Seroprevalence and risk factors associated with within-flock transmission of Leptospira interrogans in transhumant farming systems in Mexico.

A number of recent reports emphasize the risk of zoonotic diseases and the high degree of prevalence of asymptomatic animals infected with Leptospira interrogans. This report sought to assess the prevalence of antibodies to certain serovars of L. interrogans, and to describe the association between seropositivity and risk factors associated with within-flock transmission in a mountainous region of Mexico. Overall seroprevalence to L. interrogans was 54·5% (95% confidence interval 48·3-60·7); the most frequent serovar was Icterohaemorrhagiae. The accumulation of placentas and fetuses at a site close to lambing paddocks can play a significant role as a risk factor for within-flock transmission of L. interrogans in transhumant farming systems in the municipality of Xalatlaco. The high prevalence of L. interrogans antibodies supports the hypothesis that natural foci of this zoonosis are present in sheep flocks in this area. These findings emphasize the need for planning and implementation of control programmes for ovine leptospirosis in Mexico and elsewhere.

[Identification and typing of Yersinia enterocolitica biotypes and serotypes isolated]. / Identificación y tipificación de biotipos y serotipos de Yersinia enterocolitica.

OBJECTIVE: To assess the presence of Yersinia enterocolitica in otherwise healthy pigs slaughtered for human consumption. METHODS: One hundred pharyngeal tonsils were sampled in a slaughterhouse in the state of Mexico. The minimum sample size (n=100) was calculated based on a preliminary sample of 20 cases, which had 20% positive cases. The collected tonsil samples were inoculated in Rappaport broth, and Salmonella-Shigella and McConkey media. The biotyping identification process was based on biochemical and serological tests using O:3, O:8 and O:9 antisera. RESULTS: Twenty-two isolates were obtained. Most were biotype 1 (8 cases of O:3 and 8 cases of O:9), but 6 cases could not be serotyped. None of the isolates were of O:8 group. CONCLUSIONS: This was the first time that Y. enterocolitica serotypes were isolated from pig tonsils in Mexico. Its importance rely on the fact that the isolated serotypes are the most commonly found in public health problems.

Sensitivity and specificity of an ELISA as a screening test for the diagnosis of Brucella ovis in sheep.

A hot saline extract of Brucella ovis strain REO 198 at a concentration of 5 micrograms/ml in phosphate buffer pH 7.2 was used to adsorb onto Maxisorb plates and incubated at 37 degrees C during 12 h; unadsorbed excess antigen was washed off thrice with phosphate buffer containing 0.5% Tween 20. As blocking agent 1% skim milk was used. The conjugate used was protein G bound to peroxidase diluted 1:100. Thirty three sheep sera from bacteriologically confirmed infected animals and 39 sheep sera from healthy animals from disease-free zones were used. Sera were diluted 1:200. ELISA's sensitivity was 97% and specificity 84%. The cut-off value was chosen for a high sensitivity (100%) despite some loss of specificity in order to diminish false negative results rendering thus a suitable screening test for sheep epididimitis caused by Brucella ovis.