Cats are having a $12 million impact on Australian agriculture every year due to the diseases they carry, according to a new study.
The study found cats infected with diseases such as toxoplasmosis, sarcocystosis and cat roundworm release millions of tiny parasitic 'oocyst' eggs into the environment with the faeces.
The eggs then remain in soil, pasture and water for months, where they are ingested by livestock such as sheep, goats and cows, and also by poultry.
The research, published in the scientific journal Wildlife Research, was undertaken by the Threatened Species Recovery Hub of the Australian's National Environmental Science Programme.
Lead author Professor Sarah Legge from the Australian National University and the University of Queensland said the diseases were costing the industry millions of dollars each year, with the sheep industry the worst affected.
"We found that toxoplasmosis infections cause the loss of over 62,000 unborn lambs each year in Australia, costing the industry around $10 million each year," she said.
"Sarcocystosis costs the meat industry around $2 million per year. It causes cysts in meat which require trimming and can even result in whole carcasses or shipments being rejected."
Professor Legge said studies in countries with comparable lamb production industries, including New Zealand, had also found similar results.
Co-author Dr Patrick Taggart from the University of Adelaide said not all regions of Australia were affected in the same way.
"Rates of these diseases are higher in areas with more cats and in cooler and wetter regions where the parasites that cause these diseases can survive longer in the environment," he said.
"South Australia and Tasmania experience higher rates of lamb losses due to toxoplasmosis than other regions.
"Sarcocystosis-positive farms are 15 times more common on Kangaroo Island than on the adjacent mainland and cysts can be observed on up to two-thirds of slaughtered adult sheep from the island."
He said despite cats having a reputation for keeping some agricultural pests, such as rodents and rabbits, in check "there is no evidence that they are effective at this task".
"Rodent and rabbit numbers are primarily driven by weather; when their numbers go up they boost the density of feral cats which in turn may increase rates of cat-dependent pathogens in livestock.
"We can reduce the cost of cat-dependent diseases on agriculture by lowering numbers of feral and pet cats around farms.
"There is also some evidence that applying agricultural lime to pastures can reduce the viability of sarcocystis and toxoplasmosis oocyst in the environment and hence reduce livestock infection rates," he said.
