Worms and Human Disease

factors, such as the presence of nitrosamines
in the urine, are probably involved (Mostafa
et al., 1995). Squamous carcinoma is more
common than transitional carcinoma (Fig.
13). It has been estimated that schistosomiasis
is responsible for about 16% of cases of
bladder cancer in Egypt. In the Nile Delta
region, men do most of the agricultural
work and thus become infected, resulting in
a 12:1 male-to-female bladder cancer ratio.
Pulmonary arteritis progressing to irreversible
and lethal cor pulmonale because of
capillary damage by eggs sometimes occurs
when eggs are swept back into the lungs.
The presence of adult worms in the lungs
following drug treatment is also a possible
cause of pulmonary damage. In women,
eggs may cause lesions in the ovaries,
Fallopian tubes and uterus or in the lower
The Trematodes 19
Fig. 12. Intravenous pyelogram of a woman infected with S. haematobium showing bilateral hydronephrosis
with deformity of both ureters.
parts of the genital tract, including the
cervix, vagina and vulva, and about 6–27%
of such cases result in sterility.
S. japonicum, S. mekongi, S. mansoni
and S. intercalatum
Invasive phase. As for S. haematobium.
Acute phase. Allergic manifestations, such
as pyrexia, headache, oedema, cough,
dysenteric symptoms, pruritus and
urticaria, occur 3–8 weeks after infection
with S. japonicum. This is known as the
Katayama syndrome and may be accompanied
by tenderness in the liver region, mild
abdominal pain, lymphadenopathy and
splenomegaly, with an accompanying