Biology Reference
In-Depth Information
Abstract
Vivaxmalariawashistoricallydescribedas'benigntertianmalaria'becauseindividual
clinicalepisodeswerelesslikelytocausesevereillnessthan
Plasmodium falciparum.
Despitethis,
Plasmodium vivax
was,andremains,responsibleformajormorbidityand
significantmortality invivax-endemicareas.Single infectionscausing febrile illness
in otherwise healthy individuals rarely progress to severe disease. Nevertheless, in
thepresenceofco-morbidities,
P. vivax
cancausesevere illnessandfataloutcomes.
Recurrent or chronic infections in endemic areas can cause severe anaemia and
malnutrition, particularly in early childhood. Other severe manifestations include
acute lung injury, acute kidney injury and uncommonly, coma. Multiorgan failure
and shock are described but further studies are needed to investigate the role of
bacterialandotherco-infectionsinthesesyndromes.Inpregnancy,
P. vivax
infection
cancausematernalanaemia,miscarriage, lowbirthweightandcongenitalmalaria.
Compared to
P. falciparum
,
P. vivax
has a greater capacity to elicit an inflammatory
response, resulting in a lowerpyrogenic threshold.Conversely, cytoadherenceof
P.
vivax
toendothelialcellsislessfrequentandparasitesequestrationisnotthoughtto
beasignificantcauseofsevereillnessinvivaxmalaria.Withapredilectionforyoung
redcells,
P. vivax
doesnotresultinthehighparasitebiomassassociatedwithsevere
diseasein
P. falciparum
,butafourtofivefoldgreaterremovalofuninfectedredcells
fromthecirculationrelativeto
P. falciparum
isassociatedwithasimilarriskofsevere
anaemia. Mechanisms underlying the pathogenesis of severe vivax syndromes
remainincompletelyunderstood.
1. INTRODUCTION
Globally,
Plasmodium falciparum
is responsible for the majority of
uncomplicated febrile illness, as well as severe and fatal malaria, and has
therefore overshadowed the clinical and public health importance of vivax
malaria (
Baird, 2007
;
Price et al, 2007b
). Despite this,
Plasmodium vivax
is
a major cause of morbidity, accounting for almost half of all malaria cases
outside of Africa. Each year, there are between 70 and 390 million clinical
vivax infections (
Price et al., 2007b
) (reviewed in Chapter 1).
Because individual clinical episodes of malaria due to
P. vivax
infec-
tion were less likely to cause severe illness than
P. falciparum
(
Marchi-
afava and Bignami, 1894
), vivax malaria was historically described as
'benign tertian malaria' (
Manson, 1900
). However this relative term is
misleading since
P. vivax
was (
Dobson, 1997
), and remains (
Price et al.,
2009
), responsible for major morbidity and attributable mortality in
vivax-endemic areas. The spectrum of disease associated with
P. vivax
infection ranges from asymptomatic parasitaemia (
Luxemburger et al.,
1996
;
Gamage-Mendis et al., 1991
;
Karyana et al., 2008
;
Harris et al.,
