LIVESTOCK HEALTH II (PARASITES)

LIVESTOCK HEALTH II (PARASITES).

LIVESTOCK HEALTH II (PARASITES),Host-parasite Relationship.

Parasitism. Association between two organisms inn which one benefits by nourishing itself at the expense of the host.

Effects of parasites on the host.

1. Cause anaemia. Blood sucking parasites take large volumes of blood from the host leading to anaemia and eventually death.
2. Deprive the host animal of its food. Internal parasites compete for food with the host.  This lead to loss of weight, emaciation and low production.
3. Injury and damage to tissues and organs. Biting parasites damage the skin exposing it to secondary infection.  Internal parasites damage organs and tissues as they migrate from place to place in the body of the host.
4. Disease transmission. Some parasites acts as vectors of livestock diseases.
5. Cause irritation. Some external parasites irritate the animals through their biting effects.  This causes the animal to rub itself destroying the skin, fur or wool.
6. Obstruction of internal organs. Internal parasites cause obstruction or blockage of internal passages leading to mal-functioning of affected organs.

Types of parasites

• External/ectoparasites.
• Internal/endoparasites. 

External/ectoparasites.

Parasites found outside the body of the host organism.  Live on or under the skin.  Most belong to Phylum Arthropoda that has two classes of parasites.

LIVESTOCK HEALTH II (PARASITES)

Class insecta.

Tste tste fly. (Glossina spp)  

Undergoes complete metamorphosis from egg to adult. They give birth to larvae after eggs hatch inside the body.  Larva forms a puparium in damp soil near shady streams.

Harmful effects.

1. Transmit trypanosomiasis (Nagana) caused by a protozoan parasite (trypanosoma) contained in the saliva of the insect.
2. Sucks out large volume of blood causing anaemia.
3. The bites causes damage to skins and hides which acts as routes for secondary infection by pathogens.

Control of tste tste fly.

1. Bush clearing in order to destroy the breeding sites for the flies.
2. Spraying their breeding places with suitable insecticides regularly to kill adult flies.
3. Use fly traps impregnated nets.
4. Use of sterilising agents e.g. radio isotopes on male flies and then releasing them.

Keds (Melophagus ovinus)

Also known as sheep ticks. They are hairy and wingless blood sucking flies.

Harmful effects.

1. Causes considerable irritation under heavy infestation.
2. Due to irritation, the animal scratches and bites itself damaging the wool.
3. Retraded growth in lambs.
4. The animal becomes anaemic.

Control measures.

1. Shearing of infested sheep followed by hand spraying or washing them in appropriate chemicals e.g. pyrethrin, dieldrin, Malathion.
2. Routine sheep dipping.

 Fleas.

Wingless with strong legs adapted for leaping over long distances.  The mouth parts are adapted for penetrating the host’s skin and sucking blood. They are predominantly parasitic on those mammals and birds that are in a confined environment.

Harmful effects.

1. Cause irritation that leads to scratching.
2. Stickfast fleas of poultry on the combs and wattles causes wounds.
3. Stickfast fleas causes anaemia.

Control measures.

1. Animals sleeping places should be kept clean.
2. Dusting animals with appropriate insecticides.
3. Covering stickfast with petroleum jelly to suffocate them.

Lice.

Small wingless insects.

Biting lice (Mallophaga)  attacks mammals and birds.

Sucking lice (Anoplura)  attacks mammals.

Sucking lice has mouth parts reduced to styles for sucking blood.

Biting lice are provided with chewing mouth parts and live on the skin or feathers and feed on blood.

LIVESTOCK HEALTH II (PARASITES)

Harmful effects.

1. Causes irritation to the skin and the animal rubs itself on the objects.
2. Heavy infestation leads to poor health.
3. Poor feeding leading to emaciation.
4. Loss of production in birds.
5. Restlessness and anaemic conditions especially in poultry.

Control measures.

1. Perches in poultry houses should be smeared with volatile insecticides e.g. 40% nicotine sulphate solution.
2. Spraying, washing or dusting animals with appropriate insecticides.
3. Dusting with sodium fluoride on each bird.

Class Arachinida.

Consist of ticks (order Acarina) mites and spiders.

They undergoes incomplete metamorphosis.

Ticks.

 Cause injury and transmit diseases. Harmful effects

1. Ticks are vectors of livestock diseases e.g. ECF, redwater anaplasmosis and heartwater.
2. Suck blood from the host leading to anaemia.
3. Their bites causes wounds that acts as route for secondary infections.
4. Cause irritation to the animals through their bites.
5. Their bites lowers the value of hides and skin.
6. Some produce toxins that may have adverse effects on the host.

The life cycle of Ticks.

Ticks pass through 4 stages in their life cycle.

• The egg.
• The larva with six legs.
• The nymph with eight legs. Ø The adult with eight legs.

They require different number of hosts.

• One host tick.
• Two host tick.
• Three host tick.

Life cycle of one-host tick

All developmental stages occur in one host.

• Eggs hatch on the ground into larvae.
• The larvae climb onto the host via vegetation, suck blood becomes engorged and moult into nymph while still on the same host.
• The emerging nymph feed on the same host, become engorged and moults into adults.
• The emerging adults feed on the same host mate and the female drop off to the ground to lay eggs.

Examples of one-host ticks

1. The blue tick. (Boophilus  )
2. The Texas fever tick. (Boophilus  annulatus)
3. The cattle tick (Boophilus microplus)
4. The tropical horse tick.(Dermacentor nitens)

LIVESTOCK HEALTH II (PARASITES)

The life cycle of Two-host Tick

Larvae and nymph pass through their stages on the first host.

• Eggs hatch one the ground into larvae attach themselves onto the first host via vegetation.
• The larvae feed on blood become engorged and moult into nymphs.
• The nymphs feed on the same host become engorged and drop to the ground to moult.
• The emerging adult finds the second host feed on blood mate and female drops to the ground to lay eggs.

Examples of Two-Host Tick.

1. The red legged tick. (Rhipicephalus evertsi)
2. The brown tick (Rhipicephalus bursa)
3. The African Bont-legged tick. (Hyalomma truncatum)
4. The large Bont-legged tick (Hyalomma rufipes)

The life cycle of a Three-Host Tick.

Requires three different hosts to enable them to complete their life cycle.

• Eggs hatch on the ground into larvae. The emerging larvae attaches to the first host, feed on blood, becomes engorged and drop to moult into nymphs.
• The emerging nymphs seek a second host, feed on blood, becomes engorged and drop to the ground to moult into adults.
• The adults seek the third host, feed on blood, become engorged and the female drops off to the ground to lay eggs.

Examples of Three-Host ticks.

1. The brown ear tick (Rhipicephalus appendiculatus)
2. The east African Bont tick (Amlyomma variegatum)
3. The Bont tick (Amlyomma herbraeum)
4. The Gulf coast tick (Amlyomma maculatum)
5. The yellow Dog tick (Haemaphysalis leachii)
6. The fowl tick (Haemaphysalis hoodi)
7. The Brown Dog tick (Rhipicephalus sanguineous)

Control measures.

1. Natural/biological method.

Use of tick’s natural enemies that predate on ticks especially the nymphs.e.g. Birds such as egrets.  However only a small number of ticks is controlled.

Self-licking by the animal may also dislodge the ticks.

1. Mechanical methods.
2. Burning of infested pastures.

This reduces the ticks’ population by destroying the larvae, nymphs and adults. ii.           Interfering with or altering the ticks’ environment.

Making the environment less conducive restraining their development.   Include:

• By ploughing pasture land. This exposes eggs to suns heat for desiccation or burying them deeply.
• Topdressing pastures using lime or dressing using an acaricide. (Effective in control of blue ticks)

iii.       Fencing off the pasture land and farm.

Double fencing.  Used in combination with acaricide iv.      Starving ticks to death.

Can be achieved by rotational grazing which interrupts the life cycle of ticks.

1. Hand picking and killing them/de-ticking.

Effective on small scale.

Chemical methods of controlling ticks.

Involves use of acaricides. It is the most effective control measure.

Characteristics of an effective Acaricide.

• Should have ability to kill ticks.
• Be harmless to both livestock and human.
• Be stable.
• Should remain effective after having being fouled with dung, mud or hair.

Methods of Acaricide application.

• Spraying the animals regularly.
• Dipping animals completely in an acaricide solution.
• Hand dressing of animals against ticks using pygrease.

LIVESTOCK HEALTH II (PARASITES)

The Endo parasites.

Live within the body of the host animal.

Include:

• Roundworm
• Liver flukes
• Tapeworm
• Hookworm

Categories of Endo parasites.

Two Phyla of worms.

1. Platyhelminthes (flatworms) include the trematodes (flukes) and cestode (tapeworms).
2. The round worms
3. Platyhelminthes

Flatworms that are symmetrical.  Are hermaphrodites.

1. Tapeworm (Taenia spp)

Consist of a head (scolex) relatively small and a chain of segments forming the main part (strobilla)

Each segment is a proglottid.  The scolex has suckers and hooks or a combination of the two in some species.  Animals affected are pigs, cattle, sheep, goats and donkeys.

Symptoms.

1. General emaciation. Animals get thin, ribs and backbone show prominently.
2. Staring/rough hair coat.
3. Scouring and constipation due to digestive disturbance.
4. Pot-bellies especially in calves.
5. Oedematous swelling under the jaw.
6. When large numbers of tapeworms are present, they cause obstruction or blockage of intestines.
7. Proglottid are seen in faeces.
8. Anaemic conditions under heavy attack.
9. Excessive appetite. Animals tend to be ravenous.

The life cycle of Tapeworm.

There are two species of tapeworms.

Eggs are passed in human faeces in form of proglottids. The eggs are released from the segments ingested by the host (intermediate) cattle or pig. The eggs hatch in intestines, penetrate the intestinal wall and enters the bloodstream to the liver then to the muscles where they become cysts.

Cysticercus cellulosae prefers the muscular tissue and is the infective stage.  The cysts are eaten in undercooked meat and once inside the human intestine, the cysts wall dissolves and the parasite attaches themselves to the wall of the intestines and develops into adult tapeworms.

Control measures and treatment.

1. Use of prophylactic drugs such as anthelminthic drugs to kill the parasites in animals.
2. Keep animals houses clean and disinfected.
3. Practice rotational grazing and rest pastures to starve larvae to death.
4. Use of latrines/proper disposal of human excreta.
5. Proper cooking of meat.
6. Nematehelminthes.
7. Roundworms. (Ascaris spp)

Symptoms of attack.

1. Anorexia under heavy infestation.
2. Stiff dry coat or staring coat.
3. Dehydration and a pale mucosa.
4. Eggs and adults are seen in faeces.
5. General emaciation.
6. The animal may have diarrhoea.
7. Anaemic conditions under heavy infestation.
8. Pot-bellies especially in young animals.

             Life cycle of Roundworms.

Has no intermediate host.

• Eggs are laid in the alimentary canal of the host and pass out through faeces.

They undergo further development on the ground before they becomes infective.

• Eggs hatch into larvae, climb onto grass and are eaten by the host. They hatch into juveniles which migrate to the liver and lungs via the bloodstream as they change from one juvenile stage to another.  In the lungs, they move to the trachea where they are coughed and swallowed with sputum into the intestines. They develop into adults and mate and eggs are laid.

N/B hookworms penetrate the animal’s skin directly.

Control measures.

1. Hay and other feeds should not be contaminated with faeces.
2. Rotational grazing and resting pastures to starve the pastures to death.
3. Improving sanitation in animal’s houses by removing infected dung.
4. Drenching animals regularly with appropriate antihelminthes.
5. Proper use of latrines by farm workers.

Liver flukes (Fasciola   spp)

Heavy infestation causes a condition called fascioliasis.

LIVESTOCK HEALTH II (PARASITES)

Symptoms of attack.

• Loss of weight and emaciation.
• Pot-bellied conditions due to watery swelling on the body.
• Damage to the liver tissues and haemorrhage due to movements of flukes within the liver.
• Anaemic condition.
• Swollen and painful abdomen. Ø Recumbency precedes death.

Life cycle of liver flukes.

Intermediate host is the fresh water snail of the genus Limnea.

1. Adult flukes in the bile duct of liver lay eggs which are passed in faeces (3000-3500 eggs per day). Eggs in stagnant moderately warm water hatch into Miracidium (ciliated).  Miracidium is free living and swim by means of cilia to get to the intermediate host the water/mud snail (Lymnaea spp) and penetrate the skin by the rotating action of the cilia.
2. In the fresh water snail, miracidium produce embryos that hatch into sporocysts which develop into Redia multiply to produce more rediae that produce another larval form Meta-cercaria (encysted infective stage).
3. The meta-cercaria are ingested by the host in drinking water or pastures. After being swallowed by the primary host, they penetrate the wall of the intestines and hatch into adults.
4. The adults migrate to the liver grow and become sexually mature.

Control measures.

1. Controlling the fresh water snails through:
2. Physically killing them.
3. Chemically by use of copper sulphate solution, calcium cyanamide in stagnant water. iii. Draining swampy areas/levelling any depression that may hold water in the pastures.
4. Burning pastures in dry seasons.
5. Avoid grazing animals near waterlogged/marshy areas.
6. Drenching animals with anthelmintic drugs such as sodium sulphate and hexachloroethane drugs.

PRINCIPLES OF CONTROLLING ENDO PARASITES.

Factors to consider when controlling Endo parasites.

1. The flock and its environment.

The presence of one clinically infected animal s suggest the presence of other developing clinical signs in the flock.  Thus control measures should be directed to the whole flock.

2. The nutritional status of the stock.

It increase the resistance of animals to internal parasites infection.

3. Pasture management and Rotational grazing.

Resting of pastures help to break the cycle of parasites. It is determined by:

• Stocking rate.
• State of nutrition.
• Climatic conditions. Ø Herbage cover.

4. Housing management.

Adequate spacing and sanitary measures in livestock houses.  Include:

• Avoid overcrowding in the houses.
• Frequent removal of dung.
• Provision of clean bedding.
• Feeding and watering troughs should be high enough off the floor to avoid contamination.

5. Protection of the young.

They are more susceptible to worm infestation than adults.  Breeding animals should be dewormed before mating.

Creep feeding- letting young animals should graze ahead of the older stock so that the feed on quality and clean pastures.

6. Prediction of an outbreak.

Regular faecal sampling and examination to identify parasite eggs, study of climate and regular faecal egg count after drenching to know the efficacy of drugs.

Rules.

• The parasite or causal agents should be identified correctly.
• The best available drugs should be used at the right dose.
• Treatment must be given at the most advantageous time in relation to the life cycle of the parasites.

Drug Administration.

Strategic Treatment.

Administration done regularly with the purpose of avoiding contamination and infection during periods of risks.  Aims at reducing worm infection before climate favourable for parasites development.  It also reduces contamination of pastures.

Tactical treatment.

LIVESTOCK HEALTH II (PARASITES)

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