Monday, March 18, 2024

Case of the Week 741

Wow, we are already on our 3rd filarial case! The following lovely case from Idzi Potters and the Institute of Tropical Medicine, Antwerp, is another microfilaria found in blood. 

The patient is a middle aged male farmer from Central America who was noted to have mild eosinophilia on routine complete blood count. He is otherwise asymptomatic. The microfilariae measure approximately 175 micrometers in length. What is your identification?


Eagleville said...

Onchocerca volvulus

Anonymous said...

The first case of the series taught me a lesson. The width of this microfilaria is smaller than the surrounding neutrophils and its length is shorter than 200 micrometers. On top of that, it doesn’t have a sheath. All the above guide me to Mansonella species. The tail of the microfilaria is not blunt and leads me away from Mansonella perstans. The tail also is not curved like a hook, this detail eliminates Mansonella streptocerca. I am left with the only candidate Mansonella ozzardi which also fits the given geographic location. Other details gave us the specimen being blood not skin, no river nor eye infection involved.
I am more confident to go with Mansonella ozzardi.
Florida Fan

jebarnes said...

So based on size alone, I would consider one of the Mansonellas. Perstans and ozzardi are the ones found in blood and in South America. As best as I can tell, the nuclei go to the end of the tail, so I would choose Mansonella perstans.

Anonymus said...

Agreed. Mansonellosis infections are thought to have little pathogenicity and to be almost always asymptomatic, particularly among individuals living in endemic regions. Tthree filarial species are considered responsible for causing human mansonellosis: Mansonella perstans, Mansonella streptocerca, and Mansonella ozzardi. M. streptocerca has characteristic hooked tail which is not seen in the present pictures. The microfilaria of M. ozzardi closely resemble those of M. perstans. M. ozzardi microfilaria are reported to be 163–203×3–5 μm, with long thin pointed tails and body nuclei that do not extend to the tips of their tails. The microfilariae of M. perstans are reported to be longer (200×4–5 μm), to have blunt rounded tails with nuclei extending to the tips. This leads me to M. ozzardi here.