We’re getting ready to launch the Canadian Pet Tick Study, with funding from the OVC Pet Trust. We’ve had great response from veterinarians in Ontario, but need more clinics from other provinces, so please share this link with out-of-province veterinary colleagues who may be interested! Details are available here:
It’s easy to get complacent about rabies, even when you live in an endemic region. While we have ample bat rabies, Arctic fox rabies and raccoon rabies in Ontario, spillover into domestic animals is relatively rare. Success can breed complacency, though. When control measures work, it’s easy to forget why they are so important.
That’s my rambling but somewhat relevant introduction to a case of rabies in a dog in Ontario. The dog, from Wainfleet, Ontario, is the first canine rabies case in the Niagara region in over a decade. Contact tracing is underway to determine if any people need post-exposure prophylaxis and if any other domestic animals might have been exposed to the dog.
Typing of the rabies virus is presumably underway to determine what strain it is. We don’t have canine rabies in Canada (i.e. a rabies virus strain that is adapted to circulate in the dog population). This is presumably spillover from raccoon-variant or bat-variant rabies. Raccoon-variant rabies in this dog would be a likely given where the dog lives and the gradual spread of the virus into this region over the last few years from the outbreak that started in Hamilton in Dec-2015. Spillover into domestic animals and potential exposure of people is a reason the outbreak is a major concern, and why a lot of time, effort and money are being spent to try to eradicate terrestrial rabies again from southern Ontario.
While rabies is rare in domestic animals here (and in many regions), the threat still exists. Vaccination of pets is important to protect the animal and prevent spillover of wildlife rabies into people. More information about rabies can be found on the Worms & Germs Resources – Pets page.
A common limitation of studies or case reports of zoonotic pathogens or infections is that they are one sided – they often just discuss the human case(s), or they just report carriage of a pathogen in animals. Case reports of human infections often only go as far as saying something along the lines of “this bug is most commonly associated with dogs, so the person must have been infected by the pet dog.” Those are usually reasonable assumptions in most cases, but they’re still assumptions. Sometimes, it’s not possible to properly investigate the animal link. Most often, no one bothers.
A recent paper in Emerging Infectious Diseases (Sleutjens et al. 2019) shows what can/should be done when investigating suspected zoonotic infections. It’s a report describing a human case of endocarditis (infection of the inner lining the heart, typically involving heart valves) caused by the bacterium Streptococcus equi zooepidemicus (Strep zoo for short).
The patient was admitted to hospital with malaise and a fever, and infection involving a prosthetic aortic valve that was placed 9 months earlier was noted. Strep zoo was isolated from the patient’s blood, which facilitated appropriate and effective treatment. The patient was discharged from hospital 6 weeks later.
As you can probably guess from the “equi” part of the name, this bacterium is commonly found in horses. (It’s less commonly found in other animal species like dogs and cats, and rare human infections have been associated with those species too.) An investigation of possible sources was performed, and since the patient had frequent contact with 7 horses that were stabled at his yard, those horses were tested. Two of the horses had had upper respiratory tract infections around the time the patient got sick. Whether that’s relevant or co-incidental isn’t clear, since Strep zoo can cause respiratory tract disease in horses, but most often is found in healthy horses. Regardless, the bacterium was isolated from 4 of the 7 horses.
What sets this investigation apart from most others is the additional testing that was done. They performed whole genome sequencing (WGS) of the bacteria isolated from the horses and the patient. Not surprisingly, they were essentially the same, pretty much confirming that the horses were the source of infection. The figure below shows how the human isolate, in grey, is closely related to (and presumably originated from) the horse strain at the centre of the collection.
Strep zoo infections in people are rare, but it’s important to understand how, when and why bacteria move between species.
As the authors concluded “Systematic reporting of suspected or confirmed transmission of pathogens between horses and humans is lacking. Such reporting would support the estimation of the burden of equine-origin zoonotic infections in humans, which is needed as the equine industry continues to grow. Collaboration among disciplines to develop such a reporting system is fundamental for enabling reliable assessment of the potential risk for humans to become ill after contact with horses and the usefulness of implementing precautionary measures for patients with specific conditions.”
This report doesn’t mean horses pose any more risk now than they did before. It’s just a reminder that uncommonly, infections like this can occur.
In addition to the reporting need that the authors of the paper identify, a key step is even considering zoonotic infections. “Do you have pets or have contact with animals?” isn’t asked enough when people go to the doctor. Most of the time it’s not relevant, but occasionally it’s very relevant, and if the question isn’t asked, zoonotic infections can be missed (sometimes with fatal consequences).
Here are some more leftover questions from the talk I did a talk recently for Third Age Learning in Guelph:
As West Nile virus seems to be spreading, is there a vaccine becoming available for the general population?
Probably not, but that’s just a guess. While it should be possible to make an effective human vaccine, I suspect companies aren’t lining up to do it.
We have an effective vaccine in horses, so why not people?
It’s a lot easier and cheaper to get an animal vaccine licensed. People are probably also more willing to vaccinate their horses than themselves for a rare disease like this (especially when you consider how low flu vaccination rates are, despite how common flu is and how many people it kills).
So, I suspect this is a situation where it would be technically feasible to do, but from a market standpoint, it’s just not practical.
Stay away. I don’t mean run screaming from the raccoon, but don’t touch it.
It was probably a normal raccoon doing what raccoons do… looking for food.
It’s hard to know the exact context from the question. If the critter walked in the front door and was cruising through the public area, unconcerned about people or looking otherwise abnormal, I’d be concerned. Since raccoon rabies has yet to be found in Guelph, but it’s not too far away, we’re in an area where surveillance is important. Testing of the raccoon might be performed if it was caught. Catching it is the issue. The provincial ministry in charge of rabies in wildlife is the Ministry of Natural Resources (MNRF). The provincial agriculture ministry (OMAFRA) helps veterinarians deal with domestic animal exposures. Public health deals with human exposures. But in all cases, the animal needs to be captured and euthanized (or found dead) before it can be tested, and the only agencies equipped to deal with a live animal are local animal control. In the absence of something that indicates the raccoon is acting abnormally, I’d just steer clear.
I have two indoor cats that have never been outdoors except to visit the vet. Why do they need annual rabies shots?
This is a very common question. My initial (somewhat flippant) response is “you’d be amazed at how many “indoor” cats get hit by cars every year.” Some indoor cats never leave the house, but many sneak out occasionally. That’s a chance for rabies exposure. Even those that never leave the confines of their house can be exposed to rabies virus, as I know from personal experience with a rabid bat. It happens far more often than people realize, even in apartment buildings in the middle of the city.
Vaccination is important to protect indoor cats against rabies, even if the risk of exposure is low. Another thing to consider is the response to exposure. In Ontario, a vaccinated cat that gets exposed to rabies but gets a booster vaccine within 7 days does not require a formal quarantine period. An unvaccinated cat gets a 3 month quarantine if it receives a rabies vaccine within 7 days and a 6 month quarantine if it doesn’t get boosted in that time frame.
We dose our dogs to prevent tick bites. Is there anything for humans in the future?
I have to assume companies are looking into this. We have very effective tick preventive medications for dogs and cats. As mentioned above, it’s much easier to get a drug licensed for animals. Unlike a vaccine, lots of people would probably be interested in an oral or topical product that repels or kills ticks, if it was safe and effective. Wariness of putting “chemicals” into their body would dispel some, but I imagine there would still be market. Whether that market justifies the millions of dollars in drug development costs is presumably something companies have assessed.
I did a talk recently for Third Age Learning in Guelph, and there was an abundance of questions. I didn’t get through them all at the time, so I figured I’d address some of them here:
Do mice carry rabies?
Mice aren’t rabies reservoirs like raccoons, skunks or bats, as they don’t have a rabies virus strain that circulates in the mouse population. Like any mammal, they are susceptible to rabies and can be infected. However, most often when a mouse tangles with a rabid animal, it doesn’t end well for the mouse. If a mouse survived a bite from a rabid animal it could get rabies, but since that’s pretty uncommon, mice are low risk.
Can you talk about foot-and-mouth disease? I heard of someone recently dying from it.
This is another one of those situations where diseases have confusing names.
Foot-and-mouth disease is a viral disease that affects cloven-hoofed animals such as cattle, sheep and pigs. It’s a devastating disease for those species, but of very limited risk to people. The odd human infection has been reported but it’s not really considered to be a significant human health risk.
Hand foot and mouth disease is a completely different disease caused by a completely different virus. It only affects people, and usually, it causes mild disease characterized by oral lesions and a rash on the and feet in kids. Adults can sometimes become infected and serious infections (including death) can occur, but that’s very rare.
Do skunks pose a problem for cats that walk in the same area?
Not really. Rabies is a concern with skunks but that’s transmitted by bites, not by simply being in the same area (and cats are generally smarter about avoiding skunks compared to dogs).
A more realistic concern would be leptospirosis. Skunks can shed Leptospira bacteria in urine and that can contaminate the environment. We uncommonly see (or at least diagnose) leptospirosis in cats. It’s much more common in dogs, and can also affect people. Overall, though, the risk to cats posed by skunks being in the vicinity is pretty low.
How do you test a raccoon population for rabies?
It involves testing a sample of individual raccoons. Rabies testing in animals requires a brain tissue sample, meaning the animal can only be tested after it’s dead. Raccoon testing is routinely performed when there has been exposure of a person (or sometimes a domestic animal) to the raccoon. It’s done in these cases to make sure the raccoon wasn’t rabid, as that influences management of the person or animal that was bitten/exposed. Beyond that, testing of dead raccoons is sometimes performed for surveillance purposes, to see if raccoon rabies is present in a region. Because of the cost of testing, surveillance testing of this kind is mostly reserved for situations where there’s a concern that raccoon rabies is spreading or where the extent of the disease is being discerned.
More Q&As to follow.
See Dr. Sarah Boston (veterinary cancer surgeon extraordinaire)’s take on how veterinarians are misleading people into protecting people.
The Minnesota Department of Agriculture has recalled some lots of raw pet food from Woody’s Pet Food Deli, after linking them to a human infection. The link isn’t definite, but was obviously enough to prompt a recall.
The situation involves a person who developed salmonellosis and, as is typical, an investigation of possible sources ensued. Salmonella Reading was isolated from the person. This strain has been previously found in raw turkey-based pet food, and the affected person had handled just such a product that was fed to the patient’s dog. A fecal sample from the dog was tested and Salmonella was isolated. It wasn’t Salmonella Reading, but isolation of Salmonella from the dog was enough to cause concern, particularly given the previous linkage of this Salmonella strain to raw pet food-associated infections. If no other potential sources were identified, it’s reasonable to assume the pet food was the source.
The source of the Salmonella found in the dog was likely also the food, since Salmonella shedding by dogs is rare. Samples of raw food from the manufacturer were tested and Salmonella (not S. Reading) was isolated, which prompted the recall. An issue that comes up in investigation of raw pet food-associated outbreaks is the small production batches and the variability of contamination. By the time someone gets exposed to Salmonella from pet food, gets sick, goes to the doctor, gets tested, the result is reported and public health investigates, the batch of product that was originally fed to the dog is typically long gone. So, other batches have to be tested and even if the food was the source, subsequent batches may not be contaminated or, as is the suspicion here, might be contaminated with different Salmonella.
Finding Salmonella in raw meat is expected, and human (and animal) illnesses occur sporadically. They’re underreported and we don’t really understand the full scope of the problem. However, these infection are preventable.
I’m long past the stage where I think I can convince people not to feed raw diets to their pets. That’s a personal decision, and while I think it creates unnecessary risk and hassles, it’s going to be done by some. However, there are some households where raw diets should NOT be fed. These include households where high risk people or animals are present, i.e. individuals who are more likely to get sick and/or more likely to develop serious illness. Households with young kids, elderly individuals, immunocompromised individuals or pregnant women are high risk. The same applies to animals, so households with old, very young, immunocompromised or pregnant dogs/cats should avoid raw feeding too. I’m also wary of it in growing animals, since there are lots of cases of nutritional deficiencies when the diet being fed isn’t properly balanced for such an animal (which is tricky to do).
For people who choose to feed a raw diet, the key is using some simple precautions to reduce (though they will not eliminate) the risk. We have a fact sheet outlining these practices on the Worms & Germs Resources – Pets page.
As part of efforts to try to understand the scope of importation of dogs into Canada and what measures might be taken to help reduce the infectious disease risks, we are conducting a survey of dog importers. We invite anyone involved in canine importation activities to participate:
Dr. Scott Weese of the Ontario Veterinary College, University of Guelph is performing a study evaluating canine importation, to evaluate current practices, identify areas for improvement and evaluate areas that the canine importation community would like improved or developed (e.g. information materials, best practices guidance). As part of this study, an online survey of people who are involved in canine importation is being performed. This confidential survey will evaluate importers’ practices, perceptions and needs.
To participate in the study, access the survey by clicking here. For questions or additional information, Dr. Weese can be contacted at email@example.com.
Echinococcus multilocularis, a small tapeworm with a big name, is causing big concerns in Ontario, an area that was until recently considered free of this parasite. This tapeworm is normally found in the intestinal tract of wild canids (e.g. coyotes, foxes) and can also infect dogs. That itself isn’t a problem, since the intestinal form of the worm doesn’t make these animals sick. The concern arises when something (or someone) ingests tapeworm eggs from the feces of an animal with the intestinal infection, potentially leading to a different form of infection called alveolar echinococcosis (AE). In this form, the parasite causes tumour-like cysts to form in various parts of the body, particularly in the liver, and the condition can be very difficult to treat by the time it is diagnosed.
In the normal life cycle of this tapeworm, wild canids shed eggs in their feces and those eggs are eaten by small rodents, who develop the parasitic cysts in their bodies. When a canid eats one of those infected rodents, the life cycle continues, as the parasite grows into its adult stage in the canid’s gut and produces more eggs.
That’s bad for rodents, but the problem is that this “intermediate host” stage can occur in more than rodents – it can also occur in dogs and people (and occasionally other species).
Alveolar echinococcosis has been diagnosed in a small number of Ontario dogs (with no travel history) since 2012, raising questions about how they got infected. The concern was that this parasite might have become established in our wild canid population, which would result in ongoing and widespread risk to people and other animals, and would be hard to control.
Those concerns have been proven true, by a study just published in Emerging Infectious Diseases (Kotwa et al. 2019). For this study, fecal samples were collected from 460 wild canids in Ontario. An astounding 23% of them were positive for Echinococcus multilocularis, with infection concentrated most heavily in the western-central part of the province.
This remarkable set of results shows that this parasite is by now well established, at least in parts of Ontario, and that there is local exposure risk through direct or indirect contact with wild canid feces. Dogs that are prone to eating feces (I own one of those) or rodents (dead or alive) are at highest risk of exposure. Humans who have contact with coyote feces (e.g. hunters, trappers) are probably also at particularly high risk, but since canids live in such close proximity to people in some areas, including large urban centres, there’s a chance for exposure of lots of people through contact with fecally-contaminated outdoor sites.
What is the status of this disease in people in Ontario?
- We don’t know. The incubation period (the time from ingesting eggs to the time you get sick) is very long (typically 5-15 years). That means we may not really know what’s going on in people for some time. Since we have this parasite in wild canids and it’s spilled over into dogs, it’s almost certain that there are infected people in the province, they just don’t know it yet. That’s not meant to be alarmist, since it’s still going to be a rare disease; however, we won’t know the scope of the problem for some time. Echinococcus multilocularis has also recently been made provincially reportable in Ontario, to help us gather more data.
What can we do?
- Avoid contact with wild canids and wild canid feces as much as possible.
- Do our best to prevent and treat intestinal infection in dogs. In other areas of the world where this parasite is widespread, dog ownership has been identified as a risk factor for human infection, probably because dogs act as a bridge between households and the wildlife cycle of this parasite. We can treat dogs for tapeworms, but this isn’t usually part of routine deworming protocols, so currently only a small percentage of dogs are treated. I’ve been treating my dog with praziquantel monthly for the past couple of years, since emergence of the parasite was identified. I recommend it now, especially for dogs that might have contact with wild canids or that are prone to eating things like feces and small rodents.
A study published in Zoonoses and Public Health (Britton et al. 2018) investigated human H1N1 influenza in wild skunks in the greater Vancouver, BC (Canada) area, following up on an earlier study that found influenza virus in 2/50 skunks (both skunks had human contact). They looked at the nose, lungs and feces of 80 free-ranging skunks around Vancouver and found influenza A(H1N1)pdm09 in one skunk, which had been hit by a car. The skunk was euthanized because of the severity of its injuries and didn’t have any obvious signs of respiratory disease, but when tissues were examined histologically (under a microscope), there were signs of inflammation in the nasal passages. A flu virus was isolated and testing identified it as the human pandemic H1N1 strain.
Given the strain, it’s assumed that the skunk was infected by a person. It probably wasn’t from direct contact, but there are various ways that indirect contact could occur. One would be through garbage. It’s fairly easy to envision a skunk rooting through a garbage bag that might have contained used tissues from a person with flu. Whether a skunk can pass the virus on to other skunks (or to other species) is a question that remains unanswered
Movement of this flu strain into different animal species isn’t too surprising. It’s been found in a few species already, including household pets (dogs, cats, and ferrets). Skunks probably play little to no role in human flu transmission, and infected skunks may be “dead-end hosts” (infected individuals that don’t pass the virus on any further) or at least rarely affected enough that they don’t pose much risk for propagating infection. Regardless, this show how infectious diseases can do strange and unexpected things, and that we’re not a population of people living amongst populations of dogs, cats, cattle, birds… and skunks… but rather we’re all one big population of animals that can periodically share diseases.
So, washing your hands may not save a skunk, but it’s still good for you (and those around you, both human and animal). Flu also isn’t the reason I’d stay away from skunks – rabies and getting sprayed are far bigger issues. But the concepts of “let wildlife stay in the wild” and “leave them alone” should never be forgotten (though they sometime are).