City sickers: How healthy are Chicago's rats?

When talking about our project, we sometimes hear: "are we sure we want healthy rats?"

Although humans do their best to keep rat populations low, we undoubtedly do not want diseased rats living near us. Healthy rats means healthier people.

In order to gauge the public health risks posed by rats, we need to know how often rats carry zoonotic diseases (diseases shared between humans and wildlife). We also need information on the different factors that might influence rates of disease like sex, age, and where the rat was caught.

We receive rats trapped across Chicago by Landmark Pest Management. Then we take measurements, which helps us measure body condition:

 

We then take organ samples to test for Leptospirosis, which is a serious illness transmitted through rat urine, and other bacteria like E. coli and Salmonella

 

Our team collecting biological samples from rats

Once we take the biological samples, the rats are archived at the Field Museum of Natural History, where researchers can examine their genetics and test new questions in the future.

 

Rats preserved in ethanol for future studies

Humans and wildlife can be more likely to develop disease if they are chronically stressed. We wondered if that is also true in urban rats. We are measuring rat stress by analyzing hair samples in our endocrinology lab:

 

Rat hair samples that were washed, dried, and prepared for analysis

 

Ivy Yen analyzing stress from rat hair samples

So, how healthy are Chicago's rats? We have sent off 202 samples to the lab for analysis and we will have our results later this year. We will make them publicly available when they are published. Stay tuned for more updates from our project!