Selection assisted by a BoLA-DR/DQ haplotype against susceptibility to bovine dermatophilosis.
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 (R2= 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.
Maillard
Jean-Charles
JC
Cirad - Département d'Elevage et de Médecine Vétérinaire Tropicale, Animal Health Program, Montpellier, France. maillard@cirad.fr
Berthier
David
D
Chantal
Isabelle
I
Thevenon
Sophie
S
Sidibé
Issa
I
Stachurski
Frederic
F
Belemsaga
Désiré
D
Razafindraïbé
Hanta
H
Elsen
Jean-Michel
JM
D000193:Actinomycetales Infections / Q000235:genetics / Q000276:immunology / Q000662:veterinary*; D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000235:genetics* / Q000276:immunology; D017931:DNA Primers / Q000235:genetics; D004198:Disease Susceptibility / Q000662:veterinary; D005053:Eugenics; D006239:Haplotypes; D006579:Heterozygote; D000949:Histocompatibility Antigens Class II / Q000235:genetics*; D012641:Selection, Genetic
C423282:BoLA-DRB3 antigen; D017931:DNA Primers; D000949:Histocompatibility Antigens Class II