Page 204 - Textbook of Pathology, 6th Edition

188 action of the trophozoite and have necrotic bed. Such
chronic amoebic ulcers are described as flask-shaped
ulcers due to their shape. The margin of the ulcer shows
inflammatory response consisting of admixture of poly-
morphonuclear as well as mononuclear cells besides the
presence of trophozoites of Entamoeba histolytica (Fig. 7.10).
Amoeboma is the inflammatory thickening of the wall
of large bowel resembling carcinoma of the colon.
Microscopically, the lesion consists of inflammatory
SECTION I
granulation tissue, fibrosis and clusters of trophozoites at
the margin of necrotic with viable tissue.
Amoebic liver abscess may be formed by invasion of
the radicle of the portal vein by trophozoites. Amoebic
liver abscess may be single or multiple (Chapter 21). The
amoebic abscess contains yellowish-grey amorphous
liquid material in which trophozoites are identified at the
junction of the viable and necrotic tissue.
Other sites where spread of amoebic infection may Figure 7.10 Amoebic colitis. Section from margin of amoebic ulcer
occur are peritonitis by perforation of amoebic ulcer of shows necrotic debris, acute inflammatory infiltrate and a few trophozoites
colon, extension to the lungs and pleura by rupture of of Entamoeba histolytica (arrow).
amoebic liver abscess, haematogenous spread to cause malariae. While Plasmodium falciparum causes malignant
amoebic carditis and cerebral lesions, cutaneous malaria, the other three species produce benign form of
amoebiasis via spread of rectal amoebiasis or from anal illness. These parasites are transmitted by bite of female
intercourse. Anopheles mosquito. The disease is endemic in several parts
of the world, especially in tropical Africa, parts of South and
MALARIA
Central America, India and South-East Asia.
Malaria is a protozoal disease caused by any one or The life cycle of plasmodia is complex and is diagram-
combination of four species of plasmodia: Plasmodium vivax, matically depicted in Fig. 7.11, A. P. falciparum differs from
Plasmodium falciparum, Plasmodium ovale and Plasmodium other forms of plasmodial species in 4 respects:
General Pathology and Basic Techniques

Figure 7.11 Life cycle of malaria (A) and major pathological changes in organs (B).