Botulism in captive birds fed commercially-bred maggots

Development and Validation of a New Reliable Method for the Diagnosis of Avian Botulism

Liver is a reliable matrix for laboratory confirmation of avian botulism using real-time PCR. Here, we developed, optimized, and validated the analytical steps preceding PCR to maximize the detection of Clostridium botulinum group III in avian liver. These pre-PCR steps included enrichment incubation of the whole liver (maximum 25 g) at 37°C for at least 24 h in an anaerobic chamber and DNA extraction using an enzymatic digestion step followed by a DNA purification step. Conditions of sample storage before analysis appear to have a strong effect on the detection of group III C. botulinum strains and our results recommend storage at temperatures below -18°C. Short-term storage at 5°C is possible for up to 24 h, but a decrease in sensitivity was observed at 48 h of storage at this temperature. Analysis of whole livers (maximum 25 g) is required and pooling samples before enrichment culturing must be avoided. Pooling is however possible before or after DNA extraction under certain conditions. Whole livers should be 10-fold diluted in enrichment medium and homogenized using a Pulsifier® blender (Microgen, Surrey, UK) instead of a conventional paddle blender. Spiked liver samples showed a limit of detection of 5 spores/g liver for types C and D and 250 spores/g for type E. Using the method developed here, the analysis of 268 samples from 73 suspected outbreaks showed 100% specificity and 95.35% sensitivity compared with other PCR-based methods considered as reference. The mosaic type C/D was the most common neurotoxin type found in examined samples, which included both wild and domestic birds.

Observations on environmental factors in connection with avian botulism outbreaks in a Hungarian wetland habitat

In this study, the relationship between five water-quality parameters (water temperature, pH, conductivity, water-soluble oxygen (WSO) and organic matter content (chemical oxygen demand-COD)) and avian botulism cases were examined using statistical methods. Five-five sampling points, located in high and low avian botulism risk (HR and LR) areas of Lake 'Kis-Balaton' were chosen, respectively. Data from 5 HR and 5 LR years were processed. In some cases, significant (P<0.05) differences were discovered in water temperature, pH, WSO and COD values between HR and LR sites and years. Discriminant analysis verified positive relationship between the occurrence of avian botulism outbreaks and characteristics of the sampling sites in 16/20 cases (80.0%). In the remaining instances, the role of other, not examined factors could be also important.