Wildlife Toxicology

Wildlife Toxicology

BI 469/669

Fall 2013

Important Wildlife Diseases

General Comments: Use extreme caution if you encounter sick or dead wildlife. The morbidity or mortality may be due to a disease or toxic agent. Notify authorities immediately. Use Personal Protective Equipment (PPE) such as masks, gloves goggles, respirator, coveralls, etc. Thoroughly clean and disinfect, or discard any contaminated clothing or equipment. If you experience symptoms and seek medical care, inform the physician that you encountered a wildlife health situation.

Zoonosis (noun) Zoonoses (plural) Zoonotic (adjective) -- a disease communicable from animals to humans

ZOONOTIC DISEASES

RABIES

Affected Species: HUMANS, skunks, raccoons, foxes, coyotes, bats, domestic cats, dogs, and cattle.

Disease Agent: virus, a rhrabdovirus

Signs and/or Symptoms: In wildlife the signs depend upon the stage of the disease. Four stages are recognized: Asymptomatic and Prodromal stages show little or no signs. Furious stage is characterized by unusual/overtly weird behavior (virus affects the central nervous system), frothing, and tendency to bite everything. Dumb stage is characterized by paralysis, photophobia, and death.

Notes and Comments: If rabies is suspected use extreme caution. Kill the suspect animal, but do not shoot it in the head. The brain is the critical tissue required for a definitive diagnosis. Use prophylactic hand covering (rubber gloves or a plastic bag) and remove the head. Double-bag the head and keep it chilled or cooled. Do not freeze – this will ruin the diagnostic test. Ship the head to the state health department. Prominently label the shipment to indicate that rabies is suspected.

Recommendations: Wildlife incidence cannot be controlled currently. Domestic species should be vaccinated. Very few humans die from rabies, however, the treatment is not fun. In humans, if the disease reaches the furious stage, then mortality is 100%. Be very careful with skunks, raccoons, etc. that show no fear of humans and act weird. If bitten by any species, immediately flush and wash the wound with warm, soapy water.

PLAGUE

Affected Species: HUMANS, wild rodents (rodent fleas are the vector)

Disease Agent: Yersinia pestis, a cocobacillus bacterium

Signs and/or Symptoms: In humans symptoms appear after a six to eight day incubation period. Symptoms include fever, lethargy, person is often prostrate, and swelling (bubos – hence bubonic) of the lymph nodes, particularly in the groin region. These bubos are very painful.

Notes and Comments: In the U.S. the disease is restricted to wildlife in western states. Elimination in wildlife is not currently possible. Approximately 20-30 people die annually from the disease in the U.S. U.S. Fish and Wildlife monitors the incidence and distribution of the disease in wildlife by use of Nobuto strips (paper strips used for collection of blood samples) taken by hunters and trappers in affected areas.

Recommendations: Be aware whenever you enter a plague-infected area. A prophylactic vaccine is available, but this is not recommended unless you will be handling animals with the disease. If symptoms appear and disease is suspected, then seek medical help immediately and inform the physician of your possible infection with plague. Streptomycin is very effective in early stages of the disease.

ANTHRAX

Affected Species: HUMANS, domestic livestock, wild ungulates

Disease Agent: Bacillus anthracis, a gram positive rod bacterium

Signs and/or Symptoms: In animals the postmortem signs will include very dark, tar-like blood that does not coagulate. Blood will be coming out of all body orifices and the carcass will not show rigor mortis. Often there are no pre-mortality signs; the disease is acute or peracute – the animal is alive and seems normal one hour and is dead the next hour. In humans, the initial symptom is a pussy oozing carbuncle on the skin. It can be treated with antibiotics if caught early.

Notes and Comments: Do not attempt a necropsy. The disease spreads by spores and necropsy will release spores. The spores have phenomenal persistence. An anthrax contaminated area may remain contagious for more than 50 years. Anthrax has been essentially eliminated in the U.S. However, it persists in foreign countries and occasional outbreaks in the U.S. are associated with imported animal products (bone meal, wool and wool products, and animal hides).

Recommendations: Call the U.S. Department of Agriculture if you even suspect anthrax. Their experts will be on the scene rapidly while you go get antibiotic shots. Anthrax is quite rare in the U.S. but it is a very contagious and very serious disease that you should be aware of.

BOTULISM

Affected Species: HUMANS, many wildlife species, especially ducks

Disease Agent: Clostridium botulinum, a gram positive bacillus

Signs and/or Symptoms: In ducks, the signs include a dazed appearance, uncoordinated, “lazy neck” (e.g., bird does not hold its head up and neck seems rubbery), loss of body control – especially legs and wings. Many birds will drown and there may be high mortality of animals within a geographically restricted area. The disease may spread rapidly.

Notes and Comments: Waterfowl botulism occurs regularly and kills many birds. Early recognition and action are keys to minimize the number of mortalities. If unchecked, it can kill thousands of birds in one area. The bacterium is ubiquitous; however, the toxin is produced only under anaerobic conditions. The disease occurs most often in fall season in western areas. Favorable ecological conditions include shallow water, warm weather, and decaying aquatic vegetation. Under these conditions the bacteria may colonize vegetation and invertebrates and, if low oxygen levels are present, may produce toxin. Birds ingesting the toxin along with foods will show signs of disease. Bacteria will also be ingested along with the toxin. Dead birds will be colonized by maggots. The maggots will ingest the toxin without harm to them and may actually concentrate the toxin. Maggots are a tempting food morsel to other, healthy ducks which will ingest the maggots and die…and the disease continues to spread.

Recommendations: Prompt action is imperative to slow or stop the spread of the disease. The first step is to collect all carcasses so that maggot infestations do not develop or existing maggot infestations are destroyed. Second, healthy birds should be discouraged from the site by fright techniques. If feasible, the water levels in the habitat should be lowered (drain the marsh) or raised (to increase oxygenation).

TULAREMIA (aka: rabbit fever, deer fly fever)

Affected Species: HUMANS, rodents, rabbits, raccoon, mink, muskrat, deer

Disease Agent: Francisella tularensis, a coccobacillus bacterium

Signs and/or Symptoms: In animals, a large number of dead and dieing rodents in an area may indicate tularemia (also think of plague and rodenticides). Upon necropsy, these animals will have distinct white necrotic spots on the liver. Symptoms in humans include a rapid onset of fever, chills and weakness. Often called the “great masquerader” because of its nonspecific symptoms, this human disease is often misdiagnosed by physicians. Wildlife biologists, therefore, should be aware of this disease so that they can inform their physician that they may have contracted tularemia. The treatment of choice is streptomycin. If left untreated, approximately five percent of people will die and the remainder will be incapacitated for some time, often several months. The incubation period after exposure is three to five days.

Notes and Comments: The highest incidence in humans is during the fall season, corresponding to the trapping/hunting season for affected wildlife species. The human cohort at greatest risk is trappers. The most common form of transmission is thought to be handling, skinning, and gutting infected animals with cuts or breaks in the hand skin of the trapper or hunter. Other methods of transmission include: oral (eating improperly cooked meat, accidental ingestion of blood, sputum, or contaminated water), arthropods (bites from deer flies or ticks), ocular (touching the conjunctiva with a contaminated source), and bites from an infected animal.

Recommendations:There is no effective procedure for treating wildlife. For the wildlife biologist and sportsman/woman the best recommendation is awareness and caution. If suspect symptoms appear after a probable exposure, then prompt medical treatment is recommended.

TOXOPLASMOSIS

Affected Species: HUMANS, cat species, rodents, ducks, cattle, pigs

Disease Agent: Toxoplasma goondii, a protozoan parasite

Signs and/or Symptoms: In the definitive hosts (cat species) there is little or no pathology. Problems occur when the parasite infects other species. If the tissue invaded is the CNS, then the signs will include behavioral aberrations. Most often the signs are congenital deformities and abortions in wild species. These are also seen as symptoms in humans, as well as, mental retardation of the offspring.

Notes and Comments: Transmission among wildlife is usually through exposure to fecal material and ingestion of raw flesh. Transmission to humans is usually through exposure to fecal material of infected domestic cats. Livestock may also be exposed by domestic cats (e.g., the cat defecates in a food container and the food is later fed to cattle). A high incidence of abortions or malformations in wild or domestic populations may indicate toxoplasmosis.

Recommendations:Ranchers may wish to reduce contact of their livestock with domestic cats, especially if reproductive problems are evident. Pregnant women should be careful about contact with fecal material of pet cats (e.g., don’t let pregnant women empty and clean the litter box). If you are very concerned, you can have yourself and your cat tested for the presence of toxoplasmosis (consult your veterinarian and obstetrician).

GIARDIA or GIARDIASIS

Affected Species: HUMANS, muskrats, beavers, domestic dogs and cats

Disease Agent: Giardia spp., flagellated protozoan parasites

Signs and/or Symptoms: Signs and symptoms include massive diarrhea and severe intestinal pain. The disease is usually not fatal to humans or animals, but does cause severe discomfort and debilitation

Notes and Comments: Incidence of the disease is probably under reported due to failure to recognize the cause of the GI distress. There are local “hot spots” for the disease such as the Olympic Mountains. Transmission is by contact with feces or ingestion of fecal-contaminated water. Several major outbreaks of the disease in humans have been due to muskrats or beavers invading municipal water reservoirs. In water the cysts are not killed by chlorination or iodizination, but boiling does kill the infective cysts.

Recommendations: Be aware when you enter a giardia area and always boil your cooking and drinking water while in the area. Keep muskrat and beaver out of waters that serve as reservoirs for human water consumption, especially in infestation areas. The drugs of choice for humans and animals are Emtryl or Flagyl. If you have been in an infected area and develop symptoms, then inform your physician that you may have contracted giardia.

HANTAVIRUS

Affected Species: HUMANS, various rodent species of the western U.S.

Disease Agent: several different viruses

Signs and/or Symptoms: This is a human pulmonary disorder resulting primarily from inhaling virus particles. Onset of symptoms begins one to five weeks after exposure. The disease begins with fever, fatigue, chills, dizziness, and vomiting and progresses to severe respiratory problems.

Notes and Comments: Disease is most commonly seen in spring and summer seasons. The virus is present in urine, saliva, and feces of rodents. Transmission is through inhalation, rodent bites, or ingestion of contaminated food or water.

Recommendations: Wear respirator and gloves if working with rodents in infected areas. Dusty areas should be wet down to reduce risks of inhalation. Treatment is with broad spectrum antibiotics.

LYME DISEASE

Affected Species: HUMANS, mice, squirrels and other small animals

Disease Agent: Borrelia burgdorferi, a bacterium

Signs and/or Symptoms: The disease causes flu-like symptoms in humans. About half of the cases are accompanied by a “bull’s eye” rash three days to one month after a tick bite. The rash may not be at the site of the tick bite. The disease may progress to include neurological and cardiac problems. Antibiotics are most effective early in the disease.

Notes and Comments: Transmission is by tick bites. Tick attachment for 24-36 hours is needed for transmission. Most cases occur in spring and summer when tick are active and human outdoor activity is high. Disease occurs primarily in the Northeast and Midwest.

Recommendations: Minimize tick bites through use of repellants and wearing long pants and long sleeve shirts. Examine yourself for ticks after outdoor activity and carefully remove ticks without squeezing.

BAYLISASCARIASIS

Affected Species: HUMANS, raccoons, domestic dogs, skunks, foxes, rodents, porcupines, and numerous others.

Disease Agent: Baylisascaris procyonis, an intestinal roundworm nematode of raccoons

Signs and/or Symptoms: Raccoons are the definitive host and rarely develop signs of illness. In other species, signs depend upon organs affected by larval migration. Migration into the CNS results in neurologic symptoms including incoordination, circling, paralysis, and blindness. Symptoms seen in humans may also be neurologic.

Notes and Comments: This is considered an emerging zoonotic disease and more cases of human infection are being reported. The disease is probably under recognized. The majority of human cases reported so far have been in young children. Raccoons shed eggs in their feces. Raccoons may be peridomestic animals living in close proximity to humans. Young children may accidentally ingest eggs from soil, water or objects contaminated with raccoon feces during their exploration and play behavior.

Recommendations: Avoid or minimize contact with raccoons, particularly with their feces. Prompt removal of any raccoon feces will reduce the risk of infection. Wear gloves and wash hands well if handling wild raccoons. If infected, the early recognition and treatment with anti-parasitic drugs will reduce risk of permanent neurologic effects.

DISEASES OF WILD MAMMALS

EPIZOOTIC HEMORRHAGIC DISEASE (EHD)

Affected Species: This is primarily a disease of white-tailed deer (mortality in infected populations may exceed 90%). Antelope are also seriously affected (mortality may exceed 90%), while mule deer show low susceptibility (about 5% mortality), and elk are resistant (0% mortality) though they do show antibody response.

Disease Agent: an arbovirus (spread by arthropods), primary vector is a blood-sucking midge, Culicoides varripennis.

Signs: Disease outbreaks will be evident by a large number of dead and dieing animals in a local area. The disease affects integrity of the vasculature system, such that the blood vessels become leaky. The primary lesion seen at necropsy is massive hemorrhage throughout the body. The disease is often called “black tongue”, because of the color of the tongue. A closely related disease of domestic sheep is known as “blue tongue”.

Notes and Comments: The disease first appeared in New Jersey about fifty years ago. Since then there have been several outbreaks that killed thousands of animals in various regions of the country. The most serious outbreaks have occurred in the southeastern U.S. Outbreaks usually have occurred in late summer, coincident with a population increase of the vector. Many of the dead animals will be found near water. Animals that are hemorrhaging will be thirsty due to loss of fluids. Also, the Culicoides vector breeds in water, so vector populations will be greatest near water.

Recommendations: There is no effective treatment procedure for wild populations. Some efforts have been made to reduce the midge population during outbreaks through insecticide use, but the results were not very successful. The disease outbreaks are self-terminating. If you do nothing, the outbreak will end by itself. This has been the usual procedure. When practical or feasible, the dead deer should be picked up and buried or incinerated.

SARCOPTIC MANGE

Affected Species: primarily wild canids

Disease Agent: Sarcoptes scabei, a mite, an external parasite

Signs: Severely affected animals are UGLY in appearance. The mite burrows into the dermis and causes severe itching, hemorrhage, and irritation of the dermis. The hair follicles are damaged, so there will be hair loss in affected areas of the skin. There will be pussy deposits under the skin, and the bald skin areas will have an oily, reddish-blue appearance due to dermal hemorrhages. Trappers call these animals “rat-tailed” (tail hair is gone) or “blue animals” (due to skin color).

Notes and Comments: From the animal’s perspective, this must be a very unpleasant condition. In winter, furless canids can freeze to death. Due to physiological imbalances caused by the parasite load the disease may also be fatal at cool (non-freezing) temperatures.