Biology Reference
In-Depth Information
malarias, notably
Plasmodium cynomolgi
, which has often been used as an
animal model of vivax malaria.
2. HISTORY
2.1. European and North American Vivax Malaria
The propensity of
P. vivax
malaria to relapse was recognised well over
100 years ago (
White, 2011
). Precise observations describing latencies of
some 8-9 months between primary illness and relapse were complemented
by detailed prospective epidemiological observations conducted in the vil-
lage of Wormeveer in The Netherlands by Korteweg. His observations,
and later entomological studies of Swellengrebel et al., indicated that the
early summer peak of vivax malaria preceded abundance of vector mosqui-
toes, and therefore, had been acquired in the autumn of the previous year
(
Korteweg, 1902
;
Swellengrebel et al., 1936
;
Swellengrebel and De Buck,
1938
;
Winckel, 1955
;
Gill, 1938
) (i.e. the incubation period was 9 months)
(
Fig. 2.1
). A much clearer understanding of relapse in
P. vivax
malaria came
from Julius Wagner-Jauregg's discovery that malaria could cure neurosyphi-
lis. Between the 1920s and the 1950s, thousands of patients confined in
mental hospitals with neurosyphilis were treated with malaria (malaria ther-
apy). The majority of the malaria therapy experience was with a relatively
small number of parasite 'strains' transmitted either by blood passage, or
more usually by the bites of several infected anopheline mosquitoes. Recur-
rences of vivax malaria commonly occurred many months after apparently
successful treatment of the primary infection. Furthermore, whereas recur-
rence in blood-transmitted vivax malaria could be prevented by curing the
blood stage infection, recurrence in mosquito-transmitted vivax malaria
could not (
Hackett, 1937
;
Bignami, 1913
;
Yorke and MacFie, 1924
;
Yorke,
1925
;
James, 1931a
;
James et al., 1936
;
James and Shute, 1926
). This pointed
to an exoerythrocytic stage of malaria, but its location was unknown. The
Dutch malariologists showed that their indigenous
P. vivax
could have a
short incubation period if patients were bitten by a large number of infected
mosquitoes, but by self-experimentation, they proved that bites by one or
two infected mosquitoes were followed by vivax malaria 8-9 months later
(
Schuffner et al., 1929
). Importantly, it was also noted in The Netherlands
that relapse rates (proportion of incident infections which are followed by
a relapse) in naturally acquired infections were higher than with mosquito-
transmitted malaria therapy with local 'strains' despite their higher inoculum
