Salmonella In Your Dog Or Cat And How To Avoid It

Ron Hines DVM PhD

You read a lot about salmonella. Its one of the most common contaminants of the food we eat. Salmonella were discovered in 1885 by the assistant to the first US-trained veterinarian, Daniel Salmon, the guy in the photo.

Salmonella infection = salmonellosis

Salmonella’s favorite place to dwell is in the two lowest portions of the small intestine (the jejunum and the ileum). Some strains seem more content in one animal species or another. But many do not particularly care in whose intestine they takes up residence. It could be you. It could be a backyard bird, a mouse, or a lizard.

In over 90% of the animals salmonella infects, it causes at the most a transient diarrhea. But after the patient recovers, salmonellas are still quite reluctant to leave. The organism has many ways to outwit the patient’s immune system – residing quiescent (quietly) in the cecum, gall bladder and/or lymph nodes associated with the digestive tract. Or residing deep within resilient intestinal biofilms. (ref)  In those quiescent situations, laboratory tests to detect their presence (bacterial culture or PCR ) often give false negatives: “None found”. (ref1, ref2)  

In other cases, salmonella bacteria simply become part of the resident bacterial population of the animal – causing no apparent harm but still able to infect other animals through their feces these carriers pass. (ref) IowaStateU.2013.pdf Salmonella shedding can also be intermittent confined to periods of stress. We do not understand much about the dynamics because so many host and bacterial factors enter into it. Most likely it is a complex interplay of the genetics of the particular salmonella strain, the immune system of the host and the types and number of the other bacterial residents of the animal’s intestine. (ref

That is why it is misleading to make blanket statements about the seriousness of salmonella to pet and human health. There are well over 2,400 strains of salmonella – each with its own individual severity and proclivities (idiosyncracies). Some salmonella that commonly affect pets uncommonly affect humans and vice versa. (ref1, ref2

In The Veterinary Arena How Important Is Salmonella To My Dog Or Cat’s Health?

Among the health threats to your dog and your cat, I consider salmonella to be very low. That so much continues to be written about them is due to several things. First, the Food And Drug Administration liberally funds human and pet food screening for the presence of salmonella and other bacteria. Second, the salmonella, that causes Typhoid fever in humans, is particularly nasty. That bacteria, Salmonella enterica does not infect dogs or cats. But in humans, Salmonella enterica does not confine itself to the intestinal tract. It causes systemic life-threatening systemic disease. Third, the common presence of salmonella bacteria in raw and fresh diets is used by the pet food industry to discourage you from preparing your own dog or cat’s diet. Fourth, and probably the most valid reason of all is that although the salmonella strains that are often found in your dog or cat rarely cause more than transient diarrhea and stomach aches in healthy human adults, they can be life threatening to infants, the elderly, and people on chemo or immunosuppressive drugs.

Because salmonella is spread through fecal contamination, it is particularly prevalent in animal shelters and group environments where large numbers of dogs and cats come and go. Those animals are under major stress. They have weakened immune systems. Concurrent infectious disease like parvo are common in those situations and proper sanitation is very difficult to achieve.

I once managed the germ-free animal colonies of the National Institutes of Health. All our animals were derived through cesarean section, maintained behind strict biological barriers and fed sterilized diets by my animal caretakers wearing biohazard suits. I saw to it that they had no salmonella exposure. But you, your dog and your cat live in the real world and are quite likely to be exposed to salmonella many times in your lives. We are fortunate in that salmonella exposure rarely causes serious health concerns.

How Resistant To Destruction Are Salmonella Bacteria?

Salmonella is a very resilient organism. It can live for several months at refrigerator freezer temperatures. It often contaminates supermarket poultry, pork and beef during the slaughtering process. The more individual carcasses are communally processed (as in ground beef, pork or chicken) the more likely it is to be present. Field contamination of vegetables is a common event as well. 

How Common Is Salmonella Infection In Dogs And Cats?

Practicing veterinarians rarely attempt to screen dogs with diarrhea specifically for salmonella. Sending off a fecal specimen to a laboratory for bacterial culture take time (72hrs+). The test is expensive and not particularly accurate. (ref)   PCR tests  might be faster, but they do not tell your vet which antibiotics are likely to work best. We know very little about the accuracy of Salmonella PCR tests in dogs. However in human cases of salmonella, the PCR test is considerably more accurate that bacterial culture techniques. (ref) So most veterinarians treat cases of diarrhea symptomatically. It would only be if your pet does not respond as expected to symptomatic treatment that a stool culture might be contemplated. So we really do not have any field data as to how common salmonella-related disease is in dogs or cats.

Studies that screened apparently healthy dog’s poop for the presence of salmonella vary greatly in the number of carrier dogs they detected. Percentages of positive dogs vary from 1% to 36%. For cats, they vary between 1% and 18%. (rptref1, ref2, ref3, ref4, ref5, ref6, rptref7, ref8 )  

When dogs and cats are found to have diarrhea and to be positive for salmonella, it is not a guarantee that salmonella is the sole cause – or even a contributing cause of the diarrhea. Any time that the intestinal tract is disturbed for any reason, the resident population of bacteria change – some increase in number, some decrease in number, new ones take up residence. And it is often less desirable bacteria take advantage of their new opportunity to proliferate.

What Factors Make A Dog or Cat More Susceptible To Salmonella Infection?

Anything that disturbs the normal intestinal flora (the microbiota) residing in your pet’s digestive tract gives Salmonella an added opportunity. (ref) These normal (symbiotic) bacteria are a very important defense against potential pathogenic bacteria like salmonella. When these helpful bacteria do not totally eliminate salmonella from your pet, they keep salmonella numbers so low that they do no harm. Recent use of antibiotics are another risk factor for salmonella infection because they kill good as well as bad members of the pet’s bacterial population. (ref)   

The second important factor is the individual abilities of your pet’s immune system. Genetics plays a large part in how robust your dog or cat’s immune system is able to recognize and combat salmonella. Key to that are your pet’s macrophages whose duty it is to recognize foreign invaders. That ability is also age-dependent and tend to be less vigorous as animals age. 

The third factor is the strain of Salmonella your pet encounters. Some are considerably more pathogenic (more virulent) than others. 

If the size of the dose of salmonella that your pet encounters has any relationship to the disease produced remains unknown.  

What Signs Might I See If My Dog or Cat Is Exposed To Salmonella?

The vast majority of dogs and cats that accidentally consume salmonella bacteria will show no symptoms at all. In their wild states, both dogs and felines are exposed to the salmonella residing in the digestive tracts of prey animals on a daily basis.   In the rare dog or cat that will show illness, the most common sign is diarrhea. That can develop the same day or as long as a day or two later. Diarrhea is in itself a protective mechanism because it expels irritating substances. But in the process, a lot of body fluids are lost. That and the fever that sometimes accompanies salmonella dehydration lead to dehydration. In those cases, your pet will have little or no interest in eating. The intestinal irritation these bacteria produce might lead to vomiting as well (vomission). In severe cases, blood might be present in the pet’s stool. A typical case lasts no more than 1-3 days. (ref

Salmonella is not known to be a cause of chronic diarrhea in dogs or cats. (ref) Westermarck2016.pdf    The most common cause of chronic diarrhea in dogs and cats is irritable bowel syndrome or IBD.  Read about IBD here

Different strains of salmonella vary greatly in their ability to cause disease. (rptref)   Some can be quite pathogenic. (ref

How Might My Veterinarian Diagnose And Treat Salmonella In My Dog Or Cat?

In a typical veterinary hospital that is rarely done. Most veterinarians treat diarrhea symptomatically. First they are confident that your pet did not eat a toxic substance. Then stool examination needs to show that your pet is free of parasites. X-rays or ultrasound need to show no intestinal obstructions. When they have those results, they are most likely to treat your pet symptomatically. They will probably give your dog or cat medications to slow, coat and soothe the lining of its intestinal tract. They will treat dehydration when present and the majority will probably dispense an antibiotic. Your veterinarian might suggest that blood and urine samples from your dog or cat be analyzed. That is not because blood samples detect the presence of salmonella. What they do do is access your pet’s general health.

It is only on the rare occasion that rapid improvement in your pet’s health does not occur that your veterinarian might send of specimens to identify bacteria in your pet’s intestine. Knowing that your dog or cat consumed a contaminated product might be a further incentive. (rptref

In attempting to find salmonella in your pet’s stool samples, your veterinarian has two options. He/she can request that the central laboratory being used attempt to grow the bacteria and determine the best antibiotic to kill it or the vet can ask that the presence of salmonella be verified using a PCR test. The PCR Test is considerably more sensitive, but it does not determine the best antibiotics to be given. (ref)   

Public Health Officials Use Salmonellas As A Reason Not To Feed My Dog Or Cat A Raw Meat-based Diet. Is That Based On Science Or Is The Risk To My Dog Or Cat Overstated?

It is overstated.

Commercial dog and cat food companies and most veterinary nutrition departments funded by them are dead set against you feeding your pet raw meat-containing diets. They use the threat of salmonella as a major talking point.

There is no doubt that raw commercial dog and cat foods have the potential to contain living salmonella bacteria (ref) Salmonella is ubiquitous in poultry. In the commercial enterprises that market raw diets, large numbers of poultry and red meat sources are mixed and processed. That gives salmonella the opportunity to disperse throughout the entire batch. In my opinion, you are considerably safer to just by whole chickens sold for your consumption. Poultry originating a even the most sanitary plants are about 8-9% positive for Salmonella. (ref)  When one of those salmonella carrying chickens is introduced into a batch of unpasteurized raw meat diet, the entire batch contains the bacteria. (ref

My solution is for you to bring your pet’s raw chicken, beef or pork diet up to a temperature of 140F (60C) for five minutes. Better yet, prepare it at home. That preserves the majority of nutrients in the food but kills any salmonella that might be present. Just in comparison, poaching= ~180F/82C, simmering= ~185F/85C and boiling= 212F/100C. The 60C temperature needs to be in the center of the meat, not the surrounding water. Of course, you will still need to ad a balanced vitamin/mineral supplement to the home-prepared diet. Read more about the effects of heat on salmonella here. 

Freezing is not a reliable way to kill salmonella.

Raw diets are never a good idea for pets with weakened immune systems. The same advice goes for feeding raw diets to your pets if you yourself are at increased risk of infection due to health issues.

What Are Some Other Things I Can Do To Lessen The Risk Of My Dog Or Cat Being Exposed To Salmonella?

If you own a cat make it an indoors-only cat. That greatly lessens its exposure to salmonella and a host of other diseases and accidents. If you own a dog, avoid taking it to places where dogs congregate. Doggy parks are great places for easy disease transfer. Dogs are extremely inquisitive about the stools of other dogs. It can be practically impossible to keep them from poking their nose in the stools of other dogs when you exercise them off leash. (ref

Offer your pet only fully baked dog and cat treats. (ref)  It is my suspicion that many of these treats were contaminated in storage after the baking process so the risk can never be entirely eliminated. I personally feed all my pets supermarket-purchased pet treats. But I limit them to products produced in America by large corporations with robust quality control teams.

When you take a trip, hire a pet sitter to come to your house. Boarding kennels are convenient locations for diseases to transfer. That goes for any facility that offers a “pet play area” as well.

Never leave food for your pets outside of the house. That attracts wildlife and rodents – both common carriers of Salmonella, other diseases and parasites. Prevent rodent contamination of food ingredients with good housekeeping and by keeping all foods in metal or glass containers. 

Avoid sharing utensils between animals. Be clean and hygienic. Soaking utensils and containers in a solution of one part household bleach and twenty parts water will kill salmonella – provided that heavy organic soiling is not present (pre-wash the utensils). 

Assume that most reptiles and amphibians (pet turtles, lizards, snakes, frogs, etc. ) carry salmonella unless proven otherwise. 

In “group-home” situations, avoid introducing new animals to the group without an initial isolation period. Whether you have pets or livestock, the old farmer’s axiom “all in – all out” helps in preventing the introduction of most diseases including salmonella.

It is not possible to reliably cleanse dogs or cats of salmonella through the use of antibiotics. 

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