I’ve always been wary of rats, I think it’s safe to say most people are, because of their obvious connection to filth and a history of transferring and harboring disease. I’ve seen rats darting in and out of sewage drains and strolling along subway tracks in NYC, so it’s scary to think they could be one of the reasons behind foodborne illnesses in urban areas.

An article discussing a study done in NYC by Professor Ian Lipkin at Columbia University and his colleagues immediately caught my attention. The study examined and tested for 20 pathogens (15 of them testing positive along with the discovery of 1 known virus) on 133 rats from 5 different locations in Manhattan over the span of 1 year. There has been a lot of research concerning the spread of disease from wild animals to humans, resulting in a “wide-scale microbial surveillance”, especially in the developing world (case in point: fruits bats being the possible cause of the Ebola outbreak). However, there has been far less research on common animals like rats, even though they so often cohabitate with humans. Rats are known to carry diseases, but after finding such a diversity of pathogens, the scientists call for more “pathogen surveillance and disease monitoring in urban environments”, as well as more studies to clarify the possible “risks they may pose to human health.” [Check out the study to see exactly what diseases they found.]

The study notes there are 2.1 million cases of foodborne illnesses each year in NYC and not much data linking rats to spreading foodborne illness to humans, suggesting the possible risk. Although this assumptionis completely correlational, it’s convincing. Norway rats, the most common rats found in urban areas, are not thought to be contributing factors to these 2.1 million cases, but the study offers them as a possible reason because of the lack of data.

I most definitely think there should be more studies exploring this link by conducting randomized experiments in NYC and other major US cities. I think it would be very helpful to test a far greater number of rats and compare the results between cities with different climates and size (that is to say a city like NYC that is very packed together, while Miami and LA are more spread out).

Lipkin and his colleagues are now working with the NYC Department of Health and Mental Hygiene and the CDC “to look for signs of infection from some of the rat pathogens in the blood samples of New Yorkers.” It might be interesting to do an observational study on New Yorkers looking for correlations between a person that has a foodborne illness (along with the frequency at which they they get them) and the areas where they eat out most often and comparing that with which areas of NYC have the highest concentration of rats.

The study mentions that the rats were gathered over the course of 1 year, but fails to explain why this was done, but I think that could be an important factor for future studies. I think it would also be important to take into account what time of year the highest/lowest number of foodborne illness are reported. A list of the 20 “rattiest” cities (Chicago taking #1, NYC #4) was just released and reminds us that “fall is a prime time for rodents to actively seek food, water and shelter”, because of dropping temperatures and the arrival of winter. It seems to me that somehow finding a correlation between a rise in foodborne illnesses and fall weather could be a signal towards a causation of rats on foodborne illness outbreaks in urban areas.

As always, the study’s results could all be due to chance, but the only way to find out is to conduct more studies in more cities, taking more 3rd variables into account, and testing the people.

One last thing, although unrelated, it’s funny to point out… Philadelphia (my hometown) was not on the list of 20 Rattiest Cities, although both NYC and DC are high on the list as #3 and #4 and Baltimore not too far behind placing #9 . I guess “Filthadelphia” isn’t so filthy! (I think I might write a follow-up blog comparing the numbers of foodborne illnesses reported in Philly against those of a “rattier” city of similar size to Philly.)