Raw chicken linked to paralysis in dogs? A closer look

Summary:

  • A recent Australian study linked consumption of raw chicken to development of acute polyradiculoneuritis, a rare nervous system condition that can result in paralysis
  • Raw chicken itself does not cause this condition; rather, Campylobacter bacteria found in raw poultry could be a potential risk factor
  • Acute polyradiculoneuritis and/or its human equivalent Guillain-Barre syndrome has also been linked to many other potential causes, including toxoplasmosis, recent vaccination, zika virus, distemper virus, and more
  • Acute polyradiculoneuritis is also referred to as “coonhound paralysis” due to its potential to develop soon after raccoon bites in dogs
  • Most dogs recover from this condition, but the recovery process can take months
  • Campylobacter bacteria is present in stool of up to 76% of asymptomatic, healthy dogs as a nonpathogenic bacteria, however immunocompromised dogs or dogs who have been exposed to a particularly heavy load of bacteria may be at risk of bacterial infection
  • Studies analyzing the prevalence of Campylobacter bacteria in dry dog food or treat products were not located; Campylobacter is notably resistant to food processing in comparison to many other pathogenic bacteria species, therefore there may be a potential risk in dry foods or treats, but this has yet to be researched
  • Small sample size could have potentially skewed the statistical results in this study
  • Owners should be aware of the potential for increased risk of bacteria in raw pet food, obtain all raw ingredients from reputable sources, or avoid feeding raw poultry products completely if your dog is immune compromised
  • Raw feeders in Australia should be particularly careful of the source of their raw poultry products due to the apparently higher rate of diagnoses of this condition

 


 

There was an article published on 2/1/2018 reviewing a recent study done in Australia linking dogs’ consumption of raw chicken necks to developing a condition called acute polyradiculoneuritis (APN). APN is a condition that causes inflammation of nerves, which can result in paralysis. It occurs when the body’s immune system starts attacking the nervous system and damaging the protective coating on nerves. While most dogs recover from this condition [source], unfortunately it can be fatal in others.

The study was conducted at the University of Melbourne Veterinary Teaching Hospital (U-Vet hospital) between March 2015 and February 2017, and cases originated from Victoria and New South Wales. 27 APN dogs and 47 healthy dogs participated in the study. A fecal sample was taken from all dogs and the strains of bacteria were recorded. More data was obtained from medical records and owner surveys.

The abstract states:

“In cases in which the fecal sample was collected within 7 days from onset of clinical signs, APN cases were 9.4 times more likely to be positive for Campylobacter spp compared to control dogs (P< 0.001). In addition, a significant association was detected between dogs affected by APN and the consumption of raw chicken (96% of APN cases; 26% of control dogs). The most common Campylobacter spp. identified was Campylobacter upsaliensis.”

Read the study in full here.

Causes of Acute Polyradiculoneuritis/”Coonhound Paralysis”

APN is not specific to Campylobacter, or even just bacteria in general; many studies show links between Polyradiculoneuritis or Guillain-Barre syndrome (human equivalent of APN) and the onset of infections, viruses, and other causes: including Zika virus [source], H. influenzae infection [source], vaccinations [sources a, b, c], toxoplasmosis [sources ab], and more. In another study, the control group actually had more dogs with C. jejuni isolated from their stool samples than the APN group [source]. APN is also referred to as Coonhound Paralysis due to its association with raccoon bites in dogs. There is sufficient evidence that APN doesn’t have one specific cause, but rather that this condition is associated with a spike in immune response.

Prevalence of Acute Polyradiculoneuritis

APN is a very rare condition in dogs. However, it is said to be more prevalent in Australia, with one Australian vet, Dr. le Chevoir, quoted saying that he treats about 30 cases a year [source]. This seems to be significantly more prevalent than in the US, Europe, or Canada. While Dr. le Chevoir hypothesized that the higher rate of diagnosis was related to the fact that it is common in Australia for owners to feed raw diets including poultry, Australia is not the only country in which raw food diets are popular among dog owners; Raw pet food has been steadily growing in popularity for the past decade in the US, Canada, and Europe as well. There may be another geographically specific reason for the higher prevalence of APN in Australia.

Campylobacter Bacterium

The Campylobacter species isolated in the highest numbers in the study, C. upsaliensis, is commonly found as a nonpathogenic bacteria in feces samples from healthy dogs.

“C. upsaliensis is frequently found in both cats and dogs, regardless of whether the animals are sick or healthy (prevalence, 5%–66% in cats vs. 5%–48% in dogs)” [source]. Another study reported 76.2% of healthy young dogs had Campylobacter isolated from stool samples, 75% of which was C. upsaliensis [source], and another study found Campylobacter in 43% of stool samples, 86.1% of which were C. upsaliensis [source].

The shedding of Campylobacters of multiple species is common in asymptomatic dogs of all ages [source]. However, infections caused by this bacteria have been recorded in dogs, likely due to an already suppressed immune system and/or exposure to a particularly heavy load of bacteria.

Multiple studies have found no statistically significant difference in the instances of Campylobacter isolated from stool samples in raw fed dogs compared to kibble fed dogs [sources a, b], however stool samples from raw fed dogs do tend to have higher isolation of bacteria in general. Multiple studies have demonstrated a more diverse gut microbiota in raw fed dogs [sources a, b], which could be an indication that these dogs have a greater capacity to handle potentially pathogenic bacteria due to competition within the gut.

I was unable to find any studies measuring Campylobacters in commercial dry dog foods. Although it could be reasonable to hypothesize that dry dog foods would have a lesser risk of the presence of Campylobacters due to the extent of food processing, there is evidence that Campylobacters have a greater ability to survive food processing than other bacteria, often with enhanced pathogenicity [source], indicating that dry dog food products could also be colonized with Campylobacters. However, since little to no research exists measuring this type of bacteria in dry dog foods, and it is generally nonpathogenic in dogs, there is currently no way to know the extent of Campylobacters in dry dog foods.

Prevention of Campylobacter Colonization in Food & Water

Although freezing raw meat is not an effective method of killing all Campylobacter bacteria, it does significantly reduce the amount of surviving bacteria [source], especially if the meat is refrozen more than once or if the meat is frozen for an extended amount of time. In contrast to other genera of bacteria such as E. coli or salmonella, Campylobacters do not show the same decreased heat tolerance after being exposed to extreme cold [source].

Campylobacter is common in poultry, but C. upsaliensis is not typically found in chicken in high numbers. “Poultry probably has a low rate of C. upsaliensis colonization” [source], being isolated in only 1% of chicken necks in one study [source]. However, C. jejuni is very common in raw poultry. It is also commonly found in untreated water, raw milk, and other raw meats.

Instances of Guillain-Barre syndrome (human equivalent of APN) have markedly decreased in the past when further regulatory steps were taken to prevent high bacteria in poultry products in New Zealand [source]. In the US in 2011, there was a correlation of higher rates of Guillain-Barre syndrome with an outbreak of C. jejuni caused by inadequately disinfected tap water [source].

Poultry that is raised in clean conditions and properly handled during and after slaughter in a clean slaughter facility are significantly less likely to have high amounts of Campylobacter species bacteria [sources a, b]. The quality of the poultry animal’s diet before slaughter, inclusion of probiotics in the animal’s feed, and selection of breeds more resistant to Campylobacters could also reduce the colonization of commercial poultry [source].

Conclusion

APN is a very complex condition. While correlations have been established with infections, viruses, recent vaccinations, raccoon bites, and other events which trigger an immune response, the exact cause of APN is currently unknown, and the relationship of Campylobacter to APN is not yet fully understood.

Raw feeders should be aware that raw diets generally do have a higher potential to contain bacteria than dry foods. However, evidence has yet to be established that a normal amount of bacteria in raw meat actually poses a significant danger in healthy dogs. There is also a lack of research measuring Campylobacter prevalence in dry dog foods.

Owners of immunocompromised dogs should assess the risk vs benefit of raw food diets. Avoidance of raw poultry or feeding home-cooked diet may be more appropriate depending on the severity of the dog’s condition.

Raw feeders should be cautious of the source from which they obtain their raw ingredients. Raw poultry is less likely to contain a heavy load of bacteria if it has been raised, processed, stored, and handled properly. Australian raw feeders in particular should be aware of the quality of raw poultry ingredients that they are feeding their dogs and take any precautions necessary to prevent exposing your dogs to high amounts of bacteria.

All raw feeders should take care to store, handle, and prepare raw meat correctly and adequately sanitize all bowls, equipments, and surfaces which raw meat comes in contact with on a regular basis.

Although the study provided very useful information and should not be ignored, the small sample size could have resulted in skewed data, and the higher rate of APN diagnoses in comparison with other countries should be investigated further.

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