Ring forms

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What is a ring form

• Ring cartoon.jpg

The earliest stage following red cell invasion has a typical ting form:

• a = chromatin dot
• b = digestive vacuole
• c = parasite cytoplasm

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Description

At the earliest stage of red cell infection parasites have a ring form and distinction between species may not be easy (or even possible); however, as the parasite mature and develop differences become more apparent. In some species the ring form is maintained until late stages of maturation, in others there is loss of a typical ring appearance

• P.falciparum Typically small and delicate, these ring forms tend to persist from early trophozoite until late stages, during this time they may thicken
• P.ovale Typically large and robust rings, but maintain a ring shape until late stages of development (contrast with P.vivax
• P.malariae Small but more substantial that P.falciparum, these parasites become more solid or bad like, losing the ring form as they develop
• P.knowlesi Early forms resemble P.falciparum, but as they mature they often extend and become solid or band-like resembling P.malariae
• P.vivax Early stages appear as rings, but then become irregular and eventually the more typical amoeboid appearance appears

These changes are illustrated for early and late trophozoite below:

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P.falciparum

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Small and often delicate rings at early stages, these thicken at later stages, although they remain relatively small with a "ring appearance"

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P.ovale

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Robust rings that enlarge during parasite development, although the ring form can often still be distinguished

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P.malariae

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Small but more robust than P.falciparum, the parasites become more solid as they develop and may extend as a band across the cells

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P.knowlesi

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  small or normal P.malariae (round)

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  normal sized P.falciparum (round)

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  ormal or enlarged P.ovale (may become ovoid)

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P.vivax

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  small or normal P.malariae (round)

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  normal sized P.falciparum (round)

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  ormal or enlarged P.ovale (may become ovoid)

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Species significance

These changes can be very helpful in identifying malaria species

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