Photo by Flickr user Tankanawho

Heartworm season is well upon us now, and if your pets aren't already protected, there is now time like the present to get started!

Heartworm is a devastating parasitic disease. Pets become infected when they are bitten by a mosquito containing microscopic larvae. These tiny larvae travel through the skin and blood vessels and eventually become large worms (up to 12 inches) that lodge in the heart and major blood vessels of the lungs.

Currently the American Heartworm Society recommends that all dogs and cats be kept on year-round heartworm prevention. Dogs will need to have an annual heartworm test (blood test) to make sure they are negative. Heartworm prevention comes in many forms: topicals applied every 30 days, tablets/chewy treats eaten every 30 days or injections given every 6 months. T

hough there are subtle difference in the ways these products work, they are all effective at preventing heartworm disease when they are given faithfully on schedule. Treating heartworm disease in dogs is possible, but it is expensive and risky. Heartworm infected dogs are given multiple injections of an arsenic derived compound after a full medical work-up. The cost of treatment is usually about equal to the cost of keeping them on heartworm prevention for their whole lives.

But did you know that cats get heartworms too?

Photo by Flickr user sub_lime79

Though many people are aware of the risks of heartworm disease in dogs, most do not even know that their cats should also be on preventatives.

The main difference between cats and dogs is that cats generally produce a more robust immune response to heartworm disease. The good side to this exuberant immune response is that cats tend to have fewer total worms than dogs, and their bodies are more likely to be able to clear the infection naturally.

However, the downside to this strong immune response is that cats are much more difficult to diagnose than dogs and they often develop a significant amount of damage to their lungs in the process. The inflammation in cats' lungs is called Heartworm Associated Respiratory Disease and can be associated with lethargy, not eating, weight loss, coughing, panting, open-mouthed breathing, gagging, wheezing and rapid breathing.

This condition is commonly misdiagnosed as asthma or allergies. Other signs of heartworm infection in cats include chronic vomiting and sudden death. There are tests available to diagnose heartworm disease in cats, but they are much less reliable than the tests available for dogs. For this reason, it is recommended that all cats be given a heartworm prevention (topical or oral pill/chew) every 30 days for life.

Important note: Indoor cats are also at risk for heartworm disease! Because this disease is carried by mosquitoes, people mistakenly believe that their indoor cats are safe. This is not true. Cats who are supposedly indoor only are diagnosed with heartworm disease at surprisingly high rates (approximately 1/3 of all cases).

Heartworm disease has plagued the health of our pets in all states for many years. With good prevention, this disease can be completely avoided. This is why heartworm testing and heartworm prevention has become such an important part of veterinarians' wellness routines.

As we move forward, the importance of heartworm prevention in cats must take a more prominent role in feline wellness. Our kitties deserve the best!

Dr. Lyssa Alexander treats small and exotic animals and pocket pets at All Creatures Animal Clinic.

References:
1. American Heartworm Society: http://www.heartwormsociety.org/
2. Lister, A. L., Atwell, R. B. Feline heartworm disease: a clinical review, Journal of Feline Medicine and Surgery, 10 (2), 2008, 137-144.