Schistosomiasis: The waterborne threat

CEBU, Philippines - The Philippines is one of the areas most plagued by schistosomiasis. The disease has a long history in the country. Available records trace it back to 1906.

The website www.gideononline.com cited that 12,273 cases of schistosomiasis were officially reported in 1988. Of those cases, 301 deaths were reported. A 2005 report recorded a high prevalence rate (36 percent) of the disease in rice farming villages of Leyte. 

It is estimated that about 10 million people live in areas where schistosomiasis is prevalent. The disease often result in complications involving the heart, kidneys, liver, brain and eyes, which are still present in many of those subject areas, particularly in remote villages with poor treatment coverage. For the past 30 years, mass treatment of people, utilizing the drug praziquantel, has been the main method of control in the country.

Problems such as growth retardation, malnutrition, anemia, and poor cognitive function also persist in infected children.

In 2000, an 'outbreak' was reported in Davao del Sur, with 222 cases mostly in the barangays of Digos- Igpit, Colorado, and Mati. As of 2010, the country had an estimated 560,000 persons infested.

There is now strong evidence that large mammals, like cows and carabaos, contribute significantly to the transmission of the disease. Infection is also common among dogs and rats (particularly in Leyte). Given the very nature of schistosomiasis in the Philippines, it appears that the disease will not be controlled by human mass treatment with praziquantel alone. There is a need for innovative cost-effective strategies to control schistosomiasis in the long term.

Back in the 1970s, schistosomiasis was prevalent in Mindoro Oriental and Sorsogon in Southern Luzon, the provinces of North, East and Western Samar, Leyte, Bohol, and all the provinces of Mindanao with the exception of Misamis Oriental, Davao Oriental and Maguindanao. The disease is currently most common in Bohol, coastal Mindanao, Samar and southeastern Luzon.

Schistosomiasis is an infection caused by blood fluke, specifically Schistosoma japonicum. An individual may acquire the infection from fresh water contaminated with larval cercariae, which develop in snails. Infected yet untreated individuals could transmit the disease through discharging schistosome eggs in feces into bodies of water.

Long term infections can result to severe development of lesions, which can lead to blockage of blood flow. The infection can also cause portal hypertension, which can make collateral circulation, hence, redirecting the eggs to other parts of the body.

Schistosomiasis is still endemic in 12 regions with 28 provinces, 190 municipalities, and 2,230 barangays. Approximately 12 million people are affected and about 2.5 million are directly exposed

Schistosomiasis is a disease of poverty that leads to chronic ill-health. The microscopic adult worms live in the veins draining the urinary tract and intestines. Most of the eggs they lay are trapped in the tissues and the body's reaction to them can cause massive damage.

Many symptoms of schistosomiasis infection frequently include fever, blood in stools or urine, and abdominal discomfort, as well as a cough and an itchy, red, blotchy and raised rash. But many people with schistosomiasis don't have any symptoms, or don't experience any for several months or even years.

It is advisable to visit the doctor once the symptoms are observed, and if one has travelled to places known for schistosomiasis occurrence. The disease is diagnosed by the identification of characteristic eggs in feces, urine, or biopsy samples. Diagnosis may be aided with blood tests.

(Other References: www.ijidonline.com, www.cdc.gov, www.nhs.uk, www.who.int)