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Updates and Corrections to Medical Protozoology Fall 2006

October 16, Questions

I had a question about cryptosporidium. I'm studying it right now and I was
wondering what does it mean when you say the oocysts are "robust"? This is in
reference to the factors that contribute to waterborne cryptosporidiosis. Just's always easier for me to remember stuff when you know what it

By 'robust' I mean that they survive well in the environment. The relatively thick oocyst wall of the coccidian parasites makes them more resistant to desiccation and other environmental factors.

I was just skimming my notes and noticed it says in one place that p vivax and
ovale do NOT relapse, however I thought that those were the only two species of
plasmodium to be able to undergo relapse and that all 4 can under recrudesence.
Can you clarify?

In malaria relapse refers to the hyponoite stage--the dormant form found in the liver stage of P. vivax and P. ovale. Recrudescence refers to the situation in which the parasitemia drops below patency and then later rises to detectable levels again. All 4 species exhibit recrudescences, whereas only P. vivax and P. ovale exhibit relapses. Sorry about the confusion.

Also, what is the incubation for malaria?

The incubation period refers to the time after infection until clinical symptoms appear. The prepatent period refers to the time after infection until parasitemia appears. These will differ for the different species of Plasmodium. See the table at: