Raw meat feeding revisted, part II: So you want to feed raw meat to your pet...
In a recent post, I discussed a study about the health effects of feeding raw meat diets to pets. Because of the significantly higher rates of shedding of certain potentially harmful bacteria by dogs that are fed raw meat, I think raw meat diets are a bad choice - especially in households with young children, elderly individuals or people with compromised immune systems. However, if you are going to feed raw meat to your pet, you should take some basic precautions.
- Only use meat that is suitable for human consumption. Don't buy 'adulterated' meat or meat labeled unfit for human consumption.
- Keep raw meat frozen until you need it. Only thaw out the portion that is need for the next feeding, and thaw the meat in a sealed container on the bottom shelf of a refrigerator.
- Handle raw meat with care. Do not allow it to contaminate kitchen surfaces or items that may come in contact with other food. Clean and disinfect any items that come into contact with raw meat.
- Wash your hands thoroughly after handing raw meat or anything that has touched raw meat (e.g. your dog's food bowl).
- If your pet does not finish all the meat fed right away, discard any uneaten raw meat promptly. Do not allow raw meat to sit in a bowl at room temperature. Some dangerous bacteria can multiply rapidly under these conditions.
- Regularly clean and disinfect your pet's food bowl, but bear in mind that a recent study showed that it is very hard to eliminate Salmonella from raw meat in food bowls.
- Make sure your veterinarian knows that you feed raw meat. This is particularly important if your dog develops vomiting or diarrhea.
- It is very important to make sure that your pet's diet is well balanced, which can sometimes be difficult to do when feeding non-commercial or raw diets. Read about raw meat feeding, and try to find good sources of information (which is not always easy) to reduce the risk of problems caused by feeding an unbalanced diet.
- Never feed raw meat to sick dogs, puppies or pregnant dogs.
Raw meat feeding revisited: what are the risks and benefits of raw diets for dogs?
Feeding raw meat diets to dogs is a very controversial issue. Some proponents passionately advocate these diets (e.g. the BARF diet) based on vague and unproven recommendations. Opponents cite various studies showing that pets fed raw meat (not surprisingly) have high carriage rates of potentially harmful bacteria such as Salmonella, and reports of diarrhea or nutritional imbalances in these animals. However, there have been only a few good studies looking at the true health benefits and risks of feeding these diets to dogs.
A recent study in the journal Zoonoses and Public Health described the risks of therapy dogs shedding Salmonella and other potentially harmful bacteria. The authors tested 200 dogs over a 1 year period, 20% of which were fed raw meat as part of their normal diet. Dogs fed raw meat were 23 times more likely to shed Salmonella compared to other dogs. They were also 17 times as likely to be shedding extended spectrum beta-lactamase (ESBL) Escherichia coli (a highly drug-resistant form of E. coli).
The study concluded that, because of the risk of Salmonella shedding and the high-risk nature of the patients and other people that therapy dogs interact with, dogs that are involved with hospital/patient visitation programs should not be fed raw meat.
What does this tell us about feeding raw meat to pets?
Although this study doesn't answer all of the questions about the risks of raw meat diets, it reinforces the fact that pets fed raw meat have significantly higher rates of shedding of potentially harmful bacterial such as Salmonella and antibiotic-resistant E. coli. Eating pig ear treats has also been associated with Salmonella shedding. However, there was no association between a dog being fed raw meat and the animal itself developing diarrhea. In fact, raw-fed dogs had a lower incidence of extra-intestinal infections (combination of eye, ear, skin and urinary tract infections).
In general, raw meat diets should be avoided. While adverse health effects were not reported in this study, disease (including deaths) from Salmonella has been reported in dogs in other studies. While the overall risk may be low, feeding raw meat is an avoidable risk. However, it would be inappropriate to completely ignore the finding that raw-fed dogs had lower rates of certain infections. It is possible that there can be health benefits from feeding raw meat in certain dogs, but the potential benefits must be weighed against the potential risks to the animals and people with which the has contact. Raw meat diets should never be fed to pets that have contact with immunocompromised people (in the household or as part of visitation program), infants or the elderly.
If you are going to feed raw meat to your pet, make sure you take precautions to reduce the risk of infecting yourself or someone else. We'll post more on that aspect soon.
Echinococcus and hydatid disease - not your average tapeworm
A previous Worms & Germs post talked about the (very low) zoonotic risk of the tapeworm most commonly found in dogs and cats, Dipylidium caninum. Dogs can also carry other species of tapeworm, such as Taenia pisiformis, which cannot be naturally transmitted to people. But dogs can also carry tapeworms from the genus Echinococcus, the most common of which is E. granulosus. Echinococcus multilocularis is much less common in North America, and can also be carried by cats.
In Canada, dogs tend to be exposed to E. granulosus when they eat certain animals, particularly wild herbivores like moose and caribou. In other parts of the world, eating sheep organs is the most common way dogs are exposed. The immature form of the worm is found in the animal’s lungs, liver and other tissues. After being eaten by the dog, the worm matures in the intestine, and tapeworm eggs can soon be found in the dog’s stool. Tapeworm segments, as seen with Dipylidium infection, are usually not seen in the stool with Echinococcus. Under a microscope, it is possible to tell Dipylidium eggs from Echinococcus eggs, but it is not possible to tell Echinococcus eggs from Taenia eggs.
If a moose, caribou, sheep or another suitable “intermediate host” swallows the eggs from the dog stool, the parasite migrates through the animal’s body and forms cysts in various tissues which contain the immature form of the worm. If the animal dies or is killed, and a dog (or a wolf or coyote or related species) eats the cysts, the cycle begins again.
Unfortunately, humans can also be an “intermediate host” for these tapeworms. If a person ingests Echinococcus eggs from dog stool, the parasite can form cysts (called hydatid cysts) in many tissues and organs, including the liver, lungs, brain and heart. If the cysts are small and there are only a few, they may not cause any problems for years, and the person may never know they’re there. But as the cysts grow, they can get very large and start to interfere with the function of organs, or their size alone may be a problem, depending on where they are located. Treatment can be difficult – drugs are frequently not effective, and large problematic cysts may need to be surgically removed, if the surgery can be done safely. If a cyst bursts it can cause anaphylactic shock, which is very dangerous.
In Canada, Echinococcus infection and hydatid disease are most common in the western provinces. Nonetheless, everyone can take a few simple steps to help prevent exposure of people to Echinococcus:
- Always wash your hands after handling dog stool, even if you use a plastic bag or a scoop to pick it up.
- Your dog should have a fecal examination for intestinal parasites at least once per year, or more frequently if your dog is at increased risk of exposure to Echinococcus. If tapeworm eggs are identified, your veterinarian can prescribe medication to treat the infection.
- Monthly heartworm preventatives that are effective against other intestinal worms are not effective against tapeworms!
- Do not let your dog eat uncooked meat, especially the organs of sheep or wild game such as moose and caribou.
More information on Echinococcus and hydatid disease is available on the CDC’s Echinococcosis webpage.
Salmonella-contaminated pet food
The CDC has released the findings of an investigation of a prolonged multistate outbreak of salmonellosis that was linked to dry dog food in 2006-2007. This outbreak implicated two different dog food brands, both made by the same manufacturer in the same plant in Pennsylvania, as the source of a particular strain of Salmonella Schwarzengrund. The strain infected numerous people, and was also found in some dry dog food samples and stool samples of dogs that were fed the food, with which the affected people had had contact. No illness was reported in the pets. It is unclear whether people were infected from contact with the food or contact with the pets' stool.
This is the first report of salmonellosis associated with dry pet food. Previous outbreaks have been associated with contact with raw pet treats such as pig's ears. Overall, the risk from contact with dry pet food is quite low, although this outbreak clearly demonstrates that some risk exists. Handwashing after contact with pet food should greatly reduce the already low risk.
This report is certainly not a reason not to feed your dog or cat a commercial pet food. One concern that I have is that this report will (and already seems to) be used by proponents of raw meat diets as support for this feeding practice. Feeding of raw meat has been clearly shown to increase the rates of shedding of potentially dangerous bacteria such as Salmonella. Illness and death from these bacteria have been identified in dogs fed raw meat. The high rates of Salmonella shedding in raw-fed dogs are a significant public health concern, and these concerns have been previously reviewed. Outbreaks of human salmonellosis have not been reported in association with raw meat feeding. This could indicate minimal risk, but could equally be due to lack of identification of sporadic cases that would be more likely with raw food than large-batch commercial contamination or better hand hygiene practices associated with raw meat handling.
- The risk of Salmonella exposure is still much lower with good quality commercial pet food compared to raw meat.
- Wash your hands after handling pet food (of any variety), as well as food and water bowls.
- Care should be taken when handling animal stool to avoid any direct contact with it. Wash your hands after picking/cleaning up any type of stool, even if you use a plastic bag or a designated scoop to do so.
