Resumen Mycobacterium avium subesp. paratuberculosis (MAP) es el agente etiológico de la paratuberculosis o la enfermedad de Johne (JD), una enteritis crónica que afecta al ganado vacuno y otras especies animales que se la vincula con la enfermedad de Crohn, una afección intestinal inflamatoria crónica en humanos. MAP podría resistir las condiciones de pasteurización y se lo aisló de la leche al por menor en varios países. Los objetivos fueron identificar MAP y otras micobacterias en leche y productos lácteos al por menor en Argentina y evaluar la calidad de estos a través del conteo de bacterias aerobias totales mesófilas (TAB). Se analizaron 384 muestras de leche de venta minorista durante 24 meses. Todas las muestras resultaron negativas en cuanto al crecimiento de micobacterias. Sin embargo, el 1.56% de las muestras dieron positivas en la identificación de MAP por IS900-PCR. El recuento de TAB superó los límites establecidos por el Código Alimentario Argentino (CAA) en el 4.95% de las muestras. No se detectaron micobacterias distintas de MAP ni por cultivo ni por PCR. La PCR positiva en MAP resultante de muestras de leche al por menor indicaría que podrían provenir de granjas lecheras con JD y sugiere que la leche pasteurizada o los productos lácteos no son fuentes significativas de exposición humana a MAP en Argentina. Algunas muestras de leche excedieron los límites establecidos por la AAC para los recuentos de TAB, lo cual indica que la leche comercializada podría procesarse y almacenarse incorrectamente.

Abstract Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of paratuberculosis or Johne’s disease (JD), a chronic enteritis disease that affects cattle and other animal species and has been linked to Crohn’s disease, a chronic inflammatory bowel disease in humans. MAP could resist pasteurization conditions and has been isolated from retail milk in several countries. The aims were to identify MAP and other mycobacteria in retail milk and dairy products in Argentina and to assess the product quality through Mesophilic Total Aerobic Bacteria (TAB) count. Three hundred and eighty-four samples of retail milk were tested for 24 months. All samples were negative for mycobacteria growth. However, 1.56% of the samples were positive for MAP identification by IS900-PCR. The TAB count was higher than the limits established by the Alimentary Argentinian Code (AAC) in 4.95% of the samples. Mycobacteria other than MAP were not detected either by culture or PCR. The MAP positive PCR from retail milk samples would indicate that they could come from dairy farms with JD and suggests that pasteurized milk or dairy products are not significant sources of human exposure to MAP in Argentina. Some milk samples exceeded the limits established by the AAC for TAB counts, indicating that commercialized milk could be processed and stored incorrectly.

To study the deficiency of minerals and its relationship with Paratuberculosis, blood, serum, and fecal samples were obtained from 75 adult bovines without clinical symptoms of the disease and from two bovines with clinical symptoms of the disease, from two beef herds with a previous history of Paratuberculosis in the Province of Buenos Aires, Argentina. Serum samples were processed by ELISA and feces were cultured in Herrolds medium. Copper, zinc and iron in serum were quantified by spectrophotometry and selenium was measured by the activity of glutathione peroxidase. We also determined copper, zinc, iron and molybdenum concentrations in pastures and the concentration of sulfate in water. Mycobacterium avium subsp paratuberculosis (Map) was isolated from 17.3% of fecal samples of asymptomatic animals and from the fecal samples from the two animals with clinical symptoms. All the Map-positive animals were also ELISA-positive or suspect, and among them, 84.6% presented low or marginal values of selenium and 69.2% presented low or marginal values of copper. The two animals with clinical symptoms, and isolation of Map from feces and organs were selenium-deficient and had the lowest activity of glutathione peroxidase of all the animals from both herds. All the animals negative to Map in feces and negative to ELISA had normal values of Se, while 13.8% of animals with positive ELISA or suspect and culture negative presented low levels of Se. Half of the animals that were negative both for ELISA and culture in feces were deficient in copper but none of them presented low values of selenium. The content of molybdenum and iron in pasture was high, 2.5 ppm and 1.13 ppm in one herd and 2.5 ppm and 2.02 ppm in the other, respectively, whereas the copper:molybdenum ratio was 1.5 and 5.2, respectively. These results do not confirm an interaction between imbalances of the micronutrients and clinical Paratuberculosis, but show evidence of the relationship between selenium deficiencies in animals with Map infection and ELISA positive results.

A retrospective study was performed on 169 beef and dairy calves aged from 1 to 7 days old submitted to the Diagnostic Laboratories at INTA Balcarce, Argentina. Bacterial culture was performed for aerobic and microaerophilic organisms. Samples from spleen and lymph nodes, and peripheral blood mononuclear cells were also cultured for viral isolation on cell culture. Bovine rotavirus was detected by direct-ELISA. Multiple tissue samples were fixed in 10% formalin, routinely processed and stained with hematoxylin and eosin for microscopic examination. Etiological diagnosis was made in 70 of the 169 calves. Infectious agents were identified in 49 cases, the most common being Escherichia coli. When the histopathological examination was performed in cases with undetermined diagnosis, it was noted that 44 specimens had histological lesions, which suggested the presence of an infectious agent. In order to characterize the causes of bovine neonatal mortality, the protocols and methodology should be improved in further works.

Se realizó un estudio restrospectivo en 169 terneros muertos 1 a 7 días después del nacimiento pertenecientes a rodeos para carne y leche, remitidos a los Laboratorios de Diagnóstico del INTA Balcarce, Argentina. Para detectar organismos aeróbicos y microaerófilos se realizó el cultivo bacteriano. Para el aislamiento viral sobre cultivo celular, se recolectaron muestras de bazo, ganglios linfáticos y sangre periférica. El rotavirus bovino fue identificado por ELISA directo. Se efectuó el examen microscópico de diferentes tejidos, los cuales fueron fijados en formol al 10%, procesados y teñidos con hematoxilina y eosina. Se obtuvo un diagnóstico etiológico en 70 de los 169 terneros. Se identificaron agentes infecciosos en 49 casos, siendo el más común Escherichia coli. En los casos con diagnóstico indeterminado, el examen histopatológico realizado determinó que 44 especímenes poseían lesiones compatibles con la presencia de agentes infecciosos. Es necesario mejorar los protocolos y las metodologías de trabajo a los fines de caracterizar las causas de mortalidad neonatal en bovinos.

Paratuberculosis or Johne's disease is a chronic enteritis of the cattle and other small ruminant animals caused by Mycobacterium avium subsp. paratuberculosis. In Argentina, the strains were characterized in beef and dairy cattle and deer in different genetic patterns by molecular tools. M. avium subsp. paratuberculosis has been linked in men to a chronic inflammation of the intestine, named Crohn's disease. There is clinical and experimental evidence to link M. avium subsp. paratuberculosis with Crohn's disease by PCR, positive bacteriological culture from mother milk, blood and affected tissues by in situ hybridization. The milk and sub-products might be one of the possible infection sources and it has been suggested that M. avium subsp. paratuberculosis could resist pasteurization. Several works showed that this mycobacteria could be present in retail milk of countries such as United Kingdom, USA, Czech Republic, and recently in Argentina. M. avium subsp. paratuberculosis was associated with different dairy products and water for human consumption. Therefore, it is possible that these food sources may have a role for transmission. New investigations should emphasize the role of contaminated food and water in human infection around the world and determine the possible zoonotic role of M. avium subsp. paratuberculosis.

La paratuberculosis o enfermedad de Johne es una enteritis crónica producida por Mycobacterium avium subsp. paratuberculosis, que afecta a bovinos y a otras especies. En la Argentina se ha caracterizado en rodeos bovinos y de ciervos, con aislamientos tipificados en distintos patrones genéticos. M. avium subsp. paratuberculosis ha sido vinculado en humanos con una inflamación crónica del intestino, denominada enfermedad de Crohn. Existen evidencias clínicas y experimentales que relacionan a M. avium subsp. paratuberculosis con la enfermedad en el humano, mediante su detección por PCR y por cultivo a partir de biopsias de órganos, de leche materna y de sangre de pacientes afectados. La leche y sus subproductos serían posibles fuentes de infección y se ha sugerido que M. avium subsp. paratuberculosis resistiría las condiciones de pasteurización. Diversos trabajos de investigación demostraron que esta micobacteria podría estar presente en leches comercializadas en diversos países, como Reino Unido, Estados Unidos, República Checa, y también en la Argentina. La presencia de M. avium subsp. paratuberculosis en productos lácteos y agua de consumo ha sido relacionada con la resistencia del microorganismo tanto a los procesos de elaboración como a los factores climáticos adversos, lo que enfatiza el rol de los alimentos y del agua como vías de transmisión al humano. Las investigaciones en curso podrían ratificar el riesgo y las implicancias de la exposición del humano a M. avium subsp. paratuberculosis a través de los alimentos y del agua contaminados, para determinar la importancia de la paratuberculosis como enfermedad zoonótica.