LIVESTOCK HEALTH II ( PARASITES )

Introduction

• 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:

• Ema
• Pot bellied condition.
• Swellings in the jaw or other areas.
• Rough hair or rough coat.
• Anaemia.
• Diarrhoea.
• Presence of worm segments and blood stains in the defecat

Types of Parasites

There are two types of parasites:

• External (ecto-parasites)
• Internal (endo-parasites)

External parasites are;

• ticks,
• tsetse flies,
• mites,
• lice,
• fleas
• keds

Life Cycle of ticks

• Eggs are laid in cracks on the group
• They hatch in 4-6 weeks into larvae which climb on the grass waiting for a passing animal.

 One–Host Tick

• 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 anapl

Two-Host Tick

• This requires two different hosts to complete its life cycl
• 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 sickn

 Three-Host Tick

• This requires three hosts to complete its life cycl
• 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.
• Dullness.
• Anaemia.
• Big stomach (pot bellied condition).
• Presence of worm segments in faeces.
• Coughing.

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 metacercari

• 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 affected animals.
• Drainage of swampy areas.
• Eradicate the intermediate host by use of molluscicides.
• Provide water to livestock in elevated troughs.

Tapeworms

• There are many species of tapeworms

Eexample;

• Taenia solium
• Taenia saginata.

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. 

Nematodes (Roundworms)

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.