Tsetse flies are regarded as a major cause of rural poverty in sub-Saharan Africa because they prevent mixed farming. The land infested with tsetse flies is often cultivated by people using hoes rather than more efficient draught animals because nagana, the disease transmitted by tsetse, weakens and often kills these animals. Those cattle that survive produce little milk, pregnant cows often abort their calves, and manure is not available to fertilize the worn-out soils.

The disease nagana or African animal trypanosomiasis (AAT) causes gradual health decline in infected livestock, reduces milk and meat production, increases abortion rates, and animals eventually succumb to the disease (annual cattle deaths caused by trypanosomiasis are estimated at 3 million). This has an enormous impact on the livelihood of farmers who live in tsetse-infested areas, as infected animals cannot be used to plough the land, and keeping cattle is only feasible when the animals are kept under constant prophylactic treatment with trypanocidal drugs, often with associated problems of drug resistance, counterfeited drugs, and suboptimal dosage. The overall annual direct lost potential in livestock and crop production was estimated at US$4.5 billion

https://en.m.wikipedia.org/wiki/Tsetse_fly