Fancy a swim with the snails? - Schistosomiasis

Fancy a swim with the snails?... think again.

Biomphalaria, Bulinus and Oncomelania are 17.9mm diameter snails that when comapred to an object are only as big as a US dime. Yet, are an essential part of causing the second most common parasitic disease worldwide; Schistosomiasis. Affecting over 240 million people and its 3 strains S. Heamatobium, S. Japonicum and S. Mansoni causing up to 200,000 deaths worldwide.

Second only to malaria, Schistosomiasis is prevelent in sub-saharan Africa, The Middle East, Asia and The Caribbeans and is a leading cause of disability-adjusted life years (DALYs). Okay okay enough big words Tehilla.. what actually is Schistosomiasis? Let me put things in context for you.

Mary, the average Nigerian woman living in the very poor area of Ebonyi state decides to go to the local stream to have her bath. Unbeknownst to her, her husband Jack had been there to ease himself in that same stream a few weeks beforehand. You see, within Jack's released faeces, there were microscopic traces of Miracidia eggs.

These eggs mature into ciliated Miracidia after asexually reproducing for 4-6 weeks. This is the first-stage of larva trematodes that hatch from the eggs into the water. These miracidia then enter the dime-sized snails as their intermediate host before transforming into Cercariae which are released by the snails. Think about Cercariae as "little swimmers". They are now adapted to movement and can penetrate human skin.

Now, when Mary is having her bath in the stream, the Cercariae penetrate her skin and transform into Schistosomula worms, using her as a human host. For the next 5-6 weeks, these Schistosomula migrate to her lungs before moving to other venous environments. Now, depending on the species of the worm, they can live in their host; Mary, for up to 5 years!

Although most infections are asymtopmatic, Schistoma dermatitis or "swimmers itch" is a common symptom as Schistosomiasis which occurs after the cercariae penetrate the skin with previously sensitised patients experiencing more pronounced symptoms.

Acute schistosomiasis causes something called Katayama fever several weeks after exposure. This leads to pretty intense symptoms such as hematochezia - blood passage through anus, hepatosplenamegaly - enlarged liver and spleen, hematuria - blood in the urine, abdominal pain, fever, chills and malaise. Bladder calcification and ureteral reflux also arises as a sign of kidney damage associated with the S. Haematobium strain.

When it comes to diagnostic testing, common markers are oesinophilia - raised white blood cell types, excreted eggs in serial urine and stool samples.

Dang! This all sounds HORRIBLE but fear not batman is coming to the rescue! Did I say batman? Lol, no. I meant Praziquantel! Praziquantel is a broad-spectrum antihelmentic that treats certain trematode diseases such as Schistosomiasis.

Real talk though mate, before booking that group backpacking trip to Thailand, make sure you DO NOT wade or swim in unclean water! Maybe have a cheeky pack of praziqunatel hahahaha!

Xoxo,

Tehilla.