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Salmonella in pets the risk to children.


You visit a baby boy at home following a handover from the community midwife. His parents are keen to meet you and chat about their first-born son. You notice a large tank in the living room and on questioning, his parents explain that they keep iguanas, which live in the tank but are able to roam freely around the house. They ask if this poses any risk to their baby and, not knowing the answer to their question, you say you will endeavour to find out.

In 2013 it was estimated that 13 million (45 per cent) households in the UK had pets (Pet Food Manufacturers Association, 2013). Although dogs and cats are the most popular types of pet, there has been an increase in the number of people owning exotic pets in recent years. This may be due, in part, to the 2007 modification of the Dangerous Wild Animal Act (1976), which removed some exotic animals from the list of animals requiring a license if kept as a pet (Dangerous Wild Animals Act 1976 Modification, 2007).

A wide range of infections can be associated with pets, including parasitic, bacterial, fungal and viral diseases.

Human salmonellosis attributable to reptile exposure was first documented in the 1940s, and a large number of case reports have since described zoonotic transmissions of salmonella from reptiles to humans (Hoelzer, 2011). The exact number of reptile-associated salmonellosis cases among humans is difficult to determine, but one study estimated that in the USA reptile exposure is associated with approximately 74,000 human cases annually (Mermin, 2004).


Although the primary source of salmonella infection in humans is contaminated food, it has been estimated that 3-5 per cent of all cases of salmonellosis in humans are associated with exposure to exotic pets, including iguanas, turtles, sugar gliders and hedgehogs (Woodward, 1997). An estimated 90 per cent of all reptiles carry salmonella in their gastrointestinal tract and shed salmonella in their faeces, and around the world a large number of serotypes have been isolated from feral and captive reptiles as well as their eggs. Reptiles carrying salmonella are generally asymptomatic, and clinical salmonellosis is rare.

Treating reptiles with antibiotics to eliminate salmonella from their intestinal tract has not proven to be effective. Doing so increases the risk of emergence of antimicrobial-resistant salmonella strains, and attempts to raise 'salmonella-free' reptiles have been unsuccessful (Bradley, 2013).


Reptile-associated salmonella infection in humans is more likely to present with systemic disease than food-borne infections. After an incubation period of around 12-24 hours, salmonella produces symptoms of headache, fever, malaise, nausea, vomiting, abdominal pain and diarrhoea, which may contain blood. A study by Meyer Sauteur (2013) found that, although reptile-associated salmonella manifested mainly with gastrointestinal disease, 15 per cent presented with invasive disease, including septicaemia, meningitis, arthritis, osteomyelitis and joint disease, and children with invasive disease were significantly younger than those with non-invasive disease.

To determine the association between reptile ownership and salmonellosis, Ackman (1995) reviewed New York State salmonella case reports and conducted a matched case control study. The authors contacted 24 people with selected salmonella serotypes and found that 12 out of 24 case patients owned reptiles compared to two out of 28 controls (matched odds ratio, 6.6; 95 per cent confidence interval, 1.4 to 31.0). Ten of the case patients (but no controls) owned iguanas, and 10 of the 12 case patients were aged six months or under. The reasons for the high prevalence of salmonella among infants and children are not clear but may include biological, immunological and behavioural determinants (Olsen, 2001).

Mermin and colleagues looked specifically at Salmonella marina infection in children in a 12-month period (Mermin, 1997). Of the 32 children infected, 26 (81 per cent) were infants (less than one year of age), compared to children with other salmonella isolates of which only 14 per cent were infants. Of the study group 34 per cent were hospitalised and one died and 28 (88 per cent) of the study group reported iguana exposure, although only four (14 per cent) reported touching an iguana.

A number of human salmonella outbreaks have been attributed to indirect reptile contact. Reptile-associated salmonellosis occurs frequently in small children, who are rarely allowed direct contact with reptiles, suggesting indirect exposure routes. A case control study found presence of reptiles in the home to be a highly significant risk factor for salmonellosis in infants <1 year of age, strongly suggesting a predominant role of indirect transmission (Mermin, 1997). Given the large number of indirect transmissions, the USA Centers for Disease Control and Prevention (CDC) recommends that households with young children (under five years of age) do not own reptiles and that reptiles are not introduced into school settings.


Few reptile owners are aware of the risk of disease. In Mermin's study (Mermin, 1997) only 12 families (43 per cent) realised that the iguana may have been the source of infection, and in another study from USA only 20 per cent of case patients were aware of the association between reptiles and salmonella infection (CDC, 2008). If individuals are unaware of the risk, good hand hygiene, which has been shown to be highly protective in preventing infection, may not be strictly enforced (Friedman, 1998).

There is a zoonosis risk from contact with animals in pet shops. Some families visit pet shops as a leisure activity, where children can see and handle animals, potentially exposing them to disease, even though they do not own a pet. Halsby and colleagues performed a systematic review of the literature and found 57 cases of disease or incidents associated with pet shops or other facilities (e.g. animal shelter, educational organisation) distributing companion animals. The infection described most often was psittacosis followed by salmonellosis (Halsby, 2014).

Evidence suggests that many pet shop employees do not fully understand or control the risks imposed by their pets. Ipsos MORI conducted a poll in 2003 for the RSPCA contacting 300 pet shops selling exotic pets. When asked whether any illnesses may be passed on from the pets to other animals or humans, 48 per cent replied 'No - if take precautions, e.g. hand washing', 36 percent replied 'No--not at all' and 11 per cent said 'Don't know' (MORI, 2003).

It has been shown public education campaigns do work. In USA the Association of Reptilian and Amphibian Veterinarians (ARAV) produces a client education handout with basic facts on how to avoid transmission of Salmonella from reptiles to humans, and in Sweden following the distribution of information based on that produced by ARAV, the number of reported cases of reptile associated salmonellosis decreased significantly (de Jong, 2005).


Reptiles are becoming increasingly common as household pets, and with them comes the risk of reptile-associated Salmonella infections, with infants and young children particularly at risk. Frequently, only a single person in the household is affected and severe clinical manifestations may occur even as a result of indirect contact. Recommendations for reducing the risk of Salmonella to humans from exotic pets (including turtles and tortoises) include:

* Those handling exotic pets should wash their hands thoroughly after both direct and indirect contact

* Aquariums and cages for exotic pets should not be cleaned in kitchen sinks

* Exotic pets should be confined to aquariums or cages and should not be allowed to roam freely in areas occupied by children

* Veterinary surgeons and pet shop owners should give information to potential purchasers and owners about the increased risk of acquiring salmonellosis from exotic pets

* Health professionals should be aware of the risks and when seeing families with small children they should enquire about family pets.


Ackman DM, Drabkin P, Birkhead G, Cieslak P. (1995) Reptile-associated salmonellosis in New York State Pediatr Infect Dis J. 14(11) 955-9

Bradley T, Angulo FJ. (2013) Salmonella and Reptiles: Veterinary Guidelines Available: uploads/2013/03/Salmonella-Information-for-Veterinarians.pdf Accessed 14 July 2014

CDC (Centers for Disease Control and Prevention). (2008) Multistate outbreak of human Salmonella infections associated with exposure to turtles--United States, 2007-2008. Morb Mortal Wkly Rep. 57(3):69-72

de Jong B, Andersson Y, Ekdahl K. (2005) Effect of regulation and education on reptile-associates salmonellosis. Emerging infect. Dis. 11(3):398-403

Friedman CR, Torigian C, Shillam PJ, Hoffman RE, Heltzel D, Beebe JL, Malcolm G, DeWitt WE, Hutwagner L, Griffin PM. (1998). An outbreak of salmonellosis among children attending a reptile exhibit at a zoo. J Pediatr. 1998;132(5):802-807

Halsby KD, Walsh AL, Campbell C, Hewitt K, Morgan D. (2014). (2014) Healthy animals, healthy people: zoonosis risk from animal contact in pet shops, a systematic review of the literature. PLoS One 9(2):e89309. doi: 10.1371/journal. pone.0089309. eCollection 2014

Hoelzer K, Switt A, Weidmann M. (2011) Animal contact as a source of non-typhoidal salmonellosis. Veterinary Research 42:34

Mermin J, Hoar B, Angulo FJ. (1997) Iguanas and Salmonella marina infection in children: a reflection of the increasing incidence of reptile-associated salmonellosis in the United States. Pediatrics 99(3):399-402

Mermin J, Hutwagner L, Vugia D, Shallow S, Daily P, Bender J, Koehler J, Marcus R, Angulo FJ. (2004) Reptiles, amphibians, and human Salmonella infection: a population-based, case-control study. Clin Infect Dis. Apr 15;38 Suppl 3:S253-61

Meyer Sauteur PM, Relly C, Hug M, Wittenbrnk MM, Berger C. (2013) Risk factors for invasive reptile-associated salmonellosis in children. Vector Borne Zoonotic Dis. 13(6):419-21

MORI. (2003) Exotic pets. Available: researchpublications/researcharchive/912/Exotic-Pets.aspx Accessed 14 July 2014

Olsen SJ, Bishop R, Brenner FW, Roels TH, Bean N, Tauxe RV, Slutsker L. (2001) The changing epidemiology of Salmonella: trends in serotypes isolated from humans in the United States, 1987-1997. J Infect Dis 183(5):753-761

Pet Food Manufacturers Association. Available: http://www. Accessed 14 July 2014

The Dangerous Wild Animals Act 1976 (Modification) (No.2) Order 2007

Available: protect/documents/dwa-animallist.pdf Accessed 14 July 2014

Woodward DL, Khakhria R, Johnson WM. (1997) Human salmonellosis associated with exotic pets. J Clin Microbiol. 35(11): 2786-90i


Consultant Paediatrian Child Health

Department, Newbridge Hill, Bath


SpR in Paediatrics, Child Health Department,

Newbridge Hill, Bath


Consultant Paediatrician, Salisbury District

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Author:Finlay, Fiona; Furnell, Carrie; Ridley, Philippa
Publication:Community Practitioner
Article Type:Report
Date:Jul 1, 2015
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