Vol. 11, Special Issue 10 (2022)

Author(s):
R Selvam

Abstract:
Gastrointestinal nematode infection is a major constraint to the sheep farming and cause production losses, increased costs of management and treatment, and mortality in severe cases. The use of conventional disease control methods viz. chemotherapeutic agents, antibiotics, deworming and vaccination protocols, have most frequently had negative consequences like drug-resistant strains, increased production cost, etc., In alternative to that, the breeding programs with the goal of enhancing host resistance to diseases may help to lessen the problems permanently. In this article, current knowledge on the host immune response and markers associated with resistance to gastrointestinal nematodes infection in sheep is reviewed. The genetic variations within and between sheep breeds against the gastrointestinal nematodes have been reported where some individuals/breed are more resistant to the infection. Attempts have been made to identify susceptible and resistant animals based on indicator traits. Candidate genes are genes with known biological function that directly or indirectly regulating the developing processes of the investigated disease. The genes have been shown to be related to disease and more likely to find associations with the target disease traits. The basic idea is to analyze the mutations in susceptible / resistant animals, or different breeds with different susceptibility to a infection. Alleles based on the mutations find in these genes may be useful markers for disease resistance breeding. The identification of the genetic markers will enable the use of marker assisted selection to increase the accuracy of selection in breeding programmes. This knowledge may lead to a better understanding of the mechanisms of susceptibility and resistance of hosts to gastrointestinal nematodes. Understanding the genetic and molecular basis of disease resistance also has many advantages and applications such as the development of novel genetic markers for inclusion in genetic improvement programmes.