PATHOLOGICAL EFFECT OF THE PARASITE UPON THE HOSTrate into the dermal layers. This causes a certain amount of itching (‘swimmers itch’) and
may last for 2–3 days.
Once the juvenile (the schistosomule) is established in the dermal tissue it then begins
a slow migratory process. The first destination is the lung and symptoms associated with
this stage are eosinophilia, fever, diarrhoea and coughing. At this stage the lymph nodes
and spleen increase in size. The overall symptom is referred to as Katayama fever and is
normally not fatal. The infected individual recovers, but is often left with a chronic
infection. Once the worms reach maturity in the mesenteric blood vessels egg produc-
tion commences.
The egg granulomas that form within the liver lead to portal fibrosis and an increase
in the size of the liver and there is portal hypertension. Eggs can be deposited in the lungs
and the granulomas can lead to obstructive disease of the lungs. In rare instances eggs
are deposited in the spinal cord and brain where the inflammatory response leads to
necrosis of a certain amount of neural tissue.
n 7.5.6SCHISTOSOMA HAEMATOBIUM
S. haematobiumadult worms live in the blood vessels associated with the urinary tract
and bladder. Unlike S. mansoni, S. japonicumand S. intercalatumthe pathology due to this
infection (S. haematobium) is mainly related to the urino-genital tract.
The eggs pass out of the host via the urine. In order to enter the lumen of the blad-
der the eggs have to penetrate through the walls (the endothelial cell layer) of the blood
vessels. This process causes local haemorrhage and blood loss via the urine. Many of
the eggs deposited in the urino-genital tract become embedded in the lining walls and
granulomatous tissue forms round the eggs. As the disease progresses there is calcium
deposition, detectable as radiopaque patches in the urinary tract.
Continuous ‘trickle’ infections lead to an inflammation of the bladder and even to the
formation of malignant squamous epithelial cells. The inflammatory changes in the
ureter followed by fibrosis often lead to obstruction and possible kidney damage.
Immune complex deposits have been detected on the kidney glomerular membranes.
n 7.5.7FASCIOLA HEPATICAAND FASCIOLIASIS
An adult Fasciola hepaticahas a flat leaf-like shape (Fig. 3.7) with dimensions of about 20–
30 ×8–13 mm. Fasciolalike most of the trematodes is an hermaphrodite. The distribu-
tion of the male and female genitalia follows the typical trematode pattern. The outer
covering is a tegument and the anterior portion is covered in spines. The anterior end
has a cone with an anterior sucker surrounding the mouth. There is a second sucker, the
n BOX 7.2
A post-mortem examination of Zimbabwean women with S. haematobiumfound that
urinary schistosomiasis was the cause of the following pathology: genital lesions induced
by sequestered eggs and lesions in the vagina, fallopian tubes, ovaries, corpus uteri, and
parametrium.
Lesions of the upper genital tract may cause retarded intra-uterine foetal growth and
pre-term deliveries. The clinical manifestations a mainly dyspareuria, dysmenorrhoea, bloody
vaginal discharge, primary and secondary infertility and ectopic pregnancy. A relationship
between genital schistosomaisis and cervical cancer has been suggested (Richter J. et al.
1995).