Biology Reference
In-Depth Information
Figure 2.4
Relapse patterns in volunteers in the USA who were infected by a single
mosquito bite with the Chesson strain of
P. vivax
studied by Coatney et al. (
1950
). Some
were rechallenged as indicated. Late relapses are highlighted. For colour version of this
igure, the reader is referred to the online version of this topic.
simple numerical probability; simultaneous activation of several hypnozo-
ites will shorten the relapse interval because the interval is measured until
the progeny of the most rapidly growing parasites cause patent infection.
There is natural phenotypic variation even amongst genetically identical
organisms. It is the progeny of the earliest activated and most rapidly mul-
tiplying parasite that become patent first. In natural settings, multiple geno-
typically distinct (i.e. heterologous) hypnozoites may be activated but, on
many occasions, only one or two genotypes will be detected subsequently
at clinical relapse. The other hypnozoites' progeny may reach patency later,
or in symptomatic relapses, asexual growth may be suppressed by fever, ill-
ness, immune responses, and treatment such that they never reach patency.
The second factor lengthening inter-relapse intervals in artificial infections
was the acquisition of blood-stage immunity against the single infecting
