Saturday, July 24, 2021

That tongue-twisting Schistosomiasis parasite

SCHISTOSOMIASIS is a parasitic disease that is carried by an intermediary agent, which is a snail.

The Center for Disease Control and Prevention (CDC) shares that Schistosomiasis is common to places with poor sanitation.

According the World Health Organization (WHO), the transmission of this parasite to humans occurs when: “[the] larval forms of the parasites, which are released by freshwater snail, penetrate the skin of the people [when in contact] with water”.

Furthermore, once in the human body, “the larvae develop into adult schistosomes, which live in the blood vessels”, it points.

“The females release eggs, some of which are passed out of the body in the urine or faeces [of humans]. Others are trapped in body tissues, causing an immune reaction.”

For Gerard Tortora, an authority figure in the field of microbiology and author of the ‘Microbiology: An Introduction’ informs that there are three primary types of Schistosomiasis, namely: Schistosoma haematobium, which causes inflammation of the urinary bladder; Schistosoma japonicum; and Schistosoma mansoi.

The latter two are known to cause intestinal inflammation.

“Depending on the species, Schistosomiasis can cause damage to many different organs when eggs migrate in the blood stream to different areas like the lungs, liver and the brain”, he explains.

Furthermore, the WHO maintains that Schistosoma japonicum is most common to China, Indonesia and the Philippines.

Tortora explains that the life cycle of Schistosomiasis begins as eggs that have hatched into free-swimming larvae called ‘miracidia’.

“Each ‘miracidium’ searches for a snail as an intermediary host to penetrate”.

“Once inside the snail, it reproduces to form a fork-tailed larva called ‘cercariae’, which are released into the water from the sanil”, he adds.

Free-swimming cercariae then await a human host on the water. Once a human dips into the cercarie-infested water, these microbes attach themselves to the skin- whether broken or unbroken- of the human victim then enter the body through the small pores.

Once inside the body, “the cercariae travel through the host’s circulatory system (blood and blood vessels through the pumping action of the heart) to the intestinal blood vessels, where they mature into adults”.

And then, “these carcariae lay their eggs in the liver, where they mature and copulate in a month’s time”.

Lastly, “eggs are being excreted in the feces or urine of the human host”, he concludes.

According to the health statistics of WHO, at least 250 million people around the globe required treatment for Schistosomiasis in 2017. Yet, this is an underestimation as actual figures remain unreported according to health authorities.

The Public Health Nursing in the Philippines, a manual published by the National League of Government Nurses states that as of 2007, Schistosomiasis is endemic in 10 regions, 24 provinces, 183 municipalities and 1, 212 barangays with estimated exposed population of 6.7 million all over the Philippines.

“There is a high prevalence of Schistosomiasis in Bicol, Samar, Leyte and Davao”, it adds.

“Signs and symptoms of Schistosomiasis include: diarrhea; bloody stools; enlargement of abdomen; spleenomegaly [enlargement of liver]; weakness; anemia; and inflamed liver.”

However, the recent updates of WHO informs that Tte classical sign of urogenital schistosomiasis is haematuria (blood in urine).

Confirmation involves “Laboratory diagnosis consisting of microscopic identification of the flukes or their eggs in fecal and urine specimens, intradermal tests, and serological tests such as complement-fixation and precipitin tests”, explains Tortora.

He adds: “Praziquantel is the drug of choice for Schistosomiasis but Oxamniquine may be used as alternative against Schistosoma mansoi”.

The CDC classifies Schistosomiasis as a Neglected Tropical Disease with impact that is rated as secondary to malaria in terms of devastation and threat to public health.

Furthermore, “it affects mostly farmers and their families in the rural areas and due to the chronicity [long-term nature] of the disease that results in manpower losses and lessened agricultural productivity making Schistosomiasis a socio-economic problem as well”, explains the Public Health Nursing in the Philippines.

As a government intervention, the Department of Health has instituted the Schistosomiasis Control Program, a health programme that has the following objectives: (1) Reduce prevalence rate by 50 percent in endemic provinces; and (2) increase the coverage of mass treatment of population in endemic provinces.

According to Ruth Martinez, program manager of the Schistosomiasis control program, it employs the following key interventions: (1) Morbidity control: Mass Treatment; (2) Infection Control: Active Surveillance; (3) Surveillance of School Children; (4) Transmission control; and (5) Advocacy and Promotion.

On the other hand, recent findings of WHO suggests that in women, urogenital schistosomiasis may present with a range of signs and symptoms including lesions of the cervix and vagina, vaginal bleeding, pain during sexual intercourse and nodules in the vulva. In areas endemic for urogenital schistosomiasis a large proportion of women may have female genital schistosomiasis (FGS)

A recent WHO working group concluded that there is biological plausibility that female genital schistosomiasis is a risk factor HIV transmission to women. It likewise points out that genital schistosomiasis also affects men, inducing pathology of the seminal vesicles, prostate and other organs. This disease may also have other long-term irreversible consequences, including infertility

On the other hand, the Public Health Nursing in the Philippines shares the following preventive measures: (1) people living in endemic areas must be educated regarding the mode of transmission and methods of protection; (2) dispose of feces and urine so that viable eggs will not reach bodies of fresh water containing intermediate snail host; (3) treat snail-breeding sites with molluscicides; (4) prevent exposure to contaminated water. If accidental exposure do occur, apply 70 percent alcohol immediately to skin to kill surface cercariae; and (5) travelers visiting endemic areas should be advised of the risks and informed about the preventive measures.

The DOH charts January as the Schistosomiasis Awareness month.


style="display:block; text-align:center;"


SunStar website welcomes friendly debate, but comments posted on this site do not necessarily reflect the views of the SunStar management and its affiliates. SunStar reserves the right to delete, reproduce or modify comments posted here without notice. Posts that are inappropriate will automatically be deleted.

Forum rules:

Do not use obscenity. Some words have been banned. Stick to the topic. Do not veer away from the discussion. Be coherent. Do not shout or use CAPITAL LETTERS!