WHAT IS SCHISTOSOMIASIS?
Schistosomiasis (Bilharzia) is a parasitic worm infection. There are five related species that can infect humans. Worldwide, more than two hundred million people are infected with schistosomiasis. In most cases, the infection causes few symptoms.
The infection can be divided into four stages:
– Invasion stage
– Migration and maturation phase
– Phase of established infection
– Phase of severe chronic infection
During the invasion stage, the parasite’s larvae penetrate the skin. In some cases this is accompanied by itching on the skin after swimming in fresh water (a type of athlete’s foot).
The migration and maturation phase begins two to six weeks after infection. Acute schistosomiasis can develop during this phase. This is also called Katayama syndrome. This phase is often accompanied by fever. These disease symptoms are caused by the first eggs that produce the schistosoma. The symptoms consist of fever, tiredness, muscle pain, cough, shortness of breath, diarrhoea, weight loss, joint pain, redness on the skin, sometimes an enlarged liver or spleen.
The symptoms during the stage of an established schistosomiasis infection are caused by a reaction to the eggs of the parasite. The eggs can get stuck in the wall of the intestine or bladder. Symptoms of schistosomiasis in the intestines are blood and/or mucus in the stool, abdominal pain and diarrhea (sometimes dysentery). In bladder schistosomiasis we see blood in the urine. These symptoms appear several months after the initial infection.
In the phase of severe chronic infection in schistosomiasis, the eggs that were in the wall of the intestines and/or bladder have passed through the bloodstream to the liver and/or lungs. These symptoms appear months to years after the initial infection. With schistosomiasis in the intestines, this can lead to complaints of the liver, an enlarged spleen and esophagus problems. In bladder schistosomiasis, it can lead to bladder wall calcification and scarring, which can eventually lead to bladder cancer. Very rarely, the eggs pass into organs other than the bladder and intestines. For example, in the genitals or the nervous system. This can also cause long-term complaints, depending on where the eggs occur.
HOW DO YOU GET SCHISTOSOMIASIS?
Schistosomiasis occurs in fresh surface water in (sub)tropical areas. Most infections are contracted in sub-Saharan Africa, but schistosomiasis can also be contracted in other parts of Africa, parts of Latin America, the Caribbean, the Middle East, China, the Philippines and Southeast Asia.
Aquatic snails are the hosts for the parasite.
Contamination occurs when people swim in water in which these snails live or drink this (unboiled) water. The schistosomes can penetrate the skin and then spread through the bloodstream to other parts of the body. In that place they can nest and form eggs.
HOW TO PROTECT YOURSELF AGAINST SCHISTOSOMIASIS?
Schistosomiasis can be prevented by avoiding contact with fresh surface water. That means no swimming in rivers and lakes, even when the locals do.
In areas where schistosomiasis is common, it is also wise to avoid shower water when this water is taken from the lakes and rivers.
If you do come into contact with water, it is best to dry your skin immediately and do not allow it to air dry. Do this especially next to the edge of swimsuits, where water dries less quickly. It can prevent larvae that have not yet penetrated the skin from penetrating further.
You cannot prevent an infection with schistosomiasis by taking medication beforehand or right afterwards. When you are offered medication on site, for example by diving schools, you should not just take it. Vaccinatiecentrum.nl advises you to always contact a doctor after freshwater contact in the tropics to see what the best strategy is.
After exposure, we can perform a blood test for schistosomiasis at least six weeks after your return. There is no vaccine that protects against infection with schistosomiasis.
WHAT IS THE TREATMENT FOR SCHISTOSOMIASIS?
Diagnosis of schistosomiasis
If you suspect or if you have a certain infection of schistosomiasis, you can do a blood test for antibodies against the parasite at vaccinationcentrum.nl. This survey is carried out at least six weeks after the last freshwater contact. Once you have had a positive antibody test, tests will always remain positive afterwards. New infections can then no longer be detected with blood tests.
At vaccinationcentrum.nl we can in some cases also conduct research into eggs in urine or faeces. This can be done at least eight weeks after fresh water contact.
Treatment of schistosomiasis
In schistosomiasis, the drug praziquantel is usually administered. This medicine works against the adult worms and has little effect in the other stages. It is therefore pointless to take this preventively or immediately after contact with fresh water, because there are no adult worms present in the body.
In areas where schistosomiasis is common, treatment with praziquantel is sometimes performed periodically to counteract morbidity. This will not prevent new infections or infections that occurred less than six weeks ago.
People who have no symptoms, but who have had frequent contact with fresh water in an area where schistosomiasis is common, are advised to have a medical examination carried out at vaccinationcentrum.nl. This advice is given to expats, for example.
QUESTIONS OR MAKE AN APPOINTMENT?
Do you have questions or do you want to make an appointment for a (blood) test or medical examination? Mail us at email@example.com or call 085 – 90 20 303.