Rats!

Rats!

“I hope you don’t have a weak stomach,” Chris said as we stepped out of the truck and into the alley. It was my first day in the field with the City of Boston’s Inspectional Services constables. We were checking the city’s rat traps in a particularly problematic area not far from Newbury Street. Out of the corner of my eye I saw a rat scurry down a hole in a wall. Snapping on some nitrile gloves, I grabbed my cooler and got to work collecting specimens. Later that morning I would drive the specimens back to the lab in Grafton to necropsy and swab them for bacteria. My goal: to determine whether Boston’s rats are carrying methicillin-resistant Staphylococcus aureus (MRSA) and, if so, whether they are also shedding it into the environment in their feces. MRSA is a leading cause of refractory skin and soft tissue infections, particularly in homeless populations, and poses a considerable burden to the U.S. healthcare system.

When I try to explain this project to other people I’m met with expressions of concern, interest, and sometimes disgust. My fascination with the intersections between human and animal health was what drove me to pursue a dual DVM/MPH degree, and in my mind there is perhaps no wild creature whose existence is more intertwined with humans than the Brown Rat. As a future veterinarian, I’ll admit that this project presented a slight conflict: I couldn’t sample live rats. Even if I could, what neighborhood would possibly allow me to release rats back onto their streets?  Through some outreach and good luck I was able to partner with a local pest control company and the City of Boston, both of whose support I am incredibly grateful for.

Partnering with the city

If you’ll permit me a quick aside, I want to reiterate how fantastic the City’s Inspectional Services division was. Half way through the summer and struggling to obtain samples, I reached out to the city in hopes that maybe they could help me out. Sitting across from Leo, the Assistant Commissioner, I made my case, which must have sounded bizarre: “I’d like some dead rats for my research please” (okay, it was a little more nuanced than that). Leo never even batted an eye, he promised his full support and introduced me to two of his best inspectors. The next thing I knew I was on the road with Chris and Brian, both of whom went out of their way to help me reach my sample size. Not only did I have a blast working with them, but they taught me a ton about the city, and gave me an appreciation for all the work they do to keep city residents safe and healthy.

The research

White Image #2I have an interest in bench top research, so one of my personal goals this summer was to develop my lab skills. For this reason I chose to run all my own lab work, which was admittedly labor intensive and also a lot of fun. Using methods learned in Dr. Jean Mukherjee’s microbiology course I was able to isolate, subculture, and identify my bacteria. After that I subjected my colonies to antimicrobial sensitivity testing to determine what drugs they were resistant to. The final step, which I’m still troubleshooting, was to run a PCR assay to confirm my results and identify the presence of a novel methicillin-resistance gene, yet to be identified in the United States. My hope is that the findings from my small project may help contribute to our collective understanding of how antimicrobial-resistant genes spread globally.

The results

Ultimately I found that Boston rats do indeed carry MRSA at a rate higher than previously seen in similar studies in Vancouver and Tokyo. I also found that rats are carrying the bacteria in their noses and shedding it in their feces, but there does not appear to be a statistically significant association between these two occurrences. Most interestingly, I found resistance to 15 of the 18 antimicrobial drugs tested for. I always like to point out that (to my knowledge) no one is treating these rats with antimicrobials, so this resistance must come either from environmental exposure to drugs or resistant bacteria from another species. The implications of this are fascinating and disturbing when you think about the pharmaceuticals we excrete and dispose of through the sewer system, as well as the waste we put in our dumpsters.

This project was everything I hoped for, it was fun, challenging, rewarding, and I learned an incredible amount. I’m excited to know that my mentor, Dr. Marieke Rosenbaum, has received funding to broaden the work to investigate other pathogens and their geographic distribution. Another professor once told me: “it’s a wormy germy world out there”. It’s no surprise that humans and other species interchange pathogens on a daily basis. However, in a world with disappearing green space, and increasing immunosuppression, public health veterinarians have their work cut out for them. In my mind it’s neither practical nor ethical to eradicate wildlife because we perceive them as a threat. Instead, we must better design our infrastructure and be good stewards of our pharmaceuticals. As veterinarians our greatest challenge will be to advocate for animals while keeping humans healthy, I know we can do both.

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