While dogs are often cited as man’s best friend, rats are like an unwelcome relative that visits too long, damages the furniture and eats all the food.
The history of this common pest is remarkably well-described in the special features of Disney’s movie Ratatouille. It even mentions Alberta’s rat-free status.
There are more than 60 known species of rats, which are classified as rodents. Rodents comprise roughly 40 percent of all known mammals.
Rats are considered to be one of the most successful invasive species and have spread throughout the world to nearly every place humans inhabit, with the exception of Alberta and Antarctica.
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The Norway (brown) rat and the black (ship) rat are the two common pest species in cities. Norway rats are extensively used in medical research, and those with unique colours are prized pets among “fancy rat” enthusiasts.
Rats can survive on many different types of foods and thrive in areas with run-down infrastructure such as urban slums.
The importance of rat infestations is also expected to increase as the world’s population s becomes in-creasingly large and urbanized.
Rats’ impact on agriculture is difficult to accurately measure. They have the ability to destroy crops during production and can contaminate storage facilities, causing massive amounts of grain to be discarded.
Rats also pose a significant health risk to people.
They were famously responsible for Europe’s Black Death, the plague outbreak that killed roughly one-third of the population in Europe. The rat flea carries the bacterium that causes plague. When infected rats die, the fleas find the nearest warm body, which can be a person. The bacterium is transmitted to the new victim when the flea bites, and clinical illness can result.
Rats also carry other important bacteria and viruses that can cause disease in people but have no ill effect on the rodents:
- They have their own type of hantavirus, which is related to the virus in deer mice.
- They frequently carry the bacterium leptospira, which causes Weil’s syndrome, a severe disease of the liver and kidneys.
- Recent studies in Vancouver’s wild rats have shown they can carry a number of important antibiotic-resistant bacteria.
- As the name implies, rat bite fever results when bacteria in the rat’s mouth is introduced into a person’s skin following a bite.
Despite this risk, little is known about the diseases carried by rats in Canada.
The Vancouver Rat Project, led by veterinarian Dr. Chelsea Himsworth, is seeking to answer questions related to urban rat ecology, the diseases they carry and whether people have been exposed.
I’m working on the natural diseases of rats to determine their general health status as part of my training to become a veterinary pathologist.
Rat infestations significantly threaten biodiversity. For example, a number of unique birds and reptiles, including the giant tortoise of the Galapagos Islands that is famous for inspiring Charles Darwin’s theory of evolution, are facing extinction from introduced rats.
Rats are especially good at eating eggs and nestlings, which leads to critical declines in population.
Rat eradication is expensive. For example, millions of dollars have been spent to eradicate rats from Campbell Island, New Zealand.
Risks to health and biodiversity are good reasons for continued funding to keep Alberta rat free and to continue eradication efforts in other provinces.
For more information on the Vancouver Rat Project, visit vancouverratproject.com.
