Date of Award:

1962

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Wildland Resources

Advisor/Chair:

Wayne I. Jensen

Abstract

Avian botulism or ''western duck sickness" has long been a major problem on duck marshes in the western part of the United States. This has been demonstrated to result from the ingestion of products of metabolism of bacterial cells of Clostridium botulinum type C. These products when ingested by waterfowl act as neurotoxins (Coburn, 1942). Studies have shown that many animal tissues are readily utilized as culture media by C1. botulinum type C (Bell et al., 1955).

Since 1955 investigations have indicated a close relation between the occurrence of avian botulism and invertebrate population levels. It is thought that when invertebrates reach peak numbers during their most favorable reproductive season, a large die-off soon follows. Large numbers of birds show symptoms of avian botulism approximately one week after this die-off begins. The theory is that invertebrate carcasses provide a suitable medium for the rapid multiplication of C1. botulinum, and hence, the development of high concentrations of toxin. These toxin-laden carcasses are readily ingested by waterfowl which succumb to the neurotoxins (Jensen and Allen, 1960).

The prime objective of this study was to find some means of preventing invertebrates from attaining high peak numbers during their most favorable reproductive season and thus possibly reduce botulism among waterfowl. Complete kill of the invertebrate population appeared to be undesirable for two reasons: (1) too large a kill would reduce waterfowl below desirable levels; and (2) excessive kill would increase the number of decomposing carcasses and favor the outbreak of botulism. It was theorized that the kill should be between 30 and 60 percent of the invertebrates present prior to the time when peak numbers were reached.

Only those insecticides which have shown little toxicity to wildlife were used in this experiment. Attempts were made to estimate the value of LD 50 for each of the insecticides used in this study. LD 50 is the dosage causing 50 percent mortality in a test population and is considered the most reliable of the LD figures (Rudd and Genelly, 1956).

The specific objectives of this project were: (1) to evaluate the relative effectiveness of selected insecticides, (2) to determine the selectivity of the insecticides on several invertebrate groups, and (3) to determine the treatment most effective in reducing numbers of specific invertebrate groups.

Share

COinS