Home assignment. At the clinic for your tropical check. The questions turn to barefoot walking and swimming. Podiatry? Cardio? What does this have to do with tropical medicine?
Polonius is right. Though these questions seem madness, “yet there is method in it”: we’re probing for parasites.
“Has your skin ever touched the soil?”
Assessing exposure to strongyloides is the method of this question. A yes-answer leads to a blood test.
The strongyloides infection traces back to tiny larvae from infested soil in the tropics and subtropics. After penetrating the skin, the intestinal nematodes (microscopic roundworms) begin stealing the nutrients in your gut. Unlike many parasites, the strongyloides parasite can complete its full life cycle in your body, making it near impossible for the body to cure itself.
Most infections do not have prominent symptoms. With acute infections, a localized itchy, slightly redden and raised rash can develop at the site of skin penetration. This can be followed by pulmonary symptoms (lungs), diarrhea, and abdominal pain. Strongyloides can be dangerous. If infected persons become immune suppressed or receive treatment with agents that suppress the immune system, the larvae can disseminate dangerous bacteria throughout the body.
Ivermectin is the treatment of choice. No vaccine is available, nor are there preventative drugs. You can reduce risk of infection by wearing shoes, using a mat while at the beach, and wearing gloves when gardening.
“Have you had any fresh water exposure, such as swimming?”
Now we’re looking for Schistosomiasis. As with strongyloides, exposure necessitates a blood test.
The Schistosomiasis “fluke” parasite can penetrate the skin when you swim in a contaminated freshwater body. An estimated 85% of cases are in Africa, though others are found in Indonesia and Southeast Asia.
If you live in a country with schistosomiasis, consider all bodies of fresh water infected, and avoid all contact. In case of accidental exposure, vigorous rubbing and towel-drying of exposed areas may prevent parasite penetration.
Swimming in properly chlorinated pools is almost always safe, even in endemic countries. Salt water is always safe.
Pipe water from untreated sources may contain cercariae (the parasite at its larval stage). To eliminate risk of infection, use a fine-mesh filter, heat bathwater to 50 degrees Celsius for 5 minutes, or allow water to stand for at least 24 hours.
Treatment of choice is Praziquantel.
Have you taken a worm treatment prior to departure from you international assignment? It is safe, cheap, harmless and effective.
At your consult, we give you a small red-topped container to collect a stool sample. (The liquid inside is a preservative, and the sample does not need to be refrigerated.) The lab examines the contents for parasites, eggs or cysts.
The presence of parasites in the stool sample is not always dangerous. In fact, some organisms live in a symbiotic relationship with the humans, and unless there are symptoms, treatment may not be necessary.
Do you use a water purification system?
Access to potable water is indispensible. Many parasites spread via the oral-fecal route. Risk of infection is highest where sewage systems are wanting. The best prevention is careful hand washing, rigorous food preparation, and food and water hygiene.