Schistosoma haematobium

Schistosoma haematobium is a species of trematode flatworm, more commonly known as a fluke that can be found in Portugal, the Middle East, Africa, and India. This species is one a few fluke species that can give humans schistosomiasis, most commonly the kind known as urinary schistosomiasis. This species will swim around in water in its larval form known as cercariae. In this stage of life, it is able to push through a human host’s skin when the host is swimming in contaminated waters. Once the larvae are in the host, they will travel through the blood stream and reside in the liver until they develop into adult flukes. Adults are able to hide themselves from the host’s immune system by covering themselves in the body’s own antigens.

Once young Schistosoma haematobium flukes are about three weeks of age, they travel to the bladder of their human host to breed, after which females can lay up to three thousand eggs per day. These eggs move to the lumen, which is located in the bladder, and the uterus in female hosts. These eggs are then released back into bodies of water, where they will begin their life cycle again. After the eggs hatch and develop into swimming miracidia, they will enter a snail, which is their intermediate host. Common fresh water snail host species include B. nyassanus, B. globosus, B. truncates, and B. forskalii. Once the newly hatched larvae are within the snail, they will shed their epithelium and develop into sporocysts. After two weeks in this stage, the sporocysts will begin to form “daughter” sporocysts, and after two more weeks, cercariae larvae begin to enter the water. The larvae will swim to the surface of the body of water and will sink to the bottom if they do not find a human host within three days.

Humans infected by Schistosoma haematobium show many symptoms including ulceration near the muscularis propria, where the worms enter, and acute inflammation. Other effects caused by this parasite include granulomas, inflammation of the genitals in both males and females that can lead to HIV, and hydronephrosis. When the worm lays egg in the liver, it responds with hypersensitivity. This reaction is needed for the protection of hepatocytes, which are important liver tissues. It is relatively easy to diagnose a human host with a Schistosoma haematobium infection by means of a urine test. However, if the urine does not hold any eggs or an infection has reached the chronic stage, an injection of schistosome antigen can be used. This injection creates a wheal that allows doctors to detect an infection of adult worms. The most common treatment for an infection is the medicine praziquantel, which is a derivative of quinolone. Prevention against infection is important, but difficult because many bodies of water within the worm’s range are human waste dumpsites.

Image Caption: Histopathology of schistosomiasis haematobia, bladder Histopathology of bladder shows eggs of Schistosoma haematobium surrounded by intense infiltrates of eosinophils. Parasite. Credit: Wikipedia