ASSESSING THE PREVALENCE OF SALMONELLA IN WILD & CAPTIVE REPTILES

Collecting a swab sample from a Yellow-bellied Water Skink (Eulamprus heatwolei).  Photo: F. Scheelings

A zoonosis is a disease that can be transferred from animals to humans.  Reptiles are increasingly popular as pets, both in the USA and Australia, and many species of reptiles pose significant zoonotic risks for people in contact with them.  Zoonoses often also affect the health of the infected reptile, but have been poorly studied in most Australian reptiles.

At Healesville Sanctuary, some reptiles that pass through the Australian Wildlife Health Centre are tranferred to captive collections either at Zoos Victoria or other institutions.  Therefore there may be a high risk of diseases being introduced to captive populations from wild populations as well as human exposure to zoonoses.

Salmonella is a genus of enterobacteria.  Salmonella infections are zoonotic and sometimes cause severe illness.  Dr Franciscus Scheelings, together with other researchers and veterinarians from Zoos Victoria, investigated the prevalence of Salmonella in wild and captive reptiles.

AIMS

1. To assess the relative prevalence of Salmonella in wild and captive reptiles. 
2. To develop a list of husbandry recommendations to reduce the rate of Salmonella infection in captive reptiles.

METHODS

Wild reptiles were sourced from animals trapped at Cape Conran, East Gippsland, and from animals that passed through the Australian Wildlife Health Centre at Healesville Sanctuary.  The reptile collection at Healesville Sanctuary was used as a source of captive animals. 

The colonic mucosa was sampled by swabbing the cloaca of each animal.  Samples were then incubated and cultured under aerobic conditions.  Samples were considered positive for Salmonella if the urea result was negative and the triple sugar ion slants produced hydrogen sulfide.

Definitive diagnosis and serotyping was done at the Microbiological Diagnostic Unit at the University of Melbourne. 

Statistical comparisons between groups for the prevalence of Salmonella organisms were performed using Fisher’s exact test.

RESULTS

More than 500 individuals (comprising four families and 57 species) were sampled for the presence of Salmonella between January 2007 and June 2008.  Salmonella was identified in approximately one quarter of the animals tested.  The rate of Salmonella infection was relatively low: shedding rates of up to 90% have been documented in reptiles. 

Significantly fewer wild reptiles were Salmonella-positive than captive reptiles.  The majority of captive snakes species were positive for Salmonella, and Salmonella Para B bv Java 3b var was the most common isolate.

PROJECT OUTCOMES

This research suggests that captivity predisposes Australian reptiles to excrete Salmonella.  This may be influenced by factors such as hygiene and diet.  Further research is needed into the role of diet in Salmonella infection in Australian reptiles, and methods that can be used to eliminate infection.

FOR MORE INFORMATION

- on this research project - click here to email Dr Franciscus Scheelings (Principal Investigator).

- on the Australian Wildlife Health Centre - click here.

- on zoonoses, see:

• Ackerman DM, Drabkin P, Birdhead et al.  (1995).  Reptile-associated salmonellosis in New York State.  Pediatr Infect Dis J (14): 955-959
• Johnson-Delaney CA.  (2006).  Reptile zoonoses and threats to public health.  In: Reptile medicine and surgery.  2nd ed., p. 1017-1030, Ed. Mader DR, Missouri: Saunders Elsever