Disease Control 8

1.    ACARIDS

INTRODUCTION

The order Acarina belongs to the class Arachnida and contains many sub-orders. Ticks belong to this order and the sub-order Ixodoidea and have been dealt with in previous lectures. Mange Mites are also members of this order, and are characterised by having, in their adult and nymphal stages, 4 pairs of legs and a body not clearly divided into a head, thorax and abdomen. Mites occur  throughout the tropical world. The presence of mites is indicated by itching, irritation of the skin and dermatitis in various forms.

SYMPTOMS AND DIAGNOSIS

Mites can be found in scrapings from the skin. The general effect is to produce a chronic inflammation with thickening of the epidermis and loss of hair.

TREATMENT AND CONTROL

This is difficult, owing to the mites’ habit of living deep within the skin. Spontaneous recovery may occur. Proprietary injectable preparations (Ivermectins) are now being used with some success.

2.    NEMATODES (Roundworms)

INTRODUCTION

Internal parasites in cattle occasionally cause death under conditions favouring massive infestation, when nutritional levels are low. The biggest losses to the farmer are the slow losses caused by decreased growth and production.

CAUSE AND TRANSMISSION

Eggs are passed out in the dung of cattle. Under warm, moist conditions, these hatch into very small larvae which in 6 days develop to the stage of being able to infect cattle. They climb up blades of grass and are ingested by grazing animals.

SYMPTOMS AND DIAGNOSIS

A severe loss of condition, lifeless, dull coats and anaemia appear. However, the most serious infestation is a sub-clinical infestation, because the worms do not cause any noticeable symptoms besides the fact that the animals do not grow or do as well as they should do.

TREATMENT AND CONTROL

Nearly all cattle are infected with some worms, and usually it is a mixed infestation. Young   animals,

i.e. from weaning up to two years old, are the most susceptible stock. Older cattle develop some degree of roundworm resistance. This resistance breaks down if the animals are stressed by disease or undernourished. Warm, damp conditions, which are experienced during the rains, provide ideal conditions for the worm larvae to survive. Higher stocking rates also increase the danger. A dosing programme should be carried out after consultation with a veterinarian following examination of faeces samples. Read the instructions on the label and dose with the correct quantity. This is very important. Make sure the correct remedy is used for the worms to be treated.

3.    FLUKE

INTRODUCTION

Liver fluke, Fasciola hepatica and Fasciola gigantica, cause damage to the liver mainly in cattle, but also in sheep and other ruminants. It occurs in most tropical countries where conditions exist for the survival  and  multiplication  of  the  snail,   the  intermediate  host,  which  thrives  in  low-lying, wet,

marshy pasture, areas of high temperature and humidity. Drinking troughs should be regularly checked for snails.

CAUSES AND TRANSMISSION

Liver flukes live in the bile ducts of ruminants. The adults lay eggs (3 000 by F hepatica and 20 000 a day by F gigantica) which pass out of the host animal with its dung. When the eggs hatch, if they are dropped in a wet area, the small worms must find and penetrate a fresh-water snail, where, they multiply significantly.

They leave the snail as cercariae and climb on to a plant. They wait there until the plant is eaten by a ruminant. The cercariae travel in the digestive tract of the ruminant to the small intestine where they change into small liver flukes, they pass through the wall of the small intestine and migrate to the liver and eventually end up in the bile duct where they can live for several years. They are up to 22mm long and 10mm broad, flat and shiny brown. Due to the longevity of this parasite, undosed cattle accumulate infection over the years.

SYMPTOMS AND DIAGNOSIS

As the cercariae develop into mature flukes in the liver, the main symptoms will involve the digestive system. Their presence causes thickening of the wall of the bile duct causing consequent anaemia. Flukes may occur in the alimentary tracts of cattle and other ruminants.

TREATMENT AND CONTROL

It is important for a cattle producer to know the fluke situation on his property. Faeces samples are not reliable since egg-laying by liver fluke is erratic. Every opportunity should be used to check livers for the presence of fluke, such as during post-mortem examination. When cattle are slaughtered at abattoirs, meat inspectors condemn livers because of the damage which making them  unmarketable. Anti-snail measures are costly and often give only temporary success.

SHISTOSOMIASIS (Blood Fluke Disease – Bilharziasis) INTRODUCTION

This is a disease common to Africa and over 50% of cattle in some African countries are infested with it. The parasites can be seen in the blood vessels of the mesentery, the membranes supporting the intestines when held against the light. They appear as white worms about 20mm long with a thin black line down the centre.

The disease is also of major danger to humans. They differ from other flukes in that they are unisexual.

CAUSE AND TRANSMISSION

Females penetrate the wall of the intestine or bladder or even the nasal mucosa and lay eggs which pass out via the capillaries into the lumen of the organ and are voided with the faeces or urine. They hatch and miracidia enter aquatic snails where their life cycle is similar to Fasciola. Diseased  livestock may show pneumonia due to the passage of the young parasites through the lungs. The sharp points on bilharzia eggs enable them to break through the intestinal wall and be passed out with the faeces.

Symptoms and Diagnosis

A serious situation occasionally arises where cattle concentrations coincide with a high snail population, thus causing lowered productivity and even mortality. This is especially true where  stress factors like malnutrition are also involved.

TREATMENT AND CONTROL

Prevention measures are most important on properties which have a bilharzia problem. Treatment for bilharzia is still expensive and rather complicated, but cases do occur where this is necessary and veterinary advice should be sought regarding the choice of drug and dosage. The ability of cercariae to penetrate the skin makes elimination difficult.

4.       TAPEWORMS

INTRODUCTION

All tapeworms go through a cycle where their eggs are ingested and become bladder worms in the intermediate host. The intermediate host is in turn eaten by the final host where they develop into tapeworms. Here the adult tapeworms produce egg-laden ripe segments which are released to pass out with the faeces and they thus recommence the cycle.

CAUSE AND TRANSMISSION

Cattle act as an intermediate host to various tapeworms. The best known is Beef Measles where the bladder worms, half the size of a pea are found in the flesh between the muscle fibres. Their importance lies in their potential danger to human health. If it is not thoroughly cooked, infected meat causes tapeworm in the people who eat it. At approved abattoirs certain muscle cuts are made during meat inspection to check for the presence of the measles. About 1% of all carcases are found to be infected at the various abattoirs.

SYMPTOMS AND DIAGNOSIS

The effect of the tapeworm on animals may not be great. Light infections seldom have much effect. Diagnosis is made from the presence of tapeworm segments found in the faeces or intestine.

TREATMENT AND CONTROL

Niclosamide can be used on ruminants at a dose rate for cattle of 50mg/kg. Lactating cows should not be treated. Ploughing and cultivation of pasture will temporarily reduce the number of tapeworms.

5.    SUMMARY

Common Infectious Livestock Diseases and Drugs for the Treatment thereof

BACTERIAL DISEASES

DISEASE	SOURCE OF INFECTION AND SYMPTOMS	PREVENTION	TREATMENT
Anthrax (Bacillus)	Ingested or via insects. Death. Fever, trembling, diarrhoea, swelling of throat, neck or chest. Blood exudes from Orifices of carcasses.	Vaccinate. Destroy all carcasses.	Nil
Botulism (Clostridium)	Ingested flesh/bones. Toxins poison and cause paralysis to swallow.	Vaccinate. Destroy all carcasses.	Nil

DISEASE	SOURCE OF INFECTION AND SYMPTOMS	PREVENTION	TREATMENT
Brucellosis ‘C.A.’ (Brucella)	Ingested grazing. Abortion, premature or weak calf.	Vaccinate heifers.	Nil. Isolate suspects.
Enteroxaemia ‘Pulpy Kidney’ (Clostridium)	Change in feed predisposes. Death. Paralysis or convulsions. Eye is red. Diarrhoea.	Vaccinate.	Nil
Footrot (Bacillus)	Small wounds, wetness predisposes. Raw and swollen. Abscesses may burst.	Ensure dry conditions.	Sulpha or penicillin.
		Formalin or CuS04.
Malignant Oedema (Clostridium)	Infected wounds become painful and swollen.	Vaccinate.	Sulphas or penicillin injection.
Navel ill (E. coli, Bac., Pasteurella)	Bacteria enter via navel. Lesion. Painful joints, may rupture. Lung abscesses.	Disinfect with iodine and tie.	Sulphas or penicillin. Open lesions.
Paratyphoid (Salmonella)	Ingested, multiply under stress. Yellowish diarrhoea, pneumonia.	Vaccinate early. Hygiene.	Furazolidone Chloramphenical.
Pasteurellosis	Enter via mouth, lungs or wounds. Septicaemia, pneumonia, nasal discharge.	Vaccine limited coverage.	Sulphas or penicillin.
Quarter-evil (Clostridium)	Via mouth or wounds. Fever, swollen with crepitation (feels crackly when touched). Toxins poison the animal.	Vaccinate up to three years cattle.	Antibiotics
Ringworm (Fungus spp)	Crusty lesions, short hair.	Isolation of Anti- fungals.	Iodine.

DISEASE	SOURCE OF INFECTION AND SYMPTOMS	PREVENTION	TREATMENT
Swine erysi- pelas. (Bac.)	Via mouth. Septicaemic early mortality. Red quadrangular skin lesions. Cardiac failure		Penicillin.
Tetanus (Clostridium)	Deep anaerobic wounds. Stiff muscles, jaw locks.	Vaccinate.	Tranquilisers. Disinfect.
Vibriosis (Vibrio fts)	Venereal. Repeated services, abortion, Vaccinate. Irregular oestrus.	Vaccinate.	Penicillin & Streptomycin.
White scours (E. coli)	Ingested. Death without signs. Painful abdomen, white yellow or bloody scours. Fever	E. coli vacc. Hygiene	Antibiotics.

PROTOZOAL DISEASES

DISEASE	SOURCE OF INFECTION & SYMPTOMS	PREVENTION	TREATMENT
Gallsickness ‘Anaplasmosis’	Blue tick. Fever, anaemia, constipation, jaundice.	Vaccination. Dipping.	Tetracycline.
Redwater ‘Babesiasis’	Blue tick. High fever, anaemia, red urine, slight jaundice.	Vaccination. Dipping.	Phenamide, Babesan, Berenil.
Theileriosis	Brown-ear tick. Salivation, loss of appetite, tarry diarrhoea, swelling of superficial lymph nodes.	Dipping.	Nil.

VIRAL DISEASES

Blue tongue	Midges. Fever, swollen lips and tongue, salivation, diarrhoea, blue membrane of mouth. Haemorrhages.	Vaccination.	Sulphas for Secondary infections. Rest.
Foot and Mouth	Contact with carriers or diseased. Fever, salivation, blisters in mouth become sores. Also between hooves, muzzle, udder and teats.	Slaughter of infected and contact animals. Vaccination.
Heartwater	Bont tick. Fever, listlessness. Typical nervous symptoms. Fluid in pericardium & body cavities.	Vaccination. Dipping.	Tetracyclines.
Lumpy-skin disease.	Insects, Fever, lumps appear on skin which later dry out. Lymph glands swell.	Vaccination.	Antibiotics for secondary infections.
Rift Valley Fever	Mosquitoes. Fever, abortions, bloody diarrhoea, white specks in liver.	Vaccination.	Nil.
Three Day Stiff Sickness (Ephemeral Fever)	Biting insects. Fever, stiffness, lame in one leg. Loss of appetite.	Vaccination.	Nil. Treat secondary infection.