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CLOSTRIDIAL DISEASES
BACILLARY HAEMOGLOBINURIA (REDWATER DISEASE)
BLACKQUARTER (BLACKLEG)
BLACK DISEASE (INFECTIOUS NECROTIC HEPATITIS)
BOTULISM (LAMZIEKTE, WESTERN DUCK SICKENESS)
BRAXY (BRADSOT)
ENTEROTOXAEMIA (PULPY KIDNEY DISEASE, OVEREATING DISEASE, TURNIP SICKNESS)
LAMB DYSENTERY
STRUCK
MALIGNANT OEDEMA (GAS GANGRENE)
TETANUS (LOCKJAW)
In general there are three main categories of clostridial diseases:
1)
2)
3)
Those in which the organism invade the tissues where toxin is formed,
e.g. malignant oedema,
Those in which the organism multiply in the intestine with the production of toxin
that is absorbed into the blood, e.g. enterotoxaemia,
Those in which the toxin is ingested preformed in the feed, e.g. botulism.
(Spores are viable for 1-2 years in salted meat and are resistant to 100°C).
Other clostridial diseases such as tetanus and black disease result from the elaboration
of toxin in previously damaged tissue, e.g. a deep punctured wound in tetanus and a
lesion caused by immature flukes in black disease.
BACILLARY HAEMOGLOBINURIA (REDWATER DISEASE)
This is an acute highly fatal toxaemia of cattle and sheep characterized by jaundice,
haemoglobinuria, fever and the presence of anaemic infarcts in the liver. The disease
has been recorded in the USA, Mexico, Venezuela, Chile, Turkey, Australia, New
Zealand, UK. The causal organism is Clostridium haemolyticum (Cl. novyi Type D) that
can survive for long periods in soil and bones.
Infection probably occurs by ingestion of contaminated food and water. Toxin is produced
if there is any liver damage (by fluke or mechanical injury) that produces the anaerobic
conditions necessary for the growth of spores.
Lesions
These include anaemia, jaundice, dehydratation and subcutaneous gelatinous oedema.
Blood-stained fluid is present in the pleural and peritoneal cavities, the small intestine,
and sometimes the large bowel, is haemorrhagic with blood-stained contents.
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Typical lesions are found in the liver that shows anaemic infarcts (5-20 cm), slightly
raised from the surrounding parenchyma, light in colour and outlined by a zone of
hyperaemia. The kidneys are dark in colour and petechiated with purplish-red urine in the
bladder.
Judgement
Since the disease is very sudden in onset and runs a rapid course (12 h to 4 days) it is
unlikely that cases will be encountered in the abbatoir. Total condemnation because of
acute toxaemia is carried out.
BLACKQUARTER (BLACKLEG)
This an acute infective disease of the ox and sheep caused by Clostridium chauvoei and
characterized by severe inflammation of muscles with toxaemia and high mortality. It
results from soil infection and it is therefore more common in grass-fed than in stall-fed
animals. Blackleg is worldwide in distribution and is confined to certain districts and even
particular fields on a farm.
Blackquarter spores are very resistant to destructive influence and may retain their
virulence for 10-12 years in dried muscle, and indefinitely in the soil. The period of
incubation is 2-5 days.
Susceptible animals may be infected by inoculation or, more commonly, by the ingestion
of spores in soil, dust, food or drinking water. By far the greatest proportion of cases in
cattle occur in animals between 6 months and 2 years of age, animals in good bodily
condition being the most often attacked.
Sheep may be attacked at any age and outbreaks of the disease are associated with
wounds at shearing, docking or castration. In both ox and sheep the death rate is high
(about 98%), but the disease does not affect humans.
Lesions
In the ox, infection is followed by crepitant swellings that develop in the subcutaneous
connective tissue and spread rapidly. These swellings are usually observed on the
shoulder, neck, breast, loins or thigh (the muscular areas most subjected to trauma).
Carcases of animals that have died of blackquarter emit a peculiar rancid odour, though
they do not decompose as rapidly as animals that have died of anthrax.
On examination, the connective tissue surrounding the swellings is infiltrated with yellow
gelatinous substance that may be haemorrhagic and permeated with gas bubbles. The
muscular tissue of swelling is blackish-red and oedematous and gas bubbles can be
seen. The related lymph nodes are acutely enlarged and may be haemorrhagic. The
spleen is unchanged or only slightly enlarged. The blood is dark red but coagulates
readily.
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Liver and kidneys are enlarged and congested and spongy appearance is developed
(gas formation): “foaming organs” of blackquarter.
In sheep the lesions are similar to those in the ox but the characteristic changes in the
liver and kidneys do not occur.
Differential diagnosis
It is often mistaken for extensive bruising. The flesh of blackquarter-carcase may emit the
typical rancid odour of butyric acid. Blackquarter may be confused with anthrax, but in
anthrax crepitating swellings are absent, the blood is uncoagulated and the spleen is
usually enlarged.
Judgement
If a live animal awaiting slaughter is found to be affected with blackquarter, slaughter and
dressing of the carcase should be forbidden. Where disease is detected in the dressed
carcase, total condemnation is necessary.
BLACK DISEASE (INFECTIOUS NECROTIC HEPATITIS)
This is an acute toxaemia of sheep and sometimes cattle and pigs caused by the toxin of
Clostridium novyi (oedematiens) Type B produced in the liver tissue previously damaged
by immature liver flukes.
Lesions
The affection is esentially an infectious necrotic hepatitis with a black coloration of the
inner surface of the skin due to marked and widespread engorgement of minute blood
vessels.
Judgement
Total condemnation.
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BOTULISM (LAMZIEKTE, WESTERN DUCK SICKENESS)
In animals and humans botulism is a highly fatal intoxication caused by the powerful toxin
of C. botulinum that is ingested with food. The usual source of the toxin is decaying
material (carcase, vegetables) in which spores multiply rapidly under favourable
conditions of warmth and moisture. The organism is also present in the soil and is
worldwide in distribution.
Eight different types of the organism exist, being differentiated by the serological
specificity of their toxins: A, B, C alpha and beta, D, E, F and G.
Types A, B and E are most important in causing human botulism, while C-alpha causes
disease in poultry, ducks and pheasants (Limberneck), C-beta causes conditions in
cattle, horses and mink, and D affects cattle and sheep (Lamziekte).
The disease of botulism in animals, like that in humans, is associated with a paralysis of
muscles and a progressive motor paralysis ending in death due to respiratory and
cardiac failure upon the effect of the neurotoxin. The onset of death is frequently so rapid
that no clinical signs are evident.
The possibility of circulating botulinum toxin being present in animals subjected to
casualty slaughter from outbreaks of the disease is a real one, and casualty slaughter
should only be undertaken after negative sera examinations (human hazard).
Honey-related botulism: See separately !
Lesions
May be absent. Haemorrhages may be present in the gut, heart and brain. The presence
of carrion material in the stomachs may be suggestive of botulism.
Judgement
Total condemnation irrespective of carcase condition, because of the hazard for humans.
BRAXY (BRADSOT)
This is an acute infective disease of sheep characterized by abomasitis, toxaemia and
high mortality. The affection appears in the autumn and winter months. The causative
organism is Clostridium septicum the cause of malignant oedema in animals. The
predisposing causes are probably nutritional.
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Lesions
A characteristic is the rapid post-mortem decomposition with great abdominal distension
within a few hours. There is an offensive odour when the abdomen is opened, and the
peritoneal fluid, that is turbid and increased in amount, constitutes an almost pure culture
of the microorganism.
Cloudy swelling of the kidneys, liver and heart may be observed, but the characteristic
lesions are encountered in the abomasum, where the mucous membrane shows patches
of dark red discoloration, often situated where this stomach is in contact with the rumen.
Judgement
Braxy, as with other disease in which the onset of death is rapid, is unlikely to be
encountered in meat inspection. Total condemnation.
ENTEROTOXAEMIA (PULPY KIDNEY DISEASE, OVEREATING DISEASE, TURNIP
SICKNESS)
This is a rapidly fatal toxaemia that is extremely common amongst store or fattening
sheep during the autumn and late winter. Farmers frequently confuse this disease with
braxy having a similar onset and course.
Enterotoxaemia is caused by C. perfringes, Type D, that under certain circumtances,
multiplies rapidly in the abomasum and intestine and produces a powerful toxin that is
absorbed into the circulation and quickly paralyses the vital centres in the brain. The
affection often occurs soon after a change to better feeding, for the conditions most
favourable for toxin production when the intestine contains much highly nutritious food.
Lesions
Affected sheep are seldom seen alive. After death the carcase becomes distended with
gas, and characteristic post-mortem findings are congestion of heart and lungs, bloodstained pericardial fluid, diffuse or punctiform haemorrhage of heart and endocardium
and kidney. There are no constant abomasal or intestinal lesions. Clostridium perfringens
toxin may be demonstrated in the gut.
Judgement
Total condemnation.
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LAMB DYSENTERY
This is a highly fatal, infective disease that attacks lambs in the first or second week of
life and is caused by C. perfringens, Type B. Death is due to septicaemia and toxaemia,
with or without typical ulceration of the intestines. Lambs show profuse diarrhoea and
dysentery and, on post-mortem examination, enteritis and ulceration.
Judgement
The diseasae occurs so early in the life of the lamb and is of such an acute nature that
carcases are unlikely to be encountered in meat inspection. Total condemnation.
STRUCK
Struck (Cl. perfringens type C enterotoxaemia, haemorrhagic enterotoxaemia) is a highly
fatal enterotoxaemia originally observed in Kent. It may affect lambs, calves and piglets
and is characterized by its sudden onset, dysentery and high mortality.
Lesion
The main post-mortem lesion is a necrotic, haemorrhagic enteritis with petechiae in the
heart, thymus and serous membranes.
Judgement
Total condemnation.
MALIGNANT OEDEMA (GAS GANGRENE)
This is an acute toxaemia of cattle, sheep, goats, pigs, horses and reindeer associated
with a high mortality and world-wide occurrence. It is mainly caused by Cl. septicum often
in association with other clostridial organisms such as Cl. chauvoei, Cl. novyi, Cl.
perfringens and Cl. sordelli. C. sordelli causes swelled head in sheep and Cl. novyi
swelled head in rams.
The bacterium is not found in the circulating blood of affected animals, but is widely
distributed in the soil and constant inhabitant of cultivated land. Malignant oedema is
therefore particularly associated with wound infection, particularly laceration with deep
destruction of muscular tissue and effusion of blood that forms a medium favourable for
the growth of the microorganism and the production of its toxin (3% hypochloride; Hides:
for 24h in 1% formaldehyde).
Infection of sheep may occur after shearing, docking or castration, and “bighead”, that
occurs in rams after fighting. Death occurs more rapidly in sheep than in cattle.
In pigs the disease is usually acquired by wound infection, but may also occur by
ingestion of the bacteria that penetrate the mucous membrane of the stomach.
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Lesions
Oedematous area develops at the site of inoculation within 24 hours. This swelling is at
first soft, but becomes taut and can be incised in the living animal without pain. At a later
phase the swelling may crepitate in a manner similar to the lesion in blackleg, and when
incised there is effusion of a redish-yellow fluid that contains gas bubbles and possesses
a putrid odour.
In infection after parturition there is a thick, brownish-red discharge from the vagina,
followed by a swelling on the vulval lips that is at first painful but later becomes cold,
painless, blue and crepitant.
In malignant oedema in pigs the stomach wall may show oedema and gas formation.
There may be associated changes in the liver and kidneys, that become porous due to
gas formation and constitute the “foaming organs”.
Judgement
Total condemnation.
TETANUS (LOCKJAW)
Tetanus is an acute, highly fatal infective disease caused by Clostridium tetani (Bacillus
tetani) and characterized by spasmodic contraction of the voluntary muscles.
It also occurs in cattle, more rarely in pigs, while humans are infected by contamination
of wounds. Cl. tetani is particularly abundant in the surface layers of soil, especially in
manured fields and garden soil, and can frequently be demonstrated in the intestines of
healhy horses. It readily forms spores that are terminal, spherical in shape and about
twice the thickeness of the bacterium. These spores are destroyed by boiling water, but
the digestive juices have little effect on them.
Cl. tetani produces a powerful toxin made up two components (tetanospasmin and
tetanolysin, the latter producing the disintegration of red blood cells) The toxin is
destroyed by heating to 65 C for 3 min. (Spores: 100 °C for 15 min)
Infection with tetanus is associated with injuries of the skin or mucous membranes,
particularly in wounds where there is haemorrhage and destruction of tissue. Fractures,
castration, shearing wounds or difficult parturition are common methods by which the
microorganism may gain entrance to the animal body and multiply under anaerobic
conditions. Infection may also occur in the newborn animal by way of the umbilicus.
The incubation period is from 4 to 14 days, but spores remain latent in animal tissues for
considerable periods and then, under suitable conditions such as cold, excessive heat or
muscular exertion, become active.
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Symptoms and lesions
Cl. tetani seldom reaches the blood stream, but exerts its pathogenic effects by its toxin,
that possesses an affinity for nervous system. The disease is characterized by the onset
of muscular spasm, begining in the region of head and spreading backwards to other
muscular groups. The muscles feel hard. The spasm of the masseter muscles
responsible for the common term lockjaw. There is great excitability and increased
respirations, and it is characteristic for the temperature to remain normal until death and
then rise several degrees.
In cattle, retention of the fetal membranes and a resultant septic metritis is often
associated with tetanus, the main symptoms being cessation of rumination together with
tympanitis and distension of the left flank. In sheep and goats the disease is manifested
by a stiff, stilted gait, and in pigs by a pricking up of ears and tail.
There are no characteristic post-mortem lesions of the disease (fat in heart, liver and
kidneys might become soft and grey or yellow due to hyaline degeneration). Animals that
have died of tetanus show evidence of asphyxia, the blood being dark red and showing
little tendency to clot. Petechial haemorrhages may be found on the serous membranes
of heart, together with oedema and congestion of the lungs.
Though tetanus may be recognized with ease in the live animal, its detection after
slaughter presents considerable difficulty. Ante-mortem inspection is therefore of the
greatest value.
Judgement
Tetanus is extremely unlikely to be acquired by humans consuming the flesh of an
affected animal but the imperfect bleeding of the carcase together with poor durability
and changes in the colour of the musculature, necessitate total condemnation.