Agriculture officials said cats and kittens would no longer be used in a research program that an animal rights group says resulted in thousands of animals being euthanized.

Cats and kittens at a laboratory in Maryland were fed meat that sometimes contained the toxic parasite Toxoplasma gondii over more than three decades.

Scientists tested the stools of the animals for signs of the parasite in the meat before they were put down.

The US Department of Agriculture (USDA) says the research, carried out by its Agricultural Research Services (ARS) department, yielded "undeniable results." The pathogen can cause toxoplasmosis — the leading cause of death from foodborne illness in the United States.

An investigation by the White Coat Waste Project (WCW) an organization opposed to government-funded animal testing — claimed that at least 3,000 cats and kittens had been euthanized since 1982.

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The "USDA Kitten Cannibalism" study claimed the department had bought hundreds of cats and dogs in China, Vietnam, Ethiopia, Colombia and other countries, which were killed and fed to cats and other animals.

WCW's investigation was said to have horrified lawmakers, who introduced legislation known as the "Kitten Act" to end the project. Under mounting pressure, the USDA said it would no longer be using cats in such experiments.

The USDA said the research had, in any case, reached its maturity and that it considered "the project's objectives for agriculture achieved."

"While there is still additional research needed in this area regarding human health, this research area is outside of USDA's stated mission," a statement said.

Republican Nevada Congresswoman Dina Titus said she welcomed the USDA announcement as a "major victory for kittens, cats, and taxpayers."

Read more: What is the future of animal testing?

The USDA did not address the allegations that cat cannibalism had taken place, but said it had not euthanized or infected any cats with the toxoplasmosis parasite since September 2018. It said that 14 cats on its premises that were not infected would be adopted by employees.

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"We are continually assessing our research and priorities and aligning our resources to the problems of highest national priority," said ARS Administrator Chavonda Jacobs-Young.

Officials said the research had helped to halve the rate of people being infected with the parasite, which can lead to influenza-like symptoms.

Toxoplasmosis usually causes no symptoms in adults, but it can prove particularly dangerous to pregnant women and their babies, and even prove deadly.

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