Updated: Speaking of Baylisascaris...
This post has been updated with new information as of October 2, 2008.
An article was published on Sunday in a local Guelph newspaper about a 14-month-old child who has been battling infection with Baylisascaris larvae in a Hamilton (Ontario) hospital for the last two weeks. This comes on the heals of a very recent Worms & Germs post about Baylisascaris procyonis - the raccoon roundworm.
The disease caused by migration of Baylisascaris larvae through the body - visceral larval migrans - is uncommonly diagnosed in North America, although it may be more common than we think because it is difficult to diagnose with certainty, and the signs in mild cases may be very non-specific. The most severe form of the disease is called neural larval migrans, which occurs when the larvae migrate through the brain or spinal cord, as in this most recent case.
The parents of the toddler in the article, a toddler who is still blind and cannot sit up on his own as a result of his infection, have a message for parents: keep raccoons out of your yard and away from your house. The disease may be rare, but the effects can be devastating, and the risk can be significantly reduced by a few simple steps:
- Keep garbage in tightly-sealed containers.
- Clear brush and seal openings in buildings where raccoons may nest or form latrines.
- If you find raccoon stool or what appears to be a raccoon latrine on your property, clean it up very carefully. Follow this link for more information on identifying and cleaning up raccoon latrines.
- Always wash your hands well after you've been working outside in soil, dirt or water which could be contaminated with raccoon feces.
For more information, see the last Worms & Germs post about Baylisascaris.
World Rabies Day
This Sunday, September 28th, is World Rabies Day. The goal of this day its to raise awareness about rabies, a disease that still kills thousands of people and animals in many parts of the world every year. While human rabies is thankfully rare in most developed countries, it is a major health concern in many other regions. Even in countries such as Canada and the US, where human cases are uncommon, diligent vigilance is required, because rabies continues to be present in wildlife, and therefore people and pets can still be exposed to this deadly disease.
A key part of rabies prevention, which is also a major focus of rabies education programs, is the need for vaccination of pets, even strictly indoor pets. Rabies vaccination is a cheap and effective way of protecting your pet, yourself and your family from this disease. It's also required by law in many areas. The implications of rabies exposure of pets that are not properly vaccinated can be severe, possibly including euthanasia or very long quarantine, even if they are not infected.
Many groups are holding events to increase awareness about rabies, such as the People and Pets Walk to End Rabies which is being held by the University of Guelph. Information from an advertisement for this event states "Although rabies does not seem like an issue at home, it is a major health problem for both humans and animals in developing countries, claiming the life of one person every ten minutes. If we work together, we can make a difference. Please show your support and join us at the walk to help make rabies history!" That statement should make it clear why we talk about rabies so much. One human death every 10 minutes is a startling figure for a disease which we should be able to control.
More information about rabies is available on the Worms & Germs Resources page.
Healthmap
If you are looking for an interesting website to play around with, you should try HealthMap. This is a website created by the Harvard-MIT Division of Health Sciences and Technology that maps infectious disease reports from various sources. You can search by region and see what disease problems have been reported recently, or select specific diseases and find out where they've been reported. Some examples are shown below. The top image shows all disease reports worldwide (in the last 30 days), while the bottom image shows reports of Salmonella in North America during the same time period. The site relies on reports of diseases (many cases of various diseases occur but are never reported), so it focuses mainly on outbreaks or high profile cases , but it is still quite interesting.
Above: All reported disease outbreaks/cases worldwide in the last 30 days.
Below: Reported outbreaks/cases of Salmonella in North America in the last 30 days.
See the HealthMap site for more details.
Salmonella outbreak linked to turtles
Yet another reminder of the risks associated with handling turtles (and other reptiles) comes to us from a report published earlier this year regarding an outbreak of salmonellosis in people tied to contact with turtles. In this case, more than 100 people in 33 US states were affected. The report sparked additional public education efforts in Los Angeles county, CA, where eight of the cases occurred.
The report comes as no surprise - turtles are actually relatively commonly implicated in cases of salmonellosis in people (although still not nearly as commonly as foodborne transmission). It's particularly a concern in children, because kids may have close contact with pet turtles and may be more susceptible to serious infection.
In response to the cases in Los Angeles, the county Department of Public Health emphasized that parents must be wary of buying turtles for their children. Even though the sale of small turtles (less than 4 inches long) was banned in the US over 30 years ago, unfortunately these animals are still widely available in many pet stores, flea markets, and from other sources. Los Angeles Public Health personnel reported that children were getting sick because they were kissing their pet turtles - something that is very risky and should never be done by anyone, especially children. If people have pet turtles, they must be very diligent to practice good hygiene to reduce the risk of transmission of Salmonella.
More information about the risks associated with pet turtles, and measures that should be taken by people who own turtles, is available on the Worms & Germs Resources page.
Treatment of MRSA and MRSP: more than meets the eye
Methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant S. pseudintermedius (MRSP) are important causes of infection in pets, and are resistant to many different antibiotics. It's therefore very important that these bacteria are cultured and tested in a lab to determine what antibiotics may be effective. Even then, choosing an effective medication can be difficult due to the limited number of potentially effective drugs.
Treatment selection is further complicated by problems that can occur when methicillin-resistant staphylococci are tested against certain drugs in the lab - problems that are not readily apparent unless extra testing is done. One "problem" drug is the antibiotic clindamycin. Clindamycin can be an effective treatment for MRSA or MRSP infections, but some MRSA strains may be resistant to it despite appearing to be susceptible based on normal laboratory testing. This is because the bacteria can have "inducible resistance". Inducible resistance can be detected by a special test called a D-test (see picture), but this test is not widely performed in veterinary laboratories.
In recent study presented by Dr. Meredith Faires (University of Guelph) at a conference last week, 55% of MRSA from dogs and cats that were reported to be resistant to erythromycin and susceptible to clindamycin were actually inducibly resistant to clindamycin. But no MRSA that were susceptible to erythromycin were inducibly resistant to clindamycin. In contrast, inducible resistance to clindamycin was not identified in any MRSP. Therefore, in the absence of specific testing for inducible resistance (i.e. a D-test), it is wise to consider all erythromycin resistant MRSA to be clindamycin resistant as well, regardless of the results of traditional antibiotic susceptibilty testing.
Pet food and Salmonella
The recent pet food recall for Salmonella has generated a lot of attention and, encouragingly, more resources containing information about reducing the risk of Salmonella from handling pet foods. One is a video from Drs. Doug Powell and Randy Phebus of Kansas State University, that can be seen by clicking on the image below. Another is an information sheet produced by the FDA. Many of the recommendations, as well as those we've made in previous posts, are basic and common sense, but are often overlooked because handling pet food is not perceived as a risk for infectious disease. While the overall risks of infection from handling commercial pet food are low, these easy, common sense measures should still be used.
Updated: Raccoon Roundworms - Baylisascaris procyonis
This post has been updated with new information as of October 2, 2008.
Raccoons, just like dogs and cats, can have roundworms in their intestine. Dogs are typically infected by the species Toxocara canis, and cats are infected by Toxocara cati. Raccoons are infected by a type of roundworm from a different genus, called Baylisascaris procyonis. There is one thing that all three of the parasites have in common – the larvae of these worms can infect humans, causing a condition called visceral larval migrans.
Dogs and cats are usually dewormed as puppies and kittens, and often as adults as well, which dramatically decreases the number of pets that are infected with roundworms. Raccoons are not so lucky – in the northern and northeastern parts of North America, over 70% of raccoons may be infected with Baylisascaris. In Ontario, it has been estimated that only about 20-30% of raccoons are infected, but usually with high numbers of worms. In either case, younger raccoons are even more likely to be infected. Infected animals may shed millions of parasite eggs in their stool, and the eggs can survive in the soil for months or even years.
After a few weeks, the eggs in the raccoon stool become infective. If a person swallows the eggs, they hatch in the small intestine and release larvae. These larvae can then burrow through the wall of the intestine and migrate through tissues all over the body, causing tissue damage and inflammation. The signs of illness are often not very specific, and may include things like fever, fatigue and nausea. If the larvae migrate through the brain or spinal cord, a person may develop neurological signs like loss of coordination and muscle control. This is called neural larval migrans, which is the most serious type of disease caused by these larvae. If the larvae migrate through the eye, they can cause blindness. This condition is known as ocular larval migrans.
There have been less than 25 cases of confirmed visceral larval migrans due to Baylisascaris in the USA as of 2003, but the condition is very hard to diagnose with certainty, and it is possible that many cases are mistaken for other illnesses. The disease is also very difficult to treat, and neurological damage from neural larval migrans is usually permanent, so the best thing to do is prevent infection in the first place. Here are some tips on avoiding Baylisascaris:
- Avoid contact with raccoons. Many people think raccoons are cute, but they are wild animals. Raccoons are also a risk for transmission of rabies if a person is scratched or bitten. NEVER keep a raccoon as a pet.
- Discourage raccoons from hanging around your house. Clear brush and seal access to basements and attics where raccoons may try to nest or form latrines. Keep garbage in tightly-closed garbage cans. Eliminate outdoor water sources.
- Always wash your hands well with soap and water after working with soil (e.g. in the garden).
- Clean up raccoon latrines. This must be done very carefully - avoid getting any raccoon stool on your hands or clothes. The stool should be burned, buried or sent to a landfill. Clean the area where the stool was found with boiling water. Wash your hands very carefully when you’re done. Follow this link for more detailed information on how to identify and clean up raccoon latrines.
Baylisascaris procyonis less commonly infects animal species other than raccoons, including skunks, and it has even been found in dogs. It's important to have your dog's stool examined for parasite eggs on a regular basis (typically once or twice a year) and to follow your veterinarian's recommendations for deworming your dog.
More information about Baylisascaris is available on the CDC’s Baylisascaris Infection website.
Pet food recall: Salmonella
Mars Petcare has recalled certain pet foods produced in a plant in Everson, Pennsylvania and sold in several US states. This is being done because two lots of pet food were found to be contaminated with Salmonella Schwarzengrund. This is the same Salmonella strain that was identified during a pet-food associated outbreak of salmonellosis in people in 2006-2007. Production of pet food at this facility was stopped in July because of a potential link between pet food produced there and infections in two people. More information about this recall is available from the FDA.
While commercial pet foods undergo rigourous quality control and are much less likely to contain potentially harmful bacteria such as Salmonella than, for example, raw meat diets, it is important to remember that situations such as this can happen. So it's still a good idea to wash your hands after handling pet food, of any kind.
Raw meat feeding revisted, part II: So you want to feed raw meat to your pet...
In a recent post, I discussed a study about the health effects of feeding raw meat diets to pets. Because of the significantly higher rates of shedding of certain potentially harmful bacteria by dogs that are fed raw meat, I think raw meat diets are a bad choice - especially in households with young children, elderly individuals or people with compromised immune systems. However, if you are going to feed raw meat to your pet, you should take some basic precautions.
- Only use meat that is suitable for human consumption. Don't buy 'adulterated' meat or meat labeled unfit for human consumption.
- Keep raw meat frozen until you need it. Only thaw out the portion that is need for the next feeding, and thaw the meat in a sealed container on the bottom shelf of a refrigerator.
- Handle raw meat with care. Do not allow it to contaminate kitchen surfaces or items that may come in contact with other food. Clean and disinfect any items that come into contact with raw meat.
- Wash your hands thoroughly after handing raw meat or anything that has touched raw meat (e.g. your dog's food bowl).
- If your pet does not finish all the meat fed right away, discard any uneaten raw meat promptly. Do not allow raw meat to sit in a bowl at room temperature. Some dangerous bacteria can multiply rapidly under these conditions.
- Regularly clean and disinfect your pet's food bowl, but bear in mind that a recent study showed that it is very hard to eliminate Salmonella from raw meat in food bowls.
- Make sure your veterinarian knows that you feed raw meat. This is particularly important if your dog develops vomiting or diarrhea.
- It is very important to make sure that your pet's diet is well balanced, which can sometimes be difficult to do when feeding non-commercial or raw diets. Read about raw meat feeding, and try to find good sources of information (which is not always easy) to reduce the risk of problems caused by feeding an unbalanced diet.
- Never feed raw meat to sick dogs, puppies or pregnant dogs.
Raw meat feeding revisited: what are the risks and benefits of raw diets for dogs?
Feeding raw meat diets to dogs is a very controversial issue. Some proponents passionately advocate these diets (e.g. the BARF diet) based on vague and unproven recommendations. Opponents cite various studies showing that pets fed raw meat (not surprisingly) have high carriage rates of potentially harmful bacteria such as Salmonella, and reports of diarrhea or nutritional imbalances in these animals. However, there have been only a few good studies looking at the true health benefits and risks of feeding these diets to dogs.
A recent study in the journal Zoonoses and Public Health described the risks of therapy dogs shedding Salmonella and other potentially harmful bacteria. The authors tested 200 dogs over a 1 year period, 20% of which were fed raw meat as part of their normal diet. Dogs fed raw meat were 23 times more likely to shed Salmonella compared to other dogs. They were also 17 times as likely to be shedding extended spectrum beta-lactamase (ESBL) Escherichia coli (a highly drug-resistant form of E. coli).
The study concluded that, because of the risk of Salmonella shedding and the high-risk nature of the patients and other people that therapy dogs interact with, dogs that are involved with hospital/patient visitation programs should not be fed raw meat.
What does this tell us about feeding raw meat to pets?
Although this study doesn't answer all of the questions about the risks of raw meat diets, it reinforces the fact that pets fed raw meat have significantly higher rates of shedding of potentially harmful bacterial such as Salmonella and antibiotic-resistant E. coli. Eating pig ear treats has also been associated with Salmonella shedding. However, there was no association between a dog being fed raw meat and the animal itself developing diarrhea. In fact, raw-fed dogs had a lower incidence of extra-intestinal infections (combination of eye, ear, skin and urinary tract infections).
In general, raw meat diets should be avoided. While adverse health effects were not reported in this study, disease (including deaths) from Salmonella has been reported in dogs in other studies. While the overall risk may be low, feeding raw meat is an avoidable risk. However, it would be inappropriate to completely ignore the finding that raw-fed dogs had lower rates of certain infections. It is possible that there can be health benefits from feeding raw meat in certain dogs, but the potential benefits must be weighed against the potential risks to the animals and people with which the has contact. Raw meat diets should never be fed to pets that have contact with immunocompromised people (in the household or as part of visitation program), infants or the elderly.
If you are going to feed raw meat to your pet, make sure you take precautions to reduce the risk of infecting yourself or someone else. We'll post more on that aspect soon.
Brucellosis in dogs
Brucellosis is an infection caused by bacteria of the genus Brucella. The most common species of Brucella in companion animals is Brucella canis, which typically causes infection in dogs. This bacterium is very rare in Ontario - in a survey of 2000 dogs, only 0.3% had evidence of exposure to B. canis. So it was unusual that a case of canine brucellosis was recently diagnosed in the province, until it was discovered that the dog originally came from a rescue shelter in the southern USA - an area where exposure to the bacterium is much more common (approximately 8% of dogs).
Brucellosis in dogs typically causes reproductive problems such as infertility and an enlarged scrotum in males, and late-term miscarriage in bitches (breeding females), with few or no other signs of clinical illness. But in some cases the bacteria have been found to infect tissues other than the reproductive tract, including intervertebral discs (leading to back problems), the eyes, the kidneys, or the tissues around the brain and spinal cord (i.e. the meninges). The bacteria, and antibodies to the bacteria, can be very difficult to detect in the early stages of infection. The infection is usually diagnosed by a blood test, but it may take 8-12 weeks before test will yield a positive result. There are also problems with high numbers of false-positive test results due to cross-reaction with other species of Brucella. Any positive test result should therefore be confirmed by a second, different laboratory test.
Human infection with any species of Brucella is now uncommon. When illness does occur, the signs are often non-specific (e.g. fever, headache, myalgia), but more severe infections have been reported. Transmission of B. canis from an infected dog to a person is possible. The bacterium is transmitted by contact of a mucous membrane (e.g. eyes, nose, mouth) with blood, urine, milk, semen, or vaginal discharge from an infected animal. The highest-risk materials (i.e. most likely to contain a high number of the bacteria) are placental tissues and fluids that are passed during whelping (delivering puppies). Treatment for infection is available, but the course is often long and recurrence of infection can occur.
Although brucellosis is very rare in dogs in Ontario (and Canada in general), here are a few things you can do to help avoid B. canis:
- Always wash your hands right away if you accidentally come in contact with blood, urine, milk, semen or vaginal discharge from any dog.
- Prevent contact between your dog and urine, milk, semen or vaginal discharge from other dogs, especially if you travel with your dog to an area where the prevalence of B. canis is relatively high (such as the southern USA).
- Dogs used for breeding should be tested for B. canis. Many breeders will require dogs to be tested before allowing their animal(s) to be used, because the infection can be transmitted through breeding and can have such detrimental effects on fertility.
- Newborn pups should be handled as little as possible, but if you must handling them wear disposable gloves and wash your hands as soon as you take your gloves off. Exercise the same precautions when cleaning up the area where a bitch has whelped.
More information about brucellosis can be found on the CDC's Brucellosis website.
Dogs in restaurants
I just passed through Paris en route to a conference in Belgium, and was reminded of a topic that comes up occasionally: pets in restaurants. While "dining with dogs" is a common site in many areas of Europe, it is rare in North America. I periodically get asked about the risks associated with having pets (usually dogs) in restaurants, and unfortunately there isn't a clear answer.
Overall, the infectious disease risks associated with having "Rover" in a restaurant should be very low. Dogs don’t emit some intangible "aura of infection," so just having them in the vicinity while people are eating is not a problem. Microorganisms have to make it from the dog’s body to a person (and usually into their mouth) to cause disease. We don’t have many concerns about airborne spread of diseases from dogs to people. In reality, simply having a dog in a restaurant should be less risk than having people in the restaurant (since people can transmit some infections to each other over short distances by coughing and sneezing). But for this to be true, people still have to handle their dogs properly, meaning people who touch a dog should wash their hands before eating, and restaurant staff should not touch any dogs in the restaurant at all.
Does this mean we should be allowing dogs in all restaurants? Not necessarily. The biggest weakness of even the most logical infection control measures is lack of compliance - people who break the "rules". For example, would people actually minimize contact with the dog and wash their hands? Would food servers really stay away from them? Would all dogs be adequately trained never to bite, scratch, jump up or behave inappropriately in a busy restaurant environment? Furthermore, people with allergies to pets and fear of dogs need to be considered.
In the end, most dogs probably would not cause a problem in most restaurants around most people… but "most" is not "all". Clearly, this is not a straightforward issue, and there are logical arguments on both sides.
Echinococcus and hydatid disease - not your average tapeworm
A previous Worms & Germs post talked about the (very low) zoonotic risk of the tapeworm most commonly found in dogs and cats, Dipylidium caninum. Dogs can also carry other species of tapeworm, such as Taenia pisiformis, which cannot be naturally transmitted to people. But dogs can also carry tapeworms from the genus Echinococcus, the most common of which is E. granulosus. Echinococcus multilocularis is much less common in North America, and can also be carried by cats.
In Canada, dogs tend to be exposed to E. granulosus when they eat certain animals, particularly wild herbivores like moose and caribou. In other parts of the world, eating sheep organs is the most common way dogs are exposed. The immature form of the worm is found in the animal’s lungs, liver and other tissues. After being eaten by the dog, the worm matures in the intestine, and tapeworm eggs can soon be found in the dog’s stool. Tapeworm segments, as seen with Dipylidium infection, are usually not seen in the stool with Echinococcus. Under a microscope, it is possible to tell Dipylidium eggs from Echinococcus eggs, but it is not possible to tell Echinococcus eggs from Taenia eggs.
If a moose, caribou, sheep or another suitable “intermediate host” swallows the eggs from the dog stool, the parasite migrates through the animal’s body and forms cysts in various tissues which contain the immature form of the worm. If the animal dies or is killed, and a dog (or a wolf or coyote or related species) eats the cysts, the cycle begins again.
Unfortunately, humans can also be an “intermediate host” for these tapeworms. If a person ingests Echinococcus eggs from dog stool, the parasite can form cysts (called hydatid cysts) in many tissues and organs, including the liver, lungs, brain and heart. If the cysts are small and there are only a few, they may not cause any problems for years, and the person may never know they’re there. But as the cysts grow, they can get very large and start to interfere with the function of organs, or their size alone may be a problem, depending on where they are located. Treatment can be difficult – drugs are frequently not effective, and large problematic cysts may need to be surgically removed, if the surgery can be done safely. If a cyst bursts it can cause anaphylactic shock, which is very dangerous.
In Canada, Echinococcus infection and hydatid disease are most common in the western provinces. Nonetheless, everyone can take a few simple steps to help prevent exposure of people to Echinococcus:
- Always wash your hands after handling dog stool, even if you use a plastic bag or a scoop to pick it up.
- Your dog should have a fecal examination for intestinal parasites at least once per year, or more frequently if your dog is at increased risk of exposure to Echinococcus. If tapeworm eggs are identified, your veterinarian can prescribe medication to treat the infection.
- Monthly heartworm preventatives that are effective against other intestinal worms are not effective against tapeworms!
- Do not let your dog eat uncooked meat, especially the organs of sheep or wild game such as moose and caribou.
More information on Echinococcus and hydatid disease is available on the CDC’s Echinococcosis webpage.
Feline Immunodeficiency Virus - HIV/AIDS for Cats
Everyone is familiar with the human immunodeficiency virus (HIV) - the retrovirus that causes acquired immunodeficiency syndrome (AIDS) in people. Although HIV can only infect humans and some primates, cats can be infected by a very similar virus from the same genus (Lentivirus) with a similar name – feline immunodeficiency virus (FIV). The FIV virus is transmitted from cat to cat by contact with blood, usually through a cat bite. In Canada and the USA, up to 3% of healthy cats may be infected with FIV.
As with HIV in people, FIV attacks a cat’s immune system, which can leave the animal susceptible to many different infections that a healthy cat could normally fight off. Some of these infections, like toxoplasmosis, are similar to those that occur in AIDS patients. (More information on toxoplasmosis and Toxoplasma is available on the Worms & Germs Resources page). Depending on a number of factors, an FIV-positive cat may remain healthy for years, but once the animal begins to show signs of a weakened immune system, it will often develop chronic or recurrent health problems. The infection is life-long – there is no “cure” for FIV.
Some key points to remember:
- Cats cannot get HIV. People cannot get FIV. They are related but different viruses.
- Keeping your cat indoors will prevent fighting with other cats and decrease the risk of your cat contracting FIV.
- There is a vaccine available for FIV, but it remains uncertain if the vaccine can protect cats from all strains of the virus. The vaccine also interferes with tests for FIV infection. Therefore, preventing exposure to the virus is still the best way to prevent FIV infection.
- If your cat already has FIV, it is important to keep it indoors to decrease exposure to pathogens that could make your cat sick, and to prevent your cat from spreading the virus to other cats.
More information about FIV can be found on the Cornell Feline Health Center website.
