Infection by gastrointestinal nematodes (GIN), particularly Haemonchus contortus, can be detrimental to sheep health and performance. Genetic susceptibility to GIN varies between breeds, with those lacking high levels of natural resistance often requiring frequent anthelmintic treatment when facing parasitic challenge. Genetic technology can serve as a tool to decrease GIN susceptibility via selection for sheep with reduced fecal egg count (FEC) estimated breeding values (EBVs). However, the physiological changes that result from implementation of this strategy are not well described. Additionally, there is a need for comparison of animals from recent selective breeding against breeds with inherent GIN resistance. In this study we administered a challenge of H. contortus to Dorper x White Dorper (DWD; n = 92) lambs that have been genetically selected for either low (DWD-) or high (DWD+) FEC EBVs and Barbados Blackbelly x Mouflon (BBM; n = 19) lambs from a genetically resistant breed backgrounds. Lamb FEC, packed-cell volume (PCV) and serum IgG were measured at intermittent levels over 5 weeks. At day 21 and day 35, the selectively bred DWD- had a lower mean FEC compared to DWD+, but were higher than BBM. Reductions in both PCV and serum IgG from initial day 0 levels were observed in DWD lambs, but not in BBM. Furthermore, from a subset of lambs (n = 24) harvested at day 21, DWD- only tended (p = 0.056) to have lower mean worm counts than DWD+, with BBM having the lowest mean worm count. Differentially expressed genes (DEGs) identified via RNA-sequencing of abomasal tissue at day 21 indicate a more pronounced Th2 immune response and more rapid worm expulsion occurred in iBBM than iDWD- and iDWD+ lambs. However, gene expression in DWD- suggests an association between reduced FEC EBV and gastric acid secretion and the ability to limit worm fecundity. Ultimately, selection of Dorper sheep for low FEC EBV can reduce susceptibility to GIN, but it will likely require multiple generations with this trait as a breeding priority before presenting a similar resistance level to Caribbean breeds.

One of the most common factors limiting donkey health and productivity is infection with gastrointestinal nematode parasites. From December 2021 to May 2022, a cross-sectional study was conducted in and around Shone town, Hadiya zone, southern Ethiopia, to estimate the prevalence of donkey GIT nematode parasite infection and to assess its associated risk factors. For the coprological examination, 384 simple randomly selected donkeys were sampled from four peasant associations. To identify parasitic eggs in feces, the standard flotation technique was used. In the donkeys examined, the overall prevalence of gastrointestinal nematodes was 75.26% Strongyles (48.17%), Parascaris equorum (11.45%), Strongyloides (5.99%), and mixed infection (Strongyles + Parascaris (9.11%) and Strongyles + Strongyloides (0.52%)) were the most commonly encountered nematodes. There was also a statistically significant difference in the prevalence of donkey gastrointestinal parasites by sex, body condition, and management system (p < 0.05). Donkeys with semi-intensified (OR = 8.99) and poor body condition (OR = 6.48) were at an increased risk of infection compared to intensive management and good body condition. In conclusion, the current study demonstrated that gastrointestinal nematodes are the major health challenges for donkeys in the study area. As a result, strategic regular deworming, improved housing, and feeding management were recommended to improve the health and productivity of donkeys in the study area.

Gastrointestinal nematode (GIN) infestations are a major constraint to sheep production in the West Indies (WI). Intensive and semi-intensive management systems are most commonly employed. These islands display tropical weather patterns with wet and dry seasons. Semi-intensive farming combined with increased rainfall during the wet season has been reported to be most favourable for development and survival of GIN. This study was conducted to determine whether there was a relationship between GIN burdens in sheep with seasonality and management practices of farmers in Trinidad and Tobago (T&T). Farms were visited on a monthly basis from January to December 2017. A maximum of ten sheep, three to nine months of age, were selected from each farm. A total of 3,053 faecal samples were collected and analysed using the Modified McMaster technique. Environmental data on daily precipitation and temperature were collected from the Trinidad and Tobago Meteorological Office during the period of sampling. A mixed effects negative binomial regression model was constructed to analyse the relationship between gastrointestinal nematode faecal egg counts (GINFEC) with season, management system and use of dewormers as fixed effects and farm as a random effect. Average diurnal temperatures of T&T fluctuated between 23.2°C to 32.6°C and 23.9°C to 32.3°C in the dry and wet seasons, respectively. Average daily precipitation ranged between 1.6-1.8 mm and 6.1-8.5 mm during the dry and wet seasons, respectively. A decreased risk of 0.34 (95% CI 0.25-0.47, p < .0001) for GINFEC was observed in dewormed animals versus not dewormed. Semi-intensive management systems experienced an increased risk of GINFEC by 1.39 (95% CI 1.05-1.84, p = .021) compared with intensive and the risk of GINFEC was reduced by 0.40 (95% CI 0.33-0.49, p < .0001) in the wet season versus the dry. A higher prevalence of GIN was observed during the drier months of the year. Climatic conditions observed in T&T remained favourable for GIN survival, development and distribution year-round. Proper management is therefore required for reducing the occurrence of GIN in sheep of T&T throughout the year. This is the first reported study in the WI on the influence of seasonality and management on GIN infestations in sheep during the dry and wet seasons. Further investigation is needed to elucidate why GIN burdens appear to be higher in the dry season than the wet season. This study can be used as a baseline for public education in T&T as well as other developing countries.

Haemonchus contortus and Haemonchus placei are two closely related economically important parasites of ruminants. Their close morphological similarity, common occurrence as co-infections and ability to hybridize makes definitive diagnosis and epidemiological studies in field populations challenging. In this paper, we describe the development of a panel of microsatellite markers that can be used to discriminate and study the genetics of these two parasite species in co-infections and mixed field populations. We have identified two additional microsatellites (Hp52 and Hp53), in addition to three previously reported microsatellites (Hcms3561, Hcms53265 and Hcms36) that have a discrete set of alleles between the two species. Multilocus genotyping of worms with this 5 marker panel from 3 geographically diverse H. placei isolates and 4 geographically diverse H. contortus populations allows unambiguous species assignment of individual worms. This panel of markers should provide a valuable resource in studying the biology and epidemiology of these important ruminant parasite species in the field.