Factors Affecting Gastrointestinal Nematode Infection in Goats




Wetmore, Trixie

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Parasitic infections are one of the costliest concerns in animal production, with over $10 billion each year spent on medications globally. Internal parasites cause $18.2 million in sheep and goat losses annually in the United States alone. Haemonchus contortus is the primary parasitic nematode affecting Texas small ruminant production and contributes to substantial economic losses due to few clinical signs before death, reduced productivity, treatment costs, and is developing anthelmintic resistance worldwide. Small ruminants with anthelmintic resistant nematode infection sell for 14% less than lambs without resistant infections. Some alternatives to standard herd-wide anthelmintic dosing schedules that help mitigate anthelmintic resistance are frequent monitoring via fecal egg counts (FEC) and FAffa MAlan CHArt (FAMACHA), allowing self-medicating with bioactive plants, and determining which factors affect FEC. The proposed work hypothesizes that breed, age, and other factors will affect a goat’s infection level. Previous work shows these factors affect a goat’s FEC. There are two objectives to the proposed work: 1. to determine weekly FEC for 39 goats at Freeman Center for over 1-yr and 2. to determine relationships between assessed factors and FEC measures using regression analysis. The best fit model was zero-inflated negative binomial distribution due to aggregated parasite infections and the zero-frequency class being contaminated with samples that are not part of the infection process. The Spanish-Boer crossbred goats had the highest FEC of evaluated breeds (P < 0.001). January through April were higher than the remaining months, which coincides with the H. contortus proliferation season (P < 0.05).



Breed, Capra hircus, Fecal egg count, Haemonchus contortus, Month, Regression analysis


Wetmore, T. (2022). Factors affecting gastrointestinal nematode infection in goats (Unpublished thesis). Texas State University, San Marcos, Texas.


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