Jean-Charles Maillard

Protection of goats against heartwater acquired by immunisation with inactivated elementary bodies of Cowdria ruminantium.

In two experiments, four and five goats were vaccinated by giving two subcutaneous injections of a preparation of inactivated elementary bodies of Cowdria ruminantium (Gardel stock) mixed with Freunds adjuvant. All vaccinated animals together with four naive controls were challenged intravenously with 5 ml of supernatant of a culture of bovine endothelial cells infected with the same stock of Cowdria. All goats developed a high temperature. Two out of four, and four out of five vaccinated goats survived the challenge whereas all naive control animals died within 7-12 days. Vaccinated goats which died survived longer than the controls. No difference in antibody titres was observed between protected and non-protected vaccinated goats. Moreover, immune sera from surviving goats, whether heat inactivated or not, were unable to neutralize the infection of bovine endothelial cells by Cowdria in vitro. Mechanisms conferring protection on the immunized goats are unknown at the moment but the hypothesis that T-helper lymphocyte populations have been elicited seems to be likely. This method of immunization with dead organisms will help in the search for protective antigens against cowdriosis.

Molecular Immunogenetics in Susceptibility to Bovine Dermatophilosis

Abstract: To identify molecular genetic markers of resistance or susceptibility to dermatophilosis in cattle, we used a functional candidate gene approach to analyze the DNA polymorphisms of targeted genes encoding molecules implicated in known mechanisms of both nonspecific and specific immune responses existing in the pathogen/host interface mechanisms. The most significant results were obtained within the Major Histocompatibility Complex (MHC) where the BoLA‐DRB3 and DQB genes encode molecules involved in the antigen presentation to T cell receptors. A unique BoLA class II haplotype, made up of one DRB3 exon 2 allele and one DQB allele, highly correlates with the susceptibility character (P < 0.001). This haplotype marker of susceptibility was also found and validated in other bovine populations. A eugenic marker‐assisted selection was developed in the field by eliminating only the animals having this haplotype. The disease prevalence was thereby reduced from 0.76 to 0.02 over 5 years. A crossbreeding plan is in progress to study the genetic transmission of the genotypic and phenotypic characters of susceptibility to dermatophilosis. In conclusion, we discuss several hypotheses at the molecular and cellular levels to better define the exact role of the MHC molecules in disease control and to answer the question: How is MHC diversity selectively maintained by natural selection imposed by pathogens?

Genetic Resistance of Creole Goats to Cowdriosis in Guadeloupe Status in 1995

A genetic predisposition to resistance (R)/susceptibility (S) has been demonstrated for cowdriosis in certain goal lines. In order to identify genetic markers of R/S and to follow their transmission to the offspring, 4 groups of sires and dams were crossbred in 1991, 1992, and 1993: Rr, RS, SR, and SS. The offspring were challenged at the age of six months with subsequent challenge of the S parent. From 28 presumed S dams, 7 turned out R and from 2 presumed S sires, 1 was R and the other undefinable. The resistance rate was 76% for 21 RR kids and 45% for 20 RS kids. The R character seems to be better transmitted by dams than the S one. No difference was observed between R and S goats in terms of incubation period and body temperature level after challenge. There was no statistical effect found of sex, litter size, or birth mass on the R/S character; only a slight effect on daily mass gain was observed. Sperm has been collected from 4 S sires (died after challenge) and 5 R sires, and stored in liquid nitrogen in order to conceive additional SR and SS progeny. Several caprine leucocyte antigens seem to be genetic markers of R (Be 1, CLY) and of S (Be 9, Be 22, Be 23). Further powerful tools like microsatellites and probes defining other interesting loci possibly involved in disease pathogenesis are now at hand and will be included in future experiments.

Examples of Probable Host–Pathogen Co-adaptation/Co-evolution in Isolated Farmed Animal Populations in the Mountainous Regions of North Vietnam

In Vietnam, for a number of specific geographical and historical reasons, the mountainous areas have preserved an exceptional diversity of wild and domestic animal species of high socioeconomic interest. This endemic genetic diversity fosters a rapid response to environmental change in mostly isolated local communities and, in particular, fosters the constant adaptation of ecosystems common to humans and farmed and wild animal populations and pathogens. During a 2‐year study carried out in several mountainous regions of North Vietnam near the Chinese border, we surveyed 1697 breeders in 249 villages and gathered 5815 biological samples among the four main domesticated species of food animals: chickens, cattle, buffaloes, and goats. Serological analyses were carried out by ELISA on 726 sera in order to assess the prevalence of antibodies specific to two major diseases suspected to be present in the region: avian influenza (AI) and peste des petits ruminants (PPR). The results reported here reveal the presence of antibodies specific to AI, but not the H5N1 highly pathogenic strain, and the presence of antibodies specific to PPR, confirming that this disease, never previously described in Southeast Asia, is present in this region, with no mortality and little or no evidence of clinical cases. These are probably situations of co‐evolutive epidemiological equilibrium between pathogen populations, which may have lost their virulence, and animal populations that have acquired genetic resistances over generations, either naturally or through genetic introgression from related wild species better adapted to such pathogens. These results suggest the need for more research, both short‐term and, more globally, long‐term.

Animal biodiversity and emerging diseases prediction and prevention. Introduction.

This volume covers scientific topics from cellular pathogenesis to global pandemics to promote discussion and update researchers, academics, governmental and NGOs representatives, technicians, veterinarians and other professionals from the industry sector interested in tropical veterinary medicine.This volume of the Annals of the New York Academy of Sciences is a compilation of communications and posters presented during the 9th Biennial Conference of the International Society for Tropical Veterinary Medicine (STVM), held in Merida (Mexico) on June 17–22, 2007. The title of the conference, Animal Biodiversity and Emerging Diseases: Prediction and Prevention, logically followed the previous STVM biennial conference held in 2005 in Hanoi (Vietnam), Impact of Emerging Zoonotic Diseases on Animal Health. After identifying and trying to evaluate the importance of the zoonose impacts on animal health, we have observed that emerging and more probably re-emerging diseases will unfortunately remain for a long time, as these are a major problem of human and animal health all around the world in the context of environmental modifications from uncontrolled or excessive human activity. This constant threat on our planet obliges us to be vigilant and to imagine, first, the upstream setting up of reliable surveillance methods, international networks, and/or prediction and alert tools and, second, more downstream, the use of efficient prevention and action means.