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Outbreak of Drug-Resistant Salmonella at an Animal Shelter

Of the many things that keep shelter workers awake at night, one of the most worrisome is the possibility that a shelter animal could cause severe injury or illness for an adopter. Shelter director and veterinarian Jeff Rosenthal of the Idaho Humane Society faced that nightmare on a large scale when his shelter was struck by an outbreak of severe salmonella infection. Dozens of cats and adopters were affected, and some people were so ill they had to be hospitalized. 

After the dust settled, I was able to talk with Jeff about the outbreak. His words vividly describe the ordeal: “Everyone involved in animal sheltering deals with conflict and heartache, but nothing I had previously encountered compared to the stress of dealing with weeks of talking with people all day, every day, about their own illness or in many cases, their children’s illness. It was exhausting for myself and my staff, and I was terrified that a human fatality, caused by a disease spread by our shelter’s cats, might occur.” In the hopes that the rest of us can avoid ever knowing firsthand what that’s like, Jeff offered some insights into his shelter’s hard-won experience.

So, how did you first find out about the problem?
I received a call from the health department telling me they had identified six people with “multi-drug resistant Salmonella typhimurium DT 104 infection” associated with cats adopted from my shelter. They were especially worried because it was a strain resistant to treatment with common antibiotics. Ultimately, 49 human cases were identified, and ten people were hospitalized. One case was in a kid that came to the shelter and only touched one cat. He didn’t adopt, just visited—and came down with salmonella.

Yikes. Sounds pretty contagious!
Yes. I think it’s important to understand that we did have strict disinfection protocols in place at the time, but we were holding a lot of cats. We thought our procedures were more than adequate. We have six vets on staff, and we’re probably the most modern facility in Idaho. This was just a really contagious bug ... almost unbelievably contagious, and it made people really sick.

Were you able to trace how it all got started?
We never found out for sure. We raided a cat hoarder at about the time the outbreak started. Many of the confiscated cats turned out to be very adoptable and apparently healthy, and some cases were linked to those cats. There’s also a possibility that people brought disease into the building—one of the first human cases was a volunteer who used to come in and handle every cat. Contaminated food was another possibility.

Did the affected cats look sick?
There wasn’t a noticeable increase of diarrhea in the shelter. Most people got sick from cats that developed diarrhea after adoption, but some got infected from cats that never had symptoms at all. Later, we had quite a few adopted cats diagnosed with salmonella. If the adopters didn’t want to keep them during treatment, they were brought in to the shelter. Some of those cats were very sick with vomiting and diarrhea.

Was there any publicity about it? How did you handle that?
We sent out a press release as well as a bulletin to every vet in the state. Luckily, we have such a good relationship with local media, we almost had to twist their arm to cover this thing. We also contacted all adopters. People were almost more upset that the animal was ill than that they were ill. They didn’t want to talk until they were sure no one was going to hurt their cat.

Who else got involved?
The health department, the CDC, and researchers from Washington State University. They helped a lot with all the testing and environmental culturing. Their involvement saved us thousands of dollars. We definitely did the right thing by not curling up like a turtle and hiding in our shell.

Has there been any lingering negative effect on the shelter’s reputation?
There was no long-term impact on the organization’s image—as soon as we opened up again our cattery was full of potential adopters. Now we have zoonotic disease brochures and signs about salmonella all over the place. None of it seems to dissuade anyone from adopting. Then again, there were no fatalities. If there had been, I think it would have been a totally different story. We were very lucky.

Though bright and friendly, these polypropylene cat cages at the Idaho Humane Society were porous and easily scratched. Even steam-cleaning, high-pressure hot-water spraying, and scrubbing with Virkon didn’t get rid of the highly contagious salmonella bacteria; the material underneath the coating was “hopelessly contaminated.”

What did it take to stop the outbreak?
We shut down adoptions and admission of cats for three weeks and essentially gutted the whole place. When the CDC did the environmental sampling, they found salmonella in areas throughout the building. I really wondered if we could ever go back to operating. We steam-cleaned and used high-pressure hot water cleaner on all the cat kennels. We repainted the entire interior of the shelter. We had been using Disintegrator and Roccal on the kennels, but after the outbreak we switched to Virkon for cat areas. After doing all that, we went back and recultured to make sure we had gotten rid of all of it. Approximately half of our cattery was housed in polypropylene kennels. Although they looked great, some had microscopic scratches and the material underneath the coating was porous. They were still contaminated, so we had to get rid of all of them.

What changes have you made since then?
We’ve really changed the way we handle sick cats. In some ways I think having the veterinary staff contributed to the problem—we felt like we could treat a lot of these animals that were ill. We were keeping way too many sick animals here. Before the outbreak we only moved cats to isolation or sent them to foster care if they became very ill, and we always had cats with mild URI in our public adoption area.

In the aftermath of the outbreak, Rosenthal and his staff got rid of the polypropylene cages and broke down existing stainless steel cage banks into single units. The units sit atop stainless steel carts created by a local metal shop, enabling staff to roll each one individually from room to room so cats can remain in the same housing for the entire length of their stay.

How do you manage sick cats now?
We have zero tolerance for any ill animals in the general population now. If an animal gets sick, it goes immediately to isolation and out the door to foster care within 24 hours. We don’t keep any cats with diarrhea in the shelter. There was a high correlation between animals on antibiotics and salmonella, so we’re now a lot more careful about antibiotic use. We don’t routinely use antibiotics for URI or kennel cough anymore—only if there’s a specific indication.

Did you see an increase in euthanasia when you started these new policies?
Actually, no. We’re not adopting any fewer animals, and we’re not euthanizing any more animals. We’re just euthanizing smarter. I’ve been really pleased with how being conservative about keeping sick animals has benefited the shelter. I think we’re going to end up saving more animals in the long run—one sick cat can condemn ten cats on either side.

You mentioned the polypropylene cages were hopelessly contaminated. How do you house cats now?
We had a local metal shop build stainless steel carts for us, and broke down the existing stainless steel cage banks into single units mounted on the carts. Cats stay in the same units as long as they are in the shelter, and we just roll the whole thing from room to room as they move from intake to adoption.

Disease name: Salmonellosis 

Type of agent: Gram negative rod-shaped bacteria

Shelter species most commonly infected: Reptiles and many other animals, including dogs, cats, birds, and livestock.

Clinical signs: Although most commonly asymptomatic, Salmonella infection can cause vomiting and diarrhea in humans and many other animal species. Disease can be severe and occasionally fatal, especially in very young or immunocompromised individuals. Severe cases can lead to decreased red and white blood cell and platelet counts, and may resemble panleukopenia or parvo in cats and dogs. Shedding of salmonella can persist for as long as 6 to 12 weeks after clinical recovery.

Diagnosis: Fecal culture. Intermittent shedding is possible, so three negative fecal cultures at two-week intervals are required to declare an animal free of salmonella.

Transmission and control: Fecal-oral spread directly, in contaminated water and food or on fomites such as food dishes and grooming implements. Spread from infected humans to animals is possible. Risk of infection is increased by stress, poor nutrition (including overfeeding), overcrowding, antibiotic therapy, and surgery. Young animals and animals with a history of roaming and predation are also at increased risk. Salmonella can persist for weeks in the environment. It is reportedly inactivated by household bleach diluted at 1:32, potassium peroxymonosulfate (Virkon or Trifectant), and some quaternary ammonium disinfectants.

Treatement: Supportive care. Antibiotics may be prescribed in cases with signs of systemic infection, but the risk of selecting for antibiotic-resistant strains must be considered. Successful elimination with fluoroquinolones (Baytril) therapy in a cattery has been documented, but recently strains resistant to antibiotics in this class have been reported. Confirmation of cure by fecal culture is required, which can prove costly in a shelter environment. Consultation with local health officials is recommended.

Multi-drug resistant Salmonella typhimurium DT 104: This strain of Salmonella has been an increasing threat in recent years. It causes relatively severe disease in people and is resistant to treatment with common antibiotics, including ampicillin, tetracycline, sulfonamides, chloramphenicol and streptomycin. Up to 3- percent mortality has been reported in humans infected with this strain. Outbreaks of zoonotic S. typhimurium associated with cats have been reported at veterinary clinics and shelters in Idaho, Washington, Minnesota, and California.

Did changing the cat housing cost a fortune?
Reworking the kennels cost about $20,000, but I think this system is much more efficient as well as cleaner. We used to get a cat into the shelter and move it from one cage in intake, then to another room, then later to the cattery. Each cage would have to be cleaned. Now we roll the same cage right from intake to our cattery, and when adopted, the cage rolls over to our clinic for spay/neuter. They stay in the same cage from admission until they go home. When the cage is empty, the whole unit is rolled outside and sprayed down with a hot water pressure hose and then thoroughly disinfected. This greatly eliminates the possibility of cross contamination between cats. One of the big problems we ran into during the outbreak was trying to track down every kennel where the sick cats were during their shelter stay, so that’s another benefit of having them stay in the same cage.

How do you clean the cat cages these days?
We realized the cleaning process itself spreads germs. Think about little things like using the same brush on another kennel. We also used to use one transfer cat carrier for multiple cats when cleaning cages, without cleaning the carrier between cats. Now every cat has its own cardboard kennel that stays on the cart. Because the cat stays in the same cage, we now clean kennels only to the degree that they need to be cleaned, just enough to keep the cages sanitary. We’ve always used disposable litter boxes, and we switched from plastic food dishes to stainless steel. We have knitted blankies that are washed between cats.

Sounds like you’ve worked out a good system. But how do you prevent cross contamination from people handling the cats?
We had a self-service cattery at the time of the outbreak. Now we have supervision during all open hours, and visitors are not allowed to enter the cattery unless escorted. No one (public or staff) is allowed to touch a cat without washing hands or wearing gloves. We have no shared “get acquainted” areas where the cats mix and mingle.

That’s a lot stricter than most shelters. Did you meet with a lot of resistance on these changes?
Well, it’s not like you can’t touch the cats. You can touch them—just wash hands and be clean. We provide food-handler gloves, which are extremely cheap. They last well enough to handle a cat, and they’re not latex so you don’t have to worry about allergies. We found people would rather wear those gloves than have to wash hands constantly. As far as staff, those that were there during the outbreak don’t have a problem with these new procedures. They remember how scary it was. There were weeks when I really wondered if we could ever handle cats again.

Have you seen a reduction in overall disease with the new policies?
I really think the way I’m handling cats now has merit. I thought it would be impossible, but it’s worked out very well. We never put sick cats up for adoption now. We’re much more successful in our adoptions, and we have much fewer sick cats coming back. The adoptions are also more successful because people get more counseling while escorted by staff.

Any final thoughts on what shelters can do to protect themselves from something like this?

  • Protect yourself with waivers. People need to read that any animal they adopt can potentially make them sick. People are actually willing to sign those, and if you don’t warn people, you could potentially be negligent. I found out there are attorneys who specialize in salmonella! Additionally, shelters should have signage warning the public about the risk of zoonotic disease before they enter an animal housing area. It really doesn’t scare people off, and it is particularly important to warn of the risk to children, pregnant women, and those with weakened immune systems from an organ transplant or diseases such as cancer or HIV infection.
  • Educate your staff and clients. You can never stop doing that. You have to keep going over and over the safety rules.
  • Keep careful records. We had good records but we needed better—you need to know every kennel or foster home an animal stayed in and when it went there.
  • Plan adequate space for cats. We have some holding rooms that were just built too small for the number of cats. Everybody seems to understand that dogs need to be in these big rooms, but cats are often an afterthought.
  • Become compulsive about cleaning. Watch staff repeatedly to make sure it’s being done right.
  • Take the risk seriously. Those of us who work around animals all the time tend to develop a callous attitude about zoonotic disease risks. Everyone is potentially susceptible, and there is always the possibility that a previously unknown disease could enter your shelter.
  • If you have an outbreak, shut the doors until you know what’s going on. I know that’s hard for an animal control facility, but it’s critical to prevent an even bigger problem. We isolated new intakes in cleaned rooms as soon as possible, and tried to avoid picking up cats as much as possible until we had things under control.
  • Take advantage of all the entities that can help you. Don’t hide.
  • Hang in there. If we hadn’t had the competent staff and a willingness to work on this, we might have just been shut down.
Although the outbreak of Salmonella at the Idaho Humane Society was particularly dramatic, it is by no means unique. Virtually all shelters feel the pressure of too many cats with too few adopters. Too often, this leads to overcrowding, less careful cleaning, and sick cats mixed with the general population. Add a dash of bad luck, and you have a perfect recipe for infectious disease disaster. Almost every week, I hear from another shelter that has been struck by panleukopenia, ringworm, virulent calicivirus, or a variety of other infections that target crowded, stressed-out cats. The results are devastating, even when no human infections are involved. Luckily, we don’t all have to learn this the hard way. As Jeff discovered, the measures designed to prevent a recurrence of salmonella also led to healthier cats overall and more successful adoptions. There’s no need to wait for a near-fatal outbreak to prioritize cat health. —Kate Hurley


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