Animal trypanosomiasis explained

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 such as T. brucei. T. vivax causes nagana mainly in West Africa, although it has spread to South America.^[1] 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.^[2]

An interesting feature is the remarkable tolerance 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 B. indicus cattle such as the zebu.^[3]

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.^[4]

Transmission was successfully halted on Zanzibar by sterile insect technique (SIT) of the vector Glossina austeni.^[5]

Signs and symptoms

The incubation period ranges from four days to approximately eight 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.^[6]

Vectors

!Disease!Species affected!Trypanosoma agents!Distribution!Glossina vectors

Nagana – acute form	antelopecattlecamelshorses	T. brucei brucei	Africa	G. morsitansG. swynnertoni G. pallidipes G. palpalis G. tachinoides G. fuscipes
Nagana – chronic form	cattlecamelshorses	T. congolense	Africa	G. palpalisG. morsitans G. austeni G. swynnertoni G. pallidipes G. longipalpis G. tachinoides G. brevipalpis
Nagana – acute form	domestic pigscattlecamelshorses	T. simiae	Africa	G. palpalisG. fuscipes G. morsitans G. tachinoides G. longipalpis G. fusca G. tabaniformis G. brevipalpis G. vanhoofi G. austeni
Nagana – acute form	cattlecamelshorses	T. vivax	Africa	G. morsitansG. palpalis G. tachinoides G. swynnertoni G. pallidipes G. austeni G. vanhoofi G. longipalpis

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, 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.^[7]

Economic impact

Although the loss of direct livestock products (meat, milk, and blood) 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.^{[8] [9]}

Further reading

• Web site: A step closer to treating nagana . . 2017-01-17 . 2021-11-16.
• Cattand . Pierre . de Raadt . Pieter . 1991-12-01 . Laboratory Diagnosis of Trypanosomiasis . Clinics in Laboratory Medicine. Diagnosis of Important Parasitic Diseases. en . 11 . 4 . 899–908 . 10.1016/S0272-2712(18)30526-2 . 1802527 . 0272-2712.
• Sivajothi . S. . Rayulu . V. C. . Malakondaiah . P. . Sreenivasulu . D. . 2016-03-01 . Diagnosis of Trypanosoma evansi in bovines by indirect ELISA . Journal of Parasitic Diseases. en . 40 . 1 . 141–144 . 10.1007/s12639-014-0465-z . 0975-0703 . 4815840 . 27065614.
• Desquesnes . Marc . Gonzatti . Marisa . Sazmand . Alireza . Thévenon . Sophie . Bossard . Géraldine . Boulangé . Alain . Gimonneau . Geoffrey . Truc . Philippe . Herder . Stéphane . Ravel . Sophie . Sereno . Denis . Jamonneau . Vincent . Jittapalapong . Sathaporn . Jacquiet . Philippe . Solano . Philippe . 2022-02-19 . A review on the diagnosis of animal trypanosomoses . Parasites & Vectors. 15 . 1 . 64 . 10.1186/s13071-022-05190-1 . 1756-3305 . 8858479 . 35183235 . free .
• Book: Uilenberg, G.. 1998. African animal trypanosomes . A field guide for the diagnosis, treatment and prevention of African animal trypanosomosis . Food and Agriculture Organization of the United Nations . https://www.fao.org/3/X0413E/X0413E02.htm . 2023-02-03 . 92-5-104238-1 .
• Mitashi . Patrick . Hasker . Epco . Lejon . Veerle . Kande . Victor . Muyembe . Jean-Jacques . Lutumba . Pascal . Boelaert . Marleen . 2012-11-29 . Human African Trypanosomiasis Diagnosis in First-Line Health Services of Endemic Countries, a Systematic Review. PLOS Neglected Tropical Diseases. en . 6 . 11 . e1919 . 10.1371/journal.pntd.0001919 . 1935-2735 . 3510092 . 23209860 . free .

Web site: Reference Laboratories . 2023-02-03 . OIE (World Organisation for Animal Health/WOAH). en-GB.

• WHO fact sheet on Trypanosomiasis

Notes and References

1. Batista . Jael S . Rodrigues . Carla MF . García . Herakles A . Bezerra . Francisco SB . Olinda . Robério G . Teixeira . Marta MG . Soto-Blanco . Benito . Association of Trypanosoma vivax in extracellular sites with central nervous system lesions and changes in cerebrospinal fluid in experimentally infected goats . Veterinary Research. 42 . 1 . 63 . May 2011 . 21569364 . 3105954 . 10.1186/1297-9716-42-63 . free .
2. Web site: Human African trypanosomiasis (sleeping sickness) . Fact sheet . 10 January 2022 . World Health Organization (WHO).
3. Courtin D, Berthier D, Thevenon S, Dayo GK, Garcia A, Bucheton B . Host genetics in African trypanosomiasis . . 8 . 3 . 229–238 . May 2008 . 18394971 . 10.1016/j.meegid.2008.02.007 . 2008InfGE...8..229C .
4. Web site: African Animal Trypanosomiasis . October 2018 . . Institute for Cooperation in Animal Biologics. . OIE Collaborating Centre for Diagnosis of Animal Disease and Vaccine Evaluation in the Americas . OIE Collaborating Centre for Day-One Veterinary Competencies and Continuing Education . United States Department of Agriculture.
5. 2020. 1. G.. C.. M.. Y.. S.. E.. Dimopoulos. Tikhe. Simoes. Dong. Dong. Caragata. 74. 455–475. Annual Reviews. Annual Review of Microbiology. 0066-4227. 10.1146/annurev-micro-011320-025557. Prospects and Pitfalls: Next-Generation Tools to Control Mosquito-Transmitted Disease. 32905752. 221625690. free.
6. Web site: Finelle. P.. African animal trypanosomiasis. Food and Agriculture Organization of the United Nations (FAO). 19 April 2017.
7. Saini . Rajinder K. . Orindi . Benedict O. . Mbahin . Norber . Andoke . John A. . Muasa . Peter N. . Mbuvi . David M. . Muya . Caroline M. . Pickett . John A. . Borgemeister . Christian W. . 2017-10-17 . Solano . Philippe . Protecting cows in small holder farms in East Africa from tsetse flies by mimicking the odor profile of a non-host bovid. PLOS Neglected Tropical Diseases. en . 11 . 10 . e0005977 . 10.1371/journal.pntd.0005977 . 1935-2735 . 5659797 . 29040267 . free .
8. Book: Swallow, Brent M. . Animal Production and Health Division, International Livestock Research Institute, Nairobi, Kenya . Impacts of trypanosomiasis on African agriculture . Food and Agriculture Organization of the United Nations . . 2000 . 92-5-104413-9 . 45185699 . vii+52 . 10.1.1.631.6490 . 1020-7163 . PAAT Technical and Scientific Series. AGRIS id XF2001396009. CABD 20003010139.
9. Giordani . Federica . Morrison . Liam J. . Rowan . Timothy G. . De Koning . Harry P. . Barrett . Michael P. . The animal trypanosomiases and their chemotherapy: a review . . Cambridge University Press (CUP) . 143 . 14 . 2016-10-10 . 0031-1820 . 10.1017/s0031182016001268 . 1862–1889. 27719692 . 5142301 .