People in tropical countries fear diseases called sleeping sickness, and other names, caused by tiny parasites called trypanosomes (Trypanosoma spp.) also known as tryps. Now there’s new science suggesting a way to reduce Animal African Trypanosomiasis in cattle (Bos primigenius) by selective breeding.
In sub-Saharan Africa, tryps which kill cattle are hugely important to people’s livelihoods and, therefore, to development away from poverty. African tryps are carried by tsetse flies (Glossina spp.) You can scroll down for maps. The flies don’t get ill from the tryps, but they carry them between people and between cattle. That is, these insects are disease vectors.
One of the most promising ways to reduce tryp disease is to breed cattle which resist it. Where tryps are endemic (always present) it’s no surprise that some of the local cattle have that disease resistance. For example West African dwarf cattle, the Baoulé type (humpless shorthorns) don’t get so ill from tryp disease as other cattle do.
Baoulé cattle are often crossbred with the Zebu type (humped longhorns) which were imported from India many years ago. These cattle cope well with tropical climates. Farmers, including pastoralists, like them because they produce more meat and milk than the Baoulé type. But when bitten by tsetse flies, Zebus often get ill from Animal African Trypanosomiasis.
Now here’s some new science about these African cattle. At the University of Veterinary Medicine, Vienna, Katja Silbermayr has developed a blood test to show which kinds of tryps a cow or bull has. She tested 350 cattle and says, ‘Baoulés are infected less often than Zebus and seem able to tolerate higher amounts of the parasite. We only studied healthy animals and Zebus with such high parasite levels would have been too ill to be included in our study.’
Therefore, says Dr Silbermayr, ‘We plan to examine the current extent of mixing between Baoulés and Zebus and hope that in future it will be possible to determine the optimal degree of mixing to offer protection against trypanosomes.’ I wonder whether she’ll get money from the Gates Foundation.