The not-so Secret Life of Pets

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.

Dog bites

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 hospital visits as a result of being bitten by ‘man’s best friend’ in one year alone. In the US, approximately 1.5% of the population is 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 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 from dogs?

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 ages 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.

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 were obviously provoking the poor hound – pulling its tail, stopping it from 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 of dog bites?

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 infections 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 for a dog bite?

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 clean the wounds thoroughly and then to obtain cosmesis. 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 amoxicillin/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 at 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 restricting ownership of dangerous breeds or dog-free zones do little to prevent attacks.  

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 fewer children would be bitten.

Behavioural psychologists have developed programmes that involve both parent and child 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.

Cat bites

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 by cats?

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 cat 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 of a cat bite?

A much larger percentage of cat bites get infected than dog bites, 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 cats’ 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 that takes 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 for cat bites?

I’ve written before about the possible dangers of toxoplasmosis to the pregnant mother, but there is some data to suggest Bartonella henselae may be linked to an 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 receive prophylactic antibiotics.

Rodent bites

Tim: That’s the most foul, cruel, and bad-tempered rodent you ever set eyes on!
Sir Robin: You tit! I soiled my armour. 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 mouse bites. These are rarely pet-related, but rather the 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, 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 often superficial.  Other rare infections caused by rabbits, such as tularaemia, yersiniosis and salmonellosis, are much more likely to be transmitted by wild rabbits.

Many other diseases are associated with domesticated animals, from allergic conditions to 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, 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

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.

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.

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

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.

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.

Rodents

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.

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

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.