What are Schistosomes and How do they Infect Us?
To start, what are Schistosomes? According to Science Direct, 1 adult schistosomes are grayish-white flatworms that are about 7 to 20 mm long. Eggs called Miracidia are released into the water through feces and urine. They hatch and then go onto penetrate the skin of snails.
At an adolescent age the parasites are released from the snails and and are able to swim freely, they are known as Cercariae. During the penetration of the human skin the Cercariae lose their tails and reach adulthood, they are then known as schistosomula.
The schistosomula then enter the bloodstream and come to rest near the liver, intestines or genitals; each causing a different form of schistosomiasis. The worms pair together and mate for life, laying eggs which are released through urine and feces, beginning the life cycle over again.
What is Schistosomiasis?
Schistosomiasis is a disease caused by the parasitic blood fluke, schistosoma. Schistosomes in Sub-Saharan Africa cause both intestinal and urogenital schistosomiasis. There are five different species of schistosomes but, the two that terrorize Sub-Saharan Africa are S. Mansoni and S. Haematobium. They cause Intestinal and Urinary/Genital Schistosomiasis.
The World Health Organization 2 states that most people are infected through contact with contaminated water. This would make it very common in underdeveloped countries especially those in Sub-Saharan Africa. WHO estimates “…that at least 91.4% of those requiring treatment for schistosomiasis live in Africa.”
Intestinal schistosomiasis is caused when schistosoma pairs come to rest in blood vessels in or near the intestines. Intestinal schistosomiasis often includes an array of symptoms ranging from minor to dire. This includes blood in feces, diarrhea, abdominal pain, further along the disease can enlargement of the liver.
If left untreated schistosomiasis can lead to a painful death. Those infected with Urogenital schistosomiasis face a similar fate. Telltale signs of urogenital schistosomiasis often include blood in urine, fibrosis of bladder and ureter and kidney damage. Long term infection can also result in bladder cancer, lesions on genitals, infertility and death.
How does this affect children?
Children in Sub-Saharan Africa are at a higher risk for infection of schistosomes and schistosomiasis. This is most likely because children are always playing in water, eating whatever they can, and have no thought or care for cleanliness. They may also be affected during their daily lives, usually through washing clothes, playing and taking baths.
Bio-med central 3 informs that school aged children are the mostly to receive schistosomiasis and die from the disease.
This is due to the large quantities of eggs and worms found in the overly exposed children. Infants are also prone to getting the disease during their first year of life. The only available treatment, praziquantel, is often used to treat school aged children.
This often leaves children younger and adults older exposed and in danger. Even with the treatment many school aged children do not receive the medication, allowing for re-contamination. The World Health Organization 2 has found that children infected with schistosomiasis have a different list of symptoms than the adults. Children are often found with anemia and both stunted growth and ability to learn. However, if the treatment is given quickly the effects can be reversed, if not they may be lethal.
What is being done?
In addition to the medication Praziquantel, a preventative chemotherapy drug, there are other ways to help minimize and reduce the spread and infection of schistosomes and schistosomiasis.
The CDC 4 warns travelers that there is no vaccine available at this time and lists way they can minimize their risk of being infected. The largest step is remembering to bring the water used for drinking or bathing to a boil for at least one minute to kill any parasites or contaminants.
It is also recommended to dry with a towel if accidentally exposed to contaminated water. These measures are also taking place in countries that have high infection rates, like those in Sub-Saharan Africa.
In order to help control and reduce the number of people infected, there is being extensive effort to remove the snails the parasites use for their life cycle. This has already worked in other areas like Egypt.
To review, schistosomes are parasitic blood flukes that burrow into the skin of humans, living in blood vessels and producing eggs which are released in urine and feces. These parasites cause schistosomiasis, that produces many different symptoms based on the location of the worms. Left untreated the end result is usually death. Children in Sub-Saharan Africa are at the greatest risk for infection. The only treatment, Praziquantel is usually available for school aged children. There is no vaccine yet available. Matters are being taken to help prevent and control schistosomiasis, such as eliminating the snail population where the schistosomes reside.
1 Science Direct.2015. “Impact of human schistosomiasis in sub-Saharan Africa” Retrieved March 20
2 World Health Organization. 2018. “Schistosomiasis- Fact Sheet” Retrieved March 19
3 Biomed Central. 2017. “Moving from control to elimination of schistosomiasis in sub-Saharan Africa: time to change and adapt strategies” Retrieved March 20
4 CDC. 2012. “Parasites-Schistosomiasis, Prevention and Control” Retrieved March 20