Microbial pathogen data sheets : mycobacterium bovis

MYCOBACTERIUM BOVIS
THE ORGANISM/TOXIN
(N.B. The absence of a sanitiser/disinfectant from This is one of two species of the “tubercle bacilli” this section does not necessarily imply that it is (the other is M. tuberculosis) that are able to cause tuberculosis. Unlike M. tuberculosis, M. bovis infects cattle and other animals, and so the disease THE ILLNESS
can be spread to humans via contaminated milk and Incubation: In airborne infections and in
immunocompetent people the incubation period can GROWTH AND ITS CONTROL
be years, while in immunosupressed people it may Growth: It is a characteristic of the organism that it
be months. Cases of the gastrointestinal form can is very slow growing, and so given the shelf life of occur after reactivation of infections that must have foods that it has been associated with, e.g.
unpasteurised milk and raw meat, growth in foods Symptoms: Fever, chills, weight loss, abdominal
is unlikely to be significant. The organism is a pain, diarrhoea or constipation. Other symptoms Survival:
Symptoms may last for months or years.
Temperature: Survival is better under cool The organism enters the body via the intestinal tract conditions, e.g. survived in cow faeces for 5 months in foodborne infections, and primary infection is set Water Activity Survives dry conditions well.
“tubercles”. The infection is often contained at that Inactivation (CCPs and Hurdles):
point, but it can also spread to other parts of the Temperature: Inactivated by normal pasteurisation.
An inoculum of 105 / ml cells became undetectable The reverse can be true in that pulmonary disease after 30 minutes at 63.5oC in whole milk (low can spread to the intestinal region.
temperature, long-time pasteurisation).
The case fatality rate for tuberculosis in New In meat products the D time at 61oC was 1 min, while at 55oC it was approximately 10 min.
Condition: Intestinal tuberculosis or tuberculous
Treatment at 65oC for 5 min gave a 5 D kill.
Sanitisers/Disinfectants: (These products must be Toxins: Does not produce toxins.
used as advised by the manufacturer).
At Risk Groups: Immunosupressed people are
Much of the information presented here is derived especially at risk of either acute infection or from papers describing medical rather than food reactivation of an infection acquired in the past. In industry applications of these sanitisers.
countries where infection is uncontrolled children An enzyme based-iodine disinfectant inactivated the organism more rapidly than 2% glutaraldehyde.
Long Term Effects: The course of the disease is
Ortho-phthalaldehyde applied at the minimum effective concentration resulted in a 6 log reduction Dose: The infectious dose for organisms ingested
(as opposed to inhaled) is probably very high A study of 14 hospital disinfectants found chlorine dioxide, 0.8% hydrogen peroxide plus 0.06% NZ Incidence: 357 cases of tuberculosis were
peroxyacetic acid, glutaraldehydes (2% alkaline and 2% acidic, a phenolic and chlorine (approx. 1,000 In 1999 450 cases of tuberculosis were notified, and ppm) and an iodophor were effective, some of these species identification was performed on 310 isolates. Only 1.9% (six cases) of these isolates glutaraldehyde plus 0.44% phenol plus 0.08% were caused by M. bovis, which indicates 8-9 cases In 1998 3.1% of isolates from New Zealand cetylpyridinium chloride are relatively ineffective, resident Pacific Islanders were M. bovis.
but their action may be improved in the presence of In 1997 3.0% of cases were caused by M. bovis.
In 1996 4.5% of imported tuberculosis cases were Treatment with 0.3% benzalkonium chloride is not One case in recent years has been attributed to theconsumption of unpasteurised milk.
Prepared for the Ministry of Health by ESR Ltd.
These data sheets contain a summary of information available in the literature. Because of the many variables which impact on the survival of organisms in foods,information in this sheet must be used as a guide only. Specific processes must be checked by the food manufacturer to ensure their product is safe.
Treatment: Multiple antibiotic treatment is
be detected using an immunological test.
required to be administered over protracted periods.
Environment: Can persist and remain infective in
This is because the organism may have antibiotic resistance and this will not be apparent for long Transmission Routes: Can be by respiratory
periods because of the slow growth of the organism.
aerosols between humans and animals. To a lesser The antibiotics currently used are rifampicin, extent also transmitted by milk and meat derived from infected animals. Apparently not transmitted Infected lymph nodes can be removed.
Multiply drug resistant forms have caused OUTBREAKS AND INCIDENTS
outbreaks among AIDS patients that resulted in Outbreaks: No recent reports of foodborne outbreaks of M. bovis infection could be located.
The last outbreak attributed to contaminated milk Human: Humans are a reservoir of the organism,
but human to human infection occurs only rarely.
Epidemiological Data: A study in Ireland on disease Animal: Cattle and other animals are reservoirs of
caused by M. bovis between 1983 and 1992 found the organism. The possum is a reservoir in New that most cases could be attributed to the prior Zealand, making eradication from livestock consumption of milk in the pre-pasteurisation era.
Information from Australia indicated that most non- Food: Meat and milk derived from infected animals
imported cases had worked in the livestock may contain the organism. Tubercles are detectable industry, indicating an occupational exposure.
post-mortem in food animals, and infection can also REFERENCES
Anonymous (2001) Tuberculosis in 1999-highest number of cases since 1980. New Zealand Public Health Report 8, 4-5.
Cousins, D.V. and Dawson, D.J. (1999) Tuberculosis due to Mycobacterium bovis in the Australian population: cases recorded during 1970-1994. International Journal of Tuberculosis and Lung Disease 3, 715-721.
O’Reilly, L.M. and Daborn, C.J. The epidemiology of Mycobacterium bovis infections in animals and man: a review. Tubercle and Lung Disease 76 Supplement 1, 1-46.
Prepared for the Ministry of Health by ESR Ltd.
These data sheets contain a summary of information available in the literature. Because of the many variables which impact on the survival of organisms in foods,information in this sheet must be used as a guide only. Specific processes must be checked by the food manufacturer to ensure their product is safe.
Prepared for the Ministry of Health by ESR Ltd.
These data sheets contain a summary of information available in the literature. Because of the many variables which impact on the survivalof organisms in foods, information in this sheet must be used as a guide only. Specific processes must be checked by the food manufacturerto ensure their product is safe.

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