FMD is an acute viral and extremely contagious disease of cloven footed animals such as cattle, sheep, goats, pigs and antelope. It is manifested by vesicles and erosions in the muzzle, nares, mouth, feet, teats, udder and pillar of the rumen. There are three main strains of viruses causing FMD, namely A, O and C. Three additional strains, SAT 1, SAT 2 and SAT 3 have been isolated from Africa and a further strain ASIA-1 from Asia and the Far East.
Transmission: Direct and indirect contact with infected animals and their secretions including saliva, blood, urine, faeces, milk and semen, aerosol droplet dispersion, infected animal by-products, swill containing scraps of meat or other animal tissue and fomites and vaccines.
Antemortem findings:
Before vesicle formation:
Vesicle formation:
The vesicles and later erosions are commonly found on the muzzle, tongue (Fig. 46), oral cavity, teat and on the skin between and above the hoofs of the feet. In more chronic cases in cattle the hoof become loose and the animal may walk with characteristic “clicking” sound (Slippering).
Some strains of FMD, particularly in swine, sheep and goats cause erosions instead of vesicles.
Postmortem findings :
Necrosis of heart muscle(tiger heart), usually only in young acutely infected animals.
Ulcerative lesions on tongue, palate, gums, pillars of the rumen and feet.
Judgement : In countries or in zones within a country free or nearly free of FMD diseased or suspect animals are prohibited to be admitted in an abattoir or slaughtered. If FMD is suspected on postmortem examination the carcass and viscera are condemned and appropriate action recommended by the regulatory authorities of the country must be taken. In countries where this disease is present, the judgement should be in accordance with the current animal health requirements, and consisted with effective public health protection. Particular attention should be paid to secondary bacterial infections and general findings. Sanitary measures should be taken to comply with national animal health policy.
Remarks : Latent infections with Salmonella organisms were reported in animals affected with FMD.
Differential diagnosis in bovine and ovine species : Vesicular stomatitis, allergic stomatitis, feedlot glossitis, photosensitization, bluetongue, rinderpest, infectious bovine rhinotracheitis, malignant catarrhal fever, bovine papular stomatitis, bovine viral diarrhoea, pseudocowpox, ovine pox, contagious ecthyma, footrot, mycotoxicosis and increased salt in concentrate.
Discussion : In order to prevent the spread of the virus in the abattoir, the equipment and room should be disinfected with 2 % NaOH (caustic soda). In some countries sodium carbonate (Na2CO3) is used. The vehicle conveying diseased animals should also be disinfected and abattoir personnel leaving the abattoir should pass through a footbath with 1 % solution of NaOH.
The virus of FMD can survive in meat and meat products for a considerable length of time. Outside the pH range of 6 – 9, viral infectivity is destroyed. A bovine carcass matured at above +2°C produces a drop in the pH of muscle tissue to between 5.3 – 5.7 within 24 hours of slaughter. This is caused by the formation of sarcolactic acid. Quick freezing of the meat arrests acid production and consequently the virus remains infective for about 6 months. In salted meat at 4°C, the virus is still infective in bone marrow and lymph nodes for 6 months. In blood clots in large vessels of cattle and swine, the virus is infective for 2 months. The virus is inactivated by ultraviolet rays, acetic acid, 2 % lye and ethylene oxide. At high temperatures, the virus is only active for a short period. 2 % NaOH solution inactivates the virus in 1 – 2 minutes. In dry refuse in stalls, the virus remains infective for 14 days, 3 days on soil surfaces in summer compared to 39 days in fall. It is also infective for 39 days in urine and for 20 weeks on hay dried at 22°C. The virus can be destroyed with 0.5 % citric or lactic acid, by cooking meat to an internal temperature of 69°C and by pasteurization processes of milk.
Fig. 45: Excessive salivation in a cow affected with FMD.
Fig 46: FMD. Extensive areas of eroded epithelium on a bovine tongue.
Rinderpest is an acute, highly contagious, fatal viral disease of cattle, buffalo and wild ruminants manifested by inflammation, haemorrhage, erosions of the digestive tract, wasting and often bloody diarrhoea. Some swine species are also susceptible. Man is not susceptible to RP virus.
Transmission : Direct contact with infected animals or their excretions and secretions and fomites. The virus appears in the blood and in secretions before the onset of clinical signs and this may cause infection in abattoirs and stockyards.
Antemortem findings :
Postmortem findings :
Judgement : The carcass derived from a feverish and debilitated animal showing the sign of acute disease on antemortem examination should be condemned. In the areas free of RP and in zones where final stages of eradication exist, the animals are also condemned. In endemic zones, if acute symptoms of the disease are not present during clinical examination, the carcass may have limited distribution. In areas affected with outbreak which are protected by vaccination, heat treatment of meat is suggested if economically worthwhile. The affected organs are condemned.
Remarks : Rinderpest virus is sensitive to environmental changes and is destroyed by heat, drying and great number of disinfectants.
Differential diagnosis : Bovine viral diarrhoea, malignant catarrhal fever, infectious bovine rhinotracheitis, bluetongue, coccidiosis, foot and mouth disease, vesicular and necrotic stomatitis and bovine papular stomatitis. Vesicular diseases do not have accompanying haemorrhage and blisters should be differentiated from erosions (ulcers) seen at RP.
Fig. 47: Rinderpest Erosions on the dental pad and the hard palate which resemble FMD.
Fig. 48: The mucosal surface of Peyer's Patches showing necrosis and congestion.
This is a viral disease of ruminants, horses and swine characterized by vesicular lesions of the mouth, feet and teats. VS virus has two immunologically distinct serotypes, Indiana and New Jersey.
Transmission : In susceptible animals, contamination of pre-existing abrasions with saliva or lesion material, by ingestion of contaminated pasture or during milking within dairy herds. Mechanical transmission by biting arthropods is also a possibility. The virus is isolated from mites, tropical sand flies and mosquitos.
Antemortem findings :
Postmortem findings :
Judgement : The carcass of an animal affected with vesicular stomatitis is approved if the disease is not in the acute stage and secondary changes are not present. Parts of the affected carcass and organs are condemned. A carcass showing acute changes and systemic lesions is condemned. If VS is not confirmed by laboratory examination, the judgement will be the same as for the FMD.
Differential diagnosis : Foot and mouth disease, swine vesicular exanthema, vesicular disease, bovine papular stomatitis
The mouth and muzzle lesions: Bovine viral diarrhoea, rinderpest, mycotic stomatitis, photosensitization and Potomac valley fever in horses
Teat lesions: Cowpox, pseudo-cowpox, pseudo-lumpy skin disease and bovine herpes mammillitis
Fig. 49: Vesicular stomatitis. Tongue lesions.
An acute viral disease of cattle, deer, bison and buffalo characterized by inflammation of mucous membranes of the nose, eyes, corneal opacity, profuse nasal discharge and enlargement of lymph nodes. MCF is arbitrarily divided into peracute, intestinal, head-eye and mild forms according to antemortem findings. It is not communicable to man.
Transmission: Close contact between cattle and wildebeest (gnu, antelope), by common use of drinking troughs or by direct contact between cattle and newborn wildebeest and placenta of parturient dams. In American or European MCF, cattle are infected from sheep.
Antemortem findings :
Postmortem findings :
Judgement :In the early stages of the disease, when fever, emaciation and systemic signs are lacking, the carcass of the affected animal may be approved as inferior meat. Otherwise, when fever, emaciation and systemic signs are present, the entire carcass and viscera are condemned. The condemned material may be used for rendering.
Differential diagnosis : Bluetongue, rinderpest, bovine viral diarrhoea/mucosal disease, foot and mouth disease, vesicular stomatitis
Fig. 50: Malignant catarrhal fever Early stages of corneal opacity, conjunctivitis and the reddening of the eye lids.
Fig. 51: Malignant catarrhal fever. “Tiger striping” in the distal colon.
This is an acute infectious viral disease of the central nervous system in mammals.
Transmission : It is usually transmitted through the saliva by a bite from a rabid animal, commonly the dog or jackal. Man is infected the same way.
Antemortem findings :
Furious form
Paralytic form
Postmortem findings: Possible inflammation of gastrointestinal mucosa
Judgement: In endemic areas carcasses may be approved if the animal was bitten eight days before slaughter and within 48 hours of slaughter. The bite area and surrounding tissue must be condemned, and prevention taken to prevent occupational hazards.
Differential diagnosis : Indigestion, milk fever or acetonemia when first seen, foreign body in the mouth, early infectious disease, poisoning
Discussion: In a diseased animal, the virus is found in saliva, salivary gland and nervous tissue. Extreme caution should be instituted in abattoirs in order to prevent occupational hazards. Abattoir personnel can contract the disease through surface contact with infected tissue. Infection does not occur by consumption of meat from a rabid animal.
Slaughter may be prohibited during a quarantine period of 8 months following exposure to the disease. An animal suspected of having rabies should be placed under a “Held tag”. The warning sign should read “The animal is not to be handled”. Any person who was in touch with the animal should thoroughly wash his/her hands with strong soap and/or disinfectant. If possible, the wound should be opened to encourage bleeding in order to flush out the virus and expose the deeper area of the wound. Tincture of iodine (up to 0.001 % aqueous solution of iodine or ethanol 43.70%) should be further applied.
Acute pox viral disease of cattle manifested with sudden appearance of nodules on the skin.
Transmission : Insect vectors by direct and indirect transmission. Seasonal and geographic distribution.
Antemortem findings :
Postmortem findings :
Judgement : Carcass of an animal showing mild cutaneous lesions and no fever associated with general signs of infection is conditionally approved pending heat treatment. The affected parts of the carcass and organs are condemned, Carcass of an animal showing, on antemortem examination, generalized acute infection accompanied with fever, is condemned.
Differential diagnosis : Allergies, screw-worm myiasis, urticaria, dermatophilosis (streptothricosis), bovine herpes dermophatic infection, cattle grubs, vesicular disease, bovine ephemeral fever, photosensitization, besnoitiosis (elephant skin disease), sweating weakness of calves, bovine farcy and skin form of sporadic bovine lymphomatosis
Fig. 52: Lumpy skin disease. Various sized cutancous nodules in a severe case of lumpy skin disease.
Fig. 53: Cut surface of the nodules in the parenchyma of the lung and interlobular edema.
A herpes virus infection of cattle and sometimes sheep and goats manifested by cutaneous lesions and fever.
Transmission : Biting insects, mechanical milking
Antemortem and postmortem findings :
Microscopy reveals intranuclear inclusions and giant cells in the skin.
Judgement : Carcass of an animal affected with BHD is disposed similar to an animal affected with lumpy skin disease
Differential diagnosis : Dermatophilis infection, cowpox and pseudocowpox, vesicular stomatitis and lumpy skin disease. The latter is differentiated from BHD by enlarged lymph nodes.
Fig. 54: Bovine herps dermophatic disease. Dried scabs on the skin of the neck.
Fig. 55: BHD.
Ulcerative lesions of the teats and udder.
IBR is a highly infectious viral respiratory disease of cattle, goats and pigs manifested by inflammation of respiratory passages and pustular lesions on the male and female genital organs. Generally four forms of the disease are recognized; the respiratory form, the genital form, the enteric form and the encephalitic form.
Transmission: Respiratory droplet and nasal exudate in the respiratory form of IBR. Obstetrical operations, coitus and licking of genitalia of affected animals in the genital form of disease.
Antemortem findings:
Respiratory form
Genital form
Enteric form
The encephalitic form in calves
Postmortem findings:
Judgement: Carcass of an animal affected with IBR is approved if signs of acute infection are not present and the animal is in good body condition.
Differential diagnosis: Pneumonic pasteurellosis, bovine viral diarrhoea, malignant catarrhal fever and calf diphtheria
Fig. 56: Breathing through the mouth and salivation in a bovine affected with IBR.
Fig. 57: IBR. Acute inflammation of the larynx and trachea
This is an infectious viral disease of cattle manifested by an active erosive stomatitis, gastroenteritis and diarrhoea.
Transmission: Direct contact with clinically sick or carrier animals, indirect contact with feedstuffs or fomites contaminated with urine, nasal and oral secretions or faeces and contact with aborted fetuses. Transmission through aerosol droplet dispersion or by insect vector may also be a possibility. Virus may persist in recovered and chronically ill cattle which are considered a potential source of infection.
Antemortem findings :
Postmortem findings :
Shallow erosions present on the entrance of the nostrils, mouth, pharynx, larynx, oesophagus, rumen (Fig. 58), omasum, abomasum (Fig. 59), caecum and less frequently in Peyer's patches in the small intestine.
Erythema of the mucosa with submucosal haemorrhage in the abomasum, small intestine, caecum and colon. Stripped appearance on the caecal and colon mucosa is similar to that seen in rinderpest.
Cerebral hypoplasia and cataracts in calves.
Judgement: Carcass and viscera of an animal, which on antemortem examination showed generalized signs of acute infection accompanied with fever and/or emaciation, are condemned. Chronic cases of BVD with no systemic involvement have a favourable judgement of carcass, viscera and organs.
Differential diagnosis : Malignant catarrhal fever, rinderpest, blue tongue and vesicular diseases. The latter produce vesicles which are not present in BVD. Diseases with no oral lesion nor diarrhoea include salmonellosis, Johne's disease and parasitism.
Fig. 58: BVD. Congestion and erosions in the ruminal mucosa.
Fig. 59: BVD. Inflammation of the abomasum (abomasitis, gastritis).
Bovine leukosis is a persistent and malignant viral disease of the lymphoreticular system. It occurs in all breeds and in both sexes.
Bovine leukosis is observed in two forms : a) the sporadic and b) the enzootic form. The sporadic form is rare and occurs in cattle under three years of age. The enzootic form is most commonly found in adult cattle, particularly in cull cows.
Transmission: By small amounts of infected blood (e.g. infected needles, dehorning), vertical transmission from the dam to the calf (3 – 20 % of calves may become infected) and by colostrum or milk (less than 2 %). Insect transmission is also a possibility; higher rates of infection were reported in the summer.
Antemortem findings :
Postmortem findings:
Judgement: Carcass of an animal affected with leukosis (lymphosarcoma) is condemned. When a diagnosis cannot be made by postmortem findings, a laboratory diagnosis should be performed. If lymph node hyperplasia is the histological diagnosis, the carcass is approved for human consumption. Depending on disease prevalence, leukosis reactors may be totally approved or conditionally approved pending heat treatment.
Differential diagnosis : Lymphadenitis, lymphoid hyperplasia, hyperplastic haemolymph nodes, pericarditis, enlarged spleen in septicemic conditions, other neoplasms and parasitism.
Fig. 60: Leukosis. Neoplastic mass infiltrating the heart muscle.
Fig. 61: Leukosis. Neoplastic growths in the intestine. Both lesions were histologically confirmed as lymphosarcoma.
BSE is a progressive and fatal disease of adult cattle characterized by a progressive degeneration of the central nervous system causing neurological signs in animals. Some scientists suspect that an unusual and atypical virus-like transmissible agent called a prion is associated with the etiology of BSE. Prion is the term currently used in literature.
Transmission : The ingestion of protein feed supplements prepared from sheep meat or sheep by products contaminated with scrapie virus.
Antemortem findings :
The progressive degeneration of the central nervous system causes neurologic signs:
Fig. 62: BSE. Degenerative lesion in the cerebral cortex.
Diagnosis can be confirmed only on the postmortem histological examination of brain tissue. Microscopic lesions include degenerative lesions of the cerebral cortex (Fig. 62), medulla and central grey matter of the midbrain.
Judgement : Carcass is condemned.
Differential diagnosis : Rabies, listeriosis, bovine pseudorabies (mad itch), other brain infections in cattle, the nervous type of acetonemia, hypocalcemia, hypophosphatemia and hypomagnesemic tetany
Discussion : The first reported cases of this disease were in dairy cows in 1987 from different locations in the United Kingdom. The disease is now also recognized in some other countries in and outside Europe. BSE belongs to a group of human and animal diseases classified as transmissible spongiform encephalopathies. Significant human diseases of this group are Kuru and Creutzfeldt-Jacob's disease. Scrapie, which affects sheep and goats also belongs in this group.
Researchers are trying establish if BSE and scrapie have the same causative agent, and if the modified form of the scrapie agent is also a possible causative agent of BSE. Prions are also the causative agents of transmissible mink encephalopathy (TME) and of chronic wasting disease (CWD) of mule deer and elk.
BSE affects only adult animals and the incidence within-herd is low. The breed, gender or year and seasons are not associated with the development of this disease, nor is contact with sheep. In order to control this disease, in the U.K. the following actions were taken:
“Black dung” when affecting African cattle and buffalo
“Sheep fever” when seen in sheep
Heartwater is an acute, non contagious disease of cattle, sheep, goats, antelopes and wild ruminants. It is caused by the rickettsial organism Cowdria (Rickettsia) ruminantium.
Transmission: Heartwater is transmitted by various species of Amblyomma ticks. Transstadial transmission of the organism occur in vector ticks.
Antemortem findings :
Peracute form
Acute form
Nervous signs include
Postmortem findings :
Judgement : Carcass of an animal affected with heartwater is condemned in the acute stage of the disease. In a chronic case, the carcass may be approved if adequately bled and muscles are wholesome in colour and texture. The affected organs are condemned.
Differential diagnosis : Peracute form of heartwater should be differentiated from anthrax. The acute nervous form of the disease is differentiated from tetanus, rabies, cerebral trypanosomiasis, strychnine poisoning, piroplasmosis, theileriosis, lead and organophosphate poisoning, parasitism, arsenical poisoning and poisoning with certain plants.
Fig. 63 : Heartwater Cowdria ruminantium in bovine brain smear (arrow).
Q fever is a disease of cattle, sheep, goats, donkeys, camels, fowl, dogs, cats, pigeons and humans. It is caused by Coxiella burnetii. Q fever is an occupational disease of livestock personnel. farmers and laboratory personnel.
Transmission : Ticks spread infection to cattle which develop mild disease. The faeces deposited on animal hide by ticks may be the source of infection for humans. Q fever is also transmitted by inhalation or dust contaminated with infected animal secreta or excreta. Healthy animals may serve as a carrier and shed the organism in milk, urine, faeces, placenta and fetal fluids. They harbour the infection and no clinical signs are observed. Contaminated meat and water are further means of infection read.
field cases there are no clinical signs of this disease. In the disease produced by the inoculation of cows via the udder the clinical signs may include:
No gross lesions are reported in cattle.
Discussions : Coxiella burnetii is highly resistant and was isolated from farm soil 6 months after the removal of animals. It may persist in the udder up to 3 years. The temperatures of milk pasteurisation (in bulk at 63°C for 30 minutes or the common method at 72°C for 15 seconds) kill this agent in milk. Vaccination will reduce shedding of organisms in milk.
This disease in humans has a sudden onset and is characterized by loss of appetite, weakness and generalized malaise lasting from 1 – 2 weeks. Pneumonia may also be present. Death may be caused by endocarditis in older people. More severe symptoms of Q fever are noticed.
This is an acute, subacute or chronic highly infectious disease of cattle caused by Mycoplasma mycoides var, mycoides.
Transmission : Aerosol and droplet infection from the infected animals. The recovered animal called “lungers” act as carriers and shedders, especially under stress.
Antemortem findings :
Postmortem findings :
Judgement : Carcass of an animal affected with contagious bovine pleuropneumonia is condemned if the disease is associated with fever, inadequate bleeding of carcass, serous infiltration of the brisket and emaciation. Recovered animals showing no generalized signs of the disease are approved and the affected organs are condemned.
Differential diagnosis : Shipping fever (Pasteurellosis). East coast fever, foreign body pneumonia, IBR, tuberculosis, chlamidial infections and lungworms
Fig. 64: Contagious bovine pleuropneumonia. Straw coloured fluid in the thorax and partial lung hepatization.
Fig. 65: Contagious bovine pleuropneumonia. Lobar pneumonia with red hepatization and marbled appearnce of lung lobules.
Black quarter is an acute infectious disease of cattle and sheep manifested by severe inflammation of the muscle with high mortality. It is caused by Clostridium chauvoei.
Transmission : The organisms of blackleg are found in the soil. During grazing, organisms may enter the digestive tract of a susceptible animal. Clostridium chauvoei is also found in the digestive tract of healthy animals. In sheep the agent is transmitted through wounds at shearing, docking and castration and during lambing in ewes.
Antemortem findings :
Postmortem findings :
Fig. 66: Black leg. Dark-red skeletal muscle of a heifer showing haemorrhage, necrosis, edema and emphysema.
Judgement : Carcasses of animals affected with black leg should be condemned. It is prohibited to slaughter and dress an animal diagnosed with this disease at antemortem examination.
Differential diagnosis : Other acute Clostridial infections, lightning strike, anthrax, bacillary haemoglobinuria, lactation tetany, extensive haemorrhage and acute lead poisoning.
Discussion : Black leg is worldwide in distribution. Well nourished animals are more frequently affected. It is also more commonly seen in grass fed animals than in stall fed animals. Clostridia are soil-borne organisms which cause disease by releasing toxins. Specific antitoxin and antibiotics are rarely effective in the treatment of this disease. An adequate preventive vaccination program may be the most effective method in protecting the animals from black leg.
Botulism is a disease manifested by progressive muscular paralysis. It is seen in humans, animals, birds and fish and is caused by various strains of Clostridium botulinum.
Transmission : Decomposed flesh and bones are the source of infection for animals. Incubation period 12 – 24 hours. However, 2 hours up to 14 days incubation period has been recorded.
Antemortem findings :
In cattle and horses
In sheep
In pigs
Postmortem findings : Foreign material in fore-stomachs or stomachs may be suggestive of botulism.
Judgement : Total condemnation of carcass because of human hazards.
Differential diagnosis : Parturient paresis, paralytic rabies, equine encephalomyelitis, ragwort poisoning in horses, miscellaneous plant poisoning.
In sheep - louping ill, hypocalcemia and some cases of scrapie.
Discussion : Cl. botulinum is found in the digestive tract of herbivores. Soil and water contamination occurs from faeces and decomposing carcasses. The proliferation of Cl. botulinum organisms may also occur in decaying vegetable material. Sporadic outbreaks of botulism are reported in most countries. Outbreaks of botulism in cattle and sheep in Australia, Southern Africa and the Gulf coast area of the United States are associated with phosphorus deficient diets and ingestion of carrion. Cattle, sheep and rarely swine are susceptible to this disease. Dogs and cats are resistant.
Cl. botulinum produces neurotoxin which causes functional paralysis. Seven strains of this organism (“ A through G ”) are distinguished according to immunological differences. The diseases caused by various strains of this agent are frequently regarded as a separate entity owing to some of their prominent signs. Names such as “Bulbar paralysis in cattle”, “Lamsiekte in sheep” in South Africa (meaning lame sickness), and “Limberneck in poultry” are often used. Cl. botulinum is often found in anaerobic conditions of deep wounds. It produces neuroparalytic exotoxins which cause symptoms of the disease. This organism will grow and produce toxins if the temperature is between 10 – 50°C, pH above 4.6. water activity (AW) above 0.93 and anaerobic conditions exist. Fresh meats are implicated with less than 10 % of botulism outbreaks. The major sources of this organism are fish, home cured meats, home canned vegetables and fruit. Eggs, milk and their products are rarely the cause of an outbreak. Most frequently, raw, insufficiently cooked foods or foods not fully salted, cured, dried or smoked are implicated. Botulism toxins are heat labile and food suspected of having the organism should be boiled before serving.
In man the signs of the disease are weakness, dizziness, blurred or double vision, dilatation of pupils, dry mouth, difficulties in breathing and speech, progressive muscular weakness, respiratory failure and death. Pneumonia may be a complication associated with botulism in man.
Fig. 67: Botulism. Sternal recumbency. Muscular paralysis of hind and front quarters.
Malignant edema is a bacterial disease of cattle, sheep, goats, swine, horses and poultry. It is caused by Clostridium septicum and is manifested by wound infection. The infection is commonly soil-borne. Deep wounds associated with trauma provide ideal condition for the growth of this agent.
Antemortem findings :
Postmortem findings:
Judgement : Carcasses of animals affected with malignant edema are condemned.
Differential diagnosis: Blackleg. In malignant edema the muscle is not involved and the wound site is noted. Anthrax in pigs. Subcutaneous edema in the throat region is present.
Tuberculosis is a chronic disease of many animal species and poultry caused by bacteria of the genus Mycobacterium. It is characterized by development of tubercles in the organs of most species. Bovine tuberculosis is caused by Mycobacterium bovis. It is a significant zoonotic disease.
Transmission : An infected animal is the main source of transmission. The organisms are excreted in the exhaled air and in all secretions and excretions. Inhalation is the chief mode of entry and for calves infected milk is an important source of infection. When infection has occurred tuberculosis may spread: a) by primary complex (lesion at point of entry and the local lymph node) and b) by dissemination from primary complex.
Antemortem findings:
Postmortem findings:
The diagnosis may be confirmed by making a smear of the lesion and with Ziehl-Neelsen. The TB bacterium is a very small red staining bacillus.
Fig. 68: Tuberculous granuloma in the mediastinal lymph nodes. M. bovis was isolated.
Fig. 69: Lesion of tuberculosis in the lungs.
Discussion : Mycobacteria invade cattle by respiratory (90 – 95 %) and oral routes (5–10 %). Congenital infection in the bovine fetus occurs from an infected dam. Tuberculosis lesions can be classified as acute miliary, nodular lesions and chronic organ tuberculosis. Young calves are infected by ingestion of contaminated milk. The incidence of human tuberculosis caused by Mycobacterium bovis has markedly dropped with the pasteurization of milk. It also has dropped in areas where programs of tuberculosis eradication are in place. Man is susceptible to the bovine type. In cattle, lesions of tuberculosis caused by the avian type are commonly found in the mesenteric lymph nodes. Tuberculosis in small ruminants is rare. In pigs the disease may be caused by the bovine and avian types. Superinfection is specific in cattle.
Judgement : Carcass of an animal affected with tuberculosis requires additional postmortem examination of the lymph nodes, joints, bones and meninges. It is suggested that the Codex Alimentarius judgement recommendations for cattle and buffalo carcasses be followed.
Carcasses are condemned
Carcass of a reactor animal without lesions may be approved for limited distribution. If the economic situation permits, this carcass should be condemned. Heat treatment of meat is suggested during early and final stages of an eradication programme: in low and high prevalence areas where one or more organs are affected, and where miliary lesions, signs of generalization or recent haematogenous spread are not observed. If the economical situation permits, then the carcass is condemned.
In some countries, the carcass is approved if inactive lesions (calcified and/or encapsulated) are observed in organs and without generalization in lymph nodes of carcass.
Differential diagnosis : Lung and lymph node abscess, pleurisy. pericarditis, chronic contagious pleuropneumonia, actinobacillosis, mycotic and parasitic lesions, tumours, caseous lymphadenitis Johne's disease, adrenal gland tumour and lymphomatosis
Johne's disease is a chronic, infectious bacterial disease of adult wild and domestic ruminants such as cattle, sheep, and goats. It is characterized by the thickening and corrugation of the wall of the intestine, gradual weight loss and chronic diarrhoea and is caused by Mycobacterium paratuberculosis.
Transmission : Ingestion of faeces harbouring Mycobacterium paratuberculosis
Antemortem findings :
Postmortem findings :
Judgement : Carcass of an animal affected with Johne's disease is approved when generalized systemic signs of disease are not present. A poor, thin and slightly moist carcass should be held in the chiller and assessed after 24 or 48 hours. If the dryness and setting of the carcass improves during this time it can be released. The carcass with associated edema and emaciation is condemned.
Differential diagnosis : Other causes of diarrhoea and weight loss, malnutrition, chronic salmonellosis, parasitism (e.g. Ostertagiasis), winter dysentery, Bovine Viral Diarrhoea (BVD), “hardware” disease, coccidiosis, liver abscesses, kidney disease, inflammation of the heart and its sac, toxic inflammation of the intestine caused by arsenic, plants and mycotoxicosis and neoplasm.
Fig. 70 : Johne's disease. Thickened and corrugated intestinal mucosa.
Leptospirosis is an important and relatively common disease of domestic and wild animals and humans. In cattle, it is manifested by interstitial nephritis, anaemia and mastitis and abortion in most species. Leptospira spp. are the causative agents.
Transmission : Animals contract the disease by eating and drinking leptospira-contaminated urine, water, or by direct contact of broken skin or mucous membranes with mud, vegetation or aborted fetuses of infected or carrier animals. Recovered animals and animals with unapparent (subclinical) leptospirosis frequently excrete billions of leptospiras in their urine for several months or years.
Antemortem findings :
Acute and subacute forms
Severely affected animals
Severe illness in young calves may be associated with yellowish discoloration of mucous membranes and reddish-brown urine before death. The chronic form has mild clinical signs and only abortion may be observed. If meningitis occurs, the animal may show incoordination, salivation and muscular rigidity.
Postmortem findings :
Fig. 71 : Leptospirosis. Interstitial nephritis in a bovine.
Judgement : Carcass of an animal affected with acute leptospirosis is condemned. A chronic and localized condition may warrant an approval of the carcass.
Differential diagnosis : Acute and subacute forms to be differentiated from babesiosis, anaplasmosis, rape and kale poisoning, bacillary haemoglobinuria, post parturient haemoglobinuria and acute haemolytic anaemia in calves. The presence of blood in the milk is a characteristic clinical sign which will differentiate leptospirosis from other infectious diseases.
Discussion : Leptospirosis is a zoonosis and is also an occupational hazard for farmers, veterinarians and butchers.
Human infection may occur by contamination with infected urine and urine contents. The bacteria may be also found in milk in acute cases, however, it does not survive for long period of time in milk. Pasteurization will also kill leptospiras. They can survive for months in moist and humid environments, particularly in swamps, ponds and streams or poorly drained pastures.
Brucellosis of cattle is an infectious, contagious disease caused by Brucella abortus and is characterized by abortion in late pregnancy and a high rate of infertility. B. melitensis affects goats, B. ovis sheep and B. suis swine. B. abortus may occur in horses.
Transmission : An uninfected animal may become infected with Brucella organisms by contaminated feed, pasture, water, milk, by an aborted fetus, fetal membranes and uterine fluid and discharges. The disease may also be spread by dogs, rats, flies, boots, vehicles, the milking machine and other equipment used in the barn. The Brucella organism may be occasionally shed in urine.
Antemortem and postmortem findings :
In cattle
In sheep
Judgement: Cattle and horse carcasses affected with brucellosis are approved (after removal of affected parts), as Brucella bacteria remain viable for only a short period in the muscles after slaughter. In acute abortive form (after the miscarriage), cattle carcasses are condemned. Pig, sheep, goat and buffalo carcasses require total condemnation. Heat treatment may be recommended in some areas for these species due to economic reasons. Affected part of the carcass, udder, genital organs and corresponding lymph nodes must be condemned.
Reactor animals should be carefully handled during slaughter and dressing procedures. Gloves and goggles should be worn when known reactors are being slaughtered and hygroma lesions should be sprayed liberally with 1 % lactic acid at meat inspection.
Differential diagnosis: Causes of abortion in cattle, IBR, vibriosis, leptospirosis, trichomoniasis, mycoplasma infections, mycosis, nutritional and physiological causes.
Discussion: Brucella organisms have only a short life in the muscles of slaughtered animals. They are destroyed by lactic acid. While slaughtering and dressing the reactors, a hook should be used in handling the uterus and udder. Employees in close contact with infected animals should wear gloves and avoid accidental cuts.
In humans, brucellosis is called “Undulant Fever”. The general population is not at risk with this disease if high levels of hygiene and sanitation are practised. Pasteurized milk is brucella-free. Affected humans will suffer from intermittent high fever, headache and generalized malaise.
Brucellosis is an important zoonosis in particular in rural areas in developing countries and is an important occupational hazard for veterinarians, meat inspectors, farmers, animal health inspectors and butchers.
Fig. 72: Brucellosis, Hygromas on the knee joints. This condition may be a sequel to Brucella abortus infection.
Anthrax is a peracute disease of ruminants manifested with septicemia, sudden death and tarry blood from the body openings of the cadaver. It is caused by Bacillus anthracis.
Transmission: Man may contract anthrax by inhalation, ingestion and through a wound in the skin. Biting flies have been shown to be transmitters.
Antemortem findings:
The peracute and acute forms in cattle and sheep are without clinical signs. Death may follow in the acute form after 1 – 2 hours of illness. The acute form lasts about 48 hours.
In pigs and horses this disease is usually localized and chronic and is often characterized by swelling around the throat and head.
Antemortem findings in pigs:
Postmortem findings:
Diagnosis of anthrax is carried out by direct microscopic examination of tissues and fluids (Fig. 73).
Fig. 73: Anthrax. Toluidine blue stain. Bacillus anthracis in a bovine spleen. Anthrax bacilli in tissue seen in short chains surrounded by a common capsule.
Judgement: Condemnation of the carcass and its parts by burning or burial. If disposed by burial, the carcass should be buried at least 6 feet below ground. The site should be surrounded by a foot thick layer of quicklime.
Differential diagnosis: Peracute blackquarter and septicaemic form of other diseases. In splenic enlargement as seen in babesiosis, anaplasmosis and leucosis, spleen consistency is firm. In anthrax, the spleen is soft and upon incision the pulp exudes like thick blackish-red blood.
Discussion: If an animal has died from an unknown cause in an abattoir's pen or in the stockyard, a blood smear from the tip of the ear should be examined to eliminate anthrax as a cause of death. All measures should be taken to prevent further contact with the carcass. The orifices of the nose, vulva and anus should be packed with cotton swabs to eliminate further spillage of discharge. The carcass must not be opened. Due to insufficient oxygen supply in the closed carcass, spores of B. anthracis will not be formed and the organism will be killed. The spilled discharge is firstly removed by drying with sawdust and sand and is then destroyed together with the carcass. The carcass is wrapped in thick plastic sheets and destruction is performed under the supervision of an appropriate government official.
An open carcass facilitates exposure of B. anthracis to air and consequently, spores are formed within a few hours. Anthrax spores are resistant to heat and disinfectants and may survive in a suitable environment for years.
The abattoir's pen or stockyard area suspected of being in contact with an anthrax animal should be disinfected with 10 % NaOH or 5 % formaldehyde and cleaned. This cleaning should also include the cattle trucks or cars used for the transportation of infected animals. All personnel that were in contact with anthrax or that handled contaminated material, are also subjected to decontamination. The arms and hands should be washed with liquid soap and hot water. After they have been rinsed, they should be immersed for about one minute, in an organic iodine solution or 1 p.p.m. solution of mercuric perchloride or other acceptable agents. This is followed by a potable water rinse. Clothing of the personnel involved should also be cleaned and thoroughly disinfected by boiling.
If the carcass is discovered on the killing floor, all operations must cease. The carcass and its parts including hides, hooves, viscera and blood must be condemned and destroyed. The carcasses which have been dressed by the same abattoir employees prior to or after the affected carcass must also be condemned and destroyed. Those carcasses which had been dressed before the affected carcass may have a second option of being salvaged with sterilization. They must be boiled for a minimum of 3 hours if contamination occurred with blood splashes. If impractical, these carcasses may be used for “canned meat” for which heat treatment is recommended.
Disinfection of equipment used for the dressing of a diseased carcass as well as the infected abattoir area, should be done with 5 % solution of sodium hydroxide (NaOH). This disinfectant is used because of its action on fat and grease removal. Heat in the form of a blowtorch can be used for disinfecting buildings.
Salmonellosis is a disease which occurs in all animals and humans. In animals, salmonellosis is characterized clinically by one of three syndromes: a) peracute septicemic form:, b) acute enteritis or c) chronic enteritis.
The young, old, debilitated and stressed animals are at greater risk. More then 200 antigenically different serotypes of Salmonella have been identified and all of these possess pathogenic potential. The most frequently identified serotypes of the organisms which cause the disease in cattle are S. typhimurium, S. dublin, S. muenster and S. newport. Salmonellosis in stressed animals is frequently associated with inadequate diet, irregular feeding, water deprivation, overcrowding, parasitism, weather extremes, pregnancy, parturition, intercurrent diseases etc. The calving complications which may predispose the disease include abortion or early termination of pregnancy, retained placenta, endometritis and post-parturient metabolic conditions.
Transmission: Ingestion of feed that have been contaminated by the faeces of infected animals, by drinking water in stagnant ponds and by the carrier animals. In housed animals, transmission is via contaminated feedstuff containing improperly sterilized animal by-products such as bone and meat meal and fish meal. Casual workers, infected clothing and utensils, transportation trucks and birds may transmit the disease to the farm. Active carrier animals shed Salmonella organisms intermittently and without obvious stress factors. Latent carriers with stress factors are also identified in the transmission of salmonellosis.
Human infection is transmitted via contaminated water, raw milk and meat. Compared to bovines, pigs and poultry are more significant sources of infection in humans (see Chapter 4 and 7).
Antemortem findings:
Peracute septicemic form
Approximately four weeks after the onset of diarrhoea
Acute enteritis
Chronic enteritis - Preceded by acute enteric form
Postmortem findings:
Septicemic form
Acute enteritis
Chronic enteritis
In the septicemic and acute enteric forms, Salmonella organisms are present in the blood, liver, bile, spleen, mesenteric lymph nodes and in intestinal content. In the chronic form, bacteria is present in the intestinal lesions and less frequently in other viscera.
Judgement: Carcass affected with Salmonellosis is condemned.
Differential diagnosis: Acute diarrhoea in calves: Diarrhoea caused by infections (such as rotavirus, corona virus, cryptosporidiosis, E. coli), septicemia, dietetic gastroenteritis, coccidiosis, Clostridium perfringens type C enterotoxaemia
Acute diarrhoea in adult cattle: Bovine viral diarrhoea, coccidiosis, “grain overload”, gastrointestinal parasitism, winter dysentery, arsenic and lead poisoning, bracken fern poisoning and intestinal obstruction
Chronic diarrhoea of adult cattle: Johne's disease, copper deficiency and gastrointestinal parasitism
Haemorrhagic septicemia is a systemic disease of cattle, buffalo, pigs, yaks and camels. It is caused by Pasteurella multocida type B of Carter. Outbreaks of this disease are associated with environmental stresses such as wet chilly weather and overworked, exhausted animals. It is specific type of pasteurellosis distinct from of other forms of pasteurella infections.
Transmission: By ingestion of contaminated feedstuff.
Antemortem findings:
Postmortem findings:
Judgement: Carcass of an animal affected with haemorrhagic septicemia is condemned. If the disease is diagnosed on antemortem examination, an animal should not be allowed to enter the abattoir. Dressing of such a carcass would create potential danger for the spread of infection to other carcasses.
Differential diagnosis: Anthrax, blackleg, acute leptospirosis, rinderpest, other pasteurellosis, snake bite and lighting stroke.
Fig. 74: Haemorrhagic septicemia Fibrinous bronchopneumonia.
Calf diphtheria is an acute oral infection of calves less than 3 months old. It is caused by Fusobacterium (Sphaerophorus) necrophorum. This agent also causes liver abscesses and “foot rot” in cattle.
Transmission: Fusobacterium necrophorum is an inhabitant of cattle's digestive tract and the environment. Under unhygienic conditions, infection may be spread on feeding troughs and dirty milk pails. Some of the contributory factors for occurrence of this disease include abrasions in the oral mucosa, animals suffering from poor nutrition and other (intercurrent) disease present in young calves.
Antemortem findings:
Postmortem findings:
Judgement: Carcass of an animal affected with local lesions is approved. Generalized diphtheric lesions associated with pneumonia or toxaemia require the carcass condemnation. The carcass is also condemned if lesions are associated with emaciation.
Differential diagnosis: Vesicular diseases, neoplasms and abscesses
Actinobacillosis is a chronic disease of cattle caused by Actinobacillus lignieresi. It is manifested by inflammation of the tongue and less frequently lymph nodes of the head and of even the viscera and carcass.
Antemortem findings:
Postmortem findings:
Typical actinobacillosis lesions in the lymph nodes and organs consist of greenish-yellow thick creamy pus with “sulphur granules”. These are bacterial colonies surrounded by club like structures
Judgement: Carcass of an animal affected with active progressive inflammatory lesions of actinobacillosis in lymph nodes and lung parenchyma is condemned. Condemned material should be sent to authorized rendering plant. If the disease is slight and confined to lymph nodes, the head and tongue and whole carcass are approved after the condemnation of lymph nodes. If the tongue is diseased and no lymph nodes are involved the head and carcass are approved. The tongue is condemned.
Differential diagnosis: Neoplasms, tuberculosis, abscesses in the lymph nodes, foreign body, salivary cysts, fungal granulomas, chronic pneumonia and parasites
Fig. 75: Actinobacillosis. Actinobacillosis of the tongue. The tongue is enlarged, firm and contains numerous granulomatous lesions. It is called “wooden tongue” because of its firmness due to diffuse proliferation of fibrous tissue.
Fig. 76: Actinobacillosis. Multifocal, well demarcated yellow lesions in the retropharyngeal lymph node of a bovine animal.
Actinomycosis is a chronic granulomatous disease of cattle and pigs and rarely in sheep and horses. It is caused by Actinomyces bovis which is an obligatory parasite in the mucous membrane of the mouth and pharynx. Infection occurs following injury with a sharp object or hard feed pieces to the oral mucosa.
Antemortem findings:
Postmortem findings:
Judgement: see Actinobacillosis
Differential diagnosis: Tooth infection, impacted food, bone injury, neoplasms and osteomyelitis due to other causes
Fig. 77: Actinomycosis. Diffuse granulomas in maxilla and formation of green yellow pus. “Sulphur granules” are found in the pus.
Pyelonephritis is a purulent and inflammatory bacterial disease of the kidney pelvis and parenchyma caused by Corynebacterium renale. This disease is essentially observed in adult cows and sows. A predisposing factor for developing a kidney infection is trauma to the bladder and urethra during parturition.
Transmission : Infection is spread from clinically normal “carrier cows”. The organism enters via vulva from: a) bedding contaminated with urine b) tail swishing by “carrier cows” c) venereal transmission by infected bulls, and d) non sterilized obstetrical instruments.
Antemortem findings :
Postmortem findings :
Judgement : It depends on infection of one or both kidneys and/or presence of a urine odour. Carcass of an animal affected with pyelonephritis or nephritis is condemned if : 1) renal insufficiency is associated with uraemia; 2) acute infection of the kidney is accompanied with systemic changes in the organs and lymph nodes, and/or degeneration of body tissues. Borderline cases with uraemic odours should be kept in the chiller for 24 hours. They are subjected to a boiling test. If a urinary odour is not present after detention, the carcass may be approved.
Subacute or chronic kidney infections with no systemic changes allow for a favourable judgement of carcass. Only the affected parts are condemned. Pyelonephritis associated with kidney stones often has a favourable judgement of the carcass.
Differential diagnosis : Enzootic haematuria in certain areas, post-parturient haemoglobinuria, reticulitis, peritonitis, cystitis, metritis, leptospirosis, Johne's disease, white spotted kidneys of calves, urinary obstruction, infarcts, neoplasms and hydronephrosis
Fig. 78: Pyelonephritis (Contagoous) Bovine Pyelonephritis). Cut section of kidney showing multifocal abscessation in the cortex and medulla.
Fig. 79: Pyelonephritis associated with urolithiasis (stones). Chemical analysis revealed oxalate composition.
Metritis is inflammation of the uterus. This condition is of bacterial origin. It occurs as a result of calving problems such as retention of placenta, abortion, twin births, abnormal labour and traumatic lesions of the uterus cervix and vagina.
Antemortem findings :
Postmortem findings :
Judgement : Carcass of an animal affected with acute metritis is condemned if it is associated with septicemia or toxaemia. In chronic cases, when toxaemic signs are lacking, the carcass may be approved if no antibiotic residues are found.
Differential diagnosis : Recent calving
Fig. 80: Metritis. Necrotizing inflammation of the uterus with greyish-brown foul smelling uterine exudate.
Fig. 81: Pyometra. Enlarged uterus containing greenish -yellow exudate.
Mastitis is inflammation of the udder caused by bacteria, fungi and yeasts. Depending on the virulence of the agent and resistance of the udder, mastitis is manifested in acute or chronic forms.
Antemortem findings :
Postmortem findings :
Judgement : Carcass and viscera are condemned if acute or gangrenous mastitis is associated with systemic changes. If infection has spread from the supramammary lymph nodes via the iliac lymph nodes to the lumbar lymph nodes, this can be taken as evidence of spread of infection from its primary location. The condemnation of the carcass may then be warranted. A localized condition of the udder has a favourable judgement of the carcass.
Differential diagnosis : Edema, haematoma and rupture of the suspensory ligament
Fig. 82: Chronic mastitis. Enlarged, firm udder. Incision into the udder parenchyma shows normal milk and pale yellow granular appearance of the udder parenchyma.
Fig. 83: Brown red edematous udder parenchyma. The udder culture resulted in a heavy growth of Staphylococcus aureus.
Endocarditis is inflammation of the endocardium of the heart. The lesion is most commonly seen in the valves. It may be the result of bacteraemia caused by infection in some remote organs such as the udder, uterus or other sites.
In cattle, the organisms most commonly associated with endocarditis are Actinomyces pyogenes and Streptococcus spp.. Strains of Escherichia coli are also frequently found. The lesion is most commonly found on the valves. Portions of vegetation may become detached and released into the blood stream as emboli which may lodge in other organs. They may be septic or aseptic. The latter contain thrombotic material. Emboli, brought from the right heart to the lungs by blood vessels may cause pulmonary abscesses, or pulmonary thrombosis and the emboli brought from the left heart to the spleen and kidneys may cause septic or aseptic infarcts in these organs. Abscesses in the heart may also be observed.
Antemortem findings :
Postmortem findings :
Fig. 84: Endocarditis. Vegetative valvular endocarditis.
Judgement: Carcass of a debilitated animal is condemned for verrucose endocarditis if it is associated with lesions in lungs, liver or kidneys. Carcass affected with ulcerative or verrucose endocarditis with no signs of systemic changes and negative bacteriological result may be approved after heat treatment is applied. Endocarditis showing scar tissue is approved. The heart is condemned.
Differential diagnosis : Pneumonia, pericarditis, pulmonary edema, emphysema, pleuritis, lymphoma, high altitude disease, congenial heart disease, congenital valvular heart cysts or deformities especially in calves.
TRP is caused from the perforation of the reticulum by a metallic foreign body. It is mostly seen in adult dairy cattle and can occur in beef cattle.
Antemortem findings :
If mild septicemia develops the animal shows:
In chronic localized peritonitis, acute signs and pain lessen, temperature falls and stomach reticulo-rumen motility may return.
Postmortem findings :
Judgement : Viscera and carcass are condemned - a) if the animal is affected with acute diffuse peritonitis or acute infectious pericarditis associated with septicemia; b) carcass with traumatic pericarditis associated with fever, large accumulation of exudate, circulatory disturbances, degenerative changes in organs, or abnormal odour. c) carcass with chronic traumatic reticulo-peritonitis and/or purulent pericarditis with associated pleuritis, abscessation and edema of the chest.
Chronic adhesive localized peritonitis and chronic pericarditis without systemic changes in well nourished animals allow a favourable judgement of the carcass. The affected parts of the carcass and organs are condemned.
A carcass affected with infectious exudative pericarditis in a subacute stage may be conditionally approved pending heat treatment, if bacteriological and antibiotic residue findings are negative.
Differential diagnosis : Uterine or vaginal trauma, abomasal ulceration with perforation, liver abscessation, pyelonephritis, ketosis, abomasal displacement and volvulus, and “grain overload”.
Fig. 85: TRP. Cross section of the heart reveals thick fibrinous deposits that encircled heart. Rusty nail has penetrated through the wall of the reticulum into the pericardium in this case.
