Worms and Germs Blog

Ascaris lumbricoides and dogs

Scott Weese — Wed, 17 Mar 2010 16:01:33 -0500

Roundworms (ascarids) are common parasites of many animal species. In dogs and cats, Toxocara canis and Toxocara cati are the main problems. In people, it's Ascaris lumbricoides, which is often called the 'human roundworm'. It's a very common parasite that is thought to infect ~25% of the world's population. Rates are highest in tropical, developing areas with poor sanitation, poor hygiene, and as one author stated, a tendency for 'promiscuous defecation'. Basically, the more human feces in the environment and the lower the degree of hygiene, the greater the risk of inadvertently ingesting parasite eggs.

Traditionally, it's be thought that this parasite is specific for people. Occasionally, A. lumbricoides eggs have been found in the feces of dogs. The general assumption has been that dogs just ingested eggs from the environment, and the eggs are simply passing through the dog's intestinal tract. However, a recent paper has challenged that thought. In that study (Shalaby et al, Parasitology Research, 2010), adult A. lumbricoides worms were found in the small intestine of 8% of tested dogs in Egypt. The presence of adult worms means that the dogs ingested the eggs and that the eggs were able to develop to adults in the dog's intestinal tract. The adult worms were producing eggs, suggesting that dogs could be a reservoir for A. lumbricoides, beyond just spreading around eggs that they have ingested.

Overall, dogs probably play a minimal role in human infection but it's one additional dynamic to consider. The best approach to reducing the risks associated with dogs and A. lumbricoides probably don't have anything to do with dogs, however. Rather, the keys are reducing environmental contamination with human feces and improving general hygiene practices.

Raw food recall expanded

Scott Weese — Sun, 14 Mar 2010 14:51:00 -0500

Nature's Variety has expanded their recall based on more concerns about Salmonella contamination of their products. In a lot of ways, this makes no sense to me since you have to assume that raw meat is contaminated with Salmonella, E. coli, Campylobacter and various other pathogens. That's been clearly shown in studies of raw meat for humans and animals, and that's why we cook meat intended for human consumption and emphasize good food handling practices. It's also why there are concerns about feeding raw meat to pets, and the explanation for various studies showing pets fed raw meat have much higher rates of shedding potentially harmful bacteria like Salmonella. You have to assume that a reasonable percentage of Nature's Variety's food has been contaminated with Salmonella, not that this is an uncommon and preventable event.

Because of the problem or consumer concerns, Nature's Variety has announced that they will be treating all of their diets using high pressure pasteurization. Basically, this process uses very high pressures (with only a slight increase in temperature) to reduce bacterial levels. I can't find any scientific literature about the effectiveness of this method on Salmonella contamination of raw meat (it's mainly used with milk and cheese) but it should be able to greatly reduce bacterial levels in meat. That's a good thing, as long as it works. What's important to know, however, is whether it is really highly effective in this situation and whether all potentially harmful bacterial will be eliminated every time.

I'm concerned that if people think this food is "sterile" and it's not, they might not take the necessary food handling precautions. If this method usually, but not always, kills all of the bad bacteria, or if it reduces levels greatly but not completely, then there could still be the risk of infection of people and pets. This information is critical. In the absence of clear scientific data, I think we need to assume that some level of contamination could still be present (although probably much less often and at a much lower level), and make sure that proper food handling practices are used.

It's good to see this company taking measures to reduce the risks associated with raw meat feeding. Let's hope that some objective research is made available to indicate what risks might remain.

Image source: www.defendingfoodsafety.com

2009 feline H1N1 case published

Scott Weese — Sun, 14 Mar 2010 10:31:00 -0500

When the novel H1N1 influenza pandemic infected large numbers of people, it was not particularly surprising that the occasional infection was noted in pets, considering over 50% of North American households have pets, and the close nature of contact that many people have with their pets. While the few cases that occurred were highly publicized, in the end pet infections were rarely diagnosed (although that doesn't mean they were truly rare), and limited information about these cases has been available. Details regarding one H1N1-infected cat from Iowa (Sponseller et al. 2010) were recently published in Emerging Infectious Diseases.

Here are some of the highlights:

The 13-year-old cat was an indoor cat that was admitted to Iowa State University's veterinary hospital because of depression, decreased appetite and signs of respiratory disease.
Two of 3 people in the house had undiagnosed influenza-like illness a few days before the cat got sick. The cat was an affectionate pet and interacted closely with household members.
Influenza was diagnosed in the cat by detection of H1N1 influenza virus using molecular diagnostic methods (reverse transcriptase PCR) on a sample of fluid collected from the lungs.
The cat improved with supportive care alone (mainly intravenous fluids to correct dehydration).

Considering the cat lived indoors and people in the house had signs consistent with influenza, it's almost certain that the cat was infected by its owners. This isn't surprising, but it's a good example of how infectious diseases can move between people and pets, in either direction. There's no evidence that pets were a source of human infection, but if something can move from people to pets, there's certainly good reason to think that it could go back from pets to other people. This should be another wake-up call for the need to consider and investigate the potential role of pets in any emerging infectious disease, and to consider emerging "human" diseases in sick animals that might have been exposed.

The things my dogs eats...

Scott Weese — Fri, 12 Mar 2010 08:09:00 -0500

Yesterday morning, I found part of a goose carcass in the backyard.

Yesterday afternoon, I found more of it... in a pile of dog vomit on the dining room floor. (Yes, my dog's an idiot, but that's a separate story).

Between the vomiting and my dog's rather solid gut, there hasn't been any diarrhea, at least not yet, but it not an uncommon problem in most dogs after an episode like this.

Diarrhea after dietary indiscretion can be caused by a number of different factors, including ingestion of disease-causing bacteria such as Salmonella. It can also simply be from eating too much, overloading the gut with a new substance, effects of fermenting material on the intestinal tract, and other physiological causes.

The best way to prevent this kind of diarrhea is to make sure dogs don't eat anything unusual, but that may be easier said than done. If a dog does get into something it shouldn't, odds are it's not going to be a major problem in terms of infectious diseases. Most of these become typical cases of "garbage gut," the results of which are the dog vomits and maybe has some diarrhea, but is otherwise fine and gets over it quickly. Sometimes they puke once and never look back. Other times, they need to be kept off feed or be fed a bland diet for a couple days to let their system get back to normal. During this period you should be aware that, while the cause is unlikely to be infectious, there's still certainly a possibility that the dog is shedding more harmful bacteria than normal. Vomit isn't that big of a risk, particularly compared to diarrhea, but you should clean it up promptly and wash your hands thoroughly afterwards. Cleaning up diarrhea takes a little more care, as I've previously discussed.

Garbage gut is usually more of a nuisance than a major health problem. You don't necessarily need to go running to your vet every time your dog throws up after eating something, but you also need to make sure you don't miss a potentially serious problem such as ingestion of a foreign body (e.g. bones, indigestible garbage), severe intestinal infection or pancreatitis. You should go to your vet anytime you have concerns. It's particularly important to get your dog evaluated if it has persistent vomiting or diarrhea, signs of abdominal pain (e.g. hunched up stance, crying, moving around like it hurts), doesn't want to eat or drink or is lethargic. It's also wise to get to a vet quicker if your dog has underlying health problems, has a history of pancreatitis or is very young (i.e. a puppy) or very old.

West Nile virus from pony to vet student

Scott Weese — Thu, 11 Mar 2010 21:11:00 -0500

The latest edition of the journal Emerging Infectious Diseases contains an article about a South African vet student that acquired West Nile virus from a pony while performing a necropsy. Occupational exposure to infectious diseases is an inherent risk in veterinary medicine. Veterinarians know that they are at higher risk of encountering various infectious diseases and take (or should take) precautions to reduce those risks. Sometimes infections occur despite the best precautions. Sometimes infections occur because of bad practices. This report highlights the latter.

In this case, a 4-month-old pony began showing vague signs of illness, then developed neurological abnormalities and was euthanized. A necropsy (post-mortem exam) was then performed by a veterinary pathologist with the assistance of two veterinary students. As part of the necropsy, the student removed the brain and spinal cord for testing, but gloves were the only protective gear that were used. No face or eye protection was used, which is quite astounding.

The pony was eventually diagnosed with West Nile virus. Six days after performing the necropsy, the veterinary student developed a fever, malaise, sore muscles, stiff neck and severe headache. West Nile virus infection in the student was confirmed, and the viruses from the pony and person were the same type based on testing. Fortunately, the signs of infection in the student subsided after approximately ten days.

Horses are considered "dead-end" hosts for West Nile virus, meaning they cannot naturally transmit the virus. This is because horses (even severely affected ones) only have very low levels of virus in their blood, so a biting mosquito can't pick up the virus and transmit it to other individuals. However, the brain and spinal cord, particularly in a clinically affected horse, may contain very large amounts of the virus. It's astounding that a veterinary school would have a student removing the brain and spinal cord of an animal that died from a neurological condition, especially without proper protective gear, since the procedure carries a risk of splashing or aerosol exposure to the virus. Anyone performing necropsies needs to be aware of the potential risks and take appropriate precautions. The paper states that after the incident, biosafety practices were improved to include the wearing of masks and eye protection during necropsies. Well, I guess it's better late than never...

Click image for source.

This Worms & Germs entry was originally posted on our sister site, equIDblog, on 11-Mar-10.

Deworming dogs... How often?

Scott Weese — Mon, 08 Mar 2010 20:16:00 -0500

Deworming has become a controversial subject. There are numerous opposing views, strong opinions and conflicts of interest that drive a lot of debate on the subject. There's no argument that parasites can be bad for pets and some can pose a risk to people. There's no argument that we want to reduce parasite burdens in pets to improve pet health and decrease human risks. It's the "how" that causes all of the problems. Developing deworming strategies requires consideration of a several different things, including:

What parasites are in the area?
Are the risks the same all year round or are they seasonal?
What parasites pose a risk to an individual pet or what are the pet's chances of exposure? (e.g. Does the pet go outside? Is it exposed to many other animals? Are there multiple pets in the household?)
Are there any people in the household at particular risk for parasitic infections? (e.g. young children, people with developmental disorders that might be more likely to be exposed to pet feces?)

Everyone agrees puppies and kittens need more aggressive deworming, but there are a few different approaches to managing deworming in adult animals.

The Companion Animal Parasite Council advocates monthly deworming for a few reasons. One is that, based on the duration of activity of the drugs used, monthly treatment prevents establishment of significant parasite populations in the animal (and therefore also in the animal's environment). It also keeps the treatment user-friendly - it makes it easier for people to remember to treat their pet. Some concerns with this approach include its "one plan fits all" mentality, despite the fact that there are great differences in the risks between different regions, and even between pets in the same area. There are also concerns about such heavy use contributing to the development of parasite drug resistance (which is a problem in some other species like horses and sheep), although this doesn't seem to be a major concern... at least not yet.

Recent European guidelines take a somewhat different approach and use a philosophy more geared towards individual risks for each animal. These guidelines recommend that if regular deworming is used, animals should be treated at least 4 times a year, with no more than 3 months between each treatment. This is based on some research indicating that dropping treatment to 3-4 times per year had no effect on parasite levels. This approach is therefore more conservative (in terms of the number of treatments) and probably has less of an impact on the development of resistance, but it requires more organization and thought. If used properly, it's probably a good approach.

Yet another approach was recommended by a Canadian Parasite Expert Panel. With their approach, in low-risk households (both pets at low risk for parasite exposure and people at low risk of infection), treatment is based on fecal examination results or, if fecal testing is not performed, once or twice yearly treatment is recommended. In high risk households, fecal testing is recommended 3-4 times per year, with treatment based on results, or administration of routine preventive treatment at least 2, and preferably 3-4 times per year. The main criticism of this approach is that it's more complicated and perhaps prone to errors or missed treatments.

There's no clear answer, nor should there be. There really can't be a "one program fits all" approach that properly addresses the risks for all pets (and people) in all regions. Tailoring the deworming strategy to your pet, based on your pet's and your family's risk, is the logical approach. Regardless of the chosen approach, regular fecal testing is a good (and underused) way to assess what's going on with parasites in your pet, and to identify treatment failure or the emergence of drug resistance.

Monthly heartworm prevention has an impact on what you do as well, since typical heartworm preventives are also effective against roundworms and hookworms, the main parasites targeted by routine deworming. If you are in a region where heartworm is present, monthly treatment during the heartworm season is indicated, and the main decision that needs to be made is what to do the rest of the year (where heartworm isn't a risk year-round).

Composting pet waste

Scott Weese — Sun, 07 Mar 2010 09:27:00 -0500

An article in Saturday's Toronto Star discussed composting options for people without organic waste pickup or the ability to have a backyard composter. The article discussed indoor composters that can be used by apartment or condo dwellers who want to satisfy their eco-friendly side.

One of the composters they highlighted states that you can add pet waste, but that's not a good idea. Pet waste can contain a wide range of potentially harmful parasites and bacteria. The composting process can generate enough heat to kill relevant bugs, but it's not guaranteed to do so, and I'd be especially concerned about small indoor composters. Having a few nasty things in the composter itself isn't necessarily a big deal, but what happens down the line? People can be exposed to these microorganisms when removing compost. Also (and maybe more importantly) compost usually ends up in gardens and can contaminate the soil, as well as anything grown in the garden.

One of concerns is the protozoal parasite Toxoplasma gondii. Cats are the natural reservoir of the parasite and can transiently pass it in their feces, yet most people that become infected are likely exposed outside in gardens or from contact with contaminated foods. Composing may not kill toxo, and therefore lead to a risk of exposure, particularly when compost is put into flower gardens that people work in or in vegetable gardens. The risk from an individual animal is admittedly low, since cats are rarely shedding this parasite (even though most have at one point), but it's a preventable risk. There are also various other microorganisms that are potential concerns. While composting is a great way to dispose of most organic wastes, it's best to keep putting dog and cat feces in the garbage or down the toilet (and wash your hands).

If you really feel the need to compost pet waste, the safest alternative is probably to have a separate composter for pet waste that you handle differently....pay careful attention to hand hygiene after handling the compost and make sure the compost doesn't get deposited in gardens or other areas that people might frequent.

Click image for source.

Heartworm in people

Scott Weese — Thu, 04 Mar 2010 19:21:00 -0500

Heartworm is an important problem in dogs. It's a parasitic disease caused by Dirofilaria immitis and is spread by mosquitoes. It can cause serious, even fatal disease, and routine testing and preventive medication is an important thing for dogs in areas where D. immitis is present. Dogs (wild and domestic) are the natural host for this parasite, but other species can be accidentally infected, including people and cats. People become infected by being bitten by a mosquito that is carrying the parasite, having acquired it from an infected dog. Human infections seem to be quite uncommon and, interestingly, while this is a serious problem in dogs, it tends to be rather innocuous in people. In fact, the biggest problem with heartworm infection in people is the fact that it can be confused with other, more serious problems, leading to invasive testing.

After infecting someone, D. immitis works its way to the blood vessels in the lungs. This can result in a small area of inflamed tissue in the area. If a chest x-ray is taken, a "coin lesion" (a small, usually 1-3 cm spot) is often present. The parasite infection usually doesn't cause any problems in people, but lung cancer and tuberculosis can look the same on x-rays. Usually, open-chest surgery ends up being performed to get a biopsy of the area because of the concerns about cancer. In heartworm cases,the biopsy identifies the problem as D. immitis, which is much better than cancer, but the risks associated with having undergone such an invasive procedure are much greater than that of the parasitic infection itself.

Typically, treatment is not recommended in people because the infection rarely causes problems and people are "dead end" hosts, meaning they cannot pass on the infection. (Unlike in dogs, infected people don't have the parasite microfilaria in their blood, which is how the infection is passed on to mosquitoes and other animals).

Heartworm is a rare and rather innocuous problem in humans - it's nothing to lose sleep about.

Image: A diagram of a very severe case of heartworm in a dog, in which there are so many worms in the pulmonary arteries that there is "back-up" of the parasites into the right side of the heart, which is how the parasite got its common name.

Indian man's approach to rabies prevention not recommended

Scott Weese — Tue, 02 Mar 2010 17:17:00 -0500

A man from Jharkhand, India, was bitten by a dog and realized that there was the potential for rabies transmission. That's good, particularly given the huge problem with rabies in India. However, he didn't take the recommended approach of proper wound care and getting post-exposure vaccination. Rather, he killed the dog (getting bitten a few more times in the process), cut out its heart with a pair of scissors and ate it raw, exclaiming that now there would be no problem with rabies.

Not a good idea.

Rabies is widespread in India. Every year, 25 000-30 000 people die of this disease. A person in India is bitten every 2 seconds and someone dies of rabies every 30 minutes.

Every dog bite needs to be considered a possible rabies exposure. If a dog that bites someone is not available for quarantine or testing to determine whether it has rabies, post-exposure treatment is necessary. That involves an injection of anti-rabies antibodies and a series of 4 or 5 vaccines, not ingestion of the animal's heart.

Hopefully, the dog didn't have rabies and this will go down as a somewhat curious little story. Unfortunately, if the dog had rabies, there is a good chance that this person has been infected, and if infected, he will almost certainly die.

Eating an animal's heart to prevent rabies transmission may just be a bizarre belief of an unusual individual. This is something that needs to be investigated, however, because if the same belief is held by many other people in the area, they will all put themselves at risk if they are bitten by not seeking appropriate and effective treatment. Not only does killing the dog and eating its heart have no chance of preventing infection, it probably increases the risk of rabies by leading to more bites. More rabies education is often needed in problem areas, and this may be the case here.

Image: Canine heart (source: www.historyforkids.org)

Risks of Raw - More evidence

Maureen Anderson — Mon, 01 Mar 2010 09:30:00 -0500

A study by Erin Leonard of the University of Guelph and others, that has just been published in the journal Zoonoses and Public Health, once again points to the increased risk of Salmonella shedding associated with feeding raw diets to dogs. The study looked at 138 dogs from 84 households in Ontario. One-quarter of households (21/84, 25%) had at least one dog (32/138, 23.2%) that was shedding Salmonella at one time, which is considerably higher than the 1-4% of pet dogs that are typically expected to be shedding this zoonotic pathogen. Only 4 of the 32 positive dogs had any history of diarrhea in the last month, so the vast majority of these dogs had no signs that they were shedding Salmonella. Here were the study's main findings:

1. Consuming a commercial or homemade raw diet, a homemade cooked diet, or raw meat and eggs, increases a pet dog’s risk of carrying Salmonella.

Raw is raw, and by now we're hoping that people are getting the message that raw is contaminated, whether we're talking about a commercial or homemade raw diet, or feeding any raw animal products (e.g. meat, eggs). The fact that homemade cooked diets also made the list could be explained by the fact that in order to make such a diet, owners still need to start with the raw ingredients. Handling and cooking raw meat and animal products for your pet should be done with the same precautions as handling and cooking raw meat for yourself or your family. If these homemade diets were not cooked as thoroughly as they should have been, or if there was contamination of the dog's dishes with raw product, that could explain the association with Salmonella shedding. Although traditional commercial diets can also be contaminated with pathogens (usually after processing), the risk with these is much lower.

2. Testing multiple consecutive whole fecal samples greatly improves Salmonella recovery in dogs.

This is no great surprise either. Dogs (and many other species) shed Salmonella intermittently, so not every fecal sample from a Salmonella-positive dog is going to yield Salmonella on culture. The authors tested five daily fecal samples from each dog. Based on this study, the sensitivity of testing a single fecal sample in a dog (i.e. the likelihood that a Salmonella-positive dog will test positive on one fecal sample) was only 35.5%. That means almost two-thirds of positive dogs will be missed if they're only tested once. The take-home message on this point is that in order to find Salmonella in a healthy pet dog, multiple samples should be tested.

3. Having multiple dogs in a household, using probiotics and contact with livestock are important potential risk factors that need to be investigated further.

These were factors that were flagged by the authors for future investigation, because at first they seemed to be associated with Salmonella shedding in the dogs, but when the feeding of raw diets was taken into account the associations were no longer significant. A larger study, or one using a different design, will be needed to help tease apart the potential effects of these factors from feeding practices.

The bottom line: Feeding raw is risky business. Some people swear by the benefits of raw diets, but the objective evidence is lacking. There is clear evidence of the risks. In my mind, the potential up-side simply cannot outweigh the well-established down-side of feeding raw diets to pets.

Ear mites and the strange pursuit of knowledge

Scott Weese — Fri, 26 Feb 2010 14:47:00 -0500

Ear mites are a common problem in dogs and cats, particularly in young animals, as well as in strays and animals in shelters. The species of mite typically involved is called Otodectes cynotis. It is transmitted between individuals by direct contact (basically hopping animal to animal, as it does not survive for long in the environment), and causes an extremely itchy ear infection (which can get even worse if there is secondary infection with bacteria or fungi).

There are a few reports of suspected infections with Otodectes in people. Considering how common ear mites are in cats and the small number of reported human infections, transmission between pets and people is probably rare, but it certainly can occur. Most of the reports are somewhat circumstantial, involving people with itchy skin lesions that developed after a pet was diagnosed with ear mites. However, one curious veterinarian took it a step further.

Dr. Robert Lopez, of Westport, New York, intentionally infested himself with ear mites from infected animals, and described the outcome in a 1993 edition of the Journal of the American Veterinary Medical Association. First, he took a sample from the ear of a cat with ear mites and placed it in his own ear. He described the scratching sounds and movement that he could feel as the mites explored his ear canal. Severe itching developed, to the point where "sleep was impossible." The intensity of the itching and mite movement decreased over time and the infection resolved by itself within a month.

Personally, I think I would have stopped there. (Actually, I wouldn't have made it to that point, but if I did, I certainly wouldn't have tried it again.) Yet, Dr. Lopez wanted to confirm his findings so, a few weeks later, he infected himself again with mites from another cat. The same type of disease developed, although it was less severe and only lasted two weeks.

Guess what he did next - he tried again, wanting to see if the reduction in severity might indicate development of immunity. So, he infected himself a third time, with the outcome being milder disease. This suggested to him (logically so) that immunity to the mites might develop, something that fits with the fact that ear mite infestations are more common in young animals.

Self-experimentation is generally frowned upon, but has been the source of remarkably scientific discoveries, even Nobel Prize winning discoveries (e.g. the role of Helicobacter pylori in gastric ulcers in people). I don't think Dr. Lopez is in line for any prizes, but it shows how a little academic curiosity along with minimal squeamishness can provide some interesting information.

What's the relevance of all this? If your pet has signs of ear mite infestation (e.g. scratching at the ears, dirty material inside the ears), get it examined and treated. If nothing else, this needs to be done because it's a very uncomfortable problem for the pet. There's also some risk of human infection, but it's probably minimal. The mites have to make it from the pet's ear to your body to cause problems. The quicker they are treated, the lower the likelihood of this occurring. Human ear mite infestations, be they in the ear or on the skin, seem to resolve by themselves, with treatment of the animal being the most important part of control. However, it can be a pretty uncomfortable condition and one most people (with the possible exception of Dr. Lopez) would certainly rather avoid.

Stray dog rabies vaccination debate

Scott Weese — Thu, 25 Feb 2010 15:54:00 -0500

In response to an ongoing rabies outbreak, Thailand has launched a program to vaccinate stray dogs. A posting to ProMed questioned this approach.

"The authorities plan to catch stray dogs, to vaccinate them, and to release them. This is inadvisable, since rabies incubation in dogs may extend to a year, although it is mostly between 2-3 months. Catching an animal which might already be incubating an infection and then vaccinating it will not only not protect the animal but put at risk the lives of people led to believe that the animal is safe", wrote Maya Kimchi.

True, you could not guarantee that a dog that was caught was not incubating rabies, and in that case, vaccination of the dog would not be effective. However, the odds of this are very low, and it doesn't make sense to not vaccinate. The worst case scenario is you have a dog that develops rabies, that would have developed rabies anyway, but it is less likely to spread it to the other dogs you've vaccinated. There would be no risk to people vaccinating the dog since it wouldn't be infectious at that point.

"In an endemic country where there are many stray dogs and many cases of rabies in animals and humans, as in Thailand, the solution of [the problem] of stray dogs is to reduce their number and carry out mass vaccination to all owned dogs, cats, and ferrets."

The problem is the stray animals. Vaccination of pets is very much an important component, but vaccinating pets and ignoring the reservoir (stray dogs) doesn't help in the long run.

"If a country decides to avoid the elimination of stray dogs, it will be necessary to catch them, to vaccinate them, and to [quarantine] them for 6 months at a minimum, and only subsequently, together with birth control measures (castration/sterilization), release them for adoption, after registration in a database for further control."

Here's what the World Health Organization's Expert Consultation on Rabies says:

"Mass canine vaccination campaigns have been the most effective measure for controlling canine rabies."

"There is no evidence that removal of dogs alone has ever had a significant impact on dog population densities or the spread of rabies. The population turnover of dogs may be so high that even the highest recorded removal rates are easily compensated for by increased survival rates."

and

"Attempts to control dog populations through culling, without alteration o f habitat and resource availability, have generally been unsuccessful."

Culling is rarely the answer. Vaccination of stray and pet dogs, education of the public to avoid contact with stray dogs, controlling roaming of pet dogs to decrease control with strays, educating the public about the need for post-exposure prophylaxis if they have been bitten by a stray dog and ensuring that the healthcare system has the appropriate resources (e.g. available rabies antibody and vacccine) and knowledge to handle exposed individuals is the best approach.

Giardia outbreak closes shelter

Scott Weese — Thu, 25 Feb 2010 15:33:00 -0500

A Fort McMurray (Alberta) SPCA shelter has been closed because of a Giardia outbreak. Giardia is an intestinal parasite that can cause diarrhea in dogs (and other species, including people) but can also be found in about 7% of healthy dogs. Giardia infection was confirmed in four dogs in the shelter, which led to the rather aggressive measure of closing the shelter. Shelter personnel suspect that the infection started with one dog, who spread the parasite to some other dogs that were in close contact with it. Giardia is passed in stool and animals get infected by ingesting Giardia oocysts from stool contamination in their environment or water sources.

Shelter personnel speculated that "If [the first dog to be infected] went for a walk with the snow melting, of course there's lots of little presents underneath the snow, so when she goes for a walk and she steps in, say another dog's feces, and then licks her paws, she can get it."

It's pretty unlikely that old feces revealed by thawing snow were the cause, since freezing is a pretty effective way to kill Giardia. More likely, the parasite was brought into the shelter by a healthy dog, considering that a reasonable percentage of dogs are shedding Giardia at any time. Why it spread to other dogs is a different question, as is whether the other animals were sick (with diarrhea) and whether Giardia was really the cause if they were. As with any organism that can be found in healthy animals, it's hard to say for sure whether Giardia actually caused any disease or whether there was some other cause that wasn't detected and the affected dogs just happened to be shedding Giardia at the same time.

Giardia usually causes pretty mild disease that gets better on its own or with treatment. Shelter personnel stated "We are in desperate need for help from the public as far as raising funds for medical, because obviously it costs a lot of money to treat the dogs. It's a lot of money to treat an animal with giardia." It's actually pretty cheap to treat individual cases, but this makes me wonder whether they are treating all dogs in the shelter. That's not something I'd recommend because there's little evidence that treatment of non-diarrheic animals is needed or useful.

Presumably this outbreak (whether it was caused by Giardia or something else) will end soon, either because of or despite of what was done. You never know if you did something to control the outbreak or whether it just ran its natural course. If it truly was Giardia, I'd be surprised if there are more problems, but resolution of the outbreak won't change the fact that many dogs that they bring in will be shedding the organism.

Giardia is a cause of diarrhea in people, but we now know that dogs probably play only a minor role in human disease. The type of Giardia that is most often found in dogs is a dog-specific type (Assemblage D) that cannot infect people. Unless these dogs were infected with a strain that can infect people (uncommon but not impossible), there's no risk to people. Regardless, avoiding contact with stool, especially diarrhea, is still a good idea - for prevention of Giardia and other diseases.

Dog bites, the bad and the surprising

Scott Weese — Sun, 21 Feb 2010 07:24:00 -0500

Dog bites are nothing new. They are extremely common and it's not unusual to see reports of serious, even fatal, dog bites, especially in children. There have been a few reports lately that are worth mentioning.

A Pennsylvania boy was seriously bitten on the face after being invited to pet a dog at a school function. The fact that the bite occurred during what we would consider an appropriate interaction, after being invited to pet the dog by the handler and under supervision, is notable. What's more concerning is the dog was at a booth set up by an organization that trains service dogs. Let's hope this group has reviewed their temperament testing and training protocols (the lawsuit might help spur that on).

A Custom's dog bit a young girl at Dulles Airport in Washington DC. The dog was in a training exercise in the baggage claim area and bit the child in the abdomen, requiring 20 stitches. This is very surprising for a dog that would presumably have been very highly trained and evaluated. Again, a review of their training program, the circumstances of the bite, the dog's history (whether it's shown any tendency to aggression before) and the handler's actions need careful review.

A 10-day old baby was bitten and killed by the family's husky. Little information is available but this reinforces the need to take care when introducing a new baby (or dog) into the household. This would have been an unprovoked attack, considering the age of the baby and the fact that it wouldn't have been moving around and potentially disturbing the dog.

A Hamilton, Ohio woman was attacked by a dog while locking her car, receiving injuries to her ankle and thigh. Neighbours needed to help get the dog off, indicating this was a real attack, not a nip from a startled dog. The dog is still at large.

Everyone needs to be aware of the risks of dog bites. That includes dog owners and people who never plan on having a dog, because you never know when you'll be in a situation where a bite is possible. Dog owners need to recognize the potential severity of bites, and ensure that their dogs are properly trained and controlled. Parents, in particular, need to ensure that their kids know how to act around dogs (whether or not they own a dog) and make sure they supervise their children closely when around dogs.

"Be A Tree" is part of the Doggone Safe Bite Prevention Program that teaches kids (primarily elementary school level) how to reduce the risk of being bitten by dogs in everyday situations. For more information, go to their website www.doggonesafe.com, or the Doggone Crazy website, www.doggonecrazy.ca.

Distemper in raccoons and dogs

Scott Weese — Thu, 18 Feb 2010 18:18:00 -0500

The Toronto Star had a front page article today about an ongoing distemper outbreak in raccoons, and the potential effects on dogs. Toronto's not alone, as there are distemper outbreaks underway in many different municipal regions.

Distemper is an infection caused by a virus that is related to human measles virus. It mainly affects dogs, raccoons and ferrets. It can cause intestinal, respiratory and neurological disease, with neurological problems being the most severe. Vaccination of dogs against distemper is highly effective, and has greatly reduced the impact of this virus on the pet dog population.

Distemper cannot be transmitted to people, so the disease itself is only an animal health risk. However, there's an indirect effect of which people need to be aware. Rabies always needs to be considered in dogs and raccoons that have signs of neurological disease. If there is so much distemper in an area that people assume every sick (wild) animal they find has distemper, there is a risk that the odd (but important) case of rabies may be missed, leading to human exposure. It's easy to dismiss a neurological raccoon or unvaccinated dog as having distemper, and it usually is distemper (particular in light of the current outbreak), but the implications of missing a case of rabies can be severe since it can be transmitted to people and is almost invariably fatal.

If distemper is present in your area (or, really, even if it's not currently a problem):

Make sure your dog is vaccinated.
Keep your dog away from wild animals, especially ones that are acting strangely.
Keep yourself away from wild animals, especially ones that are acting strangely.
Don't do things that will encourage raccoons to move into your yard, like leaving out food.
If you see a wild animal that is acting strangely, call your local animal control agency.

Photo credit: The Star - Toronto edition 18-Feb-10

Raccoon vaccination in New York

Scott Weese — Tue, 16 Feb 2010 21:53:00 -0500

In response to ongoing problems with rabies in raccoons in New York's Central Park, a vaccination program is now underway. Raccoons are being trapped, vaccinated, tagged and then released. This is a logical response to the outbreak and one that will hopefully have a significant impact.

Trap, vaccinate and release programs can help in a few different ways. Firstly, they protect the individual raccoons that are vaccinated. However, in the bigger picture, mass vaccination is designed to protect humans and animals beyond those that are vaccinated (this is referred to as "herd immunity" - click here for a good video about this concept from a previous post). As the number of vaccinated (and therefore immune) individuals in a population increases, there's less risk of ongoing transmission of the disease (in this case, rabies), since an infected animal is less likely to encounter a susceptible (unvaccinated) individual. If, on average, an infected individual does not have a chance to infect another individual, the outbreak will eventually die out. The key is getting a high enough percentage of the population vaccinated.

For eradication of dog rabies, the World Health Organization recommends vaccinating at least 70% of dogs in a population. I'm not sure what the critical number is for raccoons, but it's presumably a similar, and reasonably high, number. Since a high vaccination rate is needed, there needs to be a concerted effort to do more than just a token vaccination program. It also helps if there's good information about raccoon numbers and distribution in the area. As long as the Department of Health is serious about this program and puts the required time and resources into it, the odds are very good that it will be successful.

(Click image for source)

Raw food recall: Salmonella

Scott Weese — Mon, 15 Feb 2010 07:29:00 -0500

Nature's Variety has recalled chicken-based raw meat products because of Salmonella contamination. After a customer complaint about "digestive problems," they tested the food and found Salmonella, prompting the recall. (For more details about the recall, click here.) In some ways, this doesn't make a lot of sense to me. If you think Salmonella contamination should be an uncommon event and a problem, you should test routinely, not wait until animals get sick. If you think that Salmonella contamination of raw meat is expected (which it is), then why test or recall? Just assume that every raw meat sample is positive for Salmonella (and Campylobacter, and E. coli). Recalling raw meat for Salmonella isn't logical. Presumably, a large percentage of the raw meat that they have sold and which they will sell in the future is contaminated, based on various studies of commercial raw meat. Handling and feeding raw meat carries an inherent risk of human and animal infections with Salmonella, Campylobacter, E. coli and other bacteria. People that feed raw meat need to understand that risk, and consider whether it's a reasonable risk for their pets and the people in the household. I don't think feeding raw meat is a good idea, but in some situations it's a particularly bad idea (e.g. when there are infants, elderly persons or immunocompromised people in the household, when the pet is very old or very young, when the pet visits high risk people).

More information about raw meat feeding can be found on the Worms & Germs Resources page.

Big gun antibiotics in pets

Scott Weese — Fri, 12 Feb 2010 19:50:00 -0500

Antibiotic resistant bacteria are a huge problem in human medicine, and they're an increasing problem in veterinary medicine. In pets, we are seeing dramatic increases in multidrug-resistant bacteria, some as a result of transmission from humans and some that are developing in animals. Regardless of the source, infections caused by resistant bacteria are a major problem. As resistance increases and we have fewer and fewer treatment options for some infections, the potential need to use certain antibiotics that are important for serious infections in humans ("big-gun" antibiotics) increases. This is a very contentious issue because concerns have been raised over the use of these drugs in animals and the potential impact on humans.

There are two extremes to the argument:

These are critically important drugs in human medicine and they should never be used in animals.
These drugs are used thousands of times a day in people and very rarely in animals, so the impact of periodic use in animals should be minimal, and failure to use them would result in animal deaths from potentially treatable infections.

I take the middle ground here. I am very concerned about antibiotic resistance (in pets and people) and I want to make sure that what I do does not have a negative impact on public health. I also realize that very rare and appropriate use of these drugs will realistically be unlikely to have any negative impact on public health, and that withholding treatment could cause animal suffering, death and prolonged infections that could be transmitted to their owners. The key, to me, is ensuring that use of these drugs is truly very rare and appropriate. At the Ontario Veterinary College, we have strict guidelines for use of "big-gun" antibiotics to try to ensure that there are used rarely and properly. For example, vancomycin can be used, but only when:

An infection is present and it is known that the bacterium is resistant to all other options and susceptible to vancomycin.
Local antibiotic administration or other types of alternative treatment are not options.
It's a serious infection that needs to be treated but it is treatable (i.e. no throwing a big gun drug at a patient that clearly has a terminal disease and does not have a realistic chance of surviving).
Approval is obtained from the Chief of Infection Control (i.e. me).

With this approach, we've only had 1 case where vancomycin was used, and that was in 2001. That's a pretty good record for a busy referral centre with a tertiary care caseload that sees "the worst of the worst." There have been a few instances when vancomycin was requested but with discussion and review of the case, better alternatives were identified. I'm certain that these guidelines have reduced the use of vancomycin and increased awareness of the problem, but have had no negative impact on patient care.

Antimicrobial resistance isn't going away. We can control it but not eradicate it. Scrutiny of antibiotic use in veterinary medicine is also not going to go away, and in some ways, that's a good thing. It should provide impetus to make sure that we improve how we use drugs, from the big guns down to our day-to-day drugs. Realistically, it's the regular use (appropriate use, overuse and misuse) of less exotic antibiotics that is having a bigger impact on antimicrobial resistance, and we need to pay attention to that as much as to the high-profile drugs.

(Click image for source)

Tiger troubles in Ontario

Scott Weese — Fri, 12 Feb 2010 19:22:00 -0500

February 14th marks the beginning of the Chinese New Year, and ushers in the year of the tiger. Coincidentally, there's been some publicity surrounding a tiger in Ontario that has nothing to do with a New Year or good fortune. On January 10, a 300 kilogram Siberian tiger killed its owner, 66-year-old Norman Buwalda, when he went into the tiger's cage to feed it. This tiger was one of many owned by private individuals or as part of dodgy roadside zoos in Ontario and across North America.

It is truly amazing how easy it is for people to obtain potentially lethal exotic animals like tigers, and how many (or most) jurisdictions have no rules against it. Tigers are beautiful and fascinating animals, but they shouldn't be pets. Exotic pets carry many risks, including injuries and infections, not to mention animal welfare issues from poor management and feeding practices. This is far from the first exotic cat to have killed its owner, and unfortunately, it's almost certainly not the last.

The latest concerns about this particular tiger involved its whereabouts. When the OSPCA (Ontario Society for Prevention of Cruelty to Animals) went to the property to investigate a complaint about the well-being of other animals, they discovered that the tiger was gone. The town's major was also unaware of the tiger's location.

Provincial police, at least, knew more, and stated that the tiger and two lions were moved to an "undisclosed location" on January 27th. I think people need to realize this isn't the witness protection program, and there's no justification for being secretive about the location of these animals. The fact that they are gone should be a comfort to neighbours in Southwold, Ontario, but what about the people that may now be living next to it? It's pretty unlikely that these animals have been moved to a proper zoo with adequate housing facilities and handlers experienced with big cats. More likely, they're in the same type of situation as before, just is a different locale.

In Ontario, you can be charged if you have a pit bull or even a dog that resembles a pit bull, but you can have a 300 kg carnivorous feline in your backyard. How does that make sense?

Rat bite fever leads to pet store lawsuit

Scott Weese — Wed, 10 Feb 2010 18:50:00 -0500

A Phoenix, Arizona man is suing a pet store after he contracted rat bite fever from a rat he had purchased. It's not surprising to see a lawsuit following a serious illness, considering people in the US often try to sue for just about anything, but I'm not sure it won't get very far. I don't doubt that the man had rat bite fever, or that he got it from the rat he purchased - the question is, is the pet store really liable? Specifically, did they do anything inappropriate?

"Rats being sold to people should not have rat-bite fever," Heitzman's lawyer, M.E. "Buddy" Rake Jr., tells New Times.

Actually, the rats don't have rat bite fever... rats are healthy carriers of the bacteria that cause rat bite fever. There are two different bacteria that can cause the disease, Streptobacillus moniliformis and Spirillum minus. Streptobacillus moniliformis is presumably the cause here since it's the main cause of rat bite fever in the US. This bacterium is very commonly found in healthy rats, with upwards of 100% of healthy rats being carriers. You have to assume that every rat is carrying this bacterium.

"It wouldn't be any different if they sold someone a dog with rabies," he says. "I'm not in the nuisance-lawsuit business - he was in rough shape."

It would certainly be a different story if the store sold someone a dog that had signs of rabies. It's possible that someone could buy a dog that had been exposed to rabies but which was healthy at the time of sale, but that's pretty unlikely. However, a big difference is that there is a highly effective vaccine against rabies. There is no such thing for rat bite fever. If a pet store sells an unvaccinated dog of unknown origin that could have been exposed, despite knowing the need for rabies vaccination, there certainly could be liability issues. Selling a rat that is carrying a bacterium that we assume most or all rats carry anyway is different.

PetCo did not immediately return telephone calls this afternoon, but in its defense, there is an information pamphlet explaining exactly how to avoid contracting rat-bite fever available on the company's Web site. ...though it seems the pamphlet's best suggestion is to not get bitten in the first place.

It would be better if everyone who bought a rat was given the information sheet, but it's a start. The fact is, the best way to avoid rat bite fever IS to avoid getting bitten by a rat! Proper rat handling is a very important aspect of disease prevention, since you can never rule out the possibility that a rat is a carrier.

Our suggestion: Don't have a disgusting rat for a pet.

Whoa. Rats can make excellent pets. They can also carry infectious diseases. However, EVERY animal can carry infectious diseases, and rats are probably no more risky than most other domestic pets. The key is to take common sense precautions to reduce the risk of injury and infection (though the risk can never be completely eliminated). For rats, this includes selection of a rat that is not aggressive or fearful, knowing how to properly take care of a rat, knowing how to take care of a bite should it happen and being aware of some diseases for which you might be at increased risk because you own a rat.

Image source: http://commons.wikimedia.org