Puppies given a startling amount of antibiotics have spurred a multi-state outbreak of diarrhea-causing bacterial infections that are extensively drug resistant, federal and state health officials report this week.

The finding, published in the September 21 Morbidity and Mortality Weekly Report by the Centers for Disease Control and Prevention, suggests that the dog industry is in serious need of training and obedience classes. The “widespread administration of multiple antibiotic classes” to puppies, including all of the classes commonly used to treat diarrhea infections in humans, is an alarming finding, the officials suggested. They called for fairly simple fixes including better hygiene and animal husbandry practices, as well as veterinary oversight of antibiotic use.

“Implementation of antibiotic stewardship principles and practices in the commercial dog industry is needed,” they concluded bluntly.

The criticism caps a multi-state investigation into an ongoing outbreak of Campylobacter infections in humans. This gut bacterial infection is estimated to cause more than a million diarrheal diseases in the US each year but is typically not linked to puppies or dogs. Instead, it’s usually linked to undercooked meat, unpasteurized milk, or contaminated water.

But the latest data fetched a new trend. Between January 2016 and February 2018, health officials kept an eye on 118 specific cases in 18 states. (Those cases led to 26 hospitalizations and no deaths.) It turned out that of the 118 cases, 29 were pet store employees. Officials collected further survey data to ask about exposures, getting good data from 106 of the 118 cases. Of those 106, 105 reported exposure to dogs, with 101 cases reporting specific exposure to pet-store puppies. The one other person on whom officials had data said they didn’t recall any dog contact.

Digging deeper, officials in four of the affected states (Kentucky, Ohio, Pennsylvania, and Wisconsin) visited 20 pet stores collectively. They sniffed out drug records for 149 puppies, finding many were given antibiotics without being sick—a big no-no for antibiotic stewardship and preventing drug resistance.

Records indicated that of the 149 puppies, pet stores had given 142 (95 percent) at least one antibiotic. More than half of those (78 puppies, or 55 percent) got those antibiotics for prophylaxis purposes only—meaning they weren’t sick and were given the drugs merely as a precaution to prevent them from becoming sick. Additionally, nearly 40 percent (54 puppies) got antibiotics for prophylaxis and treatments for actual infections. Only two puppies got drugs just because they were sick. (The remaining eight puppies of the 142 that got antibiotics didn’t have any records indicating why they got the drugs.)

Pet stores had given the puppies a wide range of antibiotics, noting 16 different drugs, which included ones from the same classes of antibiotics used to treat Campylobacter infections in humans.

Meanwhile, health officials from six of the outbreak-affected states (Florida, Kansas, Kentucky, Ohio, Pennsylvania, and Wisconsin) collected 51 stool samples from sick humans as well as 23 puppy poop samples. Whole genome sequencing analyses linked Campylobacter isolates in 45 of the human samples to those in 11 of the puppy samples.

The researchers took 18 of those Campylobacter isolates (10 from humans and 8 from puppies) and subjected them to antibiotic resistance testing. All of them were resistant to at least seven antibiotics (azithromycin, ciprofloxacin, clindamycin, erythromycin, nalidixic acid, telithromycin, and tetracycline).

The officials next tried to trace back where those infectious pups were coming from, but they couldn’t find a single breeder or distributer as a common source. Instead, the puppies seemed to swap infectious germs throughout the breeding, distribution, and transport processes of the commercial dog industry.

In the end, the officials conclude that the dog industry and pet stores must doggedly work to address the public health threat. That includes using antibiotics responsibly, educating pet store employees and customers on best hygiene practices, and housing puppies during breeding, transport, and distribution in a manner that reduces transmission risks.

“Although the investigation is completed,” the officials write, “the risk for multidrug-resistant Campylobacter transmission to employees and consumers continues.”