite system fragmented. In the present study, we applied network studies to analyse community nestedness in helminth assemblages of common warthogs, Phacochoerus africanus (Gmelin) (Suidae). Helminth data were compiled from 95 warthogs, including young and adult males and females, from 2 different conservation areas in Mpumalanga and Limpopo Provinces, South Africa, collected monthly over a period of 1 year each. The aim was to study the effect of host sex, age and season of sampling on the structure of helminth infracommunities harboured by the warthogs and to search for non-random structural patterns in the warthog–helminth interaction networks. Furthermore, we investigated the influence of a warthog's age, sex and season of sampling on beta diversity and dark diversity of their helminth infracommunities. Lastly, we asked whether the effects of host sex, age and sampling season on helminth communities differed between the 2 localities. We found that helminth communities of warthogs were nested and host–parasite interactions were influenced by all 3 factors as well as combinations thereof. However, the resulting patterns differed at the 2 localities, indicating that local environmental processes are important drivers of community structure.

Life history matters: Differential effects of abomasal parasites on caribou fitness

Parasites can impact wildlife populations through their effects on host fitness and survival. The life history strategies of a parasite species can dictate the mechanisms and timing through which it influences the host. However, unravelling this species-specific effect is difficult as parasites generally occur as part of a broader community of co-infecting parasites. Here, we use a unique study system to explore how life histories of different abomasal nematode species may influence host fitness. We examined abomasal nematodes in two adjacent, but isolated, West Greenland caribou (Rangifer tarandus groenlandicus) populations. One herd of caribou were naturally infected with Ostertagia gruehneri, a common and dominant summer nematode of Rangifer sspp., and the other with Marshallagia marshalli (abundant; winter) and Teladorsagia boreoarcticus (less abundant; summer), allowing us to determine if these nematode species have differing effects on host fitness. Using a Partial Least Squares Path Modelling approach, we found that in the caribou infected with O. gruehneri, higher infection intensity was associated with lower body condition, and that animals with lower body condition were less likely to be pregnant. In caribou infected with M. marshalli and T. boreoarcticus, we found that only M. marshalli infection intensity was negatively related to body condition and pregnancy, but that caribou with a calf at heel were more likely to have higher infection intensities of both nematode species. The differing effects of abomasal nematode species on caribou health outcomes in these herds may be due to parasite species-specific seasonal patterns which influence both transmission dynamics and when the parasites have the greatest impact on host condition. These results highlight the importance of considering parasite life history when testing associations between parasitic infection and host fitness.

The cost of host genetic resistance on body condition: evidence from divergently selected sheep

Trade‐offs between host resistance to parasites and host growth or reproduction can occur due to allocation of limited available resources between competing demands. To predict potential trade‐offs arising from genetic selection for host resistance, a better understanding of the associated nutritional costs is required. Here, we studied resistance costs by using sheep from lines divergently selected on their resistance to a common blood‐feeding gastro‐intestinal parasite (Haemonchus contortus). First, we assessed the effects of selection for high or low host resistance on condition traits (body weight, back fat, and muscle thickness) and infection traits (parasite fecal egg excretion and loss in blood haematocrit) at various life stages, in particular during the periparturient period when resource allocation to immunity may limit host resistance. Second, we analysed the condition–infection relationship to detect a possible trade‐off, in particular during the periparturient period. We experimentally infected young females in four stages over their first 2 years of life, including twice around parturition (at 1 year and at 2 years of age). Linear mixed‐model analyses revealed a large and consistent between‐line difference in infection traits during growth and outside of the periparturient period, whereas this difference was strongly attenuated during the periparturient period. Despite their different responses to infection, lines had similar body condition traits. Using covariance decomposition, we then found that the phenotypic relationship between infection and condition was dominated by direct infection costs arising from parasite development within the host. Accounting for these within‐individual effects, a cost of resistance on body weight was detected among ewes during their first reproduction. Although this cost and the reproductive constraint on resistance are unlikely to represent a major concern for animal breeding in nutrient‐rich environments, this study provides important new insights regarding the nutritional costs of parasite resistance at different lifestages and how these may affect response to selection.

Detection of Zoonotic Gastrointestinal Pathogens in Dairy Sheep and Goats by Using FilmArray® Multiplex-PCR Technology

The objectives of this study were (a) to detect gastrointestinal pathogens in faecal samples of sheep and goats using the FilmArray® GI Panel and (b) to evaluate factors that were associated with their presence. Faecal samples from ewes or does in 70 sheep flocks and 24 goat herds in Greece were tested for the presence of 22 gastrointestinal pathogens by means of the BioFire® FilmArray® Gastrointestinal (GI) Panel. The most frequently detected pathogens were Shiga-like toxin-producing Escherichia coli stx1/stx2 (94.7% of farms), Giardia lamblia (59.6%), and Campylobacter spp. (50.0% of farms). Other pathogens detected were Cryptosporidium spp., Salmonella spp., enterotoxigenic E. coli lt/st, Yersinia enterocolitica, E. coli O157, Rotavirus A, Shigella/enteroinvasive E. coli, and Plesiomonasshigelloides. There was a difference in the prevalence of detection of pathogens between sheep and goat farms only for Salmonella spp.: 18.3% versus 0.0%, respectively. Mixed infections were detected in 76 farms (80.9% of farms), specifically 57 sheep flocks and 19 goat herds, with on average, 2.5 ± 0.1 pathogens detected per farm. The body condition score of ewes in farms, in which only one pathogen was detected in faecal samples, was significantly higher than that of ewes in farms, in which at least two pathogens were detected: 2.55 ± 0.11 versus 2.31 ± 0.04. In sheep flocks, the number of pathogens in faecal samples was significantly higher in farms with semi-extensive management. In goat herds, the number of pathogens in faecal samples was positively correlated with average precipitation and inversely correlated with temperature range in the respective locations.

Parasite dynamics in untreated horses through one calendar year

Background

Horses are host to a plethora of parasites. Knowledge of the seasonality of parasite egg shedding and transmission is important for constructing parasite control programs. However, studies describing these patterns are sparse, and have largely been conducted only in the United Kingdom. This study evaluated strongylid egg shedding patterns and transmission dynamics of Strongylus vulgaris in naturally infected and untreated mares and foals through one calendar year in Kentucky, USA. The study also investigated the existence of a peri-parturient rise (PPR) in strongylid egg counts in foaling mares and collected information about Strongyloides westeri and Parascaris spp. in the foals.

Methods

This study was conducted from January to December 2018. A herd of 18 mares, one stallion, and 14 foals born in 2018 were followed throughout the year. Sera and feces were collected biweekly from all horses, and worm burdens enumerated in 13 foals at necropsy. An S. vulgaris ELISA antibody test was run on all serum samples. Fecal egg counts were determined for all horses, and coproculture and qPCR assay were employed to test for the presence of S. vulgaris in the mature horses. Data were analyzed using the proc glimmix procedure in the SAS 9.4 software program.

Results

We found a general lack of seasonality in strongylid egg shedding throughout the year among the mature horses, and no PPR was demonstrated. Shedding of S. vulgaris eggs displayed a higher abundance during the spring, but findings were variable and not statistically significant. Anti-S. vulgaris antibody concentrations did not display significant fluctuations in the mature horses, but evidence of passive transfer of antibodies to the foals was demonstrated, and foals assumed their own production of antibodies starting at approximately 20 weeks of age. Overall, colts shed higher numbers of strongylid, ascarid, and S. westeri eggs than fillies.

Conclusions

This study demonstrated a lack of seasonality in strongylid egg shedding for the study population, which is in stark contrast to previous studies conducted elsewhere. This strongly suggests that more studies should be done investigating these patterns under different climatic conditions.

Graphical Abstract

Factors associated with small lungworm infections in heavily infected sheep in southeast South Australia

This field observational study describes the seasonal pattern of small lungworm infections under different grazing managements from August 2018 to March 2019. Live weight, lungworm and gastrointestinal nematode infection, as well as pasture type grazed and snail density, were measured at 5 farm visits. Across all visits and mobs, about one quarter to one half of sheep were positive for small lungworm, although prevalence was as low as 0% and as high as 78%. The density of the intermediate host molluscs was greater than 1600 snails/m² in irrigated perennial lucerne pasture when it was grazed ('Pasture A'), but was low (<300) in non-irrigated perennial pasture ('Pasture B') and non-irrigated forage crop ('Pasture C'). Overall, non-infected lambs had a similar live weight compared with the small lungworm infected lambs (mean difference -0.6 kg; 95% CI -1.6 to 0.2; P = 0.1). The odds ratio of small lungworm infection associated with a twofold increase in worm egg count was 1.7 (95% CI 1.1 to 2.7; P = 0.02). Rather than a distinct seasonal pattern of infection, we found that small lungworm can occur throughout the year, with prevalence most influenced by pasture type (irrigated vs dryland), grazing management and the population density of the intermediate hosts. Importantly, this study suggested that small lungworm infection did not reduce lamb live weights. It reinforced that to improve sheep productivity, well-established determinants of production, such as correct grazing management to optimise pasture quality and strategies to reduce infections with gastrointestinal nematodes, should be the priority of farm managers.

Evaluation of resistance to gastrointestinal helminth nematodes in two naturally infected indigenous Nigerian goat breeds

Tropical goat breeds often have at least modest resistance to gastrointestinal nematode parasites (GIN), but enhancement of GIN resistance is important for breed improvement. This study compared changes in fecal egg count (FEC), packed cell volume, and body weight in Red Sokoto (RS) and Sahelian (SH) male and female weaner kids and adult goats. The RS is found throughout Nigeria, but the SH is found only in the arid Sahel. Goats were evaluated fortnightly for 20 times (MT) under normal grazing conditions and natural GIN infection over 9.5 months, beginning in the dry season (November) and ending at the end of the subsequent wet season (August). Animals were dewormed at the start of the study and during the rainy season (MT 18). Breed differences in FEC and PCV were not observed in weaners. Weaner females had lower FEC than males but were rapidly re-infected after deworming, perhaps in association with attainment of puberty. Adult SH goats of both sexes had lower FEC than RS goats in MT 8 through 17, suggesting a stronger acquired immune response. The FEC in lactating females of both breeds increased rapidly after deworming, to ≥ 3000 eggs per gram of feces at MT 19 and 20. The optimal time to evaluate GIN resistance in weaners was during the early rainy season, but the decision to focus on the initial high FEC near MT 15 or wait until mobilization of the acquired immune response near MT 17 requires further consideration.

Severity and prevalence of small lungworm infection on three South Australian farms and associations with sheep carcass characteristics

This field and abattoir study assessed the association of the severity and prevalence of small lungworm lesions with the carcass characteristics of 1332 lambs and adult sheep bred on three farms in southeast SA. Liveweight and measures of lungworm infection were measured on farm, then lung lesions and carcass characteristics assessed at slaughter. The overall prevalence of small lungworm lesions at slaughter was 79 % (928/1177; 95 % CI 76, 81), with a prevalence of 87 % (569/658; 95 % CI 84, 89) in lambs, and 69 % (359/519; 95 % CI 65, 73) in adults, respectively. Small lungworm infected lambs and adults had a similar hot standard carcass weight and dressing percentage compared to non-infected animals, both overall and within their respective cohort. Overall, the mean carcass weight for non-infected and infected lambs was 23.4 kg (95 % CI 18, 29), and 23.6 kg (95 % CI 18, 29), respectively, with a mean difference of 0.2 kg (95 % CI -0.4, 0.8; P = 0.5). Mean carcass weight for non-infected and infected adults was 21.3 kg (95 % CI 15, 28), and 21.5 kg (95 % CI 15, 28), with a mean difference of 0.2 kg (95 % CI -0.5, 0.9; P = 0.5). This study confirmed a very high prevalence of small lungworm lesions in sheep bred on farms in this region of SA, but their hot standard carcass weights were not reduced by these lesions. Additional information to compare the presence of lesions with productivity within an individual was collected at slaughter which provided more detailed information than is currently collected by routine abattoir surveillance. The limitations of the currently available diagnostic tests for small lungworm were also demonstrated. This indicated a need for the development of more sensitive tests to assess lungworm infections both on farm and at the abattoir. Currently, farmers in this region are concerned about the very high prevalence of small lungworm in their sheep, but this study provides reassurance that the presence of mild lesions does not reduce production.

Physiological, Immunological and Genetic Factors in the Resistance and Susceptibility to Gastrointestinal Nematodes of Sheep in the Peripartum Period: A Review

Parasitic diseases of sheep involving gastrointestinal nematodes (GIN) are one of the main problems that affect fl ock productivity, especially during the peripartum period. Around lambing, the ewes are immunosuppressed and the nematode faecal egg count (FEC) increases at four weeks before lambing, reaching a peak between the fourth and sixth week postpartum and subsequently decreasing towards weaning. Prolactin has been credited with a suppressive effect on immune system, along with other hormones that intervene in metabolism, such as leptin, which has an important role in the activation of other hormones. Cortisol has also been included; this is stimulated by any stressful event and inhibits the proliferation of T-cells and alters the function of immunoglobulins. Another related hormone is pepsinogen, which is considered a marker of the integrity of the abomasum mucosa, as well as the albumin concentration that increases in the presence of a GIN infection. The humoral and cellular immune response, as well as inflammatory reactions, are the main mechanisms of action against GIN. Lymphocytes direct the effector mechanisms in a Th2 cell response, including interleukins (IL-4, IL-5, IL-9, IL-10) and transforming growth factor beta (TGF-β) together with immunoglobulins (IgA, IgG, IgM and IgE), which prevent the invasion of pathogens. Eosinophils with a cytotoxic effect are indicators of a parasitic infection, with importance in the immune protection of infected individuals. The genetic selection of resistant individuals measured by FEC is dependent on the heritability (h²), which is moderately inheritable and highly repeatable. Effects that influence the resistance or susceptibility of sheep to GIN infections in the peripartum period are determined by the interaction of various factors, such as genotype or breed, nutrition, age, type of birth, season and production system, etc., which are studied in this review.

The effects of parasitism on ewes for prime lamb production in western Victoria

Context Internal parasites are estimated to cost the Australian sheep industry AUD436 million per annum (p.a.). Aims To assess the effects of parasitism in flocks producing prime lambs in the 500–700 mm p.a rainfall. area of Victoria. Methods Ewes on two farms that followed ‘best practice’ gastrointestinal parasite control programs (BP) and two farms that did not (regionally typical, TYP) were compared. Separate cohorts of ewes were monitored from pregnancy scanning to their subsequent joining each year for three consecutive seasons. Observations included worm egg count (WEC), bodyweight, condition score and presence of breech soiling (dag). These were compared between groups that were treated to suppress parasitism (SUP) and those treated according to the usual program used on that farm (NSUP). Data from individual ewes were analysed using a multivariable, mixed-effects regression model. Key results After adjusting for known confounders, SUP ewes were 1.2 (95% CI 0.80–1.6) kg heavier than NSUP ewes. Mature SUP ewes were significantly heavier than NSUP ewes at their next joining on 6 of 18 occasions, mostly following winters when ewes experienced nutritional stress. Ewe hoggets and Merino ewes were generally more susceptible to parasitism than mature non-Merino ewes; single-bearing ewes were less susceptible than those bearing twins. The effects of parasitism were reduced when peri-parturient ewes had an optimal condition score and grazed adequate pastures. Conclusions Ewes were more vulnerable to parasitism when immature, twin-bearing, or under nutritional stress. Some of the greatest differences between SUP and NSUP ewes occurred following periods of low feed availability and/or ewe condition score. The difference between the mean bodyweight of SUP and NSUP Merinos was not always greater than that of the non-Merinos. WECs are not a sole reliable indicator of the effects of parasitism in this class of sheep. Implications Immature or twin-bearing ewes, and those in suboptimal body condition, should be managed considering their increased vulnerability to parasitism, and WEC interpreted alongside other factors. Controlled release capsules were not cost effective in reducing production loss from gastrointestinal nematodes in most years but may be effective in reducing the effects of clinical parasitism in some cases.

Assay to compare cell- and antibody-mediated immune responses in domestic sheep and goats

Assessment of immune fitness is valuable in many aspects of livestock management and research. Determining immune consequences of selection for increased disease resistance or inhabiting various environments or climates can lead to different management decisions. The ability to measure immune responses due to different diets, pregnancy status, or aging will increase insight about how these factors contribute to overall immune health. The main objective of these experiments was to adapt a methodology used in cattle and pigs to measure both the humoral and cell-mediated immune response in sheep and goats. The route of administration of two antigens, Candida albicans and hen egg white lysozyme, were compared in sheep to determine differences in antibody or cell-mediated immune response. Subcutaneous injection produced a larger (P < 0.001) cell-mediated response compared to intramuscular injection. Inoculation in the axillary space produced a larger (P = 0.0031) antibody response compared to neck region. Finally, methodology was confirmed in goats. Complete blood cell counts were compared and lymphocytes were highest in low cell-mediated responders while eosinophils were highest in average antibody-mediated responders. This work provides a means to measure immune fitness in sheep and goats allowing for future experiments examining environmental or genetic effects on the immune response.

Demographic and reproductive associations with nematode infection in a long-lived mammal

Infection by macroparasites, such as nematodes, varies within vertebrate host systems; elevated infection is commonly observed in juveniles and males, and, for females, with different reproductive states. However, while such patterns are widely recognized in short-lived model systems, how they apply to long-lived hosts is comparatively understudied. Here, we investigated how infection varies with host age, sex, and female reproduction in a semi-captive population of individually marked Asian elephants Elephas maximus. We carried out 1,977 faecal egg counts (FECs) across five years to estimate nematode loads for 324 hosts. Infection patterns followed an established age-infection curve, whereby calves (5 years) exhibited the highest FECs and adults (45 years) the lowest. However, males and females had similar FECs across their long lifespan, despite distinct differences in life-history strategy and clear sexual dimorphism. Additionally, although mothers invest two years in pregnancy and a further three to five years into lactation, nematode load did not vary with four different measures of female reproduction. Our results provide a much-needed insight into the host-parasite dynamics of a long-lived host; determining host-specific associations with infection in such systems is important for broadening our knowledge of parasite ecology and provides practical applications for wildlife medicine and management.

Epidemiology and Control of Gastrointestinal Nematodes of Cattle in Southern Climates

Control of gastrointestinal nematodes (GIN) can have both economic and health benefits for cattle operations in the southern United States. In the past several decades, GIN control has relied almost exclusively on the use of anthelmintics. With the increase in anthelmintic resistance new strategies must be developed. Anthelmintic use should be minimized by integrating grazing management and a good herd health program into GIN control programs. This takes knowledge of GIN biology and epidemiology in the region (climate and weather) combined with specific information from the ranch.

Reproduction affects immune defenses in the guinea pig even under ad libitum food

Reproduction is one of the costliest processes in the life of an animal. Life history theory assumes that when resources are limiting allocation to reproduction will reduce allocation to other essential processes thereby inducing costs of reproduction. The immune system is vital for survival. If reproduction reduces investment in immune function, this could increase the risk of disease, morbidity and mortality. We here test in the guinea pig, if even under ad libitum food conditions, pregnancy and lactation reduce the activity of the adaptive and innate immune system compared to the reaction of non-reproducing animals. In response to a challenge with keyhole limpet haemocyanin the antibody-mediated adaptive immunity during (pregnancy and) lactation was reduced. Pregnant and lactating females showed higher levels of bacterial killing activity, an integrated measure of innate immunity, than non-reproducing females. However, two major effectors of the innate immunity, the natural antibody and the complement of pregnant and lactating females showed lower levels than in non-reproducing females. Pregnant and lactating females did not differ significantly in the expressed levels of innate immunity. Our results indicate that changes in the immune response during reproduction are physiological adjustments to predictable allocation problems, because they happen even under ad libitum food availability.

Patterns and variation in the mammal parasite-glucocorticoid relationship

Parasites are ubiquitous and can strongly affect their hosts through mechanisms such as behavioural changes, increased energetic costs and/or immunomodulation. When parasites are detrimental to their hosts, they should act as physiological stressors and elicit the release of glucocorticoids. Alternatively, previously elevated glucocorticoid levels could facilitate parasite infection due to neuroimmunomodulation. However, results are equivocal, with studies showing either positive, negative or no relationship between parasite infection and glucocorticoid levels. Since factors such as parasite type, infection severity or host age and sex can influence the parasite-glucocorticoid relationship, we review the main mechanisms driving this relationship. We then perform a phylogenetic meta-analysis of 110 records from 65 studies in mammalian hosts from experimental and observational studies to quantify the general direction of this relationship and to identify ecological and methodological drivers of the observed variability. Our review produced equivocal results concerning the direction of the relationship, but there was stronger support for a positive relationship, although causality remained unclear. Mechanisms such as host manipulation for parasite survival, host response to infection, cumulative effects of multiple stressors, and neuro-immunomodulatory effects of glucocorticoids could explain the positive relationship. Our meta-analysis results revealed an overall positive relationship between glucocorticoids and parasitism among both experimental and observational studies. Because all experimental studies included were parasite manipulations, we conclude that parasites caused in general an increase in glucocorticoid levels. To obtain a better understanding of the directionality of this link, experimental manipulation of glucocorticoid levels is now required to assess the causal effects of high glucocorticoid levels on parasite infection. Neither parasite type, the method used to assess parasite infection nor phylogeny influenced the relationship, and there was no evidence for publication bias. Future studies should attempt to be as comprehensive as possible, including moderators potentially influencing the parasite-glucocorticoid relationship. We particularly emphasise the importance of testing hosts of a broad age range, concomitantly measuring sex hormone levels or at least reproductive status, and for observational studies, also considering food availability, host body condition and social stressors to obtain a better understanding of the parasite-glucocorticoid relationship.

Quantification of differences in resistance to gastrointestinal nematode infections in sheep using a multivariate blood parameter

Breeding for resistance to gastrointestinal nematodes (GIN) in sheep relies largely on the use of worm egg counts (WEC) to identify animals that are able to resist infection. As an alternative to such measures of parasite load we aimed to develop a method to identify animals showing resistance to GIN infection based on the impact of the infection on blood parameters. We hypothesized that blood parameters may provide a measure of infection level with a blood-feeding parasite through perturbation of red blood cell parameters due to feeding behaviour of the parasite, and white blood cell parameters through the mounting of an immune response in the host animal. We measured a set of blood parameters in 390 sheep that had been exposed to an artificial regime of repeated challenges with Trichostrongylus colubriformis followed by Haemonchus contortus. A simple analysis revealed strong relationships between single blood parameters and WECs with correlation coefficients -0.54 to -0.60. We then used more complex multi-variate methods based on supervised classifier models (including Bayesian Network) as well as regression models (Lasso and Elastic Net) to study the relationships between WECs and blood parameters, and derived algorithms describing the relationships. The ability of these algorithms to classify sheep GIN resistance status was tested using the WEC and blood parameters collected from a different group of 418 sheep that had acquired natural infections of H. contortus from pasture. We identified the most resistant and most susceptible animals (10% percentiles) of this group based on WECs, and then compared the identities of these animals to the identities of animals that were predicted to be most resistant and most susceptible by our algorithms. The models showed varying abilities to predict susceptible and resistant sheep, with up to 65% of the most susceptible animals and 30% of the most resistant animals identified by the Elastic Net model algorithms. The prediction algorithms derived from female sheep data performed better than those for male sheep in some cases, with the predicted animals accounting for up to 50-60% of the actual resistant and susceptible female animals. Heritability values were calculated for blood parameters and the aggregate trait descriptions defined by the novel prediction algorithms. The aggregate trait descriptions were moderately heritable and may therefore be suitable for use in genetic selection strategies. The present study indicates that multivariate models based on blood parameter data showed some ability to predict the resistance status of sheep to infection with H. contortus.

Resistance of ewes to gastrointestinal nematode infections during the peripartum and dry periods and the performance of their lambs

ABSTRACT This study aimed to evaluate the resistance of Texel (Tx) and Ile de France (IF) sheep to gastrointestinal nematode infections in the periparturient period and after weaning, and the performance of their lambs. Fecal samples were collected from 19 IF and 17 Texel ewes to determine fecal egg counts (FEC) and larval cultures were prepared to determine the prevalence of nematodes. The ewes were weighed to determine body weight (BW) and blood samples were taken to determine the packed cell volume (PCV) and plasm protein values (PPV). The ewes were classified into two groups by FEC (heavy and moderate infection). The IF presented higher FECs than Tx 28 and 14 days before parturition; 14, 28, and 56 days after parturition; and 28 days after weaning (P<0.05). In the weaning and dry periods, the IF presented higher PCVs than Tx (P<0.05). The PPV did not differ between the groups (P>0.05). The IF presented a higher BW than Tx 14, 28, and 42 days after parturition, and in the weaning and dry periods (P<0.05). The ewes of both breeds classified as moderately infected had the highest BW at weaning (P<0.05). IF ewes with a moderate infection produced weaning lambs that were heavier than those of Tx with the same level of infection (P<0.05). Overall, Tx ewes presented a better ability to withstand infections during the periparturient period and after weaning. Although the IF ewes presented the highest FEC and more intense periparturient rise, they managed to maintain their level of production.

Trials with the Haemonchus vaccine, Barbervax®, in ewes and lambs in a tropical environment: Nutrient supplementation improves protection in periparturient ewes

Haemonchus contortus is an economic problem in sheep farms worldwide, mainly in the tropics and subtropics. A vaccine against haemonchosis, called Barbervax^®, was evaluated in ewes under two nutritional status, naturally infected with gastrointestinal nematodes. Ewes were divided into four groups: Supplemented Diet - Vaccine; Supplemented Diet - No vaccine; Basal Diet - Vaccine and Basal Diet - No vaccine. Their lambs were divided in Vaccinated and No vaccine. Ewes were immunised six times starting about 1 month of pregnancy with the first three doses at 3 week intervals and the last three shots at 4 week intervals. Supplemented ewes had higher body weight, body score and packed cell volume compared with those fed a basal diet. Both groups of vaccinated ewes showed a similar response in circulating anti-vaccine antibodies but the vaccine had no discernible effect on either body weight, body score and packed cell volume. There was a marked group difference in the number of ewes that received precautionary treatments with anthelmintic. All 14 Basal Diet - No vaccine ewes required treatment. In contrast only 7 ewes, in the Supplemented Diet - Vaccine group required anthelmintic treatment. In the Basal Diet - Vaccine and in the Supplemented Diet - No Vaccine groups, 12 and 13 ewes needed anthelmintic treatment, respectively. Vaccinated lambs showed much higher antibody titres resulting in 80% less Haemonchus spp. egg counts comparing with no vaccine lambs. Taken together these results clearly suggest that in pregnant and lactating ewes a combined protective effect between vaccination and improved nutrition resulted in fewer precautionary anthelmintic treatments. Thus, it was possible to achieve a more sustainable level of control of the haemonchosis, less dependent on anthelmintic drugs.

Body Protein Reserves Sustain Maternal Performance in Early Lactation but Dietary Protein Is Necessary to Maintain Performance and Immune Responses to Nippostrongylus brasiliensis in Lactating Rats

Background

It has been shown that dietary protein supplementation during lactation boosts immunity in Nippostrongylus brasiliensis-infected periparturient rats. It is not known whether body protein reserves accumulated during gestation have a similar effect during lactation.

Objective

This study aimed to quantify the impact of body protein reserves and dietary protein supplementation on maternal performance and immune responses to N. brasiliensis during lactation.

Methods

Multiparous female Sprague-Dawley rats were administered a primary infection of N. brasiliensis before mating and were restriction-fed either 60 g [low-protein diet gestation (Lge)] or 210 g [high-protein diet gestation (Hge)] crude protein (CP) per kilogram of dry matter (DM) until parturition. From parturition onward, dams were restriction-fed either 100 g [low-protein diet lactation (Lla)] or 300 g [high-protein diet lactation (Hla)] CP per kilogram of DM, generating 4 different dietary treatments. A subset of rats was sampled before parturition; postparturition, dams were secondarily infected with N. brasiliensis and samples were collected at days 5 and 11 postparturition.

Results

Maternal performance until parturition, as measured by pup weight, was better in Hge rats than in Lge rats [Lge: 4.84 g; Hge: 6.15 g; standard error of the difference (SED): 0.19]. On day 11, pup weights of dams with reduced protein reserves fed protein during lactation (Lge-Hla; 20.28 g) were higher than their counterparts from Hge-Lla dams (17.88 g; SED: 0.92). Worm counts were significantly different between Lge-Lla-fed (253; 95% CI: 124, 382) and Hge-Hla-fed (87; 95% CI: 22, 104) dams on day 11 (P = 0.024). The expression of splenic interleukin 13 (Il13) and arachidonate 15-lipoxygenase (Alox15) was significantly higher (P < 0.05) in Hge-Hla dams compared with Lge-Lla dams on day 5.

Conclusions

Although protein reserves were adequate to maintain maternal performance in the early stage of lactation in dams infected with N. brasiliensis, they were not adequate to maintain maternal performance and effective immune responses at later stages. Dietary protein supplementation was required to achieve this.

The use of targeted selective treatments on controlling gastrointestinal nematodes in different sheep categories under grazing system

ABSTRACT: Infections with gastrointestinal nematodes can impair both the animal health and performance. Thereby, the aim of this study was to evaluate the use of targeted selective treatments as the FAMACHA© system and faecal egg count on controlling gastrointestinal nematodes in different sheep categories under grazing system. Thirty Santa Inês sheep, six in each category (six weaning, six weaned lambs, six non-pregnant ewes, six pregnant ewes and six lactating ewes were used. Sheep were weighed, and blood and faecal samples were collected on day 0, 15, 30, 45, 60 and 75 for determination of faecal egg count (FEC), packed cell volume (PCV), total plasma protein (PPT) and the mucosa colour by FAMACHA© system in the morning (1) and afternoon (2). The faecal egg count was higher (p=0.0039) in weaning and weaned lambs compared to the non-pregnant, pregnant and lactating ewes. Also, FEC differed between ewes with higher counts in lactating ewes. The observation of eye mucosae showed a frequency of 100% of FAMACHA© scores ranged of 2.45 to 2.91 in the morning, differing (p=0.0494) among the categories, where weaned lambs showed better score. The animal categories and period interaction had a significant (p=0.0148) effect on FAMACHA© score 1 with better score in weaned lambs compared to the pregnant ewes at day 0, 15 and 75. In addition, weaned lambs were presented better FAMACHA© score compared with weaning lambs and lactating ewes at day 45 than weaning lambs at day 60 and 75. Packed cell volume in the morning and in the afternoon was influenced by days of collection with lower percentage at 30 days of experiment. The FAMACHA© system seems to be a suitable method to detect parasite infections. However, use of all available methods increases the accuracy of the diagnosis and promotes better control of gastrointestinal nematodes in grazing sheep.

Helminth parasites of Mabuya arajara Rebouças-Spieker, 1981 (Lacertilia: Mabuyidae) from Chapada do Araripe, northeastern Brazil

We provide data on the helminth fauna from the digestive tract of the lizard Mabuya arajara Rebouças-Spieker, 1981 from Chapada do Araripe, northeastern Brazil. Seventy one of the 127 lizards examined (56%) were infected with four nematode species: Physalopteroides venancioi and Physaloptera sp. (Physalopteridae), Strongyluris oscari (Heterakidae), and Parapharyngodon alvarengai (Pharyngodonidae), the latter being the component species (prevalence 53.5%; mean intensity of infection 3.37 ± 2.0; discrepancy index D = 0.69). The helminth P. alvarengai infected M. arajara throughout the year and showed increased infection rates in July, at the beginning of the dry season. In addition to the relationship with seasonality, lizards with greater body length and/or body mass were more infected. Relationships between number of parasites and body mass and with the sexes of lizards, on the other hand, were not found. Mabuya arajara represents a new host for these nematodes. This study contributes to the knowledge of the helminth fauna associated with the digestive tract of lizards from South America and the Caatinga domain.

Investigations into nematode parasites of goats in pastoral and crop livestock systems of Ethiopia

We generated epidemiological information on the prevalence of nematode parasites and possible resistance/resilience of goats in three areas, Bati, Shinille, and Borana, of Ethiopia. A total of 350 breeding does were randomly selected and monitored for one year. Fecal egg counts (FEC), packed cell volume (PCV), body weight (BW), body condition score (BC), and fecal larvae identification were done. In Borana, the long rainy season had higher FEC, lower PCV, lower BC, and smaller BW compared to dry and short rainy seasons (p < 0.01). For Bati and Shinille, the differences between the seasons were significant (p < 0.01) but not clear-cut. Breed differences were also evident (p < 0.01) on FEC, PCV, and BW. The mean FEC for Borana goat was 158.5 ± 1.12, whereas for Bati it was 38.9 ± 1.12. Age differences did not have effect on FECs, PCV, and BC. No differences in parasite load, as reflected by FEC, was verified between male and female goats. In the wet season, large numbers of larvae were recovered from the study sites except for Bati. In the three sites, Haemonchus contortus followed by Trichostrongylus colubriformis were the dominant species. In the dry season, however, very little number of larvae was recovered, only of H. contortus in Bati and of H. contortus and T. colubriformis in Borana. Generally, the level of nematode infection was low. Therefore, nematode parasites are not a major problem and strategic control program using broad spectrum anthelmintic is not advisable. Rather, monitoring parasite load and selective de-worming should be sufficient to reduce productivity loses and pasture contamination.

Effects of metabolizable protein on performance and faecal egg count of the parasitized ewe

The periparturient relaxation (PPR) in acquired immunity in ewes has been ascribed to various factors, including poor nutrition (Barger, 1993). Clinically, the faecal egg count (FEC) may increase during PPR when the ewe is continuously infected with gastrointestinal parasites. As such, the periparturient ewe plays an important role in the epidemiology of parasitic infections. The nutritional basis of PPR probably includes metabolizable protein (MP), since host's responses, in terms of immunity and resilience, are highly proteinaceous by nature. We propose that the PPR directly results from less MP being available to maintain acquired immunity and resilience, since an increasing amount of MP is directed to bodily functions with higher priority (reproduction). It is hypothesized that the increased FEC in the parasitized periparturient ewe reduces if her MP-intake exceeds her assumed MP-requirement (AFRC, 1993).

Genetic line comparisons and genetic parameters for endoparasite infections and test-day milk production traits

Keeping dairy cows in grassland systems relies on detailed analyses of genetic resistance against endoparasite infections, including between- and within-breed genetic evaluations. The objectives of this study were (1) to compare different Black and White dairy cattle selection lines for endoparasite infections and (2) the estimation of genetic (co)variance components for endoparasite and test-day milk production traits within the Black and White cattle population. A total of 2,006 fecal samples were taken during 2 farm visits in summer and autumn 2015 from 1,166 cows kept in 17 small- and medium-scale organic and conventional German grassland farms. Fecal egg counts were determined for gastrointestinal nematodes (FEC-GIN) and flukes (FEC-FLU), and fecal larvae counts for the bovine lungworm Dictyocaulus viviparus (FLC-DV). The lowest values for gastrointestinal nematode infections were identified for genetic lines adopted to pasture-based production systems, especially selection lines from New Zealand. Heritabilities were low for FEC-GIN (0.05-0.06 ± 0.04) and FLC-DV (0.05 ± 0.04), but moderate for FEC-FLU (0.33 ± 0.06). Almost identical heritabilities were estimated for different endoparasite trait transformations (log-transformation, square root). The genetic correlation between FEC-GIN and FLC-DV was 1.00 ± 0.60, slightly negative between FEC-GIN and FEC-FLU (-0.10 ± 0.27), and close to zero between FLC-DV and FEC-FLU (0.03 ± 0.30). Random regression test-day models on a continuous time scale [days in milk (DIM)] were applied to estimate genetic relationships between endoparasite and longitudinal test-day production traits. Genetic correlations were negative between FEC-GIN and milk yield (MY) until DIM 85, and between FEC-FLU and MY until DIM 215. Genetic correlations between FLC-DV and MY were negative throughout lactation, indicating improved disease resistance for high-productivity cows. Genetic relationships between FEC-GIN and FEC-FLU with milk protein content were negative for all DIM. Apart from the very early and very late lactation stage, genetic correlations between FEC-GIN and milk fat content were negative, whereas they were positive for FEC-FLU. Genetic correlations between FEC-GIN and somatic cell score were positive, indicating similar genetic mechanisms for susceptibility to udder and endoparasite infections. The moderate heritabilities for FEC-FLU suggest inclusion of FEC-FLU into overall organic dairy cattle breeding goals to achieve long-term selection response for disease resistance.

The relative effects of reproductive condition, stress, and seasonality on patterns of parasitism in wild female black howler monkeys (Alouatta pigra)

Parasitic infections in wildlife are shaped by host-related traits including individual reproductive condition. It has been argued that female primates are more susceptible to infectious diseases during pregnancy due to short-term changes in immune function that result in reduced ability to combat infections. Likewise, lactation, which is the most energetically expensive state, may affect immunity and infection risk due to tradeoffs between milk production and maintenance of immune function. Here, we examine the degree to which parasite prevalence and parasite richness are affected by female reproductive condition and stress levels in wild female black howler monkeys (Alouatta pigra). Over the course of one year, we collected fresh fecal samples from 15 adult females belonging to seven black howler groups living in Escárcega, Mexico. Fecal samples were used for parasitological analysis and for measuring fecal glucocorticoid metabolites (i.e., stress biomarker). We found that the prevalence of intestinal parasites and parasite richness did not differ among non-pregnant, pregnant, and lactating females. Fecal glucocorticoid metabolite levels increased significantly during pregnancy and during the first month of lactation, and positively predicted the probability of Controrchis biliophilus infection. Parasite prevalence and richness decreased during the months of increased rainfall. We conclude that reproductive physiology has limited consequences on intestinal parasitic infection risk in female black howler monkeys and that seasonal environmental fluctuations have greater effects.

Transcriptional immune response in mesenteric lymph nodes in pigs with different levels of resistance to Ascaris suum

A single nucleotide polymorphism on chromosome 4 (SNP TXNIP) has been reported to be associated with roundworm (Ascaris suum) burden in pigs. The objective of the present study was to analyse the immune response to A. suum mounted by pigs with genotype AA (n = 24) and AB (n = 23) at the TXNIP locus. The pigs were repeatedly infected with A. suum from eight weeks of age until necropsy eight weeks later. An uninfected control group (AA; n = 5 and AB; n = 5) was also included. At post mortem, we collected mesenteric lymph nodes and measured the expression of 28 selected immune-related genes. Recordings of worm burdens confirmed our previous results that pigs of the AA genotype were more resistant to infection than AB pigs. We estimated the genotype difference in relative expression levels in infected and uninfected animals. No significant change in expression levels between the two genotypes due to infection was observed for any of the genes, although IL-13 approached significance (P = 0.08; Punadjusted = 0.003). Furthermore, statistical analysis testing for the effect of infection separately in each genotype showed significant up-regulation of IL-13 (P<0.05) and CCL17 (P<0.05) following A. suum infection in the 'resistant' AA genotype and not in the 'susceptible' AB genotype. Pigs of genotype AB had higher expression of the high-affinity IgG receptor (FCGR1A) than AA pigs in both infected and non-infected animals (P = 1.85*10-11).

Genetic resistance to gastro-intestinal nematode parasites in Red Maasai, Dorper and Red Maasai X Dorper ewes in the sub-humid tropics

Resistance to naturally acquired gastro-intestinal (GI) nematode parasite infections (predominantly Haemonchus contortus) was studied in 166 Red Maasai, 230 Dorper and 294 crossbred (Red Maasai Х Dorper) ewes in the sub-humid coastal region of Kenya. Live weights (LWT), blood packed-cell volume (PCV) and faecal egg counts (PEC) were recorded at mating, 3 months post mating, 1 week before lambing and 1, 2 and 3 months post lambing for four separate lambings that took place between 1993 and 1996. The Red Maasai ewes were more resistant to GI nematode infections than Dorper ewes as shown by their significantly lower FEC and significantly higher PCV at most of the sampling times over the reproductive cycle. The breed difference for FEC was significant in the lactating ewes but not in the non-lactating ewes. At most sampling times, the crossbred ewes were as susceptible as the Dorper ewes in terms of both PCV and FEC, particularly at the 1 and 2 month post-lambing samplings. Resistance was also manifested by a lower proportion of ewes having to be treated with an anthelmintic and a lower mortality rate in the Red Maasai than the Dorper. The Red Maasai ewes were significantly lighter by about 1 to 2 kg than the Dorper ewes at all sampling times. There was a significant increase in FEC and decrease in PCV over the first 2 months of lactation in lactating ewes compared with non-lactating ewes. This peri-parturient increase in FEC occurred in both breeds and the crossbreds but was more marked in the susceptible Dorper ewes.

The relationship between protein nutrition, reproductive effort and breakdown in immunity toTeladorsagia circumcinctain periparturient ewes

A nutritional hypothesis for the occurrence of the periparturient relaxation of immunity (PPRI) to gastrointestinal nematodes was tested within the bounds of a nutrient partitioning framework. It was hypothesized that at times of a scarce supply of metabolizable protein (MP), an increase in MP supply or a reduction in MP demand (having singles instead of twins) should lower the extent of PPRI in sheep. Twenty-one single- and 21 twin-bearing and -rearing Finn-Dorset ewes, 2 to 7 years old, and repeatedly infected withTeladorsagia circumcincta, were given one of three pelleted foods (no. = 7). The foods were formulated to supply 0·8 (L), 1·0 (M) and 1·2 (H) times the MP requirements during lactation, and were offeredad libitumfrom d–21to d35(d0 is day of parturition). Faecal egg counts (FEC) were assessed twice weekly as an indicator for host resistance. Dry-matter intake (DMI) during late pregnancy was higher than expected, and MP supply did not limit performance at this stage. In accordance with the hypothesis, there were no indications of a breakdown of immunity toT. circumcinctaduring late pregnancy. DMI during lactation did not differ between the single- and twin-rearing ewes. Calculated milk production was lower for the L than for the M and H ewes, especially for the twin-rearing ewes. A temporarily elevated FEC was observed during the first few days in lactation, which was probably mainly due to changes in faecal output rather than to PPRI. The FEC returned to low, late pregnancy levels at d12and remained low for the single- but not for the twin-rearing ewes (P< 0·001). Overall, the L ewes had higher FEC than the M and H ewes from d19onwards; this effect was more pronounced for the twin- than for the single-rearing ewes. It was postulated that DMI achieved overcame MP scarcity and thus prevented breakdown in immunity in the single-rearing ewes. The data support the view that, at times of MP scarcity, an increase in MP supply and reduction in MP demand can lower the extent of the breakdown in immunity towardsT. circumcincta.

Inheritance of faecal egg counts during early lactation in Scottish Blackface ewes facing mixed, natural nematode infections

This paper presents an analysis of nematode faecal egg counts from Scottish Blackface ewes facing mixed, natural nematode infections (predominantly Teladorsagia circumcincta). The data set comprised 1445 measurements on 421 ewes taken at 4 and 6 weeks post-lambing, over a 4-year period. The ewes, themselves, were the progeny of 73 sires and 285 dams. Only Strongyle eggs were consistently present, and faecal egg counts from this genera ranged from zero (0·4 of all measurements) to 3388 eggs per g. Faecal egg counts were significantly affected by the number of lambs reared and suckled (increasing reproductive burden led to higher counts) by ewe age (older ewes had lower counts) and by previous selection history (ewes from a line previously selected for increased carcass fatness had lower faecal egg counts than ewes from a conversely selected lean line). The heritability of log-transformed faecal egg counts was 0·23 (s.e. 005) and the repeatability, including both within- and between-year permanent environmental effects, was 0·25 (s.e. 004). The apparent presence or absence of infection had a heritability of 015 (s.e. 007) on the observed scale and 0·39 (s.e. 016) when analysed as a binomial threshold trait. The genetic correlation between average 4-week weight of lamb suckled by the ewe and faecal egg counts was 0·24 (s.e. 010). The results suggest that faecal egg counts during early lactation are heritable and influenced by the reproductive performance of the ewe. Selection to reduce nematode faecal egg output from ewes during this period should be successful in reducing pasture larval contamination.

Effect of nutrition in early pregnancy on the periparturient relaxation of immunity to gastro-intestinal parasitism in prolific ewes

The rôle of body reserves stored during early pregnancy on the periparturient breakdown of resistance to nematode parasites was investigated. From the 35th day of pregnancy, 46 ewes were distributed in four groups and given access to a lucerne pelleted diet. Two groups were given food at maintenance (M and C) and the other two were offered food either ad libitum (H) or at 0·70 their maintenance requirements (L) in order to achieve three well differentiated levels of body reserves by the 90th day of pregnancy when backfat thickness reached a mean value of 10·6, 7·5, 7·4 and 5·0 mm for H, M, C, and L treatments respectively. After the 90th day of pregnancy all animals were given food at 50 g/kg live weight per day. All ewes in groups H, M and L received 5000 infective larvae per week (40% Teladorsagia circumcincta, 40% Trichostrongylus colubriformis, 20% Haemonchus contortus) from 5 weeks before to 3 weeks after lambing. The animals in group C remained as uninfected controls.

Host resistance, as measured by faecal egg counts, was significantly affected by the nutritional treatment established during early pregnancy, showing a mean excretion of 546, 766 and 1007 eggs per gram (e.p.g. ) for H, M, and L treatments, respectively, until 3 weeks post lambing. This response was accompanied by a significant effect on circulating eosinophils and better fed ewes showed a higher concentration with a maximum mean value of 10·1, 6·9, 5·5 and 4·0 cells per mm3 for H, M, L and C treatments, respectively, 2 weeks post infection. The effect of the worm infection per se was evident in that the lambs of the M treatment ewes grew at 0·90 of the rate of those in the control treatment (189 v. 213 g/day). Ad libitum feeding in early pregnancy appeared to sufficiently compensate for this depressive effect, with the H ewes producing lambs that grew at a rate similar to those of the C ewes (213 v. 213 g/day).

The results support the view that fat mass stored by ewes in early pregnancy is involved in the expression of immunity against gastro-intestinal nematode infection around parturition. Furthermore, the depressive effect of ewes’ infection on lambs’ growth rate can be overcome by increasing the plane of nutrition of their dams. These results have clear implications for grazing animals, particularly their nutritional management in early pregnancy and provide a simple management strategy in sustainable management systems.

Interactions Between Nutrition and Infections With Haemonchus contortus and Related Gastrointestinal Nematodes in Small Ruminants

Interactions between host nutrition and feeding behaviour are central to understanding the pathophysiological consequences of infections of the digestive tract with parasitic nematodes. The manipulation of host nutrition provides useful options to control gastrointestinal nematodes as a component of an integrated strategy. Focussed mainly on the Haemonchus contortus infection model in small ruminants, this chapter (1) illustrates the relationship between quantitative (macro- and micro-nutrients) and qualitative (plant secondary metabolites) aspects of host nutrition and nematode infection, and (2) shows how basic studies aimed at addressing some generic questions can help to provide solutions, despite the considerable diversity of epidemiological situations and breeding systems.

Relative maturity and the development of immunity to gastrointestinal nematodes in sheep: an overlooked paradigm?

Sheep display considerable variation in both the timing and magnitude of development of immunity to gastrointestinal nematodes (GIN). Onset of immunity is dependent on a number of factors, including antigenic stimulus, nutrition supply, age and size of the animals, the latter of which are confounded. Here, we review the factors associated with the development of immunity to GIN in sheep, particularly in the context of the role that relative maturity may have through applying the rules of genetic size scaling based on examples from published literature. Comparing animals based on their metabolic age, rather than chronological age, may provide an explanation for the timing of immune development and may reduce the variation in immune development that frequently is observed both between and within breeds. Further, this approach may help explain the phenotypic differences in animal performance between animals of varying immunological capacity to GIN through influences on mature body weight. As such, when considering factors influencing immune development to GIN, physiological age or relative maturity may be considered an overlooked paradigm. We propose it may be worthwhile to consider metabolic age when comparing the immune competence of animals to ensure the subjects are at an analogous stage of physiological development.

Negative covariance between parasite load and body condition in a population of feral horses

In wild and domestic animals, gastrointestinal parasites can have significant impacts on host development, condition, health, reproduction and longevity. Improving our understanding of the causes and consequences of individual-level variation in parasite load is therefore of prime interest. Here we investigated the relationship between strongyle fecal egg count (FEC) and body condition in a unique, naturalized population of horses that has never been exposed to anthelmintic drugs (Sable Island, Nova Scotia, Canada). We first quantified variation in FEC and condition for 447 individuals according to intrinsic (sex, age, reproductive status, social status) and extrinsic (group size, location, local density) variables. We then quantified the repeatability of measurements obtained over a field season and tested for covariance between FEC and condition. FECs were high relative to other horse populations (mean eggs per gram ± SD = 1543·28 ± 209·94). FECs generally decreased with age, were higher in lactatingvsnon-lactating females, and unexpectedly lower in males in some part of the island. FECs and condition were both spatially structured, with patterns depending on age, sex and reproductive status. FECs and condition were both repeatable. Most notably, FECs and condition were negatively correlated, especially in adult females.

Effects of age, sex, lactation and social dominance on faecal egg count patterns of gastrointestinal nematodes in farmed eland (Taurotragus oryx)

The eland is a large African antelope that can be bred in a temperate climate, under similar conditions and production systems as cattle. However, knowledge of parasites in farmed elands outside the area of their native habitat is still limited, and information concerning factors that influence these parasites is lacking. Therefore, faecal samples from an entire herd of elands, including calves and adult females and males, were examined monthly over a one year period. Almost 84% of the animals were found to be positive for gastrointestinal nematodes. Strongyle-type eggs were most frequently detected (prevalence 75%), followed by Capillaria sp., Nematodirus sp. and Trichuris sp. eggs. Following culturing eggs to infective larvae, Teladorsagia sp., Trichostrongylus sp., Nematodirus sp., Cooperia sp. and Oesophagostomum sp. were identified. Following necropsy of two calves that died during the study one abomasal nematode (Teladorsagia circumcincta), five small intestinal nematode species (Nematodirus helvetianus, N. spathiger, Cooperia oncophora, C. curticei and Capillaria bovis) and two large intestinal nematodes (Oesophagostomum venulosum and Trichuris ovis) were recovered. From these findings, it is evident that the eland harbours nematodes that are typical for domestic cattle and small ruminants. Morphological and morphometric analyses of recovered nematodes revealed that these parasites do not require any special morphological adaptation to establish infection in elands. The faecal output of strongyle-type and Nematodirus sp. eggs was seasonal, with the highest egg production taking place during spring and summer. Calves had higher faecal egg counts (for all the monitored nematode species) than adults did. Lactation in females was significantly (P<0.0001) associated with higher strongyle nematode egg shedding. Social dominance also affected faecal egg count patterns. The lower the hierarchical position among adults (regardless of sex), the higher the risk of nematode infection. This effect was evident for strongyles (P<0.0001) and Capillaria sp. nematodes (P=0.0065). The results of our study suggest that control measures applicable in domestic cattle and small ruminants might be similarly applicable for controlling gastrointestinal nematode infections in captive farmed elands.

Host sex and age influence endoparasite burdens in the gray mouse lemur

Introduction

Immunosenescence (deteriorating immune function at old age) affects humans and laboratory animals, but little is known about immunosenescence in natural populations despite its potential importance for population and disease dynamics and individual fitness. Although life histories and immune system profiles often differ between the sexes, sex-specific effects of aging on health are rarely studied in the wild. Life history theory predicts that due to their shorter lifespan and higher investment into reproduction at the expense of immune defences, males might experience accelerated immunosenescence. We tested this hypothesis by examining sex-specific age trajectories of endoparasite burden (helminth prevalence and morphotype richness measured via fecal egg counts), an indicator of overall health, in wild gray mouse lemurs (Microcebus murinus). To account for potential interactions between seasonality and host sex or age we examined the predictors of parasite burdens separately for the dry and rainy season.

Results

Contrary to the prediction of immunosenescence, parasite prevalence and morphotype richness decreased at old age in the dry season, indicating acquired immunity by older animals. This pattern was primarily caused by within-individual decline in parasite loads rather than the earlier mortality of highly parasitized individuals. With the exception of an increasing cestode prevalence in males from yearlings to prime age in the rainy season, no evidence was found of male-biased ageing in parasite resistance. Besides this sex*age interaction, host age was uncorrelated with rainy season parasite loads. Seasonality did not affect the overall parasite loads but seasonal patterns were found in the predictors of parasite prevalence and morphotype richness.

Conclusions

These results provide rare information about the age-related patterns of health in a wild vertebrate population and suggest improvement rather than senescence in the ability to resist helminth infections at old age. Overall, males appear not to suffer from earlier immunosenescence relative to females. This may partially reflect the earlier mortality of males, which can render senescence difficult to detect. While helminth infections are not strongly associated with survival in wild gray mouse lemurs, parasite load may, however, reflect overall good phenotypic quality of long-lived individuals, and is a potential correlate of fitness.

Electronic supplementary material

The online version of this article (doi:10.1186/s12983-015-0118-9) contains supplementary material, which is available to authorized users.

Mastitis in sheep--The last 10 years and the future of research

Bacterial mastitis is a significant welfare and financial problem in sheep flocks. This paper reviews the recently published literature, including publications that highlight the significance and virulence factors of the causal agents, especially Staphylococcus aureus and Mannheimia haemolytica, the primary causes of the disease. Research has also contributed to the understanding of risk factors, including genetic susceptibility of animals to infections, supporting future strategies for sustainable disease control. Pathogenetic mechanisms, including the role of the local defenses in the teat, have also been described and can assist formulation of strategies that induce local immune responses in the teat of ewes. Further to well-established diagnostic techniques, i.e., bacteriological tests and somatic cell counting, advanced methodologies, e.g., proteomics technologies, will likely contribute to more rapid and accurate diagnostics, in turn enhancing mastitis control efforts.

Dinâmica de eliminação de oocistos de Eimeria sp. durante a gestação e fase inicial da lactação em cabras nativas criadas extensivamente em região semiárida

<p>Objetivou-se com este estudo caracterizar a dinâmica de eliminação de oocistos de<italic>Eimeria</italic>sp<italic>.</italic> em cabras sem raça definida (SRD), criadas em sistema extensivo na região semiárida, durante a gestação e fase inicial da lactação. Vinte cabras adultas, criadas extensivamente na Caatinga, foram selecionadas e monitoradas durante oito meses. Os valores de Oopg (quantidade de oocistos por grama de fezes) foram acompanhados quinzenalmente do 1º mês de gestação ao 90º dia pós-parto. O Oopg variou durante a gestação, sendo as maiores e menores contagens de 3.300 ± 709 e 1.726 ± 215, respectivamente. Após elevação na primeira quinzena, o Oopg diminuiu gradualmente até o 105º dia e voltou a subir até o final da gestação. No período pós-parto, seguindo a tendência da fase final da gestação, houve aumento progressivo na eliminação de oocistos até o 90º dia de lactação. A quantidade média de oocistos liberados durante a fase inicial da lactação foi de 3.006 ± 102,3 Oopg comparado ao período gestacional de 2.312 ± 98,03 Oopg (P<0,05). A dinâmica de eliminação de oocistos de<italic>Eimeria</italic> sp. em cabras gestantes e lactantes, criadas extensivamente em região semiárida, foi caracterizada por três situações distintas: elevação brusca no início da gestação, seguida por redução gradual no período intermediário da gestação e aumento constante da eliminação de oocistos na fase final da gestação até inicial da lactação.</p>

Interactions between parasitic infections and reproductive efficiency in sheep

This review article summarises the many reports in the literature, confirming that, in sheep, parasitic infections can adversely affect reproductive efficiency; examples, which refer to all parts of the reproductive cycle of sheep, are as follows: trichostrongylosis in ewe-lambs (which can lead to delayed attainment of puberty), myiosis of the prepuce (which can cause impediment of mating), chorioptic mange or trypanosomosis in rams (which can lead to testicular degeneration or azoospermia, respectively), trypanosomosis or sarcoptic mange in pre-conceptual ewes (which can lead to poor conception rates or reduced number of ovulations, respectively), toxoplasmosis or neosporosis in pregnant ewes (which are causes of abortion), trichostrongylosis or trematode infections in lactating ewes (which can cause reduction of milk yield and can be a risk factor for mastitis, respectively), cryptosporidiosis in newborn lambs (which can be a cause of deaths), coccidiosis in growing pre-weaned lambs (which can cause suboptimal growth rate). In other cases, the reproductive status of the animal can influence the parasitic infection; examples are as follows: the increase in faecal parasitic output during the peri-parturient period (as a consequence of the peri-parturient relaxation of immunity), the heavier trichostrongylid infections of twin lambs compared to lambs from single parities (as a consequence of developmental origin issues in twin lambs). All the above examples support the idea of presence of interactions between parasitic infections and reproductive efficiency in sheep.

Prevalence and seasonality of bulk milk antibodies against Dictyocaulus viviparus and Ostertagia ostertagi in Irish pasture-based dairy herds

Infections with Dictyocaulus viviparus and Ostertagia ostertagi nematode parasites are of importance to bovine health and production in temperate areas across the world. Losses due to these parasites in dairy herds can be considerable due to decreased milk productivity and fertility. However, information on current epidemiological patterns in Irish dairy herds is limited. Bulk milk samples were collected from a total of 319 dairy farms across the Republic of Ireland. The D. viviparus samples were tested with an ELISA based on recombinant major sperm protein, while the O. ostertagi samples were tested with an ELISA based on crude saline extract, whole worm O. ostertagi antigen. Management data were collected from the farms using a questionnaire. Logistic regression was used to find significant associations between the presence of antibodies against D. viviparus and O. ostertagi and management factors. The overall prevalence of D. viviparus infection was 62.8%, while over 98% of herds had antibodies to O. ostertagi at the specified cut-off. Both D. viviparus and O. ostertagi antibodies were highest in November, which could be explained by the accumulated uptake of larvae through the grazing season. In herds of farmers that dosed their in-calf heifers with anthelmintics were significantly more likely to be positive for antibodies against D. viviparus infection. This study highlights that both D. viviparus and O. ostertagi infections are widespread in dairy herds in Ireland throughout the grazing season.

Temporal dynamics of helminth infections in eastern grey kangaroos (Macropus giganteus) in Victoria

Parasite infection is increasingly recognised as a factor shaping the population dynamics, life history and behaviour of hosts. However, before the impacts of parasites on wildlife hosts can be investigated, seasonal patterns in host exposure to parasitic agents must be determined. We examined infection patterns at three sites in Victoria, and combined field experiments and observations to construct a generalised life cycle of the helminth community in eastern grey kangaroos (Macropus giganteus). Kangaroo populations in Victoria had very similar helminth communities, with 20–25 species detected at each site. Despite examining relatively few hosts in this study, at least 87% of all gastrointestinal helminths were recovered according to bootstrap estimates. The prepatent period of infection in eastern grey kangaroo nematodes was at least 3 months, and faecal egg output showed a distinct seasonal pattern, with a peak in egg counts from October through to January each year. Data from one site indicated that faecal egg counts were influenced predominantly by the abundance of a single nematode species (Pharyngostrongylus kappa), despite adults accounting for only 7% of the total nematode burden. This highlights the problems associated with using faecal egg counts to estimate nematode burdens in this host. Contamination of pasture plots showed that nematode eggs take ~14 days to larvate once deposited, and that autumn rains likely triggered emergence from faecal pellets. The abundance of infective larvae in the environment therefore appears to be closely tied to environmental conditions, with a peak in infection of hosts in the winter months.

Sex-specific effects of parasitism on survival and reproduction of a rodent host in a subtropical montane region

Parasites can generate complex life history trade-offs in a host. In this study, we experimentally reduced the infection level of intestinal helminth parasites in the Taiwan field mouse (Apodemus semotus) to test (1) whether parasite richness and load are biased towards male or female mice (sex-biased parasitism) and (2) whether the effects of parasitism on the host's survival and reproduction are different between the sexes (sex-specific effects of parasitism). Our findings indicate that neither parasite richness (number of helminth taxa found in a fecal sample) nor parasite load (number of helminth eggs per gram of fecal material) was sexually biased in our A. semotus study population. These results are in agreement with those of previous studies on endoparasites in Apodemus spp., but are in contrast to those on ectoparasites in Apodemus spp. Parasite removal reduced the survival rate of reproducing females, possibly by allowing reproducing females to increase maternal investment in their current litters at the cost of their own future survival. Single-litter mothers with reduced parasitism had a higher body mass than the untreated single-litter mothers, suggesting an increased maternal investment. In addition, the reproductively more active A. semotus, particularly the females, carried higher parasite loads, suggesting a trade-off between reproduction and parasite defense. By demonstrating that parasites can affect life history trade-offs in A. semotus, our results highlight the importance of maintaining variation in life history traits under parasitism risks and illustrate the subtle demographic processes (e.g. reduced future survival among healthy reproducing females) that might be driven by parasitism.