Application of PCR to a clinical and environmental investigation of a case of equine botulism.

The research is investigating a case of equine botulism through the use of PCR (polymerase chain reaction) to detect botulinum neurotoxin genes in samples from a sick foal and the surrounding environment. The results show that PCR is an effective method, compatible with traditional mouse bioassay tests, and that the presence of the botulinum toxin B type is prevalent in the soil where the foal was raised.

Research Methodology and Tools

• The researchers used PCR, a technique that amplifies DNA, for the detection of botulinum neurotoxin gene types A to E. This was applied on samples from a foal that was diagnosed with toxicoinfectious botulism back in 1985.
• The tests were compared with the mouse bioassay, a standard test for botulism detection that uses mice. The samples tested in this way include sera, spleen, feces, and intestinal contents of the foal.
• The researchers also conducted an environmental survey alongside testing of the foal. This involved soil sample collection around the area the foal was raised and testing those samples for Clostridium botulinum (the bacteria that produces botulinum toxins).

Research Findings

• The analysis revealed that neurotoxin B, a type of botulinum toxin, was detected in the samples from the mouse bioassay. Consistent results were found from the PCR testing, where the gene for the B type neurotoxin was also detected.
• No other neurotoxin types (A, C, D, E) were detected in either the bioassay or PCR tests.
• PCR results showed that neurotoxin B genes were also found in a liver sample, which was not detected in the mouse bioassay.
• In the soil samples collected from the foal’s living environment, there was a prevalent presence of Clostridium botulinum type B.
• Various methods (PCR and agarose gel electrophoresis, PCR and an enzyme-linked assay, hybridization with type B-specific probe, and mouse bioassay) were used to test for botulinum neurotoxin-producing organisms in the soil samples.
• Among these methods, conventional detection of PCR products by gel electrophoresis was found to be the most sensitive method, capable of detecting the presence of as little as 300 cells.

Conclusion and Implications

• The study suggests that PCR is an effective method of detecting botulinum neurotoxin genes. Its results align well with the traditional mouse bioassay, and it can also detect the neurotoxin in samples where the bioassay could not (e.g., the liver sample).
• The findings indicate a high prevalence of Clostridium botulinum type B in the foal’s environment, suggesting a potential source of the botulism infection.
• The prevalence of neurotoxin B genes in the environment may have implications for efforts to control and prevent botulism in equine populations.