Schistosomiasis is still endemic in parts of the Philippines

The eggs of Schistosoma japonicum are large and more rounded than other species, measuring 70-100 µm long by 55-64 µm wide. The spine on S. japonicum eggs is smaller and less conspicuous than other species. Eggs are shed in stool.

Schistosomiasis was first recognized clinically in the Philippines in the early years of the 20th century. However, unlike some other Asian countries like Thailand and Japan who haven’t seen a new case of the parasite in decades, the Philippines still have many areas where the parasite is endemic.

The latest information from the National Center for Disease Prevention and Control show that schistosomiasis is endemic in 28 of the 79 provinces in the country, particularly among rice farmers and fishermen.

In the Philippines, schistosomiasis is third only to malaria and tuberculosis in terms of causes of morbidity.

There are five species of Schistosoma that cause schistosomiasis in humans; Schistosoma japonicum, S. mansoni, S. haemotobium, S. mekongi and S intercalatum. S. japonicum is the species found in the Philippines.

Schistosomiasis is an acute or chronic disease, produced by parasites called Schistosoma. It is not a single disease, but a disease complex.

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.

The cercariae is the infective stage of the parasite.

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 problems with schistosomiasis are many and can include; S. mansoni and S. japonicum: 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

Distended abdomen is frequently seen in schistosomiasis

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.

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 swimming and other contact in fresh water in areas that are endemic
  • Schistosomiasis can also be transmitted through drinking contaminated water. Boiling water for 1 minute will kill the parasite.
  • Untreated piped water coming directly from canals, lakes, rivers, streams or springs may contain cercariae, but heating bathing water to 50° C (150° F) for 5 minutes or filtering water with fine-mesh filters can eliminate the risk of infection. In addition, allowing bath water to stand for 2 days is effective because cercariae rarely remain infective longer than 24 hours.

 To see a map of the Philippines to see where the endemic areas are, click here

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About Robert Herriman 3 Articles
I've been a Medical Technologist/Microbiologist for 25 years both in the US and overseas. Worked and lived in the Philippines in the 1980s while stationed at Clark AB. My interests include writing and reading about the diagnosis, control and prevention of infectious diseases of all types.