I received the following comment in response to a recent E. coli O157 and petting zoos post, and thought that it merited a post of its own.

"Why doesn’t the petting zoo owners have a fecal swab sample taken from each animal in the petting zoo and submitted for STx PCR screen testing.  If a positive is found isolate the animal and continue to monitor it.  I would assume The University of Guelph’s extension service would have some information about this."

That’s a great question. When we start talking about infectious disease risks, people often ask about testing. However, testing is not always useful and I think that’s the case here. Here’s a few reasons why:

  • Animals don’t shed E. coli O157 all the time. It’s been shown in cattle that if you sample animals regularly, you will find the bacterium in the manure some days but not others. Therefore, a single negative result does not mean that the animal is definitely negative.
  • No test is 100% accurate. While current tests are quite good, it cannot be stated with absolute certainty that an animal that is negative on a test for E. coli O157 is truly negative.
  • Even if the animals are all truly negative for E. coli O157, they may still be shedding other potentially harmful microorganisms (e.g. Salmonella, Campylobacter, Cryptosporidium ) for which people need to take the same kind of precautions as for E. coli.
  • If petting zoo operators had to pay hundreds or thousands of dollars a year per animal for diagnostic testing (a reasonable estimate if they had to do multiple tests on each animal, possibly for multiple organisms), there wouldn’t be many petting zoos around.

For any test, whether it’s being used for screening or to make a diagnosis on a sick animal, it’s critical that it be thought of in terms of "what will I do with the results." In this case, negative results would not change recommendations for running or visiting a petting zoo. I’d assume that animals could still be shedding E. coli O157 intermittently, or that they could be shedding various other pathogens, and I’d still recommend use of good infection control practices like hand washing. Efforts are best spent working on petting zoo design and hand hygiene, rather than testing the animals, because these are more likely to have a positive impact by reducing the risk of disease transmission.

Photo source: http://www.microvet.arizona.edu/Faculty/songer/diag.htm

As a veterinary internist, I’m always looking for a good excuse to harass veterinary surgeons, and a recent study we performed with Dr. Lee Burstiner (an aspiring surgeon but a good guy anyway) at the 2008 American College of Veterinary Surgeons (ACVS) conference gives me more ammunition. This study is being presented today at the European Conference of Clinical Microbiology and Infectious Diseases in Helsinki.

A few recent studies have shown that veterinarians seem to be at higher risk for methicillin-resistant Staphylococcus aureus (MRSA) carriage, likely because of their frequent contact with animals that can also carry MRSA. As part of the study at the ACVS conference, attendees provided nasal swabs (because the nose is the main site of MRSA carriage) on a voluntary basis, and filled out a questionnaire about various potential risk factors. MRSA was isolated from 17% of participants, an astounding number considering that in the general population only about 1-3% of people carry MRSA.

In previous studies of MRSA in veterinarians, including veterinary internists, equine general practitioners and swine veterinarians, it has been equine or swine veterinarians that most often harbour MRSA in their noses. Interestingly, in this study, there was no difference between equine and small animal (e.g. dog and cat) vets, which is perhaps due in part to the steady increase in MRSA carriage by dogs and cats internationally. This is one more piece of evidence indicating that MRSA exposure is an occupational risk for veterinary personnel. Colonized personnel may be  more likely to develop MRSA infections, and are also at risk of transmitting MRSA to their patients (and possibly also their family members). This reminds us yet again of the need for good general infection control and hygiene practices in veterinary medicine.

It is truly astounding that MRSA colonization is so common in veterinarians. This is a consistent result among a few different studies now, and veterinarians may be one of the highest risk groups (if not the highest risk) for MRSA colonization. Why is this the case? Why is the prevalence not as high in human healthcare personnel? From where is the MRSA coming?  From the patients presumably? How do we control it? What are the implications for the health of veterinary personnel and their families? These are just some of the many important but unanswered questions.

All this being said, you don’t need to (and shouldn’t) actually consider veterinary surgeons (or veterinarians in general) biohazardous, nor should you avoid using veterinary specialists because of concerns about MRSA. MRSA is a problem in veterinary medicine in both referral and general practices, and studies like this show the need for further research to determine why this is the case, as well as the need for general improvement in infection control in veterinary medicine.

More information about MRSA in animals can be found in on the Worms & Germs Resources page. Information on MRSA in horses can be found on our sister site, equIDblog.

I’ve written several posts about petting zoos, mainly about the potential negative aspects, although I still think they’re valuable if run properly. A major concern with these events is exposure of people to zoonotic infectious diseases, particularly harmful bacteria that can be carried by healthy animals. One of the more common pathogens that causes disease outbreaks associated with petting zoos, including severe or even fatal infections in people, is verotoxigenic E. coli, particularly E. coli O157.

A recent study by Pritchard et al. in the Veterinary Record highlights some of the concerns with this pathogen. Samples were collected from various animals on 31 different farms in the UK. They found verotoxigenic E. coli on 61% of premises. The premises selected were evaluated due to suspicion that they may have been sources of infection for people, so it’s possible that the numbers reported in the study are higher than they would be for all such farms overall, nonetheless the numbers are impressive.  Risk factors for finding verotoxigenic E. coli on a given farm were the presence of young cattle and (surprisingly) adult pigs. Verotoxigenic E. coli were most commonly identified in cattle (29%). It wasn’t surprising that cattle, especially young cattle (calves), were the most common carriers based on what we know about the bacterium.  However, it was impressive how commonly it was found in other species, including sheep (24%), donkeys (15%), pigs (14%), horses (12%) and goats (10%). On most farms where verotoxigenic E. coli was found, the same strain was identified in multiple animal species, indicating that the bacterium can be wide spread on the property. This may be because different animal species in petting zoos are often mixed together, as opposed to the situation on conventional farms where they are usually housed separately.

Does this mean we should consider petting zoos biohazardous and avoid them? Well, the answer really is "yes" and "no". We should consider petting zoos as potential sources of harmful bacteria. High-risk people (e.g. very young, very old, weakened immune system) should probably avoid them. We should also think about ways to reduce the risks, such as using lower risk species, having good petting zoo design and, most important, encouraging and enforcing hand hygiene on the part of all petting zoo visitors. As the authors of this study stated “It is also necessary to balance this small risk against the undoubted benefits of allowing the public to interact with farm animals. The risk of people acquiring an infection from animals depends more on the degree of contact and the precautions adopted than the prevalence of infection in a particular species. ”

If you get verotoxigenic E. coli on your hands but you promptly and properly disinfect them (before contaminating something or putting your fingers in your mouth), you’ll be fine. The quality of petting zoos varies quite a lot, as we showed in a previous study, and pressure should be put on petting zoo operators to have well-designed and well-run events.

More information about petting zoos can be found on the Worms & Germs Resources page.
 

The latest issue of Oprah’s magazine "O" features the icon talking about her recent puppy dog adoption drama involving canine parvovirus. It just goes to show that even the pets of the biggest celebrities in the world are not beyond the reach of common microscopic infectious pathogens.

A couple of months back, Oprah adopted two cocker spaniel puppies from a shelter in Chicago. Unfortunately, within two weeks they both came down with parvovirus infection and had to be hospitalized. I’m sure both dogs received top-of-the-line care with no expense spared, but even so one of the puppies died. The other puppy came very close to dying as well, but happily she apparently has now recovered completely and is doing just fine (or quite likely better than fine, considering who her new owner is!).

Oprah also mentioned how one of her other dogs, Solomon, also suffered from a parvo infection years ago, but that dog was over a year old when he became ill. It’s actually quite unusual for any dog to get parvo beyond one year of age – most adult dogs are not affected by the virus, unless perhaps their immune system is compromised for some reason.

These stories bring up a few interesting points to ponder:

It’s great to adopt an animal from a shelter and give a homeless animal a home. It is an act of great kindness that I don’t want to take anything away from in the least. However, it’s important to realize that you never know what shelter dogs may be carrying, nor how well vaccinated they are.

  • Even if the animals are vaccinated once at the shelter, the protective effect may be less than ideal if a properly timed vaccination series is not completed.
  • In this case the pups may have been exposed to parvo after leaving the shelter, but they could have just as easily been exposed at the shelter, which begs the question of what else might they have been carrying? Bacterial pathogens such as Salmonella and Campylobacter are also particularly common in young dogs and cats (even healthy ones), and these are potentially zoonotic agents.

Young animals, particularly from shelters, are higher risk in terms of the infectious diseases they can carry and transmit. That doesn’t mean they shouldn’t be adopted, but it does mean taking some extra precautions for the first several weeks they’re in their new home. These include being very diligent about controlling stool contamination of any kind (which can be easier said than done during the house-training phase), preventing contact with high-risk individuals (e.g. young children, the elderly, anyone with a weakened immune system) and lots of handwashing on the part of everyone involved with the puppy (or kitten!).

Parvo is a very serious disease in puppies, yet people sometimes become a little complacent about vaccinating for parvo and other puppyhood diseases.   Remember, though, that the reason parvo has become so much less common than it used to be is largely because of widespread and effective vaccination.  I have to wonder about how well vaccinated Oprah’s dog Solomon was to get the disease at the age he did, but there could easily be other factors involved as well.  The virus is still out there, and if we become lax in our infection control practices – including decreasing exposure of puppies to the stool of other dogs, as well as vaccination – it’s waiting in the wings for its opportunity to move in. Even with the very best care the infection can still be fatal.

It’s also relevant to note that, as demonstrated by Solomon’s case, just because parvo is very uncommon in adult dogs doesn’t mean it’s impossible for them to get it.  It’s important to always remain diligent.

Parvoviruses are quite species specific, so thankfully people cannot get parvovirus from dogs, but remember that puppies can get diarrhea from pathogens like Salmonella, which can be transmitted to people. There is also a human parvovirus which is the cause of Fifth disease. Just like the dog virus cannot infect people, the human virus cannot infect dogs.

Image source: http://omg.yahoo.com

A new trend in the back-to-nature/all-natural (or whatever the catch-word of the day is) movement is urban chickens. These chickens are raised in small numbers by city slickers (i.e. urban residents) in their yards, and are typically used as a source of fresh eggs. Not surprisingly, this concept has met with some controversy. Some people are strong supporters of the idea, while others have serious objections. Different jurisdictions have begun passing bylaws regarding urban chickens – some have implemented pilot projects and others don’t allow it at all.

Supporters claim:

  • It’s a cheap, sustainable and "all-natural" source of eggs
  • It allows people to "get back to nature"
  • It’s a more humane way to raise chickens
  • Watching chickens roam around the yard is enjoyable

Opponents counter with:

  • Farm animals should be on farms
  • Chickens smell: Very true, especially in large numbers and/or confined spaces.
  • Chickens are loud: Many places that allow urban chickens ban roosters to decrease problems with crack-of-dawn wake-up calls.
  • Chickens carry infectious diseases: Also true, but the same can be said for any animal. The main concerns with chickens specifically are Salmonella and Campylobacter, which are both bacteria that cause diarrhea. They can be passed in the droppings of healthy chickens and can be on eggs. Common sense practices such as keeping the chickens away from areas where people eat (e.g. the backyard picnic table), proper handling of eggs and good general hygiene should reduce the risks greatly, as long as the number of chickens kept is small. Avian influenza (bird flu) is another concern, although currently it’s not a major issue in North America. Anything that increases contact between birds and people can increase the risk of influenza transmission. If bird flu entered a particular region, urban chickens could be a big problem.
  • Chickens attract undesirable and potentially dangerous wildlife like coyotes, skunks and foxes: That’s certainly a possibility, and might be more of a concern in suburban regions that have ongoing issues with things like coyote attacks.
  • Most people don’t have a clue how to raise chickens: That’s why some animal welfare agencies are opposed to urban chickens. Some humane societies also object because they can end up being the recipients of abandoned chickens, with which they are not equipped to deal and which cannot be easily adopted.

Here are some important points to consider if you’re thinking about getting some urban chickens:

  • Is it legal in your town?
  • Do your neighbours like the idea? A few chickens isn’t worth a neighbourhood spat.
  • Do you know how to take care of chickens? If the answer is no (as for most people), are you willing to learn before you get your first chicken?
  • Do you have a easily accessible source of feed? If you have to drive 100 km to get chicken feed, the project is bound to fail.
  • Do you have any high-risk individuals in the house? This would include the very young, very old and people with weakened immune systems, who are more prone to developing disease if exposed to infectious agents.  These individuals should not be exposed to chickens.
  • Are you in for the long term?  Commercial layer hens are generally productive for about 12 months, but some chickens can live for years.
  • If you decide to get rid of the chickens, what will you do? Where will they go? Setting them free or dumping them off in the country is not an ehtical option. Adult hens don’t make good roasting chickens, so even if you get them butchered for meat, you’re probably left with stewing chicken at best.
  • Remember that backyard eggs are not necessarily safer than commercial eggs. Consumption of raw eggs and improper handling of eggs are risk factors for diseases like Salmonella, no matter where they come from. Don’t be fooled by the "all natural means safe" myth.

The burgeoning green movement has scored another victory at Google’s Mountain View headquarters. The facility has fields around it that are cut periodically to control weeds and reduce fire hazards.  Google has recently exchanged lawnmowers for a herd of goats. Someone is now paid to bring in a herd of about 200 goats which spends a week or so grazing the area. This provides fossil-fuel-free grass cutting and a source of food for the goats. It’s also presumably much nicer to look out at a group of grazing animals than a noisy lawnmower.

This is another interesting example of attempts to "return to nature", at least to some degree. Another example is urban chickens, which are a topic of considerable debate in some cities (more on that in a later post). Any time there is the potential for increased contact with livestock, there is some increased risk of transmission of diseases from these animals, although this risk is likely pretty minimal with lawnmower goats. The main concern is shedding of potentially harmful microorganisms like Salmonella in the animals’ manure. Sunlight does a good job killing many of these microorganisms, and the duration and density of grazing would minimize accumulation of manure in the fields. If human contact with the fields is minimal, the risks would be extremely low. It sounds like these fields are not heavily used by people, so it’s less likely that Google employees  will be exposed to anything harmful, compared to what the situation would be if they used the area for having lunch or lounging in the sun while on break. Q-fever is also a potential concern, but that’s mainly a risk around the time of birth (called "kidding" in goats – no joke!), so they just need to make sure they’re not using heavily pregnant goats in their lawnmowing team.

There’s never a no-risk contact with animals (nor is there such a thing as no-risk contact with people), but slight increases in known or theoretical infectious disease risks are not necessarily a bad thing if the benefits outweigh the risks. There are also no blanket answers to many of the questions about infectious disease risks.  For example, while I don’t have any real concerns with the Google goats, I wouldn’t want to see goats grazing in the yard of a daycare or preschool. In a case like this, however, I think it’s a good experiment and it will be interesting to see what happens over time.

ProMed recently reported about an outbreak of canine brucellosis at a "puppy farm" in Ireland. Farm is definitely the appropriate word in this case, since this operation had about 700 breeding females. The picture on the right is not from this farm, but I imagine it’s a similar operation. Beyond the concerns about humane management of dogs under these conditions, such a large operation creates perfect conditions for various infectious diseases.

"The farm’s owner has refused to sign an undertaking not to move the dogs off-site before an official inspection can take place to investigate the extent of the [brucellosis outbreak]."

Lack of cooperation makes any disease investigation much more difficult. It’s not surprising this person doesn’t want to cooperate, given the type of operation he’s running.

"Someone from the farm told the Irish Times that the 2 animal welfare agencies were involved in acts of "intimidation" against the establishment."

I suspect that "intimidation" in this case means the agencies were doing their job, because I can’t see how there wouldn’t be significant welfare problems at a farm of this type and size.

"’We got accurate information on Friday [2 May 2009] that this man was intending moving and selling these dogs and we acted on it,’ according to Jimmy Cahill, chief executive of the DSPCA [Dublin SPCA]. ‘The guards  were very helpful but the owners refused to let us see the dogs or any of the carcasses.’ "

The reference to "carcasses" implies that deaths have occurred. Death from B. canis in dogs is very rare but it is possible. However, a poorly managed operation with hundreds of dogs is bound to have multiple issues that could cause deaths.

Canine brucellosis is caused by the bacterium Brucella canis. This main problem with this bacterium in dogs is reproductive disease, including abortion and infertility (in both males and females). Discospondylitis (inflammation of the discs between vertebrae in the back) can also develop.

Brucella canis is a zoonotic organism. Human infections are rarely reported but it is possible that some go undiagnosed. Brucella canis can be transmitted from dogs to people through contact with body fluids from infected dogs, including urine and vaginal fluids.  The risk of transmission is likely highest when handling animals during breeding or birthing. While the bacterium can be shed in nasal secretions and saliva, levels are low in these fluids and the risks are probably correspondingly low.

One problem with preventing B.canis transmission is that infected dogs do not necessarily show any signs of disease. In people, B. canis infection can cause flu-like disease, loss of appetite, weakness, joint and back pain, vomiting and diarrhea and various other symptoms.

To control the outbreak on this "farm," quarantine and repeated testing of all dogs is needed, and positive animals must be removed from breeding. Given the information provided above, it’s pretty unlikely this will happen voluntarily. I suspect this person would likely either just get rid of these dogs and get more poor-quality breeding animals, or try to continue breeding these dogs and hope people get sick of looking into his operation.

Rhodococcus equi is a very well recognized pathogen in horses – it is a common cause of pneumonia in foals between the ages of 1-6 months, and infection is also sometimes associated with other problems such as diarrhea, swollen joints and abscesses in other parts of the body. The infection can be very difficult to treat because the bacteria are able to live inside white blood cells, which helps protect them from the body’s immune system, and because they often cause abscesses to form, which are difficult for antibiotics to penetrate. Rhodococcus equi infection in foals has been studied extensively, but there’s still a lot we don’t know how the body defends itself against this organism.  These are a few things we do know:

  • Almost all foals are exposed to R. equi as neonates, but most of them never develop signs of infection.
  • Giving newborn foals hyperimmune plasma (plasma with extra antibodies against R. equi) may have some beneficial effects on farms where the infection is a recurrent problem, but this practice is still controversial.
  • Adult horses are essentially immune to the infection.
  • In almost all cases if clinical disease in foals, the R. equi strain involved carries a special gene called vapA.
  • Mortality rates in foals vary considerably from 0% to 30%.
  • So far, efforts to develop a vaccine to help protect foals have been unsuccessful, but research in this area is ongoing.

People can also be infected with R. equi, and as in foals, pyogranulomatous pneumonia (infection of the lungs which results in the formation of many abscesses) is one of the most common conditions caused by this organism. However, there are a few important differences between infection in people and infection in horses:

  • 85% to 90% of people with R. equi infection are immunocompromised, meaning their immune system is weakened or suppressed for some reason, e.g. HIV infection, or immunosuppressive drugs taken by organ transplant or cancer patients.
  • Among people infected with R. equi who have normal immune systems (i.e. immunocompetent), about half of the infections are localized, meaning they only affect one small part of the body. Many of these are associated with wound infections.
  • Only 20% to 25% of the R. equi isolates in people carry the vapA gene.
  • Infection in immunocompetent people can be fatal in approximately 11% of cases, but among HIV-infected patients the mortality rate from R. equi infection can be as high as 50% to 55%.

Rhodococcus equi is actually a soil organism, and this is likely the most common source of the organism for both horses and people. Only approximately 1/3 of humans infected with R. equi report that they have had contact with horses or pigs (pigs can also carry the bacterium). So we don’t know how much of a risk an infected foal is to a person.  However, it is prudent for people, particularly those with weakened immune systems, to take precautions to avoid potential transmission of R. equi from horses.

  • Try to reduce dust levels on the farm. Because R. equi most often lives in the soil, it can get stirred up into the air in dusty areas, which can then lead to inhalation by animals and people. Doing things like planting grass or other vegetation, installing windbreaks in high-traffic areas, or wetting down dusty stalls or paddocks can help reduce dust levels in the air.
  • Keep open wounds and other broken skin covered when working around animals.
  • Always wash your hands after handling a foal (or any horse)
  • If you have a foal that develops signs of R. equi infection, make sure you have your veterinarian examine it as soon as possible so the diagnosis can be determined and the foal can be treated properly as soon as possible. Some foals with R. equi may develop severe pneumonia very quickly, so it’s important that they are examined right away.

Spring appears to have finally sprung in earnest in Southern Ontario (although we may still get one more frost on the weekend, so I hear) and people are getting back out into the garden.  An increasingly  popular trend in recent years, particularly this year now that the Obama’s are doing it too, is vegetable gardening.  Lots of people like the idea of growing their own veggies in their own backyard, or perhaps in a community garden plot for city dwellers who still want to get their hands dirty – it’s economical, good for the environment, and the plants can be grown "organically" without the use of chemicals or pesticides.  However, pesticides and garden bugs aren’t always the only things to worry about having on your fresh veggies.  We received the following comment from a Worms&Germs reader:

"…What if veggies get infected with raccoon stool[?] Can eggs be killed after [the] veggie is grown and ready to eat?"

Great question.  The concern in the case of raccoon stool is the eggs of the roundworm Baylisascaris procyonis, which can be passed in huge numbers by a relatively high percentage of raccoons in many regions.  If swallowed, the eggs release larvae which can migrate through the tissues of the body, rarely causing visceral, ocular or neural larval migrans.

The good news:

  • Raccoons like to defecate in the same areas most of the time, usually on a relatively flat, elevated surface (e.g. woodpile).  These areas become raccoon "latrines", and the soil in the area can become very heavily contaminated with roundworm eggs.  The good part is that most raccoons therefore not defecate in your garden.
  • Vegetables cannot become "infected" by the parasite – the eggs cannot be absorbed or otherwise get inside a vegetable, they can only contaminate the parts of the plant that are directly in contact with soil.

The bad news:

  • Even though raccoons may not poop in your garden, they can still track roundworm eggs into the soil on their fur or paws when they come by to explore your crop, so you should always consider soil outside as potentially contaminated.
  • Baylisascaris eggs are highly resistant to disinfectants and chemicals, so they can’t be killed this way.
  • Raccoon roundworms aren’t the only parasites that may be found in garden soil.  Dogs and cats can carry other roundworms (Toxocara spp.) which are also capable of causing larval migrans if swallowed (although infection with these worms in dogs and cats is not nearly as common as infection with Baylisascaris in raccoons).  Cats in particular, unfortunately, do sometimes like digging in gardens and may sometimes use a garden as a litterbox.
  • Soil, particularly if it’s contaminated by the stool of any animal, can also contain many different kinds of bacteria such as Salmonella.  Even if you can somehow protect your garden plot from animals, purchased garden soil and fertilizers may contain or may have come in contact with animal stool somewhere along the way.

So how do you make your garden veggies safe to eat?

  • Wash wash wash: Because Baylisascaris eggs are so difficult to kill, the best thing to do is physically remove them from all surfaces of your vegetables by washing thoroughly to remove all visible dirt before doing anything else.  If you cut into a vegetable before washing it, the soil on the outside can contaminate the inside.
  • Peel peel: Peeling vegetables ensures that all dirt (including any dirt stuck in tiny crevices on the vegetable’s surface, or dirt you may not be able to see with the naked eye) is removed prior to consumption, but it’s still crucial to wash the veggie first (and your hands) before peeling.
  • Cook: From an infection control perspective, it’s best to cook vegetables before eating them.  This actually won’t do anything to Baylisascaris eggs – these have to be removed by washing and peeling – but it does help kill bacteria that either contaminated the veggies out in the garden or that contaminated the veggies during their preparation in the kitchen.  For those of us who like our nice crunchy vegetables, obviously cooking them won’t do, therefore washing and peeling become that much more important.

And, of course, always wash your hands thoroughly with soap and water after you’ve been working in the garden, even if you wear gloves.

In a lot of urban areas, it’s hard to prevent raccoons and other animals from getting into yards and gardens.  There are things you can do to discourage raccoons from hanging around your house, and if raccoons establish a latrine on your property it must be very carefully cleaned up.  For more information on Baylisacsaris, raccoons and cleaning up raccoon latrines, please see our archives.

A UK man is on a campaign to raise awareness about Toxocara, following an infection that blinded the child of a family friend. Mike Kennedy, chairman of the Grange Residents’ Association, is  raising awareness about the importance of picking up "dog dirt" (i.e. dog stool).

Toxocara canis is an intestinal parasite that can be found in a small percentage (likely 2-14% in Ontario) of healthy dogs, and a larger percentage of puppies. Toxocara cati is the feline equivalent found in a comparable proportion of cats. If a person swallows an infective egg – an egg that was passed in an animal’s stool and allowed to sit around in the environment for a while – infection can occur. The parasite can migrate throughout the person’s body, causing various types of problems. Migration into the eye (ocular larval migrans) can cause blindness. Migration through the brain (neural larval migrans) can cause serious brain injury. These are very rare diseases, but are obviously still a concern because of they can be so severe. The risks are highest in children and people with developmental delays, since they’re more likely to swallow stool, dirt, or something else contaminated with stool.

Mr. Kennedy’s emphasis on educating animal owners to pick up after their pets is the key. We know a small percentage of dogs and cats shed Toxocara in their stool. You never know exactly who is shedding the parasite at any time, so removing the source of parasite eggs, the stool, is critical.  Deworming pets regularly is also important, but it is only one component of parasite control. The frequency and type of deworming needed for dogs and cats varies between regions and animals.  Your veterinarian can design an appropriate deworming program for your pet. Such a program requires a balance between adequate deworming to reduce the risk of parasites in pets (and the associated risk for human infection) and using dewormers prudently to reduce the risk of parasites developing resistance to these drugs.

Photo credit: Michael Lazarev (Clyde, the bulldog puppy)