Biology Reference
In-Depth Information
component, suggesting encroachment and potential sequestration by
parasitized red cells in the lung in vivax malaria ( Anstey et al., 2007 ).
The few published twentieth century reports of autopsy in vivax malaria
showed overall little evidence for microvascular accumulation of vivax-
infected RBCs (see Anstey et al., 2009 ; Ewing, 1901 ; Billings and Post,
1915 ; Bruetsch, 1932 for review), though one described isolated 'intra-
capillary masses of swollen, infected erythrocytes and pigment'( Billings
and Post, 1915 ) and another 'frequent…mature malaria parasite(s) within
a red blood cell…taking up the entire lumen in immediate contact with
the endothelial cell'( Bruetsch, 1932b ) in at least some vessels in the brain,
and 'an unusually large number of infected red cells, young plasmodia
and pigment' in intestinal submucosal vessels ( Bruetsch, 1932b ). These
findings were not seen in other early autopsy studies ( Clark and Tomlin-
son, 1949 ). Ocular histopathology in a later fatal case of vivax-associated
coma reported accumulation of P. vivax -parasitized erythrocytes, includ-
ing schizonts within retinal and choroidal blood vessels, however, ante-
mortem peripheral blood showed a mixed infection with P. falciparum ,
with the latter likely to explain the histopathology reported ( Biswas
et al., 1996 ).
In contrast, a recent autopsy of fatal ARDS in vivax malaria before any
antimalarial treatment showed no evidence for pulmonary or other organ
sequestration ( Valecha et al., 2009 ). In the largest autopsy study to date, from
Manaus Brazil, the majority of patients had received antimalarial treatment
before death ( Lacerda et al., 2012 ). In one of the two cases with ARDS (one
of six with lung edema), scanty parasitized red cells were seen in alveolar
capillaries despite antimalarial drug clearance of parasites from peripheral
blood ( Lacerda et al., 2012 ). Published placental histology is even more lim-
ited, but has not shown placental accumulation of P. vivax -infected red cells
to date ( McGready et al., 2004 ). Taken together, the autopsy findings suggest
that significant microvascular obstruction from sequestration of parasitized
red cells does not appear to occur in vivax malaria, though it is possible that
in some circumstances, more limited cytoadherence to endothelial cells may
occur, and may amplify local inflammatory responses in affected organs,
such as the lung or placenta.
Rosetting, adherence of non-infected to infected RBCs, has been
linked to the pathophysiology of severe falciparum malaria ( Carlson
et al., 1990 ). Rosetting has been described ex vivo in vivax malaria
( Udomsanpetch et al., 1995 ), however, its role in vivax pathophysiology
is unknown.
Search WWH ::




Custom Search