Anthelmintic Resistance in our Local Goat and Sheep Herds: What Can We Do and How Can We Slow Resistance to Improve Herd Health and Sustainability in the Farming Community

Fellow: Isabelle Louge

Mentor: Sabine Mann

Co-Mentor: Jessica McArt, Mary Smith

Department of Clinical Sciences
Sponsor: 2021 Resident Research Grants Program
Title: Anthelmintic Resistance in our Local Goat and Sheep Herds: What Can We Do and How Can We Slow Resistance to Improve Herd Health and Sustainability in the Farming Community
Project Amount: $10,000
Project Period: June 2021 to May 2022

DESCRIPTION (provided by applicant): 

Anthelmintic (dewormer) resistance is a prevalent issue for small ruminant farms of every size and type, especially in systems that allow grazing on pasture, which is typical for our region. High gastrointestinal parasite loads negatively affect the health and productivity of small ruminants, which has a significant impact on the sustainability of local farm systems. In individual animals, parasitic infections can be severe, leading to anemia and death. Most local farms in our area struggle to control parasite burdens, which is compounded by the lack of research detailing parasitic resistance to different drug classes in upstate New York. The goal of this proposed study is to document resistance to available parasiticides (benzimidazoles, levamisole, macrocyclic lactones) in local small ruminant populations and make associations with herd management practices. Using the FAMACHA scoring system for identifying animals that need to be dewormed, our study will enroll 300 small ruminants (150 goats, 150 sheep) based on FAMACHA scores indicating a high parasite burden with Haemonchus contortus, a blood-sucking abomasal worm that causes the greatest losses on local farms. We target enrollment of 13 goat farms and 13 sheep farms to meet the goal number of enrolled animals. Age, body condition score, FAMACHA score, prior deworming, and health events will be recorded for each animal at enrollment. Fecal and blood samples will be collected at enrollment and fecal sample collection repeated two weeks later. Animals will be assigned, following a randomized block design, into one of three treatment categories, each representing one class of parasiticides. A questionnaire of the farmĀ“s parasite prevention strategies, prior deworming history, and other farm management relevant to parasite control will be administered to each owner. Blood samples will be analyzed for packed cell volume and total protein. Fecal samples will be submitted to the Animal Health Diagnostic Center for fecal egg counts (FEC). The fecal egg count reduction (FECR) will be calculated as the difference of FEC between the two samples for each animal. Farms will be defined as having suspected resistance to a drug class with any FECR of 80% to 95%; and having resistance with a FECR of < 80%. Our clinical experience suggests that most of the farms in our area are experiencing anthelmintic resistance to one or more drug classes. Detecting this resistance and associating the development of resistance with management techniques will allow us to better serve the local small ruminant populations and provide an evidence-based technique for other veterinarians to use to detect resistance in other parts of the country.