When your PH slapped you on your back and said that
Africa becomes part of you, he meant it literally and
figuratively: Africa is not only in your heart - you could be
harbouring Africa’s common water-bourne parasite in your
The African bush is a place of beauty, tranquility
and magnificence but is also home to some of the worlds most deadly
diseases. One of them, lurking in streams, rivers and pools has a
dark side to it which could cause life-threatening complications. It
is a common, chronically debilitating and potentially lethal disease
affecting an estimated 200 million people, half of whom live in
Africa, with 600 million people being at risk.
is called Bilharzia or Schistosomiasis.
Schistosomiasis is most prevalent in sub-Saharan
Africa. This infection occurs throughout the tropics and sub
tropics. It is endemic to 74 countries. Bilharzia is a parasitic
infection caused by Schistosoma blood flukes.
Five species of Schistosoma infect humans:
Schistosoma mansoni and Schistosoma
intercalatum cause intestinal schistosomiasis
Schistosoma haematobium causes urinary
Schistosoma japonicum and Schistosoma
mekongi cause Asian intestinal schistosomiasis
Shistosoma flukes have a complex life cycles
involving specific freshwater snail species as intermediate hosts.
Bilharzia eggs are released into the environment from infected
individuals, hatching on contact with fresh water to release
infect fresh-water snails by penetrating the snail’s foot.
Infected snails release large numbers of small,
larvae called cercariae, capable of penetrating the unbroken
skin of humans. Even brief exposure to contaminated water can result
Cercariae emerge constantly from the snail host
in what is called a circadian rhythm. This is dependent on ambient
temperature and light. Cercariae are highly mobile and can
sink to maintain their position in the water or swim upwards if
stimulated by water turbulence, shadows and by some chemical
substances found on human skin.
Cercariae secrete enzymes that break down human
skin and make penetration possible. "Swimmers itch" occurs 1 day
after penetration. It is an itchy rash caused by the death of
cercariae upon skin penetration. The rash resolves spontaneously
within 10 days and is rare in endemic areas.
which enter the snail by penetrating the snail’s foot.
As the cercaria penetrates the skin it
transforms into a migrating schistosomulum stage. Here it
stays in the skin for a few days while locating a small vein to
transport it to the lungs of the human host. From here migration to
the liver takes place.
Juvenile worms from some species develop oral
suckers and the worms start feeding on red blood cells. Worms pair
S. mansoni and S. japonicum relocate
to the intestine or rectal veins
S. haematobium migrate from the liver to the
venous plexus of the bladder, ureters, and kidneys.
Worms reach maturity in eight weeks, at which time
they begin to produce eggs. Adult worms may produce 300 to 3000 eggs
per day. Many of the eggs pass through the intestinal or bladder
wall into the feaces or urine.
Some eggs released by the worm pairs become trapped
in the veins, or will be washed back into the liver, where they will
become lodged. Worm pairs can live in the body for an average of
four and a half years, but may persist up to 20 years.
Trapped eggs mature normally, and elicit a vigorous
immune response. The eggs themselves do not damage the body but due
to the immune response severe complications may arise.
Schistosomiasis is a chronic disease. Many
infections are asymptomatic, with mild anemia and malnutrition being
common in endemic areas. Katayama fever however is a rare but
potentially lethal illness occurring 1 to 3 months after the primary
Symptoms include, fever, headache, chills, sweating,
diarrhoea, cough, enlarged liver and glands and urticaria.
Clinical features of chronic Bilharzia include,
fatigue, abdominal pain, cough and diarrhoea. Various systems can be
Lung disease: Fatigue, dizzyness and
chestpain may develop due to embolizing eggs.
Liver disease: Abdominal distension,
enlarged liver, fluid accumulation in the abdomen, dilated
bloodvessels in the oesophagus.
Intestinal disease: Embolizing eggs may
cause chronic inflamation of the large bowel, bloody diarrhoea,
anemia and rectal prolapse
Central nervous system disease: Epilepsy,
paraplegia and bladder dysfunction.
Typhoid bacteria may colonize the adult worms
providing a source of recurrent typhoid attacks.
Diagnosis of Bilharzia is usually confirmed by
serologic studies (a blood test) or by finding Bilharzia eggs on
microscopic examination of stool or urine.
Bilharzia eggs can be found as soon as 6-8 weeks
after exposure, but are not always detectable. Blood test in the
exposed, asymptomatic traveler should ideally be performed 6-8
months following exposure.
Safe and effective drugs are available for the
treatment of Bilharzia and your health care worker or Family
physician will prescribe medication which will kill the adult
Avoid swimming or walking in freshwater in
countries in which schistosomiasis occurs.
Drink safe water.
You should either boil water for 1 minute or filter water before
drinking it. Boiling water for at least 1 minute will kill any
harmful parasites, bacteria, or viruses present. Iodine
treatment alone will not guarantee that water is safe and free
of all parasites.
Heat your bath water for 5 minutes at 150°F.
Water held in a storage tank for at least 48 hours should be
safe for showering.
Swart has been involved in Communicable disease control
since 2004 and is an authority on Malaria, tropical and
infectious diseases in Africa.
Vigorous towel drying after an accidental, very brief water
exposure may help to prevent the Schistosoma parasite from
penetrating the skin.
You should NOT rely on vigorous towel drying to prevent Bilharzia.