Diseases From Animals: A Primer
A is for animals, Z is for zoonoses.
Wild animals should stay that way. Enjoy them from a distance. Even so, they're a rich source of human disease. Here are a few:
Raccoon roundworm. This is the best reason not to feed wild raccoons. The feces of an infected raccoon carry millions of roundworm eggs. These eggs become infectious in two to four weeks and can survive for years in the environment. They are very difficult to kill -- the CDC recommends cleaning contaminated decks or porches with boiling water or a propane flame gun (with proper caution, of course).
Symptoms depend on where the roundworms travel in the body. They can include nausea, fatigue, enlarged liver, and symptoms of brain infection (poor coordination, inattention to one's surroundings, loss of muscle control, coma, and/or blindness). Some infections have been fatal. Diagnosis is difficult. If you are having symptoms after contact with raccoons, be sure to tell your doctor. There is no specific cure, but early treatment can limit the extent of disease.
Giardia infection. This microscopic parasite is the hiker's bane. It's one of the main reasons why you should always purify water taken from a stream, no matter how far from civilization you're camping. An infected animal sheds Giardia in its feces. It can survive for a long time in water and in soil.
Symptoms include loose or watery diarrhea, stomach cramps, and stomach upset. People with Giardia infection are contagious and easily spread the parasite to others. Fortunately, there are excellent curative treatments.
Hantavirus. This deadly virus is carried by some strains of mice, especially deer mice. People get the infection by breathing dust contaminated with mouse droppings. If you need to clean an area that's been infested with mice, DON'T sweep it up in a big cloud of dust. Instead, put on latex gloves, wet the area with detergent or diluted bleach, wipe with damp towels, and then mop. Burn all contaminated materials. And be sure the mice are gone -- call an exterminator.
Lymphocytic choriomeningitis (LCM). This is a virus spread by the common house mouse. The virus can infect the linings of the brain and spinal cord. It's a serious disease, although many people get only mild infections. Mice shed the virus in their urine, saliva, and feces. People get infected by eating contaminated food or by inhaling aerosolized mouse urine or feces. LCM has two phases. The first lasts about a week and begins with fever, loss of appetite, head and muscle aches, nausea, and/or vomiting. There may be other symptoms as well.
The second phase happens just as the first one gets better. It may begin with symptoms of meningitis: fever, headache, and stiff neck. It may also begin with symptoms of encephalitis: sleepiness, confusion, and movement problems. There's no cure, but most people recover completely with supportive treatment. However, some people are left with permanent nerve or brain damage. About 1% of people with LCM die.
Tularemia (rabbit fever). People usually get tularemia from direct contact with rabbits. A person can also get it via the bite of an infected tick or deerfly, by eating contaminated food, by drinking contaminated water, or by breathing in F. tularensis, the bacteria that causes rabbit fever. It's very infectious: Fewer than 10 microscopic germs can cause a lethal infection. This is why tularemia was studied during World War II as a germ warfare agent.
The kind of disease one gets depends on how one is infected. The inhaled form is most severe, with a 30%-60% fatality rate in untreated cases. It causes pneumonia with sudden fever, chills, muscle and joint aches, dry cough, and progressive weakness. In severe cases there is bloody spit with difficulty breathing.
Equine Encephalitis and West Nile Viruses
The equine encephalitis and West Nile viruses are transmitted from wild birds to humans -- and to horses -- by mosquitoes. We read a lot about West Nile virus, because of its recent arrival in the U.S. and its rapid spread across the nation. It can cause a very dangerous infection of the brain and spinal cord. So can equine encephalitis, which has long been firmly rooted in the U.S. In fact, eastern equine encephalitis is considered a much more serious disease. About 30% of people who get it die, and another 30% have lasting nerve damage.
Most years there are very few cases of equine encephalitis. But some years are much worse than others -- and there's no way to predict in advance when there will be an outbreak. It's too soon to know whether West Nile virus will be the same every year or come in cycles in the U.S.