Figure 2.8 Temporal pattern and genotyping of recurrences of vivax malaria in eight
mothers (upper panel) and nine infants (lower panel) studied on the NE border of Thai-
land ( Imwong et al., 2012 ). Each number on the vertical axis represents a patient. Filled
circles denote the initial infection. An open circle represents a genetically homologous
recurrence, and a black diamond, a genetically heterologous recurrence. Recurrences
where genotyping was indeterminate (two in infants, three in mothers) are not shown.
One mother's sole relapse was indeterminate. For colour version of this figure, the
reader is referred to the online version of this topic.
earlier experimental observations that some hypnozoites of frequent-relapse
phenotypes can remain dormant for long periods ( Coatney et al., 1950b ).
9.3. The Stimulus for Hypnozoite Activation
If acute malaria activates latent hypnozoites and thereby causes vivax
malaria relapses, then it seems that a significant systemic illness is neces-
sary for this activation. Formal studies to provoke relapses of vivax malaria,
which included forced route marches, simulated altitude, and induced