Heartworm is a very serious disease that can spread from one dog to another and, less frequently, from cat to cat. In adult canines and felines, mosquitoes are responsible for the spread of heartworm. Once in the bloodstream, heartworms gradually lodge in the heart’s right ventricle as well as other organs.

Without treatment, the heartworm cycle is endless as it spreads in dogs or cats. A mosquito bites an infected animal. The larvae, or microfilariae, transfer to the mosquito. When the insect then feeds on another animal, the larvae are deposited into the bloodstream. As the larvae develop into adults in dogs or cats, they may reside in veins and lungs. In time, they will travel to the heart and breed. Female heartworms will produce thousands of live young. They, in turn, live in the bloodstream and eventually will transfer to their mosquito hosts.

Adult heartworms can grow to nearly 12″ in length. They can survive inside canines for as long as 7 years and about 3 years in felines. Not all cats or dogs exhibit symptoms until the heartworm population has spread and grown. In fact, thousands of the young heartworms can thrive in the bloodstream before signs of illness are present.

For dogs, a blood test can usually identify the microfilariae. However, cats require additional testing as the blood may not always provide reliable indication of the disease. Heartworm spread in cats is slower and the molting worms are less likely to reach the heart. Problems can arise from arterial complications and a single worm can cause distress or fatalities. Research also indicates that female cats are more resistant to heartworm disease spread than their male counterparts.

Heartworm spread can occur almost anywhere in the world, with the exception of Antarctica. Areas that typically are conducive to higher mosquito populations will see greater occurrences of heart worm spread in untreated animals.

Prevention, of course, is the most important factor in controlling the spread of heartworm in dogs. Preventing heartworm spread in cats is still a matter for much discussion among veterinarians. Testing should be conducted before beginning any course of medication. Spring is a recommended time to test as a seven-month incubation period typically occurs before the larvae are large enough for detection. Preventative treatments can cause adverse-to-serious reactions when heartworms are already present. Monthly or regularly scheduled heartworm medications work to kill any larvae in the bloodstream.