Endemic and Parasitic Diseases
of Smallstock

A disease is endemic when it occurs with predictable regularity in a population with only minor fluctuations in frequency pattern over time (Smith 1995). Alternatively, the term "endemic" may refer to "the constant presence of a disease in a population" (Thrusfield 1986). Major classes of endemic diseases affecting small ruminants in southern countries include those caused by both internal and external parasites as well as tick-borne and other arthropod-borne diseases (ticks, mites, and biting flies): Gastrointestinal Nematodes and Cestodes Lungworms Trematodes Diseases caused by Bacteria Mycoplasma Viruses Protozoa and Rickettsia Arthropods All of which are likely to be significantly influenced by lack of an adequate diet or by more serious malnutrition. See also: Zoonotic Diseases and: Major Epidemic Diseases

Internal Parasites of Sheep and Goats Internal Parasites of Poultry Parasite Resistance Alternative Control Strategies Internal Parasites    Roundworms or Nematodes    Trematode Worms or Flukes    Tapeworms (Cestodes)    Coccidia External Parasites:    Ticks    Mites    Biting flies    Fly maggots and Fly Strike Fungal diseases Viral diseases Bacterial diseases References and Further Reading

Gastrointestinal parasites in sheep and goats can, and in some circumstances do, cause severe losses. These range from decreased utilization of feeds to death. Good management practices, including prevention, control and treatment of gastrointestinal parasites, can prevent or reduce these losses.

Goats and sheep have numerous gastrointestinal parasites, many of which are shared by both species, as well as other ruminants. The most important include:

• Coccidia (a protozoan),
• Bacteria and viruses,
• Nematodes (roundworms),
• Cestodes (tapeworms),
• Trematodes (flukes).

Among the gastrointestinal parasites, nematodes present the greatest potential problems. The barberpole worm (Haemonchus contortus), is generally considered to the most important. Other species of nematodes occasionally cause economic loss to producers, but these are of generally less significance when compared to the potential damage caused by Haemonchus. In general, most approaches to control of these parasites apply equally well to the majority of gastrointestinal nematodes.

Nematodes or Roundworms

The most important nematodes of poultry are the Ascaridia, Heterakis and Capillaria species. They can either have a direct bird to bird life-cycle, with transmission by ingestion of infective eggs or larvae, or they may have an indirect cycle requiring an intermediate host. The Ascaridia, Heterakis and Capillaria species of nematodes are widely distributed, causing non-specific clinical signs of infection, such as loss in appetite and growth, a general loss in condition and occasionally death. Eggs laid by mature worms in infected birds are passed out in faeces. Once outside the body, the eggs undergo development either within an invertebrate host or in the soil. In the case of a direct life-cycle, birds become infected by eating embryonated eggs or the freed larvae. For those with an indirect life-cycle, an intermediate host such as a worm or insect ingests the eggs or free larvae. Birds then become infected when they consume a host containing an infective larvae. The life cycle of the different nematode species can last from days to months.

Cestodes and Trematodes

Cestodes and Trematodes are less pathogenic than the nematodes, but a large number have been identified with a wide range of hosts. The tapeworms require an intermediate host, such as earthworms or insects. The birds become infected through ingestion of the intermediate host. Trematodes tend to be more important parasites of wild water-fowl and domesticated ducks and geese.

Protozoans

One of the most important parasites of poultry are the protozoans causing Coccidiosis. This is caused by protozoan parasites, belonging to the genus Eimeria that live in the lining of the intestine. Both indoor and outdoor poultry management systems are at risk, but those that reply on intensive systems of production, with large numbers of birds in a small space are most at risk. Under such conditions serious infections can quickly build up. Typically, the disease is seen in birds of 3-6 weeks old, before they have acquired immunity.

For more on diseases in poultry

A major problem is the emergence of resistant strains of parasites. Resistance to all the major classes of anthelmintics has been reported. Where strains of parasites resistant to more than one drug exist, the options for treatment are seriously restricted. Hot countries where parasite turnover is high and anthelmintics are used often are, generally, worst affected (Wanyangu et al., 1996). Unfortunately new anthelmintics are costly and time consuming to develop. Careful management of the use of drugs is important. The correct dose for the animal should be administered as under-dosing tends to facilitate the emergence of resistance. Targeting of the animals that actually require treatment can help to reduce the selective pressure on the parasites to develop resistance. Easy to use tests such as the FAMACHA© system (Van Wyk et al. 1998) have been developed to aid the identification of animals that need to be dewormed.

Resistance is an inevitable consequence of the use of antiparasitic drugs (anthelminths, acaricides, insecticides) and there is substantial evidence that when a parasite has developed resistance to one drug it will usually also be resistant to other products from the same chemical group. Parasite resistance to drugs is an inherited phenomenon produced by selection pressure associated with the regular exposure to antiparasitic drugs.

A recent survey carried out by FAO and the Office Internationale des epizooties (OIE) in 77 out of 151 OIE member countries, revealed that over 50 per cent of countries are affected by parasite resistance. More than 20 percent of the countries reported having drug resistance problems in helminths and ticks. Today, the agricultural sector worldwide is facing up to the fact that all the economically important parasite species of livestock have somewhere developed resistance to the majority of the chemical groups available.

The false assumption that worm control is easy and could be accomplished only using drugs has significantly delayed the development of complementary and alternative strategies to control parasites. This is particularly relevant to smallholders and poor livestock farmers who are unlikely to be able to afford to implement chemical control methods, and certainly not on a regular basis.

In addition, there has in recent years been an increasing demand by consumers that agricultural products should be free from chemical contamination, and their potential effects on human health. The threat of adverse effects on the environment by the use of any chemicals in agricultural production has also driven this agenda.

Stakeholders in the agricultural sector such as farmers, the pharmaceutical industry, veterinarians, and extension personnel, realize that the time of easy parasite control, based only on the use of parasiticides is over. It is now essential to recognise that parasite control will have to rely on combinations of strategies and not just on chemical treatments.

Parasitic and other endemic diseases continue to be a major constraint on livestock production - both in intensive and extensive systems and in developed and developing countries alike. It is increasingly evident that the false assumption that parasite control is easily accomplished by the use of chemical means alone has lead to the development of parasite resistance. One of the results, quite apart from an increasing difficulty of parasite control is the creation of ecological imbalances and the build-up of chemical and drug residues in meat, milk and wool.

Integrated Parasite Control Methods (IPC or IPM) are required and these should be adopted from the outset in any farming system. Parasite control needs to move away from the reliance on chemical treatment only, to a more integrated and sustainable set of technologies. IPC is widely advocated - but what is it?

Integrated Parasite Control

Integrated Parasite Control (IPC) or Integrated Parasite Management (IPM) combine several control methods in order to slow or to prevent the development of drug resistant parasite populations. This can be achieved through good management of pastures, paying attention to the nutritional requirements of livestock, and careful management and use of anti-parasite drugs. An understanding of the life cycles and ecology of the parasites is an important part of this process. Components of IPC include:

• Good management and sanitation: clean grazing, clean feed, clean water
• Manage the natural resilience and parasite resistance within the herd or flock
• Pay attention to the seasonal nutritional requirements of stock
• Pay attention to alternative control strategies that may be applicable, and fine-tune these general strategies to the unique ecology, equipment availability and skills in the area.

For example, ewes require supplementation particularly in the latter stages of pregnancy, and if provided with adequate nutrition, including energy, protein, vitamins and minerals, will loose less condition than if not provided with supplements (see condition scoring). When individuals loose condition they are more susceptible to new parasite infections, and are less able to combat existing low-level infections.

For more information on Integrated Parasite Control see: Wells (1999).

Alternative methods of parasite control include:

	Use of genetically resistant breeds of livestock	As well as a combination of these different approaches, together with strategic use of chemical control
	Improved grazing management
	Alternative treatments, including the use of botanical dewormers
	Improved feeding and nutrition, especially increased levels of protein in the diet: Health-Nutrition interactions

Attempts have been made to develop alternative control strategies such as the use of genetic resistance. The red Masai sheep, for example, is noted for its resistance to worms (see Mugambi et al., 1997; Wanyangu et al. 1996). Other possibilities for control include improved grazing management to avoid infected pastures. This option is, however, difficult to implement where animals cannot be confined. Efforts have also been made to identify alternative treatment such those used in traditional livestock medicine. For instance, the use of Papaya extracts or seeds has been shown to have significant effects on control of nematodes in pigs and chickens (see Satrija 2001), whilst many species of Artemesia (wormwood) are effective against a variety of intestinal parasites.

Internal Parasites

For a comprehensive account of Helminth Parasites
of Small Ruminants in Sub-Saharan Africa see the work by
Kusiluka, L.J.M. and Kambarage, D.M. (1996).
Diseases of Small Ruminants in Sub-Saharan Africa: A Handbook.

Nematode worms are significant health problems for sheep and goats throughout the world. The impact is seen in a number of ways. Parasitism causes a reduction in food intake and lower weight gains. Milk production can also be affected, and heavily parasitised animals may die. The economic consequences for livestock keepers can therefore be serious (Hunter 1994; Hall, 1985; Kimberling; 1988).

It is necessary to understand the lifecycle of the parasites if they are to be controlled. Gastrointestinal nematodes produce eggs, which are passed in the faeces of sheep onto the pasture. The eggs hatch into larvae, which then develop to reach the infective stage. Grazing animals such as sheep and goats may ingest the larvae, which then mature into adult worms. The ability of nematode larvae to survive on the pasture is dependent on environmental conditions. Generally, warm and humid conditions are favourable to the parasites. However, the larva may go into a phase of hypobiosis or arrested development and may therefore survive when conditions are less favourable. The worms can, thus, be problem even in relatively arid environments.

A widely used measure to control nematode worms is to treat animals with anthelmintic drugs. These treatments can be effective, but there are a number of constraints to their successful use.

• It is important that treatments are given at the correct time and to the appropriate age groups.
• Lack of information on the lifecycle and epidemiology of the parasites can limit the effectiveness of control measures.
• Where livestock are free to roam and mix with other flocks, parasite control can be difficult to implement as pastures tend to become re-infected by untreated animals.
  

Another group of parasites are the trematode worms or flukes. Important parasites in this group include Fasciola spp. Infection leads to liver damage, anaemia and may lead to the death of the animal (Hunter, 1994). Understanding the lifecycle of the parasite is important for disease control. The eggs of the fluke are passed in the faeces of the infected animal. The larva, which emerges from the egg, is unable to survive unless it is able to penetrate its intermediate host, a particular species of snail. The larva further develops within the snail and later emerges and may be ingested by a grazing animal. The snails require damp conditions for survival.

Control strategies for flukes include the control of grazing to keep animals away from pools and marshy areas where the snails, which act as a host for the parasite are found. Drug treatments for liver flukes are also available.

	For more on Flukes and Fasciolosis, see:
	Pathogenesis and Epidemiology of Fasciolosis
	Using forecast models to control Fasciolosis in Nepal
	Interaction between Fasciolosis and nutrition in growing ruminants
	Feeding tree fodder to beat liver fluke

A variety of different species of tapeworm occur in different vertebrates. They all require a main, or definitive, host and an intermediate host in order to complete their life cycle. Domestic livestock may, depending on the species of tapeworm or cestode, be involved as either the definitive hosts, or as the intermediate hosts. In general, the more significant problems from cestodes in livestock are caused when they are involved as intermediate hosts - typically causing hydatidosis.

The tapeworm of sheep (Moniezia sp.) lives in the small intestine and is transmitted to sheep by soil mites that live in the pasture. Sheep are infected when they ingest the infected mites on grass. Although tapeworms are often accused of causing weight loss and/or diarrhoea, they normally do not cause much damage. In more extreme cases, tapeworm infestations can cause diarrhoea, weight loss, and even death. Moniezia adults can be extremely long - up to 6m in length may be found in the intestines of sheep, goats or cattle.

Tapeworm segments may commonly be seen in the faeces of young growing ruminants. In general these worms are not thought to cause much trouble to the animals, and by the time you actually see the segments, the livestock are beginning to develop their own immunity - causing the worms to be expelled.

Sheep and goats receiving a high quality feed or nutrition and/or with a higher body condition score are better able to withstand parasite challenges. Nutrition in early pregnancy increase fat stores and has been shown to increase the immune response to parasites. Ewes receiving increased protein levels during late gestation are better able to mount an immune response to parasites.

Break the Pork Tapeworm Cycle: Six Easy Steps

Hydatid Disease or Hydatidosis

Tapeworm cysts may also be seen in the internal organs of sheep and goats after slaughter. These are the cyst stages of tapeworms whose adult stages live in carnivores. The life cycle of Echinococcus granulosus for example includes dogs and other canines as the definitive host, and a variety of species of warm blooded vertebrates (sheep, cattle, goats, as well as humans) as the intermediate host.  The adult worms are very small, usually 3 to 6 mm, and live in the dog's small intestine.  Eggs are deposited with the dog's faeces. When these eggs are consumed by the intermediate host they hatch in the small intestine, then penetrate the gut wall and enter the circulatory system - and are then distributed throughout the body. Most end up in the liver and grow into a stage called a hydatid cyst, although this can grow anywhere in the body. These cysts can be quite large - cysts several inches in diameter are not uncommon. One or two small cysts in the liver of a host might go unnoticed for years.  However, a single large cyst in the liver could prove fatal. Hydatid disease is more serious when the cysts are found in other locations, particularly the brain.

The infection is transmitted to the definitive host when the hydatid cyst is eaten, for example by a dog. Echinococcus granulosus is more common in areas of the world where dogs are used to herd or guard sheep, or where suitable wild hosts are found. In some pastoralist groups, infections with E. granulosus is high. For example, the prevalence of E. granulosus in dogs in Turkana District of northern Kenya was found to be 39.4% (Macpherson et al., 1985).

There is no treatment for sheep or goats infected with hydatid cysts. In humans, surgical removal of cysts is the normal means of treatment.

Dogs can be treated with suitable anthelmintics. These may effective in removing the tapeworms, but provide no protection against reinfection. The activities of dogs should be controlled to help prevent transmission of the parasite. Measures to stop the dog–sheep cycle include:

• Preventing dogs from eating infected offal.
• Preventing infected dogs from defecating on pastures grazed by livestock.

For human protection, dogs should also be kept out of vegetable plots to prevent contamination of the vegetables by eggs from the dog's faeces.

For more on Hydatid Disease or Hydatidosis
Review of echinococcosis/hydatidosis: a zoonotic parasitic disease
See also: "Epidemiology and Control of Taenia saginata Cysticercosis"

Coccidiosis is caused by a group of protozoan parasites. Animals become infected after ingesting the oocyst (the egg) from the environment. Different species of the parasite may infect different livestock. For example, the coccidia infecting chickens are not thought to pass infections to sheep, and vice versa.

The symptoms of coccidiosis range from loss of appetite and slight, short-lived diarrhoea to severe cases involving great amounts of dark and bloody diarrhoea and, in some cases, death. The severity of symptoms depends upon the number of parasites invading the intestines. Faeces of sick animals contain many infective stages of coccidia. When an outbreak occurs, isolation and sanitation are key to preventing its spread throughout the herd or flock.

Healthy adult animals tend to have some immunity to coccidia. Similarly, local breeds are more likely to have some resistance than imported exotic breeds. The most susceptible animals are very young kids or lambs, and young that are being weaned. Adults can also develop coccidiosis if they are stressed or if they are moved into a new environment that is heavily infested with oocysts. Coccidiosis is also more of a problem in crowded conditions.

Treatment can be provided by a class of drugs called coccidiostats. These drugs tend to slow down the disease rather than kill all the coccidia, and they will also help reduce the number of oocysts that are being passed into the environment.

Understanding the life cycle of coccidia is an important step in learning what damage they do to the host. Coccidia are intercellular parasites. They live and grow within the cells lining the gastrointestinal tracts of the host. The oocyst is passed in the faeces of infected hosts. Oocysts then undergo a period of development, called sporulation, before being able to infect another host. This usually takes 2-3 days. Oxygen, moisture and warm temperatures are required for development. After sporulation occurs, the oocysts are very resistant to environmental conditions and ordinary disinfectants. Extremely dry weather and direct sunlight are the only environmental factors that are detrimental to sporulated oocysts. Moist areas out of direct sunlight (e.g. near water troughs) can harbour infective oocysts for a year or more. After a susceptible animal ingests a sporulated oocyst, infective spores are released and these enter the cells lining the intestine. In the intestine they go through several stages of development. The intestinal cells are destroyed and thousands of smaller coccidia are released. These smaller forms reinvade and damage other intestinal cells. Eventually sexual stages are reached and new oocysts are passed into the environment. The complete cycle usually takes about 2-3 weeks.

A major and important group of endemic diseases are the tick-borne diseases. Ticks cause problems for livestock through the direct effect of attachment, the injection of toxins, and the transmission of diseases.

Tick-borne diseases often inhibit the introduction of exotic or cross-bred livestock, which tend to be more susceptible to the diseases than are local breeds. Important tick-borne diseases of sheep and goats include Cowdriosis or Heartwater. This disease is caused by the rickettsial organism Cowdria ruminatium, which is spread by ticks of the genus Amblyomma. The disease is found in much of sub-Saharan Africa, Central and South America and the Caribbean. Severe cases of the disease can lead to the death of the affected animals. Another tick-borne disease, which affects small ruminants, is anaplasmosis. The disease is found in most sub-tropical and tropical regions as well as in some temperate regions. The disease is caused by rickettsial organisms of the genus Anaplasma, which are spread by a number of species of ticks.

Control of ticks and tick-borne diseases has traditionally been based on dipping of animals using acaricides. In many countries dipping services were provided by the state and were backed up by laws making dipping compulsory.

It is now considered that controlling ticks by intensive use of acaricides is no longer possible or desirable. Reasons include:

• the high costs of acaricides,
• the development of acaricide resistance in ticks,
• environmental concerns, and
• inappropriate use of acaricides can result in periodic disease outbreaks (see below)

Furthermore, the presence of infected ticks can lead to the emergence of a state known as "endemic stability", which is characterized by low levels of clinical disease due to resistance among the livestock population. Inappropriate use of acaricides can disrupt this balance and leave animals susceptible to disease - resulting in periodic outbreaks. Developing at strategy for the control of ticks and tick-borne diseases requires the consideration of a number of factors. These factors would include:

• the ecology of the tick vectors,
• the susceptibility of the livestock,
• feeding practices, and
• the extent to which acaricide is used, the economics of the local farming system, and
• the costs, availability and degree of uptake of various control measures.

A dip tank or spray-race requires considerable investment. Therefore, among small producers, hand spraying is often the method used if tick control is practiced. Another alternative is the pour-on. Acaricide is combined with solvents/propellants, which are poured onto the back or selected parts of the flanks of the animal, from where it disperses on the hair and skin. Ticks are only affected when they suck blood and therefore pour-ons are not effective against tick damage or against the rapid transmission of disease. Pour-ons are expensive, but have the advantage of not requiring much water or expensive equipment.

Chickens are natural predators of livestock ticks and that chickens can be used as part of an integrated tick control plan.

Chickens, when allowed free access to pastures, can eat a significant number of insects. Ticks tend to climb to the tops of grasses when waiting for a suitable host to appear. The larger ticks are easily eaten by chickens. Chickens can also be let into livestock holding pens where they will even remove ticks from livestock such as cows and goats, for example for a few hours during the milking period.

In a similar manner, Muscovy ducks will eat large numbers of flies, and can be an effective means of fly control.

Discussions with smallholder farmers in Western Kenya showed that they clearly recognised the value of freely ranging chickens for control of ticks. This means that their need to use expensive chemical control is greatly reduced. When chemical controls are needed, for example if cows or goats have tick infestations on their udders, farmers recognise that it is important to keep the chickens away from the livestock to stop them eating the ticks that are contaminated by the chemicals.

For more on the use of poultry for tick control
See also, the radio scripts from Developing Countries Farm Radio Network, on: Chickens eats ticks on cattle, and How Farmers use Biological Pest Control

Important external parasites of sheep and goats include the mites, which cause mange. These include the species Sarcoptes scabiei. Symptoms include severe itching, thickening of the skin, and hair loss. Severe weight loss and death may follow (Hall, 1985). Another parasite is Psoroptes ovis, which causes sheep scab or sheep mange, a serious condition mainly of wooled sheep, which causes lesions on the skin and the loss of wool. Control measures for external parasites include spraying or dipping with acaricides.

Blackflies or Simulium sp.

Blackflies, or flies belonging to the genus Simulium, have preferences for a wide range of different host species. Adult females of different Simulium species can feed on the blood of humans, cattle, horses, sheep, goats, poultry, other livestock as well as wild mammals and birds. Each different blackfly species will prefer one type of host and their common names sometimes indicates this host specificity, for example the turkey gnat in North America. Simulium feed during the daytime, preferring low wind conditions. They do not usually go indoors. They are attracted to their hosts from a distance by smell, by heat, and by sight. The female flies swarm around and then crawl on the host tending to prefer parts of the head and ears as well as any skin that is exposed.

Female Simulium are blood feeders whose bites can itch and persist for several days. The flies bite by cutting into the skin and feeding on the pool of blood that forms in the hole they make. Anticoagulants injected into the feeding site the flies can cause mild to severe allergic reactions in some individuals, both human and livestock.

Stomoxys species (Stable flies)

Sheep, goats and pigs can be attacked by Stomoxys flies which can cause considerable irritation amongst a herd. Both male and female Stomoxys feed on blood several times each day, taking one to two drops at each meal. Stamping of feet is a good indication that stable flies may be present since they normally attack an animal legs and bellies. Production performance declines in infested herds because of the painful bites and animal fatigue caused by attempts to dislodge or avoid flies.

Stomoxys breed in decaying vegetation, and the larvae tend to be found in manure, moist hay, and other damp and decaying vegetation. The cycle lasts for between 10 to about 20 days. Removing and spreading potential fly breeding materials on a weekly basis helps to break the cycle. Waste management is therefore the first line of defence in developing an effective fly management program. It is much easier and to prevent theses flies building up in number than attempt to control large fly populations once they have become established.

Nasal Bot flies (Oestrus ovis)

The larvae of a number of different species of fly live in or around the nose of mammals, including livestock. Oestrus avis, or the sheep nose boot fly, deposits living larvae (maggots) in or around the nostrils of the sheep. These are non-biting flies found in all places wherever sheep and goats are kept. When flies are attacking sheep, the animals bunch together and keep their noses to the ground in an effort to avoid the flies.

The larvae migrate through the nostrils into the head sinuses, or cavities in the horns or bones of the jaw or nose, where they feed on the internal secretions. Migration of the larvae irritates the nasal membranes and is often followed by secondary infections. When there are one or two larvae, they may pass out unnoticed with mild symptoms. Symptoms are dependent on the number of these larvae present in their nasal cavities. The common symptoms are sneezing, coughs and jerky movements of heads. Infested sheep shake their heads, stamp their feet, or hold their noses to the ground. Blood flecks in the nasal discharge, and sheep banging their heads against feed bunks, fences, or the ground indicate the presence of nose bots. Infected animals become inactive and do not feed well. There is a decrease in growth rate of the young and adults may loose weight. In heavier infestations animals may deteriorate and die.

The larvae are sneezed out or drop out to the ground, where they pupate and become adults. The Oestrus ovis pupae develop at shallow depths in the soil and the timing of emergence is directly dependent on climatic conditions, specifically the number of degree-days above a particular threshold soil temperature. Using temperature data derived from ground stations and from satellite imagery, the Directorate of Veterinary Services of the Ministry of Agriculture, Water and Rural Development of Namibia issues warnings to farmers in the south of the country about the likelihood of infestation of smallstock by Oestrus ovis. Farmers can then treat their stock at the most appropriate time. Treatment with a drench containing Ivermectin can be given to combat Oestrus ovis (Ivermectin is also effective against gastrointestinal parasites).

The main fungal disease of livestock is ringworm. This is caused by the fungus Trichophyton verrucosum, and has nothing to do with worms. The disease is transmitted in conditions of close contact between infected and susceptible animals. Often, the original source of infection is found to be from an animal that was purchased or brought in from elsewhere. The ringworm fungus can also infect humans and a wide range of other animal species, and so can also be spread to domestic stock by contact in this way. Geographic distribution is world-wide.

The fungal infection starts as an area of small scales or crusts on the skin. The hair falls out and the area expands outwards, resulting in a characteristic ring-shaped patch.

Also of importance are the fungal infections of livestock feed, commonly called moulds. Moulds may grow on feed (either in the standing crop or, more usually, during storage). The fungal spores that are produced when the mould reproduces may be ingested or inhaled by the animal and this may itself be harmful. Many fungi, however, also produce secondary compounds called mycotoxins.

For more on moulds and Mycotoxins

For information on diseases caused by viruses see Chapter 5 in Kusiluka and Kambarage (1996)

Enterotoxaemia, or Clostridial diseases

Enterotoxaemia is caused by a bacterium called Clostridium perfringens. It normally inhabits the lower digestive tract and causes no harm to the animal. Clostridium perfringens thrives on starch and sugars that are normally digested and metabolized higher in the digestive tract. When a lamb overeats, undigested starch and other carbohydrates provide a medium that allows Clostridium perfringens to proliferate. It also enhances the organism’s ability to produce a number of very potent toxins that are released into the intestinal tract and then absorbed into the animal's system. The result is the sudden death associated with this disease. Vigorous, healthy, rapidly growing lambs are particularly susceptible to enterotoxaemia.

For more information on Clostridial diseases

For more information on diseases caused by bacteria see Chapter 3 in Kusiluka and Kambarage (1996)

FAO. (2002). Biological control of nematode parasites of small ruminants in Asia. Final Proceedings of FAO Technical Co-operation Project in Malaysia TCP/MAL/0065 (T) 2002. FAO Animal Production and Health Paper.

Satrija, F., Retnani, E.B., Ridwan, Y. and Tiuria, R. (2001). Potential Use of Herbal Anthelmintics as Alternative Antiparasitic Drugs for Small Holder Farms in Developing Countries. Livestock Community and Environment. Proceedings of the 10th Conference of the Association of Institutions for Tropical Veterinary Medicine, Copenhagen, Denmark, 2001