Table of Contents
What is a parasite? A Parasite is an organism which obtains its livelihood from another organism (host) which suffers damage. Parasitism is the association between a parasite and a host.
The effects of parasite on the host animal are:
- Depriving the host of its food.
- Sucking blood.
- Damaging the organs of the host.
- Cause irritation on the skin of the host.
- Destruction of hides and skins.
- Transmission of diseases.
- Cause obstruction in body passages.
General Symptoms of Parasites infestation:
- Potbellied condition.
- Swellings in the jaw or other areas.
- Rough hair or rough coat.
- Presence of worm segments and blood stains in the defecation.
Types of Parasites
There are two types of parasites: (1) External (ecto-parasites) (2) Internal(endo-parasites)
External parasites are;
- tsetse flies,
Life Cycle of ticks
- Eggs are laid in cracks on the ground.
- They hatch in 4-6 weeks into larvae which climb on the grass waiting for a passing animal.
- This requires one host to complete its life cycle.
- Example: blue tick (Boophilus decoloratus).
- Preferred sites: face, neck, dewlap and side of the body.
- Disease transmitted: Redwater and anaplasmosis.
- This requires two different hosts to complete its life cycle.
- Example: The red legged tick (Rhipicephalus everts)
- Preferred sites: Ears, anus, udder and the tail.
- Disease transmitted: Redwater and east coast fever.
- Example: Bont legged tick (amblyomma spp.)
- Preferred sites: Udder, scrotum and tail switch.
- Disease transmitted: Sweating sickness.
- This requires three hosts to complete its life cycle.
- Example: The brown ear tick (Rhipicephalus appendiculatus)
- Preferred sites: Ears, tail switch and around the eyes.
- Disease transmitted: East coast fever and redwater.
- Bont tick transmit heartwater (amblyomma spp.)
Control of Ticks
- Dipping/spraying/hand dressing with acaricides.
- Rotational grazing.
- Ploughing the land to break the life cycle.
- Hand picking and killing.
- Fencing of the grazing ﬁelds to keep off other animals including wild game.
- Burning of grass to kill them in various stages.
Endo-parasites ( internal Parasites)
Endoparasites are helminths.
They can be divided into:
Platyhelminthes/flatworms which include;
– Trematodes (flukes)
– Cestodes (tapeworms).
– Nemato-helminthes/nematodes. E.g Roundworms.
General Symptoms of Helminthiasis
- Diarrhoea which foul the anal and tail region.
- Big stomach (pot bellied condition).
- Presence of worm segments in faeces.
Trematodes (Liver Fluke)
There are two species of flukes:
- Fasciola gigantica
- Fasciola hepatica.
Fasciola hepatica is more common.
It is commonly found in the liver and bile duct of cattle, sheep and goats.
Liver ﬂuke is a problem in marshy and low lying wet areas.
Life Cycle of the Liver Fluke
- Adult fluke in the liver of the primary host lays eggs.
- Eggs pass through the bile duct into the small intestines and are passed out in faeces onto the pasture.
- Under moist conditions, they hatch into a miracidium larva which swims about in search of a secondary host (fresh water snails).
- In the snail, it develops through sporocyst, redia and cercaria.
- When it leaves the snail, the cercaria gets encysted on vegetation and becomes metacercaria.
- This is swallowed by the primary host with grass.
- The young fluke migrates into the liver through blood vessels when it matures.
Control of Liver Fluke
- Keep livestock off marshy areas near the rivers/streams/lakes and dams.
- Drench af-fected animals.
- Drainage of swampy areas.
- Eradicate the intermediate host by use of molluscicides.
- Provide water to livestock in elevated troughs.
There are many species of tapeworms
- The adults live in the small intestines of man (the primary host).
- The intermediate host of Taenia solium is pig .
- The intermediate host of Taenia saginata is cattle.
Life Cycle of Tapeworm
- Adult tapeworms live in man’s intestines where it lays eggs.
- Eggs are passed out with faeces,
- Then they develop an outer covering known as onchosphere.
- The eggs are swallowed by intermediate host.
- The outer covering is digested and the young worm emerges.
- This bores into the blood vessels and is carried to speciﬁc muscles such as the tongue, heart, thigh muscles.
- It develops into an encysted form called bladder-worm.
- When the animal is killed and meat is eaten raw or in an inadequately cooked form, man gets infected by the bladder-worm.
- In man, the bladder-worm evaginates and attaches itself onto the intestinal wall where it develops into an adult.
Control of Tapeworms
- Meat should be well cooked before eating.
- Use of drugs in primary host.
- Meat inspection by meat inspectors] veterinary officers.
- Use of pit latrines by man.
Common ones are:
- Ascaris suum (pig roundworms),
- Ascaris lumbricoides found in man and sheep
- Haemonchus contortus found in sheep, cattle and goats.
- Roundworms are common in warm areas especially in areas where the standards of hygiene and sanitation are low.
Nature of Damage
- Damage is done to the liver and lung tissues as they migrate in the body.
- Suck out blood.
- Deprive the host of food.
Control of Roundworms
- Use of drugs.
- Rotational grazing.
- Use of proper stocking rates to avoid overgrazing.
Practicing high standards of cleanliness and hygiene such as use of latrines
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