How does farmer connectivity influence livestock genetic structure? A case-study in a Vietnamese goat population.

Assessing how genes flow across populations is a key component of conservation genetics. Gene flow in a natural population depends on ecological traits and the local environment, whereas for a livestock population, gene flow is driven by human activities. Spatial organization, relationships between farmers and their husbandry practices will define the farmer's network and so determine farmer connectivity. It is thus assumed that farmer connectivity will affect the genetic structure of their livestock. To test this hypothesis, goats reared by four different ethnic groups in a Vietnamese province were genotyped using 16 microsatellites. A Bayesian approach and spatial multivariate analysis (spatial principal component analysis, sPCA) were used to identify subpopulations and spatial organization. Ethnic group frequencies, husbandry practices and altitude were used to create cost maps that were implemented in a least-cost path approach. Genetic diversity in the Vietnamese goat population was low (0.508) compared to other local Asian breeds. Using a Bayesian approach, three clusters were identified. sPCA confirmed these three clusters and also that the genetic structure showed a significant spatial pattern. The least-cost path analysis showed that genetic differentiation was significantly correlated (0.131-0.207) to ethnic frequencies and husbandry practices. In brief, the spatial pattern observed in the goat population was the result of complex gene flow governed by the spatial distribution of ethnic groups, ethnicity and husbandry practices. In this study, we clearly linked the livestock genetic pattern to farmer connectivity and showed the importance of taking into account spatial information in genetic studies.

[Use of the B19 strain in the prevention of bovine brucellosis in northern Cameroon. Study of effect of the dose on seroconversion rate and duration in female zebu]. / Utilisation de la souche B19 dans la prophylaxie médicale de la brucellose bovine au Nord-Cameroun. Etude de l'effet de la dose sur le taux et la durée de séroconversion chez des femelles zébus.

Four herds of zebus from northern Cameroon totalling 136 animals were vaccinated subcutaneously with the following doses of Brucella abortus strain 19: 5 x 10(9) colony-forming units (CFU), 10(9) CFU, 5 x 10(8) CFU and 10(7) CFU. Twenty-eight days after vaccination, the following seroconversion rates were observed respectively: 97.4, 96.2 84.2 and 73.3%. Of the 52 animals which could be tested subsequently including 39 over one year old on the vaccination day, only one showed antibodies 6 months after vaccination. The cost price of the strain 19 vaccine produced at the Boklé National Veterinary Laboratory was estimated to be 65 F CFA at the 10(9) CFU dose and 1,740 F CFA at the 5 x 10(10) CFU dose usually recommended. The use of the Buck 19 strain in the medical prophylaxis of bovine brucellosis in northern Cameroon is discussed.

[Main infectious agents involved in the etiology of lung diseases of small ruminants in northern Cameroon]. / Etude des principaux agents infectieux intervenant dans l'étiologie des pneumopathies des petits ruminants au Nord-Cameroun.

Between 1990 and 1992, 91 necropsies of small ruminants affected with pulmonary illness led to the isolation of the following strains of Mycoplasma (M.): M. mycoides subsp. mycoides LC, M. ovipneumoniae, M. agalactiae, M. sp. type D2 and M. arginini. Eleven Pasteurella multocida strains (serotypes A1, A3, A5, A7 and D2) and 11 Pasteurella haemolytica strains (serotypes 1, 2, 3, 6, 7, 8 and 9) were isolated. Corynebacterium pseudotuberculosis, Actinomyces pyogenes, Staphylococcus sp., Streptococcus sp., Bacillus sp. and Mycobacterium sp. were also isolated. Thirty-two antibiograms were performed on Pasteurella, Corynebacterium pseudotuberculosis and Actinomyces pyogenes strains. Eighty eight p. cent were sensitive to penicillin G and oxytetracycline, and 84% to chloramphenicol; 50% were not sensitive to spiramycin and 47% to streptomycin. One Capripoxvirus strain was isolated on sheep. Pest of small ruminants (PPR) virus was detected by immunocapture ELISA test performed on some lung samples. Two serological surveys, one for contagious caprine pleuropneumonia (898 goats), between 1991 and 1993, and one for PPR (902 sheep and goats) in 1993, were conducted in the North and Far North provinces. No antibody against contagious caprine pleuropneumonia was detected. Among the animals in the sample, PPR prevalence was 64 +/- 7% in the Far North province and 14 +/- 3% in the North province. Concerning control measures, a vaccination campaign against small ruminant pasteurellosis appears to be hardly feasible because of the antigenic diversity of the isolated Pasteurella strains. PPR is endemic especially in the Far North province. The efficiency of a vaccination campaign against PPR must be estimated with a field survey.

[Epidemiology of digestive parasitic diseases of young cattle in northern Cameroon]. / Epidémiologie des parasitoses digestives des jeunes bovins dans le Nord-Cameroun.

Studies of gastro-intestinal parasites of zebu calves were carried out in traditional herds in Northern Cameroon through monthly faecal analysis in 17 herds for a period of two years. Toxocarosis appeared to be the most important parasitic infection in the North province where its prevalence reached 58% in calves aged 0-6 months; 60% of the infested calves passed large numbers of eggs at least once. Samples revealing high egg counts were more frequent in the dry season. Deworming calves aged one month with a cheap anthelmintic against Toxocara is likely to be economically profitable in the North. Seventy-five and a half per cent of the calves 0-12 months old were infested with Strongyloides; high counts of Strongyloides eggs were registered at least once for 31% of these calves. As for toxocarosis, calves seemed to be more often and more heavily infested with Strongyloides in the North than in the Far North province. Strongyloidosis was apparently of low clinical importance, with the rare clinical manifestations accompanied by toxocarosis. The importance of digestive tract strongylosis was difficult to evaluate. Every steer was affected at one stage of its life in a similar manner in the two provinces; 6.8% of samples showed high egg counts and 35% of the steers aged over six months passed large numbers of eggs at least once. These results did not permit a priori recommendation of a systematic deworming programme against strongyles; instead, several less intensive deworming programmes have to be tested in order to determine their economic profitability. Coccidia were found in 77.4% of calves aged 0-12 months, with heavier and more frequent infections in the North. However, infections of high intensity were generally rare. Trichuris, Moniezia, Fasciola and paramphistomes were rarely found. Concerning nematodosis, curative treatments and cost-profit studies of deworming programmes should be aimed at toxocarosis in calves aged 0-3 months in the North, and strongylosis in steers aged 6-12 months, in both provinces.