Cercaria

This article is about the flatworm life stage. For the genus of flatworms, see Cercaria (genus). For the genus of single-celled organisms, see Euglena.

A cercaria (plural cercariae) is the larval form of the trematode class of parasites. It develops within the germinal cells of the sporocyst or redia.[1] A cercaria has a tapering head with large penetration glands.[2] It may or may not have a long swimming "tail", depending on the species.[1] The motile cercaria finds and settles in a host where it will become either an adult, or a mesocercaria, or a metacercaria, according to species.

Cercarial infection in water borne environments has caused dermatologic burden to nearby swimmers and fisherman. The cycle as mentioned above, starts at the cercarial egg distribution whether fecal in route or from the nostril of a duck/geese. The snail or reservoir is the main home for the hatching of the miracidia that form into successive sporocysts. Released cysts travel and infect nearby fish or accidental hosts such as humans. This continued cycle from origin to host, is represented by a positive reinforcing loop. This species infection has been referred to as Cercarial dermatitis or "Swimmers Itch." In the fish ecosystem in varying populations the sunfish is infected beneath its scale bedding resulting in Black spot disease.

The further impact to investigate in this scenario is with repeated cercarial exposures human Ige levels may elevate. This situation could be detrimental to those susceptible to anaphylaxis, severe asthma or those battling an auto immunological condition.

One proposition to mitigate this scenario is to adequately control the population of the snails where human exposure is expected. That way there is better containment at the reservoir and a less Cercariae species burden that may affect aquatic and human populations.

References 1.CDC - DPDx - Cercarial Dermatitis. (2019, May 13). Www.cdc.gov. https://www.cdc.gov/dpdx/cercarialdermatitis/index.html

2.CDC. (2024, May 8). About Swimmer’s Itch. Swimmer’s Itch (Cercarial Dermatitis). https://www.cdc.gov/swimmers-itch/about/index.html

3.Kolářová, L., Horák, P., Skírnisson, K., Marečková, H., & Doenhoff, M. (2012). Cercarial Dermatitis, a Neglected Allergic Disease. Clinical Reviews in Allergy & Immunology, 45(1), 63–74. https://doi.org/10.1007/s12016-012-8334-y

4.The Real Truth About Black Spot Disease, and How It Affects Fish. (2018, January 8). Outdoor Canada. https://www.outdoorcanada.ca/black-spot-disease/

The term Cercaria is also used as a genus name in descriptions of species when only the larval form is known.[3]

Rotifers (Rotaria rotatoria) produce a chemical, Schistosome Paralysis Factor, suppressing cercaria swimming and reducing infections.[4]

References

  1. ^ a b "Glossary". VPTH 603 Veterinary Parasitology. University of Pennsylvania School of Veterinary Medicine. Archived from the original on 2011-07-18. Retrieved 2019-05-22.
  2. ^ "Schistosoma". Australian Society for Parasitology. Retrieved 19 February 2011.
  3. ^ "Cercaria Müller, 1773". WoRMS. World Register of Marine Species. 2023. Retrieved 2023-02-26.
  4. ^ Gao, Jiarong; Yang, Ning; Lewis, Fred A.; Yau, Peter; Collins, James J.; Sweedler, Jonathan V.; Newmark, Phillip A. (2019). Khosla, Chaitan (ed.). "A rotifer-derived paralytic compound prevents transmission of schistosomiasis to a mammalian host". PLOS Biology. 17 (10): e3000485. doi:10.1371/journal.pbio.3000485. ISSN 1545-7885. PMC 6797223. PMID 31622335.