By Dr. Margaret Williamson Infectious Disease Specialist, Georgia Infectious Diseases
Parasites can be subtle, and you don't need to travel to the jungle to become infected with a parasite. Simply going to the park or hiking in the woods can be enough. Few doctors can recognize common symptoms or problems as parasitic infections. Doctors will also need lab tests and exposure histories to find these sneaky parasites. However, not all doctors are trained to look for parasites. Infectious disease specialists are best qualified to diagnose and treat these conditions.
Here are three parasites to watch out for:
Toxocara is a dog or cat roundworm that can accidentally infect humans. Typically these worms live in the gut of your pet. The eggs of the parasite are released in poop that can infect the soil. The tiny larvae within the egg live a long time in the soil, silently waiting for the next animal to pick them up. They are regularly found in city parks, sandboxes and areas of dirt where pets poop on a regular basis. The southeastern US has the most cases.
Humans are exposed to toxocara by playing in the dirt – either in the park or in their own gardens. The eggs can get on our hands or under our nails. If we put those hands in our mouth, eat before washing our hand or get our fingers too close to our faces, we can accidentally put the eggs into our body. Children are particularly at risk since they are not the best at washing their hands.
Toxocara can cause fever, flu-like symptoms, swollen liver, wheezing, cough and shortness of breath. Sometimes it can cause seizures, behavioral changes or poor appetite. These widespread symptoms correspond to where the small larvae travels throughout the body. This condition is called visceral larva migrans. Visceral means organs, larva means worm hatchlings and migrans means traveling in many directions.
However, there are more subtle versions of toxocara that can be much more difficult to diagnose. Covert toxocaraiasis may just cause abdominal pain, poor appetite, isolated wheezing or coughing. The worm can travel into the eye on its random journey in the body. The retina can become very inflamed and the center part of the eye can get cloudy. This is called ocular toxocara.
To diagnose a toxocara infection, your doctor should start with basic blood tests, including blood counts. When the larva travels through the body, your eosinophils increase to very high levels in your blood. This is a major clue that disseminated parasites are causing the problem. Eosinophils are a type of white blood cell that attack parasites. Specific antibody tests for toxocara can then pinpoint this worm as the cause of the infection.
To treat the infection, there are several pill antibiotics that kill toxocara. Both mebendazole and albendazole are commonly used. Treatment usually lasts 1 to 3 weeks. If there is eye involvement, doctors use steroids to calm the inflammation. The patient may need surgery to clean the center part of the eye. Sometimes people need multiple rounds of both antibiotics and steroids to treat relapses.
To prevent a toxocara infection, make sure to wash your hands after working in the yard or playing in the dirt. Treat your pets on a regular schedule for roundworms. Pregnant dogs should also be treated so their litters do not get infected. And be sure to scoop your pet’s poop!
Babesia is a microscopic parasite that infects our red blood cells. It is very similar to malaria. These parasites grow and multiply inside the red blood cell, increasing in number until the cell explodes. The same ticks that carry Lyme disease can also carry Babesia. The majority of cases are found in the northeast. New York State and New York City lead the list in numbers of cases.
How do humans get exposed? Ticks attach to mammals in order to suck small amounts of blood. Typically very young ticks called nymphs carry the strongest potential for infection. They need to stay attached for more than 24 hours in order to transfer their infection from their saliva into our blood stream. The longer they stay attached, the bigger the chance you will get sick.
After being infected with Babesia, people may feel achy, with muscle pains, fatigue headache and fever. It can be mistaken for flu symptoms. With more significant infections, people become anemic and even jaundiced as the red blood cells are destroyed. There are people who are especially at risk for severe infections. People over the age of 60 tend to be sicker than others. If you have had your spleen removed for any reason, you need to be aware of this infection and remind your doctor that you don’t have a spleen.
Babesia diagnosis starts with a simple blood smear. The cells are examined under a microscope, and the doctor then looks for tiny rings of parasite inside the cells. Clumps of four Babesias form a chunky cross. This “tetrad” is diagnostic. Sometimes finding these tiny organisms is like finding a needle in a haystack. Only 1% or less of your cells have visible parasites. For these subtle cases science can amplify tiny specks of parasite DNA to find the culprit.
Lastly, antibodies against Babsesia can suggest infection. These last two types of tests need to be sent to special labs for analysis.
Is there treatment? There are many people who have very light cases without getting sick, and their body fights off the infection on its own. Anyone who becomes sick – even with just flu-like symptoms – should be treated. Two different antibiotics are needed to kill the parasite: atovoquone and azithromycin. Both pills are taken for a week. For the critically ill, stronger antibiotics like quinine and clindamycin are favored.
In order to avoid babesia, avoid ticks! Know if your area has a high risk of Lyme disease. If it is, then Babesia is likely in your neighborhood as well. Ticks tend to live in tall grasses, near woodpiles and at the edge of forests. Wear light-colored clothes because the tick shows up well against the light background. Tuck your socks over your pant legs, which might make you feel silly, but it prevents ticks from latching to your ankles as you walk through the meadow. Mosquito repellant with DEET is also effective against ticks. Shower after your adventure and look for ticks on yourself, your children and your pets. Look behind the ears and on the neck, scalp, legs and groin areas, which are their favorite places to cling.
Cercarial Dermatitis (aka “Swimmer’s Itch” or “Clam Diggers’ Disease”)
Cercarial come from bird schistosomes, which are parasites that live in the blood of water birds. The parasite is eventually released in their poop and infects the water. Small snails pick up the parasite, where it matures into a cercarial form. These are dumped back into the water, where they look for another bird to continue the cycle.
Humans can be the accidental host when the tiny larvae stick into our skin. Luckily, humans are different enough from birds that these parasites cannot live long. The parasites die quickly as our body’s defenses attack. This inflammation that our body generates causes the rash, not the parasite itself. The parasite is commonly found in fresh water lakes. Outbreaks are common in the upper Midwest, but the parasites have also been found in Delaware, New Mexico and Colorado.
Spending time in the shallow water can expose our legs and bodies to these small parasites, especially during the warm summer months. After infection, the skin will burn, and then intense itching takes over. Small bumps that look like pimples or blisters appear after 12 hours. If you scratch open the skin, bacteria can infect the wounds. Every time you get exposed, the rash and itching gets worse. Our body recognizes the parasite and will increase the amount of inflammation with each exposure.
There are no tests to diagnose cercarial dermatitis. Having a history of a recent lake exposure is typically enough to imply the diagnosis. Usually the rash goes away on its own within two weeks. Topical cortisone can help calm the inflammation, and Benadryl helps with the itching. If the rash lasts longer than two weeks, you either got it infected or you have been reexposed to the parasite.
In order to prevent yourself from getting sick, limit your time in shallow water. Wash off the water as soon as you get out and towel dry. If you develop a rash within a day of swimming, avoid contact with the lake because repeated exposure will just make the rash worse.