Breed differences in resistance to a tropical protozoan parasite, Theileria annulata

The tick-borne protozoan parasite, Theileria annulata, causes an overwhelming infection in naive Bos taurus European cattle (such as Holsteins). However we show that a group of an indigenous Bos indicus breed, Sahiwal, are relatively more resistant to this parasite than a group of Holstein cattle. All the Sahiwals survived an experimental challenge with T. annulata whereas the Holsteins did not. Of the clinical, haernatological and parasitological parameters measured, there were significantly different responses in terms of temperature, size of lymph nodes, macroschizont and piroplasm counts. Levels of acute phase proteins were also significantly lower in the Sahiwal group than the Holstein group. Acute phase proteins are produced in the liver in response to proinflammatory cytokines such as IL-6 and TNF[alpha]. In vivo, the parasite enters bovine macrophages within draining lymph nodes and differentiates into the intracellular macroschizont stage. It is this stage that is mainly responsible for the pathology seen in susceptible breeds. High levels of monokine mRNA (including TNF[alpha] and IL-6) are expressed in infected Holstein macrophages, and the acute phase response indicates that these cytokines play an important role in pathogenesis. The ability of Sahiwals to limit infection with the parasite suggests that macrophages from this breed are able to regulate pro-inflammatory cytokine production and the host overcomes the parasite infection. We have found that infected macrophages from Sahiwals and Holsteins have differential expression of a number of important immune molecules. We are now planning a global approach by microarray analysis to detect gene expression differences following infection. Potentially differences in gene expression in macrophages may pinpoint the mechanisms of resistance to T. annulata. (Texte intégral)

Bibliographic Details

Main Authors:	Glass, E.J., Mc Guire, K., Springbett, A., Black, A., Craigmile, S., Eckersall, P.D., Preston, P.M., Brown, C.G.D.
Format:	conference_item biblioteca
Language:	eng
Published:	CIRAD
Subjects:	L10 - Génétique et amélioration des animaux, Theileria annulata, parasite, mouton, résistance aux maladies, http://aims.fao.org/aos/agrovoc/c_31225, http://aims.fao.org/aos/agrovoc/c_5574, http://aims.fao.org/aos/agrovoc/c_8369, http://aims.fao.org/aos/agrovoc/c_2328,
Online Access:	http://agritrop.cirad.fr/512059/
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