Schistosomiasis - IVD Research, Inc.

Schistosomiasis is the second most prevalent tropical disease in the world, after Malaria. It is also known as bilharzia in honor of Theodore Bilharz, who first identified it. The reality behind Schistosoma infection covers hygiene education, quality of water, snail control and poverty. Schistosomiasis is endemic in 74 tropical countries, estimated to infect over 200 million people, with another 600 million people at risk of infection.

The main forms of human schistosomiasis are caused by 5 species of flatworm in the genus Schistosoma, within the class Trematode. The 5 species are as follows: S hematobium, Schistosoma mansoni, Schistosoma japonicum, Schistosoma intercalatum, and Schistosoma mekongi. The worms also are called blood flukes because they live in the vascular system of humans and other vertebrates.

Larval forms of the parasites, which are released by freshwater snails, penetrate the skin of people in contaminated water. The larval form of Schistosoma parasites are called Cercariae.

In the body, the larvae develop into adult schistosomes, which live in the blood vessels. The females release eggs, some of which are passed out of the body in the urine or feces. Others are trapped in body tissues, causing a severe immune reaction.

Often water contaminated with the urine or feces of infected people is used for bathing, thus transmission occurs and more people are infected. Education is needed in regions where this occurs. In urinary schistosomiasis, there is progressive damage to the bladder, ureters and kidneys. In intestinal schistosomiasis, there is progressive swelling of the liver and spleen, intestinal damage, and hypertension of the abdominal blood vessels.

Travelers are at risk if they travel to areas where the disease is endemic. In areas where the sanitation is poor and the snail hosts are present, bathing in contaminated waters is an extreme risk.

Diagnosis

Better diagnostic tests are need in the field, where microscopic examinations may be difficult. IVD Research manufactures a Schistosomiasis ELISA test for worldwide use, and is the top choice for many doctors and researchers in the field.

Many persons with chronic Schistosomiasis recall no symptoms of acute infection. Diagnosis of Schistosomiasis infection is usually confirmed by serologic studies or by finding schistosome eggs during microscopic examination of stool or urine samples. Schistosome eggs can be found 6-8 weeks after exposure, but are not always detectable. Serologic testing in an asymptomatic traveler should ideally be performed several months following exposure.

Treatment

Three drugs have recently aided the fight against Schistosoma infection:

Praziquantel - treatment of all forms of schistosomiasis, with virtually no side effects Oxamniquine - used exclusively to treat intestinal schistosomiasis in Africa and South America Metrifonate - effective for the treatment of urinary schistosomiasis

Prevention

Heating bathing water to 50° C (122° F) for 5 minutes or filtering water with fine-mesh filters can eliminate the drastically lower the risk of infection. If such measures can not be done, people should be advised to allow bathing water to stand for 2 days, because cercariae almost always lose their potential for infection after 24 hours.

Properly chlorinated swimming pools are not a threat, even in regions with 50% or most the population being infected. Strongly wiping a person's body down with a towel can prevent some infection and is better than nothing. Covering skin in DEET insect repellent has also shown to prevent infection, however the application wears off quickly.

Better education in areas where the disease in endemic can greatly reduce the incidence of infection. Water quality controls is needed in many areas where a high rate of the population is infected and do not have access to clean water.