Sunday, October 25, 2020

Answer to Case 612

 Answer to Parasite Case of the Week 612: fly larva (maggot), Lucilia species. By using a pictorial key from the CDC website, I would say that this is most likely Lucilia (Phaenicia) sericata, the common green bottle flyThe presence of three spiracular slits indicates that this is a third instar larva (second instar larvae each have 2 slits). 

Congratulations to the many viewers who wrote in with the correct answer! As nicely explained by Idzi, Jeff, Florida Fan and Kosta, the appearance of the spiracular plate (straight slits, complete peritreme), and lack of an accessory oral sclerite points to this being Lucilia rather than Calliphora sp. 

This fly is found in most regions of the world, and feeds on dead, decaying tissue. There are several interesting features of L. sericata that are worth mentioning:

1. It is a cause of facultative myiasis in humans and animals.

2. It feeds on carrion, and is commonly used in forensic entomology to estimate the time of death.

3. It is used for maggot therapy in humans, as the larvae will effectively feed on necrotic tissue and thus aid in wound debridement. Maggots are specially raised for this purpose and disinfected prior to use. You can see some 2nd instar Medical Maggots (TM) that were sold for human maggot therapy HERE.

Florida Fan commented on how challenging it can be to get a picture perfect image of the spiracular plates. Emily and I learned at the London School of Hygiene and Tropical Medicine how to carefully prepare fly larvae for mounting to create truly beautiful preparations. However, for routine clinical use, we also like to play around with foam and applicator sticks to position the larva just right under the camera. 

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