The US government has been buying up hundreds of cats and dogs to feed to healthy kittens, an investigation has found. 

A US Department of Agriculture (USDA) lab in Maryland has been purchasing large quantities of dogs and cats for "needless" research projects, which involve feeding the brains of cats to healthy cats and injecting their hearts and tongues into mice.

The investigation, titled "USDA KITTEN CANNIBALISM", details how the USDA has been purchasing animals from meat markets (and other places) for use in toxoplasmosis experiments. According to the report, the Maryland lab feeds animals that have been intentionally infected with Toxoplasma gondii to healthy cats in order to infect them. After the researchers harvest the parasite from the cats' feces over a period of several weeks, they then euthanize the animals and incinerate them.

Cats are the only known hosts for the parasite's eggs, though the infection can be transmitted to humans who consume food or water contaminated with cat feces. In humans, toxoplasmosis causes symptoms such as a fever, swollen glands, and aching muscles. 

The research currently receives $650,000 a year in taxpayer funds and has spent a total of $22.5 million, killing more than 3,000 cats since it began in 1982.

According to the White Coat Waste Project (WCW) report, cats and dogs have been bought from questionable sources, including:

• 42 cats purchased at Chinese pet markets and meat farms and killed before their hearts and tongues were
  shipped to the US to be injected into mice.
• 48 stray cats rounded up in Ethiopia and killed before their hearts were shipped to the lab to be fed to mice.
• 34 cats purchased at a Chinese meat market, killed, and their tongues, brains, and hearts shipped to Maryland.
• 309 dogs acquired from a shelter in Colombia, killed, and their brains, tongues, and hearts shipped to be fed to cats.
• 120 unclaimed Brazilian shelter dogs killed and their tongues, brains, and hearts of 20 of them fed to cats.
• 42 dogs destined for a Vietnamese meat market purchased and killed. The hearts, brains,
  and tongues of some of these dogs were shipped to Maryland and fed to cats.

Lawmakers in the House of Representatives have tried to pass an act to permanently end the practice, through the Kittens in Traumatic Testing Ends Now (KITTEN) Act.

"The USDA's decision to slaughter kittens after they are used in research is an archaic practice and horrific treatment, and we need to end it," Sen. Jeff Merkley, D-Ore., the Senate bill's lead sponsor, told NBC News.

Support for the ban appears to be growing, following the new report.

The report alleges that "some of these cats and dogs were purchased by the government from the same Asian meat markets that the US Congress roundly condemned in a House Resolution."

Though the lab has had some success in fighting toxoplasmosis, USDA researchers have not seen a breakthrough in 20 years, according to one whistleblower.

"It's crazy. Cannibal cats, cats eating dogs," former USDA scientist Jim Keen told NBC News of the research. "I don't see the logic."

WCW vice president of advocacy and public policy Justin Goodman told NBC News that the practice of infecting new cats is no longer necessary as they can continue to use samples they already have.

"They just don't need to do it anymore; it's scientifically unnecessary."