Parasitology



Genetic polymorphism of the β-tubulin gene of Onchocerca volvulus in ivermectin naïve patients from Cameroon, and its relationship with fertility of the worms


C. BOURGUINAT a1, S. D. S. PION a2, J. KAMGNO a3, J. GARDON a3a4, N. GARDON-WENDEL a3, B. O. L. DUKE a5, R. K. PRICHARD a1c1 and M. BOUSSINESQ a3a6
a1 Institute of Parasitology, McGill University, Sainte Anne-de-Bellevue, Quebec, Canada H9X3V9
a2 Department of Infectious Disease Epidemiology, Imperial College, Norfolk Place, London W2 1PG, UK
a3 Laboratoire d'Epidémiologie et de Santé publique, Centre Pasteur du Cameroun, BP 1274, Yaoundé, Cameroon
a4 Institut de Recherche pour le Développement, UR 24 Epidémiologie et Prévention, CP 9214 Obrajes, La Paz, Bolivia
a5 River Blindness Foundation, 2 Hillside, Lancaster LA1 1YH, UK
a6 Département Sociétés et Santé, Institut de Recherche pour le Développement, 213 rue La Fayette, 75480 Paris Cedex 10, France

Article author query
bourguinat c   [PubMed][Google Scholar] 
pion sd   [PubMed][Google Scholar] 
kamgno j   [PubMed][Google Scholar] 
gardon j   [PubMed][Google Scholar] 
gardon-wendel n   [PubMed][Google Scholar] 
duke bo   [PubMed][Google Scholar] 
prichard rk   [PubMed][Google Scholar] 
boussinesq m   [PubMed][Google Scholar] 

Abstract

Observations of low response of patients infected with Onchocerca volvulus to ivermectin suggest that the parasite may be under a selection process toward potential resistance. To limit the extension of this phenomenon, it is crucial to characterize the genes of O. volvulus that are involved. For this, O. volvulus adult worms collected before the introduction of ivermectin in an onchocerciasis endemic area of central Cameroon were genotyped for β-tubulin. To derive a baseline to investigate the selective pressure of ivermectin, we analysed (1) the frequency distribution of the β-tubulin alleles, and (2) the relationship between the different β-tubulin related genotypes and the fertility status of the female worms. The frequency of allele b of the β-tubulin gene was very low, as it was observed in West Africa. We observed a deficit of heterozygous female worms leading to Hardy Weinberg disequilibrium, which might be explained by a shorter life-span of these worms compared to the homozygous worms. Unexpectedly, our results also show that the heterozygous female worms were much less fertile than the homozygotes: more than two thirds of the homozygotes were fertile, whereas only 37% of the heterozygotes were fertile. These results will be further considered when analysing post-treatment data.

(Received June 21 2005)
(Revised August 3 2005)
(Accepted August 3 2005)
(October 3 2005)


Key Words: Onchocerca volvulus; β-tubulin; genetic polymorphism; fertility; Cameroon.

Correspondence:
c1 Institute of Parasitology, McGill University, Sainte Anne-de-Bellevue, Quebec, Canada H9X3V9. Tel: +514 398 7729. Fax: +514 398 7857. E-mail: roger.prichard@mcgill.ca


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