Queensland Health Guidelines for Public Health Units
|1.0||August 2010||Full revision of guideline|
|2.0||June 2015||Full revision of guideline|
A number of Brucella species may cause disease in humans. To date, eight species have been identified, named primarily for the source animal or features of infection. Of these, the following four have moderate-to-significant human pathogenicity:
|Brucella melitensis||(from sheep; highest pathogenicity)|
|Brucella suis||(from pigs; high pathogenicity)|
|Brucella abortus||(from cattle; moderate pathogenicity)|
|Brucella canis||(from dogs; moderate pathogenicity)|
Clinical evidenceClinically compatible illness (NB. clinical evidence is required for reporting probable cases to NOCS but does not by itself constitute a requirement for clinicians to notify).
Laboratory definitive evidence
Isolation of Brucella species
IgG seroconversion or a significant increase in antibody level or a fourfold or greater rise in titre in Brucella agglutination titres or complement fixation titres between acute and convalescent phase serum samples. (Where possible both tests should be conducted in parallel at the same laboratory).
Laboratory suggestive evidence
A single high Brucella agglutination titre (at least 1:64). Note: the numerical value is not specified in the national case definition and the titre considered significant varies by pathology laboratory.
Community Outbreak Criteria
Two or more associated cases.
Pathology LaboratoriesTo notify by usual means if definitive or suggestive evidence.
Blood cultures are best performed on samples collected during a febrile episode, preferably while the temperature is rising. The isolation rate is improved if several samples are taken over 24 hours.
Bacterial culture and isolation will identify the genus Brucella, but not species. Queensland Health Forensic and Scientific Services (FSS) routinely perform speciation PCR testing on all Brucella isolates. B. suis, B. melitensis and B. abortus species can be identified with the current assay.
Report confirmed cases and probable cases.
Confirmed caseA confirmed case requires laboratory definitive evidence only.
Probable caseA probable case requires laboratory suggestive evidence AND clinical evidence.
- To monitor the epidemiology of brucellosis in Queensland.
- To identify locally acquired human cases not exposed to feral pigs, so that animal health authorities can be alerted to possibility of emerging infection in domestic animal populations.
Brucellosis occurs worldwide and remains one of the world's major zoonotic pathogens. It is responsible for enormous economic losses as well as considerable human morbidity in endemic areas, especially in developing areas of the Mediterranean region, the Middle East, India, central Asia and parts of Africa and Latin America. In such countries it is predominately an occupational disease of those working with infected animals or their tissues, especially farm workers, veterinarians and abattoir workers. The consumption of unpasteurised milk and milk products from infected animals is also a major risk factor in these countries.
Most notifications of brucellosis in Australia occur in Queensland. Since 1991 the number of notifications in Queensland has varied between 10 and 50 per year. Exposure to feral pigs is the main source of locally acquired brucellosis.
The pathogen could also be a potential agent of biological terrorism, particularly B. melitensis and B. suis. The bacteria are highly infectious by aerosol. It has been estimated that only 10-100 organisms are needed to constitute an infectious aerosol for humans. The bacteria are sensitive to exposure to heat and most disinfectants, but can survive in the environment for up to 2 years under specific conditions. Brucella sp. infections can lead to spontaneous abortions and intrauterine fetal death in pregnant women but have not been associated with birth defects.
The clinical features of brucellosis depend on the stage of disease, and the organs and systems involved. It is a systemic bacterial disease with acute or insidious onset, characterised by continued, intermittent or irregular fever of variable duration. Other common symptoms include: headache, weakness, profuse sweating, chills, arthralgia, depression, weight loss and generalised aching. Local suppurative infections of organs including the liver and spleen may occur, subclinical disease has been reported and chronic localised infections can occur. The disease can last for several days, months, or occasionally a year or more if not adequately treated. Osteoarticular complications occur in 20% - 60% of cases and genitourinary involvement is seen in 2% - 20% of cases. Neurobrucellosis is a less common but severe manifestation that is seen in 3% - 7% of cases. The case-fatality rate of untreated brucellosis is 2% or less.
Swine brucellosis (caused by B. suis) is endemic in the feral pig population in Queensland, and has also been reported in northern parts of the Northern Territory, New South Wales and Western Australia. B. suis has also been identified as the cause of several cases of Brucellosis in pig dogs in northern NSW.
Bovine brucellosis (B. abortus) was eradicated from the Australian cattle herd in 1989 and is presently considered an exotic animal disease in Australia.
Caprine brucellosis (caused by B. melitensis) has never been reported in goats or sheep in Australia.
Ovine brucellosis (caused by B. ovis) occurs widely in sheep in Australia but does not pose a zoonotic risk.
Infection occurs principally from exposure through breaks in the skin via contact with infected tissues, blood, urine, vaginal discharges, aborted animal foetuses and especially placentae; also by ingestion of raw milk or milk derived products from infected animals. Airborne transmission from animal to humans is also possible. A small number of cases have resulted from accidental self-inoculation of strain 19 Brucella animal vaccine; the same risk is present when Rev-1 vaccine is handled. Limited data support vertical transmission of human brucellosis and transmission via breast milk. Further study is needed to substantiate these routes.
Variable and difficult to ascertain: usually 5-60 days; 1-2 months common place, occasionally several months.
Rare person-to-person transmission. In addition to possible transmission from mother to child as above, risk may exist for medical personnel in endemic areas with gross exposure to blood, tissues, or contaminated fomites.
Severity and duration of clinical illness are subject to wide variation. Duration of acquired immunity is uncertain.
If notified on the basis of a single high agglutination titre, consult with the attending medical practitioner to attempt to confirm the diagnosis by the presence of a clinically compatible illness, and/or a further sample for laboratory confirmation.
In consultation with the attending medical practitioner and case, attempt to identify the source of infection. Especially inquire about exposure to feral pigs. Ascertain whether person has been overseas in the past 2 months or has imported an animal product from overseas.
Nil; use standard precautions if dealing with draining lesions. Disinfect purulent discharges.
A 6 week course of oral antibiotics plus 7 days of IV gentamicin: for children less than 8 years, a combination of trimethoprim/sulfamethoxazole and gentamicin or rifampicin and for adults and children 8 years or older a combination of doxycycline and gentamicin or rifampicin. Refer to latest edition of Therapeutic Guidelines: Antibiotic.
Steroids may be required for severely ill patients.
Relapses can occur in up to 10% of cases and are usually a result of sequestered rather than resistant organisms. Expert advice should be sought regarding longer duration of therapy or alternative combination regimens if indicated for relapse, osteoarticular disease, neurobrucellosis or endocarditis.
The case should be advised of the nature of the infection and its mode of transmission.
Yes, to determine if there is a cluster of infection.
Persons having exposure to the same possible source of infection as the case.
If workplace acquired, contact the occupational health officer in the workplace to inquire if there are any other cases (i.e. common exposure).
No controlled studies have been performed to assess the value of administering post-exposure prophylaxis (PEP) to persons at risk. Anecdotal evidence suggests that PEP may reduce the risk of developing clinical disease. PEP should be considered for all persons after an obvious exposure to living brucellae (e.g. following laboratory exposure). Regimens reported in the literature are: a combination of oral doxycycline 100mg bd and rifampicin 600mg qid for 3 weeks commenced as soon as exposure is confirmed. For pregnant women use trimethoprim-sulfamethoxazole 160/800mg bd for 3 weeks.
In addition, increased surveillance for clinical signs of disease is recommended for at least 6 months, and serological testing for subclinical disease is suggested every 1-2 weeks for the first 3 months and then monthly for the next 3-9 months.
The contact should be advised of the nature of the infection and its mode of transmission. Advice on possible side effects from PEP should be given if PEP is recommended.
Other Control Measures
Ultimate control of human brucellosis depends on the elimination of the disease in animals, therefore reservoir animals need to be identified and contained. Elimination of Brucella suis from feral pigs is unlikely. New, non-imported, human cases of brucellosis with no history of exposure to feral pigs should be reported to Biosecurity Queensland so that appropriate investigation and control measures, if required, can occur.
Trace source of infection. Recall incriminated products and implement remedial measures in production process.
- Educate farmers, pig shooters, and handlers of potentially infected animals, particularly feral pigs, to reduce exposure and exercise care in the handling and disposal of placenta, discharges, foetuses and aborted animals. Protective clothing and gloves should be worn during risk activities; and hand hygiene measures taken as soon as possible after contamination with potentially infected substances.
- Educate the public against drinking unpasteurised milk, particularly if travelling overseas. Boiling milk is effective when pasteurisation is not available. As cattle, sheep and goats in Australia are free of zoonotic forms of brucellosis, unpasteurised milk and milk products produced in Australia from these animals do not pose a risk of brucellosis.
- Educate dog owners to prevent dogs from consuming raw feral pig products.
Prepare a report of any outbreak investigation for the Communicable Diseases Unit, Queensland Health, on request.
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