JÖHNE’S DISEASE (PARATUBERCULOSIS)
Paratuberculosis is a chronic infectious disease of cattle, sheep and goats
characterized by persistent diarrhoea and wasting. The affection is not
transmissible to humans.
The causal organism, Mycobacterium paratuberculosis, is an acid-fast
bacterium resembling the tubercle bacillus.
The disease in cattle is most frequent in animals over 1.5 years old,
particularly in second-calf cows as parturition may accelerate the progress of
the disease already latent in the intestine. Infection is probably acquired in the
first year of life, but the disease develops so slowly that months may pass
before an animal shows clinical symptoms. Infected pastures are regarded as
unsafe for at least a year.
Symptoms
Oedema of the intermaxillary space is the earliest symptom of the disease,
and early wasting of the buttock muscles is a diagnostic feature.
There is at first little interference with the appetite, and rumination does not
cease. Thus, emaciation without exhaustion is a feature of the disease and
the animal gradually loses condition.
Diarrhoea soon develops, this being periodic but persistent, foul-smelling,
dark and homogenous with small bubbles on the surface. As the disease
progress there is pallor of the mucous membranes due to anaemia, and this
is followed by emaciation.
Lesions
The lesions are not strikingly evident compared with the marked emaciation
that typifies the later stages.
The earliest lesion is usually found near the ileoccaecal valve, and beside the
ileum, the caecum, colon and rectum may also be affected.. The mucous
membrane being 4 to 5 times its normal thickness, and raised in irregular
longitudinal and transverse convolutions that cannot be obliterated by
stretching. The surface of the convolutions may show areas of congestion,
and the intestinal wall may be much thickened and oedematous.
The mesenteric lymph nodes are enlarged and oedematous, but the
parenchymatous organs show little change (in the last stage of emaciation
pathological fatty infiltration of the liver may be seen). It is characteristic for
the loss of flesh to precede the loss of body fat (sickly yellowish white
colouration).
In sheep the disease frequently coexists with severe intestinal parasitic
infection and may be manifested by thickening of the ileum. The intestine may
be pigmented an intense yellow. Necrosis, caseation and calcification (never
seen in cattle) may be present in the mesenteric lymph nodes and calcified
nodules in the intestinal wall.
Judgement
Many bovine carcases encountered in meat inspection are “borderline” cases
between poorness (thin) and emaciation, and present considerable difficulty
in judgement.
Carcases classified as “poor” may be fit for human consumption food with
condemnation of the intestine.
Where there is evidence of serous infiltrations with dampness apparent on
the serous membranes of the thorax and abdomen, together with lack of
setting, it is advisable to detain the carcase overnight in a cool dry
athmosphere: a number of carcases will considerably improve in appearance
and dryness and, having a value for manufacturing purposes, may safely be
passed for food.
Definite indications of emaciation or oedema and lack of setting after the
detention period warrant total condemnation.
CROHN’ DISEASE & MYCOBACTERIUM PARATUBERCULOSIS
Crohn’s diseaseof humans is not fatal but causes chronic diarrhoea,
persistent abdominal pain, weight loss, tiredness and mental problems.
Because it is not notifiable, the number of people affected can only be
estimated buti t is thought that up to 80000 suffer from it in Britain, with
between 4000 and 8000 new cases every year. The cost to the nation of
sufferers’ medical care is estimated to be BPS 240 million per year.
Crohn’s disease is almost certainly (in 60-90% of all cases) caused by
bacteria found in milk (even if pasteurized) and drinking water supplies.
According to research data, up to 55 per cent of dairy herds in western
Europe and America are infected with the bacteria, which can survive the
pasteurization process.
The causative is called Mcobacterium avium subspecies paratuberculosis
(MAP) which is difficult to destroy. The normal pasteurization process
involves heating milk to 72 °C for 15 seconds but to be sure of killing MAP it
would need to be heated to that level for twice as long.
MAP can live udetected in cattle for years. Infected cows secrete
bacteria into their milk and ont o their pastures.
the
Tests have proved that MAP causes chronic infection of the intestines of
many animals, including 4 types of primates. American studies have isolated
MAP from the breast milk of woman with Crohn’s disease but not in woman
who do not have the illness.
Dairy herds ought to be tested for the infection and the illness ought to be
notifiable. The milk should be heated to 80 °C and then allowing itt o cool
before drinking it.