UNITED NATIONS  DEVELOPMENT PROGRAMME Emergencies Unit for Ethiopia

INTRODUCTION

Livestock diseases are the major cause of economic losses to the peasant farmer and pastoralists in Ethiopia amounting to hundreds of millions of birr annually. Because livestock are the chief source of cash income to small holders, up to 88% in the highland livestock-cropping system, diseases are an important cause of reduced productivity of meat and milk as well as draft, hides and dung fuel. Although many of the diseases could be controlled by available vaccine technology, timely recognition of the disease followed by acquisition of the pharmacueticals are lacking due to the remoteness of the livestock holder and the shortage of infrastructure facilities to support health services delivery. Consequently, in Ethiopia the majority of disease intervention consists of mass inoculations following outbreaks rather than preventive measures.
 

VIRAL DISEASES

Rinderpest

Rinderpest is a highly contagious plague of cattle which has caused devastating losses in many parts of the world. Through the Pan-Africa Rinderpest Campaign, the disease is under control except in certain foci. Sheep and goats are more resistant than pigs, cattle and wild ruminants but can transmit the disease to them. Transmission is by close contact inhalation of the virus. After incubation of 6-15 days a high fever followed by sleeplessness and still later by discharge from the nose and eyes. Discrete erosions on the inner lower lips coalesce and ulcerate. Three to five days after incubation severe diarrhoea occurs indicating similar ulceration of the stomach and intestine and the body temperature drops prior to death, which follows soon after.

Treatment is not feasible but because of the ease with which the virus can be destroyed and because recovered animals are not carriers, elimination of the disease in an outbreak area is a matter of slaughtering severely infected animals and total vaccination of all susceptible animals. Strict quarantines need to be enacted to prevent wild animals from becoming infected and reintroducing the disease. Subsequent vaccination of growing stock following weaning is essential until the disease is eliminated from the area. Refrigerated meat can carry the virus for months.

Foot-and-mouth disease

A highly contagious disease of the mucosa membranes and the foot tissue adjacent to the hoof, this disease is known over most of the Tropics with outbreaks still being common in Ethiopia. The virus, which occurs in 7 serotype with many subtypes, is transmitted mainly by ingestion of forage contaminated by infected animals. The virus can survive over a year on infected premises, for months on clothing, hair, hay, straw packing and vegetables, and in meat that is incompletely frozen or boiled. It can be carried by motor vehicles from infected areas and is resistant to strong disinfectants.

After incubation of 3-8 days, a high fever, especially in young stock, is followed by sleeplessness and swelling of the lining of the mouth. Slow, smacking chewing along with reddened vesicles on the mucosa tissues are common by the third day. One or more of the feet may show swelling and the lame animal may go down over a 2 week period. Lameness is the main symptom in pigs, sheep and goats and though the disease is usually more mild, abortion and shedding of the hoof may occur.

Control is by slaughter and mass vaccination however the former may be prohibitively expensive. All animate things should be disinfected and inanimate burned or buried. The pasture area should be quarantined for at least 1 month. Since there is little cross-immunity among sub-types, vaccines are best prepared from locally isolated viruses. Vaccines are only effective for up to 8 months and a booster is best used after 3-4 months. A single yearly vaccination has been effective in areas where the virus commonly occurs. There is no control programme in Ethiopia except in large farms due to the high cost of the vaccine.

Pox Group

Sheep pox and goat pox in sheep are very contagious viruses spread by contact and inhalation often causing 50% mortality. After 2-14 day incubation, a high fever, depression, nasal discharge and skin lesions occur. Control consists in isolation of infected flocks and vaccination of outbreak area flocks, though vaccination of flocks with the disease is unlikely to prevent deaths in the flock. A specific camel pox, attacking only rabbits and young camels, runs a benign course of 2-3 weeks. The disease is widely distributed in Ethiopia and the regular MoA control programme makes vaccines available.

Lumpy Skin Disease

Although being a related poxvirus conferring resistance to sheep pox, this virus is rarely fatal but causes severe losses in terms of milk production, body condition and hide quality. Once confined to South Africa, it has moved north into Kenya, Sudan and Ethiopia. Control consists of vaccination with either sheep pox or Lumpy Skin pox of all animals over 6 months but care must be exercised not to introduce sheep pox into new areas. The disease exists widely in the country and a vaccine is being used.

PPR (Peste de petits ruminants)

PPR is another virus with antigenic relationship to the Rinderpest family, which includes distemper and measles. PPR is newly diagnosed and is already widely distributed disease affecting sheep and goats. The virus spreads very rapidly and is present in high amounts in body excretions, especially diarrhoeic faeces. Vaccination is the best means of control but no national strategy exists.

ORF-Contagious Ecthyma

Antigenic to goat pox but not sheep pox, this highly infectious virus causes pustular, scabby lesions of the muzzle and lips. It is common in the highlands during the rainy season when shoats graze wet, dewy grass. Mortality may reach 25-75% in lambs due to respiratory lesions. Spread in the flock is very rapid and occurs by contact, abrasion and breaks in the skin. Affected lambs may be discouraged from suckling and grazing, causing decline and death.

Control consists of isolation of infected individuals and flocks. Persistence in a flock from year-to-year is common in which case lambs should be vaccinated within 6-8 weeks while still suckling. Vaccination, which is effective for 2 years, is by painting a saline suspension of scabs onto the scarified inside the thigh. No vaccine exists in Ethiopia and local treatment consists of disinfection of the mouth.

African Horse Sickness

This is a highly fatal disease of horses, mules and donkeys which is spread by biting midges or gnats (Culicoides spp.). The disease is most common in low lying swampy areas after heavy rainy periods when the insect is present. Fever, laboured breathing and nasal discharge is followed by sweating, staggering and lying down. The nasal discharge becomes voluminous and laboured breathing inhibits ingestion with death in 4-5 days.

Vaccination of all equine in the area and a broad buffer zone is recommended to restrict spread by infested wind-blown midges. Also, care should be exercised to quarantine animals in infected areas until the passage of the rainy season. The disease occurs over a large area of Ethiopia and use of vaccination has started.

Rabies

Rabies is a highly fatal disease to which all mammals including man are susceptible. Wild and feral carnivores are the chief carriers to domestic stock. Domestic dogs and cats are the chief transmitters to man and care must be taken even if the infected animal just licks an open wound. Suspected animals should be restrained and watched for evidence of mania and paralysis of the hind limbs. Free animals try to bite other animals they come in contact with while restrained ones will bite even inanimate objects. Incubation varies from a few to many days depending upon the severity and distance of the entry wound from the central nervous system. Positive diagnosis is relatively difficult and involves laboratory identification of the presence of Negri-bodies in the brain tissue.

The disease is not often reported in rural areas and control consists of destruction of infected animals. In urban areas vaccination of free roaming animals is recommended. Persons suspected of having contact with a rabid animal can now be protected by an oral vaccine if treated soon after exposure.

Newcastle disease of fowl

Newcastle disease is an acute, highly contagious viral disease that occurs throughout the world. It results in drastic lowering of egg production and death or delayed maturity of layers and broilers The virus can survive 6 months in infected eggs or chicken houses and can be carried by birds or on workers' clothing. The disease spreads rapidly within the flock by sneezing, coughing and consumption of common drinking water. Precipitous drop in egg production as well as soft shells within 2-3 days of infection is accompanied by lack of alertness, gasping and sneezing. Paralysis of the legs, wings and neck cause strange contortions. Usual morbidity of 100% is followed by mortality of around 50%, especially in young and baby chicks.

Control consists of sanitation of chicken houses before re-use and isolation of infected birds. Preventative vaccination can be administered in drinking water at age 2 weeks and again 2-3 months later which brings about adequate immunity levels within 1-2 weeks and lasts for about 6 months. Although the vaccine is produced in Ethiopia, it is routinely used only by the large farms.
 

BACTERIAL DISEASES

Anthrax

Anthrax, caused by Bacillus anthracis, is world-wide and is characterized by sudden death with black tar-like exudates from natural orifices. Following incubation of 1-2 weeks, muscle tremors, mucosal congestion and fever may precede collapse and terminal convulsions followed by the dark bloody discharge. In less acute cases, listlessness, haemorrhage of the mucosa membranes, abortion, swelling of the perineum, throat and abdomen can last for about 2 days. Sudden death of animals in the area of known outbreaks is cause for suspicion of anthrax. The soil around an infected carcass becomes heavily infected with spores which can remain viable for re-infection for 20 years. Carnivores readily spread the spores to forage in the surrounding area.

Although antibiotics are effective in the treatment of anthrax, the usually rapid course of the disease limits their effectiveness. When confirmed, stringent regulations prescribe burying carcasses at 2 meters or complete burning and quarantine of the area for 6 months. Vaccination of cattle in areas of known outbreaks is recommended for three successive years.

Blackleg

Blackleg is an infectious, but non-contagious disease of young cattle and occasionally sheep/goats caused by Clostridium chauvoei. The organism is widespread in the soil where the spores have been concentrated by continuous grazing. The spores can be found in the liver and spleen of normal healthy animals but enter through the mucosa membrane of the alimentary tract following ingestion. In sheep and goats, the spores can enter through wounds including the reproductive tract following birth.

Following a high fever, depression, anorexia and lameness in an upper limb, the limb becomes cold, painless and dark in colour with gas formation in the interior. Death from toxaemia occurs within 2-3 days of the fever. In sheep and goats, the dark lesion usually occurs at the site of the wound and entry of the organism. Early treatment, as soon as gas formation begins, with antibiotics is necessary. Proper control consists in destruction of carcasses by burning. Vaccination of young stock is cheap and effective. Sheep and goats should be vaccinated before lambing, castration or docking the tail.

Pastuerellosis

Outbreaks occur during periods of environmental stress causing 50-100% morbidity and mortality. Pasteurella multocida persist on tonsil and nasal mucus tissues of infected animals and are spread by ingestion or inhalation from contaminated forage. Fever, profuse salivation and depression are followed by death within 24 hours. Treatment with antibiotics is effective and vaccination, even in the face of an outbreak, is effective.

Contagious bovine pleuropneumonia CBPP and Contagious caprine pleuropneumonia CCPP

These two similar mycoplasmic bacteria cause lesions of the lungs and pleura of cattle and goats, inflicting serious economic losses. Infected animals may take 3-6 weeks to show a rise in temperature, loss of appetite, coughing, arched back and lowered head. Respiration is shallow, rapid and laboured. Death may come in 1-3 weeks of symptoms or, in less severe cases, coughing and weight loss can last 7 weeks.

Mortality is usually 50% with half of the surviving carrying the disease `encapsulated' in lung tissue and transmitting the disease to other herds for as long as 3 years. The disease is spread through discharged nasal droplets and so is more likely to occur when cattle are confined.

Infectious Bovine Keratitis (IBK)

IBK or pinkeye is nonfatal and rarely causes loss of the eye. It is caused by the bacterial (Moraxella bovis) inflammation or keratization of tissues around the eye. Bacteria are spread by face flies and ocular fluid on tall grasses in late summer and autumn.

Opacity of the cornea in infected cattle causes partial blindness, reduction in grazing and loss of milk production. Weight loss in calves and reduced weaning weights result. Acute cases respond to daily injection of the conjunctival sacs with antibiotics and surface applications of ophthalmic ointments.
 

Brucellosis in cattle, sheep and goats

Brucellosis has been recognized since ancient times inciting uteral and fetal infections resulting in abortion and infertility. Brucella abortus in cattle and Brucella melitensis in sheep and goats (known as undulant fever in man) can be contacted through ingestion, respiration, conjunctiva or broken and unbroken skin. Depending upon the titer of bacteria contracted, an incubation of days to weeks result in the occurrence of nodes in the lymphatic, lactinal, uterus, spleen, liver and joints. Abortions occur in the 5th month of pregnancy. Retention of the placenta and infertility commonly result, those which do breed can carry the bacteria to other first calf heifers causing another round of abortions.

Common means of transmission are through infected forage containing foetal membranes, discharges, faeces, and urine or, in the case of man, through milk from infected cows. Control consists of vaccination of young female animals before pregnancy. Blood testing (Bang's test) and disposal of carrier stock is recommended for cattle but not effective for sheep and goats since complete elimination is almost impossible. Sanitation of infected foetuses, membranes and the surrounding area is essential. Animals from infected herds are best isolated during parturition and new herd animals should be kept separate until they have given birth. Milk from infected herds must be boiled before it is consumed by humans.

Dermatophilosis, Actinobacillosis and Actinomycosis

This group of diseases, though not fatal, cause losses in production. Dermatophilus congolense causes moderate to severe emaciation and debilitation with resultant loss in meat, milk and wool production and hide quality. Development of the Ethiopian dairy industry is seriously hampered by the susceptibility of the European derived stock. Actinobacillus lignietese causes inflammation of the tongue in cattle and in the soft tissues of the head and neck of sheep causing difficulty in eating. Actinomyces bovis enter through breaks in the gum tissues causing osteomyelitis of the head and jaws.

Vaccination is not an effective means of control for these three diseases. Actinobacillosis does not respond to localised application of Iodine or antibiotics and isolation of infected animals to prevent contamination of feed/water troughs is recommended. Treatment and control measures for the other two diseases have not yet been well defined.

Footrot and Abscess

Arising from abrasions to the foot, Fusobacterium necroforum and probably other bacteria are contagiously spread from one animal in a herd to another, especially during wet weather. Acute swelling of the skin, tissues and joint above the hoof result in the spreading of the claws. Sudden lameness and loss of mobility severely reduce productivity and may spread within the herd. Prompt cleaning of the foot tissues and injection with Sulpha-antibiotics is necessary. Control consists of moving corals to new areas, keeping the herd out of areas where wetting of the feet is constant and removing cattle from stubble or stony fields where injury may occur.

Heartwater

Another disease in Ethiopia of exotic derived stock, this one is caused by the rickettsia Cowdria ruminantium that is transmitted by ticks. Fever is the first symptom 13-17 days after being parasitized by ticks but is followed by diarrhoea, nervous incoordination, muscle twitching and finally loss of mobility. The disease is so named because of the yellow fluid found in the sack surrounding the heart. Treatment is with sulpha or tetracycline drugs but prevention by controlling ticks is best.
 

PROTOZOAL DISEASES

Trypanosomiasis

Trypanosomiasis or Tryps (Sleeping sickness in humans) is a group of diseases caused by the widely distributed and highly variable members of the Trypanosome species. In most of Africa transmission occurs by cyclical passage and multiplication in one of several species of the biting Tsetse fly (Glossina). Of the three main groups of flies, one is adapted to open woodland savanna which is the most common type of cattle country. Another is adapted to riverine and lake shore habitats where cattle congregate for water and to escape heat. The third group inhabit highland forest areas where cattle are moved during the dry season. This includes the forested areas of western and southwestern Ethiopia, where expansion of agricultural production could be possible. The disease is constantly present depending upon the fly population and has caused an estimated loss of 500 million birr in 5 zones of western Oromia (Region 4).

Warm and cold-blooded animals are hosts and so control is difficult. With all Trypanosome parasites, common symptoms of hosts include intermittent fever, progressive anaemia and loss of weight. The nutritional status of the animal and the stress/activity required can accelerate the progress of the disease. Dehydration may occur when infected animals are too weak to trek for water. Ploughing or physical exertion can induce acute anaemia and death within 1 week. On the other hand, nutritional intervention and a non-stress environment can allow gradual recovery but relapse will occur under stress.

Treatment with a number of drugs is complex, unavailable in Ethiopia and relative expensive for the small holder. Berenil, intramuscular and Homidium, deep intramuscular are the most effective and must be alternated because the Trypanosome can altar its protein coating to resist the drug over time. It is essential to make frequent blood examinations of cattle under drug treatment and switch drugs whenever animals show relapse indicate a build-up of resistance to one of the drugs by the trypanosome. Repeated re-injection every 3-4 months is common but should be accompanied with examination to determine whether to continue one drug or switch.

Vector control consists of two practical interventions, trapping and spraying the Tsetse fly. Traps constructed of black cloth with a blue centre were found to be attractive to the flies. These are placed near the corals where dung and urine also attract the flies. Insecticide baited jars are placed at the centre of the trap to dispose of those which enter. Also animals are treated to discourage flies by spraying or pouring on insecticides. Clearing of brush and trees destroys the flies habitat in the highland but can hardly be encouraged on a large scale for environmental reasons.

Trypano-tolerant cattle is a long-term possibility but of little current hope. The N'Dama cattle were introduced to Africa over 7000 years ago and have evolved a level of tolerance but even this breaks down under poor nutrition and stress. Meat production is good but milk production is low and animal size does not favour use for draft. Cross-breeding to the Zebu type, which has been in Africa only 1300 years, is a difficult procedure with complicated bio-technological techniques for identification of chromosomes involved in tolerance traits. Recently introduced European breeds are extremely susceptible.

Anaplasmosis

Anaplasmosis is a tick-borne bacterial disease causing jaundice, anaemia and debilitation of mainly cattle but also sheep and goats. Anaplasm marginale, the most pathogenic, and A. centrale infect cattle and wild ruminants while A. ovis are present in sheep and goats. Because the anaplasm attacks the red blood cells, anaemia and jaundice appear in 3-4 weeks and older, more susceptible animals may die. Others may show signs of aggressiveness, anorexia and weakness or unwillingness to move.

Because of the commonness of ticks, it is difficult to eradicate. However control of ticks and vaccination are helpful if the disease is common in the area. Otherwise treatment with broad spectrum antibiotics such as tetracycline intravenously drastically reduces the parasite numbers. Although widely occurring in Ethiopia, there is no control design or vaccine in the country.

Babesiosis

Babesiosis or tick fever in many animal species is caused by several widely distributed species of Babesia which are transmitted by blood-sucking ticks. Generally 7-10 days after contaminated ticks attach to the animal, the temperature rises followed by anorexia, weakness, salivation and diarrhoea. Destruction of red blood cells causes increased respiration, heart rate and a change in urine colour to dark brown. The transmitting tick may go through 1-3 stages of attachment to different hosts before becoming an engorged adult, dropping off and laying eggs. It is known that the parasite multiplies in the tick and it is thought that sexual reproduction also occurs.

Treatment is recommended only for valuable breed stock since there is a narrow range in dosage between therapy and toxicidity. Control of the disease consists of control or elimination of tick vectors, control of cattle movement from infested areas to disease free areas and in areas where the disease is common, vaccination with a small amount of blood from a known carrier. The majority of animals will develop an increased level of tolerance, though some may succumb and the number of carriers will be increased.
 

ENDOPARASITES

Helminthic Diseases

There are three main groups of parasitic worms infecting domestic animals, the trematodes or flukes with the liver fluke being most important, the cestodes or tapeworms and the nematodes. A great variety of these infest domestic and wild animals as well as man. Many have secondary hosts and reproduce in such large numbers that elimination is impractical in the warm tropics unless the animals are confined. Antihelmenthic drugs are expensive and generally unavailable in Ethiopia.

Haemonchus

Haemonchus contortus intestinal worms cause poor growth, production and heavy death losses. Larvae and adults are vigorous blood suckers causing anaemia and protein deficiency due to interference with digestibility and absorbtion of protein, calcium and phosphorus. Death may be acute from blood loss or more gradual from high red blood cell production and exhaustion of body iron and protein.

Spread is through ingestion of contaminated forage and under favourable conditions female Haemonchus can lay 10,000 eggs per day for months causing gross contamination of pastures. Drenching with antihelmentics is effective but may need to be repeated every 2-4 weeks during the rainy season because reinfestation from the common pasture occurs. Drenching at weaning or at the dry season will boast productivity at times when reinfestation is less likely.

Faciolasis

The liver fluke, Fasciola hepatica mainly in sheep and Fasciola gigantica mainly in cattle, inhabit the bile duct or intestine causing Fascioliasis or damage to the liver which is characterized by anaemia, jaundice and swelling of the liver. Each mature fluke develops into many eggs in the intestine which are then passed in the droppings. A miracidium develops which penetrates the snail and multiplies 7-9 weeks in the snail before developing into cercariae encysting on grasses where the cattle graze. Cysts ingested take 10 weeks to mature in the intestine.

There are a number of drugs to treat liver flukes which are administered either as a drench (forcible swallowing) or intramuscularly. Because of the remarkably prolific breeding habits of the snail and the number of cercariae which may be carried by one snail it is impractical to try to eliminate the snail or the disease.

Shistosomiasis or the blood fluke inhabits the blood vessels of man and livestock. It is found only in southwestern Ethiopia and an attempt by the Carter Foundation is being made to eradicate it.

Thelaziasis

Thelazia spp. are carried by faceflies, larvae being deposited on the conjunctiva while the fly is feeding on eye fluid. Tearing, conjunctivitis, corneal ulceration and abscess. Blindness may result in reducing production. Treatment of the tear gland with .05% iodine solution is effective.

Lungworm

Mature lungworms, Dictyocaulus viviparus, live in the bronchia where eggs are coughed up, swallowed, and pass three developmental stages before being passed in the faeces. A single infected animal may contaminate a pasture with 33 million larvae. Larvae are ingested when heavily stocked pastures force grazing near faecal pads. Symptoms are similar to pneumonia but no response will occur from antibiotic treatment. Treatment with modern antihelmenthic drugs is recommended and control of animal numbers in infested grazing areas reduces ingestion.
 

ECTOPARASITIC DISEASES

The exterior parasites of livestock include insects (flies, mosquitoes, lice and fleas) and ascarides (mites and ticks). Some are merely blood biting or sucking, others are carriers of previously listed diseases and still others lay eggs which hatch into larva living in the animal flesh. Some are not felt by the animals, some cause itching, scratching, rubbing, tail switching, stomping and head thrusting. In addition to the blood loss and tissue infections, ectoparasites cause additional stress on animals. Control measures such as spraying and dipping are difficult, requiring crushes and pits, and are usually not effective if the animals are roaming or in contacting other herds and wild animals.
 

REFERENCES:

Hall, HTB. 1977. Diseases and Parasites of Livestock in the Tropics. Longman LTD Group
Jensen, Rue and Briton Smith. 1982. Diseases of Sheep. Lea and Febiger.
Jordan, Anthony. 1986. Trypanosomaisis Control and African Rural Development. Longman LTD Group.
Losos, George. 1986. Infectious Tropical Diseases of Domestic Animals. Longman LTD Group.
Rieman, HP. and Burridge, MJ. 1984. Impact of Diseases on Livestock Production in the Tropics. Elsevier
 

ANNEX 1

Glossary

Anorexia loss of appetite for food

Antigen a foreign protein, usually a micro-organism, that stimulates production of blood antibodies against that protein

Anti-serum a serum that contains anti-bodies

Ascardiosis infestation with worms of the genus Ascaridia

Ataxia failure or irregularity of muscular co-ordination

Attenuated reduced in virulence, usually by passing the micro-organism through a succession of non-hosts

Avian of or pertaining to the husbandry of domesticated birds

Bovine of or pertaining to the husbandry of domesticated cattle

Buccal mucosae the mucose membranes lining the mouth

Caprine of or pertaining to the husbandry of domesticated goats

Choreic a convulsive nervous condition characterized by involuntary and irregular jerking movements

Conjunctiva the mucous membrane that lines the eyelids and covers the eyeball

Contagious the characteristic of being easily spread to other individuals

Dromedary of or pertaining to the husbandry of domesticated camels

Dyspnoea difficult or labored breathing

Epizootic an animal disease which is widespread or spreads rapidly

Equine of or pertaining to the husbandry of the domesticated horses, mules and donkeys

Hemoglobinuria a condition of blood in the urine causing a red to dark red color

Infectious the capability of an organism to invade the body

Keratitis-

conjunctivitis inflammation of the cornea and conjunctiva of the eye

Morbidity the diseased or the proportion of diseased animals

Mycoplasma bacteria that exhibit fungal-like growth characteristics

Osteomyelitis inflammation of the bone tissues which may include the marrow

Ovine of or pertaining to the husbandry of domesticated sheep

Pathogenic the capability of an organism to cause a disease

Serotypes distinctly different red blood cell clumping reactions as a result of the presence of different antibody

Stomatitis inflammation of the membrane lining the mouth

Toxemia death as a result of the production or ingestion of poisonous substances

Vaccine a suspension of killed or attenuated micro-organisms which upon injection stimulate the production of antibodies against a disease

Vector the intermediate host or carrier of a disease organism which in the process of transfer may or may not be affected

Vesicles a blister of the epidermis containing a clear fluid

Zoonosis or Zoonotic pertaining to a disease which can be transmitted between animals and man.