Human brucellosis: review of an under-diagnosed animal transmitted disease.

Human brucellosis is an important animal transmitted disease of man. Although, the cases have been recorded all over the world, the prevalence is higher in developing countries. Lack of sufficient knowledge about the disease among the physicians, its under-diagnosis or misdiagnosis and absence of effective prevention and management strategies are attributed to the widespread of the disease. Increase in the occurrence of animal brucellosis has also resulted indirectly in an increase in the prevalence of human infection. Absence of characteristic clinical symptoms, chronic nature of the infection and difficulty in isolation of the causal agent from the patients make the diagnosis of the disease more difficult. The serological tests employed for diagnosing human brucellosis vary in terms of their sensitivity and specificity. Therefore, a combination of serological tests is desirable. Currently no vaccine is available against human brucellosis, which could check the spread of the disease effectively. It is suggested that clinicians investigate the cases of pyrexia of unknown origin (PUO) for brucellosis. It is desirable that specimens from cases of tuberculosis, typhoid, rheumatoid arthritis, urogenital infections, kala-azar, cirrhosis, bacterial endocarditis, leukemia and filariasis should also be screened for brucellosis in man. The cases of meningitis of unestablished etiology as the cases of human brucellosis are often misdiagnosed as cases of typhoid or tuberculosis.

Seroprevalence of brucellosis in man.

A total of 352 human serum samples were screened for brucellosis. A combination of serological tests including Rose Bengal plate test (RBPT), standard tube agglutination test (STAT) and dot-enzyme linked immunosorbent assay (dot-ELISA) were employed for the purpose. The study revealed a prevalence rate of 4.97 per cent in samples that included specimens from persons occupationally exposed to animals. The number of seropositives through all tests used was higher among males (5.95 per cent) than females (3.15 per cent). A markedly higher prevalence of 17.39 per cent was recorded among field veterinarians. A low prevalence (2-6 per cent) was observed in humans with unknown history of animal contact. Dot-ELISA yielded 4.97 per cent positives compared to 1.38 and 0.82 per cent through RBPT and STAT respectively.

Enterotoxigenicity as an attribute of virulence in Yersinia enterocolitica.

Seven strains of Y. enterocolitica were screened for their enterotoxic activity. Three strains belonging to serogroups 0:3 and 0:9 elicited enterotoxic response in rabbit ligated gut segments and in infant mice. The enterotoxin resisted heat at 65 degrees and 100 degrees C for 20 min. The toxin was eluted in the second beak material during Sephadex G-75 gel filtration. On the basis of polyacrylamide disc gel electrophoresis the toxic component had a molecular weight of about 12,400.

Tissue changes induced by enterotoxic preparations of Salmonella weltevreden in ligated rabbit gut segments.

Culture filtrates and cell lysates of two strains of S. weltevreden which caused dilation of ligated rabbit gut segments (characteristic associated with the enterotoxic activity) induced mild to severe architectural changes in the test segments of intestine. The dilated segments contained thick, bloody and mucoid exudates. The results suggested that besides invasiveness and enterotoxigenicity, S. weltevreden possibly possessed factor (s) that damaged intestinal tissue and played part in the pathogenesis of Salmonella gastroenteritis.

A delayed permeability factor in the culture filtrates and cell lysates of Salmonella weltevreden.

Salmonella weltevreden strains produced a delayed permeability factor (PF) when tested on depilated rabbit skin. The PF activity could be demonstrated in freshly concentrated culture filtrates as well as in the cell lysates. The activity varied with strain and preparation. The induration and blueing reactions were associated with well marked balancing zones.