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Wildlife Diseases

Bayou-Diversity (1 July 2018) Medicare, Medicaid, cancer, and heart disease are a few examples of human health issues that seem to constantly make head-lines. But even for many of us who are outdoor enthusiasts, the health of Louisiana’s native wildlife populations is rarely contemplated. Diseases of wildlife are not new. They have been recognized for centuries. More than 2,000 years ago references to diseases in wildlife were recorded in the Bible, as well as in the writings of Homer and Aristotle. As a science, though, this subject has only developed in the past 50 years.

Diseases in wildlife are often similar to those in humans, the causative agents usually bacteria, viruses, or parasites. In many instances these diseases are a natural part of an ecosystem and serve to keep populations in balance with their habitat, just as predators sometimes do. Diseases of deer have been well studied, and herd health checks are routinely conducted in Louisiana. One standard test, which determines the number of stomach parasites, yields results that correlate with the general health of a herd: high parasite count = poor herd health, usually as a result of too many deer in a given area, or low parasite count = good health and a herd in balance with its habitat.

Mortality associated with wildlife diseases frequently goes unnoticed because it doesn't often occur on a large scale in a short period of time, and scavengers quickly recycle the evidence. Exceptions exist, particularly with reference to waterfowl. In the winter of 1965-66 an estimated 70,000 birds died of avian cholera in north-central California. Even larger outbreaks involving diving ducks have occurred in the Chesapeake Bay. Birds are also subject to botulism, tuberculosis, salmonellosis, avian pox, and sarcocystis. Local wild mammals must contend with hemorrhagic disease, anaplasmosis, leptospirosis, and rabies, among others. Chronic wasting disease in deer is a current concern.

The occasions when wildlife diseases are not natural cycling mechanisms in Louisiana ecosystems can always be traced to humans. Toxic diseases such as lead, mercury, and pesticide poisoning result from human insensitivity to wildlife. Humans have introduced alien diseases into susceptible native wildlife via pets, domestic animals, and exotic species. More than any other, these diseases pose serious threats to local wildlife and serve to remind us of the vulnerability of wild animals to disease, both natural and unnatural. (image by KO; toxic lead shot in gizzard of pintail duck that died of chronic lead poisoning)


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