[1] In areas or locations of low to moderate tsetse fly challenge, typanotolerant N'Dama cattle show lower numbers of parasites in their blood, develop less severe anemia and have also been shown to be more productive.
[9] Despite persistent parasitaemia, clinical signs in trypanotolerant West African dwarf sheep and goats revealed a milder illness with lower mortality.
[7] In addition to the above-listed criteria, studies have shown that the effective dose of the trypanosome parasite that these animals acquire following the bite of the tsetse fly is also a consideration.
[11] The quantity of trypanosomes injected into an animal's skin as a result of bites determines how severe the sickness will be; thus, trypanotolerance during natural exposure may be influenced by lower infective dosages.
The effort that would eventually bear fruit began with a conversation between Peter Brumby - then at the International Livestock Centre for Africa - and Morris Soller in 1985.