Prevalence of three Mycoplasma sp. by multiplex PCR in cattle with and without respiratory disease in central Mexico.

This study aimed to identify Mycoplasma bovis, Myc. dispar, and Myc. bovirhinis, which are involved in bovine respiratory disease through a multiplex PCR as an alternative to culture's features that hamper Mycoplasma isolation. Nasal swabs were taken from 335 cattle with and without respiratory disease background (RDB) from dairy herds in the central region of Mexico. Each sample was divided in two; the first part was processed for the direct DNA extraction of the nasal swab and the second for Mycoplasma isolation, culture, and then the multiplex PCR was performed. In the nasal swabs, Myc. bovis was identified in 21.1%; Myc. dispar, in 11.8%; and Myc. bovirhinis, in 10.8% in cattle with RDB. Isolates were identified as Myc. bovis, 20.1%; Myc. dispar, 11.8%; and Myc. bovirhinis, 6.1%. There is a strong correlation between the presence of Mycoplasma identified by PCR and the clinical history of the disease (ρ < 0.0000). In animals without RDB, Myc. bovirhinis was the only species detected in 6.1% of the samples processed directly for multiplex PCR, and in 2% of the isolates. There is an excellent correlation (kappa 0.803) between the isolation and the 16S PCR and a high correlation (kappa 0.75) between the isolation and the multiplex PCR. Therefore, we conclude that the PCR multiplex test is highly sensitive and may be used for the diagnosis and surveillance of the three species in biological samples and mycoplasma isolates.

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.

Detection of Chamydia psittaci in enteric subclinical infections in adult sheep, through cell culture isolation

Con excepción de México, la clamidiasis en ovinos es una entidad bien determinada en países donde se desarrolla la ovinocultura. A fin de determinar la presencia de Chlamydia psittaci en hatos ovinos en nuestro país, 10 explotaciones de 5 diferentes áreas del altiplano fueron muestreadas, colectándose un total de 267 muestras viables de heces de hembras adultas en SPG (92 de ellas se obtuvieron en un segundo muestreo efectuado en 5 explotaciones elegidas al azar). Las muestras fueron procesadas e inoculadas en células L-929 con medio Iscove's suplementado, realizándose la identificación de las inclusiones intracitoplasmáticas características mediante tinción de Giemsa, e inmunofluorescencia indirecta en muestras sospechosas. Se obtuvo 92.88 por ciento de aislamientos sin observarse diferencias significativas entre los diferentes hatos analizados ni entre los dos muestreos efectuados. Es necesario, en consecuencia, realizar estudios que conduzcan a la identificación del posible papel patógeno de C. psittaci en nuestros ovinos

Detection of Chlamydia psittaci in enteric subclinical infections in adult sheep, through cell culture isolation.

Ovine chlamydiasis is a well known disease in countries with a good practice of breeding sheep herds, not so in Mexico. Aiming to determine Chlamydia psittaci presence in sheep herds in Mexico, we sampled 10 different farmlands in 5 geographical zones on the highlands, gathering a total of 267 viable samples from adult ewes in SPG (92 of them were obtained in a second sampling carried out in five randomly chosen farms). Samples were treated and inoculated on L-929 cells grown in Iscove's supplemented medium; identification of the characteristic intracytoplasmic inclusions was performed by Giemsa stain, and indirect immunofluorescence in suspected samples. Isolation was successful in 92.88% of the trials. No significant differences were observed among the studied herds nor between the two samplings. This high incidence leads to consider seriously the possible pathogenic role of C. psittaci in Mexico.