STATUS OF ANTI-HELMINTIC RESISTANCE IN HORSE FARMS FROM SÃO PAULO STATE

• Grant number: 25/04636-4
• Support Opportunities: Regular Research Grants
• Start date: September 01, 2025
• End date: August 31, 2027
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Preventive Veterinary Medicine
• Principal Investigator: José Gabriel Gonçalves Lins
• Grantee: José Gabriel Gonçalves Lins
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil
• Associated researchers: Marcos Jun Watanabe ; WANDERSON ADRIANO BISCOLA PEREIRA

Abstract

Horses are animals of significant cultural and historical value in modern society, and they play a crucial role in livestock production due to their versatility in agricultural activities, transportation, and draught. Additionally, in the equine industry, they are essential for leisure activities, equine therapy, and in equestrian competitions involving cultural and regional sports. The equine sector generates an annual revenue exceeding 16 billion Brazilian reais and employs more than three million people in Brazil, with the state of São Paulo presenting the 10th largest herd in the country. Like other animal species, horses are susceptible to parasitic infections caused by gastrointestinal nematodes (GIN), which are one of the greatest threats to the welfare and health of these animals. The control of parasitic diseases in equines relies on the administration of anthelminthic drugs. However, the intensive and indiscriminate use of these drugs over the past decades has led to the emergence of parasitic populations resistant to the anthelmintic drugs available in the market. In this context, the objective of this research is to evaluate the efficacy of anthelminthic drugs against GIN in equines from the state of São Paulo. Animals of both sexes and of different ages (foals, young, and adults) naturally infected by GIN, which have been treated with anthelminthics for more than three months and present fecal egg counts (FEC) ¿ 200 eggs per gram of feces, will be included. Anthelminthics from the three most used pharmacological classes for equine treatment (benzimidazoles, pyrimidines, and macrocyclic lactones) will be administered to create treated groups for each property assessed. Egg count reduction tests (RCOF) will be performed for each anthelminthic molecule used in each evaluated production unit. Additionally, the minimum egg reappearance periods in the feces of the evaluated animals will be determined. Faecal cultures will be conducted to obtain and identify infective larvae. All trials and analyses, including animal selection and distribution into experimental groups, will be conducted following the guidelines of the World Association for the Advancement of Veterinary Parasitology (WAAVP). Structured questionnaires will be applied to the owners of the animals included in the study to determine epidemiological factors associated with the diagnosis of parasitic infections, animal health, and the adopted sanitary and nutritional management practices, as well as the efficacy of the anthelminthics administered. DNA sequencing of nemabiome (ribosomal DNA or metabarcoding) will be performed to assess the species composition of GIN involved in anti-helminthic resistance cases identified in equine herds. (AU)