Leptospirosis and Schistosomiasis are two diseases that can be contracted in the tropics and subtropics by skin contact with fresh water are schistosomiasis and leptospirosis.
Schistosomiasis (also known as bilharzia) is a parasitic infection caused by larvae released from snails that live in fresh water. Humans become infected when the larvae penetrate unbroken skin, thus entering the body.
Travelers at risk are those who wade, swim, or bathe in freshwater (lakes, rivers, streams, etc) where the snail hosts are present.
Schistosomiasis occurs throughout the tropics and subtropics and is most prevalent in sub-Saharan Africa, but is also found in Southeast Asia, S. America, the Carribean, and the Middle East.
There is no practical way to distinguish infested waters from non-infested waters. Swimming in adequately chlorinated swimming pools is usually safe. Vigorous towel drying after a brief accidental exposure to waters may be a way to prevent infection. If you have had exposure to fresh water while in a country where schistosomiasis is present you should have a blood test done 6-8 weeks after exposure to the water.
Leptospirosis is a form of bacteria that is carried in the urine of infected wild and domestic animals. The majority of occurrences of this disease have occurred in tropical climates, but is prevalent worldwide. Recent outbreaks have occurred in the Dominican Republic (2007), Fiji (2007), Phillipines (2008), Costa Rica, Malaysian Borneo, and more.
Leptospirosis can also be transmitted through soil or water that has been in contact with an infected animal. The occurrence of heavy rainfall increases the risk of spread of the organism.
Leptospira can enter the body through cut or abraded skin, mucous membranes, and conjunctivae. Ingestion of contaminated water may lead to infection. For example, if you choose to go white water rafting in an area where leptospirosis happens to be an epidemic or water is splashed on broken skin when hiking than you could be putting yourself at risk.
The incubation period for leptospirosis ranges from 4 to 29 days. Leptospirosis can be a mild to severe illness. Symptoms usually begin abruptly with:
No vaccine is available to prevent leptospirosis. If you think you might be at risk for leptospirosis you should wear protective clothing, covering cuts and abrasions with dressings, and minimize contact with potentially contaminated water. Currently the CDC recommends that travelers who might be at increased risk for leptospirosis consider taking doxycycline preventively (200 mg orally, weekly), begun 1-2 days before, and continuing through, the period of exposure.
Schistosomiasis (Medline Plus)
Leptospirosis (Medline Plus)
Travelers' Health (CDC)