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Tremacoda Flukes 
Plukw .ire parasite*. They live on 
nr in an animal, called che hose, and 
feed on blood or animal (issues. 
They have suckers co hang onto their 
host. Flukes are not the same as 
leeches, however. Leeches arc 
bigger, easy to sec with the naked 
eye; most flukes arc very small. 
Schistosoma flukes that cause 
bilbarxia (schistosomiasis) live 
msidr people Adult flukes cling to 
the walls of body organs and suck 
blood After mating, females lay 
eggs, which enter the person’s 
bladder or intestine (depending on 
the species of Schistosoma). The 
eggs leave the human body through 
the urine or faeces. 
When Schistosoma eggs arc dropped 
in water, they hatch into tiny la rvac 
called mirac idia. The miracidia seek 
out and enter a freshwater snail. The 
host snails live in standing water, 
such as dams, irrigation ditches, 
rice paddies and slow-moving 
rivers, usually below I .NIK) 
metres altitude Schistosoma 
flukes cannot live in land snails 
or slugs. 
Inside the snail, miracidia change 
into sporocysts. which have the 
ability to reproduce ascxually. 
The sporocysts produce thousands 
of larvae called cercariu. The 
ccrcaria leave the snail and swim 
in watet. They must find a new host 
within a few days or they will die. 
I his time, the host will be a human 
being 
Schistosoma cercaria arc able to go 
through human skin. Inside the 
person, they find their way to the 
blood system The young flukes 
may swim around a person's blood 
system for several years. 
riir pretence of blood flukes feeding 
inside the body is the disease 
bilharaia or schistosomiasis. Ir 
alfcers millions of people mi tropical 
arras. There is treatment for the 
disease, but prevention is bertcr 
than cure" 
The lust prevention is to use latrines 
- it is people who put bilhar/ia in 
water, not snails' bridges made of 
logs or "stepping stones' help 
people to cross standing warcr. It 
is best 10 (liter or boil water from a 
dam or slow-moving stream before 
drinking it 
