This paper is intended to be a general guide about diseases that hunters and their hunting dogs may encounter. Links to additional information have been provided where appropriate. Hunters should always consult their physician if they are concerned they have been exposed to a disease or are showing symptoms of illness. If there are any concerns that your hunting dog or any other companion animal may have contracted any of these diseases, please contact your veterinarian.
Protecting Hunters from Risk: Some Common Sense Guidelines
There is an increasing awareness among hunters that there are medical risks associated with handling wildlife, and certain safety precautions should be taken. The American Veterinary Medical Association (AVMA) has the following advice on certain health concerns linked to hunting, both in North America and in other areas of the world. This document is by no means intended to discourage people from hunting; instead, it is intended to inform hunters of the risks they face and steps they can take to reduce those risks.
Hunters and their dogs can be exposed to infectious diseases not only from infected animals, but also via insect vectors and contaminated soil and water. Diseases that are transmitted from animals to humans, either through direct contact with the animal or a contaminated surface or water, through ingestion of animal products (including meat and milk) or through insect transmission from an animal are called zoonotic (pronounced ZO-oh-NOT-ik or zoo-NOT-ik) diseases. Insects such as mosquitoes, ticks, flies, fleas or mites serve as vectors, capable of transmitting infection from an infected animal to another animal or a person.
Tick-borne diseases pose a hazard to both hunters and their dogs. They are usually transmitted to people through tick bites, but skin contact with the internal fluids of infected ticks also poses a risk of infection. Cases of tick-borne diseases, such as anaplasmosis, ehrlichiosis, Rocky Mountain Spotted Fever (RMSF) and others, have increased in the last decade. These diseases can be fatal. The symptoms of these diseases can be somewhat vague, making it difficult for physicians to diagnose the disease until it has become more severe. Hunters and their dogs are especially vulnerable to tick-borne diseases because of time spent in tick-infested environments. Preventing tick bites is the single most important step in preventing tick-borne diseases.
The following guidelines are recommended for hunters and their dogs to avoid tick-borne diseases:
To protect hunting dogs, hunters should consult their veterinarian, but basic guidelines include:
People involved in outdoor activities, such as hunters, are naturally more exposed to the threat of being bit by mosquitoes that can carry diseases such as West Nile virus and encephalitis viruses. For protection against mosquito-borne diseases, hunters should always:
Anaplasmosis is a tick-borne disease caused by the Anaplasma phagocytophilum bacteria (and less commonly by Anaplasma platys). It is spread by tick bites, primarily by the blacklegged and western blacklegged ticks.
Anaplasmosis is a reportable disease—- this means that health care providers and laboratories that diagnose cases of laboratory-confirmed anaplasmosis are required to report those cases to their local or state health departments, which in turn report the cases to CDC. In 2008, 1,009 cases of anaplasmosis were reported in the United States; the majority of the cases were reported in the eastern and Central U.S. The bacteria is considered endemic (established in the environment) in the upper Midwest, East and Northeast regions of the United States, as well as the Western coastal regions.
Symptoms of anaplasmosis in humans generally appear 5-21 days after a bite from an infected tick, and include headaches, fever, chills and muscle aches, and may be confused with flu symptoms. While some people may only experience mild symptoms and recover without medical attention, elderly or immunocompromised people may develop a more severe illness.
Dogs with anaplasmosis may show signs of lameness and joint pain, and some may also develop vomiting, diarrhea, coughing or labored breathing. It can be difficult to distinguish anaplasmosis from Lyme disease because the signs of disease are very similar and they occur in essentially the same areas of the country.
As with all tick-borne diseases, preventing tick bites is essential to preventing the disease.
There are many different strains of the avian influenza virus, most of which are considered of "low pathogenicity" (less likely to cause disease) and are not zoonotic. Worldwide, the highly pathogenic H5N1 strain of avian flu has received much attention in the media because of its ability to infect people who come in close contact with infected birds; H5N1 has not yet been detected in wild or domestic birds in North America to date, but precautions are highly recommended for hunters to reduce the risk of contracting any wildlife disease.
A 2006 report of 39 bird hunters and 68 wildlife professionals in Iowa found antibodies to a strain of avian influenza virus in the blood of one of the hunters and two of the wildlife professionals, indicating past exposure to a less common (and less infectious) type of avian flu. Although it involved a small number of test subjects, this study suggests that human exposure to avian influenza virus when handling wild waterfowl may occur more commonly than expected, and these fowl are capable of transmitting the disease to humans. The investigators did not determine if any of the people had become ill as a result of the virus. The study's results suggest that handling wild waterfowl, especially ducks, may be a risk factor for direct transmission of avian influenza virus to humans. (Gill 2006 EID)
Infection with the avian influenza virus may not cause illness at all, or may cause flu-like symptoms. Illness in dogs due to avian influenza has not been reported.
Babesiosis is a relatively unknown, malaria-like disease that is caused by Babesia parasites. It is transmitted by ticks – the same species of ticks that can carry Lyme disease and ehrlichiosis. It can also be transmitted by blood transfusion from an infected blood donor.
It is found mainly in Northeastern states, as well as Minnesota, Wisconsin and Washington state. Symptoms are flu-like and it can be difficult to diagnose.
Babesiosis in dogs can also be difficult to diagnose because of the variety of signs that may be observed. Infected dogs may appear normal, or they might suddenly go into shock from rapid destruction of their blood cells – these dogs show signs of fever, weakness, depression, swollen lymph nodes and very pale gums.
Brucellosis is most commonly caused by the Brucella abortus or the Brucella suis bacteria. Bison, elk, reindeer and caribou can become infected with the bacteria and develop brucellosis, but their role in transmission of the infections to livestock remains under debate. Brucellosis is one of the most serious diseases of livestock, can cause significant economic losses in production, and can infect people. As a result, the United States Department of Agriculture's Animal and Plant Health Inspection Service developed a brucellosis eradication program to eliminate the disease from our nation's herds. Controversy continues in the Greater Yellowstone Ecosystem regarding what role the bison and/or elk that wander outside Yellowstone National Park's borders play in infecting domestic cattle. Brucellosis is a reportable disease – this means that health care providers and laboratories that diagnose cases of laboratory-confirmed brucellosis are required to report those cases to their local or state health departments, which in turn report the cases to CDC.
There was one suspected, but not confirmed, human case of brucellosis linked to the use of deer and elk urine as a scenting agent during hunting in 1996. Many of these wildlife lures consist of urine, ground-up scent glands, and various other ingredients that may be contaminated by bacteria. There is a possibility that disease organisms could be transmitted from infected animals to humans, so it is recommended to follow basic sanitary measures when handling these lures, including avoiding ingestion, inhalation or direct skin contact.
Currently, human brucellosis due to Brucella suis in the U.S. is primarily associated with exposure to infected feral (wild) boars/hogs. The U.S. Centers for Disease Control and Prevention (CDC) provides resources and precautions for feral pig hunters, including a brochure, poster, flyer and wallet card.
Hunters may become infected with the Brucella bacteria during the cleaning of carcasses. Protective equipment, such as gloves and protective eyewear, is recommended.
Brucellosis in dogs is more commonly caused by Brucella canis, which is generally not spread to humans. Contact with or ingestion of infected milk, fetal membranes (placenta) or aborted fetuses from infected animals can result in infection with B. abortus or B. suis. Infection with B. abortus or B. suis rarely causes signs of disease in dogs but can cause abortion in pregnant bitches. Dogs infected with B. abortus or B. suis can infect humans.
Campylobacteriosis is a disease caused by Camplyobacter jejuni or Campylobacter coli bacteria. It affects the intestinal tract and, in rare cases, the bloodstream. It is one of the most commonly reported causes of bacterial diarrhea.
Campylobacter bacteria are generally spread by eating or drinking contaminated food or water, unpasteurized milk, and by direct or indirect contact with stool from an infected person, animal or pet. Many animals, including pigs (including wild pigs), cattle, dogs, moose, hares and birds, can carry the bacteria in their intestines.
Most infected animals will not show signs of disease, but they can develop diarrhea.
CWD is a transmissible spongiform encephalopathy, in the same class of diseases as bovine spongiform encephalopathy (BSE – more commonly known as "mad cow disease"). These diseases are caused by prions, which are infectious proteins. The diseases affect the brain and spinal cord, causing signs such as weakness, incoordination and abnormal behavior. How CWD is spread from animal to animal is not fully understood, but it is believed to be transmitted through direct animal-to-animal contact or when an animal eats soil contaminated by saliva or manure from an infected animal. CWD prions have been found in elk antler velvet, suggesting a possible route of transmission from elk to elk.
To date, only 4 species are known to be naturally susceptible to CWD: mule deer, white-tailed deer, Shiras moose and Rocky Mountain elk.
Signs of a possibly infected animal include stumbling, lowered head, droopy ears, weakness, a wide stance (as if trying to balance themselves), excessive salivation and emaciation ("wasting").
Hunters need to be aware that many states ban importation of whole carcasses and animals from states in which CWD has been reported; in fact, some states have check stations at their borders. For more information about the regulations for each state, visit the USDA's CWD pages.
According to the U.S. Centers for Disease Control and Prevention (CDC), there is no current evidence that CWD passes to humans. However, simple cautionary measures should be taken by any hunter handling deer, moose and elk. To date, data from an ongoing multi-year study suggests CWD may not be spread to people through consumption of meat from infected animals; however, eating meat from an obviously ill animal is not recommended.
Hunters should check with the state fish and game agency about any reported outbreaks of CWD, and the following simple precautions should be taken when handling any deer, moose or elk:
To date, there is no evidence dogs can become infected with CWD. However, it is best to avoid feeding brain and spinal cord tissues from killed game to dogs.
Studies have demonstrated that CWD prions can be excreted in the saliva, urine and manure of infected animals. These findings have led to recommendations for bans of the use of deer urine to lure deer.
Cryptosporidiosis is an illness caused by a simple, one-celled parasite named Cryptosporidium (there are several different species of the parasite that are capable of infecting animals and people), which is shed in the stool of wild and domestic animals. Infection generally occurs by contact with the stool of infected animals, contaminated surfaces or by drinking water or eating uncooked food contaminated with stool from infected animals. People can also become infected by swimming in contaminated water.
Although some people may not become ill after being infected, the most common symptoms of infection are extreme diarrhea, along with stomach cramps, nausea, vomiting, fever, headache and decreased appetite. People with weakened immune systems can develop severe disease if infected with Cryptosporidium. Cryptosporidiosis is a reportable disease – this means that health care providers and laboratories that diagnose cases of laboratory-confirmed cryptosporidiosis are required to report those cases to their local or state health departments, which in turn report the cases to the U.S. Centers for Disease Control and Prevention (CDC).
The best way to prevent infection is by using good hygiene. Avoid drinking untreated water; water can be made safe by heating it to a rolling boil for at least 1 minute or by using a filter that has an absolute pore size of 1 micron (pt) or smaller, or has been NSF rated for "cyst removal."
Infected persons can shed the organism in the stool for several weeks after infection, emphasizing the need for good hygiene.
Dogs can become infected with Cryptosporidium but generally do not show signs of illness. Mild diarrhea may develop. To date, there is little evidence that dogs can readily infect their owners with Cryptosporidium; however, proper hygiene is always recommended when handling dog stool.
Deer Parapoxvirus has been reported in red deer in New Zealand, but human infections have occurred in the United States. The virus is related to the orf virus, which affects sheep and goats, and the pseudocowpox virus, which affects cattle. The deer parapoxvirus causes scabby, crusty lesions on the muzzle, lips, face, ears, neck and antlers of affected deer.
There have been two confirmed cases of deer parapoxvirus infection in humans in the U.S., both of whom were deer hunters on the East Coast of the U.S. Both patients had nicked their fingers while dressing the deer carcasses and later developed pox lesions (scabby crusts) on their hands. One hunter also developed swollen lymph nodes. Both hunters reported that the deer had not shown any signs of illness at the time they were dressed.
The CDC continues to investigate deer parapoxvirus cases in the U.S. More information will be provided as it is obtained.
Hunters and their dogs can be infected by several species of tapeworms. Echinococcus multilocularis infects rodents (including field mice), and coyotes, wolves, foxes and dogs can become infected by eating infected rodents; the worms develop in the animal's intestines, and their eggs can infect people who come into contact with the infected animal's stool (or anything, including the animal's fur, that is contaminated with stool).
Echinococcus granulosus tends to cycle between canine species (coyotes, foxes, wolves, dogs, etc.) and larger grazing animals (sheep, goats, cattle, deer, elk, moose, caribou, etc.). Hunting dogs can become infected when they eat infected organs; the worms grow inside the dog's intestines and begin to shed eggs that pass in the stool and can continue the cycle of infection. Infected dogs do not usually show any signs of disease.
Although rare, hydatid tapeworms can be transmitted to humans from dogs, and the eggs eventually grow into cysts in the lungs, liver or other internal organs. These cysts can cause permanent damage.
Ehrlichiosis is a disease caused by bacteria that belong to the Ehrlichia species. There are several types of the bacteria that can cause illness. The disease is transmitted via the bite of an infected tick. It is a reportable disease – this means that health care providers and laboratories that diagnose cases of laboratory-confirmed ehrlichiosis are required to report those cases to their local or state health departments, which in turn report the cases to the CDC.
Symptoms usually occur within 1 to 3 weeks after exposure and can range from mild to severe. Common symptoms include fever, muscle pain, headache and chills. Occasionally, symptoms may include nausea/vomiting, a sharp drop in weight, mental confusion, cough and skin rash.
In dogs, the disease has 3 distinct phases. During the initial phase of infection, which generally lasts 1 to 3 weeks, the signs are nonspecific and include fever, loss of appetite, weight loss, depression and swollen lymph nodes. If the disease is not detected or treated during the initial phase, the dog may again appear normal. Chronic infection can develop, however, and can be life-threatening. Signs of severe ehrlichiosis include dramatic weight loss and loss of muscle tone, swollen lymph nodes, high fever, and bleeding.
Equine encephalitis viruses, including the Eastern equine encephalitis virus (EEE), Western equine encephalitis virus (WEE) and Venezuelan equine encephalitis virus (VEE), are transmitted by mosquitoes. As with West Nile Virus (WNV), the reservoir hosts for the encephalitis viruses are primarily wild birds.
Human infection with encephalitis viruses often causes symptoms such as fever, flu-like illness, muscle pain, vomiting and neurologic signs including seizures and convulsions. Infection with equine encephalitis viruses can be fatal. Infection with any of the equine encephalitis viruses is a reportable disease – this means that health care providers and laboratories that diagnose cases of laboratory-confirmed encephalitis are required to report those cases to their local or state health departments, which in turn report the cases to the CDC.
Although dogs can become infected with the viruses (particularly VEE), they do not usually develop illness.
Escherichia coli, or E.coli, is a bacteria that causes diarrhea and stomach pain in people and is the leading cause of hemolytic uremic syndrome, a rare kidney disorder that can cause kidney failure. Many types of E.coli are harmless, but certain types can cause severe disease.
Although most cases of E. coli infection come from eating contaminated beef or drinking unpasteurized, contaminated milk products, it is possible for white-tailed deer to become infected when they graze in cow pastures contaminated with the bacteria. Disease-causing E.coli has been found in cattle, goats, sheep, deer, elk, pigs and birds. Infection can also occur if a person drinks or swims in contaminated water. The bacteria are spread through fecal-oral transmission; an infected person or animal sheds the bacteria in their stool, and others are infected by accidentally eating the bacteria after they have touched a contaminated surface or had contact with infected stool. The bacteria are invisible to the naked eye, and people can become infected even if they don't see the contamination.
Dogs can become infected with E. coli. Intestinal infection often causes diarrhea and abdominal pain. E. coli infection in dogs can also cause urinary tract infections, uterine infections, ear infections and other problems.
Because the bacteria live in the animal's intestines, shooting a deer through its abdomen can increase the risk of contamination of the muscle (meat) by the intestinal fluids. The risk of infection is also related to how the carcass is handled, dressed, processed, preserved, stored and cooked.
Giardiasis is caused by infection with a microscopic parasite called Giardia duodenalis. The parasite is shed in the stool of infected wild and domestic animals. Infection generally occurs by contact with the stool of infected animals, contaminated surfaces or by drinking water or eating uncooked food contaminated with stool from infected animals. People can also become infected by swimming in contaminated water.
Although some people may not become ill after being infected, the most common symptoms of infection are diarrhea with "greasy" stools, along with gas, stomach cramps, nausea, vomiting, fever, and decreased appetite. It may take up to 1-2 weeks for these symptoms to occur, and illness may last 2-6 weeks. People with weakened immune systems can develop severe disease if infected with Giardia.
Dogs can become infected with Giardia but generally do not show signs of illness. Mild diarrhea may develop. The risk is very low that dogs can readily infect their owners with Giardia; however, proper hygiene is always recommended when handling dog stool.
Hantaviruses have worldwide distribution. Rodents (such as deer mice) are the natural hosts for these viruses. The viruses can be found in the rodents' urine, feces, and saliva, and when these substances have been deposited and dried, the viruses can become airborne and infect humans when they breathe in the airborne particles. Another way to get infected, although not as common, is via a rodent bite or drinking or eating food or water contaminated by rodents. Hantavirus pulmonary syndrome (respiratory disease due to hantavirus infection) is a reportable disease – - this means that health care providers and laboratories that diagnose cases of laboratory-confirmed hantavirus infection are required to report those cases to their local or state health departments, which in turn report the cases to the CDC.
The illness that develops in humans depends on the type of hantavirus. There is a severe illness known as hantavirus pulmonary illness that was first reported in the Southwestern U.S. in the early 1990s. This syndrome starts with fever, body aches, headache, nausea, vomiting, diarrhea and a dry cough. The major symptoms that indicate more serious illness are shortness of breath and difficulty breathing. This may lead to respiratory failure (which happens about 4 days after the symptoms first appear), when the lungs fill up with fluid and results in death in about 50% of infected patients.
Preventive measures to reduce the risk of hantavirus infection include:
To date, hantavirus infections in dogs have not been reported.
Leptospirosis is caused by Leptospira bacteria. The bacteria are found worldwide. Many species of both wildlife and domestic animals can spread leptospirosis. It is transmitted through an infected animal's urine.
Hunters and their dogs become exposed to Leptospira bacteria when they wade in contaminated waters or swamps; walk through contaminated soil, mud and wet plants; by direct contact with infected animals; or by eating food or meat or drinking water contaminated with the bacteria. The bacteria can also infect people and their dogs through open wounds or if contaminated water or food comes into contact with mucous membranes (e.g., linings of the nose, mouth and eyes). Person-to-person transmission is rare.
Symptoms of leptospirosis in humans range from mild to severe. The symptoms usually appear 5-14 days after infection, with a mild fever, chills, muscle ache and headache. Symptoms may progress to abdominal pain, vomiting, diarrhea and skin rash. The most severe cases develop liver and kidney problems, heart dysfunction and mental confusion. These severe cases are more common in older people and can result in death.
The signs of leptospirosis in dogs vary and can be vague. Infected dogs might not show any signs of disease, or they may exhibit fever, vomiting, diarrhea, loss of appetite, weakness and depression, stiffness or infertility. Younger animals may be more likely to develop the disease.
Lyme disease is an illness caused by a bacterium, Borrelia burgdorferi, which is a "spirochete" (a bacterium that has a worm-like, spiral-shaped form). Deer ticks are the primary carriers of the bacteria.
In humans, often the earliest indication of infection is a "bullseye" rash at the site of the tick bite – so named because it resembles a target. As the infection develops, symptoms include fever, headache, fatigue, and muscle and joint pain. The disease can progress to cause chronic joint problems as well as heart and neurological problems. Lyme disease is not contagious from one person to another. Lyme disease is a reportable disease – this means that health care providers and laboratories that diagnose cases of laboratory-confirmed Lyme disease are required to report those cases to their local or state health departments, which in turn report the cases to the CDC.
Dogs infected with Lyme disease may not show signs for 2-5 months, at which time they usually develop fever, loss of appetite and lameness. It can be difficult to distinguish Lyme disease from anaplasmosis because the signs of disease are very similar, and they occur in essentially the same areas of the country.
Because it can be a difficult disease to diagnose, it is best to prevent infection by taking appropriate measures to prevent tick bites.
Plague is a disease caused by infection with Yersinia pestis bacteria, the same bacteria responsible for the "Black Death" that killed millions of people in the 1300s. The bacteria is still present in the environment in several regions of the nation, and the disease has recently been reported in mountain lions, rodents, rabbits, squirrels and other carnivorous animals. There are two common forms of plague – pneumonic plague, which involves the lungs and is more life-threatening; and bubonic plague, which is more common and less severe.
Plague can be transmitted to hunters and their dogs through bites of infected fleas or by direct contact with infected animal tissues when skinning or handling wild game. The highest risks of exposures come from infected blood and tissues. The disease is more commonly found in areas with high populations of prairie dogs or other rodents.
The symptoms of plague in humans include high fever, chills, weakness, headache, nausea, and often a painful enlarged lymph node (in the groin area or armpit). Plague is a reportable disease – this means that health care providers and laboratories that diagnose cases of laboratory-confirmed plague are required to report those cases to their local or state health departments, which in turn report the cases to the CDC.
Signs of infection in dogs are usually open sores around the head and neck, and a veterinarian should be consulted immediately. Do not allow hunting dogs or pets near established prairie dog colonies, because they may become infested with plague-carrying fleas and may become ill and/or bring the infected fleas into your home or onto your property, increasing the risk of human infection.
Q fever is a disease caused by the Coxiella burnetii bacteria. Cattle, sheep and goats are the primary reservoirs of C. burnetii, but cats, dogs, some wild mammals, birds and ticks are also natural reservoirs. The bacteria can be present in high numbers in the birth tissues (e.g., amniotic fluid, placenta and uterus) of infected animals and in lower numbers from their milk, urine, vaginal mucus, semen and manure/feces. The nesting sites of infected animals pose a high risk for infection. The bacteria most often infects humans and animals through an aerosol route – as the infected fluids dry, the bacteria remains in the dust. Infection can also develop following ingestion of contaminated, unpasteurized dairy products.
Both hunters and hunting dogs can become infected with Q fever. In humans, Q fever is often mistaken for a flu or cold; symptoms include fever, chills, headache, muscle pain, weakness and severe sweats, usually lasting 2 weeks. There is a possibility of complications involving the lungs, nervous system or heart. Q fever is a reportable disease – this means that health care providers and laboratories that diagnose cases of laboratory-confirmed Q fever are required to report those cases to their local or state health departments, which in turn report the cases to the CDC.
Many animals do not exhibit signs of the disease, but infected dogs can shed the bacteria in their urine or milk and serve as sources of infection of their owners.
Rabies is caused by different variants (similar to strains) of the rabies virus. The virus is transmitted primarily through bites and causes severe damage to the brain. Non-bite transmission of the rabies virus is very rare but can occur through scratches, abrasions, open wounds or mucous membranes contaminated with saliva or other potentially infectious material (such as brain tissue) from a rabid animal. Once clinical signs of rabies are observed, it is 100% fatal in animals and almost 100% fatal in humans.
In the United States, rabies is most common in raccoons, foxes, skunks and bats. The virus can infect any mammal, and there are documented cases of rabies in many wildlife and domestic species.
The symptoms of human rabies cases can vary, but early symptoms may include fever, headache, sore throat, tingling at the site of the bite and fatigue. As the disease progresses, infected humans can develop disorientation, paralysis, hallucinations, seizures, coma and death.
Rabies is a reportable disease – this means that health care providers and laboratories that diagnose cases of laboratory-confirmed rabies are required to report those cases to their local or state health departments, which in turn report the cases to the CDC. Suspected cases are also reportable to local and state health departments.
The first clinical signs of rabies seen in animals are usually nonspecific and may include lethargy, vomiting, fever and anorexia (loss of appetite). Signs rapidly progress and in days may include restlessness, confusion/disorientation, ataxia/incoordination, lameness, hypersalivation, weakness, paralysis, aggression, self mutilation, tremors, seizures, choking, or difficulty breathing or swallowing. Contrary to popular belief, rabid dogs are more likely to exhibit lethargy and paralysis than aggression.
Common sense guidelines for avoiding exposure to rabies include:
Do not take any extraordinary risks if you do see a potentially rabid animal – the presence of a potentially rabid animal should be reported to the proper authorities. If it is necessary to kill the animal before the proper authorities can be contacted or can arrive, avoid killing the animal by a head shot or causing any trauma to the animal's head – the brain must be intact for rabies to be confirmed. Do not handle any potentially rabid animals without proper protection (such as gloves), and avoid any contact with the animal's mouth, eyes and nose.
If you are bitten or come into physical contact (scratches or direct contact with the brain or saliva) with a potentially rabid animal, immediately wash the area with soap and water. Contact your physician immediately; rabies is almost always fatal if not treated immediately. Also contact the local or state health department.
View the AVMA's World Rabies Day page for more information.
The raccoon roundworm, Baylisascaris procyonis, is a large parasitic worm that lives in the intestines of raccoons, although over 90 species of mammals, including dogs, rabbits, rodents, birds and humans can become infected with it. It is a common parasite in raccoons and has been reported throughout the U.S. (mainly in the Northeast, midAtlantic, Midwest and West Coast states).
The adult worms shed millions of microscopic eggs that are passed through the infected animal's stool into the soil, where the eggs can survive for months or even years. Humans become infected through accidentally eating eggs in contaminated food or water, or through contact with raccoon feces or objects that have been contaminated with raccoon feces. Because raccoons tend to use specific "latrine" areas, there can be a very high number of infective eggs in the soil in these areas.
While the worm does not cause harm to raccoons, it can cause serious illness in humans. Symptoms include nausea, lethargy, liver enlargement and loss of muscle control, eventually resulting in coma and blindness. Deaths are rare, but permanent liver, eye or brain damage can occur.
Dogs can be infected with the raccoon roundworm by contact with the stool of infected raccoons (or soil or water contaminated by the stool) or by contact with (or eating) the intestinal contents of an infected raccoon. Signs of illness include fatigue, blindness, incoordination and other nervous system problems. It is possible that an infected dog could shed eggs that can infect its owner. It has been suggested that monthly heartworm preventives may decrease the risk of infection in dogs.
Rocky Mountain Spotted Fever (RMSF) is caused by the Rickettsia ricketsii bacteria and can be transmitted to hunters via tick bites. Person-to-person transmission does not occur.
Symptoms of RMSF usually appear within 3 to 14 days after the bite of an infected tick, with moderate to high fever (which may last for 2 to 3 weeks), severe headache, fatigue, muscle aches, chills and skin rash. The rash looks like blood spots or heavy freckles, explaining the "spotted fever" part of the name, and begins on the legs and arms and may include the soles of the feet and palms of the hands, spreading rapidly to the rest of the body. It is important to note that not everyone who has RMSF will develop a rash. RMSF is a reportable disease – this means that health care providers and laboratories that diagnose cases of laboratory-confirmed RMSF are required to report those cases to their local or state health departments, which in turn report the cases to the CDC.
In dogs, the first sign observed is usually a high fever, occurring 4-5 days after a bite from an infected tick. Blood spots (pinpoint or larger in size) may be seen on the lips, gums and nonhaired (or shorthaired) areas of the dog's skin. The dog's legs may swell, as well as the lips, ears and sheath. In the late stages of the disease, or sometimes during recovery, the damage in the legs can be severe enough that sloughing of the skin and tissues can occur.
There are new spotted fevers being detected worldwide that are similar to RMSF, and these are also transferred via tick bites. In the United States, the most frequently diagnosed rickettsial infection associated with hunters returning from international travel is African tick bite fever.
Salmonellosis is a bacterial infection caused by Salmonella species. There are many Salmonella species that can cause infection and illness. Many species of animals, including pets, livestock, reptiles, birds and wildlife, can be infected and can spread Salmonella.
These bacteria usually infect the intestinal tract but also can be found in urine, blood or in other body tissues.
Salmonella bacteria are spread through fecal-oral transmission; an infected person or animal sheds the bacteria in their stool, and others are infected by accidentally eating the bacteria after they have touched a contaminated surface or have had contact with infected stool. The bacteria are invisible to the naked eye, and people can become infected even if they don't see the contamination.
Symptoms in humans and animals may include mild to severe diarrhea, stomach pain, fever and vomiting. Infections in the bloodstream are rare but potentially can be very dangerous. Salmonellosis is a reportable disease – this means that health care providers and laboratories that diagnose cases of laboratory-confirmed salmonellosis are required to report those cases to their local or state health departments, which in turn report the cases to the CDC.
Sarcoptic mange is a skin disease caused by sarcoptic mange mites, which are found nationwide. This mange can be found in feral swine, foxes, coyotes and wolves, as well as in big game (including moose, elk, caribou, lions and water buffalo). It is spread by contact from animal to animal or from an infected environment to an animal and becomes more common when animal populations are high and contact is more likely.
Sarcoptic mange mites burrow through the top layer of the dog's skin and cause intense itching. Clinical signs include generalized hair loss, a skin rash and crusting. Skin infections may develop secondary to the intense irritation. It usually appears first in the hind end and tail regions, and gradually expands up along the back to the head.
People who come in close contact with an affected dog may develop a skin rash and should see their physician. When hunters come across an infected carcass, they should burn or bury the carcass, and as always, when dealing with a wild animal carcass, gloves should be worn and the workplace disinfected afterwards. If a hunting dog comes in contact with a mange-infested carcass, prompt use of mite-killing topical products can prevent infection. Consult your veterinarian for a product recommendation.
Toxoplasmosis is caused by Toxoplasma gondii, a single-celled parasite.
A person can get toxoplasmosis by eating raw or undercooked meat, especially venison, lamb or pork, or from consuming unpasteurized milk or milk products. Humans can also get toxoplasmosis by consuming food, water, or soil contaminated with cat feces.
Healthy people rarely develop toxoplasmosis. If illness occurs, symptoms include fever and swollen lymph nodes. Eye problems can also occur. Less common symptoms include skin rash, fatigue and muscle pain, and serious cases (usually in persons with weakened immune systems) develop pneumonia and central nervous system (brain or spinal cord) disorders. If a pregnant woman becomes infected, it may result in severe birth defects or death of the baby.
Dogs can become infected with T. gondii, but it is uncommon for them to develop illness. Illness is more likely to develop in dogs with weakened immune systems, and the signs of illness include incoordination, weakness and seizures.
Preventive measures include thoroughly cooking meat and using proper food hygiene (washing hands and utensils after contact with raw food, washing fruit before eating it, etc.) Avoid eating raw eggs or unpasteurized milk.
Trichinellosis, also called trichinosis, is caused by a parasite called Trichinella spiralis. Unlike many other parasites that can infect people, this parasite lives in the muscle tissue of animals (including the tongue and diaphragm, both of which are specialized muscles). Because the meat of the animal is actually its muscle tissue, the parasite can infect people who eat the meat of an infected animal.
T. spiralis is found worldwide, in a wide range of birds and mammals. In North America, it is common in the cougar and the grizzly bear but has also been reported in black bear, wolf, red fox, coyote, lynx and wild hogs.
Although it is considered to be a relatively minor disease in wildlife, causing only minor behavioral changes (such as less activity, increased predation and decreased reproductive activity), trichinellosis can be fatal in humans. As they burrow into the muscle cells, the muscle cells serve to "protect" the larvae, so they can live for years in an animal. They only become reactivated when the meat they have been living in is eaten by a carnivore or hunter.
Symptoms include stomach pain and fever, muscle aches, and swelling around the eyes. Thirst, sweating, chills, weakness and fatigue may follow. Chest pain can occur if the parasite has infected the diaphragm. The onset of illness depends on the number of parasites and the amount of meat eaten. Trichinellosis is a reportable disease—this means that health care providers and laboratories that diagnose cases of laboratory-confirmed trichinellosis are required to report those cases to their local or state health departments, which in turn report the cases to the CDC.
Trichinella spiralis can infect dogs that eat raw meat infected with the parasite. Infected dogs may not show any signs of illness or they may develop mild diarrhea.
The main course of prevention against trichinellosis is the proper handling and cooking of meat. Smoking, freezing or curing game meat may kill the larvae, but this is not the case for all strains of Trichinella. Low-temperature smoking will not kill the larvae. In addition, livestock should never be served the meat or offal of wildlife.
Mycobacterium bovis, a bacteria, causes bovine tuberculosis (TB). This is a different disease and different bacteria than human tuberculosis. M. bovis infection has been reported in wild boars, white-tailed deer, mule deer, elk, bison, badgers, possums, water buffalo, wapiti and other species. M. bovis poses a minimal risk to people, but can easily infect domestic cattle herds. For this reason, there are federal and state eradication programs. When field dressing an elk or deer, hunters should look for tan or yellow pea-sized lumps in the wall of the rib cage or in the lungs. If these lumps are present, the hunter should immediately stop handling the carcass, attach a game tag, and contact the local fish and wildlife agency.
Mycobacterium tuberculosis, the cause of human TB, has been reported in meerkats and mongoose in South Africa, but the significance of free-ranging wildlife in the spread of human TB remains unknown.
Tuberculosis is a reportable disease – this means that health care providers and laboratories that diagnose cases of laboratory-confirmed tuberculosis are required to report those cases to their local or state health departments, which in turn report the cases to the CDC.
Tularemia is caused by infection with Francisella tularensis bacteria, commonly found in the United States in rabbits, squirrels, muskrats, beavers, prairie dogs, cats, bobcats, deer and sheep. Rabbits are the most common source of tularemia in the United States. It is a potentially fatal disease. It can be spread to animals and people by deerflies and other insects. Tularemia is a reportable disease—this means that health care providers and laboratories that diagnose cases of laboratory-confirmed tularemia are required to report those cases to their local or state health departments, which in turn report the cases to the CDC.
Historically, people that work outdoors (landscapers, etc.) have been more likely to be infected with tularemia. Hunters are at risk of exposure because of the amount of time they spend outdoors and in their handling of game species prone to infection.
Routes of exposure may include:
Less common routes may include:
Symptoms of tularemia in people usually include skin lesions and swollen glands. If the infection is caused by eating infected meat, symptoms may include sore throat, intestinal pain, diarrhea and vomiting. Inhalation of the bacteria may produce a fever or may also cause a pneumonia-like illness. While the symptoms may appear anywhere from 2-10 days after exposure, they usually appear after 3 days. Simple measures can be taken to minimize the risk of tularemia, including the following:
Dogs can be affected by tularemia, but the signs observed may be mild and nonspecific. The signs that may be observed are related to the mode of transmission and include fever, depression, mucopurulent (mucus with pus) discharge from the nose and/or eyes, pustules at the sites of contact, swollen lymph nodes, and loss of appetite. In most cases, the disease is self-limiting with supportive treatment.
African mosquitoes carrying the West Nile virus (WNV) first arrived in New York City in 1999. The virus has since spread throughout North America. The virus infects wild birds, and mosquitoes then transfer the virus to other animals and to humans.
Approximately 20% of people who are exposed to the virus via mosquito bites develop symptoms. Approximately 1% develop encephalitis (inflammation of the brain) or meningitis (inflammation of the linings of the brain or spinal cord) that can lead to death. West Nile Virus infection is a reportable disease – this means that health care providers and laboratories that diagnose cases of laboratory-confirmed West Nile Virus infecitons are required to report those cases to their local or state health departments, which in turn report the cases to the CDC.
Sudden bird die-offs can indicate the presence of West Nile virus in the area. Hunters should report any noticeable increase in dead birds to state health department or state wildlife agency.
Hunters should avoid handling dead birds they encounter that have not been shot during the hunt. Follow the state or local health department's instructions regarding what to do with the dead bird. If instructed to dispose of the bird, hunters should use gloves or protect their hands with a plastic bag to place the bird carcass in a garbage bag and dispose of it in the trash.
Dogs are not likely to show signs of disease when infected with the West Nile virus.
Many of the same risks associated with hunting in North America may also be present worldwide, but there are additional risks with international hunting. These risks include diseases unique to the area. It is recommended that hunters find out the health situation in each destination country as they are determining where they will hunt. The World Health Organization's (WHO) International travel and health site provides basic information, as well as advisories on safe food, health regulations and other topics. The U.S. Centers for Disease Control and Prevention also maintains a Traveler's Health section with advice and information.
Below are some of the zoonotic diseases unique to international destinations.
Chikungunya fever is caused by the chikungunya virus, which is transmitted to humans via the bite of an infected mosquito.
Big game hunters in Africa and Asia need to be especially aware of this virus, as it has been the cause of many epidemics in both these continents. The mosquito that carries the virus, Aedes aegypti, is known to be an aggressive daytime biter that appears to be attracted to humans. This mosquito also transmits the virus between humans. It is suspected that monkeys and possibly other wild animals serve as reservoirs for this virus. Lately, the Aedes albopictus mosquito (Asian tiger mosquito) has also been recorded as transmitting the virus to humans in Asia, Africa and Europe. There are also certain African forest-dwelling mosquitoes that have been found to be infected with the virus.
Rarely, a person can have chikungunya without any symptoms. A primary symptom of chikungunya is severe joint pain. It may progress to a more serious illness, with fever, headache, fatigue, nausea, vomiting and rash. Acute chikungunya usually lasts from a few days to several weeks, but some people can experience fatigue or joint pain for a longer period of time.
To date, chikungunya infection in dogs has not been reported.
Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne disease caused by a Nairovirus. It is found in Eastern Europe, Africa, Northwest China, Central Asia, the Middle East, India, the Mediterranean and Southern Europe. Ixodid (hard) ticks are the transmitters of the CCHF virus. Both wild and domestic animals, such as cattle, goats, sheep and hares, may be infected with these ticks. Transmission to hunters may occur through tick bites or the infected blood of an animal. CCHF can be transmitted from one infected human to another by contact with infected blood or body fluids. The first signs of CCHF are sudden, with headache, high fever, back and joint pain, stomach distress, red eyes, flushed face, sore throat, and red spots in the mouth. Rare symptoms include jaundice, and in severe cases there are mood swings and changes in vision and hearing. Severe bruising and nosebleeds also occur.
Rift Valley Fever (RVF) is caused by the Rift Valley Fever virus (RVFV), a mosquito-borne virus that has been associated with widespread outbreaks of severe disease in livestock and humans in Africa, and more recently, the Arabian peninsula. Infections in livestock cause 10-20% deaths in adults and 100% in newborns. Infections in humans usually consist of mild illness, but in 1-2% of human cases, RVF can progress to liver problems, blindness, severe bleeding and death. Epidemics always occur during heavy rainfall seasons, when the infected mosquitoes are present in high numbers. RVF is considered a serious threat, and recent studies, while not yet confirmed, have indicated that certain wildlife species may be reservoirs for this virus between outbreaks, including African buffalo, lesser kudu, black rhinos, white rhinos and impala. These studies also suggest that, during a RVF outbreak in a region, any wildlife meat, if not properly handled, may pass the RVF infection on to humans.
We would like to thank the AVMA's Committee on Environmental Issues for their participation and advice on this project.
U.S. Department of Agriculture (USDA)Fact sheets: Food Safety while Hiking, Camping & BoatingFact sheet: Roasting Those "Other" Holiday MeatsFreezing and Food SafetySafe food handling
Centers for Disease Control and Prevention (CDC)Avian influenza among waterfowl hunters and wildlife professionalsProtect yourself from tick bitesTickborne rickettsial diseasesInsect repellentsWildlife, Exotic Pets, and Emerging ZoonosesTraveler's Health pages
Wisconsin Department of Agriculture, Trade, and Consumer ProtectionCommon Sense: Handling and processing venison
This information has been prepared as a service by the American Veterinary Medical Association. Redistribution is acceptable, but the document's original content and format must be maintained, and its source must be prominently identified. Please contact Dr. Kimberly May (800.248.2862, ext 6667) with questions or comments.