The not-so Secret Life of Pets

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Everyone knows that Australia is one of the most dangerous countries in the world. It houses deadly spiders, snakes and sea life as well as the deadly drop-bear*. But more children are injured by pets every year than any of the native species.

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It would perhaps not be amiss to point out that he had always tried to be a good dog. He had tried to do all the things his MAN and his WOMAN, and most of all his BOY, had asked or expected of him. He would have died for them, if that had been required. He had never wanted to kill anybody. He had been struck by something, possibly destiny, or fate, or only a degenerative nerve disease called rabies. Free will was not a factor.

Stephen King, Cujo

Between 1995 and 2011 there were 28 fatalities due to dog attacks in Australia. According to Flinders University Research Centre for Injury Studies there were 7581 reported visits to hospital as a result of being bitten by ‘man’s best friend’ in one year alone. In the US approximately 1.5% of the population are bitten every year. No doubt a great many more minor cases go unreported. It has been estimated that only 50% are reported to doctors or the police. Up to 43% of dog attacks in children under the age of 10. Unfortunately a large number of these bites occur to the face, nose or lips as children try to kiss, hug or snuggle with them.

Why are children more at risk?

Children seem to be more carefree and less aware of the risks posed by poking dogs with sticks. Because of their small size they are more likely to be attacked than their parents. Boys, between the age of 5 and 9, are more likely to be bitten and the lifetime chance of a child being bitten by a dog is around 50%. (Ed. note – it happened to me so at least one of you is safe.)  Unfortunately it is rarely a stranger’s dog that is the problem. The majority of severe dog bites belong to dogs that are known to the victim.

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As you can see from the above graphic children are more likely to be bitten on the face or upper extremity – it is easy to see why. One Austrian study presents some fascinating data on what the children were doing before they were bitten. Whilst some of them were obviously provoking the poor hound – pulling its tail, stopping it eating, trying to break up a fight – the majority were just playing nearby.

Are some dog breeds more dangerous than others?

Looking at historical data from the US it is plain that pit bulls (American Pit Bull Terrier, American Staffordshire Terrier and Staffordshire Bull Terrier) have been involved in many more fatal attacks than any other breed. They were responsible for 65% of all fatal attacks in 2008 amounting to one person being killed every fourteen days!

Pitbulls were originally bred to be fighting dogs, and used in blood sports such as bull baiting and cock-fighting. When such ‘entertainment’ was banned in 1835 their use in fighting literally went underground as they were used in illegal fighting pits in the coal mines of Staffordshire, England. The dogs were bred for their fierceness and agility.

One must take into account, however, that breed identification, especially when cross breeding has occurred, can be unreliable. Media misrepresentation may add to the confusion.

What is the microbiology?

Although human bites are more likely to cause severe infection (because of the wide variety of oral flora), dog bites are far more common.

Of those people who are bitten by dogs only the smallest number develop severe life-threatening infection as a direct result of the bite. Those that do may well have been infected with Capnocytophaga canimorsus. It is a gram negative, spore forming anaerobe found in the oral cavity of dogs. Immunocompromised patients are most at risk and, as the bacterium can take a week to incubate, may not become profoundly unwell for some time after the initial insult. At this point they will become systemically unwell with fevers, chills and rigors before developing limb necrosis, multi-organ failure and death.

Infection may also be a result of staphylococcus, streptococcus and bacteroides species.

What about rabies?

Fortunately for those of us practising in Australia the nearest we get to rabies is the Australian Bat Lyssavirus and that’s a post for another time.

What is the treatment?

Dog bites can cause substantial soft tissue defects, lacerations and abrasions as well as broken bones and subsequent scarring. Depending on the site that is bitten plastic surgery is often required, firstly to thoroughly clean the wounds and then to obtain cosmesis. In fact, the first partial face transplant was carried out on a woman who was bitten by her pet Labrador. Most cases only require debridement and irrigation followed by a course of amoxycillin/clavulanic acid. In wounds with established infection our local practice is to use piperacillin/tazobactam intravenously.

Do all dog bites need prophylactic antibiotics? A Cochrane review from 2001 suggests not. As is often the case though only 18 trials comprise the database and the control groups (no antibiotics) often had a low rate of infection to begin with so it is difficult to assess the effectiveness of antibiotics. Wounds that are deemed to be of higher risk of infection include deep puncture wounds and those that undergo primary closure.

The injuries are not just physical but mental as well. 50% of children who are bitten enough to require medical attention suffer from a degree of post-traumatic stress disorder (PTSD).

Can we prevent dog bites?

Community based measures such as restriction in ownership of dangerous breeds or dog-free zones does little to prevent attacks.  As we have seen, the majority of cases occur in, or near the family home and involve a dog that is known to the child. Perhaps more effective strategies would involve educating children about appropriate mindful behaviour around dogs. By teaching them to avoid antagonistic behaviours such as pulling tails or fur, hitting or trying to ride on them like tiny horses then less children would be bitten. Programmes that involve both parent and child have been developed by behavioural psychologists and appear to have a degree of success but only in proxy measures such as increased caution and wariness around dogs. It is impossible to tell if such a programme might have an effect on the incidence of attacks unless it was instituted in a state-wide manner.

Young children should be supervised at all times when around dogs, even their own.

 

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The cat dropped the rat between its two front paws. “There are those,” it said with a sigh, in tones as smooth as oiled silk, “who have suggested that the tendency of a cat to play with its prey is a merciful one – after all, it permits the occasional funny little running snack to escape, from time to time. How often does your dinner get to escape?

Neil Gaiman, Coraline

Unlike dog bites, which get reported early, cat bites are often thought of as being less dangerous and so are only reported late when complications occur. They only account for 5 to 15% of all animal bites treated, amounting to about 400,000 cases  per year in the US.

Why do children get bitten and scratched?

If I had to answer it in one sentence I’d say it is because cats are… cats (COI – I’m not a cat person) but it is often because children do not know how to behave around animals and cannot see the warning signs.

The majority of cat bites/scratches occur on the hands (63%) and forearms (23%) with very few reported injuries occurring to the face. Perhaps cats know better than to stay still whilst a toddler is trying to kiss them?

Statistically though the median age of a cat attack is much older, around 38 years of age, and the victim is more likely to be female than male.

Are some breeds more dangerous than others?

If you would care to read the Journal of Feline Medicine and Surgery you would know that Siamese cats are more likely to be aggressive than other breeds and that the majority of attackers are female. These cats probably have owners with only 31% of reported attacks being by strays or feral cats.

What is the microbiology?

A much larger percentage of cat bites get infected than dog bite, in part due to the fact that they often cause deep puncture wounds that are difficult to clean. Whilst the highest point estimate suggests that up to 18% of canine bites become infected, 18 to 80% of cat bites display signs of infection. It is difficult to know how accurate these figures though as we do not know the denominator. Because cats’ teeth are large needles covered in bacteria they can easily penetrate a joint and cause subsequent infection. It’s worthwhile imaging the bitten part to look for a retained fragment of tooth.

The organism that we most have to be worried about in feline bites is Pasteurella multicida.  It is a gram negative anaerobic coccobacillus found in 90% of cat’s mouths. Infection may also be a result of staphylococcus, streptococcus and bacteroides species.

And what of Catch Scratch Disease – an illness deemed so important that Motorhead sang about it (a cover of the Ted Nugent original). Bartonella henselae causes an indolent infection taking several weeks to appear. What starts out as a small localized pustule at the site of the scratch can lead to painful massive lymphadenopathy. It normally self-resolves but can be much more severe in the immunocompromised host.

What is the treatment?

I’ve written before of the possible dangers of toxoplasmosis to the pregnant mother but there is some data to suggest Bartonella henselae may be linked to increased incidence of depression. If you want to further the conspiracy theory that cats control their owners then this paper is a worthwhile read.

Again careful wound care is important but as cat bites are much more susceptible to infection they should all probably received prophylactic antibiotics.

 

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Tim: That’s the most foul, cruel, and bad-tempered rodent you ever set eyes on!
Sir Robin: You tit! I soiled my armor I was so scared!
Tim: Look, that rabbit’s got a vicious streak a mile wide! It’s a killer!

Monty Python and the Holy Grail  (1975)

Not many children get brought to the emergency department because of rodent bites.  US surveillance data suggests that only about 2.4% of animal bites in children are a result of rat or mice bites. These are very rarely pet related but rather the a result of the James Herbert-esque swarms that hide beneath our feet.  Around 1.2% of reported bites come from family favourites – gerbils, hamsters, guinea pigs and rabbits.

The organisms are the typical oral flora so include Streptobacillus monoliformis or Sprillum minus which may lead to Rat Bite Fever. After an incubation period of up to four weeks victims may fall foul of fever, rash and septic arthritis and possibly infective endocarditis.

Rabbit scratches and bites, with the exception of the Killer Rabbit of Caerbannog, only cause infection about 10% of the time as they are generally superficial.  Other rare infections caused by rabbits such as tularaemia, yersiniosis and salmenellosis are much more likely to be transmitted by wild rabbits.

 

Many other diseases are associated with domesticated animals from allergic conditions, parasitic ones and some very rare ones but this article concentrates only on those that may be associated with bites and scratches. If you have experience managing other domesticated animal bites then please feel free to recount your experiences in the comments section below.

In general all bites, whatever the attacker, should be thoroughly cleaned and irrigated.  Tetanus prophylaxis should be offered depending on immunisation status and consideration should be given to prescribing antibiotics.

*Go on, Google them.

References

Dogs

Gilchrist J, Sacks JJ, White D, Kresnow MJ. Dog bites: still a problem?. Injury prevention. 2008 Oct 1;14(5):296-301.

Schalamon J, Ainoedhofer H, Singer G, Petnehazy T, Mayr J, Kiss K, Höllwarth ME. Analysis of dog bites in children who are younger than 17 years. Pediatrics. 2006 Mar 1;117(3):e374-9.

Bini JK, Cohn SM, Acosta SM, McFarland MJ, Muir MT, Michalek JE. Mortality, mauling, and maiming by vicious dogs. Annals of surgery. 2011 Apr 1;253(4):791-7.

Wilson F, Dwyer F, Bennett PC. Prevention of dog bites: Evaluation of a brief educational intervention program for preschool children. Journal of Community Psychology. 2003 Jan 1;31(1):75-86.

Cats

Talan DA, Citron DM, Abrahamian FM, Moran GJ, Goldstein EJ. Bacteriologic analysis of infected dog and cat bites. New England Journal of Medicine. 1999 Jan 14;340(2):85-92.

Dire DJ. Cat bite wounds: risk factors for infection. Annals of emergency medicine. 1991 Sep 30;20(9):973-9.

Palacio J, León-Artozqui M, Pastor-Villalba E, Carrera-Martín F, García-Belenguer S. Incidence of and risk factors for cat bites: a first step in prevention and treatment of feline aggression. Journal of Feline Medicine & Surgery. 2007 Jun 30;9(3):188-95.

Rodents

Rabinowitz PM, Gordon Z, OdoFin L. Pet-related infections. American family physician. 2007 Nov 1;76(9).

Plaut M, Zimmerman EM, Goldstein RA. Health hazards to humans associated with domesticated pets. Annual review of public health. 1996 May;17(1):221-45.

Steele MT, Ma OJ, Nakase J, Moran GJ, Mower WR, Ong S, Krishnadasan A, Talan DA. Epidemiology of animal exposures presenting to emergency departments. Academic emergency medicine. 2007 May 1;14(5):398-403.

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About 

An Emergency Physician with a special interest in education and lifelong learning. When not drinking coffee and reading Batman comics he is playing with his children.

@andrewjtagg | + Andrew Tagg | Andrew’s DFTB posts

Author: Andrew Tagg

An Emergency Physician with a special interest in education and lifelong learning. When not drinking coffee and reading Batman comics he is playing with his children.

@andrewjtagg | + Andrew Tagg | Andrew’s DFTB posts