About the Project

Why are we doing this project?
What are the goals of the Vancouver Rat Project?
Where and when will the project take place?
Why are we studying rats in the Downtown Eastside?
What questions does the project hope to answer?
What rat-associated diseases are being studied?

About Rat-Associated Diseases

Do rats carry any germs that could be spread to people?
What sort of diseases do these germs cause in people?
How can I tell if a rat is carrying a disease?
How could I get a disease from a rat?
Am I at risk?

Why are we doing this project?

There has been little to no research on Canadian rats, the diseases they carry, and how they might affect public health. It is important to understand rats and to find out which diseases they carry so we can know whether rats pose a health threat for people and what can be done to reduce that threat.

What are the goals of the Vancouver Rat Project?

Rats are common in Canadian cities but there is very little scientific information on rats in Canada. The goal of this project is to understand rat populations in Vancouver's Downtown Eastside and to determine whether rats could pose a health risk to people. This will be the first in-depth study of rats in Canada, and we hope that the information generated by this study may be used to decrease the human health risks associated with rats.

When and where will the project take place?

The first phase of the project was a rat ecology study (a study of rat populations). This involved trapping rats throughout the Downtown Eastside (DTES) over the course of one year (September 2011 - August 2012). For the second phase of the project, we will be checking trapped rats for diseases that could be transmitted to people. This phase of the project started in May 2012 and is ongoing. For the third phase of the project, we will try to determine if DTES residents have been exposed to any rat-associated diseases and to identify risk factors associated with disease exposure. This phase of the project started in March 2013 and is ongoing.

Why are we studying rats in the Downtown Eastside?

We are studying rats in Vancouver's Downtown Eastside because high population density (lots of people), older buildings, and being close to the ocean probably make this area attractive to rats and encourage contact between rats and people. Additionally, research in other areas has shown that factors associated with poverty can promote disease transmission from rats to people. However, we recognize that rats are present in other areas of Vancouver and these rats may also pose a risk to human health. Depending on the results of this project, it may be worthwhile to study rats in other areas of Vancouver in the future.

What questions does this project hope to answer?

Due to the unpredictable nature of research, we cannot know what our findings will tell us! However, it is hoped that the data will help us answer most of these questions, and perhaps more:
  • Approximately how many rats are living in the DTES, how are they distributed among the different city blocks, and what are the characteristics of these populations (i.e., most common species, average age, reproductive cycles, etc.)?
  • How do features of the urban environment (e.g., amount of garbage in an alley) influence rat populations? Can we identify specific features of the urban environment that promote or deter rat infestations?
  • Are these rats healthy?
  • Do these rats carry any diseases that could be transmitted to people?
  • How are these diseases spread among rats?
  • Are people in the DTES being exposed to rat-associated diseases?
  • What are the risk factors for rat-to-human disease transmission?

Please visit the Resources page to find out what we have learned so far.

What rat-associated diseases are being studied?

We will be looking for the following bacteria, viruses, and parasites known to be carried by rats in other parts for the world. For example:
  • Seoul hantavirus
  • Yersinia pestis
  • Leptospira interrogans
  • Rickettsia typhi
  • Rickettsia felis
  • Bartonella elizabethae
  • Toxoplasma gondii

We will also be looking for bacteria and viruses that could be carried by rats but have not been studied as extensively as the organisms listed above. These include:

  • Salmonella sp.
  • Escherichia coli (E. coli)
  • Methicillin-resistant Staphylococcus aureus (MRSA)
  • Methicillin-resistant Staphylococcus pseudintermedius (MRSP)

Finally, we will be using a new DNA-based technology called metagenomics, which may allow us to discover new bacteria and viruses that have never been found before.

Do rats carry any germs that could be spread to people?

Rats are known to carry a number of zoonotic microbes, including bacteria and viruses. A zoonotic microbe is one that can be transmitted from an animal to a person. Examples of rat-associated zoonotic microbes include Seoul hantavirus, and the bacteria Leptospira spp., Yersina pestis, Rickettsia typhi, andStreptobacillus monilliforme.

With the exception of plague, most of these diseases are thought to be present in rat populations throughout the world. However, the prevalence of these diseases (i.e., the number of rats that are infected) is known to vary remarkably among cities and even among different locations within a city. For this reason it is important for each city to develop an understanding of its own rat populations in order to judge the health risks posed to people.

Luckily, the distribution of plague is more limited. Most cases of bubonic plague in people occur in Southeast Asia, Africa, and South America. However, other wild rodent species in the USA carry plague, and plague can be spread among distant cities by rodents that 'stow away' on ships. For these reasons it is possible for distribution of plague to expand in the future.

If you would like to know more about rat-associated diseases, please read the summary of our paper 'Rats, Cities, People, and Pathogens: A systematic review and narrative synthesis of literature regarding the epidemiology of rat-associated zoonoses in urban centers.'

What sort of diseases do these germs cause in people?

Most commonly, infection with the aforementioned microbes causes non-specific flu-like illness characterized by fever, chills, headache, nausea, and vomiting. Because of these symptoms can be caused by a variety of different illnesses, and because doctors are often not aware of rat-associated disease risks, cases of rat-associated zoonotic disease in people are often underdiagnosed or misdiagnosed.

In some cases, rat-associated zoonotic disease can be more severe. For example:
  • Seoul hantavirus can cause 'hemorrhagic fever with renal syndrome.' This disease is characterized by fever, bleeding, and renal failure.
  • Leptospira spp. can cause 'Weil's disease.' This disease is characterized by fever, bleeding (including bleeding into the lungs), renal failure, and jaundice.
  • Yersina pestis is the cause of bubonic plague. Bubonic plague is characterized by marked swelling of the lymph nodes (these swollen lymph nodes are the 'bubos' from which bubonic plague gets its name). The bacteria can spread from the swollen lymph nodes to cause fatal septicemia (bacterial infection of the blood).
  • Rickettsia typhi causes 'murine typhus.' This disease is characterized by fever, joint pain, and skin rash.
  • Streptobacillus monilliforme causes 'rat bite fever' and 'Haverhill fever.' These diseases are characterized by fever, joint pain, arthritis, and skin rash.

How can I tell if a rat is carrying a disease?

Interestingly, although rat-associated bacteria and viruses can make people sick, they generally cause no disease in rats. This means that there is no way to tell from the outside whether a rat is carrying a disease that could be spread to people. The only way to tell if a rat is carrying a zoonotic disease is to run specific tests on the rat's blood or tissues.

How could I get a disease from a rat?

There are many ways in which rat-associated diseases can be spread from rats to people. These include:
  • Through contamination of the environment: For example, Leptospira spp. is transmitted through rat urine. This urine can contaminate soil and water bodies. People may become infected with the bacterium when they come into contact with contaminated soil or water.
  • Through contaminated food: Haverhill fever is associated with contamination of raw milk by rat excrement. Also, scientists wonder if rats could transmit Salmonella spp., E.coli, and Campylobacter spp. (all common causes of gastrointestinal disease in people) through contamination of food.
  • Through aerosols (i.e., infectious particles in the air): Once rat excrement is dry it turns to dust that could be inhaled by people. It is thought that this is the main mechanism for transmission of Seoul hantavirus from rats to people.
  • By fleas: Both Rickettsia typhi and plague are spread when fleas feed on an infected rat and then go on to feed on a person. Rat fleas can be found in all sorts of environments and many people are bitten without even realizing it.
  • By rat bites: The aptly named 'rat bite fever' is most spread through rat bites. Although wild rats may bite people, the disease is more commonly associated with pet rats and laboratory rats.

Am I at risk?

For most people, risk of getting these diseases is low. People who have a weakened immune system or people who are often exposed to rats are more likely to become infected.

Have a question that wasn't answered here? Please feel free to contact us!