7 topics with concise reviews: definitions, key facts, and class questions.
In this section, we analyze the sporozoans (phylum Apicomplexa)—obligate intracellular parasites whose evolution is tailored to the stealthy destruction of host cells. These are the causative agents of major vector-borne and opportunistic infections that physicians encounter in clinical practice.
We will systematically cover malaria plasmodia and the clinical presentation of malaria, examine babesias, and thoroughly study tissue and intestinal parasites: Toxoplasma, Sarcocystis, Isospora, and Cryptosporidium. Special attention is paid to the pathogenesis and laboratory diagnostic methods for each infection.
In classes and exams, professors are guaranteed to ask about the life cycles of sporozoans. The main stumbling block is the alternation of definitive and intermediate hosts, as well as the succession of reproduction forms (schizogony, sporogony). Be prepared to draw the development scheme of Plasmodium, differentiate its species in a blood smear, and clearly justify why Toxoplasma is specifically dangerous for pregnant women and immunocompromised patients.
Why are late relapses of the disease possible upon P. vivax infection?
Upon infection with P. vivax, a portion of the sporozoites in liver cells enters a dormant stage—hypnozoites. They can remain quiescent for weeks or months, and their subsequent activation causes late relapses.
What is the difference between a "thick smear" and a conventional smear in diagnostics?
In the "thick smear" preparation, blood is not fixed, which causes erythrocytes and the parasites themselves to become distorted. However, due to the larger blood volume, the pathogen concentration in the preparation is significantly higher, which simplifies its detection.
How to distinguish babesias from malaria plasmodia in a blood smear?
Babesias look very similar to young ring forms of plasmodia, but they are betrayed by asynchronous budding, the presence of paired forms, and specific tetrads—groups of four individuals inside an erythrocyte.
Primary infection during pregnancy (especially in the 1st trimester) causes a teratogenic effect, leading to fetal developmental defects, miscarriages, or severe CNS damage in the newborn.
Primary infection during pregnancy (especially in the 1st trimester) has a teratogenic effect by crossing the placenta. This can lead to severe developmental defects, fetal death, or the birth of a child with lesions of the central nervous system and internal organs.
Which stage of the pathogen is excreted with human feces?
Already matured oval-shaped sporocysts (10–16 µm in size) enter the external environment with feces. Inside each of them, there are four mature sporozoites.
What staining method is used to detect Isospora oocysts?
Ziehl–Neelsen staining is used to visualize oocysts. With this method, they stain pink.
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