EAH NS 
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Parasitic 
Nematodes 
Parasites on insects 
A number of insects have nematode 
parasites. The nematodes usually 
live only part of their life cycle in 
the host insect. In some nematodes, 
it is the young worm that is the 
parasite; in others, it is the adult 
Others live for a time in different 
hosts. 
Some nematodes live in both 
animals and plants. A nematode 
may feed inside a plant, then enter 
an insect when the insect eats the 
plant. The nematode lays its eggs 
in the insect, which takes the young 
worms to another plant. Another 
type of nematode develops inside 
an insect, then enters a plant to 
mate and rcpnxiuce 
Nematodes that live inside inserts 
usually weaken or even kill the 
insect host People are now using 
these worms to control insect pests, 
instead of poisonous pesticides. A 
farmer buys a million nematodes in 
a package, and spreads them over 
his crops. This is a biological way 
of controlling insects. 
Parasites in people 
Some large nematodes are parasites 
in people. Plnworm.s (also called 
threadworms), are small, thin and 
white in colour, anti live in the 
intestines. Female pin worms 
deposit their young on the host s 
bottom or bedclothes. Pin worm 
infection is very common in small 
children. It does little harm, and is 
treated by medicines and washing 
hands Whipworms .ire about -i cm 
long, part of the body short and 
thick and part long and thin. They 
live in the intestines, sucking blood 
from the intestine wall. Whipworm 
infection usually mild, but can 
lead to bleeding and anaemia. Large 
Asians roundworms arc 15 to 40 
cm long, whitish or pinkish in 
colour. They live in the intestines 
and feed on the food we eat. Most 
infections with roundworms arc 
not serious, but in a few cases there 
arc m> many worms that they block 
the intestine or the nose The eggs 
nf roundworms and whipworms 
are passed with the faeces to the 
ground, where they may get onto 
vegetables or m the water supply. 
Using latrines, washing hands, and 
washing fruits and vegetables that 
are eaten raw controls the spread 
of the worms. There are medicines 
to treat infection. 
Hookworms are about one cm 
long and reddish pink in colour. A 
hookworm uses the hooks in its 
mouth to attach to a person's 
intestine, and feeds on the blood of 
its host. The worms mate in the 
host's intestine, and the eggs pass 
out through the faeces. The young 
hookworms are free-living in the 
soil, they need warm, moist 
conditions to survive. If a person 
