Serological study of listeriosis in domestic animals in São Paulo-Brazil.

This research studied the presence of L. monocytogenes (bacteria causing listeriosis disease) in different types of domestic animals in São Paulo, Brazil. The results showed varying rates of bacteria reaction, with some animals showing strong reactions indicative of infection.

Research Methodology

• The study conducted serological tests to identify the presence of the bacteria L. monocytogenes in various domestic animals including 7,809 bovines, 838 horses, and 671 swine in São Paulo, Brazil.
• Researchers used the serum agglutination method for the tests, a well-established protocol often utilized to detect and measure the concentration of antibodies (proteins that the body produces in response to harmful substances) in animals’ blood.
• Only somatic antigens (substances that induce an immune response) from L. monocytogenes serotypes 1, 2, 3, 4a, and 4b were utilized in the tests.

Measurement Criteria and Results Interpretation

• A titer of 1/20 was considered reactive, meaning that any serum reacting at this dilution level was considered to have experienced an immune response to the L. monocytogenes bacteria.
• However, the study deemed only the serums with a titer of 1/320 or above to be positive for the presence of the L. monocytogenes bacteria.

Results

• The test showed that in bovine samples, 17.8% were reactive, but only eight samples were positive for L. monocytogenes serotypes 1, 2, and 4b.
• For horses, researchers detected type 1 antigen in 22.7% of the reactive samples, but only 11 samples were deemed positive.
• The test on swine presented a 13.3% reactivity rate, but none were found to be positive since the highest titer was 1/160, which was below the researchers’ positive threshold of 1/320.

This means that while a significant number of animals reacted to the presence of the L. monocytogenes bacteria, few showed strong immune responses that would signify infection. The findings indicated different rates of listeriosis infection among the animal species studied.