Page 205 - Textbook of Pathology, 6th Edition

189 Infectious and Parasitic Diseases

CHAPTER 7

Figure 7.12 Malarial parasite in blood film—various stages of two main species, P. vivax and P. falciparum.

i) It does not have exo-erythrocytic stage. 2. In falciparum malaria, there is massive absorption of
ii) Erythrocytes of any age are parasitised while other haemoglobin by the renal tubules producing blackwater
plasmodia parasitise juvenile red cells. fever (haemoglobinuric nephrosis).
iii) One red cell may contain more than one parasite. 3. At autopsy, cerebral malaria is characterised by
iv) The parasitised red cells are sticky causing obstruction congestion and petechiae on the white matter.
of small blood vessels by thrombi, a feature which is 4. Parasitised erythrocytes in falciparum malaria are
responsible for extraordinary virulence of P. falciparum. sticky and get attached to endothelial cells resulting in
The main clinical features of malaria are cyclic peaks of obstruction of capillaries of deep organs such as of the
high fever accompanied by chills, anaemia and brain leading to hypoxia and death. If the patient lives,
splenomegaly. microhaemorrhages and microinfarcts may be seen in the
MORPHOLOGIC FEATURES. Parasitisation and destruc- brain.
tion of erythrocytes are responsible for major pathologic The diagnosis of malaria is made by demonstration of
changes as under (Fig. 7.11,B): malarial parasite in thin or thick blood films or sometimes
1. Malarial pigment liberated by destroyed red cells in histologic sections (Fig. 7.12).
accumulates in the phagocytic cells of the reticulo- Major complications occur in severe falciparum malaria
endothelial system resulting in enlargement of the spleen which may have manifestations of cerebral malaria (coma),
and liver (hepatosplenomegaly). hypoglycaemia, renal impairment, severe anaemia,