What causes heartworm disease?

Heartworm disease (dirofilariasis) is a serious and potentially fatal disease in dogs. It is caused by a blood-borne parasite called Dirofilaria immitis.

Heartworms are found in the heart and adjacent large blood vessels of infected dogs. The female worm is 6 to 14 inches long (15 to 36 cm) and 1/8 inch wide (5 mm). The male is about half the size of the female. One dog may have as many as 300 worms.

How do heartworms get into the heart?

Adult heartworms live in the heart and pulmonary arteries of infected dogs. They live up to five years and, during this time; the female produces millions of offspring (microfilaria). These microfilariae live mainly in the small vessels of the bloodstream. The microfilaria cannot become adults without going through a mosquito.

The female mosquito bites an infected dog and ingests the microfilariae during a blood meal. The microfilariae develop further for 10 to 30 days in the mosquito and then enter the mouthparts of the mosquito. When this mosquito bites another dog, it transmits the microfilriae to the new dog. These larvae then develop into adult worms living in the dog’s heart, over the next 6 – 8 months.

How do dogs get infected with them?

The disease is not spread directly from dog to dog. An intermediate host, the mosquito, is required for transmission. All it takes is a few mosquito bites for a dog to become infected with heartworms.

It takes a number of years before dogs show outward signs of infection. Consequently, the disease is diagnosed mostly in four to eight year old dogs. The disease is seldom diagnosed in a dog less than one year of age because the young worms (larvae) take up five to seven months to mature after infection.

What do heartworms do to the dog?

Adult heartworms cause disease by clogging the heart and major blood vessels leading from the heart. They interfere with the valve action in the heart. By clogging the main blood vessels, the blood supply to other organs of the body is reduced, particularly the lungs, liver and kidneys, leading to malfunction of these organs.

Most dogs infected with heartworms do not show any signs of disease for as long as two years. Unfortunately, by the time clinical signs are seen, the disease is well advanced. The signs of heartworm disease depend on the number of adult worms present, the location of the worms, the length of time the worms have been present, and the degree of damage to the heart, lungs, liver, and kidneys.

The most obvious signs are a soft, dry cough, shortness of breath, weakness, nervousness, listlessness, and loss of stamina. All of these signs are most noticeable following exercise, when some dogs may even faint.

Microfilaria do not cause disease themselves but a dog with a lot of microfilaria can have severe reactions if given heartworm preventative, so a dog should NEVER be started on prevention without doing a blood test to make sure they do not already have heartworm disease.

How do I prevent my dog from getting Heartworms?

Prevention is essential in keeping your dog healthy. Monthly heartworm preventatives are available in a variety of forms. These medications are safe, effective and affordable, and should be given to every dog, every month, for every year of their life. Initially your veterinarian will need to do a simple blood test to ensure your dog does not already have heartworm, before starting the medication. Once your dog is on heartworm preventative year round, this test will be done every other year to make sure the medication is working.

Why should I get heartworm preventative from my veterinarian?

Heartworm preventative is a prescription medication that requires a consultation and examination by your doctor. Given improperly it can cause serious side effects. Many pet stores and Internet sites will offer these medications, but the manufacture only guarantees the product if purchased from a veterinarian. This is because some pet stores or internet sites may sell out-dated medications that are no longer effective, or medications from overseas that use different measurement systems, causing your pet to be either over- or under-dosed. If you have questions about your medication, or where you can obtain it, please ask your veterinarian

Feline Leukemia virus (FELV) is one of the most common and destructive of all cat viruses. It is highly contagious and is spread primarily by saliva during cat fights, grooming or mating. Kittens may become infected while still in the womb, when the mother bites off the umbilical cord or during nursing.

Not all cats exposed to (FELV) become infected. About 40% of exposed cats have immune systems that destroy the invading virus. The remainder of exposed cats become persistently infected (30%) or develop a latent infection (30%) The latter group has inactive virus in their bone marrow, and these virus particles may later become active when the cat becomes ill from another disease, stress or certain drugs. There is some evidence that older cats can become resistant to the virus, while younger cats may be particularly susceptible. In some instances, it may be beneficial to vaccinate all kittens until they are a year or two old, and then discontinue vaccination if they stay indoors after that. Ask your veterinarian for advice on whether or not your cat should be vaccinated.

Of the cats persistently infected, about 25% will die within 1 year and 75% will die within 3 years. Some may live a normal life but tend to have various chronic illnesses.

Illness

There are no signs specific for FELV infection. The main effect of the virus is to disrupt the cat's immune system. While anemia is the most common disorder caused by the virus, cancer and various other diseases are common. Disorders commonly associated with FELV infection include: chronic respiratory disease; chronic infection of the mouth, gums and tongue; chronic eye disease; frequent or chronic skin disease; reproductive disease (abortion, stillbirths and kitten deaths); frequent or chronic urinary tract infections; chronic digestive tract disease; and other systemic diseases (infectious peritonitis, hemobartonellosis, toxoplasmosis, & polyarthritis).

Prevention

Vaccination before exposure to the virus is the best means of preventing FELV infection. Without vaccination, isolation from other cats is the only means of prevention. Yearly testing of cats who go outdoors helps identify potential infections.  All cats who are the victims of a bite wound should be tested within months after the incident to ensure they did not become infected by the bite wound.

Treatment

While there is no accepted cure for Feline Leukemia we can often treat cats with specific injectable medications that can break the cycle of illness and in rare instances may help the cat to fight off the virus permanently. Your veterinarian can discuss and recommend the appropriate protocol for your pet should your cat test positive for the virus.

Important Facts

* There is a quick test that can check your cat for infection. All cats should be tested at least once in their lives.  All outdoor cats should be tested yearly, or vaccinated. 

*Cats that test positive are at risk to develop life threatening infections and cancer

There are currently 6 vaccines that we are using for dogs: Distemper combination, Leptospirosis, Rabies, Lyme Disease, and Bordetella (kennel cough), and a new vaccine to protect against dental disease.

DISTEMPER

This vaccine is actually 4 vaccines in one injection. It contains Distemper, Hepatitis, , Parvovirus, and Parainfluenza.

Puppies should receive this vaccine starting at 6-8 weeks of age and then every 3-4 weeks through 16 weeks of age. It is very important for the last vaccine to be given at 16 weeks or older because the pup’s maternal antibodies may interfere with the vaccine before that age.

Non-vaccinated adult dogs should initially receive 2 vaccines scheduled 3-4 weeks apart.

Adult dogs should receive a booster every 3 years.

LEPTOSPIROSIS

Puppies 10 weeks of age and older should be vaccinated. A booster is required 3 – 4 weeks after the initial vaccine. The vaccine is then given yearly, ideally in late winter or early spring. No more than 2 boosters should be given to a puppy during the initial vaccination period. Allergic reactions are common in smaller breed dogs. Your veterinarian will assess your pet's risk of exposure before recommending this vaccination.

RABIES

Rabies vaccines are required by law. All dogs should receive their first rabies vaccine at 3 months of age or older. The first vaccine is good for 1 year. Each additional booster2 years as long as the vaccine is kept up-to-date, 3 years in Mass. is good for

lYME DISEASE

Dogs can be vaccinated against Lyme Disease starting at 12 weeks of age or older, with a second booster required in 3 weeks. Annual boosters are recommended, ideally in late winter or early spring. Adult dogs should be tested for lyme with a 4DX test prior to initiating vaccination. Dogs that test positive should be treated with a course of antibiotics prior to initiating vaccination.

Dogs can be vaccinated as early as 8 weeks of age. It is recommended that the vaccine be administered at least 7 days prior to boarding. This vaccine may also be required for dog shows, obedience classes, and by some groomers. Annual vaccination is required to maintain protection.

Porphorymous Vaccine(Dental Vaccine)

Dogs can be vaccinated at anytime for this vaccine, it does not need to be boostered, but may be administered every 6 – 12 months depending on the severity of your pet's dental disease. This vaccine does NOT prevent tartar, but it does help protect the gums and teeth from the bacteria that build up around tartar and lead to tooth loss and gingival diesease. Some dog's experience muscle pain after receiving this vaccination so your veterinarian may recommend an anti-inflammatory for comfort.

There are currently 3 vaccines that we are using for cats:

Distemper combination (FVRCP), Rabies, Feline Leukemia Virus (FELV).

DISTEMPER

This vaccine is actually 3 vaccines in one injection. It contains Distemper (Panleukopenia), Rhinotracheitis, and Calicivirus.

Kittens should receive this vaccine starting at 6-8 weeks of age and then every 3-4 weeks through 12 weeks of age. It is very important for the last vaccine to be given at 12 weeks or older because the kitten’s maternal antibodies may interfere with the vaccine before that age. The vaccine should be boostered again 1 year later, and then every 3 years after that.

Non-vaccinated adult cats should initially receive 2 vaccines scheduled 3-4 weeks apart

Adult cats with prior vaccination should receive a distemper vaccine every 3 years.

RABIES

Rabies vaccines are required by law. All cats should receive their first rabies vaccine at 3 months of age or older. The first vaccine is good for 1 year. Each additional booster is good for 2 years as long as the vaccine is kept up-to-date, 3 years in Mass.

Feline Leukemia (FELV) and Feline Immunosuppressive Virus (FIV)

Unfortunately, FELV and FIV are very common in this area. They are highly contagious and attack the immune system, thus impairing the cat’s defense cells. We strongly recommend testing for these 2 viruses (usually at the cat’s first veterinary visit). There is no cure for either disease; however, there is a preventative vaccine for FELV. Vaccination is most important in outside cats.

Cats can be vaccinated against Feline Leukemia Virus starting at 9 weeks of age with an additional booster required in 3-4 weeks. Annual boosters are necessary to maintain protection.

While there is a vaccine against FIV, it only protects against 40% of the strains of virus that cause the disease, and it leads to confusing test results when trying to diagnose the disease. At this time, the vaccine is only recommended for outdoor cats that have a tendency to get into cat fights. Once a cat is vaccinated, it will test positive for the disease. Cats that spend a lot of time outdoors, or are involved in a fight that results in bite wounds should be tested yearly for FIV.

Feline Infectious Peritonitis (FIP)

FIP is another highly contagious and lethal virus of cats. There is no cure. Though there is a vaccine available it has not been shown to be very effective at preventing the disease, and in some cases, may actually trigger clinical signs. In most cases, vaccination is not recommended.

During your pet's annual exam, your veterinarian may recommend routine bloodwork.  These tests check your pet for any signs of infection, anemia, and for any problems with internal organ function or hormonal imbalance.  Whenever possible, it is valuable for these tests to be run for many reasons.

  If your pet were to become ill, any abnormal test values could be compared to blood results obtained when your pet was well to more accurately diagnose a problem. 

 In many cases, animals that appear perfectly normal will have abnormal blood test results that help your veterinarian identify a potential illness, and treat or avoid it before it can cause serious health issues.  Certain parasitic and infectious diseases can be identified BEFORE they make your pet sick. Treatment before illness avoids emergency visits and costly hospitalizations.  

 If your pet requires medications, such as pain medications for arthritis, or medications for persistent allergies, routine blood testing ensures that there will be no contraindications to the medications and helps to avoid any potential adverse affects.

Lastly, if your pet ever requires any sedation or anesthesia for an emergency surgical procedure, having baseline bloodwork from your pet will help your veterinarian develop a healthy anesthetic protocol for your pet's procedure.

If you have questions about blood testing and your pet, please ask your veterinarian.