Figure 1

Life cycle representing gastrointestinal nematodes (order Strongylida) of small ruminants; adapted from[12]. First-, second- and third-stage larvae (L1, L2 and L3, respectively) are free-living in the environment. The fourth larval (L4) and adult stages (dioecious) are parasitic in the gastrointestinal tract of the host. Disease is caused by the L4 and/or adult stages and depends on factors including: species of nematode infecting the host; intensity of the infection; species, age and immunological/health status of the host; host response against the parasite; environment and management aspects [10, 13].