An outbreak of schistosomiasis, or bilharzia that affected dozens of school children at Maradu Primary School in Francistown, Botswana is reportedly under control, according to Dr Gobezie Solomon, coordinator of the District Health Management Team (DHMT) of Greater Francistown.

Image/Alvaro1984 18
Image/Alvaro1984 18

The outbreak that began in mid-May resulted in 42 positive cases of schistosomiasis. All the 42 cases were registered at Maradu Primary School.

“When we interviewed the affected pupils after the outbreak they revealed that they had gone for swimming at the stagnant shallow pools along the Tati River,” said Solomon. Nearly 600 pupils were tested and 42 were positive for the blood fluke.

According to the World Health Organization, the invading parasites in Botswana are Schistosoma mansoni and S. hematobium. Prevalence rates fluctuate depending on rainfall and have been as high as 80% or as low as 20% in defined geographical areas. Since 1983, shistosomiasis control has been integrated into the primary health care services and this has kept the disease under control.

The health district reports having enough medication to treat those that are sick. Dr Solomon said, “We can go on mass treatment if the prevalence goes beyond 20%.” The current prevalence stands at 6 percent.

Educational efforts are taking place to warn parents about bilharzia. In addition, churches in the area are advised not to baptize members using water from the Tati river.

Schistosomiasis is second only to malaria in terms of socioeconomic and public health importance, with 200 million people infected in approximately 75 countries.

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Schistosomiasis is an acute or chronic disease; it is not a single disease, but a disease complex initiated by several different species of schistosomes. The three most important human species are Schistosoma mansoniS. haematobium and S. japonicum.

It is also considered a “man-made” disease, frequently associated with the development of irrigation and hydroelectric projects in developing countries.

Geographically, the three species are found in Africa (S.mansoni and S. haemotobium), the Middle East (S. haemotobium), the Arabian Peninsula, Brazil, Suriname, Venezuela and the Caribbean (S. mansoni) and China, the Philippines and parts of Indonesia (S. japonicum).

The schistosomes are found in fresh water. This water gets contaminated by infected people working in the rice field, fisherman in the lake or children playing who indiscriminately defecate or urinate in the water.

Schistosomes have a very complicated life cycle. The eggs in the feces or urine hatch and the ciliated miracidia swim to the specific snail species where it penetrates and goes through a couple of stages in the snail. After a period, thousands of the infective stage are released and swim around looking for a human to infect.

Schistosoma haemotobium egg Image/CDC

Schistosoma haemotobium egg

The free-swimming cercariae are capable of penetrating the unbroken skin of the human host.
In the human, the adult schistosomes eventually end up in the blood vessels of the intestines (S. mansoni and S. japonicum) or bladder (S. haemotobium). Here they produce eggs, which are the cause of the disease.

The pathology of S. mansoni and S. japonicum may include Katayama fever, hepatic perisinusoidal egg granulomas, Symmers’ pipe stem periportal fibrosis, portal hypertension, and occasional embolic egg granulomas in brain or spinal cord. People, especially children are characterized with a large distended abdomen due to enlarged liver and spleen.

Pathology of S. haematobium schistosomiasis includes hematuria (blood in the urine), scarring, calcification, squamous cell carcinoma, and occasional embolic egg granulomas in brain or spinal cord.

Those at greatest risk are travelers who wade, swim, or bathe in freshwater in areas where sanitation is poor and the snail hosts are present.

Blood flukes in Black and White : T-shirts, coffee mugs and other merchandise with a clean, computerized image of the three schistosomes

Schistosomiasis can be diagnosed by identifying the characteristic eggs in stool samples, biopsy of tissue, rectal (all) or bladder (S. haemotobium only). If eggs cannot be found in stool samples, antibody detection tests are available.

The drug of choice is praziquantel for infections caused by all Schistosoma species.

There is not a vaccine or any other prophylaxis available for prevention of schistosomiasis.

Prevention is by avoiding fresh water. According to the CDC, because there is no practical way to distinguish infested from noninfested water, travelers should be advised to avoid wading, swimming or other contact with freshwater in disease-endemic countries.