New blog on animal health including MRSA

Dr. J. Scott Weese of the Ontario Veterinary College (author of many important papers, discussed in many posts here, on MRSA in food and companion animals) has started a blog on animal-health issues. Here is a recent post on tracking down the source of a MRSA infection when there is a pet in the house.

The blog is called Worms and Germs and I've added it to the blogroll at right.

Much more on MRSA and animals

Again from the 108th General Meeting of the American Society for Microbiology: new findings on the complex interaction of MRSA in humans, pets and food animals.

• From the University of Iowa, the first finding of MRSA in US pigs, on seven farms in Iowa and Illinois. The abstract doesn't say what subtype of MRSA was found, but a new strain of MRSA was found last year in pigs in the Netherlands and both that strain and a known human strain have been found in pigs in Canada. Carriage rates among the Midwestern pigs: from 100% of very young animals to 36% among adult swine. (Poster 983, first author AL Harper)
• From Nicholls State University and two veterinary practices in southern Louisiana, results of screening tests on pets show high rates of carriage of methicillin-resistant Staph species. The pets carried both S. aureus and S. intermedius. (Poster 1017, first author T. Rachal.) For an earlier post on pets harboring MRSA, look here.
• And from the University of Georgia, an analysis of MRSA strains isolated from 50 humans and 60 companion animals (dogs, cats, horses, birds) found the same strains in both: SCCmec type II, a hospital strain, and SCCmec type IV, the main community strain. Human carriage rates: 78% type IV, 22% type II. Animal carriage rates: overall, 40% type IV and 60% type II, but with some important differences between species — all of the cats and birds harbored type II, while the dog isolates were overwhelmingly II and the horses overwhelmingly IV. Of greatest importance, the types did not have identical resistance patterns: In humans, the type IV was sensitive to vancomycin and tetracycline, but the animal IV was sensitive to vanco only, suggesting that MRSA may be evolving differently in its transient animal hosts — an especial concern if the animal-carried strains pass back to humans. (Poster 1027, first author S. Sanchez.)

More on pets and human infections

Another snippet from the International Conference on Emerging Infectious Diseases in Atlanta — again, not about staph, but about the unique role that pets may play in disease transmission:

In the exhibit hall that houses the "posters" (which are just what they sound like: broad swaths of shiny paper printed with graphical presentations of research), there is an intriguing report from West Virgina and the CDC about a novel infection in a cat. The infection is very serious: Corynebacterium diphtheriae, the bacillus that causes diphtheria (the "D" in the childhood DPT vaccine). Diphtheria seldom occurs in the United States — five or fewer cases per year — which is a good thing since it is a horrible disease that causes a membrane to grow across the throat and cut off breathing. It occurs so seldom because humans are the sole host for the disease, and when vaccination renders humans inaccessible territory, diphtheria fades away.

Well, make that: Humans were thought to be the sole host. The report at ICEID describes a pet cat (by the picture, a charming tortoiseshell) who came into a West Virginia veterinary hospital with a very severe ear infection. The infection turned out to be caused by C. diphtheriae that was present not only in that cat, but in a second household cat as well — but not in the cats' two human household members, nor in the eight vet personnel who had been exposed to the cats. Four isolates from the two cats had identical genetic fingerprints, but did not match any C. diphtheria isolates ever analyzed by the CDC.

And this means... what, exactly? It's not not clear how significant a development it is — "More research needed," the CDC says — but it's not good. A disease that was thought to exist only in humans, and thus could be chased out of humans if the percentage of vaccination is high enough, might instead be sustained in humans' environment by another species. And that species just happens to be a very common animal that shares our space very intimately. (Reports that my cats sleep on my pillow are merely vicious rumors. Anyway, it's only during the day.)

If vaccination coverage of the population were perfect, this would not matter: We would be protected anyway. But it's not.

More on pets and staph

I am at the International Conference on Emerging Infectious Diseases, a biannual meeting sponsored by the CDC that is a disease geek's dream of heaven. The days are extremely packed — about 2,000 attendees and presentations every 15 minutes for most of three days — so blogging may be a little light. Lots of MRSA news here though, so there will be a lot to catch up on.

Here's one example: Engeline Van Duijkeren of Utrecht University reported this afternoon on an outbreak of Staphylococcus intermedius, a staph species that colonizes and causes disease in dogs and cats but is rarely found in humans. Between late 2006 and early 2007, the lab at Utrecht received samples for analysis from six animals, all of which had surgery at the same veterinary hospital: five dogs with orthopedic surgery, one cat with abdominal surgery. The samples yielded identical strains of S. intermedius that were all methicillin-resistant — and resistant to a host of other drugs as well, from 3d and 4th generation cephalosporins to clindamycin to tetracycline to Bactrim.

The lab group found the case cluster and the resistance pattern so striking that they looked around for a common source, including among the clinic's veterinary personnel. They swabbed the surgeon, six technicians, two healthy dogs who lived in the clinic, and the local environment. They found the identical strain in the noses of the surgeon, three of the technicians, and one of the house dogs. Conclusion, van Duijkeren said: The humans (who were colonized, not sick) picked up the strain and redistributed it to the animals under their care. It's the first recorded transmission of MRSI between humans and animals.

(Worth noting: A questioner from the University of Pennsylvania, which has done a lot of work on staph in animals, rose during the Q/A to suggest that the hospital was experiencing a clonal cluster of cases that arose independently, rather than a chain of transmission. Oooh, more fodder.)

MRSA and cats - an earlier paper

In journalism, there sometimes arises a situation in which a reporter for a major outlet writes a story that is very similar to one that has already been published by a minor outlet, without crediting the minor outlet. We call it "bigfooting." It's not a compliment.

The flurry of attention to the new letter in the New England Journal of Medicine about a pet cat harboring MRSA and reinfecting the cat's owner has a whiff of bigfooting about it. The letter describes a German family with MRSA that particularly persisted in the wife/mother despite treatment until one of their three pet cats was swabbed and decolonized.

The three authors from the Bavarian Food and Health Safety Authority write, "There is evidence that companion animals, mainly dogs, harbor MRSA, and interspecies transmission has been shown in the members of a family and their dog. This case illustrates that MRSA transmission also occurs between humans and cats." There are five cites appended to the letter, on MRSA epidemiology and sequencing and MRSA in dogs. The inference that this is the first recorded case of cat-human MRSA exchange was picked up by several media outlets: — Associated Press, Reuters — and explicitly stated by HealthDay. com, whose story was carried by the Washington Post.

So, the bigfooting: This isn't the first report of cat-human transmission at all. A very nice paper published in December 2006 in Emerging Infectious Diseases (not NEJM, but not exactly obscure as it is published by the CDC) reports the first isolation of the CA-MRSA strain USA300 from a California cat along with an identical strain in the cat's human. And it shows up close to the top of a Medline search, so it wasn't exactly hard to find.

(There is also a 2005 Veterinary Microbiology paper that reports a PVL+ strain in a cat along with several from dogs, but the researchers didn't type the strains and were unable to say whether they were CA or HA; and two letters in the Veterinary Record in 2004 and 2006 citing multiple MRSAs in cats. Neither draw a direct link to human illness.)

OK, enough truth-squadding. Back to HAI and search-and-destroy soon.