Influence of lamb resistance or susceptibility on morphometric parameters of Haemonchus contortus.

• Grant number: 25/21702-0
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: January 01, 2026
• End date: December 31, 2026
• Field of knowledge: Biological Sciences - Parasitology - Helminthology of Parasites
• Principal Investigator: César Cristiano Bassetto
• Grantee: Maria Isabel de Almeida Bustos
• Host Institution: Instituto de Biociências (IBB). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil

Abstract

The ovine helminthiasis caused by Haemonchus contortus is one of the main challenges in sustainable sheep production, leading to economic losses due to anemia, reduced weight gain, decreased production, and even animal mortality. The control of this parasite has become increasingly difficult due to the development of multiple resistance to anthelmintics, which reinforces the need for alternative strategies such as integrated management and genetic selection of resistant animals. This project aims to evaluate the influence of lamb resistance or susceptibility profiles to H. contortus infection on developmental, morphometric, and reproductive parameters of the parasite. Samples of abomasal content from 35 artificially infected lambs, previously collected, frozen, and stored, will be used. Aliquots corresponding to 10% of the abomasal content will be washed through sieves for recovery and subsequent counting and identification of the different developmental stages, which will be classified as early L4, late L4 (male and female), early L5 (male and female), and adults (male and female). Ten adult females and ten adult males per sample will be selected to measure body length and, in females, intrauterine egg counts, while in males, spicule length will be measured. To confirm that the evaluated specimens belong to the species H. contortus, DNA will be extracted from adults, followed by PCR with species-specific primers. The data obtained will be subjected to statistical analyses comparing resistant and susceptible lambs. It is expected that this study will contribute to advancing knowledge on host-parasite interactions and that the morphometric and reproductive characteristics of the parasite will support the development of more effective sanitary management and genetic selection strategies, reducing the use of anthelmintics and promoting the sustainability of sheep production. (AU)