Trypanotolerant

Trypanotolerant refers to hosts that can endure infection with Trypanosoma parasites, particularly those transmitted by tsetse flies, with little or no severe disease and without a complete loss of productivity. In contrast to resistance, which reduces parasite numbers, tolerance means infected individuals may carry parasites and yet maintain health, growth, and reproduction.

In livestock, trypanotolerance has been most documented in West African cattle breeds, especially the N'Dama and Muturu cattle (Bos taurus). These animals often exhibit lower parasitemia, milder anemia, and better weight gain and fertility under trypanosome challenge compared with susceptible breeds. The trait is generally considered polygenic and influenced by environmental factors such as nutrition, climate, and management.

Mechanisms underlying trypanotolerance are complex and involve both innate and adaptive immune responses. Some cattle show more effective control of parasite replication and a modulated inflammatory response, allowing them to tolerate infection with less tissue damage. Because tolerance does not prevent infection, trypanotolerant animals can still serve as reservoirs for parasites, underscoring the need for integrated disease management alongside breeding programs.

Applications of trypanotolerance include enhancing livestock production in tsetse-infested areas and reducing reliance on chemoprophylaxis. Breeding programs aim to combine tolerance with other desirable traits, improving disease resilience in smallholder farming systems.

See also: Trypanosoma, trypanosomiasis, tsetse fly, host–pathogen interactions.