A Night at the Lab: Thin Blood Smears

         Here is something fun from work this week. We don't often get positive malaria smears, but they do happen. The key to reading malarial smears is knowing what is not in normal blood.

         I have attached a nice CDC infographic about the malarial life cycle.

Background

         Pacific Islander male in his early 20's. No travel history in the last 30 days. Before anyone goes off about malaria at where he is from, the answer is no. There's no transmission of malaria in his home country. Patient has a history of malaria.

Thin Smears Under the Scope

         One of the tell-tale signs of malarial infection is seeing the trophozoites in ring stage. In this case, the "rings" look more like baskets, so there's a chance it's not Plasmodium falciparum.

         This is most likely the best-looking schizont I have ever seen in a patient sample. That's not saying much because a smear is a lower tech approach compared to all the methods available.

         At first glance, one could mistaken this for an enlarged lymphocyte. But, that is not a normal blood cell. It is likely to be a gametocyte from the parasite.

Conclusion

The patient definitely has malaria. The percent parasitemia was about 1%.

         The lab does not speciate the parasites at the general level. That is up to the pathologists and infectious disease specialists.

         If I were to guess, I would say P. malariae. This is due to the well-defined trophozoite rings and normal-sized blood cells. The gametocytes were large unlike other species.

         As to why does this young man have malaria? Well, that's some digging the infectious disease doctor would have to do.