Worms & Germs Blog

West Nile Virus in Ontario Horses

Posted in Horses

Two Ontario horses have recently been diagnosed with West Nile virus infection, prompting the equine health advisory below from the Ontario Ministry of Agriculture Food and Rural Affairs. That’s not too surprising, as now is the typical time of year that we start seeing this mosquito-borne infection in Ontario. West Nile numbers in both humans and horses tend to vary year-to-year. There’s been some suggestion that this might be a bad year for West Nile virus based on mosquito pool testing, but predicting West Nile infections is far from an exact science, as a multitude of different factors are involved.  Only time will tell whether it’s going to be a bad year or not.

Regardless, West Nile remains a relatively rare disease in Ontario, but one that’s best avoided if possible. That involves mosquito control and mosquito avoidance, for both horses and people.

Ontario Rabies Update

Posted in Other animals, Rabies

Here’s the latest map of the terrestrial rabies cases in southwestern Ontario.  Raccoon-variant cases still centre on the Hamilton area.  It was never assumed that this particular outbreak would be eliminated quickly, given the case numbers seen in the first several months and the additional challenges of trying to control the spread of the virus in an urban (vs rural) wildlife population. The Ontario Ministry of Natural Resources and Forestry (MNRF) has a multi-year plan to hopefully (re-)eradicate this rabies virus strain from the province. Over 270,000 oral rabies vaccine (ORV) baits have been dropped so far in 2017 alone as a major part of the control program, with more to come in the fall.  In 2016, over 1.6 million ORV baits were dropped, and over 4500 animals were tested.  The map also shows the much smaller number of fox-variant rabies cases that have been detected in Perth County, Huron County and the northern part of Waterloo region. Baiting will be done in all of these areas as well.  For more information on rabies in wildlife and the baiting schedule, visit https://www.ontario.ca/page/rabies-wildlife.

Barn > Deck > Garage > Attic: Cat Migration and Kitten Care

Posted in Cats, Deworming, Other diseases, Parasites, Toxoplasmosis

I’m not sure I wrote about it at the time, but last spring we adopted Rumple (technically Rumpelstiltskin, pictured below… rough life) from the Guelph Humane Society as part of their Barn Cat Adoption program. He quickly migrated from the barn and set up shop as a garage and deck cat (which also lead to an unintended 12 hr, 100 km round-trip excursion when he hitched a ride from someone who left their car door open for a minute while at the house… but that’s another story and an example of the value of microchips).

Out of the goodness of his heart, Rumple adopted a wayward young female feral cat this spring. Not long after, she kept getting bigger and bigger, disappeared for a couple days, then came back much smaller. That answered the “pregnant vs abdominal disease” question.  (For the record, Rumple’s not to blame for that, since cats are neutered, vaccinated and microchipped as part of the barn cat adoption program.) We weren’t sure where the kittens were or if they were alive.  Five weeks later, I saw her trotting in from the field with a kitten in her mouth, relocating them from the birthing spot to our attic (which also required maneuvering up an extension ladder to get there).
So, we now have 6 kittens living above our garage, and we need to think about a preventive medicine plan.

I’ll start with deworming. These kittens look pretty healthy so far – actually very healthy for feral kittens, probably because of limited cat density in our rural area. They don’t have the classic pot-bellied (worm filled) appearance, but they are presumably harbouring parasites. Neonates are the highest risk group for a variety of parasites. They can be exposed early in life, develop significant parasite burdens in a short time, and are at greatest risk of health complications as a result. They also pose the greatest risk of transmission to people since they are often handled very closely, and more apt to poop just about anywhere. (That doesn’t mean they should be totally avoided as biohazards. My kids are having a great time trying to socialize the kittens – a little common sense and handwashing are key.)

Because of the greater risk during this period and the likelihood of a greater worm burden, we’re more aggressive with deworming youngsters. I was able to (semi-effectively) treat their mom during what we now know was pregnancy, with a topical dewormer. Ideally, we’d have started deworming the kittens starting at 2 weeks of age, and repeating at 4, 6, and 8 weeks, followed by monthly treatments until 6 months of age. This obviously wasn’t possible since they weren’t accessible for those first time points. Now that we have access to them (when we can catch them… another potential issue at the moment), the process can start. There aren’t specific guidelines for what to do when you start deworming older kittens, but every two weeks for the first 3-4 doses, then monthly until 6 months of age is reasonable. Hopefully they’ll all be re-homed by then anyway. Mother cats can get reinfected during this period from kitten feces, so Alice will get treated a few more times as well.

Among the future priorities… corralling the kittens so they can be treated and socialized more easily, vaccinating, finding homes for them (despite the daily requests from my kids to keep them) and getting Alice spayed, since as much fun as kittens are, there’s not exactly a shortage.

Psittacosis From A Horse

Posted in Horses, Other diseases

I’ve had this paper from One Health (Chan et al 2017) on my “to blog” pile for a while, since it’s an interesting story. Like any case report, it’s a bit of an oddball infection, and not likely indicative of a major or new risk. However, there are often a few good general take-home messages from reports like this.

The paper describes five human cases of psittacosis (Chlamydophila psittaci infection) linked to contact with fetal membranes of a horse. Psittacosis is a potentially nasty bacterial infection that is usually linked to psittacine birds (parrot family). This bacterium can be found in other species periodically, but it’s rare, and horse contact doesn’t trigger much thought about psittacosis.

The mare foaled on a stud farm, where two people were in attendance and a 3rd examined the fetal membranes after foaling. That’s a common procedure to make sure they are intact, since any membranes left behind in the mare can cause serious complications. The membranes appeared abnormal and the foal died a week later (but testing of the foal was not performed).

The fetal membranes were taken to the local vet school by one of the farm personnel (who was also a vet student), and they were examined by two staff and three students.

Five of the nine people that had contact with the fetal membranes developed psittacosis, and the timing of when they got sick was consistent with exposure at the time of fetal membrane contact. Risk factor analysis was performed and direct contact with the membranes was the only thing that was significant, and no other reasonable sources (e.g. bird contact) were identified.

Two of the five affected individuals were hospitalized, but everyone recovered.

Anytime there’s an outbreak, it’s good to look back and see what could be done differently. It doesn’t make much sense to look at psittacosis-specific prevention measures around horses since this is such a rare problem.  There has to be a balance between what’s practical, what people will actually do, and what might help (e.g. farms aren’t going to have biosafety cabinets to examine fetal membranes, so looking to recommendations for handling infected bird tissues has some limitations). Therefore, we’re left focusing on more general practices that could potentially protect people in a scenario like this, but that are also more broadly useful. A lot of it comes down to attention to hygiene, especially hand washing. Wearing routine personal protective equipment or dedicated clothing to reduce contamination and tracking around of microbes, handling items in a manner to reduce splashes (e.g. gentle handling, not tossing the placenta around), cleaning and disinfecting equipment and areas that might be contaminated, and hand washing would go a long way.

The “Antibiotic Course” Has Run Its Course

Posted in Cats, Dogs, Horses, Other animals

It’s commonly been stated that it’s important to finish your course of antibiotics (whether “your” refers to a person or animal), as a means of reducing the risk of developing antibiotic resistance. That’s never made much sense to me, since more antibiotic exposure is more likely to lead to a risk of resistance emerging. However, it’s been dogma.  The issue was addressed a few years ago in the ACVIM Consensus Statement on Antimicrobial Use in Animals. It also comes up in some working group that I’m in regarding antimicrobial use in humans and in animals, as messaging is starting to move away from “complete the course.” It’s a challenge though, since we don’t want treatment stopped too early (reducing effectiveness), but we also don’t want treatment to continue for days after it’s not needed.

A recent article in the BMJ, “The antibiotic course has had its day”(Llewelyn et al 2017) hits on the same topic. I’d recommend reading the whole article if you’re interested in the subject. Some of the more interesting aspects and comments are outlined below (italics are verbatim text from the paper):

  • However, the idea that stopping antibiotic treatment early encourages antibiotic resistance is not supported by evidence, while taking antibiotics for longer than necessary increases the risk of resistance.
    • Yet, there is often clinician fear. Basically, sometimes (consciously or not) people think that if the patient fails to respond to treatment, it’s a failure and is the clinician’s fault if they went with a short treatment course. If antibiotic resistance developed because of an excessive course of antibiotics, that’s seen as the drug’s fault, forgetting it’s the clinician that prescribed it. Fear of immediate and obvious patient outcome problems (even when unsubstantiated) typically overwhelm less obvious concerns about resistance.
  • Fundamental to the concept of an antibiotic course is the notion that shorter treatment will be inferior. There is, however, little evidence that currently recommended durations are minimums, below which patients will be at increased risk of treatment failure.
  • Historically, antibiotic courses were set by precedent, driven
by fear of undertreatment, with less concern about overuse. For many indications, recommended durations have decreased as evidence of similar clinical outcomes with shorter courses has been generated.
    • This applies in veterinary medicine too. I work with a few guidelines initiatives and getting people to buy into shorter durations has been a challenge. We’re making progress but fear of undertreating persists in some people.
  • For most indications, studies to identify the minimum effective treatment duration simply have not been performed.
  • Of note, a recent clinical trial found that using fever resolution to guide stopping antibiotics in community acquired pneumonia halved the average duration of antibiotic treatment without affecting clinical success.
    • This raises some interesting thoughts about when to stop. Focusing on how people feel or what they see in their animals as an indicator to stop may provide a more appropriate, tailored treatment, by stopping when the infection is gone. Sometimes. For some diseases, the time to stop is probably the time that the patient feels better or signs such as fever abate. However, there are probably others that need slightly longer treatment, since improvement in signs of disease doesn’t necessarily mean the infection is completely controlled. Here’s where more research is needed.

Their conclusion:

Research is needed to determine the most appropriate simple alternative messages, such as stop when you feel better. Until then, public education about antibiotics should highlight the fact that antibiotic resistance is primarily the result of antibiotic overuse and is not prevented by completing a course. The public should be encouraged to recognise that antibiotics are a precious and finite natural resource that should be conserved. This will allow patient centred decision making about antibiotic treatment, where patients and doctors can balance confidence that a complete and lasting cure will be achieved against a desire to minimise antibiotic exposure unimpeded by the spurious concern that shorter treatment will cause antibiotic resistance.

H7N2 Influenza in a New York Animal Shelter: A Recap

Posted in Cats

The 2016 outbreak of H7N2 influenza in cats in a New York shelter, with transmission to one veterinarian, got a lot of attention, including a few posts on our blog. H7N2 influenza is known to have been circulating in birds in the US since at least 1994, and two human infections had been identified (a person involved in culling infected birds in 2002, and an immunocompromised person with no bird contact in 2003). However, the strain hadn’t been identified since 2006.

A recent paper in Clinical Infectious Diseases (Lee et al 2017) provides information about the transmission and public health response during this most recent outbreak. Here are some highlights:

  • The index case was a cat that was admitted to the Manhattan, NY shelter 12-Nov-2016. It died Nov 25, and tested positive for H7N2 influenza virus.
  • Widespread (no details, though) infection of cats was subsequently identified in the shelter, with no infections detected in dogs, chickens or rabbits.
  • 385 people adopted a cat from the shelter between Dec 15 and Dec 21. Of those, 188 were contacted and agreed to be interviewed. Three of them had experienced disease potentially consistent with influenza and were tested. All were negative (but they only tested for virus shedding, which doesn’t last long, so I wouldn’t consider that definitive).
  • 265 people worked or volunteered with cats at the shelter. Between Dec 16-18, 165 of those were interviewed and tested. 24 had experienced flu-like illness and influenza virus was detected in one, but it was seasonal flu (H3N2) so not associated with the cats.
  • On Dec 19, a veterinarian who had helped collect throat swabs from healthy cats at the shelter reported flu-like signs. The vet had prolonged exposure to cats during sampling and did not use a mask or other respiratory precautions.  H7N2 influenza infection was diagnosed, treatment with oseltamivir (Tamiflu) was prescribed and the person recovered uneventfully.
  • The viral isolate from that vet was nearly identical to that from the cat. Those viral isolates were similar to the H7N2 strain that was circulating in birds in the early 2000s and those that caused the two earlier human infections.
  • No human-human transmission was identified among the vet’s contacts. The same day the vet got sick (often the peak time of virus shedding) the person traveled by commercial airline. Some contacts on the plane were reached and no illness was detected.

This report highlights a few interesting issues.

  • Infection with this flu virus had not been detected in many years. Where it came from is a great and unanswered question.
  • Infection of the cats was also very notable, since they were not known to be susceptible. This should be a reminder that “not knowing” whether a species is susceptible to a flu strain is not the same as “knowing that they are not” susceptible.
  • It’s surprising that, in the course of a flu outbreak investigation, typical infection control precautions (e.g. wearing a mask) weren’t taken when cats were being sampled.
  • The human infection is likely one of these oddball infections that occurred because of a confluence of factors (e.g. a cat happened to be shedding a lot of virus, the person did things that increased exposure, their immune system didn’t handle exposure like it would most of the time), particularly since no other people were identified as having been infected.

Fortunately, the outbreak in cats ended and only one person was affected. The H7N2 strain didn’t cause serious human disease or spread widely, which is always the concern with zoonotic influenzas. A big concern with flu is if a new strain becomes able to infect another species, and it causes serious disease and spreads widely, it could have devastating effects. The fact that seasonal flu (one that spreads readily in people) and H7N2 were present at the same time in people associated with the shelter shows the potential for flu viruses to meet up and potentially swap RNA.  That’s part of the reason why influenza in animals is tracked carefully in most regions.

Close Encounters of the ‘Tick’ Kind…Your Pet, Pathogens & Lyme Disease

Posted in Dogs, Horses, Other diseases, Parasites

Guest Blog by Dr. Michelle Evason DVM DipACVIM, and current PhD student researching Lyme disease in dogs

Recently, an interesting article on pet ownership and human tick risk was published (Jones et al, Zoonoses and Public Health 2017). The study looked at risk factors for “tick encounters” in people living in Lyme disease endemic states in the US.

Somewhat unsurprisingly (for anyone who likes to pet & play with their pets or allows them outside), the study found that people who owned pets had 2x the risk of finding ticks crawling on them (and 1.5x the risk of tick attachment) compared to households that didn’t have pets. While I’m really hoping that anyone reading this doesn’t decide that getting rid of their dog, cat, horse or other is my recommendation to solve this concern… I am REALLY hoping that people DO consider protecting their pets from tick attachment through the use of veterinary approved prevention methods (if they aren’t already), regular tick checks of their animals (especially prior to letting them sleep on the bed), and also strongly hoping that people consider protecting themselves (and their children) with tick prevention methods when they are outside (with or without their pets) in areas that are higher risk (e.g. forest, long grass) or if they live in declared Lyme endemic regions of Canada.

Ticks are a hot topic in parts of Canada, as they’re spreading pretty steadily across some parts of the country. There are lots of ways to prevent Lyme disease (or a number of other tick-borne diseases), and still enjoy the beauty and bounty of the Canadian summer and fall… and they all begin with awareness of why and how disease occurs. Right now, in Canada one of the increasing causes of clinical infectious disease illness in people and their dogs (and horses) are TICKS! This link from the CDC is a great guide to ways to provide protection from ticks in humans, and your veterinarian is an excellent guide to information on prevention for any 4 legged friends you may choose to co-habitate with.

As plenty of you know, there is a current lack of consensus regarding many of the clinical questions (diagnosis, treatment, prognosis) the veterinary community has about dogs (and horses) infected with Borrelia burgdorferi, the agent of Lyme disease.

These clinical questions about Lyme disease exist across species (i.e. canine, equine and human) and while I am frequently confused about what the term “One Health” actually means, if I get to choose a definition this would be it: Various animals (yes –  humans are animals) infected with the same bug and getting a similar disease from it. So, it’d be great if we could all just team up and pool our knowledge on the topic. To be fair, Lyme is an extremely difficult disease to research outside of the lab; clinical Lyme disease is very hard to reproduce experimentally and we think only a very small percentage of dogs exposed to Borrelia burgdorferi via Ixodes tick bites develop disease. Furthermore, it’s not as if zero research on this particular pathogen is occurring, and if it was an easy disease to study we’d already have the answers to these questions… and it’s pretty clear by now that we just don’t.

Wouldn’t it be great if someone (or a group of someone’s) came along and decided to develop a study that followed young dogs along and watched, looked and listened to their devoted owners and veterinarians about what happened if/when they were bitten by a tick carrying the agent of Lyme disease, so we could move past (or try to) this lack of consensus and information and find some answers for all of us? Unfortunately, studies like this are hard to do, mainly because it’s tough to get people to take the time to enroll, answer questions and then do so repeatedly. It’s also tough to get funding for research that takes this kind of time, and as such longitudinal/lifetime studies are challenging to perform and to some degree are a total academic gamble. On the other hand, research studies like this have been attempted and done quite successfully in humans, such as the groundbreaking Framingham heart study and more recent Guelph Family Health Study.

Both of these have helped (and likely will continue to help) answer a great number of clinical questions that have paved the way to clearer understanding of disease, and perhaps even more importantly prevention. That’s why we’ve recently launched the Canadian K9 Lifetime Lyme Study and are part of a similar initiative in the USA, to try to answer some of these questions. More to come on those…

Rabid Horse: Minnesota

Posted in Horses, Rabies, Vaccination

If a horse comes into the hospital at this time of year and has some difficulty standing, incoordination and mild fever, the first thing on my list of likely causes is probably equine herpesvirus type I (EHV-1) infection. Next would be West Nile virus encephalitis. However, we consider all sudden onset neurological disease cases in Ontario to be rabies suspects, just in case.

Rarely is it actually rabies, which can lead to less attention to the potential for rabies infection and sometimes an approach of “we’re calling it a rabies suspect because we have to, but we really don’t think it’s a big deal.” That can lead to less care with infection control practices. However, even though it’s rare, it still happens. A recent case of rabies in a horse in Minnesota should be a reminder of that.

The scenario was similar to that described above: the horse had a hard time standing, was incoordinated, had facial spasms and a low grade fever (facial spasms would get me thinking more about West Nile since that was a pretty common sign when we saw the first wave of equine West Nile cases here in Ontario in the early 2000s). The horse was euthanized after failing to respond to treatment, was tested and was positive for rabies. Post-exposure prophylaxis (PEP) was recommended for the owner, three family members, the vet and a vet student.

As is common, a clear source of infection wasn’t identified. A skunk source is suspected because skunks are a rabies reservoir in that region, and the owner reported smelling a skunk in the area a couple months earlier (consistent with the rabies virus incubation period).

There’s no mention of whether the horse was vaccinated against rabies. I’d guess that it wasn’t, since rabies vaccine is pretty effective. While rabies is rare, this is a good reminder of the need for vaccination against this almost invariably fatal zoonotic infection, and the need to approach neurological horses with care.

Fatal viral infection from a cat?

Posted in Cats

One thing that’s a given with infectious diseases is that there’s always something new to learn. Interestingly, I had a couple enquiries about an obscure virus last week, and was subsequently sent a link to a news report about the same disease: severe fever with thrombocytopenia virus.

As the mouthful of a name suggests, the virus causes a syndrome characterized by severe fever with thrombocytopenia (low platelet count). It’s a tick-borne virus that was initially found in China.  The reported mortality (death) rates range from 6-30%, which would make it one of the more serious infectious diseases one can get. However, like many “rare” diseases, it’s possible that it’s actually more common and less severe overall than we realize. If only people who are very sick get tested, that biases the death rate to a higher level. It’s possible (although completely speculative on my behalf) that many other people get sick, get better and never get diagnosed (or possibly even get infected and never get sick at all). It’s a possibility we always have to consider when interpreting death rates from rare diseases.

The news report involves a woman from Japan who died last year from this disease. The unique aspect of this case is that she was caring for her sick cat, and was bitten by the cat. She didn’t have any known tick exposure so doctors hypothesized that the cat was the source. However, it’s not known whether the cat was infected or whether it can be spread by a cat bite. That leaves this very speculative but something to consider.

While it’s unclear whether the cat was the source of infection in this case, it’s a good general reminder of the need to use basic hygiene practices around animals (especially sick animals), to take care to reduce the risk of bites and to promptly and thoroughly clean bite wounds. That doesn’t prevent all infections, but it can reduce the risk.

Clostridium difficile, hospital visitation and dog risk

Posted in Dogs

A reader has been trying to post a question about an older post on C. difficile in visitation dogs. Here’s the question and my answer:

Do the dogs have a risk of getting sick from the C. difficile bacteria?  I understand from the post that they can ingest and shed it in their feces, but the post never states whether they can get sick from the bacteria or not!

It’s a great question, and it lacks a similarly great answer. We don’t really understand C. difficile in dogs. We’ve made an association between the presence of C. difficile toxins in feces and the presence of diarrhea in dogs, but there are a few things that cloud our understanding of whether C. difficile is actually a significant problem. My guess is that C. difficile is a cause of diarrhea in dogs, but it’s not a major one. Or, maybe more accurately, it’s not a common cause of serious disease. It might be a relatively common cause of mild disease that gets better on its own (and therefore just doesn’t get diagnosed), but is an uncommon cause of serious disease. Dogs don’t get recurrent C. difficile infection or pseudomembranous colitis like people do, and those are the two most serious and recognizable forms of disease. Given the commonness of exposure (dogs probably ingest a small number of C. diff spores on a routine basis) and the low apparent incidence of disease (at least serious disease), it doesn’t seem to be a major health risk.