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Fifteen Yorkshire female pigs were inoculated with 100,000 infective T. canis eggs. Three animals were used as uninfected controls. Groups of three infected pigs were euthanized by accepted methods on days 7, 14, 21, 28 and 126 p.i., respectively. Larvae were recovered from all animals included in each group slaughtered on days 7 and 14 p.i.; on day 21 p.i. from two pigs, on day 28 p.i. from one, and no larvae were found on day 126 p.i. Differences in the mean number of larvae per gram in lymph nodes, liver and lungs between slaughter days, were significant for livers on day 7 p.i. and for lungs on day 14 p.i. (P < 0.10). The decrease over time was significant in all the organs that previously had larvae. Larvae were not found in the other organs and tissues analysed. Macroscopical lesions were found in the liver, lungs and lymph nodes on days 7, 14, 21, and 28 p.i. The entire surface of the liver was covered with small white spots on day 7 p.i., on days 14 and 21 p.i. the spots were distinctly nodular and, in some places, individual lesions were confluent. Lesions had apparently started to heal on days 28 and 126 p.i. appearance was normal. Lymph nodes were enlarged and oedematous during the first 4 weeks and the lungs had small areas of consolidation visible all over the surface, but by day 126 p.i., no visible lesions could be seen. Microscopical lesions were observed in the liver on day 7 p.i., with a largely periportal hepatitis. Numerous eosinophils and lymphocytes were present. The typical granulomatous reaction was observed on days 14 and 21 p.i. with a central necrotic core and a narrow region of fibroblastic tissue. By day 28 p.i. lesions had almost disappeared and the number of eosinophils was fewer. There were fewer leukocytes and the fibrous tissue had disappeared from the liver on day 126 p.i. For the first 3 weeks, pictures of the lymph nodes and the lungs were characterised by the formation of a granuloma. In the center of the granuloma larvae were observed. The majority of the lesions had healed by day 126 p.i.

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A total of 206 strains of Staphylococcus aureus isolated from bovine clinical and subclinical mastitis in Argentina during 1996 to 1998 were investigated for their in vitro susceptibility to several antimicrobial agents. Minimum inhibitory concentrations that inhibit 90% of the strains tested reported in micrograms per milliliters were: 1.5, 0.5, 0.75, 1.50, 0.75, 1.0 and 0.125 for penicillin, oxacillin, cephalothin, gentamicin, erythromycin, clindamycin and ampicillin-sulbactam, respectively. Resistance was detected in 83 (40.3%), 24 (11.6%), 16 (7.7%) and 7 (3.4%) S. aureus isolates for penicillin, erythromycin, pirlimycin and gentamicin, respectively. No resistance was detected for oxacillin, cephalothin and ampicillin-sulbactam. Results indicated that S. aureus isolates in Argentina exhibited high resistance to penicillin of all antimicrobial agents tested.

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El análisis de la bibliografía disponible sobre el aislamiento del virus de la fiebre aftosa reveló que la inoculación de animales de laboratorio con fines diagnósticos no ha sido uniformada. Los estudios realizados sobre la efectividad de las distintas especies difieren metodológicamente entre sí, en lo que respecta a varios parámetros que incluyen la especie, edad, sexo y cepa del huésped, así como la dosis, vía de inoculación y volumen del inóculo. El empleo de virus adaptados a cultivos o a diferentes especies animales representa otra variable, si se considera que su infectividad no sería comparable a la de las cepas de campo. Por ende, se desconoce la susceptibilidad comparativa de las distintas especies de animales de laboratorio para aislar el virus de la fiebre aftosa y consecuentemente, su efectividad diagnóstica en muestras de bovinos infectados naturalmente.

Analysis of the available literature on the isolation of foot-and-mouth disease virus revealed that the inoculation of laboratory animals for diagnostic purposes has not been uniform. Studies carried out on the effectiveness of a variety of species differ from each other methodologically in several parameters which include the species, age, sex and strain of host as well as the dose, route of administration, and volume of the inoculum. The use of viruses adapted to culture or to different laboratory animal species represents another variable if it is considered that their infectivity may not be comparable to that of field strains. On this basis, the comparative susceptibility of the different species of laboratory animals to isolate Aphthovirus, and consequently, their disgnostic effectiveness in samples from bovines with natural infections, remains to be determined.

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Los hallazgos del presente estudio demuestran que el hamster es más susceptible a la infección por el virus de la fiebre aftosa que el ratón lactante, habitualmente empleado para efectuar aislamientos de este agente con fines diagnósticos. El hamster mostró una susceptibilidad superior a la inoculación de Aphthovirus obtenidos de bovinos infectados naturalmente. La comparación se basó en las manifestaciones clínicas, el tiempo medio de supervivencia, el porcentaje de mortalidad, la relación entre título y mortalidad, y el comportamiento de la infección en animales destetados. Le siguieron en orden descendente de susceptibilidad los meriones, conejos y cobayos lactantes, mientras que las ratas resistieron a la infección. Los resultados se analizan en términos de su implicancia diagnóstica para estudios epidemiológicos y el control de la enfermedad.

The present findings demonstrate that the hamster is more susceptible to infection with foot-and-mouth disease virus than the sucking mouse, traditionally used for isolating this agent. Hamsters were more sensitive to the inoculation of Aphthovirus obtained from bovines with natural infections. The comparison was based on clinical manifestations, mean survival time, percent mortality, relationship between titer and mortality, and evolution of infection in weanlings. Following in decreasing order of sisceptibility were suckling gerbils, rabbits and guinea pigs, while rats were refractory. The results are discussed in terms of their diagnostic implications for epidemiologic studies and disease control.

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