Regulator urges WHS caution during the mouse plague

The following article is a news item provided for the benefit of the Workplace Health and Safety profession. Its content does not necessarily reflect the views of the Australian Institute of Health & Safety.
Monday, 20 September, 2021 - 12:00
Policy & legislation
New South Wales

SafeWork NSW recently issued a safety alert warning those in contact with rodents – particularly farmers and agriculture workers – to be more careful of health and safety risks as areas of rural and regional NSW continue to be affected by an ongoing mouse plague.

These risks include greater exposure to diseases such as leptospirosis and hazardous chemicals like zinc phosphide, and SafeWork NSW also said mental health and wellbeing and that of your colleagues and workers could also be impacted.

The alert said zoonoses such as leptospirosis are diseases that can be transmitted between animals and humans. Leptospirosis is a bacterial infection that can be spread from animals, such as rodents to people.

Exposure can occur through contact with infected mice or water, soil or mud that has been contaminated by the urine of infected mice. The bacteria can enter the human body through cuts or abrasions and occasionally through the lining of the mouth, nose and eyes.

Rodents such as mice can also transmit other diseases to humans, including lymphocytic choriomeningitis virus (LCMV), rat-bite fever and gastrointestinal infections such as salmonellosis.

The alert said farmers, agriculture, horticulture and abattoir workers are some groups who are at higher risk of exposure. Rainfall and flooding events such as those recently seen across NSW can also increase the risk of leptospirosis.

Symptoms of leptospirosis usually develop within five to 14 days after infection, and symptoms may include flu-like symptoms such as headaches, muscle aches, fever, chills, vomiting, diarrhoea and conjunctivitis. Some people will only have mild symptoms, although some may develop severe disease including kidney and liver problems, jaundice, bleeding and lung problems.

The alert said there are a number of important control measures to minimise the risk of leptospirosis exposure.

Minimise rodent contact

  • Clean up rubbish and remove food sources around your workplace or onsite accommodation.
  • Seal as many holes or gaps as possible inside your premises.
  • Conduct regular pest control such as baiting and traps. Do not set traps near food preparation areas.


When you work in areas where mice and rodents have been

  • Cover cuts and abrasions with a waterproof dressing.
  • Wear personal protective equipment (PPE), including gloves and waterproof protective clothing (for example, goggles, aprons and boots) where contact with rodents or their urine is possible (such as clean-up of mouse carcasses). Handling of rodent carcasses should not be undertaken by workers who are pregnant or whose immune system is suppressed.
  • Wear appropriate footwear when walking in mud or moist soil.
  • Avoid wading in or drinking water that could contain rodent urine (boil drinking water if you are unsure).
  • Wash any cuts and scratches sustained immediately with clean water and soap.
  • Wash hands with clean water and soap and dry thoroughly after handling potentially infected material – especially before eating, drinking or smoking.
  • Shower after work.


Clean and decontaminate

  • Clean and disinfect rodent contact areas such as floors and countertops with disinfectant or bleach solution.

  • Wash any clothing or bedding with laundry detergent in hot water if exposed to rodent urine or droppings.

To control the mice population, farmers and workers may use hazardous chemicals such as zinc phosphide more often and in bigger quantities than commonly used in mouse and rat baits.

The Australian Pesticides and Veterinary Medicines Authority (APVMA) has recently issued a permit allowing the concentration of zinc phosphide to be increased from 25 grams per kilogram to 50 grams per kilogram in mouse and rat baits.

The alert said exposure to zinc phosphide can be hazardous to your health. Exposure can occur by getting it on your skin, breathing it in or accidentally eating or drinking a product containing the chemical. When zinc phosphide is accidentally eaten by a person it can travel to the stomach and mix with stomach acid – causing it to release the toxic gas, phosphine.

Symptoms of exposure to zinc phosphide include headaches, dizziness, vomiting and difficulty breathing. It can also cause liver and kidney failure, convulsions, delirium, coma and death in cases with severe acute exposure.

Zinc phosphide is a hazardous chemical, so it is important to use, handle, store and dispose of it safely.

The alert said to ask your supplier for safety data sheets (SDS) and always refer to product labels and the SDS for directions on the safe use, handling, storage and disposal of hazardous chemicals. Read and understand the health effects of the product that you are using and note the safety measures required to use the chemical safely.

In using zinc phosphide, the alert also said to:

  • Follow instructions and information in labels and the SDS for safe use.
  • Ensure all workers and others who are handling the chemical are informed of the risks to their health and are instructed on working safely with it.
  • Do not open zinc phosphide in enclosed areas and avoid inhaling any vapour.
  • Make sure correct personal protective equipment (PPE) such as gloves, masks (with suitable gas filter cartridges) and protective clothing are used and provided to those who are at risk of exposure.
  • Make sure you practice good personal hygiene to reduce your risk of exposure.
  • Always remove contaminated clothing and wash hands after using chemicals and before eating, drinking, using the toilet or smoking
  • Wash contaminated clothing separately.