Leptospirosis: BC's most relevant rat-borne disease
Leptospirosis is a bacterial infection caused by Leptospira species shed in the urine of Norway rats (and many other mammals). In Metro Vancouver, the risk is concentrated around contaminated water sources, soil, or mud that Norway rats have urinated in. Urban scenarios include: gardening with bare hands in soil adjacent to a rat burrow system, wading in floodwater in Richmond or Pitt Meadows (which may be contaminated with rat urine), and contact with surfaces in crawlspaces, basements, or garages with active rat populations.
Leptospirosis presentations range from mild flu-like illness (fever, headache, muscle aches, 80% of cases) to severe Weil's disease (jaundice, kidney failure, meningitis). BC reports approximately 5-20 cases per year, mostly tied to occupational exposure (farm workers, sewer workers) or recreational exposure (trail running through flooded areas, kayaking in contaminated water). Urban Metro Vancouver cases are rare but documented. The bacteria dies quickly when dried — the main risk is wet, contaminated soil or water, not dried droppings.
| Pathogen | Carrier | Transmission route | BC case frequency | Severity |
|---|---|---|---|---|
| Leptospira spp. | Norway rats (primary) | Contact with contaminated water/soil/urine | 5-20 cases/year BC | Mild to life-threatening |
| Sin Nombre hantavirus | Deer mouse (Peromyscus) | Inhalation of aerosolized droppings/urine | 1-5 cases/year BC | Very severe; 40% CFR |
| Salmonella spp. | Rats, mice (via food contamination) | Ingestion of contaminated food | Sporadic; under-reported | Mild to moderate |
| Lymphocytic choriomeningitis (LCMV) | House mice (primary) | Contact with urine, droppings, saliva; pregnancy risk | Rare in BC | Mild to severe (pregnancy) |
| Rat-bite fever (Streptobacillus) | Rats, rarely mice | Bite or scratch; contact with carcass | Very rare in BC | Moderate; treatable with antibiotics |
| Murine typhus (Rickettsia) | Rats via fleas | Flea bite (not direct rat contact) | Rare in BC | Moderate; antibiotic-responsive |
Salmonellosis and food contamination
Salmonella from rodents is not transmitted by bites or droppings inhalation — it's a food-contamination pathway. Mice and rats walking across food-preparation surfaces, food packaging, and open food containers leave Salmonella-contaminated urine and faecal traces. This is why mice in a kitchen are a food-safety concern independently of any structural or material damage. The risk is highest in spaces with open food storage (pantry shelves without containers, fruit bowls, bread bins) or shared with rodents long enough that the population has been active across multiple food surfaces.
LCMV and pregnancy risk
Lymphocytic choriomeningitis virus (LCMV) is carried by house mice and can be transmitted through contact with mouse urine, droppings, or saliva. For healthy adults, LCMV causes a mild flu-like illness in most cases. The serious concern is in pregnancy: LCMV infection in the first trimester has a high rate of miscarriage; in the second and third trimesters, it can cause severe fetal neurological damage. Pregnant women in a home with confirmed mouse activity should take this seriously — this is a situation where immediate professional treatment is the right response, not deferred DIY.
Reducing exposure without waiting for treatment
- Store all food in glass or rigid plastic containers immediately — cardboard and soft plastic allow rodent access and surface contamination.
- Wash all food surfaces that rodents may have contacted with a 1:10 bleach solution before use.
- Don't let dogs and cats eat prey rodents (rat-bite fever and intestinal parasites are transmitted this way).
- Wear gloves when gardening near areas with rat burrow activity.
- Avoid wading in floodwater near agricultural or industrial areas after heavy rain (leptospirosis risk).
- Use N95 and gloves for any cleaning in rodent-active areas — this applies to house mouse evidence as well as deer mouse evidence.