A recent CDC expert commentary was recently published on “Animal Lovers and Zoonotic Diseases: 5 Things to Know“. Regular readers of Worms & Germs will find many of the points very familiar, but the article provides a nice summary of some of the recurring themes that arise when dealing with animals and people and the infectious diseases we share. The article is great reading for healthcare providers (who are in fact the target audience), with some important reminders about the risks of not only direct contact with animals, but also indirect contact and even contact with pet food. At the very end is a link to a simple but useful 1-page tip sheet on staying healthy around pets. While certainly not exhaustive, the tips provided are certainly a good start to decreasing some of the infectious disease risks associated with pets.
There have been a few news reports about an apparent increased incidence of the fungal disease, blastomycosis, in dogs in Minnesota. Blastomycosis is an interesting disease with important “One Health” aspects. It’s caused by the fungus Blastomyces dermatitidis, that naturally lives in the soil in certain parts of the world. The risk is highly variable by region, being an important concern in some areas and a non-entity in others… and sometimes those are not too far apart, which can be a big concern for travellers.
Dogs, cats and people are among the many species that can get blastomycosis. Infection can cause a wide range of problems from severe lung disease to skin disease. It’s actually not transmitted between infected individuals, but finding it an animal (or person) is still relevant to other species, because they’re all infected the same way: from the environment. Since dogs spend more time with their nose to the ground, they’re at greater risk of exposure compared to people. So, dogs can be useful sentinels for human risk. Having a dog with blasto doesn’t mean you’re at risk from the dog, but it means you might have been exposed from the same environmental source. Knowing that can be important, since it might speed up recognition of the disease if you get sick.
Back to the Minnesota situation. A news report indicated there have been 170 cases of blasto in Minnesota dogs. (Presumably that’s a marked under-estimation, since many dogs are likely infected but not tested, as with many diseases.) While year-to-year comparisons can be a bit dodgy, because things like increased awareness can bias the results, that’s a 50% increase from this time last year, and it’s already well above the record of 155 cases set in 2017. Also, unfortunately demonstrating what I described above, there’s another report from Minnesota talking about a man battling life-threatening blastomycosis, a year after his dog died of the disease.
The situation where I live here in Ontario is less clear. We know there are “hot spots” of blasto in the province. However, unlike in Minnesota, it’s not a reportable disease in animals here. So, there’s no easy way to capture data, compare case numbers year-to-year, identify trends and see if the affected areas are changing. Blastomycosis is now reportable in people in Ontario, but the lack of centralized dog data hampers our assessment of the risks and changes to those risks.
We’ve worked periodically to track blasto in animals, and hope to get back to that shortly with our soon-to-relaunch WormsAndGermsMap. It’s all based on voluntary data, so it has some limitations, but it’s better than nothing.
Image of thoracic radiograph of a dog with lungs heavily infected with blasto (from Weese and Evason, Infectious Diseases of the Dog and Cat, A Colour Handbook).
Here’s an interesting article from the CDC about canine importation, the ways people try to avoid the rules and what’s being done to counteract these issues. Illogical, dangerous and/or illegal dog importation continues to be a problem in many countries, and many people unknowingly support it by assisting with importation or buying trafficked dogs. This article, Perspective from the field: illegal puppy imports uncovered from JFK airport highlights some important issues.
As part of our research into antibiotic use and resistance, we’re looking at what drives antibiotic prescription, use and compliance. It’s a complex subject and needs to be approached from a variety of angles. One angle is looking at what pet owners perceive or want. To address this, we’ve launched a survey designed to gather information about pet owners’ perceptions and preferences when treating their pets for an infection. The study is funded by the Ontario Veterinary College Pet Trust. The survey is voluntary and anonymous.
If you own or care for a cat and are 18 years of age or older, you are invited to participate in this survey. The survey, along with full details and ethics approval information, are available here:
We appreciate our readers’ help with this research. Our previous study about antibiotic use in dogs provided some interesting and useful information. More details about that soon….
Following up on the lighthearted rant about fake emotional support animals, it’s important to remember that animals can do great things in many situations. Dental offices weren’t really on my radar until Dr. Anne Gussgard from the UiT Arctic University of Norway contacted me about the work her team was doing with dog-assisted therapy in dental offices.
It makes complete sense, as dental offices can be anxiety-invoking for many, and the calming effect of a properly implemented dog therapy program could certainly have benefits to the patient, reducing stress or even reducing the need for sedation.
Anytime animals are brought into healthcare facilities, there are two main areas of concern: health risks to people and health risks to the animals (in this case dogs). Often the latter gets overlooked. Dr. Gussgard coordinated two papers in Clinical and Experimental Dental Research about these risks. It’s still early, and the impacts and risks still need to be studied, but the two papers highlight important issues and approaches for people considering studying or implementing dog-assisted therapy in dental offices.
(All images from Gussgard et al, Clinical and Experimental Dental Research, 2019)
I’ve written (ranted?) regularly about fake service dogs and disruptive emotional support animals. I’ve had the odd “you must hate animals” reply, but selfish people who slap a service dog vest on their pet so they can take it anywhere, just because they want to take it anywhere, cause problems for people who really need an animal with them.
Anyway, I never thought I’d be referring to Toronto Star entertainment columnist Vinay Menon in a post, but here’s his entertaining (but at the base of it, correct) take on the proliferation of dodgy support animals.
A recent study looked at human illness associated with raw pet food and has led to headlines such as “It is safe to feed raw pet foods.”
Did the study say that? No, it did not.
If you asked 100 people if they had a foodborne disease in the past year, I assume few would say “yes,” despite the widespread estimate that about 30% of people get a foodborne illness every year. If you ask people if they got a foodborne disease from a specific food, the numbers would be even weaker / lower. People generally don’t have good recall for things like that, since we don’t usually recognize a cause when we get intestinal disease. The odds of someone linking their vomiting or diarrhea to their pet’s food are low, especially if they have no awareness that their pet’s food is a risk. Even if someone thinks about the source of their disease (which probably isn’t overly common), would they think about their pet’s food as the source, versus other foods in the house, versus a restaurant, versus anywhere else they ate? I suspect the average pet owner would not.
The problem isn’t the study, it’s how the study has been interpreted. It didn’t (and couldn’t) get a good estimate of the burden of disease associated with raw pet diets. The title of the study is Owners’ perception of acquiring infections through raw pet food: a comprehensive internet-based survey (Anturaniemi et al, Vet Rec, 2019). It looked at perceptions, which is useful, but has a lot of limitations.
The study was an internet survey of pet owners who fed raw diets. Internet surveys are easy to do, but are problematic for a few reasons. When you ask 1000 people to complete a survey and 990 respond, you know you captured your population well. If 10 respond, you know you haven’t and maybe you have a biased group of respondents (e.g. people that were more motivated / biased one way or another might be more likely to respond). With an internet survey, you generally have no idea how many people got the survey, and therefore no idea what percentage of people responded. The survey was disseminated through the research group’s Facebook page and through the researchers’ own academic, private and industrial contacts, so the people invited may not reflect the typical pet owning population. That doesn’t mean the results are useless (I’ve done internet surveys myself), it just means we need to be careful interpreting results. I tend to approach surveys as tools to get some basic information to figure out what questions to address more thoroughly, rather than tools to answer specific questions.
The main question that was asked in this study was “Are there/have there been people in your household that have become sick from handling raw pet food or that have become sick from contact with a raw pet food eating pet?”
That’s a question we want to answer. However, it’s not a question the general public is well equipped to answer themselves.
- The sample size was large (16,475 households), which is good, but there’s not much information about the households to determine how reflective they are of the broader population.
- Most had been feeding raw diets for years, but some were pretty recent (e.g. 0.1 years, which is not much time for someone to get sick as a result).
- Overall, 0.2% of households reported a “confirmed” transmission from the pet or food. That’s a relatively small number, but 0.2% per year means a lot of sick people. I’m actually surprised that people reported getting sick from their pet’s food at all. I’d expect massive under-recognition and under-reporting, so seeing any reports is interesting. If you consider that in most foodborne disease, reported cases usually account for less than 10% of the real number (and probably less than that here), the true burden of disease based on these numbers is quite a bit higher, to a level I’d certainly be concerned about.
- Salmonella and Campylobacter were most the commonly reported infections. However, most of the time, there was no effort to confirm the pet food as the source, so it’s hard to say what the numbers really mean.
- In situations where there was “confirmed” transmission, 31% of the time the pet was sick at the same time. That maybe strengthens the association between human and animal disease, but also maybe shows potential bias. Are people more likely to blame the pet/food if both they and their pet are sick at the same time, and blame human food or not consider pet food if the pet isn’t sick? I have no idea, but that could greatly influence self-reported data.
- Interestingly, raw foods were handled in the same place as human food and with human food utensils significantly more often in the negative households. That’s the opposite of what I’d expect. The counter argument might be that people who handle raw pet food poorly are not tuned into the risks and are therefore less likely to identify or blame the pet food if they get sick.
The authors sum things up in a more balanced manner than internet headline writers:
“As a conclusion, this large study population from all over the world shows that the transmission of zoonotic pathogens might happen, but it seems to be sporadic. It is clear that the precise source of the pathogen is often challenging to find, which makes the interpretation of the result difficult. However, studies using different kind of approaches should be conducted in the future to be able to get a better understanding of the true risks or possible health benefits of feeding raw food diets to pets. This way the true pros and cons can be accurately analysed, before asking pet owners not to feed their pets with a nutritionally balanced raw diet.”
That’s a good conclusion. This study provides some baseline information and can help tailor future studies. It helps us figure out how to get a good answer rather than giving us a good answer now.
More information about ways to reduce the risk from feeding raw diets is available on the Worms & Germs Resources – Pets page.
Media reports have described a number of Norwegian dogs with unknown intestinal disease, characterized by vomiting and diarrhea. Cases were first reported in Oslo, with subsequent reports in other towns – whether this indicates spread of disease or spread of awareness isn’t clear. Oslo could be the epicentre of the disease, but it could also simply be the first place it was identified, based on the presence of more dogs and more veterinarians. Some affected dogs have died. Details are sparse and other information I’ve been getting doesn’t yet provide much more insight, but it’s obviously something worthy of attention.
First thoughts that come to mind for something like this are:
Is this infectious?
Even though we jump to an infectious cause, this isn’t always the case. In particular, a toxin has to be considered. This is where getting information about common exposures (places visited, food and treats affected dogs have consumed) is critical.
If it’s infectious, is it something new?
Common things occur commonly. Most “strange” disease issues end up being unusual manifestations of common problems, rather than emergence of a new problem. However, infectious diseases continue to emerge, so while we should focus on the usual suspects we still need to think about the potential for something new.
Testing for infectious intestinal diseases in dogs (and most species) can be a challenge. The gut contains a wide range of bacteria, viruses and parasites. Most of them are actually good, or are at least harmless. Some can cause disease but usually don’t, and are commonly found in healthy animals. Some are more strongly linked with disease, but rarely do we have absolute causes, i.e. something that we find and we can definitively say is a problem for that individual animal.
As a result, testing can be extensive, expensive and low yield. In a single adult dog with sporadic diarrhea, we tend not to do much testing, because it’s hard to get a clear answer and it usually doesn’t change what we do. A potential outbreak or new problem is different, and it makes sense to put more time and effort into testing to try to figure out the cause of the problem.
In situations like this, we usually work to identify the usual suspects first (e.g. parvovirus, Salmonella, Campylobacter), as well as suspects that we’ve more recently identified as being problems (e.g. NetF-producing Clostridium perfringens). Broad testing that looks for things that are less convincing causes of disease (e.g. circovirus) can be useful if results are given the proper context, realizing they might be innocuous or only relevant when another cause of disease is also present . Simply finding a bacterium, virus or parasite in a patient doesn’t necessarily mean anything for that animal. Looking at results across lots of affected individuals, comparing results to what we know about different populations, and comparing testing results and clinical patterns to those of diseases we know can get us useful information. It’s not unusual to think that there’s a new important cause of diarrhea, only to realize with further study that it’s just a harmless background bug that we hadn’t bothered to pay attention to before.
More information will hopefully be available in the near future.
Here are the answers to the latest Worms & Germs crossword puzzle. Rather than my boring answer key, here’s a key sent in by a reader, Dr. Hillary Israeli (with much better illustrations than I could do).
A recently published University of Guelph study evaluating pet poultry flocks found (unsurprisingly) high rates of shedding of certain concerning bacteria (Brochu et al, J Vet Diagn Invest 2019).
- Campylobacter, an important cause of gastrointestinal disease in people, was present in 36% of tested chickens. Salmonella was less common but present in 3% of chicken fecal samples.
- The Campylobacter shedding rate was actually higher than has been reported in commercial chickens at slaughter plants. This is in contrast to some statements you see about people not worrying about infectious diseases with small-flock chickens because they’re not from a “factory farm.” As far as Campylobacter and Salmonella are concerned, chickens are chickens.
As the authors state, “Fecal shedding can lead to the spread of the pathogen within the environment, leading to contamination of food, tools, and materials coming into contact with people, flies, and other flocks. Given that small flock poultry are often kept as pets, close contact (e.g. kissing, petting) could increase the risk of exposure further, especially for people at higher risk (e.g. children). These results underscore the importance of proper sanitation and hand hygiene measures for flock owners to protect both flocks and the public from these pathogens.”
In a related note, the CDC has updated their Outbreaks of Salmonella infections linked to backyard poultry investigation notice.
- As of August 30th, a total of 1003 people from 49 US states have been affected. Alaska is the only mainland state where cases have not been identified (the Alaskan climate probably not being great for outdoor poultry).
- 23% of affected people are children under the age of 5, as is common in outbreaks like this, both because of their close contact with animals and their increased susceptibility to disease.
- Two people have died and over 25% of diagnosed cases have been hospitalized. So, this isn’t just a case of having to spend a couple days running to the bathroom. It can cause serious disease, a fact that’s often overlooked.
- Multiple Salmonella strains are involved, and affected people have reported getting chicks from a wide range of sources, including agricultural supply stores, websites and hatcheries.
- Outbreak strains of Salmonella have been isolated from the backyard poultry environments at multiple homes, showing the potential for exposure without direct bird contact. This also highlights the potential for spreading Salmonella beyond the yard by other routes such as wildlife and runoff.
I’m not anti-backyard chickens. However, I’m against doing things illogically (or downright stupidly). Some basic common sense and infection control practices can limit (though never eliminate) the risk, but use of these precautions is likely inadequate. It’s a complex situation that doesn’t just deal with the chicken owners. It also relates to household visitors and even neighbours, since the potential for transmission of things from yard to yard can’t be dismissed. Ultimately, we need good guidance for backyard chicken owners and good compliance, and a realization that there are always risks and therefore necessary control measures. We’re working on this area but it’s not going to be a quick fix.