VIEWS: 11 PAGES: 7 POSTED ON: 10/9/2011
Salmonella in Australian Macropods FACT SHEET Introductory statement Human salmonellosis is one of the most common and economically important zoonotic diseases in the world (OIE, 2008). It is therefore important to recognise that macropods can harbour salmonellae without displaying clinical signs of disease (Samuel, 1982). It is not uncommon for people to come into direct contact with macropods or their faeces in the urban environment, as kangaroos are commonly found grazing at local parks and golf courses and wildlife carers often hand-rear orphaned joeys. The risk posed by Salmonella to both people and their pets through carcass contamination during harvesting and processing of kangaroos is not known. Aetiology Salmonella is a gram-negative, rod-shaped bacilli belonging to the family Enterobacteriaceae, genus Salmonella (CDC, 2008). Salmonella nomenclature is complex and evolving (Brenner et al., 2000). Currently, the genus Salmonella consists of only two species, S. enterica and S. bongori. S. enterica is further divided into six subspecies, which are referred to by a Roman numeral and a name (I, S. enterica subsp. enterica; II, S. enterica subsp. salamae; IIIa, S. enterica subsp. arizonae; IIIb, S. enterica subsp. diarizonae; IV, S. enterica subsp. houtenae; VI, S. enterica subsp. indica (OIE, 2008; Brenner et al., 2000). The individual names of each serotype in subspecies I continue to be used for identification, whilst antigenic formulae are cited for unnamed serotypes described after 1966 within the remaining subspecies and in S.bongori. S. bongori, formally classed as subsp. V, still retains this symbol in classification despite being recognised as a separate species. Antigenic formulae include subspecies designation, followed by O (somatic) antigens and flagellar protein antigens (H) in accordance with the Kauffmann–White scheme (OIE, 2008; Brenner et al., 2000). At the first citation of a serotype in subsp. I, the genus name is given followed by the word “serotype” or the abbreviation “ser.”, then the serotype name. Subsequently, the name may be written with the genus followed directly by the serotype name. The serotype name is capitalised and not italised (Brenner et al., 2000), although variations of this exist in the literature. Natural hosts Salmonellae are known to infect a wide range of natural hosts, including macropods. Within Australia, quokkas (Setonix brachyurus) on Rottnest Island, pet kangaroos, kangaroos held in captivity and hand- reared joeys are particularly susceptible to infection (Speare and Thomas, 1988; Hart et al., 1985; Iveson and Bradshaw, 1973; Arundel, 1981). Records collated by the National Enteric Pathogens Surveillance System (NEPSS) in Australia up until 2006 indicate that Salmonella spp. are most commonly isolated from red (Macropus rufus), eastern grey (Macropus giganteus) and western grey (Macropus fuliginosus) kangaroos. Salmonella has also been reported in the boodie or Lesueur’s bettong/rat kangaroo (Bettongia lesueur). A significant number of isolates were obtained from macropods whose species was recorded only as kangaroo, rat kangaroo or in one instance, as wallaby (National Enteric Pathogens Surveillance Scheme, 2007). Consequently, it is possible that the list of natural macropod host species is more extensive. World distribution Salmonella has a world-wide distribution, but appears to be most prevalent in areas of intensive animal husbandry, particularly where pigs, calves and poultry are housed in confinement (OIE, 2008). Occurrences in Australia Salmonella is present throughout Australia. Incidence of foodborne salmonellosis is highest among young children and their carers, together with residents of the Northern Territory (OzFoodNet Working Group, 2007). Page 1 27/06/2009 Epidemiology The morbidity and mortality rate of Salmonella infection in wild macropods is believed to be negligible. Although theoretically possible under conditions of environmental stress, there have been no confirmed reports of primary clinical disease in these animals in their natural habitat (Speare et al., 1989). Contamination of kangaroo meat, however, does suggest that wild macropods are capable of harbouring the organism. Studies have also demonstrated the presence of infection in a large number of healthy, captive macropods. In captivity, these animals may become infected as a result of oral consumption of contaminated feed or water (Samuel, 1982). Shedding of Salmonella is variable and cannot always be related to the level of stress the animal is exposed too. Healthy macropods (species unspecified) housed in hygienic, large, grassed enclosures were found to have higher rates of infection than macropods held at a research institute that were regularly exposed to stress associated with handling, fighting and travel. Despite the introduction of an infected kangaroo to this latter group, all animals remained negative. There were no differences in the prevalence which could be attributed to the sex, age or species of macropod (Samuel, 1982). Three agile wallabies (Macropus agilis) orally fed a dose of S. ser. Infantis began shedding the organism within twenty four hours, despite the absence of clinical signs. Prevalence of Salmonella infection in orphaned joeys is considered to be significant. A severely ill joey is likely to excrete more Salmonella than a healthy joey, posing a greater risk to its carer (Speare and Thomas, 1988). Clinical signs Salmonellosis is the clinical manifestation of infection with Salmonella (Blood and Studdert, 1999). In hand-reared joeys and kangaroos held in captivity, salmonellosis can cause varying levels of gastroenteritis and septicaemia, manifesting most commonly as diarrhoea. Infection has also been reported to cause death as a primary pathogen and as an opportunistic invader of the intestinal tract in animals in captivity (Samuel, 1982). Joeys often present as dull and lethargic with a reduced appetite. Diarrhoea becomes haemorrhagic and foul smelling with time (Staker, 2006). Clinical disease is possible in free-ranging macropods subjected to environmental stress, but has not been reported (Speare et al., 1989). Many infected kangaroos are asymptomatic, yet are still capable of shedding large numbers of Salmonella. Diagnosis Diagnosis in kangaroos is based on isolation of the organism from aseptically collected tissue at necropsy or from faeces or rectal swabs. As many animals are asymptomatic carriers, other evidence of disease compatible with salmonellosis must be present. Prior or current infection of animals by some serovars may also be diagnosed serologically (OIE, 2008), although this has not been reported in macropods. Clinical Pathology Clinical pathology in macropods has not been described. Pathology Due to the large number of healthy macropods found to carry Salmonella yet exhibit no clinical signs, it is often difficult to attribute illness, death and consequently, pathology, to this organism. The natural history of Salmonella in wild macropods has largely been studied in the quokka (S. brachyurus) on Rottnest Island, located off the coast of Western Australia (Hart et al., 1985; Iveson and Bradshaw, 1973). Despite virtually all animals being positive throughout the summer months, no evidence of disease has been found in infected quokkas (Hart et al., 1985). Consequently, there are no reports of pathology. Agile wallabies (M. agilis) infected with S. infantis were found to shed the bacteria within a day of being inoculated however no signs of illness were displayed. Whilst no gross or histological changes were noted at post mortem, Salmonella was recovered from the walls of the ileum, caecum, stomach, stomach contents and mesenteric lymph nodes draining the intestine (Samuel, 1983). Salmonella has been isolated less commonly from the urine, liver, lung, kidney, heart, abdomen and spleen of macropods. Carriers often harbour the organism in their mesenteric and ileocaecal lymph nodes (Thomas et al., 2001). Page 2 27/06/2009 Differential diagnoses In captive macropods, differential diagnoses of Salmonella include other causes of gastroenteritis and diarrhoea. Coccidiosis is a common differential. In the event of acute death, toxoplasmosis should also be considered. Strongyloides has been found to cause diarrhoea and death in eastern grey (M.giganteus), western grey (M. fuliginosus) and red kangaroos (M. rufus) as well as a red-necked wallaby (Macropus rufogriseus) (Arundel, 1981; Winter, 1957). In hand-reared joeys, diet and environmental stress, coccidiosis, yeast/candidiasis, roundworms, antibiotic administration and cryptosporidia are all differential diagnoses of diarrhoea, listed from most through to least likely (Mason, 2007). Other causes of bacterial diarrhoea, including E. coli and Klebsiella, should also be considered (Gage, 2002). Laboratory diagnostic specimens There are numerous methods for isolation of Salmonella in use world-wide. In macropods, culture is the most common method of diagnosis and is used to isolate Salmonella from tissues collected aseptically at post mortem or from faecal and rectal swabs in infected animals. Studies have shown that the relative yield of Salmonella in faecal material is greater than from rectal swabs (Hart et al., 1982). Lymph nodes, primarily the mesenteric, commonly harbour Salmonella in carrier animals, even when they are not shedding. The detection rate of Salmonella was found to be 2.4 times greater in joeys that had died than in live joeys as a result of the isolation of Salmonella spp. from lymph nodes (Speare and Thomas, 1988). Consequently, these are particularly useful tissue samples to collect at post mortem. Salmonella has also been isolated from ileocaecal lymph nodes, liver, lung, urine kidney, spleen and gall bladder (Samuel, 1982; Thomas et al., 2001). Samples should be collected as aseptically as possible during the acute phase of disease or as soon after death as possible. It is also preferable to collect samples prior to the commencement of any antibiotic treatment (OIE, 2008). Laboratory procedures Salmonellae may be isolated using a variety of culture techniques, involving pre-enrichment to resuscitate sublethally damaged salmonellae, enrichment media containing inhibitory substances to suppress competing organisms and selective plating agars to differentiate salmonellae from other enterobacteria. Care must be taken when selecting an enrichment media as some can be toxic to certain Salmonella serovars. More detailed information on the culture of Salmonella can be obtained from the ‘Manual of diagnostic tests and vaccines for terrestrial animals 2008’ (OIE, 2008). Other forms of Salmonella detection in use include immunomagnetic separation (IMS), electrical conductance/impedence and PCR. Serological tests to detect infected herds/flocks have also been developed and include the serum agglutination test (SAT) and ELISA (OIE, 2008). Their use has not been reported in macropods. Treatment There are no published reports of the efficacy of antibiotics in the treatment of Salmonella infection in macropods. Culture and sensitivity is likely to provide a useful means of determining the most effective antibiotic to use, given it is not contraindicated in the species. Gage (2002) recommends the use of a broad spectrum sulfa/sulfa-trimethoprim antibiotic at a dose of 5mg/kg of the trimethoprim component P/O OID for 5-7 days (Gage, 2002). Gentamycin and amoxicillin have also been suggested (Staker, 2006). Additional oral or Intravenous fluids coupled with glucose/electrolytes, probiotics, a multivitamin and a reduction in diet and environmental related stress may assist in recovery (Staker, 2006). There is no requirement to treat asymptomatic infection in macropods. Prevention and control Minimising diet and environmental related stress is paramount in preventing and controlling Salmonella in macropods in captivity and joeys in care. Dogs should be prevented from cleaning the cloaca of hand reared joeys and carers should ensure their hands are washed immediately after contact with the animal. Artificial pouches should be washed/disinfected if soiled, avoiding contamination of the joey’s fur. Regular cleaning and disinfection of enclosures, including the removal of faecal matter will assist in reducing environmental contamination. Salmonellae are susceptible to a range of disinfectants, including 1% sodium hypochlorite, 70% ethanol, 2% glutaraldehyde, iodine-based disinfectants, C phenolics and formaldehyde. They can also be killed by moist heat (121° for a minimum of 15 min) or C dry heat (160-170° for at least 1 hour) (The Center for Food Security and Public Health, 2005). In Page 3 27/06/2009 captivity, feed contamination can be a source of infection and should be investigated for the presence of salmonellae. Professional shooters working in the commercial harvesting industry need to ensure the gut is not perforated during the evisceration process, resulting in contamination of the carcass at harvesting. Cross contamination at the processor can be minimised by thoroughly washing knives between carcasses and implementing adequate decontamination procedures. All individuals coming into contact with kangaroos need to maintain adequate levels of hygiene. Care should be taken when handling and storing kangaroo meat to avoid cross contamination of other foodstuffs. Thorough cooking of meat intended both for human and pet consumption will also reduce the risk of salmonellosis. Surveillance and management Notifiable Salmonella serovars within Australia include Salmonella ser. Enteriditis in poultry, Salmonella ser. Abortus equi, Salmonella ser. Abortus ovis and Salmonella. ser. Pullorum. A number of these are also notifiable to the OIE. These serotypes are largely species specific and are unlikely to cause infection in macropods. Since 1980, the National Enteric Pathogens Surveillance System (NEPSS) has collated, analysed and disseminated data on human enteric bacterial infections diagnosed in Australia. Reports of isolates are received from the five laboratories capable of serotyping and phage typing Salmonella within Australia. Salmonella isolates are submitted to these laboratories by other diagnostic laboratories throughout the country. The NEPSS publish their findings via Communicable Diseases Intelligence (CDI) (Department of Health and Ageing, 2008). In 2000, the OzFoodNet network was established by the Australian Government Department of Health and Ageing to undertake national investigations into gastroenteritis outbreaks and clusters of disease potentially related to food products. Results are announced quarterly and annual reports have been published in CDI since 2002 (Department of Health and Ageing, 2008). Statistics According to the National Wildlife health Surveillance Database (Event No. 556), a mass mortality event suspected to be associated with drought in Meekatharra, Western Australia, resulted in the death of approximately 3000 red kangaroos (M. rufus). Salmonella was cultured from three animals, one of which had bacteria associated with the intestinal lining. Whilst it is possible Salmonella played a role in the eventual death of this animal, it is likely that dehydration and malnourishment were the primary problems. AWHN also provides reports on wildlife isolates to the NEPSS, which maintains a summary database of Salmonella isolates from wildlife in Australia. This is a valuable resource for Australia. Research Macropods were first suspected of carrying high levels of Salmonella in the 1960’s when it became evident that contamination of kangaroo carcasses in pet meat preparation was a definite risk factor for infection in pets (Anderson et al., 1964). Following a case of salmonellosis in a young infant on Rottnest Island, off the coast of Western Australia (Iveson and Bradshaw, 1973), a significant amount of research was undertaken to investigate whether quokkas (S. brachyurus) were carriers of the organism. It was soon discovered that infection in these small macropods peaked as high as 70-100% in the summer months as a result of disruption to the digestive physiology associated with a decline in feed. No signs of clinical disease were noted (Hart et al., 1985). Whilst studies investigating the natural history of Salmonella in macropods has been largely limited to the quokka (S. brachyurus), it is important to note that these animals are unlikely to be representative of large-bodied macropods on the mainland. Consequently, care should be taken in extrapolating this data. In a prevalence study of Salmonella in macropods (varying species) from Queensland, 51% of animals tested were found to be positive. Thomas et. al. (2001) undertook a similar study, culturing faeces and organs of macropods over a period of twenty years. From the 57 animals sampled, 62 isolates were cultured, belonging to 24 different Salmonella serotypes. Whilst these studies report high levels of infection, it is important to realise that environmental and diet related stress associated with living in captivity is likely to result in a potentially higher prevalence than in macropods in their natural environment (Samuel, 1982; Thomas et al., 2001). For similar reasons, orphaned joeys are considered an occupational risk for their wildlife carers. Under care, joeys often experience stress related to sudden withdrawal from their mother, a change in nutritional diet and unaccustomed exposure to humans and other animals. Between 1981 and 1985, Speare and Thomas (1988) examined orphaned macropod young. Samples were taken from 65 live joeys and 38 dead joeys. A total of 26.8% were Page 4 27/06/2009 found to be infected with Salmonellae spp. whilst 21.7% were actively excreting the bacteria in faeces (Speare and Thomas, 1988). Kangaroo meat intended for human and pet food consumption has been associated with high rates of Salmonella contamination for some time now. Whilst early studies reported contamination rates as high as 44.9% (Suzuki et al., 1967), enforced regulatory standards within the industry have seen this figure decrease significantly. More recent studies have reported contamination rates between 0.84% and 18% (Holds et al., 2008; Eglezos et al., 2007; Bensink et al., 1991). Presence of Salmonella on kangaroo carcasses suggests that natural infection does occur in wild macropods. However, there are no published studies reporting the true prevalence of infection in these animals. Research is currently being undertaken at Murdoch University in Western Australia to determine the prevalence of Salmonella in kangaroos (predominantly M.fuliginosus) in their natural habitat. It is important to draw comparison between the level of natural infection and the rate of carcass contamination. Any significant differences are likely to highlight the need to improve hygiene practices at the processor and evisceration techniques in the field. More extensive studies in all states, comparing the rate of carcass contamination between processors for human consumption and those for pet meat need to be investigated, as different standards exist. Contaminated pet meat is a direct source of infection to household animals, who are then likely to contaminate the household environment. Contaminated pet meat is also a source of infection to household members who handle the food and store it in their own refrigerators. Human health implications In Australia every year, there are approximately 17.2 million cases of gastroenteritis, of which 5.4 million are estimated to have originated from contaminated food. Salmonella is one of the three most common pathogens responsible for foodborne gastroenteritis (Hall and Kirk, 2005). Food products of animal origin are considered to be the major source of human Salmonella infections (OIE, 2008). A number of serovars commonly responsible for salmonellosis have been isolated from kangaroos, including S. ser. Typhimurium, S. ser. Saintpaul, S. ser. Chester and S. ser. Muenchen (National Enteric Pathogens Surveillance Scheme, 2007). At this stage, no confirmed outbreaks of foodborne gastroenteritis have been linked to the consumption of kangaroo meat. There is also an occupational risk associated with salmonellosis. Meat workers may acquire infection from carcasses contaminated during the evisceration process as can individuals working in close association with joeys and kangaroos in captivity. Conclusions Salmonella infections in animals intended for human consumption are considered to be a major source of salmonellosis. Whilst kangaroos have not yet been linked with an outbreak of disease, these animals do present a potential risk of infection both to people and their pets. Despite the prevalence of infection in wild macropods, other than the quokka (S. brachyurus), remaining unknown, the contamination of kangaroo meat suggests that macropods in the wild are capable of harbouring Salmonella. Furthermore, studies have demonstrated that high rates of infection occur in orphaned joeys and captive macropods. Consequently, it is important for all individuals coming into close contact with these animals and their meat products to practice adequate hygiene measures at all times. References and other information Anderson K, Crowder EF and Woodruff P. 1964. The isolation of samonellae from kangaroo meat sold as pet food. Med. J. Aust. 2. 668 - 669. Bensink JC, Ekaputra I and Taliotis C. 1991. The isolation of Salmonella from kangaroos and feral pigs processed for human consumption. Aust. Vet. J. 68. (3). 106-107. Blood DC and Studdert VP. 1999. Saunders Comprehensive Veterinary Dictionary. WB Saunders; London. Brenner FW, Villar RG, Angulo FJ, Tauxe R and Swaminathan B. 2000. Salmonella nomenclature. J. Clin. Microbiol. 38. (7). 2465-2467. Speare R and Thomas AD. 1988. Orphaned kangaroo and wallaby joeys as a potential zoonotic source of Salmonella spp. Med. J. Aust. 148. (12). 619, 622-623. CDC. 2008. Salmonellosis; (Accessed: 12th May, 2009). http://www.cdc.gov/nczved/dfbmd/disease_listing/salmonellosis_ti.html Page 5 27/06/2009 Department of Health and Ageing. 2008. Surveillance systems: NEPSS; (Accessed: April 29th, 2009). http://www.health.gov.au/internet/main/publishing.nsf/Content/cda-surveil-surv_sys.htm Department of Health and Ageing. 2008. Surveillance systems reported in CDI, 2008; (Accessed: 25th June, 2007, 2007). http://www.health.gov.au/internet/wcms/publishing.nsf/Content/cda-surveil- surv_sys.htm Eglezos, Sofroni, Huang, Bixing and Stuttard. 2007. A survey of the microbiological quality of kangaroo carcasses processed for human consumption in two processing plants in Queensland, Australia. J. Food Prot. . 70. (5). 1249 -1251. Gage L. 2002. Hand-rearing wild and domestic mammals Wiley-Blackwell; Australia. Hall G and Kirk M. 2005. Foodborne illness in Australia; Annual incidence circa 2000. Department of Health and Ageing. Hart RP, Bradshaw SD and Iveson JB. 1985. Salmonella infections in a marsupial, the quokka (Setonix brachyurus), in relation to seasonal changes in condition and environmental stress. Appl. Environ. Microbiol. 49. (5). 1276-1281. Hart RP, Iveson JB, Bradshaw SD and Speed TP. 1982. A study of isolation procedures for multiple infections of Salmonella and Arizona in a wild marsupial, the quokka (Setonix brachurus). J. Appl. Bacteriol. 53. 395-406. Holds G, Pointon A, Lorimer M, Kiermeier A, Raven G and Sumner J. 2008. Microbial profiles of carcasses and minced meat from kangaroos processed in South Australia. Int. J. Food Microbiol. 123. 88 - 92. Iveson JB and Bradshaw SD. 1973. Salmonella javiana infection in an infant associated with a marsupial, the quokka, Setonix brachyurus, in Western Australia. J. Hyg. 71. 423 - 432. Arundel JH. 1981. Wildlife diseases of the Pacific Basin - Australia. (Accessed Mason P. 2007. Diarrhoea in Joeys. Healesville Sanctuary; Australian Wildlife Health Centre. (Accessed 15th May, 2009). http://www.wildlifevictoria.org.au/cms/images/stories/docs/diarrhoea%20in%20joeys.pdf National Enteric Pathogens Surveillance Scheme. 2007. National enteric pathogen surveillance system data: Salmonella in macropods. Microbiological Diagnostic Unit; Department of Microbiology and Immunology, The University of Melbourne. OIE. 2008. Salmonellosis 2.9.9; Manual of diagnostic tests and vaccines for terrestrial animals 2008. (Accessed: 2009, 12th May). http://www.oie.int/eng/normes/mmanual/2008/pdf/2.09.09_SALMONELLOSIS.pdf OzFoodNet Working Group. 2007. Monitoring the incidence and causes of diseases potentially transmitted by food in Australia: Annual report of the OzFoodNet Network, 2006 CDI. 31. (4). Samuel JL. 1982. Salmonella in macropods. In: Wildlife diseases of the Pacific Basin and other Countries; Proceedings of the 4th International Conference of the Wildlife Disease Association. Sydney. 61 - 63. Speare R, Donovan JA, Thomas AD and Speare PJ. 1989. Diseases of free-ranging Macropodoidea. In: Kangaroos, wallabies and rat-kangaroos. 705-734. Staker L. 2006. The complete guide to the care of macropods; a comprehensive guide to the handrearing, rehabilitation and captive management of kangaroo species. Lynda Staker; Samuel JL. 1983. Jaw disease in macropod marsupials: bacterial flora isolated from lesions and from the mouths of affected animals. Vet. Micro. 8. (4). 373 - 387. Suzuki A, Kawanishi K, Suzuki N and Takayama S. 1967. A survey of Salmonella contamination of imported meats during 1965 - 1966. Bull. Natn. Inst. Hyg. Sci. 85. 188 - 195. The Center for Food Security and Public Health. 2005. Salmonellosis; Paratyphoid, non-typhoidal salmonellosis. (Accessed: 19th May, 2009). http://www.cfsph.iastate.edu/Factsheets/pdfs/Nontyphoidal_Salmonellosis.pdf Page 6 27/06/2009 Thomas AD, Forbes-Faulkner JC, Speare R and Murray C. 2001. Salmonelliasis in wildlife from Queensland. J. Wildl. Dis. 37. (2). 229 - 238. Winter H. 1957. Salmonella birkenhead from a kangaroo. Australia Veterinary Journal. 33. (3). 67. Updated: 22/05/2009 To provide feedback on this fact sheet The Australian Wildlife Health Network would be very grateful for any feedback on this fact sheet. Please provide detailed comments or suggestions to email@example.com. We would also like to hear from you if you have a particular area of expertise and would like to produce a fact sheet (or sheets) for the network (or update current sheets). A small amount of funding is available to facilitate this. Disclaimer This fact sheet is managed by the Australian Wildlife Health Network for information purposes only. Information contained in it is drawn from a variety of sources external to the Australian Wildlife Health Network. Although reasonable care was taken in its preparation, the Australian Wildlife Health Network does not guarantee or warrant the accuracy, reliability, completeness, or currency of the information or its usefulness in achieving any purpose. To the fullest extent permitted by law, the Australian Wildlife Health Network will not be liable for any loss, damage, cost or expense incurred in or arising by reason of any person relying on information in this fact sheet. Persons should accordingly make and rely on their own assessments and enquiries to verify the accuracy of the information provided. Page 7 27/06/2009
"Salmonella in Australian Macropods FACT SHEET"