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View the document Parasites and parasitic disease

Parasites and parasitic disease

Parasites are organisms that live at the expense of another organism or "host". Internal parasites live inside the host in blood, muscle, or other body tissue which provides a favorable environment for growth and reproduction. External parasites live on or under the skin, or pierce the skin and feed on the animal's blood. In general, parasites do not kill the host, but cause a chronic state of ill-health which is reflected in low productivity and high susceptibility to other diseases. Young, pregnant, lactating, or malnourished animals are those most seriously affected by parasites.

Helminthiasis

This is a general name for any one of a number of conditions related to the presence of worms in the digestive system. While inside the host animal, they absorb food, interfere with digestion, or reduce the efficiency of blood-forming tissue. Sometimes the worms migrate to other parts of the body. The life cycle is completed when the female lays eggs which are passed out in the feces and which continue to incubate in pasture, manure, bedding, water, or intermediate host. Except in the case of hookworm (see below), the eggs are ingested by the new host (the draft animal) and hatch inside its digestive tract.

Symptoms: Chronic weight loss, variable diarrhea and constipation, weakness, lowering productivity. Other symptoms are specific to the type of worm.

Treatment: Numerous products are available and should be used as recommended by local veterinary or sanitary officials. Commonly used antiworm treatments (anthelmintics) are phenothiazine, thibenzole, and Vadephen. Administration varies from 2-4 times per year according to size and type of animal, and climatic conditions which affect the presence of the particular organism.

Prevention: Rotation of pastures and use of sanitary watering troughs reduces the likelihood that an animal will ingest parasite eggs; good feeding and management coupled with regular administration of anthelmintics (as prescribed).

Remarks: Worms may be classified in three major groups:

ROUNDWORMS

Ascarids affect pigs, cattle, poultry, and especially horses; they are intestinal worms which can impair growth or cause death in young animals. Worms may migrate to lungs and cause damage.

Hookworms are blood-sucking worms which are ingested or which enter the skin and migrate to the intestine, causing gastro-enteritis and anemia in ruminants and pigs.

Strongyles affect horses ant mules, causing anemia, emaciation, colic, and sometimes death. Some species of the worm appear in the feces.

FLUKES are found in all animals, especially those which graze in wet or marshy areas. The liver is damaged and fluids leak into the body cavity, giving the animal a "potbellied" appearance. Ruminants are especially susceptible. The disease is called Distomatosis.

TAPEWORMS primarily affect sheep and goats, but may be present in horses or cattle. Worms in the digestive tract can be very long and rob the animal of nutrients. Worm larvae may live in the bladder or muscle tissue and cause general weakness and lowered productivity.

Mange (Scabies)

Highly contagious skin disease transmitted by mites which burrow under the skin and breed in large numbers. The itching causes the animal to rub, depositing the organism on trees or fences where other animals then contract the disease.

Symptoms: Hair falls out, grey scabs appear, skin thickens and develops folds. Itching is intense and may cause animal to bite or rub itself, causing open lesions. With demodectic mange (present in West Africa), small bumps appear on the shoulder, neck, and trunk.

Treatment: Cut the hair; apply iodine, creosote or mixture of two parts oil, one part kerosene.

Prevention: Isolate infected animals; keep harness, bedding and stable area clean. Spray animal with solution of 0.66X lindane. Burn hair clippings of treated animals.

Remarks: Mange is sometimes classified along with scabies because both are transmitted

by mites and are similar in other respects. It may be noted that Chorioptic Scabies or leg mange is present in West Africa, especially in equine animals.

Ringworm

This fungus grows on the outer layer of skin, causing itching, and, in severe cases, secondary infection due to rubbing. Ringworm is contagious, affecting all animals and humans.

Symptoms: Raised, quarter-sized patches of hair with crusty edge, especially on the ear, nose, eyes, lips, or any area that tends to be moist or humid. The patch becomes raw when the animal rubs or bites it in an attempt to relieve the itching.

Treatment: Cut the hair, remove the scabs with a brush or curry comb; wash with soap and boiled water and apply full strength iodine, creosote, or fungus ointment every 2-3 days.

Prevention: Isolate infected animals; clean and disinfect brushes and tack (harness) regularly; ensure that stable is well-ventilated and sanitary.

Remarks: Fungus diseases are most common during humid seasons, with animals recovering during the dry months.

Ticks

Ticks attach themselves to the skin, burrow, and feed off the animal's blood. They also spread fevers: piroplasmosis, brucellosis, typhus, East Coast Fever, heartwater. Grazing animals are most likely to be affected because ticks cling to tall grass and attach themselves to the passing host (especially during summer months).

Symptoms: Ticks are visible on the underside of the animal and around the ears. The animal kicks up at its belly shakes its head. Eventually it becomes anemic and starts to lose weight.

Treatment: Dab on kerosene, turpentine, or parafin.

Prevention: Regular application of insecticides as recommended by local veterinary service. Sprays or dips can be very effective if done every 57 days; commonly used products include Tigal liquid (mix one part tigal in 800 parts water), Tox (2.5 parts in 1,000 parts water), Gamatox (1 kg in 500 liters water). For ear ticks, use Lindane, Gamatox (mix 1 kg in 500 liters of water), Tox (2.5 parts/1,000 parts water).

Trypanosomiasis

This is a disease caused by parasites called trypanosomes which live in the blood and which are carried by the tsetse fly (glossina), or other biting insects. The disease affects the nervous system, making the animal lethargic and chronically thin; sometimes death results. All animals and humans are affected. Zebu cattle and horses are particularly susceptible. N'dama cattle and some donkeys have a high resistance. The disease is especially prevalent in a band or "vector" which crosses the African continent just north and south of the equator.

Symptoms: Intermittent fever, poor appetite, chronic thinness (especially seen in sunken flanks), swelling of lympth glands, eye mucus and watering, accelerated respiration.

Treatment: No known treatment.

Prevention: For cattle-Vaccination with Ethedium three times yearly, or with Prothedium or Berenil as prescribed. For horses-Vaccination with Trypadine as prescribed.