Correlation of carbohydrate larval antigen (CarLA®) antibody response with parasitism in Ontario sheep

Abstract

Gastrointestinal nematode parasites (GINs) are a significant cause of morbidity, mortality and loss of productivity on North American sheep farms. In light of the rising prevalence of anthelmintic resistance, selection of animals with a superior immune response to GINs has received considerable attention. In New Zealand, measurement of salivary antibody to a carbohydrate larval antigen (CarLA®, AgResearch Inc.) has been used successfully to identify sheep with superior immunity. However, climate and GIN epidemiology in Ontario are different from New Zealand, and sheep are generally not exposed to GINs for several months during housing over winter. To date, CarLA® has not been evaluated in North America. The purpose of this study was to determine whether Car LA® correlates with parasite burden under temperate grazing conditions in Ontario.