Everyone has an opinion about turkey populations. When turkey hunters get together, inevitably the conversation revolves around whether there are too many hens or too many turkeys in general. Sometimes turkey hunters speculate about disease when the birds are numerous. People who care about turkeys worry about maladies such as blackhead, West Nile Virus, mycoplasmosis and avian pox. At times, the agricultural community expresses concern about wild turkeys infecting their poultry or cattle and affecting egg or milk production.
Individual wild turkeys do fall victim to diseases and parasites. A number of bacterial and viral infections occur in wild turkeys, but diseases and parasites are rarely limiting factors affecting turkey populationsanywhere within their range. In fact, no wild turkeys have ever been linked to disease outbreaks in domestic poultry or cattle. Most bird diseases cannot be transmitted to mammals.Biologists, veterinarians and pathologists have studied wild turkeys for decades. A number of disease agents have been documented in individual wild turkeys. Some infectious diseases seen in wild turkeys are caused by viruses, others are caused by bacteria and mold. It would take many pages to list all the illnesses that might affect turkeys so we will limit this discussion to some likely possibilities.
While wild turkeys are susceptible to diseases that affect domestic chickens, turkeys and other poultry, wild turkeys do not seem to serve as reservoirs for such diseases.
Shake the disease
Avian pox is a viral disease that accounts for nearly one quarter of the diagnoses of sick or dying wild turkeys examined in the southeastern United States. Wildlife pathologists reported a few cases of avian pox in 12 of 13 years in 8 southeastern states between 1972 and 1985 so this disease is pretty common. The virus may be transmitted by mosquitoes and other blood-feeding insects and by direct contact between infected and uninfected birds. The disease occurs most frequently in wet years when vector (the insects that transmit the virus) populations are high. Avian pox can be fatal, though a wild turkey may survive for quite some time with a pox infection. Open sores on exposed skin of the head and neck and on leg scales are characteristic of the disease. The lesions are also found in the trachea and esophagus, affecting breathing and feeding. Affected turkeys are sometimes emaciated. Though avian pox is probably the most common disease affecting wild turkeys, it is not a major threat to the population.
Other viral diseases that have been noted in wild turkeys include western equine encephalitis, St. Louis encephalitis and eastern equine encephalitis. West Nile virus is prevalent in the United States and is another type of encephalitis. All of these viral infections have been documented through blood tests that showed wild turkeys had antibodies to the diseases. In other words, wild turkeys have been exposed to them. However, none of these infections seem to have a major affect on wild turkeys. With West Nile virus, wild turkeys have rarely shown clinical symptoms and the level of virus in their blood is thought to be insufficient to re-infect any other organisms.
Avian influenza is a viral infection that has been a serious problem in domestic poultry operations and wild waterfowl. Whenever an outbreak occurs in domestic poultry, the affected flocks are destroyed to prevent the spread of the disease. Though some poultry operators are fearful that wild turkeys may carry the disease and pose a threat to commercial poultry operations, avian influenza has never been found in wild turkeys. The greatest threat for the spread of the virus is migratory birds.
Mycoplasmosis is another viral disease common to the domestic poultry industry. It comes in several forms, the most frequently encountered being Mycoplasma gallisepticum. This malady is quite common among backyard poultry flocks and pen-raised game birds, but has been found only rarely in free-raging wild turkey flocks. Mycoplasmosis has been documented in wild turkeys in Georgia, California and Colorado. In two of the three cases, the turkeys were interacting with domestic poultry. Antibodies to Mycoplasma gallisepticum have been found in wild turkeys in California, Colorado, Missouri, Texas and Wisconsin. The incidence of antibodies is extremely low, indicating the disease is very rare in the wild.
Many turkey hunters have heard of a newly isolated disease virus and are concerned about its impact. Lymphoproliferative disease virus was historically found in domestic turkeys in Europe and the Middle East. Since 2009, the Southeastern Cooperative Wildlife Disease Study has identified multiple cases of Lymphoproliferative disease virus in wild turkeys from throughout the Southeast, Midwest and Northeast. Many of the birds in which this virus was found had evidence of other diseases. There is not enough information to determine the impact on wild turkeys. It appears the disease has been around for some time even though it was only recently documented in wild turkeys.
Wildlife experts are monitoring this and other diseases carefully. Wild turkeys are subject to a number of diseases caused by parasites. One of the most well known is histomoniasis AKA or “blackhead” disease. Chickens, pheasants, turkeys and other Old World birds can survive blackhead and serve as a reservoir for the protozoan parasite (Histomonas meleagridis) that causes the disease. It is a complex infection that involves an intermediate host. The eggs of the worm and the protozoan parasite can be found in earthworms. Wild and domestic turkeys develop severe symptoms after infection as the parasites create lesions in the liver and intestines. This infection results in death very quickly among wild turkeys.
Among the parasites that affect wild turkeys are cestodes (tapeworms are one form), trematodes and nematodes. They also harbor external parasites such as ticks, mites and feather lice. The external parasites can impact the health of individual turkeys when they are stressed or when food is in short supply. However, most wild turkeys are healthy enough to withstand the normal external parasite load.
Good news for you
Wild turkeys do get sick and some die. There will always be small losses of wild turkeys to diseases in any given year. However, disease generally does not play a major role in limiting wild turkey populations. So when someone asks you if large numbers of wild turkeys will increase the incidence of disease and decimate the flocks, you can be pretty confident it is unlikely. Diseases that affect wild turkeys are not a threat to people or domestic animals.
If you ever harvest a wild turkey that appears to be acting strangely or seems to be ill, keep it cold, not frozen, and get it to your state wildlife agency for examination.