Thursday, January 30, 2014

The usual suspects: Fluffy can make you sick

Large scale livestock production in conjunction with the widespread use of antibiotics to promote animal growth has resulted in the emergence of antibiotic resistant bacteria in farm animals. People who work on and live near such farms are exposed to the resulting pathogens. Smith et al observed that both pigs and the farm workers who raise them in the American Midwest can become colonized with MRSA. Voss et al reported MRSA prevalence among pig farmers that was more than 760 times higher than that among patients admitted to Dutch hospitals. Moreover, a recent study by Carrel and coworkers shows an association between people's proximity to concentrated animal-feeding operations and colonization with MRSA.

These studies, along with many others, illustrate the point that if we blast animals with antibiotics, then we should expect that the environment and people inhabiting it will be exposed to antibiotic resistant pathogens. Recognizing the risks involved, in 2006 the European Union banned the use of antibiotics to fatten farm animals. Denmark went even further and eliminated their use for disease prevention in livestock. In the US, the FDA recently described steps aimed at reducing antibiotic use in agriculture. Hopefully the proposed rules will be adopted and result in decreased use.

I think of the farm and antibiotics issue as being part of a larger thing: the nexus of animal and human health. This idea is often described as "One Health", which recognizes that human, animal, and environmental health are all linked.

And by "animal" we don't only mean livestock. I don't ordinarily think of Staph as a zoonosis, but it is. In fact, several studies have observed human infection associated with companion animals. A review by Day et al highlighted the remarkable spectrum of infectious diseases of dogs and cats that are shared by humans (including Staphylococcus spp.). More recently, Vincze et al described an alarming rate of MRSA in wound samples taken from companion animals in Germany.

It's important to realize that pets get antibiotics, too. Lots, it appears. Writing in 2005, Heuer et al observed that
 . . . a comparatively small number of companion animals (550,000 dogs and 650,000 cats) consume approximately the same amount of fluoroquinolones and cephalosporins as consumed annually in the much larger population of food animals in Denmark (23 million slaughter pigs, 130 million broiler chickens, and 1.2 million cattle and dairy cows). We do not believe that antimicrobial drugs are more generously prescribed for companion animals in Denmark than in other industrialized countries.
This is something that needs to be borne in mind. Overuse of antibiotics in companion animals also carries risks to human health, especially when you think about the frequent contact owners have with their pets.

So the next time Fluffy is feeling down, think twice before asking the vet for antibiotics.

(image source: David Hartley) 

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