Many people have heard of heartworm disease but aren’t exactly sure what it is, so let’s review: Heartworm disease is a serious and potentially fatal disease of dogs, cats, ferrets and certain wildlife, including wolves, coyotes, foxes and sea lions. It is caused by foot-long worms that live in the heart, lungs, and nearby blood vessels. These worms can cause heart failure and severe damage to the lungs and other organs of the body. Heartworm is transmitted by mosquitos, and adult worms can live for 5 to 7 years in dogs and up to 2 or 3 years in cats.
For the most part, dogs are a natural host for heartworms. This means that heartworms living inside a dog mature into adults and produce larvae called microfilaria, which is the stage that is transmittable by mosquitos. Left untreated, their numbers will increase, and dogs have been known to harbor several hundred worms in their bodies.
A cat, however, is an atypical host for heartworms, and cats with adult heartworms typically have just one to three worms. Many cats affected by heartworm have only immature worms present, but this does not mean they don’t cause problems. Even immature worms can cause damage in the form of a condition known as “heartworm associated respiratory disease” (HARD). Heartworms can cause respiratory and circulatory system damage and can affect the cat’s immune system, causing symptoms such as coughing, wheezing and difficulty breathing.
In a few cases, heartworm in cats may even migrate to other parts of their body, such as the brain, eye and spinal cord. Severe complications such as blood clots in the lungs and lung inflammation can result when adult worms die in the cat’s body. There is NO treatment for heartworm in cats, as the medication used to treat heartworm infection in dogs is toxic to cats. The treatment goal for cats is stabilization and determining a long-term management plan. Prevention is the only means of protecting cats from the effects of heartworm disease.
Signs of heartworm disease in cats can be very subtle or very dramatic. Symptoms may include coughing, asthma-like attacks, periodic vomiting, lack of appetite or weight loss. Occasionally, an affected cat may have difficulty walking, experience fainting or seizures, or suffer from fluid accumulation in the abdomen. Unfortunately, in some cases, the only sign is sudden death.
How do you know if your cat has heartworm?
Diagnosis can be complicated, as infection in cats is harder to detect than in dogs. This is because the standard antigen test only checks for markers of adult female worms. If the worm(s) are all male, or they don’t have any adult worms at all, the test will be negative. The preferred method for screening cats includes the use of both an antigen and an antibody test. The antibody test detects exposure to microfilaria. Additional tests may include x-rays or ultrasound.
Because there are no approved treatments for feline heartworm infection, prevention is critical. There are several good monthly preventatives on the market. Some medicines are topical (applied to the skin), and others are given by mouth.
So, what is the risk of heartworm disease in Montana?
The risk of transmission for canine heartworm is low in Montana due to the relatively cool, short summers which prevent the development of microfilaria to the infective stage in the mosquito. However, heartworm disease is spreading to new regions of the country each year. Mosquitos blown great distances by the wind and infected pets relocated to previously uninfected areas contribute to the spread of heartworm disease. For example, this happened after Hurricane Katrina when 250,000 pets, many of them infected with heartworm, were adopted and shipped throughout the country.
To assess the prevalence of heartworm infection in Montanan mosquitos, over 60,000 mosquitos from 12 Montana counties in 2005 and 2007 were collected and tested for the parasite. None of the mosquitos tested positive for canine heartworm. However, this was over 10 years ago. We recently contacted the State Veterinarian’s office and learned that there are currently 2 small areas in Montana where heartworm now seems to be endemic: an area near Yellowstone and an area near the center of the state. We also learned that there have been longer infection seasons for “seasonal” diseases, such as West Nile in horses.
While Cats on Broadway does not currently recommend a monthly heartworm preventative for cats living in Missoula, we do recommend providing a monthly preventative for cats that travel out of state. This will protect your pet and the pets of your friends and family. Even though it’s not a problem now, it is inevitable that heartworm will one day become endemic throughout the state of Montana.
If you have any questions about exposure to heartworm, please contact our office! Thank you! =^_^=