AVIAN BOTULISM—ANOTHER PERSPECTIVE
Waterfowl botulism is unique among intoxications because toxin produced within its victims leads to secondary poisoning of other birds. Because of this phenomenon, the epizootiology of the carcass-maggot cycle of botulism resembles that of an infectious disease and the reproductive rate (R) of the disease could be defined as the average number of secondary intoxications attributable to a single carcass introduced into a marsh. I propose that toxin production and botulism occur commonly at a low level in many marshes and that factors which influence R determine when the disease expands into a large epizootic. A model that incorporates the number of carcasses occurring in a marsh, the probability of a carcass containing spores, the probability of a carcass persisting until toxin-bearing maggots emerge, and the contact rate between live birds and toxin, may be useful for predicting the extent of secondary-poisoning, for identifying questions for research, and as a theoretical basis for management.
Real-time polymerase chain reaction for the detection of toxigenic Clostridium botulinum type C1 in waterbird and sediment samples
A quantitative real-time PCR (qPCR) for detection of the neurotoxin of the Clostridium botulinum type C (BoNTC) encoding gene has been compared with a nested PCR (nPCR) and a conventional PCR (cPCR) using 2 toxigenic C. botulinum C1 reference strains and samples from bird tissues (n = 30) and sediments (n = 30) from wetlands where botulism outbreaks have been reported. A cPCR based on 16S ribosomal RNA sequences from 60 strains of Clostridium species was also developed to detect the genomic DNA of C. botulinum C in order to evaluate the presence of nontoxigenic strains. Quantitative PCR showed a similar sensitivity to nPCR (<0.5 pg of DNA), and both were more sensitive than the cPCR when using the C. botulinum reference strains. Quantitative PCR and nPCR revealed an equal number of positives in uncultured samples of sediments (3%) and bird tissues (40%), but these values tended to be higher after culture enrichment with the qPCR assay (10% and 80%, respectively). Associations between the presences of toxigenic C. botulinum C in the environment and in birds within the ecological conditions in wetlands could be studied further using the culture enrichment and qPCR techniques shown in the current study.
High-Speed Infrared Radiometers*
The paper describes high-speed infrared radiometers utilizing thermistor infrared detectors. Instruments with 4- and 8-in. diam Cassegrain mirror optics are described. The method of operation and the calibration of these radiometers is discussed.The radiometers are uniformly sensitive from 0.7 to 35 μ. They have a response time of 16 msec and a sensitivity of the order of 10−10 w/cm−2 corresponding to a blackbody temperature differential of 0.01°C.The radiometers are used for quantitative measurements of infrared radiation and remote temperature determinations.