Paraquat is a highly toxic weed killer that is used extensively to control a wide range of grasses and broadleaf weeds. The Australian Pesticides and Veterinary Medicines Association (APVMA) has restricted the supply of paraquat due to its high risk of poisoning and it is only approved for use in commercial agricultural settings. In Australia and New Zealand, paraquat is only available as a blue or green liquid with a pungent smell and is not expected to be found in most homes.

Whilst paraquat poisoning is uncommon, ingestion is regarded as a medical emergency and immediate veterinary assessment is recommended in all cases. Vomiting often occurs soon after an ingestion as many paraquat formulations contain an emetic agent. Other early signs following ingestion include a reduced appetite and lethargy. These clinical signs, frequently combined with a history of consuming unknown food items, often lead to an initial misdiagnosis of acute gastroenteritis.

Concentrated formulations of paraquat are corrosive and ingestion can result in burns and ulceration to the mouth and throat. As poisoning progresses, affected animals can develop multiple organ failure including respiratory failure, acute kidney injury or liver injury. Skin exposure to liquid concentrates may result in burns. Prolonged skin contact, particularly to concentrated formulations, may result in systemic poisoning.

Early diagnosis, decontamination and veterinary assessment is crucial and potentially lifesaving following exposures. However, as many of these exposures may occur in rural and remote areas, sometimes access to veterinary care may be limited. The Helpline can be particularly useful in these cases and can immediately assess the exposure and make an immediate risk assessment. Our team can also provide step by step advice on appropriate methods of decontamination at home to prevent as much absorption of the toxin as possible. Administration of food or even a dirt or clay slurry is recommended following ingestions as this can limit absorption of the paraquat.

For those that store or use paraquat containing products on properties with animals, some poisoning prevention measures include:

✅ Never decant paraquat products into unlabelled containers for storage.

✅ Always leave partially used products in the original labelled container.

✅ Empty drums should be triple rinsed and stored in a locked room to await proper disposal.

✅ Always follow the manufacturers recommended withholding periods for grazing of treated areas.

The Animal Poisons Helpline provides free advice to pet owners in Australia and New Zealand and can be reached on 1300 869 738 (AU) or 0800 869 738 (NZ). If you don’t already follow the Animal Poisons Helpline Facebook page, follow now to receive live animal poisons alerts and updates. If you are a member of a veterinary team in Australia or New Zealand, you can join the Animal Poisons Centre For Vets Facebook group which is regularly updated with toxicology tidbits and poisoning trends. We thank the Western Australian Department of Primary Industries and Regional Development for supporting this post.