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Health Concerns to be Aware of When Working With Wildlife

(a.k.a. - Zoonoses)

 

from The Humane Control of Wildlife in Cities & Towns by the Humane Society of the United States

 

Zoonotic diseases are those diseases shared by animals and humans. Approximately 150 zoonotic diseases are known to exist. Wildlife serves as a reservoir for many diseases common to domestic animals and humans. Persons working with wildlife should be alert to the potential for disease transmission from animals.

 

Neither animal handlers nor the general public have reason to be alarmed or frightened, but everyone should respect the potential for disease transmission and use sound preventive measures. Generally, disease is more easily prevented than treated. This discussion reviews common zoonotic diseases, including those ailments that are often erroneously cited as being closely linked to wildlife. Many zoonotic diseases are so common in nature, so rare in humans, or so mild in their symptoms, that wild animals pose a minimal health risk to people.

 

The diseases listed are grouped according to their causative agent or mode of transmission.

 


CONTENTS:

 

BACTERIAL DISEASES

          Leptospirosis

          Brucellosis

          Bubonic Plague

          Psittacosis

          Salmonellosis

          Tetanus

          Tularemia

         

MYCOTIC DISEASES

          Aspergillosis

          Histoplasmosis

 

VIRAL DISEASES

Rabies

 

HELMINTH PARASITIC DISEASES

          Baylisascaris procyonis

 

PROTOZOAL DISEASES

          Giardiasis

          Toxoplasmosis

 

TICK-BORNE DISEASES

          Lyme disease

          Rocky Mountain Spotted Fever

 

PHYSICAL TRAUMA

 


 

BACTERIAL DISEASES

Most of the bacteria that cause disease in wildlife also cause disease in man. There are several important routes of disease transmission. The contamination of neglected minor wounds, abrasions, and skin lesions where the skin is broken serve as common portals of entry for microorganisms. These infections are frequently caused by mixed groups of bacteria, but they usually involve Staphyloccocci and Streptococci. Another important mode of transmission is the contamination of mucous membranes, primarily the mouth, with feces or urine. Most of these infections can be prevented by establishing good personal hygiene habits, such as thorough hand washing and protecting open lesions on the hands and arms. It should be noted that even bruised areas will be more susceptible to secondary bacterial infections than normal skin.

 

LEPTOSPIROSIS

Infectious Agent:......Leptospira spp.

Host:.........................Skunks, raccoons, opossums, Norway rats, mice, and many other animals including domestic species.

Transmission:...........Bacterial penetration of abraded or lacerated skin by infected urine, contaminated food, water, or soil, or by direct contact with an infected animal. The organism can invade intact skin.

Symptoms:................In wild animals, the disease is usually unapparent except in marine mammals. The disease is relatively rare in humans. A mild form is characterized by fever, chills, nausea, malaise, and myalgia (muscle pain). In the severe state, it may appear as a meningitis.

Prevention:.................Good personal hygiene, particularly avoiding contact with urine of wild species.

 

BRUCELLOSIS (Undulant Fever)

Infectious Agent:......Brucella spp.

Host:.........................White-tailed deer, fox, raccoons, and many other animals.

Transmission:...........Contact with tissues, blood, urine, vaginal discharges, or fetuses of infected animals. Brucellosis is a highly contagious infection in many animals. It usually begins as a septicemia (blood infection) localizing in lymph nodes, spleen, reproductive organs, and joints where it can persist for long periods of time.

Prevention:.................Use protective gear, especially rubber gloves, when handling infected animals.

 

BUBONIC PLAGUE

Infectious Agent:......Yersinia pestis

Host:.........................Fleas; often found on rats and ground squirrels

Transmission:...........Flea bite. Wild rodents, rabbits, and mammals serve as the hosts to the fleas. The disease is endemic (indigenous) in the southwestern United States.

Symptoms:...............Wild rodents become infected but usually do not show clinical signs under normal conditions. The signs in animals are fever, pneumonia, and swollen lymph nodes. In humans, the disease is categorized into bubonic and pneumonic types. The bubonic form is characterized by a bacteremia and infected lymph nodes. Human mortality in untreated cases for this form of plague is 25-60%. The pneumonic form is characterized by an acute pneumonia and is rapidly fatal (1-3 days) if untreated (100%). Veterinarians have been killed by this disease.

Prevention:.................Active immunization may be necessary in endemic areas. Avoid contact with fleas. Rehabilitators should be careful in handling animals with fleas and should de-flea incoming animals.

 

PSITTACOSIS (Ornithosis, Chlamydiosis)

Infectious Agent:......Chlamydia psittaci

Host:.........................Birds (over 100 species including pigeons, raptors, and finches)

Transmission:...........Fecal-oral contamination and inhalation of dried discharges and droppings from birds. The infecting organism is present in nasal discharges, droppings, and tissues of infected birds. The droppings are the most common route by which the disease is transmitted to humans. It is commonly found in feral pigeons that appear healthy.

Symptoms:...............Signs in animals include decreased or no appetite, resulting in emaciation, lethargy, respiratory signs, and a greenish blood-tinged diarrhea. Conjunctivitis is common and varies in severity. The disease may be acute and consequently the animal may die with few signs of disease. Clinical signs in people include fever, headache, upper respiratory infection, and pneumonitis. Rehabilitators, veterinarians, and bird banders have been infected by the birds they handled.

Prevention:.................Transmission is through the inhalation of aerosolized feces, so it is particularly important not to allow build up of feces in enclosed areas. When entering into a potentially infected area (for example, a pigeon roost), wear a mask to prevent inhalation of dust from the droppings. Also, practice good personal hygiene.

 

SALMONELLOSIS

Infectious Agent:......Salmonella spp.

Host:.........................Birds and reptiles (most mammals also).

Transmission:...........Fecal contamination of mucous membranes (fecal/oral). Food, water, or surfaces may become contaminated. Salmonella gastroenteritis is probably the most common zoonotic disease of humans. It is estimated there are two million cases annually in the United States. The organism is commonly found in animals, especially birds and reptiles.

Symptoms:...............Signs in animals are often subclinical, but when present, include diarrhea, vomiting, and mild fever. The bacteria are shed for some time following infection. Many animals are persistent carriers. In humans, the disease usually produces a gastroenteritis (intestinal infection) accompanied by diarrhea and often abdominal pain. Dehydration is often a problem.

Prevention:.................Good personal hygiene.

 

TETANUS

Infectious Agent:......Clostriduim tetanii

Host:.........................No animal host.

Transmission:...........Contamination through breaks in the skin from penetrating or crushing wounds.

Symptoms:...............Tetanus is an acute disease caused by the toxins produced in the body by Clostridium tetanii. The disease is characterized by tonic spasms of the muscle groups of the jaw, neck, and back. Untreated, there is a 70 percent mortality rate.

Prevention:.................Vaccination with a primary series of three doses of tetanus toxoid and booster every ten years is highly effective. Acute wound-associated tetanus can be prevented by appropriate wound management, including active or passive immunization.

 

TULAREMIA (Rabbit Fever)

Infectious Agent:......Francisella tularensis

Host:.........................Rodents and lagomorphs (rabbits). Also included are over 100 species of mammals and 25 species of birds. It has been seen in fox, beaver, mice, and muskrats.

Transmission:...........Handling infected animals, contamination of cuts, mosquito/fly/tick bites, and by inhalation. It can also be spread by touching the conjunctiva of the eye with dirty hands from handling affected animals.

Symptoms:...............In humans, signs are flu-like with an ulcer forming on the skin at the site the organism entered, this is followed by enlargement of the lymph nodes; if ingested, vomiting and diarrhea are seen; if inhaled, pneumonia. Severe systemic disease can lead to headaches, myalgia, chills, and fever. Humans do die from this disease.

Prevention:.................Use rubber gloves when handling animals, especially rabbits; protection from ticks.

 


 

MYCOTIC DISEASES

These are diseases caused by fungi that are often found in the environment.

Often they are only a serious problem in people who are immunocompromised in some way.

 

ASPERGILLOSIS

Infectious Agent:......Aspergillus fumigatus

Host:.........................The fungus is ubiquitous (is found all over in our environment). Animal hosts in rehabilitation are generally wild birds such as raptors or waterfowl.

Transmission:...........While under stress in a captive facility, rehab animals are more likely to develop the fungal disease. They in turn shed the spores of the fungus and the workers may inhale them.

Symptoms:...............In birds, respiratory signs. Most healthy people have no trouble resisting infection. However, this is not true for anyone who has been debilitated by illness, other diseases, or has been on long term antibiotic, antimetabolite, or corticosteroid therapy.

Prevention:.................Good hygiene and good ventilation. At least 12 air exchanges per hour are recommended in any room where susceptible birds are housed. Waterfowl are not to be housed on wood shavings because the fungus will thrive in them when wet. Moldy grains and food stuffs are not fed or stored. Necropsies are performed with masks as are treatments on suspect patients. Spray necropsy birds down with a disinfectant to matt feathers and reduce aerosolized lint and debris.

 

HISTOPLASMOSIS

Infectious Agent:......Histoplasma capsulatum

Host:.........................Birds and bats

Transmission:...........Inhalation of infective spores. Histoplasma capsulatum is widely distributed throughout the United States. The Mississippi and Ohio River valleys are areas of high concentration. The organism thrives in the soil that has been enriched by the presence of decaying bird or bat droppings. It is most likely to be found in roost areas that had been established for a minimum of three to five years. The organism grows in the upper 1-2 inches of the soil. When combined with moisture, roost areas are exceptional for the growth of Histoplasma.

Symptoms:...............The disease is acquired through inhalation of airborne spores. Upon first-time contact, the person will become infected. The majority of people who become infected develop only mild respiratory infections and, once recovered, become somewhat resistant. More severe infections are encountered in heavily-contaminated environments. The acute disseminated form, most frequent in children, may result in death. Similar forms of the disease occur in skunks, rats, opossums, foxes, and other animals.

Prevention:..............Avoid accumulations of soil mixed with droppings from bats or birds. If occupation of such areas is necessary, use masks or a self-contained breathing apparatus. Always wear boots and properly bag clothing for washing. As a last resort, contaminated soil can be treated with a 3 percent solution of formalin to kill the spores, but such treatment will kill other organisms in the environment.


 

VIRAL DISEASES

Viruses are known to infect a wide range of hosts, including humans and wild animals. The usual mode of transmission and dissemination is through the direct contact or aerosol contact with others of their own species. Wildlife populations, such as waterfowl, experience epizootics (epidemics in wildlife) caused by viruses. Duck plague, or duck viral enteritis, may cause large die-offs in a localized area. People also experience viruses; for example, the upper respiratory viruses where epidemics are not uncommon. There are only a few viruses that are common to humans and wildlife; however, since they have no specific cure, they can be very serious.

 

RABIES (Hydrophobia) (Bite Wound Disease)

Infectious Agent:......Rhabdovirus

Host:.........................Any mammal, usually carnivores; in ND, highest incidence is in skunks, foxes, bats, and raccoons.

Transmission:...........Bite wounds, infected saliva in cuts or skin abrasions, aerosol in bat caves.

Symptoms:..............Rabies is almost always a fatal disease of mammals, including humans. The disease progresses from fever and malaise, to paresis and paralysis of the muscles, to delirium and convulsions and eventual death due to respiratory muscle paralysis. In animals, ANY abnormal behavior is cause for concern, especially a lack of fear of humans and normally nocturnal animals being out during the day. Domestic animals once formed the largest reservoir for the disease, but, since the 1960's, wildlife species, especially skunks, bats, fox, and raccoons, have taken over that distinction. In 1986, 5,551 cases of rabies were reported in the United States. Of these, 91 percent were from wildlife species. Rabbits and squirrels are rarely infected. Human deaths average two cases per year.

Treatment:.............. (note: once the disease has developed... there is NO treatment; this is a FATAL disease)
For humans ONLY: (animal treatment is NOT an option)

  1. Cleanse wound thoroughly with soap and flush immediately to mechanically remove the organism.

  2. SEE YOUR DOCTOR IMMEDIATELY!

Prevention:.................Since rabies is such a uniformly fatal disease, emphasis should be placed on disease prevention. People working with wildlife regularly should consider pre-exposure immunization. The best protection for you and the animal in your care is to avoid being bitten!

 


 

HELMINTH DISEASES (parasitic)

Helminths are worms. All species of wildlife carry their own complement of helminth intestinal parasites. Our domestic animals also have specific kinds of roundworms. There are two forms of disease produced by these parasites. Cutaneous larval migrans is a penetration of the skin with the parasite undergoing a localized migration in or just under the skin, creating an inflammatory reaction that is self-limiting. Visceral larval migrans occurs when the eggs of a parasite are ingested and further penetrate the intestinal tract, where they undergo a migration through the animal's organs. The amount and severity of the disease depend on the organs affected. Although only Baylisascaris infection is described below, any roundworm is capable of tissue migration. Therefore, handling of fecal matter should always be with the protection of gloves.

 

CUTANEOUS AND VISCERAL LARVAL MIGRANS

Infectious Agent:......Baylisascaris procyonis (Raccoon Roundworm) (others also, see above)

Transmission:...........Skin penetration, oral ingestion of eggs. The roundworm of raccoons is reported to infect at least 70 percent of raccoons in some areas. For the raccoon, it causes few problems. However, it can cause serious illness to other animals, including humans. The adult worms shed millions eggs per day, passing them in the host's feces.

Symptoms:...............If accidentally ingested by another species, humans included, the larvae hatch and penetrate through the intestine, migrating to many parts of the body. If these larvae migrate into the eye, brain, or spinal cord, there can be serious, irreversible consequences. Blindness, central nervous system disease, or death can result. Children have died due to this migrating parasite (due to their propensity to place objects in their mouth). In adults, eye problems are a more common result. Other species have roundworms that can sometimes penetrate the skin, causing a localized self-limiting skin irritation (Cutaneous larval migrans) in man.

Prevention:.................

  1. Avoid contact with feces, especially raccoon. Use disposable gloves whenever handling fecal matter and wear a mask if cleaning up an area with dried raccoon feces.

  2. Good personal hygiene in handling any wildlife species.

  3. Deworm all incoming raccoons with an effective antihelminthic drug such as Strongid-T suspension (Pfizer) every two weeks.

  4. Thoroughly clean and disinfect and cages, carriers, or areas occupied by raccoons. The ova are very resistant, however, to decontamination procedures. Recommended procedures are autoclaving, flaming with gasoline, propane, or fuel oil, boiling in lye water (1 Ib./20 gal. water).. Cages should NOT be used again for any other species (other animals may become infected and show misc. CNS signs leading to death; these animals cannot transmit the parasite in their feces **UPDATE 2010 - Confirmed that domestic dogs can acquire the parasite from raccoons and it can complete it's life cycle in the dog so that the dog is now shedding both types of worm eggs in it's feces.)

  5. Keep children from handling raccoons or from exposure to raccoon feces; e.g., cover backyard sandboxes.


 

PROTOZOAL DISEASES

These are one-celled animal parasites that infect both wildlife and humans.

 

GIARDIASIS

Infectious Agent:......Giardia lamblia

Host:.........................Beaver, muskrat, waterfowl.

Transmission:...........Fecal contamination of water and hand-to-mouth transfer of cysts from feces of an infected animal. Both wild mammals and birds can harbor these organisms. They presumably have acquired the disease from infected waters. Waterfowl and aquatic species of mammals are most frequently infected.

Symptoms:...............A protozoal infection of the small bowel is often asymptomatic but may be associated with a variety of intestinal symptoms: chronic diarrhea, abdominal cramps, bloating, weight loss, and frequent loose, pale stools.

Prevention:.................

  1. Avoid and hand-to-mouth contact while handling any wildlife species.

  2. Good personal hygiene and hand washing.

 

TOXOPLASMOSIS

Infectious Agent:......Toxoplasma gondii

Host:.........................Most commonly the house cat; wild animals

Transmission:...........Ingestion of the oocyst (egg); eating undercooked infected meat; transplacental infection in primary infections of pregnant women. Although wild animals are often cited as infectious agents for toxoplasmosis, the domestic house cat is the only species that passes infective eggs in its feces. All other warm-blooded species may become infected but are not excreters of the infective eggs. Other nondefinitive hosts only become infective when they are eaten by another animal.

Symptoms:...............The disease is seldom severe and usually is self-limiting. Acute disease may result in high fever, lymph node enlargement, muscle pain, and even death. A pregnant woman is particularly susceptible and, when infected for the first time, often passes the parasite on to her baby. Up to 3,000 babies are born every year in the United States with ocular lesions produced from Toxoplasma gondii.

Prevention:.................Confining cats will prevent their contact with wild species. Make certain to practice good personal hygiene and sanitation. To avoid children interacting with infected cat feces, keep backyard sandboxes covered.

 


 

TICK-BORNE DISEASES

Several species of ticks are responsible for transmitting diseases from wildlife species to humans. As these ticks develop from juveniles to adults, they parasitize several different hosts. In ticks, the infective organism is transmitted both from the female to her offspring and between stages of the tick's life cycle.

 

LYME DISEASE

Infectious Agent:......Borrelia burgdorferi (a spirochete)

Host:.........................Deer ticks, often found on deer, mice, squirrels, weasels, bats.

Transmission:...........Tick bites (Ixodes)

Symptoms:...............Little is known about the signs in wild animals and it is felt that probably there are not many pathogenic effects on these animals. In humans, early signs include an expanding ring-shaped skin lesion. Signs include malaise and fatigue, relapsing fever, myalgia, arthralgia (muscle and joint pain), headache, stiff neck, and lymph node enlargement. Days or months later, a chronic or recurring arthritis may develop which may lead to neurological or cardiac problems. Other signs include chills, profuse sweating, vertigo, and varying jaundice.

Prevention:.................Tick control of animals in our care.

 

ROCKY MOUNTAIN SPOTTED FEVER

Infectious Agent:......Rickettsia rickettsi

Transmission:...........Tick bite

Symptoms:...............Rocky Mountain Spotted Fever is characterized by sudden onset with moderate to high fever that persists for two to three weeks. Headache, chills, and rashes that progress to hemorrhages are common. The fatality rate is about 20 percent in the absence of specific therapy. With prompt treatment, death is uncommon. The disease is generally restricted to the summer months in areas where the dog tick (Dermacentor variabilis) and wild animal hosts are abundant.

Prevention:.................

  1. Avoid tick-infested areas.

  2. Same as for Lyme Disease.

 


 

PHYSICAL TRAUMA

The last group of health-related problems involves physical trauma from a wild animal. Whenever a wild animal must be handled, the procedure must be accomplished as safely and quickly as possible.

Prevention:...............Proper techniques must be employed to minimize the risk of personal injury while, at the same time, avoiding injury to the animal. Gloves, catch sticks, caging, and other appropriate equipment may be necessary when handling a wild animal. Most of these animals will be extremely stressed, resisting every restraint attempt.

Treatment:................In the unfortunate circumstance that a person is bitten or scratched, he or she should cleanse the wound thoroughly with soap and flush with water immediately, providing for a mechanical removal of potentially infective organisms. This should be followed by cleansing under medical supervision. The question of rabies should be addressed, depending upon the species of animal and vaccination history. After a bite wound, one of five courses should be decided upon:

  1. Begin post-exposure rabies prophylaxis immediately.

  2. Sacrifice the animal and examine the brain for rabies.

  3. Place the animal under observation (NOT an option with wild animals!)

  4. Determine when there is no risk of rabies and no action is necessary.

  5. Receive a tetanus vaccination or anti-toxin. The advice of a physician should be sought to help make the best possible decisions regarding the management of the injury.


 

-- adapted from the following:

Pocket Guide to the Humane Control of Wildlife in Cities & Towns, The Humane Society of the United States, 1991.

Basic Wildlife Rehabilitation 1AB, International Wildlife Rehabilitation Council, 1992.

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This page last updated 11/27/2012 02:07 AM