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Parasitic Infestations of Surgical Importance in Children 145

• Secondary bacterial superinfection, septicaemia, tetanus, severe arthri- are more often and more heavily infected than adults because of their
tis, and ankylosis may be additional clinical manifestations of GWD. play habits and hygiene. Also, both the prevalence and intensity of
infection have been found to be higher among males than females
Treatment
in many surveys. Like other parasitic diseases, poverty, ignorance,
The main treatment is extraction of the worm by cautious wind-
poor living conditions, inadequate sanitation, inadequate or total lack
ing around a matchstick and gentle traction applied daily until it is
of public health facilities, and lack of safe water supplies, as well as
removed. Wet compresses are applied to the ulcer daily until the dis-
deplorable personal and environmental hygiene characteristic of many
charge from the worm ceases.
developing Third World countries, are identified as important factors
Application of a topical antibiotic to the lesion prevents secondary contributing to the increasing transmission of schistosomiasis.
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bacterial infection and complications. The use of niridazole (Ambilhar )
(25 mg/kg in two divided doses given orally daily for 10 days), Life Cycle of the Parasite
thiabendazole (50 mg/kg daily for three days), or metronidazole (10 Of the different Schistosoma species that can infect humans, S. haema-
mg/kg per dose at 8-hour doses daily for 10–20 days), can help to lessen tobium, S. mansoni, and S. japonicum are the most important because
the intense tissue reaction, make extraction easier, and relieve the pain. they cause the vast majority of infections.
The worm may be removed intact before it breaks through the Man is the definitive host of these parasites; S. japonicum, however,
skin. Preoperatively, an antihistamine is given to prevent untoward can live in other animals such as dogs, cats, cows, pigs, and rats. The
allergic reaction. intermediate host is the snail—bulinus for S. haematobium, biomphalaria
and australorbis for S. mansoni, and oncomelania for S. japonicum.
Prevention
Measures are directed to three different areas: For transmission to occur, there must be humans (or in the case of
S. japonicum, animals) and snails living in close proximity and moving
1. Providing a safe drinking water supply through the same aqueous environments. Additionally, infected humans
• Providing piped water or drilled boreholes equipped with hand must excrete their faeces or urine into or nearby the snail-infested
pumps are appropriate, although they are expensive to maintain. water. When these conditions necessary to maintain the multistage life
cycle are met, humans become infected when they come into contact
• Improving the existing water system, such as protecting open wells
or using concrete or stone masonry parapets, is a sustainable inter- with the cercariae during swimming, bathing, washing, or wading in
vention. Small dams and ponds can be equipped with infiltration infested water, or ingesting water from snail-infested sources. The
cercariae penetrate the skin or mucous membrane to enter the body.
galleries to prevent people from wading into the water and therefore
preventing infestation of the water sources by the parasite larvae. They travel via the bloodstream, lung, and liver, and finally lodge
within 30 days in the venules of the portal system, where they mature
2. Filtering drinking water into adult worms. The adult males then move against the flow of blood,
• When safe drinking water is not available, transmission can be carrying the females in their gynaecophoric canal to the vesicular veins
interrupted by using filters made from fine mesh (100 microns). (in case of S. haematobium) or the mesenteric veins (in the case of S.
mansoni and S. japonicum) in order to produce eggs.
• Ordinary cloth filters can be used at the household level, with the Fertilised eggs or ova are released by the female parasites within the
water boiled and aerated to restore taste.
vasculature, then they cross the endothelium and basement membrane
• A monofilament nylon cloth filter is more robust and has the abil- of the vein by means of a lytic substance they secrete, and enter the
ity to remove the vector of the disease from drinking water. basement membrane and epithelium of the bladder or intestines,
depending on the species involved. As a result, many eggs enter the
3. Chemically treating pond water
lumen and are released from the body in urine or in the stool, but many
• The application of temephos (Abate ) to surface water sources, are held up in the wall and die after 3 weeks; it is these dead ova that
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mainly ponds, is an effective measure to prevent transmission by provoke the various pathological reactions. Those that are released
killing the vector. Treatment of the drinking water sources should from the body perish in 8 hours unless they come into contact with fresh
be conducted monthly throughout the transmission season.
water. The next phase of the flukes’ life cycle takes place when humans
Schistosomiasis urinate or defaecate into or near fresh water.
Schistosomiasis is a group of diseases caused by trematodes (blood The eggs liberate their larvae or miracidia, which must enter the
flukes) of the genus Schistosoma, the important species being S. hae- liver of the appropriate snail within 48 hours or die. In the snail, the
matobium, S. mansoni, and S. japonicum. It is also named bilharziasis miracidium forms a sporocyst that divides several times, forming
daughter sporocysts containing cercariae. The sporocyst matures in 9
in honour of Theodor Bilharz, a young German pathologist who dis- weeks and ruptures, releasing many cercariae excreted by the snails into
covered the aetiological agent for S. haematobium in Egypt in 1851. the water. The tailed cercariae swim in the water until they come into
After malaria, schistosomiasis is the second most prevalent and most contact with a human and the cycle is restarted. They die within 48 to
important parasitic disease in the world, with profound economic and 72 hours if no such contact is made. The life cycle takes 12–14 weeks.
public health consequences.
Demographics Pathology
Schistosomiasis remains a global health problem in the 21st century The pathological changes depend on the intensity and frequency of
infection and the duration of exposure. The earliest reaction is papular
with an estimated 200 million people in 74 countries infected, of whom dermatitis at the sites of entry of the cercariae, followed by pulmonary
85% are living in sub-Saharan Africa; the remainder live in South and inflammatory reaction as the cercariae pass through the lungs. These
Central America, the Caribbean, and the Far and Middle East. Travelers changes may not be clinically apparent, especially in people normally
to endemic areas (particularly Africa) are at high risk of infection, and resident in the endemic areas.
with increasing immigration globally, the chances of importing this In the established infection, the basic pathological reaction is
disease to nonendemic areas are greatly increased. provoked by dead ova and consists of the formation of foreign body
The occurrence of species of schistosomiasis are highly variable granulomata and fibrosis. The granuloma is made up of an ovum
from one country to another. S. mansoni is the most widespread, with surrounded by epithelioid cells, plasma cells, lymphocytes, eosinophils,
S. haematobium concentrated in Africa and the Middle East, and S. giant cells, and fibroblasts.
japonicum primarily found in Asia. On the whole, school-aged children