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Thursday, 23 April 2015

Rats in the city

The Uninvited Guests - Rats

     by Jim Chan.

News update Feb. 15, 2017: 

Leptospirosis kills one and strikes two others in New York

ratsImage copyrightISTOCK
Image captionRats are a common sight in New York City, but disease outbreaks are rare

One person has died and two others have been stricken by an outbreak of leptospirosis - a rare bacterial infection commonly spread by rat urine.
New York City health officials have identified the cases - all on one city block in the Bronx. Each of the three patients was admitted to hospital severely ill with acute kidney and liver failure. City officials say the cases, occurring in the past two months, are the first such concentrated cluster. Full article: Leptospirosis - Killed one and two hospitalized in New York City BBCReposting from

The Uninvited Guests - Rats

Looking back at over 36 years of my career as a public health inspector, I have many encounters with critters like rats, mice, cockroaches and other “uninvited guests” in food
premises during inspection and investigation. I admit that after years of working as a public health inspector, I am still trying to figure out what’s going on in the society of rats? Do rats actually have a sense of social behaviour like us? 

Rats are troublesome and damaging pests in homes and in the food industries. They are not fussy eaters and they eat a variety of foods, including food that we stored in kitchen cupboards or pantry. They can contaminate food with the wastes such as droppings and urine that they leave behind, and can lead to food poisoning such as Salmonella and E.coli. 

Rats can also damage structures and property and thrive in a wide variety 
of conditions and environments. Rats are often found in and around homes, buildings, food establishments such as restaurants, supermarkets, shopping malls, food storage warehouses. Rats also found on farms, in gardens and open fields causing damages to local food crops.

Toronto Public Health reports a 50% increase in rodent-related complaints as compared to records collected in the same period in 2015. (Toronto Star's article Rat related complaints on the rise in Toronto).

Ever heard of the term 'You dirty rat!'

According to the Journal of Medical Entomology ''A team of scientists including entomologists, virologists, and immunologists trapped 133 Norway rats in Manhattan over a
 10-month period and recorded the insects, arachnids, and pathogenic bacteria associated with the rodents. About 6,500 parasites were found on the rats, including several mite species, a louse species, and rat fleas. The researchers did find a few different bacterial species from genus Bartonella, which can cause disease in humans, but they detected neither the plague bacterium nor the bacteria that can cause murine typhus''

Can rats transmit diseases to human? 

Other than food poisoning, rats can also transmit some communicable diseases to humans via their urine, feces, fleas and bites. Many of these diseases are rather serious, and some can even be fatal (Diseases from rats to human). The following are some examples of diseases that can be transmitted by rats:

Rat-bite fever - Disease that cause by bites or scratches from infected rats, handling rodents with the disease (even without a bite or scratch), consuming food or drink contaminated with the bacteria. Symptoms of Rat-bite fever.

Plague - Caused by the bacterium Yersinia pestis. Humans usually get plague after being bitten by a rodent flea that is carrying the plague bacterium or by handling an animal infected with plague. In history, plague killed millions of people in Europe during the Middle Ages.Today, the risk of plaque can still be a risk in North America.

Leptospirosis - A bacterial disease that is spread by rat urine to humans. Symptoms including fever, chills, jaundice, vomiting, muscle aches or rashes. If left untreated, leptospirosis can cause kidney damage and in rare cases, can even be fatal.

What are the chances of rats nibbling on the food served in your favourite restaurant?  

In 2011, a national news media (Global News) reviewed and analysis data from Toronto
Public Health's DineSafe program and suggested that Rats, mice infested over 100 food premises and closed by health inspectors because of many health violations involving rodent infestations or inadequate pest control.

In 2009, a Scarborough Restaurant convicted and fined over $20,000 for food safety infractions after failing a health inspection in the summer. The restaurant was cited for a series of violations in an inspection, including failing to properly heat food, failing to keep food premises in a sanitary condition, .
failing to address a pest infestation, and did not have an adequately trained food handler on duty, as well as the operator obstructing the red closure sign posted by the public health inspector. Another restaurant was fined over $6000.00 because of rats (Photo - right).

How to tell if you have a rat infestation?

A rat infestation can be identified by checking areas within and outside of a home, a food establishment or a building for rat droppings, nests, and tracks. Rats are destructive and may gnaw on furniture, walls, floorboards and leaving rough holes. Rats are also more active in the early evening and can sometimes be heard scurrying about in attics, behind walls and other areas. In addition to these signs,
the very appearance of an active infestation is actually seeing a live rat in or around a building or a food establishment. Also, finding dead rats (see photo - left) in a kitchen,toilet, basement, attics,or garbage storage area can also be indication of a rat infestation. 
For food establishments, rats love to live in or around the garbage storage area, especially when garbage, food wastes and grease are not properly maintained and stored (see photo - right). Such environment gives rats food & shelter to start an infestation, and won't be long, rats will make their way inside the food establishment to cause a health hazard for the operator.

How to tell if the uninvited guests are rats or mice?
One way to determine if you have a rat or mouse infestation is to see what wastes they left behind. Even if you do not see an actual live or dead rodent, the size of the droppings can tell you if there is a mouse or rat infestation (photo on left - a rat dropping & mouse droppings side by side). Mouse droppings are small (6 mm or ¼ inch), and rat droppings can measure up to 19 mm (¾ inch) long and they look like small black jelly beans.

What is 'Sex in the city' for rats?

A female rat can reach sexual maturity in 2 to 3 months and can reproduce every 21 days. Each rat could have 15,000 descendants by the end of just one year. 

How to get rid of rats?

Rats are very hearty and adaptable creatures and they have been on this planet for hundreds of thousands of years, so they are hard to get rid of. A rat can get through a hole the size of a 25 cents coin into a building and once rats get inside, they can start an infestation very fast. 

A successful rat control strategy usually includes four steps: Sanitation, building design, rodent proofing and if needed, pest control

The following tips can help to prevent rat infestation in your home:

1. Eliminate food and water sources:
  • Keep all garbage in strong containers with tight fitting lids.
  • Do not add food scraps containing meat, bones, grease, fish into the garden compost.
  • Ensure the compost is away from the building. 
  • If pets are kept outside, remove leftover pet food right away and do not leave it outside overnight. 
  • Keep pet pens, enclosures and bird feeding areas free of wastes and spilled food and seeds..
2. Eliminate hiding places and shelters:
  • Keep backyard tidy, trim lawn grass short and keep garden areas free of tall weeds.
  • Remove unused piles of firewood, lumber, old storage containers or garden sheds.
  • Keep firewood on stands at least 30 cm (12 inches) off the ground.
  • Check for rat burrows or holes (see photo on left) regularly. A fresh dug burrow is an indication of an active rat infestation.
  • Keep property clean and free of garbage and junks.

3. Protect buildings:
  • Build garden or storage sheds on concrete slabs or foundation.
  • Cover or fill holes on walls, doors and any area where rats can get into the building (using steel wool to fill holes first before covering with cement).
  • Install screens in the garden compost.
4. Pest control:
  • Trapping - Using traps does have some advantages as it provides an alternative for those who do not want to use chemicals or pesticides.If the rat population is small
    enough, trapping can yield quick results when done properly. Remember to dispose of the dead rats before their odour becomes a problem, especially in an inaccessible area such as behind a wall or ceiling.
  • Rodent baiting - Use poison baits or rodenticides can be dangerous if not careful. They should be used in areas where domestic animals and children cannot access them, but the best is to contact a licensed pest control company to do the job.

Rat infestation in Toronto downtown 
News clip (Youtube video)

Other rat related links:

Loblaw: Supermarket shut down because of rats

Toronto Star: Fish market shut down

Global News: Rats, mice infested over 100 food premises

Toronto Sun: Rat inside restaurant

BlogTO: Pizza restaurant closed due to rats

Norway rats: Norway rat facts

CBC News link: Rat hitching a ride into Alberta, Canada


  1. Yeah the rats are big problem. And I think they exist in every home. A few months back there were loads of pests and mouse at my home. I had a hard time in dealing with them. At last I made the decision to hire a professional Pest control port macquarie service. Now I don’t have any pests at the home. I’ll have the inspection again after a few days.

    1. Rats are hard to control as they move from one location to another in a neighbourhood. I've observed rats running around in the middle of winter (-15 C) in our Toronto downtown area. I think you've made the right decision to hire a licensed pest control operator (Pest control port macquarie ) to handle the infestation in your home. You may want to inspect your home regularly to ensure no re-infestation. Thanks for the comment.

  2. I work in a restaurant in downtown Toronto and there is an ongoing active infestation in the area. A few food businesses including a fish store have been closed down by health inspectors for the past few years. We actually seeing live rats in and around buildings and food places, especially behind restaurant's garbage storage locations. They are very active at night.

    1. Thanks for the comments. if you continue to see evidence of rat infestation in the area, best is to ensure the operator of the restaurant you working for to take some pro-active action to prevent rats getting into the building. You may even contact the local public health inspector to help in dealing with the neighbourhood rat problem. In Toronto, you can file complaints via the DineSafe website or call 311 to report the problem.

  3. Hi, I tried the method you suggested and I talked to the owner about taking some control actions to clean up the restaurant and fix up the holes where the rats came into the kitchen. She was upset first and said the staff caused the problem, later, she agreed to bring in a pest service to get rid of rats and staff agreed to help clean up. I have also filed a complaint as you suggested and looking forward to the health inspector visit.

    1. Just a follow up to our comments. Hope you've resolved the rat issue at your workplace?

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