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146 Parasitic Infestations of Surgical Importance in Children

In S. haematobium infection, the lesions are most marked in the • Serological test: Several serological tests may be done. Some of
bladder and lower part of the ureters. The bladder often contains focal these may be used for screening of large populations.
polypoid mucosal lesions or plaques of large masses of eggs. Eggs of S. • Additional tests: Tests such as sigmoidoscopy, liver biopsy, and
haematobium in the bladder and ureteral walls appear to have a tendency to barium swallow/oesophagogastroscopy may be indicated in intesti-
calcify, giving a “sand” appearance to these focal lesions and making them nal schistosomiasis.
visible radiologically. Late effects are fibrous contraction of the bladder.
Ureteral polyps, strictures, and obstruction may lead to pyelonephritis Strategies for Control
and hydronephrosis. Cystitis with squamous metaplasia and ulceration The four main foci for control of schistosomiasis are: (1) large-scale
leading to haematuria are common findings throughout the course of S. population-based chemotherapy, (2) vaccines, (3) molluscicides, and
haematobium infection. Carcinomas of the bladder, of which half are (4) environmental interventions. Various combinations of these strate-
squamous cell and almost half transitional with a few adenocarcinomas, gies have resulted in remarkable progress toward reducing schistosomi-
are late complications. asis. Sub-Saharan Africa, however, has had very little schistosomiasis
The changes are more marked in S. japonicum infection compared control activity in the recent past. WHO is now rolling out initiatives to
to S. mansoni because a lot more ova are produced. The mucosa of address this deficit. Current WHO initiatives target school-age children,
the large bowel is hyperaemic and studded with pseudotubercles and with a goal of treating 75% of children at risk of schistosomiasis-related
shallow ulcers. Sessile or pedunculated polyps from coalescence of morbidity by 2010.
granulomata and epithelial hyperplasia are often present. Fibrosis leads Medical Treatment
to rigidity and consequent narrowing of the bowel.
The liver is also affected, especially in S. japonicum. It can be small, • Praziquantel is effective against all three species of schistomiasis.
enlarged, or normal in size and nodular. The initial granulomata result It may be given as a single oral dose of 50 mg/kg or 20 mg/kg three
times at 4-hour intervals. Side effects are transient nausea, epigas-
in fibrosis around the terminals of the portal vein with ova embedded tric pain, pruritus or skin eruptions, headache, and dizziness. The
in them. These changes lead to portal hypertension with splenomegaly, cure rate is 80%.
ascites, and oesophageal varices.
Clinical Manifestation • Niridazole (Ambilhar) is the drug of first choice for all the species
Symptoms start after age 5 years but are marked in the second decade of schistomiasis. The dose is 25 mg/kg (maximum 1.5 g) orally in
of life, and without treatment are severe in the third decade. Soon after two divided doses for 7–10 days. Side effects include confusion,
depression, mania, epilepsy, slurred speech, and dark brown urine.
penetration of the cercariae, there is a pricking sensation followed by
papular dermatitis at the sites of penetration. This lasts for 2–3 days. • Metrifonate is effective against S. haematobrium with a cure rate
About 4 weeks later, as a result of allergy to the developing flukes, the of 50–90%. It is given orally in a dose of 10 mg/kg repeated fort-
patient experiences intermittent fever, malaise, urticaria, and cough. nightly for three doses.
These symptoms last about 2–8 weeks. Like the initial symptoms, these • Oxamniquine (Mansil , Vansil ) is effective against S. mansoni as a
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are mild, transient, or absent in infection by S. haematobium, especially single oral dose of 30 mg/kg, but a second dose may be repeated in
in patients resident in endemic areas. In S. mansoni and S. japonicum a few weeks. Fever, headache, and dizziness may occur.
infections, an allergic reaction to schistosomules in the liver results in
pyrexia; malaise; painful, tender, and enlarged liver; splenomegaly; and Surgical Treatment
at times jaundice and urticaria. From 6 to 24 months after the initial Surgical treatment may be necessary in later life. It is indicated for
infection, symptoms develop due to the excretion of ova and the reac- fibrous contracture or carcinoma of the bladder, stenosis of the ureter,
tion to dead ova, the severity depending on the intensity of infection hydronephrosis, portal hypertension and stenosis of the bowel.
and the number of eggs produced. Myiasis
Intermittent terminal haematuria after strenuous exercise is the main
symptom of urinary schistosomiasis (S. haematobium infection). It occurs Myiasis is a condition in which fly larvae (maggots) invade living tis-
in about 50% of patients and is initially caused by damage of the mucosa sue. They can be cutaneous, arterial, intestinal, or urinary in normal tis-
by escaping ova and later by granulomatous ulcers or bilharzioma. Other sue or in preexisting wounds. Their importance lies in the fact that they
symptoms are frequency of urination and burning sensation. are easily misdiagnosed, can cause mechanical damage, and cutaneous
myiasis may require surgical removal of burrowed larvae.
Investigations
The cornerstone of diagnosis of schistosomiasis is the detection of Demographics
Myiasis is a parasitic infestation caused by the larvae of several fly spe-
schistosome eggs in urine or faeces observed in saline. The characteris-
cies, such as Cordylobia anthropophagi (Tumbu fly), which is endemic
tics of the respective ova aid their identification and diagnosis.
in Tropical Africa and is known to have been widely distributed in the
• X-ray of the pelvis: There may be calcification of the bladder wall
West African subregion for more than 130 years. Other fly species that
and the lower end of the ureters in advanced cases.
produce larvae that cause myiasis are Cordylobia rhodaini (Lund fly),
• Abdomino-pelvic ultrasound scan: Ultrasound assessment of the found in the rainforest areas of Tropical Africa, and Dermatobia homonis
changes in the urinary system are also promising. Ultrasound is still (human botfly), which is endemic in Central and South America.
useful for early identification of periportal fibrosis and for assess- Aetiology/Pathophysiology
ment of hepatosplenomegaly.
Myiasis could result from a breach in healthy skin by the fly larvae
• Cystoscopy: When examination of the urine and faeces is negative themselves or through abrasions and wounds in which the respective
or there are marked bladder symptoms, cystoscopy is performed. flies deposit their eggs or larvae. The larvae can burrow through healthy
Tubercles, sandy patches, granulomatous ulcers, or bilharzioma may tissue by using their cuticular spines aided by proteolytic enzymes.
be evident; biopsy of the lesion provides histological confirmation. The larvae arise from eggs deposited by the fly species on soil
polluted with animal excrement, or clothing saturated with perspiration,
• Rectal biopsy: Ova are seen in snips of rectal mucosa.
or soiled diapers. After hatching, the larvae can stay alive for 7–20 days
• Excretion urography: Origraphy may demonstrate hydronephrosis, while attached to contaminated articles and clothing or the soil. They
hydroureter, or multiple filling defects in the bladder due to bilharzioma. are activated by the warm body of the host and penetrate the skin and