Answer to Case 621

 Answer to the Parasite Case of the Week 621: Poikïlorchis (Achillurbainia) congolensis.

Wow, I am so impressed with how many of you got this identification. This rare parasite was first described in Nature in 1957 in a man from the Belgian Congo. 

From Idzi: Poikilorchis congolensis, or alternatively Achillurbainia congolensis -as the genus Poïkilorchis (Fain and Vandepitte, 1957) was regarded by Dollfus as a synonym of Achillurbainia (Dollfus, R. P., 1966. Personal communication).

As far as I have found in the literature, it has been described in humans only eight times up ‘till now, although some authors suggest that some of the reported cases of Paragonimus (especially in Africa) could be in fact cases of Poïkilorchis infection.

Although its hosts are not known for sure, Poïkilorchis congolensis is considered to be a zoonosis, with the common final host probably being leopards (and maybe also giant rats?) and intermediate hosts being probably freshwater crabs.

The infection typically produces subcutaneous retroauricular cysts, which contain as well the eggs as the adults. Nevertheless, in many (human) cases only eggs are found in the cyst.

In the literature, I found human cases in Central and West Africa, Sarawak (Malaysia), possible also one in China…

Idzi and the vial of of Poïkilorchis congolensis eggs.

As many of you noted, these eggs look like those of Diphyllobothrium/Dibothriocephalus spp., but the source is inconsistent with this identification. Similarly, the eggs resemble those of Paragonimus spp., but the size is too small. Other helminths that may be found in this location include cestode larvae (Taenia solium, Echinococcus granulosus complex), Lagochilascaris minor, and Gnathostoma spp., but none would have the appearance seen in this case.

So this is over all a fantastic case, and a great way to start off the new year! Thanks again to Idzi for donating this case.