Australian vets have issued a warning after a rare but potentially fatal bacterial disease was found in New South Wales and the Northern Territory.

A spate of leptospirosis, a rodent-borne bacterial disease, has been recorded in NSW.

The outbreak has killed at least two dogs and left a puppy battling for survival.

Leptospirosis, or lepto for short, is a bacterium that is shed in the urine of infected animals such as rats and mice.

People should be on the lookout for lepto and the potential risk of your dog catching it, especially in areas where there have been rats (building sites, rubbish bins) in combination with stagnant water or puddles.

Dogs become infected and develop lepto primarily through ingestion of the urine from infected rats.

This usually occurs through contaminated stagnant water or soil, or even contaminated food.

Dogs that hunt and eat rodents can also become infected.

In WA, leptospirosis is a notifiable infectious disease.

Common symptoms can include lethargy, fever, vomiting, diarrhoea, excessive thirst, bloody urine and jaundice (yellow skin and gums).

You should take your pet to the vet as soon as possible as the chances of recovery depend on how severe the disease is and how quickly treatment is initiated.

Lepto can cause acute kidney and liver failure and when this happens many dogs will succumb to this disease.

It is best to vaccinate dogs, especially in high-risk areas.

People should also try to stop their dogs from swimming or drinking in waterways such as rivers, lakes and ponds and take measures to reduce the rodent population.

Walk your dog on a leash in high-risk areas, especially if they love chasing rats.

Humans can also become infected by the urine of infected rats or dogs and people are advised to wash their hands and seek medical advice if they suspect they have been exposed to lepto.