I’ve recently had many clients asking questions about heartworm disease, so I wanted to clarify a few facts and debunk some myths about the disease.  Heartworm disease is caused by a parasite, Dirofilaria immitis, which is transmitted by mosquitoes.  After a mosquito bites an infected dog, the mosquito becomes infected with the micofilaria (or larval stage) of the parasite. The parasite then undergoes a maturation in the mosquito, and the larvae of the worm are transmitted when the mosquito bites another dog.  The larvae migrate through the dog’s body to the right side of the heart and pulmonary arteries, where each worm can grow to the size of a spaghetti strand. Yes, these are real worms in the heart.

Life Cycle of Heartworm

Historically, heartworm disease was not seen in Colorado or was very rare, due to the fact that we have a dry climate, cool temperatures, and a short mosquito season at higher altitudes.  I don’t know if climate change has been partially responsible for the emergence of heartworm disease in Colorado, but I do know that the increased travel of dogs from other areas of the country, especially the southeastern U.S., has contributed to its presence here.  The relocation of dogs after Hurricane Katrina is thought to have played a large part, with approximately 85% of dogs from the hurricane area being infected with heartworms.

In the past, most dogs I saw that were infected with this disease had a history of travel somewhere outside of Colorado, but unfortunately now I am seeing the disease in dogs that have never left Colorado, and in one case, a dog that has never left Boulder County.

The following is a map showing the incidence of heartworm disease across the U.S. Please note it is a map from 2007, but clearly shows heartworm disease in Colorado. I suspect that the map is much darker four years later.

Incidence of Heartworm Disease

Heartworm disease can be diagnosed with a simple and inexpensive blood test.  This blood test should be done yearly unless dogs have been on heartworm preventative year round.  The blood test is positive if a protein found on the adult female worm is present.  It takes six months for worms to mature in to an adult once a dog is infected, so it is possible to have a negative test even if the dog has been infected. For this reason, the American Heartworm Society recommends yearly testing.

The preventative medication consists of a chewable treat that is given once monthly during mosquito season. In Colorado, I recommend dogs be given the preventative May through October.  If dogs travel outside of Colorado, especially to the southeastern United States or California, where mosquitos are present all year, they should be given preventative year round.

Fortunately heartworm disease can be inexpensively and safely prevented. For dogs infected with heartworms, the treatment is toxic, painful, and expensive.  It involves a series of injections of an arsenic-based drug, followed by 6-8 weeks of kennel rest.

I urge you to have your dog tested for heartworms and to consider starting heartworm preventative, even if you haven’t in the past. For more information, please visit the following website  http://www.heartwormsociety.org/

copyright 2011 Lisa Cass DVM

Re: Equine Herpesvirus Outbreak in Colorado

LAKEWOOD, Colo. – The Colorado Department of Agriculture continues to investigate the spread of Equine Herpesvirus (EHV-1) in the state.

As of 5/23/2011, 12pm:
• 9 confirmed cases of horses with EHV-1
• Two horses, which tested positive for EHV-1, were euthanized after showing severe neurological signs associated with the disease.
• 22 suspect cases. Suspect cases are those horses that are believed to have been exposed to EHV-1 but confirmatory tests are still pending.
• 12 quarantine and hold orders have been issued in 8 counties (Bent, Boulder, Garfield, Gunnison, Larimer, Mesa, Morgan, & Weld)

BACKGROUND
Colorado State Fair Horse Shows Cancelled
Colorado State Fair organizers have voluntarily cancelled th ree equine events following the spread of EHV-1.
• Zamora Roping originally scheduled for May 20-22, 2011. Reschedule date pending.
• Mounted Shooting Regional originally scheduled May 27-30, 2011. Rescheduled for October 7-10, 2011
• Sagebrush Slide Cow Horse Show originally scheduled June 1-5, 2011. Rescheduled for August 10-14, 2011

“We decided to reschedule these events to limit the number of horses traveling to and from our fairgrounds,” said State Fair General Manager Chris Wiseman. “Our horse shows are important to the Fair and to Colorado as a whole and we want to be proactive in protecting our horse community.”

Facts about EHV-1 Vaccines
The common vaccines available for EHV-1 immunization do not protect against the neurological form of EHV-1 disease which is commonly called equine herpesvirus myeloencephalopathy (EHM). These immunizations do protect against the respiratory and abortion forms of the disease.

The EHV -1 vaccines are thought to reduce the shedding of the virus and may decrease the amount of circulating virus in the system of infected horses. So vaccinations prior to infection may help reduce the severity of an outbreak.

In the face of an EHV-1 outbreak, the value of vaccinating EHV-1 affected horses or exposed horses is questionable and may be detrimental to the horse. When an EHV-1 outbreak occurs, it may be helpful to give an EHV-1 booster immunization in a previously vaccinated, unexposed horse.

Consult with your veterinarian to determine the best vaccination and treatment strategy for your horses in your particular situation.

New Travel Requirements for Horses Entering Colorado
Standard requirements for horses entering Colorado include a health certificate issued within 30 days of their arrival and a negative Coggins test within 12 months. The new requirement consists of a permit to enter the state. Horse owners who wish to bring their hor se into Colorado must first call their veterinarian. That veterinarian can then contact the Colorado Department of Agriculture’s State Veterinarian’s Office at (303) 239-4161 and request a permit number. That number would then be included on the health certificate.

A Note on Easter Pet Hazards

Easter can be a time when lots of chocolate and candy are around the house. Be careful to put chocolate and candy well above the reach of pets, especially dogs. Chocolate is toxic to dogs, especially small dogs who eat large amounts. If you find your pup has dug into the easter baskets, call your vet. It’s helpful to tell the vet what the dog has eaten: what kind of chocolate (milk, dark, baker’s) and how much.

The other type of candy that can be hazardous is anything containing the sweetener xylitol.  Xylitol is found in  sugarless gums and lollipops.  This causes a massive insulin release which leads to dangerously low blood sugar.  This is an emergency and needs to be treated right away. If you find your dog has eaten candy or gum containing xylitol, load up and get to the vet quickly- in this situation it’s best to head to the hospital and call when you’re on your way.

Cats are less likely than dogs to eat candy but are not immune to dipping into the Easter baskets. The plastic “grass” for decorations can be great fun for cats to play with but very dangerous if swallowed because it can cause an intestinal blockage. For homes with cats, it’s best to use paper Easter grass instead of plastic. Although it can still cause a problem, it’s more likely to be digested if swallowed.

Most pets love a little bit of hard boiled egg. If you’re wondering what to do with all the extra eggs, give a little bit to your cat or dog with their regular meal or for a special treat.  Eggs contain a lot of protein and are an especially good dietary supplement for older pets who are losing their muscle tone.

Wishing a fun and and safe holiday to all!