A Steer with bovine trypanosomiasis Wellcome L0011039

Animal trypanosomiasis, also known as nagana and nagana pest, or sleeping sickness, is a disease of vertebrates. The disease is caused by trypanosomes of several species in the genus ''

Trypanosoma ''Trypanosoma'' is a genus of kinetoplastids (class Trypanosomatidae), a monophyletic group of unicellular parasitic flagellate protozoa. Trypanosoma is part of the phylum Sarcomastigophora. The name is derived from the Greek ''trypano-'' ( ...

'' such as ''

Trypanosoma brucei ''Trypanosoma brucei'' is a species of parasitic kinetoplastid belonging to the genus '' Trypanosoma'' that is present in sub-Saharan Africa. Unlike other protozoan parasites that normally infect blood and tissue cells, it is exclusively extrace ...

''. ''

Trypanosoma vivax ''Trypanosoma vivax'' is a parasite species in the genus ''Trypanosoma''. It causes the disease nagana, affecting cattle or wild mammals. It is mainly occurs in West Africa, although it has spread to South America. Range Historically restricted ...

'' causes nagana mainly in West Africa, although it has spread to South America. 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 Tsetse ( , or ) (sometimes spelled tzetze; also known as tik-tik flies), are large, biting flies that inhabit much of tropical Africa. Tsetse flies include all the species in the genus ''Glossina'', which are placed in their own family, Glos ...

flies. An interesting feature is the remarkable tolerance to nagana pathology shown by some breeds of cattle, notably the

N'Dama N'Dama is a breed of cattle from West Africa. Other names for them include Boenca or Boyenca (Guinea-Bissau), Fouta Jallon, ''Djallonké'' or ''Djallonké cattle'', Fouta Longhorn, Fouta Malinke, Futa, Malinke, Mandingo (Liberia), and N'Dama Peti ...

– a West African '' Bos taurus'' breed. This contrasts with the susceptibility shown by East African '' Bos indicus'' cattle such as the

zebu The zebu (; ''Bos indicus'' or ''Bos taurus indicus''), sometimes known in the plural as indicine cattle or humped cattle, is a species or subspecies of domestic cattle originating in the Indian sub-continent. Zebu are characterised by a fatty h ...

Transmission

Most trypanosomes develop in tsetse flies (''Glossina'' spp.), its biological vector, in about one to a few weeks. When an infected tsetse fly bites an animal, the parasites are transmitted through its saliva. It can also be spread by fomites such as surgical instruments, needles, and syringes. The most important vectors are thought to be horseflies (''Tabanidae'' spp.) and stable flies (''Stomoxys'' spp.). The immune response of animals may be unable to eliminate trypanosomes completely, and the host may become an inapparent carrier. These inapparent infections can be reactivated if the animal is stressed. Transplacental transmission can also occur.

Signs and symptoms

The incubation period ranges from 4 days to approximately 8 weeks. The infection leads to significant weight loss and anemia. Various symptoms are observed, including fever, oedema, adenitis, dermatitis and nervous disorders. The disease cannot be diagnosed with certainty except physically detecting parasites by blood microscopic examination or various serological reactions.

Vectors

Control measures

If the outbreak is detected early, the organism can be destroyed by quarantines, movement controls, and the euthanasia of infected animals. Tsetse fly populations can be reduced or eliminated by traps, insecticides, and by treating infected animals with antiparasitic drugs. The tsetse habitat can be destroyed by alteration of vegetation. Some drugs can prevent trypanosomiasis, and are called prophylactic drugs. These are very effective in protecting animals during the times they are exposed to diseases. Historically, these drugs were not used properly, leading to some resistance.

Waterbuck The waterbuck (''Kobus ellipsiprymnus'') is a large antelope found widely in sub-Saharan Africa. It is placed in the genus '' Kobus'' of the family Bovidae. It was first described by Irish naturalist William Ogilby in 1833. Its 13 subspecies ar ...

, among other animals, produces chemical odours that repel tsetse flies. This has led to the development of collars that store and gradually release these chemicals, reducing tsetse attack and thus trypanosomiasis incidence for cattle wearing these collars.

Economic impact

Although the loss of direct livestock products ( meat,

milk Milk is a white liquid food produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals (including breastfed human infants) before they are able to digest solid food. Immune factors and immune-modula ...

, and

blood Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the cir ...

) is problematic, the greatest impact of livestock trypanosomiasis is the loss of crop productivity due to loss of the animals' draught power in the field.

AGRIS AGRIS (International System for Agricultural Science and Technology) is a global public domain database with more than 12 million structured bibliographical records on agricultural science and technology. It became operational in 1975 and the data ...

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Transmission

Signs and symptoms

Vectors

Control measures

Economic impact

References

Further reading