Peter D Massey, DrPH, GCPH, RN, Program Manager Health Protection, Hunter New England Health, NSW.

Posted Flock & Herd April 2013

Zoonoses are 'those diseases and infections which are naturally transmitted between vertebrate animals and man' (WHO, 1959). Of the emerging human infectious diseases approximately 60%-70% are zoonoses (Jones et al, 2008). An emerging zoonosis is defined by WHO as 'a zoonosis that is newly recognised or newly evolved, or that has occurred previously but shows an increase in incidence or expansion in geographical, host or vector range' (WHO, 2004). There are more than 40 zoonotic diseases currently recognised of public health significance in NSW (Adamson et al, 2011). People with a zoonotic illness frequently present with non-specific symptoms so under-diagnosis may occur. Cross reactivity of serology and the need for acute and convalescent sera may also result in under-diagnosis. Exposure factors are important in determining the likelihood of disease.

Leptospirosis and brucellosis are emerging diseases in parts of NSW, and have human health and animal health issues that are closely linked.

Leptospirosis is a bacterial zoonotic disease caused by one of nine pathogenic Leptospira species. Humans usually become infected through broken skin or mucous membrane contact with water, food, soil or vegetation contaminated with urine from infected animals. The incubation period is 5 to 14 days (range from 2-30 days). The illness usually lasts from a few days to 3 weeks. Outbreaks are commonly associated with exposure to flood water contaminated with the urine from infected animals, but exposure during mouse plagues are also of concern (NSW Health, 2012).

Ninety-seven notifications of leptospirosis in humans were reported for the period 2009-2012 in NSW. The peak being in 2011 with 39 notifications, this coincided with a mouse plague in south-west NSW. More than 80% of notifications are in males with the peak age groups being 30-34 years and 50-54 years (NCIMS, 2013a).

Brucellosis is a zoonotic infection caused by Gram-negative aerobic coccobacilli from the Brucella genus (Bossi et al, 2004). Four Brucella species are associated with moderate to significant human pathogenicity, specifically Brucella melitensis which is found primarily in goats, Brucella suis in pigs, Brucella abortus in cattle and Brucella canis in dogs. Humans have also very infrequently been infected with Brucella species from marine mammals (Van Bressem et al, 2009). Globally B. melitensis more frequently affects humans than the other Brucella species and is the most virulent, pathogenic and invasive species, followed by B. suis, B. abortus and B. canis. B. abortus has been eradicated from Australia and B. melitensis and B. canis are not found in Australia (Newman et al, 2010).

Brucellosis symptoms in humans are non-specific and may include undulant fever, sweats, malaise, anorexia, headache and back pain. The onset can be insidious or acute, generally beginning 2-4 weeks after exposure, but can occur up to 6 months later (MMWR, 2009). Depression and chronic infection can occur (Young, 2009) with delays in diagnosis increasing the risk of complications (Eales, 2010).

Human infection with B. suis follows occupational or recreational exposure to infected animals, inhalation of infectious aerosols, laboratory exposure, or consumption of inadequately cooked contaminated meat (Young, 2009). Worldwide many cases of human infection follow contact with infected feral pigs or 'wild boars' (Meng et al, 2009).

Sixteen notifications of Brucellosis in humans were reported from NSW for the period 2009-2012. Nine of the notifications were from feral pig hunters in north-west NSW. Brucella suis has recently been identified in feral pigs in northern NSW and continues to emerge as a human and animal health issue (Ridoutt et al, 2013, DV Conference paper). Most notifications are in young males (NCIMS, 2013b; Irwin et al, 2009).

The vaccination of livestock against leptospirosis will reduce some of the risk for humans but as infection is also from rodents and feral pigs, an important level of risk remains. Currently the most important means of preventing leptospirosis and brucellosis in humans is to take precautions when coming into contact with potentially infected animals (NSW Health, 2012; Queensland Government, 2010; WHO, 2006. Many of the current strategies to reduce the risk of leptospirosis and brucellosis do not appear appropriate or acceptable for people at highest risk of disease, such as farmers and feral pig hunters (Massey et al, 2011). More acceptable strategies need to be developed and tested in consultation with the people who need to implement them.

Emerging zoonotic diseases remain an important challenge for human health and animal health practitioners to tackle together.


  1. Bossi P, Tegnell A, Baka A, Van Loock F, Hendriks J, Werner A et al. Bichat guidelines for the clinical management of brucellosis and bioterrorism-related brucellosis. Euro Surveillance 2004; 9(12): E15-E16
  2. Eales K, Norton R, Ketheesan N. Brucellosis in northern Australia. American Journal of Tropical Medicine and Hygiene 2010; 83(4): 876-878
  3. Jones KE, Patel NG, Levy MA. Global trends in emerging infectious diseases. Nature 2008;451(7181):990-994. 70
  4. Irwin M, Massey P, Walker B, Durrheim D. Feral pig hunting: a risk factor for human brucellosis in north-west NSW. New South Wales Public Health Bulletin 2009; 20(11-12): 192-194
  5. Massey PD, Polkinghorne BG, Durrheim DN, Lower T, Speare R. Blood, guts and knife cuts: reducing the risk of swine brucellosis in feral pig hunters in north-west New South Wales, Australia. Rural and Remote Health 11: 1793
  6. MMWR, Brucella suis infection associated with feral swine hunting - three states, 2007-2008. Morbidity & Mortality Weekly Report 2009; 58(22): 618-621
  7. Meng X, Lindsay D, Sriranganathan N. Wild boars as sources for infectious diseases in livestock and humans. Philosophical Transactions of the Royal Society of London B: Biological Sciences 2009; 364(1530): 2697-2707
  8. Newman L, Stirzaker S, Knuckey D, Robinson K, Hood J, Knope K et al. Australia's notifiable disease status, 2008: Annual Report of the National Notifiable Diseases Surveillance System. Communicable Diseases Intelligence 2010; 34(3): 157-224
  9. NSW Health. Leptospirosis Fact sheet. (Online) 2012. Available:
  10. NSW Health Notifiable Conditions Information Management System (NCIMS)(HOIST), Communicable Diseases Branch and Centre for Epidemiology and Evidence, NSW Ministry of Health. (Online) 2013a. Available:
  11. NSW Health Notifiable Conditions Information Management System (NCIMS)(HOIST), Communicable Diseases Branch and Centre for Epidemiology and Evidence, NSW Ministry of Health. (Online) 2013b. Available:
  12. This web page is managed and authorised by Centre for Health Protection of the NSW Department of Health. Last updated: 27 March, 2009
  13. Queensland Government. Brucellosis. Queensland Health Fact Sheet. (Online) 2010. Available:
  14. Ridoutt C, Lee A, Jordan D, Moloney B and Massey PD . Surveillance of swine brucellosis and Leptospira spp. in feral pigs (Sus scrofa) and the potential risks to humans and livestock in northern New South Wales, Australia. 2013 DV Conference, Armidale, NSW
  15. Van Bressem MF, Raga JA, Di Guardo G, Jepson PD, Duignan PJ, Siebert U et al. Emerging infectious diseases in cetaceans worldwide and the possible role of environmental stressors. Diseases of Aquatic Organisms 2009; 86(2): 143-157
  16. Woolhouse MEJ, Gowtage-Sequeria S. Host range and emerging and reemerging pathogens. Emerg Infec Dis 2005;11(12):1842-1847
  17. World Health Organization. Brucellosis in humans and animals. (Online) 2006. Available:
  18. World Health Organization. Zoonoses. Technical report series no. 169. Geneva; 1959
  19. World Health Organization. Report of the WHO/FAO/ OIE joint consultation on emerging zoonotic diseases. Geneva; 2004
  20. Young E. Brucella species. In: G Mandell, J Bennett, R Dolin (Eds). Mandell, Douglas, and Bennett's principles and practice of infectious diseases, 7th edn. Philadelphia, PA: Churchill Livingstone Elsevier, 2009; 2623-2642


Site contents and design Copyright 2006-16©