Mosquitoes bite dogs, too
Prevent heartworms and other bug-borne diseases in your pet

Editor's note: This is the first in a two-part series explaining the dangers mosquitoes pose to pets.
Buzz, ouch, slap slap, buzz, slap!
Do you recognize these sounds? Not exactly what you would call sounds of the wild, but if you have spent any time outdoors lately, you know what I am talking about. Mosquitoes are here, and they are here in numbers. While these nasty, annoying little blood suckers can make an outing miserable, they can also be the precursor to major health problems not only for us, but for our pets.
Make no joke about it: We are at war with these tiny vampires. A long time ago I was taught that if you are going to war, you had better know your enemy.
Worldwide, mosquito-borne diseases kill more people than any other single factor. In the United States, mosquitoes spread several types of encephalitis, dog heartworm and malaria. In many species of animals, the female is the most deadly, and this is the case with mosquitoes. Only the female mosquitoes bite. They zero in on their prey like something out of a sci-fi movie. The mosquito's visual picture, detected by various parts of its body, is an infrared image produced by its prey's body temperature.
Not only do we have to protect ourselves from the potential health risk that mosquitoes carry, we also must ensure that we protect our pets from danger. The most common ailment in pets caused by mosquitoes is dirofilariasis, or heartworm disease. Heartworm is a serious and potentially fatal disease in dogs. The disease can also be found in our feline friends, but cats are not the preferred host of the heartworm.
According to Dr. Elisa Spears of the Call Field Companion Animal Clinic, heartworms are found in the heart and large adjacent vessels of infected pets. The female worm is 6 to 14 inches long and 1/8 inch wide. The male is about half the size of the female. One dog may have as many as 300 worms. Spears adds that heartworms can survive inside a dog for as long as five years and, during this time, the female produces millions of young or microfilaria. These microfilaria live in the bloodstream, mainly in the small blood vessels. The immature heartworms, however, cannot complete the entire life cycle inside the dog; the mosquito is required for some stages of the heartworm life cycle.
So how does a dog contract heartworms? Spears explained that when the female mosquito bites an infected dog, she ingests the microfilariae during the blood meal. The microfilariae develop further in the mosquito for 10 to 30 days and then enter the mouthparts of the mosquito. The microfilariae are now called infective larvae because at this stage of development, they will grow to adulthood when the mosquito, seeking another blood meal, injects them into the next unsuspecting host dog.
The mosquito bites the dog where its coat is thinnest. Having long hair, however, does not prevent a dog from being bitten and getting heartworms.
The larvae remain under the dog's skin for about two months. Then the infective larvae enter the dog's bloodstream and move to the heart and adjacent vessels, where they grow to maturity in two to three months and start reproducing, thereby completing the full life cycle. The complete process, from the time the larvae penetrate the skin until the microfilariae are produced by adults, takes approximately six months.
Spears also states that it takes as long as two years before dogs show the outward symptoms of infection. Consequently, the disease is diagnosed mostly in 4- to 8-year-old dogs. It is seldom diagnosed in a dog under 1 year of age because the young worms take up to seven months to mature following establishment of infection in a dog.
The signs of heartworm disease depend on the number of adult worms present, the location of the worms, the length of time the worms have been present, and the degree of damage to the heart, lungs, liver, and kidneys from the adult worms and the microfilariae.
Spears warned that pet owners should watch for the signs that your dog could be infected with heartworms. These signs are: a soft, dry, chronic cough, shortness of breath, weakness, nervousness, listlessness and loss of stamina. All of these indications are most noticeable following exercise, when some dogs may even faint. Severely infected dogs may die suddenly during exercise or excitement. Next week's article will address the diagnostic tests and therapies that vets use to treat dogs that have heartworms.
Spears said the best advice for pet owners is that an ounce of prevention is worth a pound of cure. It is essential to begin and maintain your dog on a heartworm prevention program. Preventive doses come in oral and topical versions and are available only from a veterinarian. While heartworm preventative medication can be given on a daily basis, Spears said that most clients prefer giving their pets a monthly dose. As an added bonus, some of these drugs also kill other parasitic worms, and one, Revolution, also acts against fleas, ticks and mites. A new product on the market allows pet owners to have their dogs receive heartworm medicine once every six months.
So do the right thing. Protect your dog and cats from the onslaught of mosquitoes and the possibility of contracting heartworms. Make sure you visit your vet and place your pet on a heartworm preventative. The cost of this proactive response is small compared to the cost of having your pet treated if it does become infected with heartworms.
Also, if you want to spray your pet with an insect repellent, make sure that it is safe to use on animals. Never use any spray that contains DEET, an ingredient in most insect repellents. If you would like to use natural repellents, you can visit online www.naturespets.com to find a wide variety of natural, animal-friendly repellents.
Another serious disease spread by mosquitoes that infects both animals and human beings is the West Nile Virus. My next article will examine the threat of this disease, which is now beginning to show up in Texas.