Nasty Infectious Diseases You Want To Avoid - Schistosomiasis
This is an infection that occurs worldwide, caused by flukes (parasites) that live and multiply in freshwater snails. It is also known as snail fever. There are two types of human schistosomiasis (swimmer's itch) and visceral schistosomiasis, a serious systemic disorder that occasionally causes minor skin symptoms. The disease is caused by one of three types of flukes (called schistosomes) acquired from bathing in infested lakes and rivers.
Visceral schistosomiasis is a parasitic disease (which is also called bilharziasis) that causes an itchy rash where flukes have penetrated the skin. The disease is found in most tropical countries and affects more than 200 million people around the world.
Theodor Bilharz first described the cause of urinary schistosomiasis in 1851. The first doctor who described the entire disease cycle was Piraja da Silva in 1908. The species of Schistosoma which can infect humans include: Schistosoma mekongi and Schistosoma japonicum which cause Asian intestinal schistosomiasis; Schistosoma mansoni and Schistosoma intercalatum which cause intestinal schistosomiasis; and Schistosoma haematobium which causes urinary schistosomiasis.
Cause - When the parasite-infected snails release large numbers of very small larvae in the water, the larvae can penetrate unbroken skin of a human host, where they develop within their host into adults; their eggs provoke inflammatory reactions. The worms enter the blood and make their way into the liver and intestines. Travelers are at risk when swimming in an area where the infection is present.
Symptoms - Symptoms begin within two to three weeks of exposure. While it also causes problems in other organs, the skin symptoms of this condition include dermatitis, hives, and skin lesions due to the deposits of eggs in the skin. The relatively minor skin symptoms of this form of schistosomiasis are quite different than the marked skin inflammation in swimmer's itch (the second form of schistosomiasis). About one to two months after the penetration of the skin, hives again appear. Skin lesions caused by the egg deposits may appear in the genital and perineal areas.
Treatment - There is no vaccine to prevent the disease, and visitors to the tropics should assume that all lakes and rivers are unsafe for swimming. Praziquantel has revolutionized the treatment of this form of schistosomiasis since the 1980s, since one dose can kill the flukes and prevent further damage. Alternative drugs are oxamniquine and metriphonate. Antimony has been used in the past to treat Schistosomiasis as in minute doses this toxic metalloid has the effect of bonding to sulfur atoms in the various enzymes utilized by the parasite and eliminates it without harming the host. A pharmaceutical agent manufactured by an Egyptian drug company, Mirazid, was under investigation but it turned out that Praziquantel was proven to be several times more effective than Mirazid.
Prevention - Since there is no way to tell infested from noninfested water, travelers should avoid freshwater swimming in rural areas of suspected countries. Accidental exposure to water in suspected areas should be followed by immediate, vigorous towel drying or quick application of alcohol to the exposed areas of skin.