http://www.cdc.gov/travel/diseases/schisto.htm
http://www.cdc.gov/ncidod/diseases/submenus/sub_schistosomiasis.htm
|
Schistosomiasis Description Schistosomiasis is caused by flukes, whose complex life cycles involve specific fresh-water snail species as intermediate hosts. Infected snails release large numbers of minute, free-swimming larvae (cercariae) that are capable of penetrating the unbroken skin of the human host. Even brief exposure to contaminated water can result in infection, for example, by wading or swimming in or bathing with contaminated fresh water. Human schistosomiasis cannot be acquired by wading or swimming in salt water (oceans or seas). Clinical manifestations of acute infection can occur within 2 to 3 weeks of exposure to cercariae-infested water, but most acute infections are asymptomatic. The most common acute symptoms are fever, lack of appetite, weight loss, abdominal pain, weakness, headaches, joint and muscle pain, diarrhea, nausea, and cough. Rarely, the central nervous system can be involved, producing seizures or transverse myelitis as a result of mass lesions of the brain or spinal cord. Chronic infections can cause disease in the lungs, liver, intestines, or bladder, or a combination of these. Many people who develop chronic infections can recall no symptoms of acute infection. Diagnosis of infection is usually confirmed by serologic studies or by finding schistosome eggs on microscopic examination of stool or urine. Schistosome eggs can be found as soon as 6 to 8 weeks after exposure, but are not invariably present. Occurrence This infection is estimated to occur worldwide among some 200 million people. Schistosomiasis is most prevalent in Brazil; Egypt and most of sub-Saharan Africa; and southern China, the Philippines, and Southeast Asia. Risk for Travelers Exposure to schistosomiasis is a health hazard for U.S. citizens who travel to endemic areas of the Caribbean, South America, Africa, and Asia. Outbreaks of schistosomiasis have occurred among adventure travelers participating in river trips in Africa, as well as among resident expatriates such as Peace Corps volunteers in high-risk areas. Those at greatest risk are travelers who engage in wading or swimming in or bathing with fresh water in areas where poor sanitation and appropriate snail hosts are present. Preventive Measures No vaccine is available; nor, at this time, are there any available drugs known to be effective as chemoprophylactic agents. Because there is no practical way for the traveler to distinguish infested from noninfested water, travelers should be advised to avoid fresh-water wading or swimming in rural areas of endemic countries. In such areas, heating bathing water to 50° Celsius (122° Fahrenheit) for 5 minutes or treating it with iodine or chlorine in a manner similar to the precautions recommended for preparing drinking water will destroy cercariae and make the water safe. Thus, swimming in adequately chlorinated swimming pools is virtually always safe, even in endemic countries. Filtering water with paper coffee filters can also be effective in removing cercariae from bathing water. If these measures are not feasible, travelers should be advised to allow bathing water to stand for 3 days because cercariae rarely survive longer than 48 hours. Vigorous towel drying after accidental exposure to water has been suggested as a way to remove cercariae in the process of skin penetration. Although toweling can prevent some infections, to recommend this to travelers might give them a false sense of security; it is far safer to recommend avoiding contact with contaminated water. Upon return from foreign travel, those who might have been exposed to schistosome-infested fresh water should be advised to undergo screening tests. Treatment Safe and effective oral drugs are available for the treatment of schistosomiasis. Travelers should be advised to contact an infectious disease or tropical medicine specialist. Occurance: Africa:
Southern Africa; Sub-Saharan Africa; Lake Malawi; the Nile
River valley in Egypt: |