Trypanotolerance

A trypanotolerant organism is one which is relatively less affected by trypanosome infestation.

By host

In livestock

Some breeds are known for their trypanotolerance. This is especially important in Africa where a few particular trypanosomes are major economic and agricultural pests.^[1][2][3][4]

Trypanotolerant livestock breeds

• N'Dama cattle^[2]
• West African Dwarf goats^[5]: 106
• West African Dwarf sheep (Djallonké)^[6]
• Cameroon sheep

Trypanotolerance of the N'Dama Cattle and West African Dwarf Sheep and Goats

Certain domestic ruminant breeds in sub-saharan Africa show remarkable resistance to the effects of African trypanosomiasis: they can tolerate the parasites's presence while controlling parasitaemia levels and, most importantly, do not show the severe anemia and production loss that are typical of infection in susceptible breeds.^[7]

The trypanotolerance trait is seen in N'Dama cattle, and it refers to the N'Dama cattle's ability to survive in areas with high tsetse fly endemicity, where other cattle breeds would frequently contract trypanosomiasis.^[1] In areas or locations of low to moderate tsetse fly challenge, typanotolerant N'Dama cattle show lower numbers of parasites in their blood, develop less severe anemia and have also been shown to be more productive.^[8]

An investigation to test the resistance of different small ruminant breeds (West African dwarf sheep and goats) to an artificial infection with T. congolense revealed that native sheep and goats had a higher natural resistance to the illness than exotic breeds, with exotic/indigenous crossbreeds falling somewhere in between.^[9] Despite persistent parasitaemia, clinical signs in trypanotolerant West African dwarf sheep and goats revealed a milder illness with lower mortality. ^[9] The significance of these trypanotolerant traits is highlighted when choosing breeds of sheep and goats for selection programs. Some literature claims that trypanotolerance in small ruminants (sheep and goats) should be viewed as resilience rather than resistance because it is less apparent than in cattle.^[10]

Trypanotolerance appears to include both non-immunological and immunological pathways and is most likely multifactorial.^[11] However, physiological and nutritional factors, concurrent diseases, the presence and absence of tsetse, and inter-current diseases all have an impact on the level of resistance displayed by typanotolerant breeds of cattle, sheep, and goats.^[7]

In addition to the above-listed criteria, studies have shown that the effective dose of the trypanosome parasite that these animals acquire following the bite of the tsetse fly is also a consideration. It only takes one fly bite to transmit the infection. ^[11] The quantity of trypanosomes injected into an animal's skin as a result of bites determines how severe the sickness will be; thus, trypanotolerance during natural exposure may be influenced by lower infective dosages.^[7] The finding that some cattle that are highly resistant in the field don't always retain that level of resistance after being artificially infected with a specific dose of the parasite may be supportive of this hypothesis.^[12]

History of genetic research

Trypanotolerance had previously been achieved through normal livestock breeding in cattle, but genetic analysis was becoming a serious option in the 1980s. The effort that would eventually bear fruit began with a conversation between Peter Brumby - then at the International Livestock Centre for Africa - and Morris Soller in 1985. This was followed by the opening of the shortlived International Trypanotolerance Center in the Gambia in 1987 with a seminar on the genome mapping project that would continue beyond the Center itself. The project was then actually completed by the ILRI - the successor to the ILCA - in 2003.^[13]

References

1. d'Ieteren, G.; Authie, E.; Wissocq, N.; Murray, M. (1998). "Trypanotolerance, an option for sustainable livestock production in areas at risk from trypanosomosis". Revue Scientifique et Technique de l'OIE. O.I.E (World Organisation for Animal Health). 17 (1): 154–175. doi:10.20506/rst.17.1.1088. ISSN 0253-1933. PMID 9638808. S2CID 1188831.
2. Kim, Soo-Jin; Ka, Sojeong; Ha, Jung-Woo; Kim, Jaemin; Yoo, DongAhn; Kim, Kwondo; Lee, Hak-Kyo; Lim, Dajeong; Cho, Seoae; Hanotte, Olivier; Mwai, Okeyo Ally; Dessie, Tadelle; Kemp, Stephen; Oh, Sung Jong; Kim, Heebal (2017-05-12). "Cattle genome-wide analysis reveals genetic signatures in trypanotolerant N'Dama". BMC Genomics. BioMed Central. 18 (1): 371. doi:10.1186/s12864-017-3742-2. ISSN 1471-2164. PMC 5427609. PMID 28499406.
3. "Trypanotolerant livestock in the context of trypanosomiasis intervention strategies". Food and Agriculture Organization of the United Nations. Retrieved 2021-02-20.
4. "Trypanotolerance in West African cattle". CIRAD (Centre de coopération internationale en recherche agronomique pour le développement). Retrieved 2021-02-20.
5. R. T. Wilson (1991). Small Ruminant Production and the Small Ruminant Genetic Resource in Tropical Africa. Rome: United Nations Food and Agriculture Organization. ISBN 9789251029985.
6. Mawuena, K. (1987). "Haut degré de tolérance à la trypanosomose des moutons et des chèvres de race naine Djallonké des régions Sud-guinéennes du Togo. Comparaison avec les bovins trypanotolérants" [High degree of tolerance to trypanosomiasis of dwarf Djallonké sheep and goats in the southern guinean area of Togo. Comparison with trypanosoma tolerant cattle]. Revue d'élevage et de médecine vétérinaire des pays tropicaux. 40 (1): 55–58. doi:10.19182/REMVT.8696 (inactive 31 January 2024). PMID 3444966. S2CID 86116225.{{cite journal}}: CS1 maint: DOI inactive as of January 2024 (link)
7. Authié, E. (1994). "Trypanosomiasis and trypanotolerance in cattle: A role for congopain?". Parasitology Today. 10 (9): 360–364. doi:10.1016/0169-4758(94)90252-6. ISSN 0169-4758. PMID 15275419. S2CID 42585897.
8. Kemp, S.; Teale, A. (1998). "Genetic Basis of Trypanotolerance in Cattle and Mice". Parasitology Today. Elsevier. 14 (11): 450–454. doi:10.1016/s0169-4758(98)01334-9. ISSN 0169-4758. PMID 17040846. S2CID 3253779.
9. • This review...
   •  • Murray, M.; Trail, J.; d'Ieteren, G. (1990). "Trypanotolerance in cattle and prospects for the control of trypanosomiasis by selective breeding". Revue Scientifique et Technique de l'OIE. O.I.E (World Organisation for Animal Health). 9 (2): 369–386. doi:10.20506/rst.9.2.506. ISSN 0253-1933. PMID 2132686. S2CID 2846382.
   • ...and this chapter...
   •  • Murray, Max; Morrison, W.; Whitelaw, D. (1982). Host Susceptibility to African Trypanosomiasis: Trypanotolerance. Advances in Parasitology. Vol. 21. Elsevier. pp. 1–68. doi:10.1016/s0065-308x(08)60274-2. ISBN 978-0-12-031721-9. ISSN 0065-308X. PMID 6762064. S2CID 38907545.
   • ...cite this study:
   •  • Griffin, L.; Allonby, E. (1979). "Trypanotolerance in breeds of sheep and goats with an experimental infection of Trypanosoma congolense". Veterinary Parasitology. 5 (2): 97–105. doi:10.1016/0304-4017(79)90001-3. ISSN 0304-4017. S2CID 83754228.
10. Geerts, Stanny; Osaer, Sabine; Goossens, Bart; Faye, Déthié (2009). "Trypanotolerance in small ruminants of sub-Saharan Africa". Trends in Parasitology. Cell Press. 25 (3): 132–138. doi:10.1016/j.pt.2008.12.004. PMID 19200783.
11. Duvallet, Gérard (2017). "Chapitre 1. Arthropodologie générale". Entomologie médicale et vétérinaire [Medical and Veterinary Entomology]. IRD Éditions. pp. 19–35. doi:10.4000/books.irdeditions.21962. ISBN 9782709923767.
12. Chow, Y. W.; Pietranico, R.; Mukerji, A. (1975-10-27). "Studies of oxygen binding energy to hemoglobin molecule". Biochemical and Biophysical Research Communications. 66 (4): 1424–1431. doi:10.1016/0006-291x(75)90518-5. ISSN 0006-291X. PMID 6.
13. Soller, Morris (2015-02-16). "If a Bull Were a Cow, How Much Milk Would He Give?". Annual Review of Animal Biosciences. Annual Reviews. 3 (1): 1–17. doi:10.1146/annurev-animal-022114-110751. ISSN 2165-8102. PMID 25493539. S2CID 46733451.