Brucellosis outbreak in a rural endemic region of Mexico - a comprehensive investigation.

Brucellosis is a worldwide zoonotic disease. Generally, humans can be infected by either the consumption of raw milk and fresh cheeses made from unpasteurised milk or by contact with infected animals, mainly in endemic regions. In this study, we investigated a brucellosis outbreak in State of Guanajuato, an endemic region of Mexico. Microbiological culture of human blood, raw milk from cows and goats, and fresh cheeses was performed to isolate Brucella. Identification of the bacteria was done by bacteriological procedures and by multiplex Bruce-ladder polymerase chain reaction (PCR). Brucella melitensis was isolated from patients, infected goats, and fresh goat cheeses; while Brucella abortus was isolated from cows. All patients had eaten fresh cheese, but no occupational exposure to animals was reported. The results of molecular typing did not show any Brucella vaccine strains. The isolation, identification, and molecular characterisation of Brucella spp. in both human brucellosis cases and infected animals are very important to identify the source of infection and to take control measures in endemic regions.

Prevention of Blackleg by an immunogen of Clostridium chauvoei.

Diseases in livestock caused by Clostridium spp. are of concern in Mexico. There are no good-quality vaccines against these infections, and for this reason several outbreaks have occurred in recent years. The objective of this work was to study the immunogenic capacity of a 156-kDa recombinant protein of Clostridium chauvoei that has shown 80% protection against this disease in guinea pigs. This immunogenic protein was cloned in the expression vector pBluescript and was used to immunize C. chauvoei-free bovine animals that were kept in an endemic area. Three experimental groups were studied. In group 1, 30 bovines were vaccinated by subcutaneous route with one dose of 350 microg/animal of the recombinant protein of 156 kDa. In group 2, 30 bovines were vaccinated with the same concentration of this protein plus aluminium hydroxide as adjuvant. Group 3 was vaccinated with a commercial bacterin by intramuscular route with a dose of 5 mL/animal. In each group, five animals were inoculated with saline solution and remained as controls without vaccination. Blood samples were obtained each month during a 6-month period. Serum samples were analyzed by agglutination test and Western blotting. The recombinant protein of 156 kDa was recognized by serum samples from all the animals in groups 1 and 2. Only two animals from group 3 recognized this protein. During the time of the experiment any cases of this disease were observed. However, other studies with a longer time or greater stress conditions that would favor occurrence of the disease would be required to confirm whether this immunogen is also protective in bovines.