Echinococcus granulosus

A previous Worms & Germs post described what is known as the sylvatic cycle of Echinococcus granulosus, which is thought to be a common route of infection for dogs in Canada.  In the sylvatic cycle, dogs become infected with Echinococcus by eating the internal organs (usually lungs and liver) of wild game such as moose and caribou.  The dogs then pass tapeworm eggs in their stool, which can cause infection in other wild animals (thus continuing the cycle) or in people who accidentally swallow the eggs.  In humans, Echinococcus forms slow-growing cysts (called hydatid cysts) in different organs of the body which can be very difficult to remove or treat in some cases.

Echinococcus also has a pastoral or domestic cycle.  In this cycle, dogs acquire the parasite by eating the internal organs of infected sheep, and sometimes other livestock such as cattle and swine.  This cycle is potentially very important in areas where there is a lot of sheep farming.  In some areas of Latin America, 20-95% of sheep at slaughter may have evidence of hydatid cysts in their organs.

It is much more difficult to tell when a dog is infected with Echinococcus compared to other tapeworms such as Taenia or Dipylidium.  An adult Echinococcus is tiny - only a few milimetres long (see picture right), very unlike the long, stringy white tapeworms that most people picture.  Dogs can carry hundreds, even thousands of these tiny tapeworms without showing any signs of illness at all.  The eggs can sometimes be difficult to detect on fecal examinations, and when they are seen they cannot be differentiated from Taenia eggs.  Nonetheless, this is still the best way to detect infection, so fecal examinations should be performed regularly.

Remember:

• In areas where Echinococcus is known to exist, it's important to have your veterinarian perform fecal examinations on your dog's stool more frequently than the usual once-a-year, because of the serious zoonotic potential of this parasite.
• Always wash your hands well after handling dog stools.
• Do not let your dog eat uncooked meat, or the organs from farm animals or wild game.

For more information on Echinococcus, see Worms & Germs post entitled Echinococcus and hydatid disease - not your average tapeworm.  There is also information available on the Michigan State Department of Natural Resources site.

Lower photo credit: Ontario Veterinary College

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.

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.

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.

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.

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.

• Only eat/drink pasteurized dairy products.
• The main risk from cats and dogs (especially cats) is when they give birth. If you have a cat or dog that has kittens/puppies, wear gloves if you have to touch the babies or any placentae. Afterwards, cleaning the area very thoroughly to physically remove any tissue or fluid residue is very important, because most disinfectants cannot kill C. burnetii. Always wash your hands thoroughly after handing newborn kittens or puppies.
  
• On dry, windy days, avoid farms or areas where sheep or goats are kept.
• Avoid sheep and goat farms during the lambing/kidding season.

• Cryptosporidium hominis primarily infects humans. Clearly it can make people sick, whether their immune systems are weakened or not.
• Cryptosporidium parvum primarily infects calves, and clearly makes people (and calves) sick. However, because it is relatively common in people as well, in many cases it is hard to say if a person with C. parvum was infected by contact with calf stool or human sewage.
• Both the dog-associated C. canis and cat-associated C. felis have been found in people, and C. felis can cause diarrhea even in immunocompetent individuals. Infection with these species in humans is very uncommon compared to C. hominis and C. parvum
• The largest outbreak of cryptosporidiosis ever reported in North America occurred in Milwaukee in 1993, when an estimated 1.6 million people were exposed to the parasite and over 400 000 people became sick as a result of the infection.
• In most studies, contact with pets is either not associated with the risk of cryptosporidiosis or may even have a slight protective effect. One study showed no significant association between pet ownership and cryptosporidiosis in HIV patients.

• Keep your hamster in a clean enclosure with good ventilation and enough space for your hamster to have separate areas to eat, sleep, exercise and poop/pee.
• Prevent contact with wild rodents. This means keeping your hamster in its cage and not letting it roam around the house. Also ensure that your hamster cannot escape from its cage and wild rodents cannot get into the cage.
• Most importantly, always wash your hands after handling your hamster.

1. The suggested size of the problem;
   
2. The often serious nature of the disease;
3. The zoonotic potential of the infection (a small number of human infections acquired from dogs have been recognized in Ontario and Québec in recent years);
4. The ongoing widespread presence and sometimes large numbers of raccoons in suburban and urban Ontario;
5. The diagnosis of canine leptospirosis throughout the province;
6. The diagnosis of the disease in dogs of all types, not just the “male hunting dog” which is sometimes conventionally regarded as “high risk”.

1. The sporadic nature of the infection, including the lack of exposure of some dogs to raccoons and other wildlife sources;
2. The number of vaccine reactions associated with leptospiral vaccines (this is not a significant problem with at least one of the vaccines);
3. The considerable confusion caused by the (almost certainly totally unfounded) suspicion that serovar autumnalis causes canine leptospirosis, but is not in the new vaccines;
4. The lack of inclusion of serovar bratislava in the vaccine (although this serovar seems to cause only mild disease in dogs);
5. The annual cost of revaccination.

• Use common sense – know how to handle a cat properly so that it is not frightened or uncomfortable. If a cat growls at you or tries to get away, let it go!
• Don’t let cats play with your hands, feet or hair. Use a nice cat toy instead.
• Don’t approach strange cats, especially strays. If you are bitten by a cat that may not have been vaccinated for rabies, it is very important to report the incident to you local public health department and your doctor, as you may need to receive rabies post-exposure prophylaxis (PEP).

Tularemia is a disease caused by the bacterium Francisella tularensis.  It causes different signs of illness depending on how the bacteria enter the body.  If the bacteria are inhaled, it tends to cause pneumonia (pneumonic tularemia).  If the bacteria get in through a break in the skin, infection may cause the local lymph nodes (glands) to become very swollen, and in some cases the skin itself may become infected resulting in the formation of large sores (ulcers).  Infection can also cause sores in the mouth and diarrhea.  The earliest, most common signs are things like fever, headache, chills, sore muscles, and sore throat which often come on very abruptly.  The infection can be treated with antibiotics, but it is important to see a doctor and start treatment as soon as possible.

Tularemia is also sometimes called "rabbit fever," because the bacteria are often carried by animals such as rabbits and hares.  Rodents (including beavers, rats, mice, squirrels etc.) can also carry F. tularensis, and occasionally so can cats and dogs.  Some biting insects like deerflies and certain species of ticks can carry the bacteria and transmit it when they bite.  Francisella tularensis can also survive in water and soil for a long time.  People can become infected by being bitten by an infected insect, handling an infected animal (dead or alive), or coming into contact with feces from an infected animal.  Occasionally a person may inhale the bacteria if it is in the air, as may happen with disturbed, dusty, contaminated soil.

More information on tularemia can be found on the CDC's tularemia website.

Things you can do to avoid tularemia:
Avoid touching or handling wildlife (dead or alive), especially rabbits and rodents.
Don't let your pet touch or eat dead animals.
Always wash your hands if you have been working outside in the dirt/soil.
Wear insect repellent containing DEET (visit the Health Canada website for more safety tips) 
Make sure you only wash food with and drink water that has been properly treated.

One of the reasons tularemia is such a big deal is it is very infectious - as few a ten bacteria can be enough to make even a healthy person sick!  But it is still quite uncommon in North America - about 100-200 cases are reported in people in the USA every year.  Between 2002-2004 there were 34 cases reported in Canada, most of which occurred in Quebec and in adults.  However, infection can be fatal in a very small number of cases, especially if proper treatment is not given as soon as possible.

• Clean your cat’s litter box every day. The oocysts usually take about 24 hours to become infective once they’ve been passed in your cat’s stool, so daily cleaning helps remove them before they reach this stage.
• Always wash your hands with soap and water after cleaning your cat’s litter box, after working in the garden or in any soil, and after handling raw meat.
• Cook all meat, especially pork, lamb, mutton and wild game, to an internal temperature of 67ºC/153ºF or higher.
• Keep sandboxes covered so outdoor cats don’t contaminate them with stool.
• Keep your cat indoors. Outdoor cats are more likely to be exposed to Toxoplasma and shed oocysts in their stool.
  

• Always wash your hands with soap and water (or use an alcohol-based hand sanitizer) after handling a horse, and before handling another horse.
  • This is especially important if you have touched a horse’s nose, or any cuts or wounds that the horse may have.
  • Don’t go down the row of stalls in the barn and pet every horse on the nose! They love the attention, but this is a great way to spread MRSA if it’s there!
• New horses coming into the barn, or animals coming back from a hospital, should be kept separate from all the other animals and only dealt with after all the other horses, for 3-4 weeks.
  • This is an important measure for controlling many infectious diseases, not just MRSA.
• If your horse has a cut that looks infected, cover it with a bandage of some kind and contact your veterinarian. Your veterinarian can culture the wound to determine if it is an MRSA infection.

• A cat that goes outside, especially one that hunts, is more likely to pick up bacteria like Salmonella, or parasites like Toxoplasma and intestinal worms, which can potentially be transmitted to people, whether or not the cat gets sick. Outdoor cats are also more likely to come home with parasites like fleas which, in addition to being a major nuisance to you and your pet, can also transmit tapeworms and may contribute to the transmission of cat scratch disease (bartonellosis).
• Cats that live exclusively indoors are also not at risk of contracting two very important viruses, namely feline immunodeficiency virus (FIV, which is the cat equivalent of the human HIV/AIDS virus) and feline leukemia virus (FeLV, which is sometimes also called Fe-Leuk). These viruses are transmitted by direct cat-to-cat contact, particularly during cat fights. They cannot be transmitted to people, but they can make your cat very sick and prone to other infections, some of which may be zoonotic.
• It’s also easier to keep track of your cat’s health if it doesn’t go outside. Changes in your cat’s drinking and litter box habits, which can be important indicators of various health problems, can be detected much faster if your cat isn’t finding alternate sources of water or places to do its “business” outside.
• And there are still other benefits to keeping your cat indoors, including not having to worry about your kitty being hit by a car, not having to treat fight wounds and cat bite abscesses, and not having your feline friend bringing little “presents” into the house, like dead (or not so dead) rodents and birds.