Re: Lake Swimmer's Itch Caused by Parasites

Hi Shroom:

The person who wrote the article didn't specifically say what type of parasite. Since the parasite is usually carried by snails I'm guessing that it would be Schistosoma mansoni. However, it could also be one of the other parasites suggested below. I did a quick search and here's what I found:



http://cat.inist.fr/?aModele=afficheN&cpsidt=15120590


Planktonic cercariae (parasite larvae) of digenetic flatworms (Himasthla rhigedana) encyst up to 100% of intermediate host populations. Toward explaining such high prevalence, larval behavior and passive-transport processes were evaluated experimentally for their roles in waterborne parasite transmission.




Here's what the CDC says on symptoms:


http://www.cdc.gov/Ncidod/dpd/parasites/cercarialdermatitis/factsht_cercarial...


Cercarial dermatitis
(sir-CARE-ee-uhl der-muh-TIGHT-iss)
"Swimmer's Itch"

What is swimmer's itch?
Swimmer's itch, also called cercarial dermatitis, appears as a skin rash caused by an allergic reaction to specific parasites found in certain birds and mammals . These microscopic parasites are released from infected snails into fresh and salt water (such as lakes, ponds, and oceans). Rather than finding a host bird or mammal, the parasite instead burrows into the nearby swimmer's skin, causing an allergic reaction and rash. Swimmer's itch is found throughout the world and is more frequent during summer months.


How does water become infested with the parasite?

The adult parasite lives in the blood of infected animals such as ducks, geese, gulls, swans, and certain aquatic mammals such as muskrats and beavers. The parasites produce eggs that are passed in the feces of infected birds or mammals.

If the eggs land in the water, the water becomes contaminated. Eggs hatch, releasing small, free-swimming larvae. These larvae swim in the water in search of a certain species of aquatic snail.

If the larvae find one of these snails, they infect the snail and undergo further development. Infected snails release a different type of larvae ( cercariae , hence the name cercarial dermatitis) into the water. This larval form then swims about searching for a suitable host (bird, muskrat) so they can start the lifecycle over again . Although humans are not suitable hosts, the larvae burrow into the swimmer's skin, and may cause an allergic reaction and rash. Because these larvae cannot develop inside a human, they soon die. Tweet