Heartworm (Dirofilaria Immitis)

FACTS: You're not the only one who loves dogs - numerous parasites on the inside and outside of man's best friend use him as their own little ecosystem. Most are harmless annoyances, but heartworm (or Dirofilaria immitis) can cause serious complications and even death if left untreated.

Thin, spaghetti-like parasites, heartworms typically reside in the pulmonary arteries and hearts of their hosts. An infected dog can have as many as 250 worms. As they grow, the worms constrict blood supplies to the heart and lungs, causing infected animals to develop coughs, become listless, and lose their appetites.

Microscopic offspring called microfilariae are released by female worms after mating. These get sucked up by mosquitoes and develop into larvae that can infect the next host. Because larvae can only develop when it's hot, summer is a particularly dangerous time for transmission. However, since symptoms take six months to appear, winter is the time to be most aware.

If one of these worms works its way into your dog's heart, there are treatments available that can help. Preventatives can also be used. However, these medications are dangerous if your dog already has heartworm, so be sure to test your pet before administering them.

Remember: keeping control of heartworm is the best way to ensure your dog keeps only you in his heart.