Just as there is pre- ventative for dogs, there is preventative for cats. Heartguard provides a beef pill, given once a month, to prevent heartworms and hookworms in cats. Because of the low accuracy in tests, cats do not need to be test- ed prior to giving the prevention.

We are seeing a grow- ing concern for feline heartworms and think that it is very impor- tant to alert pet own- ers. If you have ques- tions, please call us.

Most dog owners under- stand the threat of heartworms developing in their companion's heart, but we are now seeing an increase in feline heartworms. In this newsletter, we want to help people understand how heart- worms are now a threat to the feline communi- ty. Dog owners, you have not been left out. The heartworm life cycle is the same in cats and dogs. Here are some interesting facts about canine heart- worms!

So what are heart- worms? Well, they are a type of round worm called Dirofilaria im- mitis that live in the right ventricle of the heart and adjoining large vessels. While living in their host's heart, the adult heart- worms will breed and produce baby heart- worms called micro- filariae (to keep every- one from getting con- fused, we will refer to the dog or the cat as the "host").

So where does the mosquito come into play? The mosquito will ingest the microfilariae (L1) during the blood feast and continue the life cycle of the heart- worm. The microfilaria will molt a couple of times (L1-L2-L3) and develop into larva (L3) that is able to grow in its host. Now the mos- quito is ready to infect the host. The micro- filariae must complete this molting stage in- side the mosquito or the heartworm will not develop. When the mosquito bites the host, the larva (L3)

moves out of the mos- quito's spiracles and bores into the host's skin. As the L3 larva migrates through the host's tissue, it will molt a couple of more times (L3-L4-L5) into the L5 larva. By this L5 stage, the larva will find its way to the host's blood- stream. The L5 larvae will make their way to the heart where they will develop into the adult heartworm. The adults will then breed and produce micro- filariae (L1). The micro- filariae will circulate in the host's circulatory system. When a mos- quito bites an infected host, it will ingest the L1 microfilariae and the vicious cycle repeats.

Why are we now dis- covering these nasty worms in cats and what are some differences between the canine and feline heartworms? Cats are not the normal host for D. immitis. Some scientists think it is because cats' im- mune system fights D. immitis larvae and microfilariae more effectively. Another theory is that the cat's heart is not the ideal breeding ground for heartworms. There must be a male and a female heartworm present to reproduce. If a cat has all males or all females, micro- filariae will not be pro- duced. Dogs can have over 100 heartworms in their heart, where cats will usually only develop 2 to 4 heartworms, The normal life span for a canine heartworm is about five years, where feline heartworms only live for about 2 years. A good rule of thumb is

that cats are suscept- ible, but not resistant.

What about heartworm tests? There are tests available to know if a cat has heartworms, but they are not 100% accurate. The in clinic canine heartworm test will test for the antigen from the adult heart- worms. Because of the low adult heartworm count in cats, there is not an accurate test available that can be performed in the clinic. A sample must be sent off to a special labo- ratory. They can per- form a more sensitive test.

What are some of the signs of heartworms? The signs of heart- worms in cats can be the same as in dogs. a cat may show signs of congestive heart fail- ure, coughing, dyspnea (having trouble breath- ing), and lethargy. Other signs, associated with the above signs, are vomiting or gag- ging, and/or weight loss. Somje cats may not experience any signs at all and live normal lives. However, be aware that feline heartworms can be fatal.

Canine heartworm treatment has im- proved tremendously over the years. Treat- ment of canine heart- worms is safe and more effective. However, feline heartworm treat- ment can be as hazard- ous or even as fatal the the worms themselves. Since feline heartworms have a shorter lifespan, most of the time treat- ing the signs is more effective.