The U.S. Food and Drug Administration (FDA) wants veterinarians to help spread the word about the potential for jerky pet treats to cause illness, and to collect data and samples for the government’s ongoing investigation.

A Dear Veterinarian letter released Tuesday asks clinicians to report all suspect cases to the FDA; collect certain diet details from owners of sick pets; conduct routine urinalysis and blood work for liver and kidney injury; and freeze a subsample of urine for possible later analysis.

The FDA also is asking practitioners to share a fact sheet on the topic to help raise public awareness.

Despite extensive media coverage and multiple alerts posted by the FDA since 2007, the agency says it continues to receive reports of illness from pet owners who had not previously heard that pets — mostly dogs — were turning up sick after eating jerky treats.

“That told us that we needed to find a new way to communicate with pet owners, and what better way than to enlist clinicians as our eyes and ears?” said Siobhan DeLancey, a spokeswoman in the FDA Office of Foods and Veterinary Medicine.

The outreach to veterinarians was part of an extensive progress report posted Tuesday by the FDA about the jerky saga, which has continued without resolution for six years.

As of Sept. 24, the agency said, it had received more than 3,000 complaints of illness related to consumption of jerky treats containing chicken, duck, sweet potato or dried fruit. The reports involve more than 3,600 dogs and 10 cats; and more than 580 deaths.

Most of the complaints relate to treats made in China, a fact that has led many consumers to view with suspicion any pet foods and snacks with a “made in China” label. The FDA post suggests that avoiding products with such labels may not be enough. “Pet owners should be aware … that manufacturers do not need to list the country of origin for each ingredient used in their products,” it notes.

The agency has been unable to identify a contaminant. However, the discovery of residues of antibiotics not allowed in foods led in January to the recall of several varieties of chicken jerky, including the popular brands Waggin’ Train and Canyon Creek Ranch by Nestle Purina PetCare Co. and Milo’s Kitchen by Del Monte Corp.

Since then, the FDA reports, there has been a “sharp drop” in the number of complaints. “FDA believes it unlikely that the reports of illness it has received are caused by the presence of antibiotic residues in jerky treat products,” the agency states. “Rather, because the brands that were recalled represent a significant portion of the jerky pet treat market in the United States, FDA theorizes ... that the drop-off in complaints since January 2013 is more likely the result of the general lack of availability (of) jerky pet treat products.”

Despite its doubts that the antibiotic residues explain the thousands of illness complaints, the FDA says it is studying the possibility that low levels of antibiotics may make dogs ill when fed over time. The line of inquiry “may take many months to complete,” the agency notes.

While it pursues that and other potential sources of contamination, the agency advises pet owners to consult their veterinarians before feeding jerky treats to their pets. Many veterinarians already have been recommending that clients avoid jerky treats. Some recommend avoiding all food products made in China, or all commercially manufactured treats.

Dr. Neil Marrinan, a veterinarian in Connecticut, treated a Yorkshire terrier about six years ago for reversible kidney disease that he believes was induced by what he describes as “bright orange Chinese ‘chicken jerky’ treats.”

Marrinan subsequently began advising all clients to avoid all China-made treats. “My own practice is to avoid any treat with a bright orange color that you could not make yourself in your own kitchen,” he said.

He commended the FDA for continuing to investigate. “I think that it is important to determine the cause because whatever is causing kidney disease after eating these treats may be present in other food, as well,” he said.

The FDA reports that of the complaints of illness it’s received, about 60 percent entail gastrointestinal illness, with or without elevated liver enzymes. About 30 percent entail kidney or urinary signs. The remainder involve a variety of signs, convulsions, tremors, hives and skin irritation among them.

Common early signs of illness are decreased appetite, lethargy, vomiting, diarrhea, increased consumption of water and increased urination.

Among the cases involving kidney and urinary dysfunction, the FDA reports that about 135 have been for a specific kidney disease known as Fanconi syndrome, or Fanconi-like syndrome. In Fanconi syndrome, part of the kidney called the proximal tubule does not work properly, causing nutrients such as glucose, bicarbonate and amino acids to be lost in the urine.

Fanconi-like syndrome has been identified by veterinarians as a hallmark of the mysterious jerky-related disease. In dogs, Fanconi syndrome typically is seen as an inherited condition in breeds such as basenjis and Norwegian elkhounds.

One piece of information in particular the agency says it often lacks in reports of illness is the lot number from the package of suspect treat. In a statement aimed at pet owners, the agency explains: "If we have the lot numbers, we can identify whether particular lots triggered more complaints, trace products back to specific manufacturing facilities, and identify lots for testing. While we still want to hear from you even without the lot number, this information can help our investigation immensely.”

In the multiple materials the FDA posted Tuesday about the jerky treat puzzle, the agency detailed the many steps it has taken to investigate the problem, including inspecting facilities in China where jerky treats are made, establishing ongoing contact with authorities in China and companies that make pet treats, and even making its own jerky to try to duplicate the commercial process.

“This is one of the most elusive and mysterious outbreaks we’ve encountered,” Dr. Bernadette Dunham, director of the FDA Center for Veterinary Medicine (CVM), says in posted remarks.

A blog entry by Dr. Linda Tollefson, associate commissioner for the FDA Office of Foods and Veterinary Medicine, expresses the personal love that CVM employees have for animals and declares, “It’s our mission, both as public servants and animal lovers, to find — and eliminate — the cause of these illnesses.”