Prevalence of Clostridium botulinum type C in substrates of phosphate-mine settling ponds and implications for epizootics of avian botulism.

Prevalence and conditions for occurrence of Clostridium botulinum type C were examined on phosphate-mine settling ponds and a natural wetland in northern Florida between April 1981 and March 1982. Substrate samples were collected monthly (winter) and semi-monthly (summer) from 16 locations on seven ponds. Selected environmental parameters were measured at each location at the time of sampling. Mouse inoculation tests and toxin neutralization tests using enrichment culture filtrates were conducted to identify C. botulinum type C in the samples. The bacteria were identified in 26 (5.6%) of 467 sediment samples. Occurrences were distributed over four of the seven ponds and included nine of the 16 sample locations, but were restricted to the months April through October. The organism occurred over a wide range of ecological conditions found on the ponds during these months. If the presence of C. botulinum type C in the substrate is a prerequisite for botulism to occur, the prevalence and fairly wide distribution of this organism on settling ponds makes it difficult to predict where future outbreaks may occur.

An epizootic of avian botulism in a phosphate mine settling pond in northern Florida.

Type C botulism was determined to be the cause of an epizootic among waterfowl and shorebirds in a phosphate mine settling pond in northern Florida during May and June of 1979. Several hundred birds, the most common of which were American coots (Fulica americana), wood ducks (Aix sponsa), common gallinules (Gallinula chloropus), and northern shovelers (Anas clypeata), were afflicted over about a three-week period. A second smaller outbreak occurred in the same pond in early December of 1979. This is apparently the first time that botulism has been reported in waterbirds of Florida.

Organochlorine pesticide residues in plain Chachalacas from South Texas, 1971-72.

Plain chachalacas (Ortalis vetula) from the intensively cultivated and sprayed Lower Rio Grande Valley of Texas were analyzed for pesticide residues during 1971 and 1972. Residues of eight organochlorine pesticides and a polychlorinated biphenyl were identified in fat tissues of specimens collected from four study areas. Chemicals detected in all 24 birds and average residue levels (+/- SD) in ppm wet weight were: DDT (1.52 +/- 4.12), DDE (2.48 +/- 2.09), dieldrin (0.23 +/- 0.59), endrin (0.13 +/- 0,52), and Aroclor 1248 (0.17 +/- 0.20). Residue levels varied considerably, but the majority of the fat tissues contained significantly less than 1 ppm of these chemicals. Because birds of this species feed primarily on unsprayed native fruits rather than on sprayed crops, they adsorb very few pesticides through their diet. Although birds from exposed areas near cultivated field had generally higher residues than had birds from less exposed areas, these herbivores generally had much lower residues than would most birds living near heavily treated lands. During the present study there was no evidence that plain chachalacas died as a direct result of exposure to agricultural chemicals, nor was there evidence that eggshells of this species have thinned significantly since 1900.