A field study on the occurrence of gastrointestinal nematodes in sheep over the wet and dry seasons in two West Indian islands

ABSTRACT

Objective: Gastrointestinal nematode (GIN) infestations of sheep are considered a major constraint to sheep production in the West Indies. Sheep are semiintensively managed under tropical conditions which are favorable for the development and survival of GIN. This study was conducted to determine if there was a relationship between GIN burdens in sheep with seasonality and management practices of farmers in Trinidad and Tobago (TT). Design and Methodology: Eighteen (18) farms were visited in Trinidad and 23 in Tobago on a monthly basis between January and December 2017. A maximum of ten sheep between three to nine months of age were selected using non-random sampling at each farm. Results: A total of 3053 fecal samples were collected and analyzed using the Modified McMaster Technique. A mixed effects Poisson regression model was constructed to analyze the relationship between eggs per gram (EPG) with season, management and deworming. The standard error was adjusted for clustering according to farm. EPG decreased according to wet season vs. dry season (coef. = - 0.6, 95% CI = -1.17 - -0.03, p = 0.039). Semiintensive management system experienced higher EPG than intensive system (coef. = 1.43; 95% CI = 0.72, - 2.14; p < 0.001). EPG did not vary significantly according to whether the farmer dewormed or not over the period (p = 0.54). Conclusion: Proper management is required for reducing the occurrence of GIN in sheep of TT throughout the year. Further investigation is needed to elucidate why EPG appear to be higher in the dry season than the wet season.