key: cord-0040204-si0wkcb3
authors: Bruning-Fann, C.; Balander, R.; Garling, D.L.; Kopcha, M.
title: INFECTIOUS DISEASES OF MEAT ANIMALS | Production Diseases
date: 2004-11-28
journal: Encyclopedia of Meat Sciences
DOI: 10.1016/b0-12-464970-x/00025-8
sha: d0c2ac63240ec41899b1dd80e399ffb47a04be3a
doc_id: 40204
cord_uid: si0wkcb3

nan

Diseases that affect the health and productivity of food animals directly impact the cost and supply of high-quality protein available for human consumption. In addition to the expense resulting from animal treatments and deaths, diseases also cause economic losses by decreasing meat, milk or egg production, reducing feed conversion, slowing weight gain, and increasing the time the animal must remain on the farm prior to marketing. This article will briefly discuss many of the important diseases that affect the production of livestock, poultry and fish for meat. It is worth noting that a number of diseases included in this article are notifiable and/or zoonotic (discussed in greater detail in Infectious diseases of meat animals:

Notifiable and zoonotic diseases). A good review of the use of antibiotics for the treatment of infections diseases can be found in Antibiotics: Use in animal husbandry.

Diseases of importance to ruminants and swine are listed in Table 1 , while Table 2 lists diseases that are of importance for poultry.

Actinobacillosis is characterized by firm, nodular swellings of the tongue, head and other tissues. Losses associated with this infection are due to incapacitation of the affected animal and condemnation of affected tissue.

Actinomycosis most often causes a slow-growing swelling on the jaw. Incapacitation of the affected animal and condemnation of affected tissue result.

The course of illness can range from chronic to peracute, with animals exhibiting clinical signs related to anaemia (icterus, depression, inappetence, fever, weight loss, decreased milk production, death). On necropsy, the blood is watery and icterus can be prominent.

Anthrax affects an extremely wide range of mammals, including humans. The clinical course ranges from chronic to peracute (death with few if any clinical signs). Acutely affected animals develop high fever, depression, respiratory and/or cardiac distress, convulsions, bloody discharges from body openings and death. Cases that are more chronic may develop oedema in the ventral portions of the head, neck, thorax and abdomen. Anthrax should be considered whenever there is a carcass in which the blood fails to clot and rigor mortis does not occur. Upon necropsy, enlarged spleens and lesions consistent with septicaemia are seen.

This disease is characterized by atrophy of the nasal turbinates of swine, which in moderate to severe cases causes distortion of the snout. Development of the disease is related to infection with Bordetella bronchiseptica and Pasteurella multocida in addition to environmental and management factors. Economic losses can be severe as affected animals consume less feed, leading to a slower rate of weight gain and stunting. Atrophic rhinitis is widespread in the swine industry of many countries. Aujeszky's disease affects a wide range of animals with the infection resulting in death in all species but swine. With swine, clinical signs can vary from inapparent infection to death, depending on the state of immunity, age of the animals and the strain of the virus. Clinical signs in young pigs are fever, inappetence and depression, followed by trembling, incoordination, convulsions, coma and death. Sows frequently exhibit increases in abortion, stillbirths and/or mummies. The course of this disease in all other species is short (<48 h) and begins with a brief excitement phase characterized by trembling, anxiety and aggressive behaviour. This is followed by intense pruritis and culminates with incoordination, convulsions, coma and death.

Avian Chlamydiosis is a systemic and occasionally fatal disease of most birds caused by several different strains of Chlamydia psittici. The lungs of affected birds are diffusely congested. The thoracic and peritonial cavities show fibrinous exudates. The pericardial and air sacs are thickened and covered by fibrinous exudates. The heart may be enlarged with fibrin plaques or yellowish flakey exudate on the surface. The liver and spleen are frequently enlarged and discoloured.

Avian infectious bronchitis is an acute, highly contagious respiratory disease associated with coughing, sneezing and tracheal rales. Gross lesions include a serous, catarrhal or caseous exudate in the trachea, nasal passages, sinuses and air sacs. Laying chickens frequently exhibit fluid yolk material in the abdominal cavity. Egg quality is severely affected in recovered birds.

There are a number of distinct avian pox viruses, which vary in their species specificity and pathogenicity. Pox lesions typically affect the non-feathered areas of the bird. Diphtheritic lesions of the oral cavity and oesophagus and/or infection of the nasal cavities may also be present. There are no internal lesions.

This disease is named for the emphysematous swelling most often seen in the large muscles of cattle and sheep. The affected muscle is dark, dry and spongy in appearance with a sweet smell. Blackleg usually develops in beef breed animals in excellent health and weight.

This viral disease of ruminants, especially sheep, is spread by biting insects (Culicoides spp.). Clinical signs include fever, listlessness, reddening of the face, and erosion, ulceration and necrosis of the mouth. Swelling and cyanosis of the tongue may be seen along with lameness, conjunctivitis and pneumonia.

Botulism is caused by a toxin produced by the bacteria Clostridium botulinum. A wide variety of species are affected including livestock, poultry and humans. This disease manifests as an ascending muscle paralysis with death occurring due to respiratory or cardiac paralysis. More information on Clostridium botulinum can be found in Microbiological safety of meat: Clostridium botulinum.

Clinical signs are variable and include fever, inappetence, lethargy, diarrhoea, dehydration, purulent nasal discharge, oral erosions, respiratory signs and corneal opacity. Erosions may occur on the coronary band and interdigital spaces of the foot, causing lameness. Gross lesions may include erosions with little evidence of inflammation in the mouth, pharynx, oesophagus, stomachs, caecum and small intestine.

Several species of Brucella cause illness in ruminants, swine, and humans. Clinical signs include fever, abortion, stillbirths and retained placentas. Humans may be infected through handling infected tissue or consumption of milk from infected animals.

Campylobacter cause diarrhoea in a variety of animals, with younger animals most severely affected. The prevalence of this disease has been increasing in both animals and humans in recent years. More information on Campylobacter spp. can be found in Microbiological safety of meat: Thermotolerant Campylobacter.

This chronic disease primarily affecting sheep and goats is characterized by caseous abscesses of the lymph nodes, lungs and other organs. Economic losses result from decreased weight gain and productivity, condemnation of tissues or the whole carcass and decreased value of the hide as abscesses rupture to the outside.

Clostridium perfringens causes enteritis, dysentery, toxaemia and death in cattle, sheep, swine, goats and deer. Further discussion of Clostridium perfringens can be found in Microbiological safety of meat: Clostridium perfringens.

Various genera of coccidia affect a wide variety of animals. Clinical signs range from inapparent infection to depression, weight loss, haemorrhagic diarrhoea and death. In general, young animals are the most severely affected. In poultry, lesions may be seen upon careful examination of the intestinal tract, where thickening of the wall and whitish plaques or cysts may be seen.

Clinical signs of this disease vary with the age and species of waterfowl infected and vary from listlessness, inappetence, nasal discharge, ataxia, decreased production and diarrhoea to acute death. In general, haemorrhages can be found in the intestines, liver, pancreas, kidneys and lungs. The lumens of the intestine and ventriculus (gizzard) are frequently blood-filled.

Although erysipelas can affect a number of species, it is usually of significance only in swine, turkeys and humans. Swine suffer septicaemia and skin lesions. The disease can range from chronic to acute or may be inapparent. Clinical signs include fever, listlessness, inappetence, painful lameness and, in pregnant sows, abortion. Raised, firm, discoloured (pink to purple), urticarial (frequently diamond-shaped) skin lesions are characteristic. In turkeys, erysipelas is associated with death and male sterility. Clinical signs include listlessness, ataxia, weight loss, skin and snood lesions and death. Gross lesions in turkeys are related to septicaemia. In humans, erysipelas causes a local skin lesion and is associated with the handling of live swine and turkeys and the processing of meat, poultry or fish (where it is a contaminant).

The course of this disease is most often acute and fatal. Affected birds display fever, anorexia, depression, mucoid oral discharge, diarrhoea and respiratory distress. Acute death without any previously noted clinical signs is common. Lesions are associated with vascular disturbances. Frequently, congestion and haemorrhages are seen in the intestine, with increased levels of peritoneal and pericardial fluids. The liver may be swollen with many small areas of necrosis. In turkeys, pneumonia is common.

Clinical signs vary greatly with this disease depending on the strain of organism and age of the affected animal. Feedlot animals generally develop high fever, inappetence, lethargy, respiratory signs, nasal reddening and discharge, conjunctivitis and papules or ulcers on the nasal mucosa. Breeding animals can abort or develop inflammation, pustules, erosions and ulcers on the prepuce and penis of males and the vulva and vagina of females. Young animals frequently develop fever, ocular and nasal discharges, respiratory signs, diarrhoea and encephalitis. Lesions also vary and may include inflammation, haemorrhage and necrotic foci in the respiratory tract, bronchopneumonia and erosions or ulcers in the nasal passages.

This subacute or acute respiratory disease affects primarily chickens, causing depression, sneezing, rales, nasal discharge, and swelling under the eyes that may extend to all of the face and wattles. Egg production is greatly curtailed. Gross lesions consist of sinusitis and may include conjunctivitis, tracheitis, bronchitis and airsacculitis.

Infection with type A influenza viruses is a problem for swine, poultry and humans. This disease is characterized by a sudden onset of fever, coughing, sneezing, respiratory distress and listlessness, with the affected animals either recovering or dying, quickly. Gross lesions in poultry include sinusitis, periocular oedema and cyanosis, diphtheritic plaques in the trachea, and haemorrhages in the proventriculus, small intestine and cloaca. Economic losses are incurred through loss of weight during illness, reproductive problems (abortions in swine; loss of egg production in poultry) and deaths. Poultry, especially chickens, have suffered far greater losses than swine.

In recent years, this disease has taken on additional significance as it has become apparent that poultry and swine play an important role in the reassortment of genetic material and the development of influenza strains that affect humans.

Clinical disease is rarely seen in young animals. Affected animals show progressive weight loss leading to emaciation and death. The weight loss caused by the accordian-like, corrugated thickening of the intestinal wall and mucosa is accompanied by a profuse diarrhoea. This disease in goats has a somewhat different appearance as usually only a focal or diffuse thickening of intestinal walls is seen. Diarrhoea is rare in goats. Losses occur through decreased productivity and the eventual death of affected animals.

This acute upper respiratory disease of chickens is characterized by nasal discharge, gasping, coughing with expulsion of bloody exudates, respiratory distress and death. The trachea and larynx are inflamed and oedematous. In more severe cases, there is haemorrhage and necrosis of the trachea and larynx. Inflammation may extend to the bronchi, lungs and air sacs.

Leptospira are in the tissues and urine of infected animals and can survive for months outside a host. Infection occurs in animals and humans when the agent contacts abraded skin or the mucous membranes of the mouth, nose or eye. Clinical signs include fever, anaemia, icterus, blood in the urine, abortion and, occasionally, death. Chronically infected animals may show no signs other than slow weight gain. Gross lesions include haemorrhages on the surface of the abdominal organs, heart and lungs.

Listeria affects a wide range of animals, most often cattle and sheep. Neurological disturbances, most notably walking in a circle, but also abortions, septicaemia and death, may be seen with this disease. More information on Listeria monocytogenes, the causative agent of this disease, can be found in Microbiological safety of meat: Listeria monocytogenes.

Whitish nodules in the bursa, liver, spleen, kidney, and occasionally in the heart, gonads and pancreas, are typically seen with this disease. These nodules grossly resemble those seen with Marek's disease, although lesions seldom are seen in birds <16 weeks of age, whereas Marek's can affect birds as young as 3-4 weeks old.

Lymphosarcoma is caused by a virus in cattle, while the cause in other species is unknown. Clinical signs of lymphosarcoma include greatly enlarged lymph nodes that bulge from the cut surface.

This disease can be caused by two or more different alcelaphine herpes viruses (AHV).This disease primarily affects cattle and deer that are exposed to either sheep (AHV-2) or wildebeests (AHV-1) that carry the infective agent. Infected cattle and deer develop a high fever, depression, swollen lymph nodes, serous discharges from the eyes and nose, erosions in the mouth, diarrhoea and death. Lesions include necrosis of the epithelium of the gastrointestinal, respiratory and/or urinary tracts.

Malignant oedema results from contaminating a wound with a Clostridium sp., most commonly Cl. septicum. A soft, oedematous, rapidly growing swelling develops at the injury site. The muscle in affected areas is dark brown to black (similar to blackleg). High fever, anorexia and muscle tremor precede death.

Chickens are the only important natural host of Marek's disease. Enlargement of peripheral nerves, especially the vagus, brachial and sciatic, is diagnostic for this lymphoproliferative disease. Paralysis of areas innervated by the affected nerves is common. Also seen are whitish nodules involving the thoracic and abdominal organs, enlarged feather follicles and a blue or grey discoloration of the iris.

This acute respiratory disease affects a wide range of avian species. Clinical signs and lesions depend on the age and species affected and the strain of the virus. Severity of disease ranges from inapparent infection to acute death. Affected animals may display gastrointestinal, respiratory and/or nervous system signs. Clinical signs may include depression, diarrhoea, respiratory distress, paralysis, twisting of the neck, head thrown back, swelling of the head and death. Gross lesions are variable and may include haemorrhages and necrosis of the intestine, tracheal haemorrhages and airsacculitis. Occasionally, humans exposed to Newcastle virus develop conjunctivitis.

Shipping Fever is primarily a respiratory disease of ruminants, especially cattle and sheep in feedlots. Clinical signs include depression, inappetence, fever, and difficulty in breathing. Gross lesions include a fibrinous pleuropneumonia and/or bronchopneumonia. Affected animals exhibit stunting, poor weight gain, and frequently die. Shipping fever is most frequently seen in animals that have been recently stressed (such as through transportation). This disease can be caused by a number of different agents but is usually associated with stress (such as occurs with shipping), a viral infection, followed by a bacterial infection. The bacteria most commonly associated with shipping fever is Mannheimia haemolytica (previously Pasteurella haemolytica). This disease causes great economic losses due to reduced rate of gain of body weight, inefficient feed conversion, cost of treatments, condemnation of carcasses and death of the animals.

This disease is characterized by fever, reproductive problems (stillbirths, abortions, mummies, weak piglets) and/or respiratory problems (sneezing, difficulty breathing, pneumonia). Gross lesions are much more common in younger animals and may include enlargement of lymph nodes, cyanosis (bluing) of the skin especially noticeable on the ears, pneumonia, and clear fluid in the chest, abdomen or pericardial sac. Differences in viral strains account for the variety and extent of clinical signs and lesions.

Progressive pneumonia is a chronic disease of sheep and goats. Clinical signs are rarely seen in animals less than 2 years of age. As the pneumonia progresses, weight loss, respiratory distress and weakness are seen. At slaughter, the lungs are firm and do not collapse. The lung lobes are adhered to one another and to the thoracic wall.

Salmonella spp. affect the enteric tract of most, if not all, animal species. Clinical signs include fever, diarrhoea and dehydration and can range from inapparent infection to death from septicaemia. Young animals are usually the most severely affected. The occurrence of this disease in animals and humans has increased greatly in recent years. Intensification of the livestock and poultry industries and contamination of feedstuffs through the use of animal by-products are thought to be contributing factors to the increase in disease. Further information on Salmonella spp. can be found in Microbiological safety of meat: Salmonella spp.

Infection with these protozoans is usually asymptomatic with diagnosis made at slaughter. Losses occur due to trimming away of infected tissue or condemnation of the carcass if the condition is generalized.

Scrapie generally occurs in animals over 2 years of age. Affected animals lag behind the herd, are easily excited, develop ataxia and, despite a good appetite, progressively lose weight. Fine tremors of the head and neck become apparent. The classic clinical sign of scrapie is extreme pruritis resulting in animals scraping their bodies on surfaces in an effort to relieve the itchiness. Bilateral alopecia and erosions result from this intense scratching behaviour. Some strains of scrapie do not cause pruritis. More information on scrapie and other transmissible spongiform encephalopathies can be found in Microbiological safety of meat: Prions and viruses.

Tetanus affects swine, horses and all ruminant animals. The clinical manifestation begins as muscle stiffness and tremors, which progresses to convulsions and death.

This disease causes vomiting, severe diarrhoea and death in young pigs (< 5 weeks old). Older swine usually suffer only a short bout of vomiting and diarrhoea. Gross lesions may include reddening of the gastrointestinal tract and thinning of the wall of the small intestine.

Tuberculosis can be caused either by the bovine (M. bovis), avian (M. avium), or human (M. tuberculosis) strains of Mycobacterium. Cattle, sheep, goats and deer are readily infected by M. bovis but are rarely affected by the avian or human strains. Swine are affected by all three types of tuberculosis. Tuberculosis is a chronic disease causing decreased productivity, respiratory distress and eventually death. Caseous, granulomatous lesions (tubercles) in the lungs and/or lymph nodes are characteristic. Poultry, especially chickens, are readily infected by avian tuberculosis but resistant to the bovine and human strains. Affected poultry suffer poor productivity and are unthrifty. Tubercles are found most often in the intestines, liver, spleen and bone marrow of affected animals.

Disease of importance to fish are listed in Table 3 .

The diseases are discussed briefly below.

Clinical signs include lethargy, inappetence, flared opercula and/or laboured opercula movements. The gills may be pale with thickened tips or reddened and swollen with mucus strands trailing from the gills. Onset of illness frequently follows environmental deterioration (overcrowding, low oxygen, excessive turbidity, high ammonia levels).

Affected fish may appear normal or they may be inappetent, depressed, darker in colour, fluid-filled abdomen, exophthalmic and/or haemorrhagic at the base of the fins and vent. Grossly, the kidneys are pale and swollen, with whitish nodules.

This disease primarily affects young catfish. Clinical signs include erratic swimming, swimming tail-down at the surface, fluid-filled abdomen, exophthalmia, haemorrhages on the skin, gills and the base of the fins. Upon necropsy, petechial haemorrhages are found throughout the muscle.

This widespread disease causes lesions in the skin, gills and fins. The gills exhibit light to dark brown discoloration and necrosis. Fins become frayed; the skin becomes dull and loses coloration. Skin ulcers develop and can progress to affect the underlying muscle.

The clinical presentation of this disease is variable in catfish. Peracutely affected fish may die prior to the development of clinical signs. Acutely affected fish hang tail-down from the surface or swim in a corkscrew pattern. External examination may reveal petechial haemorrhages on the ventral surface of the body and around the mouth, raised lesions or ulcers on the upper midline near the eyes, and whitish ulcers on the skin. Gross lesions include bloody or clear yellow fluid in the abdomen, swollen kidneys and spleen and swollen, discolored liver with areas of necrosis or haemorrhage. Chronically infected fish may develop a raised cranial lesion or ulcer that eventually penetrates the skull.

The clinical picture varies with the age and species of fish and strain of Aeromonas salmonicida. In salmon this disease is usually acute (anorexia and discoloration of the skin 2-3 days before death) to peracute (death without prior clinical signs). Gross lesions include pale liver, soft kidneys, enlarged spleen and haemorrhages in the viscera. When the course of the disease is subacute, classic ulcerative lesions (furuncles) are seen.

Signs of disease include haemorrhages and ulcers of the skin, exophthalmia, haemorrhages involving the eye, fluid-filled abdomen and reddening of the fins and the bases of the fins. Internally, swollen kidneys, a pale or greenish liver and intestinal and vent haemorrhages may be seen. This disease is more frequently seen when temperatures are warmer.

Clinical signs in young fish include pale gills, exophthalmia, haemorrhages at the base of the fins and vent, darkening of the skin and white faecal material trailing from the vent. Subdermal haemorrhage may occur in the area between the head and dorsal fin. Grossly, the kidney, liver, spleen and pancreas are necrotic.

Young salmon and trout are clinically affected with IPN while older animals can be carriers. Clinical signs include erratic swimming, exophthalmia, abdominal distension and darkened bodies. Grossly the pancreas contains numerous petechial haemorrhages while the liver and spleen are pale.

This disease is caused by a protozoan parasite. Clinical signs include anorexia and lethargy, and the gills exhibit pale, swollen, clubbed and/or broken lamellae.

Affected fish exhibit abdominal swelling, exophthalmia, pale gills and a darkening in colour. Lesions include swollen, mottled kidneys and spleen.

Saprolegnia (Saprolegnia spp., Achlya spp., Dictuyuchus spp.)

Several fungal species (water moulds) affect fish and fish eggs, causing cottony tufts or greyish white patches to appear on the affected tissue.

Clinical signs range from mortality without prior clinical signs to a chronic course. In the acute form, subdermal cavities develop which ulcerate releasing serosanguinous fluid. In the chronic form, eye lesions (exophthalmos, corneal edema and ulceration) and granulomatous lesions in the muscle predominate.

Clinical signs and lesions vary greatly. Lethargy, exophthalmia, anaemia, abdominal distension, darkening of the body, and haemorrhagic skin, eyes, gills, and fin bases may be seen. Grossly, the abdomen is haemorrhagic and the liver, kidneys, and spleen are oedematous.

This chronic debilitating disease affects younger fish to a much greater degree than older fish. The characteristic behaviour, for which this disease is named, results from damage to the tail cartilage. This disease also causes the tail to become very dark. Damage can also occur to jaw, head, opercula and other areas of the spine. There are no internal lesions. Weight loss and death occur owing to the inability of the fish to move and feed properly. 

The use of ionizing radiation as a means of controlling microorganisms has been extensively researched for many years. Two technologies are used. In one, a radioactive substance, e.g. Cobalt 60, gives off the radiation. It gives off high-energy photons, called c-rays, which can penetrate foods to a depth of more than 50 cm. The second technology uses beams of high-energy electrons, often produced by an electron accelerator. The electrons can only penetrate food to a depth of 3 cm, so the thickness of material, which can be treated effectively, is limited. These technologies have been used commercially for a long time (c-rays for more than thirty years), e.g. to sterilize disposable medical equipment.

Ionizing radiation inactivates microorganisms by one of two mechanisms, described as direct and indirect inactivation. Direct inactivation refers to the collision of a photon or an electron with the genetic material of a cell. If this collision results in damage to the genetic material that cannot be repaired, the cell is inactivated. Indirect inactivation results when a photon or electron passes very near to the genetic material and ionizes a molecule of another substance (usually water). The free radical resulting from this ionization reacts with the genetic material of the cell and results in inactivation. Microorganisms vary in their sensitivity to the direct effects of ionizing radiation, with bacterial spores and viruses being most resistant. Indirect inactivation is influenced by envi-ronmental factors, such as temperature and moisture content.

Irradiation may be applied to foods to accomplish different technical objectives. Meats may be 'pasteurized', to eliminate vegetative pathogenic bacteria, or may be completely sterilized, as is done by NASA in the United States, for the production of high-quality, sterile foods for the space programme. The World Health Organization has concluded that food irradiated to any dose appropriate to achieve the intended technological objective is both safe to consume and nutritionally adequate.

Meat and meat products are irradiated primarily to improve the safety of the products by reducing the potential presence of pathogenic bacteria. Most of the pathogenic bacteria that have been associated with meat, including Salmonella, Campylobacter, and the pathogenic Escherichia coli species, are readily inactivated by irradiation. The technology of irradiation provides the meat industry with the ability to provide a fresh, non-heat-treated product to consumers that is essentially free of pathogenic food-borne bacteria.

Along with the reduction or elimination of pathogenic bacteria, there is a significant reduction in the populations of spoilage bacteria. This results in an extension of shelf-life of the fresh product, which is related to the dose at which the product is processed. Irradiated meats stored at refrigeration temperatures may have an extension of shelf-life of up to 2 weeks.

The Merck Veterinary Manual, 8th edn

Diseases of Poultry

Introduction to Fish Health Management

Diseases of Sheep

Fish Disease: Diagnosis and Treatment

Veterinary Medicine: A Textbook of the Diseases of Cattle, Sheep, Pigs, Goats, and Horses, 9th edn

Diseases of Swine, 8th edn

Infectious Diseases of Wild Mammals