Nagana

The disease is caused by trypanosomes of several species in the genus Trypanosoma. The trypanosomes infect the blood of the vertebrate host, causing fever, weakness, and lethargy which lead to weight loss and anemia; in some animals the disease is fatal unless treated.The trypanosomes are transmitted by tsetse flies.
An interesting feature is the remarkable resistance to nagana pathology shown by some breeds of cattle, notably the N'Dama - a West African Bos taurus breed. This contrasts with the susceptibility shown by East African Bos indicus cattle such as the zebu. Most wild African animals are also resistant.
This disease is the non-human animal counterpart of Human African trypanosomiasis, also known as sleeping sickness.
Nagana and history
The nagana pest disease has had a significant effect on African history, by keeping horses and camels (and thus cavalry and mounted knights and mounted messengers) out of much of Africa. One main effect was in stopping the southward advance of Islam at the northern limit of tsetse fly country.It also Prevented the colonization of much of Africa for a long time. Another effect is that it is probable that the southward spread of the Bantu/Nguni peoples had to wait until their cattle evolved to become resistant to nagana.
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