Salmonella: Transmission from Pet Reptiles

Zoonoses or Zoonotic diseases are those that can be transmitted between humans and animals. Salmonella is a zoonosis from pet reptiles that I am asked about on a fairly regular basis, and usually relates to the risk associated with reptile pets and Salmonellosis in humans. Whilst reptiles, amphibians and many other exotic pets can and do transmit Salmonella infection from time to time, sensible hygiene precautions can generally prevent this occurrence. Other precautions are recommended such as refraining from buying wild caught animals which are more likely to be infected, but also may be stressed and debilitated leading to enhanced shedding of infective material. Similarly, buying pet reptiles from clean, professional outlets or breeders may also reduce the risk of acquiring an infected animal in the first place due to decreased chances of transmission between animals where hygiene and cleanliness are scrupulous. Many different Salmonella species and serovars have been isolated from reptiles commonly kept as pets, several of which are infectious to humans.

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The difficulty in assessing infection risk from reptile pets lies in the fact that certain Salmonella spp. can be commensal organisms in the gastrointestinal tract of pet reptiles, and also in that they are often intermittently shed so even if screening faecal samples it can be difficult to ensure a pet reptile is Salmonella free. Pets can appear perfectly healthy with no outward signs of infection yet carry a pathogenic strain that could result in severe illness in humans. Transmission to humans is usually via the faecal oral route, and as such any contact with faecal material should be minimised. Hygiene precautions such as washing hands after handling animals, wearing gloves for cleaning reptile housing and for maintenance of aquatic environments and filtration systems are the best defence against infection. Salmonella bacterial cells have been demonstrated to survive and remain infective in the environment for long periods of time, up to 6 months in dried reptile faeces and up to 6 weeks in contaminated aquarium water. Therefore, indirect transmission from the environment to oral ingestion can also be a significant route of infection in homes with reptile pets, particularly where cleanliness and hygiene practices are poor.

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Signs of infection in humans include diarrhoea, vomiting, lethargy, abdominal cramps/pain, fever and in severe cases dehydration or even septicaemia and death. The most serious risk for infection is in young children, the elderly and immunocompromised individuals. One of the issues which comes up from time to time in the media, is whether reptiles and amphibians are suitable pets for children in the first place. This debate raged most notably in the 1980’s and early 1990’s when thousands of baby terrapins were being sold to young children in the UK and USA during the teenage mutant ninja turtles craze, resulting in several high profile cases of Salmonellosis in children. Several more recent high profile outbreaks in the USA have linked Salmonella outbreaks in children to aquatic frogs sold for home aquaria.

Transmission can be increased in young children for a variety of reasons, mainly due to not washing hands after handling pets or putting their hands in faecal contaminated water and then touching their mouths. Immunity in young children is also underdeveloped compared with healthy adults so transmission risk is again increased. As such, it is prudent to advise against aquatic pets such as turtles and frogs for young children for safety reasons as much as for the fact that these are specialist pets requiring detailed care and environmental conditions. In a household with very young children that would not understand these precautions, it may be better to limit access to such pets or consider waiting until children are a bit older to allow interaction with them. Similarly, it may be worth re-homing pet reptiles or amphibians if there is a member of the household who is on immunosuppressive medications like steroids or chemotherapy agents, or those with immunocompromising conditions. The alternatives would be rigorous and regular testing to screen for Salmonella spp, recognising that several tests are needs to rule out the disease and also that strict biosecurity will have to ensure infection is not introduced. This could potentially be very difficult to achieve especially considering some outbreaks of pathogenic Salmonella have been traced to rodent or insect food items required for many captive reptile diets.

If keeping reptiles or amphibians in the home with children it is crucial to teach them the importance of good hand washing after handling any animal, not just exotic species. Supervised handling if at all should be encouraged. Cleaning of reptile housing and equipment should never be carried out in areas where food is to be prepared, or drinking water is sourced or even in showers and baths used by the household. Preferably these tasks should be carried out outside the home or in a dedicated sink or washing facility. Cages or tanks housing exotic pets should be cleaned and disinfected with an appropriate disinfectant at the correct concentration on a regular basis. This is especially important for aquatic species who obviously occupy faecal contaminated water and therefore often have a higher potentially pathogenic load of gastrointestinal micro-organisms than other species.

In summary, perhaps reptile and amphibian pets are too great a risk for certain households depending on what practical arrangements can be made to limit risk of infection to vulnerable individuals, particularly young children. It is important to be aware however that with sensible hygiene precautions such pets pose a very low risk and incidence of disease transmission from pets to owners is greatly exaggerated by the media when occasional cases occur. Any signs of gastrointestinal illness in households containing such pets should be investigated by a medical doctor, especially in the vulnerable groups discussed. It is important to also mention that gastroenteritis caused by Campylobacter spp is also sometimes transmitted by captive reptiles and amphibians, and can cause similar signs.

Bibliography:

http://www.arav.org/wp-content/uploads/2013/03/Salmonella-Information-for-Veterinarians.pdf

http://www.apsu.edu/files/iacuc/Zoonoses-fish-reptiles-amphibians.pdf

http://www.cfsph.iastate.edu/Factsheets/pdfs/reptile_associated_salmonellosis.pdf

http://www.eurosurveillance.org/images/dynamic/EE/V15N22/art19581.pdf

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1297927/pdf/11285792.pdf

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One thought on “Salmonella: Transmission from Pet Reptiles

  1. Dear exotic pet vet,
    You have written one of the most balanced and sensible articles about reptiles and salmonella on the Web. All too often we find articles exaggerating the risk, particularly from the anti-captivity camp. Finding an article that presents the information in a more down-to-earth way is encouraging.
    But people must not associate salmonella with reptiles only. As you pointed out, salmonella infects many other animals. Fish can have it, some small mammals, some amphibians, even dogs and cats and humans in a small percentage of the population. And we must not forget that most foodborne cases come from chicken, so the logical endpoint is that chickens and other birds are infected as well, and with no outward symptoms. Why no one hears about infection in birds?
    But the main topic of my comment is more about children and reptiles. I believe if sensible precautions are taken, they can coexist. If you wash your hands whenever handling reptiles or the insides of their enclosure, clean there feces, limit where they roam when children are in the house, maintain enclosures secure and supervise handling by children if done at all, you are most probably safe. I know some reptile hobbyists with families, and I have read about too many others in internet forums having children and reptiles with no problems with the above precautions. Some didn’t follow them so rigorously, something probably not good, and still got no problem. On the other hand most infections, at least those making the headlines, seem not to affect reptile hobbyists or other people knowing the risk, but usually unsuspecting people getting for example a turtle for their two-year old child. The biggest problem in that action is I believe the buying of animals for so young children. No animal must be bought for so young a child, which still doesn’t even know what it is, let alone can care of them.
    Furthermore, those outbreaks you mention, like that of aquatic frogs in the US or that with the bearded dragons later, usually affect one supplier only, are caused by one or a few only strains of salmonella, and are usually associated with newly purchased animals, but unfortunately the negative publicity affects the species and its keepers as a whole. For that reason, when buying reptiles, I prefer hobbyist breeders first, and larger breeders or specialized stores second, because I know those animals are much more healthy. I would never by one from a common pet store or any other venue not specializing in reptiles. Captive-bred is the only option. I believe wild-caught animals must be reserved for breeders or serious hobbyists, either to introduce new blood in the captive population, or to breed a rare in the hobby species.
    Also, having to send reptiles away of the home when children are born will create a huge logistic problem, as most of these animals are long-lived, and there aren’t many people that will care for them temporarily. Then the hobby will be impeded. Also, this practice contradicts the widely circulating moral message that pets must be cared for the duration of their natural lifespan.
    Also this obscession about reptiles and salmonella has started making an impact in the public sphere. Nowadays reptiles are less presented to the public, less are kept in schools, less programs presenting reptiles to children exist, generally they are hidden from view, like something dangerous.
    In a discussion with a hobbyist that had many species for many years, who also was following all these news headlines, he said to me that all this hysteria happens due to reptiles being in the acceptance phase yet. I don’t know if they will be finally accepted as legitimate pets and as normal animals like others, but similar disease panics have happened in the past for other animals. He told me as an example the warning about pregnant women and cats, or the warnings about immunocompromised people and every animal, which nowadays have been moderated a lot. We hope the same will happen towards reptiles, that people will be educated about the true risk and take the sensible precautions, and no more blancket statements to be issued from authorities, like ban reptiles from all homes with young children, ban all reptiles from schools, etc.

    I believe a part of the problem is based on the finding of scientific and epidemiological research, which isn’t always unbiased as with any research, but a large part of it is much older, having a centuries-old tradition, which, in our medical and scientific era, has worn the medical cloak. It is the archetype of the lowly, evil, filthy reptile crawling literally and figuratively in dust, soil and excrement. Reptiles, as well as amphibians, arachnids, insects, some worms, mollusks and some nocturnal or small mammals in a lesser extent, have been maligned by many cultures throughout history, and have been ascribed with all sorts of evil traits and abilities, like evil, enemies of humanity, cold, poisonous, bearing bad luck, etc. Disease carrier is one of this negative traits. There are traditions throughout the world that link reptiles and amphibians to several diseases, most of which are either unrelated to them or non existent. Toads for example cause warts, the urine of tortoises causes the same, house geckos are poisonous and cause sever dermatological disease, even leprosy, can kill if eaten or if they bite, etc. I believe most of the fuel for the anti-reptile sentiment today comes from the remnants of those traditions. Although we may not believe in these things today, still a distrust and reluctant attitude towards reptiles, if not outright disgust and fear, is pervasive in a large sector of the population. Reptiles must be regarded as normal animals, that I believe is the start of making them acceptable and their risk put into perspective.

    Ps 1. When I was young, I was spending every summer catching various reptiles (geckos, lizards, tortoises), frogs toads, tadpoles, crayfish, large insects, hedgehogs, and playing with cats and chasing chickens. All of these animals, apart probably from the invertebrates and the cats in some extent, were high-risk salmonella carriers. I learnt to wash my hands from a young age, but, as a child playing outside, I sometimes didn’t do it. I remember for example catching some fire-bellied toads, dipping my hands in the mucky river water, then after a half hour, eating some cherries straight from the tree. Neither my parents nor myself remember of any gastrointestinal illness associated to those activities. On the other hand, I remember severe and debilitating gastrointestinal illnesses in fall and winter, when we congregated in schools, and all children got them, probably from a virus. Too many other hobbyists, though not all, started to cultivate an interest in reptiles from a young age. We all caught them, sometimes we were scratched, bitten or doused with toxic secretions, but miraculously we came out all unscathed. If we shelter children from contact with reptiles, and allow them to watch them from afar, on a screen in the comfort of their chairs, how they will have an interest in reptiles, and generally in animals and nature later? Later then I had some red-eared sliders, and after that we learnt about salmonella, but no one panicked. Just we washed our hands after handling them and poored the old water away more carefully. Unfortunately I didn’t know how to care for them correctly, and they died. An embarrassing page of my life. Now I have a crested gecko, a bearded dragon, a pac man frog, and my rabbit, but now I know how to care for them correctly and they are in excellent health. Now the only thing distressing me is the ongoing attacks on our loved hobby. If you wonder how I found tortoises, geckos and fire-bellied toads, I am from Greece, so these animals are native here. If you want any information about wild tortoise habits, so to enrich their captive life, I can help.
    Ps 2. Has anyone in the whole of your practice abandoned reptile keeping due to salmonella fear, gave the reptile away due to child, got himself or a child in the home salmonellosis proven to come from the reptile, or kept reptiles with children successfully? And what precautions he or she was taking for the latter?
    Thank you very much. I am waiting for a reply.
    Kind Regards,
    Stefanos

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