Various disease problems in small ruminants influenced by Management Systems. Small ruminant management can be grouped into two broad categories, that is, traditional and modern systems. The traditional management systems can be further subdivided into groups namely, the extensive, semi-intensive and intensive systems.
The extensive system
This system is common in arid and semi-arid areas receiving rainfall below 700 mm per annum and because of the unreliability of rainfall, crop agriculture is restricted to irrigated areas where only drought resistant crops such as millet, sorghum and cassava can be grown. Forage and water sources for the animals in these areas are scarce and subsistence is mainly derived from livestock use, sale or exchange.
This system is common in arid and semi-arid areas receiving rainfall below 700 mm per annum and because of the unreliability of rainfall, crop agriculture is restricted to irrigated areas where only drought resistant crops such as millet, sorghum and cassava can be grown. Forage and water sources for the animals in these areas are scarce and subsistence is mainly derived from livestock use, sale or exchange.
Two sub-systems, nomadism and transhumance are found under the extensive system of management. In the nomadic system, people and animals are constantly moving in search of pasture and water or to avoid disease epidemics and tribal conflicts. Subsistence is based wholly on animals. Under the extensive system, animals graze on communal land and, animal herds owned by different families or individuals compete for grazing and water. Often, herds of cattle, small ruminants and camels graze together. At night, animals are protected from theft and/or predation by confinement in night enclosures which are constructed using thorn bushes or wooden poles depending on the availability of these materials. The only human input into this system is the unpaid family labour used to look for the animals and the main management objective is to avoid risks of diseases, drought and to maintain herd numbers. There is no controlled breeding, supplementary feeding or veterinary care for the animals except where governments are developing veterinary extension services to encourage settlement of pastoral communities. The marketing infrastructure for animals is also underdeveloped. Because of shortage of water and forage, malnutrition is the major limiting factor for profitable production of small ruminants particularly during the dry season.
The semi-intensive system
This system is common in areas where the annual rainfall is more than 1000 mm and therefore suitable for crop cultivation. Thus, subsistence is gained mainly from crops and, small ruminants are kept as an insurance against crop failures and as a source of income. Under this system, between 10 and 50 percent of household
revenue is derived from livestock or livestock products and, in years of drought they may be the only means of subsistence.
Livestock are sedentary, although movement of animals for a short-distance is not uncommon. Most commonly, animals are grazed for a restricted period of time, usually late morning or late evening, depending on the availability of labour and feed. Herding is practised to control grazing, protect animals from raiders and
predators. Herders also assist diseased animals and collect newly born kids. Small ruminants complement crop production by utilising crop residues and by-products while their manure fertilises lands.
Supplementary feeding of the animals with crop residues and household wastes such as cassava and banana peelings or vegetables is sometimes practised and at night, animals are confined in enclosures close to the owner's house. The night enclosures are similar to those observed under the extensive system. Sometimes animals are just tied to pegs around the owner's house. There is minimal control of breeding and veterinary care. Under the semi-intensive system, since most of the land is utilised for crop production, land available for animals is limited. As a result, herd sizes are smaller than in the extensive system.
predators. Herders also assist diseased animals and collect newly born kids. Small ruminants complement crop production by utilising crop residues and by-products while their manure fertilises lands.
Supplementary feeding of the animals with crop residues and household wastes such as cassava and banana peelings or vegetables is sometimes practised and at night, animals are confined in enclosures close to the owner's house. The night enclosures are similar to those observed under the extensive system. Sometimes animals are just tied to pegs around the owner's house. There is minimal control of breeding and veterinary care. Under the semi-intensive system, since most of the land is utilised for crop production, land available for animals is limited. As a result, herd sizes are smaller than in the extensive system.
The intensive system
This system is common in areas with high population density and intense agricultural activity. Land scarcity and labour shortages are the major limiting factors to small ruminant production. Four feeding systems are found within this system; tethering, stall-feeding, intensive use of cultivated forages/pastures and integration with tree crops.
Modern small ruminant production
This systems require a high capital investment.Animals are either stall-fed or grazed on improved pastures during the day and are housed at night. Supplementary feeds such as concentrates are often provided. Most commonly small ruminants are integrated with dairy, beef and sometimes large scale crop farming. Because animals are raised for commercial purposes, modern animal husbandry practices are employed
and the productivity of animals under this system is generally high.
However, considerable economic losses may be encountered under this system if husbandry practices are poor. Disease such as helminthosis, coccidiosis, clostridial enterotoxaemias and pneumonia are frequently encountered under this system causing tremendous losses. Close confinement is very favourable for cross-transmission of diseases.
It follows from the above section that, the prevalence of various disease problems in small ruminants are influenced by management systems. Therefore, any disease control programmes in an area should be formulated with due consideration of the management systems. Most diseases of livestock can be controlled by proper management.
Various disease problems in small ruminants caused by Helminthosis, Bacteria, Mycoplasma, Viruses, Protozoa and Ricketsia, and Arthropods.
This system is common in areas with high population density and intense agricultural activity. Land scarcity and labour shortages are the major limiting factors to small ruminant production. Four feeding systems are found within this system; tethering, stall-feeding, intensive use of cultivated forages/pastures and integration with tree crops.
Modern small ruminant production
This systems require a high capital investment.Animals are either stall-fed or grazed on improved pastures during the day and are housed at night. Supplementary feeds such as concentrates are often provided. Most commonly small ruminants are integrated with dairy, beef and sometimes large scale crop farming. Because animals are raised for commercial purposes, modern animal husbandry practices are employed
and the productivity of animals under this system is generally high.
However, considerable economic losses may be encountered under this system if husbandry practices are poor. Disease such as helminthosis, coccidiosis, clostridial enterotoxaemias and pneumonia are frequently encountered under this system causing tremendous losses. Close confinement is very favourable for cross-transmission of diseases.
It follows from the above section that, the prevalence of various disease problems in small ruminants are influenced by management systems. Therefore, any disease control programmes in an area should be formulated with due consideration of the management systems. Most diseases of livestock can be controlled by proper management.
Various disease problems in small ruminants caused by Helminthosis, Bacteria, Mycoplasma, Viruses, Protozoa and Ricketsia, and Arthropods.
Helminths cause direct losses due to deaths and indirect losses due to reduced productivity through reduced feed intake and liveweight gains and, decreased quality of skins, wool or mohair. Furthermore, they render animals more susceptible to other infections. Diagnosis of helminthosis is based on history, epidemiological, clinical and pathological findings and laboratory analysis of appropriate samples. The most commonly used laboratory methods for diagnosis of gastrointestinal nematodes are faecal egg counts, faecal cultures, determination of infective larvae on herbage and worm counts at post mortem. The control of helminthosis is designed to eliminate or reduce the prevalence of helminths and improve the productivity of the livestock industry. The eradication of helminthosis in animals is difficult and the aim of control is therefore to limit the infection by minimising the challenge to an economically justifiable level. It is therefore important to accurately assess the cost-benefit effectiveness of any helminth control programme if production from the animals is to be optimised. Effective control of helminthoses can be achieved by judicious use of anthelmintics and good management. Many anthelmintics which are effective against different species of helminths affecting small ruminants have been developed. Benzimidazoles, imidazothiazoles, tretrahydropyrimidines, organophosphates and ivermectins form the major classes of anthelmintics.
The most common bacterial diseases affecting small ruminants are pneumonia, brucellosis, footrot, dermatophilosis, caseous lymphadenitis, anthrax and clostridial infections such as blackquarter, tetanus, malignant oedema and enterotoxaemias. Colibacillosis and salmonellosis are also encountered particularly under the intensive production systems.
The major syndrome associated with Mycoplasma spp infection in small ruminants is pneumonia. However, Mycoplasma spp do cause other disease syndromes such as polyarthritis and mastitis. Many species of Mycoplasma are involved in the pathogenesis of pneumonic syndromes in small ruminants. The common species include Mycoplasma mycoides subspecies mycoides (large colony type), Mycoplasma mycoides subspecies capri, Mycoplasma arginini, Mycoplasma ovipneumoniae, Mycoplasma agalactiae and Mycoplasma capricolum. Contagious caprine pleuropneumonia (CCPP) is a distinct disease entity caused by Mycoplasma biotype F 38. Mycoplasma mycoides subspecies capri is also still being considered as a cause of a mild form of CCPP. The pathogenesis of mycoplasmal pneumonia is similar to pneumonic pasteurellosis, as so are the clinical signs and pathological features. The incubation period may be as short as 3-6 days or as long as 3-4 weeks in natural field infections. CCPP is a highly contagious disease of goats and it is characterised by depression, fever (41.6-41.7°C), anorexia, dyspnoea, coughing, abdominal respiration, reluctance to move, bleating, extension of the neck, frothy or mucopurulent nasal discharges and subcutaneous oedema on the chest and abdomen. Stringy salivation may be observed before death. Death may occur within 2 days of the onset of the clinical signs. Tylosin (11 mg/kg) is effective in the treatment of CCPP when used in early stages of the disease. Oxytetracycline (15 mg/kg), tiamulin, chloramphenicol and penicillinstreptomycin can also be used. Separation and treatment of the affected animals will minimise the spread of the disease. Susceptible naive animals should be vaccinated before being moved to endemic areas. A saponified inactivated Mycoplasma strain F 38 vaccine has been found to be effective in the control of the disease.
The common viral infections of goats and sheep are peste des petits ruminants (PPR), contagious ecthyma, goat/sheep pox and Nairobi sheep disease. Other viral diseases are Rift Valley fever and blue tongue.
Coccidiosis and trypanosomosis are the clinically and economically most important protozoan diseases of goats and sheep. Toxoplasmosis is associated with reproductive wastage in small ruminants but the extent of the problem and the economic significance in the sub-Saharan region is not well documented. Babesia spp infection in goats and sheep is an inapparent infection but it may cause a mild or serious disease in exotic or immunosuppressed animals. This is an enteric disease affecting particularly kids and lambs and it is characterised by debility, malaise, inappetance, diarrhoea or sometimes dysentery, dehydration and death in untreated animals. Coccidiosis in goats and sheep is caused by protozoa of the genus Eimeria. The common species of Eimeria affecting goats in sub-Saharan countries are E. alijevi, E. arloingi, E. ninakohlyakimovae and E. christenseni. Other species are E. hirci, E. caprovina, E. jolchijevi and E. aspheronica. E. arloingi, E. christenseni and E. ninakohylakimovae are considered to be the most pathogenic species of Eimeria in goats. The species affecting sheep include E. crandallis, E. ahsata, E. faurei, E. intricata and E. ovina. Other species are E. ovinoidalis, E. pallida and E. parva. E. ovinoidalis, E. crandallis, E. ovina and E. ahsata are known to be pathogenic in sheep. Diarrhoea which may be mucoid or bloody, abdominal pain, tenesmus, inappetence, debility, loss of weight and dehydration are the common features associated with coccidiosis. Anaemia may also be encountered. In the acute disease, there may be fever, ocular and nasal discharges. Subclinical coccidiosis is associated with reduced feed intake, poor weight gains and poor food utilisation. Coccidiosis is self-limiting, however, other enteropathogens can complicate the clinical picture. Exposure to lowgrade challenge results in development of strong immunity against the disease. Successive infections in young animals may cause animals to excrete large numbers of oocysts with subsequent heavy contamination of houses, pastures or watering places. Coccidiosis can be treated using decoquinate (0.5 mg/kg) and lasolacid at a daily
intake of 4.3 mg/kg body weight. Sulphonamides such as sulphadimidine, sulphamerazine, sulphamethazine and sulphaquinoxaline at dosage rates of 50-100 mg/kg for 4 days are effective against coccidiosis in small ruminants. Amprolium in feed is also used to treat the disease in goats (100 mg/kg) and sheep (50 mg/kg). Nitrofurazone given orally (10-20 mg/kg) is also effective. Other drugs include monensin (20 g/ton of feed), toltrazuril and dicrlazuril. Coccidiostats in drinking water or feed are commonly employed to control the disease in intensive production systems. Decoquinate (0.3 -4.0 mg/kg) in feed mixtures is a safe and very effective coccidiostat in goats and sheep. Monensin fed prophylactically at 10-30 mg per ton of feed controls shedding of oocysts and increases feed conversion. However, high levels of monensin render the feed unpalatable and toxic. Proper hygiene in the house and minimisation of predisposing factors are important factors to be considered in the control strategies of coccidiosis. Provision of adequate nutrition enhances the resistance of animals to coccidiosis.
Ectoparasites are not associated with heavy mortalities in small ruminants but they are important causes of unthriftiness and loss of production in affected animals. The common ectoparasites of veterinary importance are mange mites, fleas, lice, ticks and Oestrus ovis.
The most common bacterial diseases affecting small ruminants are pneumonia, brucellosis, footrot, dermatophilosis, caseous lymphadenitis, anthrax and clostridial infections such as blackquarter, tetanus, malignant oedema and enterotoxaemias. Colibacillosis and salmonellosis are also encountered particularly under the intensive production systems.
The major syndrome associated with Mycoplasma spp infection in small ruminants is pneumonia. However, Mycoplasma spp do cause other disease syndromes such as polyarthritis and mastitis. Many species of Mycoplasma are involved in the pathogenesis of pneumonic syndromes in small ruminants. The common species include Mycoplasma mycoides subspecies mycoides (large colony type), Mycoplasma mycoides subspecies capri, Mycoplasma arginini, Mycoplasma ovipneumoniae, Mycoplasma agalactiae and Mycoplasma capricolum. Contagious caprine pleuropneumonia (CCPP) is a distinct disease entity caused by Mycoplasma biotype F 38. Mycoplasma mycoides subspecies capri is also still being considered as a cause of a mild form of CCPP. The pathogenesis of mycoplasmal pneumonia is similar to pneumonic pasteurellosis, as so are the clinical signs and pathological features. The incubation period may be as short as 3-6 days or as long as 3-4 weeks in natural field infections. CCPP is a highly contagious disease of goats and it is characterised by depression, fever (41.6-41.7°C), anorexia, dyspnoea, coughing, abdominal respiration, reluctance to move, bleating, extension of the neck, frothy or mucopurulent nasal discharges and subcutaneous oedema on the chest and abdomen. Stringy salivation may be observed before death. Death may occur within 2 days of the onset of the clinical signs. Tylosin (11 mg/kg) is effective in the treatment of CCPP when used in early stages of the disease. Oxytetracycline (15 mg/kg), tiamulin, chloramphenicol and penicillinstreptomycin can also be used. Separation and treatment of the affected animals will minimise the spread of the disease. Susceptible naive animals should be vaccinated before being moved to endemic areas. A saponified inactivated Mycoplasma strain F 38 vaccine has been found to be effective in the control of the disease.
The common viral infections of goats and sheep are peste des petits ruminants (PPR), contagious ecthyma, goat/sheep pox and Nairobi sheep disease. Other viral diseases are Rift Valley fever and blue tongue.
Coccidiosis and trypanosomosis are the clinically and economically most important protozoan diseases of goats and sheep. Toxoplasmosis is associated with reproductive wastage in small ruminants but the extent of the problem and the economic significance in the sub-Saharan region is not well documented. Babesia spp infection in goats and sheep is an inapparent infection but it may cause a mild or serious disease in exotic or immunosuppressed animals. This is an enteric disease affecting particularly kids and lambs and it is characterised by debility, malaise, inappetance, diarrhoea or sometimes dysentery, dehydration and death in untreated animals. Coccidiosis in goats and sheep is caused by protozoa of the genus Eimeria. The common species of Eimeria affecting goats in sub-Saharan countries are E. alijevi, E. arloingi, E. ninakohlyakimovae and E. christenseni. Other species are E. hirci, E. caprovina, E. jolchijevi and E. aspheronica. E. arloingi, E. christenseni and E. ninakohylakimovae are considered to be the most pathogenic species of Eimeria in goats. The species affecting sheep include E. crandallis, E. ahsata, E. faurei, E. intricata and E. ovina. Other species are E. ovinoidalis, E. pallida and E. parva. E. ovinoidalis, E. crandallis, E. ovina and E. ahsata are known to be pathogenic in sheep. Diarrhoea which may be mucoid or bloody, abdominal pain, tenesmus, inappetence, debility, loss of weight and dehydration are the common features associated with coccidiosis. Anaemia may also be encountered. In the acute disease, there may be fever, ocular and nasal discharges. Subclinical coccidiosis is associated with reduced feed intake, poor weight gains and poor food utilisation. Coccidiosis is self-limiting, however, other enteropathogens can complicate the clinical picture. Exposure to lowgrade challenge results in development of strong immunity against the disease. Successive infections in young animals may cause animals to excrete large numbers of oocysts with subsequent heavy contamination of houses, pastures or watering places. Coccidiosis can be treated using decoquinate (0.5 mg/kg) and lasolacid at a daily
intake of 4.3 mg/kg body weight. Sulphonamides such as sulphadimidine, sulphamerazine, sulphamethazine and sulphaquinoxaline at dosage rates of 50-100 mg/kg for 4 days are effective against coccidiosis in small ruminants. Amprolium in feed is also used to treat the disease in goats (100 mg/kg) and sheep (50 mg/kg). Nitrofurazone given orally (10-20 mg/kg) is also effective. Other drugs include monensin (20 g/ton of feed), toltrazuril and dicrlazuril. Coccidiostats in drinking water or feed are commonly employed to control the disease in intensive production systems. Decoquinate (0.3 -4.0 mg/kg) in feed mixtures is a safe and very effective coccidiostat in goats and sheep. Monensin fed prophylactically at 10-30 mg per ton of feed controls shedding of oocysts and increases feed conversion. However, high levels of monensin render the feed unpalatable and toxic. Proper hygiene in the house and minimisation of predisposing factors are important factors to be considered in the control strategies of coccidiosis. Provision of adequate nutrition enhances the resistance of animals to coccidiosis.
Ectoparasites are not associated with heavy mortalities in small ruminants but they are important causes of unthriftiness and loss of production in affected animals. The common ectoparasites of veterinary importance are mange mites, fleas, lice, ticks and Oestrus ovis.
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