Answer to Case 591

Answer to Parasite Case of the Week 591: L3 larva of PhormiaspeciesAs Blaine mentioned, this is a case of facultative myiasis involving an existing wound. The wound was caused by removal of the eye due to a large cancerous growth. What I didn ' t share is that the growth had been neglected, and the wound may have been as well. Several of you mentioned that this is a third stage (L3) larva, which indicates that the larva was allowed to mature for sometime within the wound.Although we can ' t see the tracheal trunks to say if they are pigmented or not, the posterior spiracular plate is clearly visualized and shows an incomplete peritreme, relatively-straight slits without lateral swellings, and slits are directed towards the region where the peritreme is incomplete, consistent withPhormiasp.Some of you mentionedLuciliasp. in the differential, although in my interpretation,Luciliahas a complete peritreme with distinct button, unlike what we are seeing here.The CDC hasfreely-available pictorial keys online which are a useful starting place when examining fly larvae. Blaine and I also published a guide forLaboratory Identification of Arthropod Ectoparasites. If you don ' t have access to manuscript, send me an email and I can send you a copy for your own personal use.
Source: Creepy Dreadful Wonderful Parasites - Category: Parasitology Source Type: blogs