A tse-tse fly, photographed using a scanning electron microscope. The picture shows the large compound eyes (red), comprised of a mosaic of many simple elements, the ommatidia. "Tse-tse fly" is a generic name for all species of the genus Glossinia, found in tropical Africa. They are a major cause of poverty in sub-Saharan Africa, due to their being a vector for the disease nagana, or African animal trypanosomiasis. In areas of the fly's prevalence, cattle cannot be used for draught work, milk and meat production, or as source of manure for soils. Humans are also subject to infection - the disease known as sleeping sickness. The causal parasites are protozoans of the genus Trypanosoma. They are introduced by a bite from an infected fly, and migrate through the blood to the brain, causing lethargy, and eventual death.