Monday April 14 2008
“Beware of the dog: you may catch MRSA”, warns The Times today, going on to say that letting a dog lick your face, picking up its faeces or allowing it to sleep on your bed could put you at risk of catching salmonella, campylobacter or MRSA. The newspaper adds that the risk of infection from dog to man is low, and that the researchers behind this study do not wish to create a scare, particularly considering the benefits that owning a dog can have on health.
This controversial study has, according to the news story, irritated dog lovers. One said that you are more likely to catch a disease from a child and another that the study has told us nothing but to use a bit more common sense.
The study behind the story has nothing to do with the link between the behaviour of dogs and their owners and disease. It simply describes the patterns and habits of dog owners in Cheshire. Though the researchers discuss the potential link between some behaviours and disease, this is not based on findings from their survey. Further studies are needed to see whether there is any link and whether particular behaviours are truly high risk.
The basic message is a good one: maintain at least a basic level of hygiene, particularly when handling dog faeces.
Where did the story come from?
Carri Westgarth and colleagues from the University of Liverpool and the University of Bristol carried out the research. The study was funded by the Department for Environment, Food and Rural Affairs (Defra) and published in the journal The Veterinary Record.
What kind of scientific study was this?
The study is a cross-sectional survey of 260 dog-owning households (owning 327 dogs) in a community in Cheshire, England. The researchers were interested in describing the nature and frequency of contact between pet dogs and their owners or other people. Particular focus was given to contact that might be associated with a risk of the transmission of pathogens (small organisms, such as viruses or bacteria that can cause disease) that are known to be transferable from animals to humans (called zoonoses).
Through a previous doorstep survey in Cheshire, the researchers identified 260 dog-owning households that were then invited to complete a questionnaire. The main person who performed dog duties was asked to complete the questionnaire. Participants were encouraged to complete their questionnaires by offers of money-off vouchers for dog food and local boarding kennels.
The questionnaire was designed to investigate behaviours that might have the potential for zoonoses to be transferred, such as where the dog sleeps, its health and diet, and how it behaves with other people and dogs.
Using the responses from the questionnaires, the researchers investigated whether there were any relationships between the frequency of “contact behaviours” (i.e. the dog lying on furniture or a person’s lap, jumping up at household members, frequency of walks, etc) and the size of the dog (i.e. toy/small, medium, or large/giant).
What were the results of the study?
Questionnaires were returned for 85 per cent of the dogs. There were multiple questions on the dogs and their owner’s behaviour. Some of the results include:
- When fed, 79 per cent of dogs ate in the kitchen, with the most popular food being dry complete commercial dog food. Raw meat was never given to 83 per cent of dogs. Six per cent of the dogs sometimes or often found and ate raw carcasses, 25 per cent rolled in them, and six per cent sometimes found and ate dog faeces. Eighty four per cent had visited a vet in the last year, four per cent because of vomiting and/or diarrhoea.
- The most common sleeping place for the dog was the kitchen (42 per cent), 19 per cent slept in the bedroom and 14 per cent on a human bed.
- Common dog behaviour when interacting with household members included sniffing, nudging with the nose, jumping up and licking hands.
- Outside the house, 76 per cent of dogs often or sometimes interacted with other people, while a different question showed 76 per cent of dogs interacted with other dogs. Common behaviour with other dogs included being playful (59 per cent), sniffing (81 per cent) ignoring (42 per cent) and aggression (24 per cent).
- Sixty two per cent of owners removed faeces from the garden every day, one per cent never removed them and three per cent removed them less than once a week. Seventy per cent of owners used plastic bags to dispose of the faeces, while 91 per cent used them on a walk. Shovels were used at home by 42 per cent of dog owners.
- Asked whether they washed their hands after picking up faeces, 96 per cent said they did so always or usually. When asked whether they washed their hands before eating, 85 per cent said always or usually, while 58 per cent said they did so after touching a dog.
What interpretations did the researchers draw from these results?
The researchers concluded that dog-dog interactions and dog-human interactions were highly variable and depended on the household, the sex, size and age of the dog, and owner preferences.
They said that the preferred sleeping place, the kitchen, could “be considered a risk for the transmission of zoonotic disease”.
The researchers discuss other behaviours that could increase the risk of disease transmission, e.g. having dog food near human food, dogs eating faeces, dogs sleeping on their owner’s bed or sharing furniture, sniffing and licking hands and faces, playing fetch games, giving treats, not washing hands after picking up faeces, dogs coming into close contact with other dogs and whether the dog was taken to the vet often.
What does the NHS Knowledge Service make of this study?
This study – being a cross-sectional survey of dog owners – has little to do with the subject of disease transmission. It was not set up to investigate whether any behaviour (of owners or their dogs) are actually linked to an increase in disease. The nature of the questionnaire and the study design mean that the researchers cannot associate any dog or owner behaviour with zoonoses.
In actuality, the researchers are merely describing the habits and patterns of dog owners in the Cheshire area and, drawing on other literature, they suggest that particular behaviour might be associated with an increased risk of infection.
Though the findings do not necessarily dictate it, the message to be taken away from this study is an important one grounded in common sense: maintain basic levels of hygiene, particularly when handling faeces.
Sir Muir Gray adds...
Human beings are still a greater risk.