Parasite- A living organism that lives in or on another organism and obtains nourishment from that organism without being useful to it in any way.

-This host-parasite relationship is referred to as parasitism.

-Parasitism is an association between two organism one a parasite and the other the host.

Effects of parasites on livestock

(i) Cause Anaemia 

-Blood sucking parasites take large volumes of blood from the host animals leading to anaemia.

ii) Deprive the host of nutrients (food)

-Internal parasites compete for food with the host animals this result into loss of weight, emaciation and low production.

iii) Injury and damage to tissue and organs.

-Biting parasites break the skin of the animal exposing it to secondary infection.

-Some internal parasites such as round worms, live fluke etc damage organs and tissues.

-Tissue injury results into Hemorrhage.

Iv ) Disease transmission.

 -Some parasites act as vectors of some diseases 

-They spread disease from sick animals to healthy ones.

v) Cause irritation 

-Some external parasites irritate the animals through their biting effects.

-This causes the animal to rub itself against solid objects destroying skin, fur or wool.

vi) Obstruction to internal organs 

-Internal parasites may cause mechanical obstruction or blockage of the internal passages.

-This leads to mal-functioning of organs affected.

TYPES OF PARASITES

a. External parasites (ectoparasites)

b. Internal parasites (endoparasites)

a. External parasites

-Found on the outside of the host body.

-They may live on or under the skin.

-Most ectoparasites belong to the phylum arthopoda.

-T here are two main classes of these parasites.

i) Class insecta.

ii) Class arachnida 

CLASS INSECTA

These consist of tse tse flies, keds, mosquitoes, flies, lice and fleas.

a. Tsetse fly (Glossina spp)          

- This is a true insect undergoing complete metamorphosis i.e.

 -Tsetse flies give birth to larvae after the eggs hutch inside the body of the mother.

-Larva forms the pupa, which later changes into an adult.

-Tsetse flies bites mainly during the day.

Harmful effects

-They transmit Trypanosomiasis caused by a protozoan called trypanosome

-Sucks out blood from the animal causing anaemia.

-Cause damage on the skins and hides of animals making wounds which provide routes for secondary infection by pathogenic organisms.

Control

-Bush cleaning to destroy their breeding places.

-Spraying their breeding places with insecticides.

-Use of fly traps with impregnated nets.

-Use of sterilizing agents e.g. radio isotopes on male flies and then releasing them.

b.Keds (melophagus orinus)

-Are sometimes referred to as sheep ticks.

-They are hairy and wingless bloodsucking flies.

Harmful effects 

-Cause irritation in heavy infestation.

-Due to irritation, animal scratches itself thus damaging the wool.

-Retarded growth in lambs.

- Anaemia.

Control measures

-Shearing the infected sheep and hand spraying them with appropriate chemicals eg pyrethrum, malathium, dieldrin etc

-Routine sheep dipping.

c. Fleas 

They are wingless but have strong legs adapted for leaping over long distances. 

-They suck blood as their mouth parts are adapted for penetrating the host’s skin and sucking blood.

-They pass through the following stages during development, egg- larvae- pupa- adult.

  Harmful effects

-Cause irritation leading to scratching.

-Stick fast in poultry causing wounds on the comb and wattles.

-They cause anaemia.

Control measures

-Animals sleeping places should be kept clean.

-Dusting animal hooks with appropriate insecticides.

-Covering the stick fast fleas with petroleum to suffocate them.

d. lice 

They are small wingless insects and can be divided into two groups.

- Biting lice (mallophaga)

- Sucking lice (anoplura)

Biting lice

-They are found on both the birds and mammals.

-They have chewing mouthparts.

-They complete their lifecycle between three to four weeks.

Sucking lice 

-Have mouthparts reduced into styles for sucking blood.

-They are found only on mammals.

Harmful effects

-Cause irritation to the animal hence, the animal is seen to rub itself against fixed objects.

-Heavy infestations cause loss of health in animals.

 -Since animals under attack do not feed very well, there is emaciation.

-Loss of production in birds.

-Anaemia and restless especially in poultry.

Control measures

-Spraying or dusting animals with appropriate insecticides.

-Keeping animal houses clean.

-Perches in poultry houses should be applied with insecticides eg 40% nicotine sulphate solution.

-Dusting each bird with sodium fluoride for individual treatment.

CLASS ARACHNIDA

-This consists of the ticks, mites and spiders.

-Ticks and mites belong to the order Acarina.

-These do not undergo complete metamorphosis.

-They have two body parts i.e. cephalothorax and the abdomen.

-The adults have 4 pairs of legs.

(a) Ticks.

-Ticks rank as the single most important ectoparasites of livestock.

-They cause injury and spread very dangerous diseases.

-There are over 50 different species of ticks known.

Harmful effects

-Vectors of diseases e.g. ECF, Red water, Anaplasmosis.

-Suck blood-causing anaemia to the host.

-Cause wounds through their bites.

-Cause irritation to the animal.

-Their bites lower value of hides and skins.

-Some ticks produce toxins that may be harmful to the host.

THE LIFE CYCLE OF TICKS

-Ticks usually pass through four main stages in their cycle i.e.

       -Egg

       -Larva (six legs)

       -Nymph (Eight legs)

       -Adult (Eight legs)

-Different species of ticks need different number of hosts.

-There are therefore three categories of ticks i.e.

         -One host ticks.

         -Two host ticks.

         -Three host ticks.

ONE HOST TICKS

-These ticks require one host to complete their lifecycle.

-Eggs on the ground hatch into larvae.

-Larvae climb onto the host, suck blood, become engorged and moult into nymphs.

-Nymphs feed on the same host, become engorged and moult into adults.

-Adults feed on the same host, mate and the females drop off to the ground to lay eggs.

Examples of one-host ticks:

           -Blue tick ( Boophilus decoloratus)

           -The Texas Fever tick (Boophilus annalatus)

           -The Cattle tick (Boophilus microplus)

           -The Tropical Horse tick (Dermacentor nitens)

 TWO HOST TICKS

-This tick requires two hosts to complete their lifecycle.

-The larvae and nymphs pass through their stages on the first host.

-Eggs on the ground hatch into larvae, which climb on to the first host.

-A larva attaches themselves to the host, feed on blood, become engorged and moult into nymphs.

- Nymphs feed on the same host become engorged and then drop to the ground to moult in adults.

-Adults find a new host on which to feed.

-They feed on the second host and mate.

-Females drop off to the ground to lay eggs.

Examples of two host ticks.

          -Red legged tick (Rhipicephalus evertsi)

          -The Brown tick (Amblyomma maculatum)

          -The African Bont-legged tick (Hyalomma truncatum)

          -Large Bont-legged tick (Hyalomma rufipes)

THREE HOST TICKS

-These ticks require three different hosts to enable them to complete their lifecycle.

-Eggs hatch on the ground into larvae.

-Larvae attaches itself to the first host, feed on blood, become engorged and drop off to the ground and moults into nymphs.

-The nymphs look for a second host, feed on blood, become engorged and drop off to the ground and moult into adults.

-Adults seek for the third host, climb, feed become engorged and mate.

-Females drop off to the ground to lay eggs.

Lifecycle of a three host tick.

Examples:-

           -Brown ear tick (Rhipicephalus appendiculants)

           -East African Bont tick (Amblyomma variegatum)

           -Bont tick (Amblyomma herbraem)

           -Gulf Coast tick (Amblyomma maculatum)

           -Yellow Dog tick (Haemaphysalis leachii)

           -Fowl tick (Heamaphysalis hoodi)

           -Brown Dog Tick (Rhipicephalus sanguineous)

TICK CONTROL MEASURES

i) Natural/Biological method.

ii) Mechanical method.

iii) Chemical method.

1. Natural/ Biological method.

-This is the use of the tick’s natural enemies which predate on the ticks. E.g. using predators such as birds to control ticks.

N/B Only a small number of ticks is controlled using this method.

2. Mechanical method

i) Burning the infected pastures.

-Burning destroys eggs, larvae, nymphs and adults.

ii) Interfering with the ticks environment 

  This is achieved by:-

-Ploughing pasture land .the eggs are exposed to the sun heat or are deeply buried.

iii) By top dressing pasture using lime or dressing using acaricides.

iv) Fencing off the pasture and farm.

v) Hand picking the ticks (deticking)

vi) Starving the ticks to death

     -This is achieved by practicing rotational grazing.

     -It interrupts the lifecycle of the ticks.

3. Chemical control method.

This is done by application of acaricide.

Properties of an effective acaricide

-Has the ability to kill ticks.

-Be harmless to both human and livestock.

-Be stable.

-Should remain effective after having been fouled with dung, mud or hair.

Methods of acaricide application

-Spraying regularly with the acaricide.

-Dipping animals in plugs dips containing the acaricide.

-Hand dressing using pyegrease. 

ENDOPARASITES (INTERNAL PARASITES)

These are parasites which live within the body of the host animal e.g. tapeworms, Round worms, Fluke etc

Categories of Endoparasites

-Endoparasites are generally called helminthes 

-They fall under 2 phyla

i)Platyhelminthes (Flat worms)

-class-trematoda (flukes)

-Cestoda (tapeworms)

  ii) Nemathelminthes (nematoda)- Round worms.

P LATYHELMINTHES

-Are flatworms.

 -Body is symmetrical

-Are hermaphroditic.

a) Tape worm ( Taenia spp) -cestodes

-Have two main parts ie

-Has a head (Scolex) and a chain of segments called the strobila 

-Each segment is called a proglottis.

-Scolex has suckers or hooks or both.

Animals affected   –   pigs

- Cattle

- Sheep.

- Goats.

- Donkey.

Symptoms of attack

-General emaciation 

-Rough or staring coat.

-Scouring and sometimes constipation due to digestive disturbance.

- Pot-bellies especially in calves.

-Oedematous swelling under the jaw.

-Obstruction/blockage of the intestines when tape worms are present in large nubers.

- Ploglottides present in faeces.

-Anaemia.

-Excessive appetite.

N.B. Lifecycle of tape worm 

-Tape worms attack farm animals as intermediate hosts and man as final host.

-There are two common species of tape worm 

i) Beef tape worm (Taenia saginata) 

ii) Pork tape worm ( Taenia solium)

-Affected human beings drop Ploglottides full of eggs with faeces.

-Eggs are picked by the right intermediate host either cattle or pigs while feeding.

-After ingestion by the host (intermediate), Eggs hutch in the intestines into embryos.

-Embryos penetrate the intestinal wall and enter the blood system.

-They first move to the liver and then to all body muscles of the animal where they become cysts.

-Under cooked beef or pork from infected animals if eaten by man causes an infection.

-In the human intestine cysts wall dissolve and the parasites attack themselves to the wall of the intestine.

-Here they develop into adult tapeworms.

-These are passed out again in faeces.

Control measures and treatment 

-Use of prophylactic drugs e.g. antihelminthes (dewormers) to kill parasites in animals.

-Keep animal houses clean and disinfected.

-Practice rotational grazing to starve the larvae (cysts) to death.

-Keep the feeding and watering equipment clean.

-Use of latrines by farm workers ie proper disposal of human faeces.

-Proper meet inspection.

-Proper cooking of meat.

b) Liver fluke (Fascial spp (Trematoda)

There are many species of flukes.

-Two are the most common ones ie

i) Fasciola heptica (sheep)

ii) Fasciola gigantica (cattle)

-Heavy infestation of flukes cause a condition called Fascioliasis.

Symptoms

-Emaciation 

-Indigestion in the animal.

-Pot bellied condition.

-Damage to liver tissue causing haemorrhage due to movement of flukes in the liver.

-Anaemia due to sucking of blood.

-Animals are dull and depressed.

-Swollen and painful abdomen.

-Recumbence precedes death.

N.B. Fasciola has the following characteristics 

-Gray or gray-pink in colour 

-Flattened like leaf.

-Have a conical projection at the anterior end.

-Have a tapering body ending. 

Lifecycle:

-Liver fluke use the fresh water snail as their intermediate host.

- They have sheep or cattle as their final host.

-Adult flukes are found in the bile duct of the liver of the host animal.

-Here they produce eggs which are passed into the alimentary canal through the bile duct.

-Eggs are passed out through dung.

-A fluke produces about 300-3500 eggs per day.

-I the eggs falls into stagnant water that is warm, they hatch into a ciliated embryos called miracidia (miracidium)

-On coming into contact with the intermediate host snail (Limnea spp). It penetrates the snail tissue.

-Once inside the snail tissues, miracidium process masses of cells called sporocysts

-Sporocysts change into Redia.

-Redia produces cercaria more out of snail

-Cercaria change into metacercaria which is the infective stage of the fluke

-The definite/ final host through grazing or drinking infected water takes Metacercaria.

N.B. Metacercaria can survive in wet grass and in shady places or when withstand harsh conditions for a year.

-Once swallowed by the host, cercaria penetrates walls of the intestine and hatch into adults.

-Adults migrate to the liver where they grow, mature, mate and produce eggs.

-The cycle starts all over again.

Control measures 

1. Controlling the fresh water snail (intermediate host) though 

a) Physically killing them.

b) Chemically by use of CuSo4 Sodium pentachlorophenate etc which is added to stagnant water to kill the snails.

c) Draining swampy areas/leveling any depression that may hold water in the pastures. 

2. Burning of the pastures during the dry seasons to kill cercaria

3. Not grazing animals near marshy or waterlogged areas.

4. Routine drenching using antihelminthes e.g. NaSo4, hexachloroethane drugs.

ROUNDWORMS (NEMATODES)

(Ascaris spp)

There are three common species of round worms 

i) Ascaris lumbricoides Cattle and sheep.

ii) A. suum Pigs.

iii) A. galli poultry.

-Heavy infestation of these worms cause a condition called ascaridiosis 

Symptoms of Attack.

-Anorexia (Loss of appetite in heavy infestation)

-Staring coat (stiff and dry)

-Dehydration and pale mucosa 

-Eggs and adults present in faeces.

-Emaciation 

-Diarrhoea.

-Anaemia.

-Potbellies especially in young animals.

LIFECYCLE OF A ROUNDWORM

-The common roundworm Ascaris lumbricoides does not have intermediate hosts.

-Eggs are laid in the alimentary canal of the host animal.

-Eggs are passed out of the host with faeces.

-Under favorable environmental conditions, eggs hatch into larvae which climb