Mycobacterial lymphadenitis in pigs on the Darling Downs

ESTUDO DA DINÂMICA DA INFECÇÃO POR MYCOBACTERIUM AVIUM EM UMA POPULAÇÃO SUÍNA ATRAVÉS DE MODELAGEM MATEMÁTICA

RESUMO O presente trabalho estudou, através de modelagem matemática, a dinâmica da infecção por Mycobacterium avium em uma população suína. Para descrever a dinâmica de transmissão de M. avium em granjas de suínos, foi elaborado um modelo de compartimentos. Como esse modelo visava estimar a relação entre taxa de infecção e proporção de suínos que apresentam lesões, detectadas no abate aos 150 dias de idade, resultantes de infecção por M. avium, considerou-se que a dinâmica da doença poderia ser descrita por dois compartimentos de animais: suscetíveis à infecção, e infectados que poderiam vir a apresentar lesões. Através dos resultados obtidos nas simulações realizadas, observou-se que para uma dada força de infecção, a proporção de infectados no final da fase de creche (aqueles que apresentariam lesões no abate) se mantém constante ao longo do tempo, não estando sujeita a variações de caráter sazonal. A simulação matemática da doença, considerando a transmissão horizontal como mecanismo principal da ocorrência de condenações em matadouro por linfadenite granulomatosa é inconsistente com o que se observa na população. Portanto, o componente ambiental tem papel preponderante na dinâmica das infecções micobacterianas dos suínos produzidos no Brasil.

[Tuberculosis lymphadenitis in slaughtered swine from the State of São Paulo, Brazil: microscopic histopathology and demonstration of mycobacteria]

INTRODUCTION

As the occurrence of tuberculosis lymphadenitis in swine constitutes a public health risk, especially in immunosuppressed individuals, the distribution of tuberculoid lesions and the presence of microbacteria in lymph nodes and hepatic and muscular tissue in swine for slaughter, in the State of S. Paulo, SP (Brazil), in the period from 1993 to 1994, were studied. MATERIAL E METHOD: Tuberculous lesions in 60 carcasses of swine, slaughtered at abattoirs during the period 1993-1994, were studied. When macroscopic lesions were observed, a representative sampling of lymph nodes, hepatic and muscular tissues (masseter and diaphragm) were examined using histopathological and microbacterial isolation techniques.

RESULTS

The macroscopic lesions were found predominantly in mesenteric lymph nodes. The MAI Complex (M.avium-intracellulare) was isolated mainly in the carcass group that showed lesions and was not found in the control group. Microorganisms of the MAI Complex were not isolated from hepatic and muscular tissues.

CONCLUSION

No clear relationship between the type of mycobacteria isolated and the macroscopic lesions observed during the carcass inspection was found.

Tuberculin sensitivity of cattle inoculated with atypical mycobacteria isolated from cattle, feral pigs and trought water

Each of 12 cattle was inoculated either subcutaneously and intradermally or into a mesenteric lymph node with 1 of 8 species of liver atypical mycobacteria isolated from cattle, cattle trough water and feral pigs. Seventy-eight days after inoculation the cattle were tuberculin tested with bovine PPD, avian PPD and homologous heat-concentrated syntheic medium tuberculins. They were killed 85 days after inoculation. Organisms were cultured from caseous granulomas at all sites in cattle inoculated with M. avium serotype 2. M. simiae was recovered from a granuloma at the subcutaneous site. Acid-fast bacilli were isolated from the mesenteric lymph node inoculated with trough water organisms. At 72 h, all the cattle had produced skin reactions of 4 mm or more to the homologous tuberculins and all except 1 produced a similar response to avian PPD. Only isolates of bovine origin sensitised cattle to bovine PPD to this degree, and these reactions were less than the corresponding response to avian PPD.

Synthesis and release of sulfolipid by Mycobacterium avium during growth andcell division

Mycobacterium avium exhibits a life cycle wherein small cells elongate to form filaments. The life cycle is unique in that elongated cells will undergo rapid division by fragmentation only if fatty acid is present. The utilization of [14C]palmitic acid and [3H]oleic acid by M. avium during the life cycle was assessed. Four glycolipids, identifiable by elution patterns from hydroxylapatite columns, were associated with postfission cells and contained isotope from the precursor fatty acid. The incorporation of 3H from oleic acid into the cellular glycolipids was maximal during cell division, but as much as 73% of the radioactivity was lost to the lipids from cells in the postfission status. Three of the glycolipids were sulfatides into which 36S was incorporated by M. avium. The [35]sulfatides were synthesized by cells undergoing fragmentation and were recovered from the medium at the termination of cell fission. These results demonstrated that the isotope was not lost to the cells because of turnover, but rather that the labeled compounds were released, intact, from the cells after fission. Because of the facile release of the sulfolipids, it was suggested that they were part of the cell envelope of M. avium cells during the division process.