Molecular Relationship between Strains of M. bovis from Mexico and Those from Countries with Free Trade of Cattle with Mexico.

The purpose of this study was to identify relationships between spoligotypes of M. bovis from cattle in Mexico and those reported in countries with free trade of cattle with Mexico: Australia, Canada, New Zealand and the United States of America. Mexican spoligotypes were obtained from isolates collected from cattle in different parts of the country. Spoligotypes from Canada and New Zealand were obtained from different reports in the literature. Those from the United States were obtained from the database of the National Veterinary Services Laboratory in APHIS-USDA. In order to perform the analysis in a single data set, spoligotypes were all converted to binary data and classified according to www.mbovis.org or www.pasteur-guadeloupe.fr:8081. Epidemiologic information included country and species infected. From 3,198 isolates, 174 different spoligotypes were obtained, 95 were orphans. Ninety one percent of the isolates came from the Unites States (n = 1,609) and Mexico (n = 1,323). Spoligotype SB0265 is shared between Canada and the United States in cattle and wildlife. Six spoligotypes, SB0673, SB0121, SB0145, SB0971, SB0140 and SB1165, were frequent in cattle and wildlife in the United States and cattle in Mexico, suggesting wide exchange of strains. Spoligotype SB0669 was found only in Mexico. Spoligotype SB0140 was the most common in Australia and the sixth in the United States and Mexico. In a phylogenetic analysis, spoligotype SB0140 appears as the oldest spoligotype in the data set, suggesting this as the ancestral spoligotype for all spoligotypes in the five countries. Some spoligotypes are shared by animals and humans, corroborating the zoonotic importance of M. bovis.

Efficacy of a vaccine formula against tuberculosis in cattle.

"Test-and-slaughter" has been successful in industrialized countries to control and eradicate tuberculosis from cattle; however, this strategy is too expensive for developing nations, where the prevalence is especially high. Vaccination with the Calmette-Guérin (BCG) strain has been shown to protect against the development of lesions in vaccinated animals: mouse, cattle and wildlife species. In this study, the immune response and the pathology of vaccinated (BCG-prime and BCG prime-CFP-boosted) and unvaccinated (controls) calves were evaluated under experimental settings. A 10(6) CFU dose of the BCG strain was inoculated subcutaneously on the neck to two groups of ten animas each. Thirty days after vaccination, one of the vaccinated groups was boosted with an M. bovis culture filtrate protein (CFP). Three months after vaccination, the three groups of animals were challenged with 5×10(5) CFU via intranasal by aerosol with a field strain of M. bovis. The immune response was monitored throughout the study. Protection was assessed based on immune response (IFN-g release) prechallenge, presence of visible lesions in lymph nodes and lungs at slaughter, and presence of bacilli in lymph nodes and lung samples in histological analysis. Vaccinated cattle, either with the BCG alone or with BCG and boosted with CFP showed higher IFN-g response, fewer lesions, and fewer bacilli per lesion than unvaccinated controls after challenge. Animals with low levels of IFN-g postvaccine-prechallenge showed more lesions than animals with high levels. Results from this study support the argument that vaccination could be incorporated into control programs to reduce the incidence of TB in cattle in countries with high prevalence.

Population structure of Mycobacterium bovis isolates from cattle in Mexico.

The molecular fingerprints of 878 isolates of Mycobacterium bovis collected from cattle between 2009 and 2010 in different regions of Mexico were used in this study. One hundred and ninety-four spoligotypes were observed in total with a high degree of heterogeneity. Sixty-four percent of the isolates grouped into just nine spoligotypes, and 27% fell into only two spoligotypes: SB0673 and SB0669; 149 were orphan spoligotypes. The two predominant spoligotypes were found in almost all states in Mexico, especially in central Mexico, where there is a high concentration of dairy cattle; however, some spoligotypes were closely associated with restricted geographical areas. The hypothetical evolutionary relationship among spoligotypes was estimated using the spoligoforest program in the spolTools webpage. Four trees with connected components and nine unconnected nodes were found. The biggest tree had SB0140 strain as a root, suggesting this as the oldest strain in the tree. However, the relationship of this spoligotype with SB0673 and SB0669 was weak. The discriminatory power of spoligotyping for this M. bovis sample of isolates was 0.94, and the recent transmission index (RTI) 0.83, suggesting a high rate of recent transmission of some strains of M. bovis in the population. This parameter indicates that new measures are required to stop the dissemination of tuberculosis in cattle.

Diagnóstico de ileítis porcina por medio de la reacción en cadena de la polimerasa / Polymerase chain reaction for diagnosis of porcine ileitis

La ileítis porcina es una enfermedad que ocasiona importantes pérdidas económicas a la industria porcina. El agente causal de esta enfermedad es Lawsonia intracellularis, un microorganismo de dificl cultivo. Por esta razón, el diagnóstico, generalmente se realiza sólo al sacrificio. Debido a la dificultad del diagnóstico en animales vivos, se han desarrollado técnicas para detectar el ADN de la L. intracellularis por medio de la reacción en cadena de la polimerasa (PCR). El objetivo de este trabajo fue evaluar la técnica de PCR para el diagnóstico de la ileítis porcina en muestras de mucosa intestinal y heces de cerdos sospechosos de la enfermedad. El ADN fue extraído usando tierras diatomeas y tiocainato de guanidina. Para la amplificación del ADN se utilizaron oligonucleótidos específicos que amplifican un fragmento de ADN de L. intracellularis de 319 pb. La estandarización de la técnica se realizó a partir de mucosa intestinal de un cerdo infectado experimentalmente. La mínima cantidad de ADN de mucosa infectada que se detectó por PCR fue de 3.72 ng. Cuando la mucosa infectada fue adicionada a muestras de heces normales se necesitaron 12.4 ng del ADN extraído, para obtener un producto de amplificación visible. El producto de amplificación esperado de 319 pb fue también obtenido de mucosa intestinal o muestras de heces de cerdos infectados con signos clínicos característicos de ileítis porcina. Se concluyó que la técnica de PCR puede ser muy útil para el diagnóstico de esta enfermedad y para la determinación de la prevalencia de la ileítis porcina en diferentes áreas