Wildlife and Human Health


Giardia lambliais a common, single-celled parasite, which can cause an illness of the intestines known as Giardiasis. The disease can be found throughout the world and is widespread among mammalian, avian, and reptile species; including humans, companion animals, wildlife, sheep and cattle, and wading birds. Giardia goes through two stages.  During the first stage, called the trophozoite stage or “active” stage, it is in the intestine of the host and cannot survive on its own.  During the second stage, called the cyst stage, it becomes protected and infectious and is shed in the feces of the host.  In this second stage, Giardia can be killed between 129º and 132º F and dies instantaneously at boiling point, 212º F, but it can last 2 – 3 months in cold water.

When humans become sick with Giardia, the Giardia parasite is predominantly spread via person-to-person contact. Due to poor hygiene practices, rapid transmission can occur in developing nations, day-care facilities, and institutional settings. Contamination of food and water sources from human or animal-infected fecal material is another means of transmission. Symptoms of the disease usually appear from nine to twelve days after exposure; however, they can appear within five to twenty-five days. Some people don’t show any signs of illness at all, though they may still shed the parasite. The disease is characterized by numerous intestinal symptoms that can last from one week to a few months, and may include diarrhea, flatulence, abdominal cramping and discomfort, fatigue, and weight loss. Treatment is available through prescribed antibiotics. Some individuals recover without the need for medication.

Giardia and Beaver

Research has shown that Giardia of human origin can be transmitted to several wildlife species. More research is needed, however, to determine the role wildlife plays in transmitting Giardia to humans. Being a highly visible species in watersheds, the beaver has often been unfairly implicated as the source of Giardia contamination of fresh water resources. The term “beaver fever” is often used to describe waterborne outbreaks. However, current research shows that contamination from humans is regarded as a more probable source. In fact, humans are now considered to be the most common reservoir, as they shed 900 million cysts per day. There has never been a proven, documented case of a human contracting Giardia from beaver. Many studies claiming to have done so lack any scientific evidence in support of the claims. Giardia from human sources can enter waterways by many different methods, such as washed-out septic systems, untreated human sewage discharged into waterways, cabin toilets, and backpackers and campers who inadvertently deposit contaminated feces in the environment that is washed away by rain and ends up in rivers and streams. Near highly used human recreational areas, studies are showing that there are increased Giardia cysts in surface water and wildlife.


You can protect yourself and your family from Giardiasis using preventative measures, such as good personal hygiene including frequent hand washing and wearing gloves when handling possible contaminated materials. Careful disposal of sewage wastes and protecting water supplies from human, companion animal, and wildlife contamination is also important. Avoid drinking water that has not been treated or filtered, and carry treated water (boiling water is most effective) or equipment for purifying water with you when you are hiking or camping.

Lyme Disease

The bacterium that causes Lyme disease can be spread to both people and animals through the bite of very small infected ticks. The disease can be found throughout the United States, however is most common in the northeastern and coastal states, the upper Midwest, and the Pacific Northwest.


Lyme disease is most often spread during the late spring and summer through the early fall season. Ticks live on low-lying brush and grassy areas, and subsequently crawl onto animals and people who come into contact with these plants. The bacteria causing Lyme disease is transmitted to the ticks when they bite an infected animal and then, in turn, the ticks can transmit the bacteria to humans. Not all ticks carry the bacteria causing Lyme disease. An infected tick must be attached for at least 24 hours before it can transmit the bacteria to humans. Removing ticks as soon as possible can reduce the chance of infection.


Symptoms of the disease usually appear from 3 to 32 days after exposure. In many cases, a bulls-eye or donut-shaped rash appears at the bite site, and is often accompanied by flu-like symptoms such as fever, headache, lethargy, swollen glands, sore throat, and stiff muscles and joints. In addition, skin irritations like hives, redness in the cheeks and eyes, and burning or itching may also occur. Some people don’t show any signs of infection, and symptoms often disappear on their own after a few weeks. The person will remain infected, however, and without treatment, the disease can progress into more serious illness involving the joints, nervous system, and heart. Lyme disease is most often diagnosed through the bulls-eye or donut-shaped lesion, but doctors can also have patients’ blood tested for the bacteria antibodies.


Treatment is available through prescribed antibiotics. Early detection and treatment can prevent more serious problems from occurring.


You can protect you and your family from Lyme disease by using preventative measures, such as knowing and avoiding places where infected ticks are found, and by quickly removing ticks if bitten. If unavoidable, steps to keep exposure to a minimum should be taken, by covering skin with long-sleeved shirts and long, light-colored pants tucked into socks. Using tick repellents and checking your body and clothing every three to four hours is recommended. Ticks often gravitate toward the legs and thighs, armpits, ears, groin, and hairline. They are very small and in the nymph stages are no larger than the head of a pin, so a careful “tick-check” of the body is recommended. When removing ticks, pull them straight out and do not crush them. Thoroughly wash the wound and your hands if you used them to pull the tick out, and apply antiseptic on the bite. Be sure to check companion animals for the presence of ticks and use preventative measures on them, as well. If you notice a bulls-eye or donut-shaped rash or develop symptoms of Lyme disease after being in an area with ticks, see a doctor as soon as possible.

Learn more about Lyme disease and deer hunting and about the ecology of Lyme disease.


Rabies is a much-feared disease of the nervous system that dates back to ancient times. It is caused by a virus that is transmitted by contact with the saliva of an infected animal, usually through a bite or scratch. The incubation period can last from several weeks to a year or more. There is no known cure for the disease in animals. If not treated immediately, the disease is also fatal in humans.

Rabies was rare in Massachusetts for decades, appearing primarily in a very small percentage of bats. However, an outbreak of raccoon rabies, which originated in the Mid-Atlantic States in the late 1970’s, has now made its way to New England. It is one of several strains of rabies currently plaguing wildlife in different areas of the United States. It is essential that residents know how to protect themselves, their pets, and other animals.

You can’t be completely sure that an animal has rabies just by looking at it. Animals with rabiessometimes become aggressive, have seizures, attack people and other animals, and alsosometimes act confused and disoriented, show signs of paralysis, and make hoarse vocal sounds. They may also just stand and stare. If you see an animal that you suspect may be rabid, don’t try to deal with it yourself. Call your local animal control officer, animal inspector, police department, Massachusetts Division of Fisheries and Wildlife, or the Massachusetts Department of Public Health.

All mammals can contract rabies, but the current outbreak primarily affects raccoons, with some spillover into skunks, foxes, and occasionally woodchucks (also known as groundhogs). Birds, rabbits, opossums, squirrels, chipmunks, rats, mice, and other small rodents are rarely affected. Snakes, turtles, lizards, frogs, toads, salamanders, fish, and insects do not get rabies.

Enjoy wild animals from a distance. Never handle or attempt to pet or feed them. Do not keep wildlife as pets. Keep your trash cans in a closed garage or shed. Use raccoon-proof lids on garbage that is outside. Keep cats indoors and supervise domesticated pets when outside at all times. Be sure your dogs and cats are up to date on their rabies vaccinations. If you keep a bird feeder, clean up spilled seed to avoid attracting other forms of wildlife. Consult your veterinarian about vaccinating livestock, since they can also contract rabies.

Read more about rabies on the CDC’s site.

West Nile Virus

West Nile Virus is a virus that causes encephalitis and is primarily transmitted to humans and other animals by mosquitoes and ticks while they feed. There is no vaccine currently available to prevent the virus, and children, the elderly, and immuno-compromised people are at greater risk for developing severe illness. There are preventative measures that can be taken to help reduce the number of mosquitoes in your area. Taking steps like eliminating all sources of standing water on your property (mosquitoes are able to breed in any puddle that lasts longer than four days), wearing long-sleeved shirts and pants when outdoors between dusk and dawn, and checking to make sure window and door screens are securely attached and don’t have any holes can help. For more information about West Nile Virus see the Massachusetts Department of Public Health’s fact sheet.

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