Issue |
Genet. Sel. Evol.
Volume 35, Number Suppl. 1, 2003
Second International Symposium on Candidate Genes for Animal Health
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Page(s) | S193 - S200 | |
DOI | https://doi.org/10.1051/gse:2003027 |
DOI: 10.1051/gse:2003027
Selection assisted by a BoLA-DR/DQ haplotype against susceptibility to bovine dermatophilosis
Jean-Charles Maillarda, David Berthiera, Isabelle Chantala, Sophie Thevenonb, Issa Sidibéb, Frederic Stachurskib, Désiré Belemsagab, Hanta Razafindraïbéc and Jean-Michel Elsenda Cirad - Département d'Élevage et de Médecine Vétérinaire Tropicale, Animal Health Program, Montpellier, France
b Cirdes, Unité de Recherches Biologiques, Bobo-Dioulasso, Burkina Faso
c Fofifa - Département de Recherches Zootechniques et Vétérinaires, Antananarivo, Madagascar
d Inra - Station d'Amélioration Génétique Animale, Castanet-Tolosan, France
(Accepted 4 February 2003)
Abstract
Bovine dermatophilosis is a severe skin infection of tropical
ruminants inducing a severe loss in productivity and a 15% mortality
rate. This disease is caused by the actinomycete bacterium
Dermatophilus congolensis associated with the tick
Amblyomma variegatum. Currently there are no prospects for a
vaccine, and acaricide or antibiotic control is hampered by the
development of chemoresistance. Animal breeders have observed that
dermatophilosis susceptibility seems to be determined genetically, and
we previously identified a BoLA-DRB3-DQB class II haplotype
marker for high (R
2 = 0.96) susceptibility to the
disease. With this marker, we developed a successful eugenic selection
procedure for zebu Brahman cattle in Martinique (FWI). Over a period
of five years, a marked reduction in disease prevalence, from 0.76 to
0.02 was achieved, and this low level has been maintained over the
last two years. The selection procedure, based on a genetic marker
system targeting the highly polymorphic BoLA locus,
eliminates only those individuals which are at the highest risk of
contracting the disease. In the present work, we discuss the
properties of this system, including the "heterozygote advantage" and
the "frequency dependence" theories, and examine their involvement in
the biological mechanisms at the host/pathogen interface. We speculate
on the exact role of the MHC molecules in the control of the disease,
how the natural selection pressure imposed by the pathogens
selectively maintains MHC diversity, and how our results can be
practically applied for integrated control of dermatophilosis in
developing countries.
Key words: bovine dermatophilosis / BoLA / MHC / MAS / Brahman zebu
Correspondence and reprints: Jean-Charles Maillard
e-mail: maillard@cirad.fr
© INRA, EDP Sciences 2003