What is a disease you may ask yourself at first? Disease can be defined in many ways, but a common definition would be any impairment that would interfere or modify normal functions, with responses to factors such as nutrition, infectious agents, defects, or toxicants (Wobeser 1997). Disease outbreaks follow a simple three way path that involves a host, agent, and the environment. Wide arrays of avian diseases are found throughout the bird world, but much is still unknown about them. According to Karstad, “disease in wildlife populations is rarely a one-cause, one-effect situation. Usually it is caused by profound changes in the environment” (Wobeser 1997).
They can range from bacterial diseases such as avian cholera, botulism, tuberculosis, salmonellosis, and chlamydiosis; to different viral diseases such as duck plague, inclusion body disease, and avian pox. Other diseases found in waterfowl are fungal diseases (aspergillosis), parasitic diseases like sarcocystis, gizzard worms, and nasal leeches. Lead poisoning and oil toxicosis are two lethal toxic diseases also found to occur. This topic will focus on what is avian botulism, what are the causes, and ways to prevent outbreaks from occurring.
Avian botulism is also known as limberneck, western duck sickness, duck disease, and alkali poisoning. “Botulism” was first termed over 100 years ago when man ate spoiled sausage. Research on avian botulism didn’t occur until the early 1900’s. Cases were documented as early as 1876 and 1893 when large numbers of waterfowl were found dead in Great Salt Lake marshes. Botulism is caused by the ingestion of a specific toxin that is produced by the bacterium, Clostridium botulinum (Davis et al. 1971). Seven different strains of the toxin have been identified and they affect different species of birds and mammals. Type A strain of botulism is limited to mostly affecting domestic chickens, and many fish eating birds such as loons and gulls are affected by type E botulism. The other strains of B, D, F, and G have not had any documented cases in the United States.
Waterfowl are most commonly affected by the C strain of toxin. Historically it is thought that the type C strain has the most major outbreaks in the years that have high amounts of rainfall in the spring and summer with high flows in the surrounding water systems. The type C strain is found in two forms, either spores or in vegetative cells. The spores are formed when vegetative growth cannot go forward and can exist in hot, dry, cold, and acidic conditions, where vegetative cells only grow when there is oxygen absent and in a small temperature window (Kadlec 2002). Growth is found in wetlands with simple organic compounds found throughout the water column and may be caused by different factors like water depth, level fluctuations, water quality, types of organisms, and rotting vegetation.
Throughout most of the United States and Canada most outbreaks occur from July through September with...