Heartworms in Dogs

Heartworm infestation afflicts most canines and some feline species the world over. It has become a major concern of owners of pet dogs and just recently, even cats. Left untreated, heartworm infestation in dogs is dangerous and often fatal.

The parasite is transmitted from one animal to the other through mosquitoes, which serve as the vector. Dogs are normally put on preventive medication, which kills off the parasites at larval stage, while they are circulating in the dog’s blood. However, adult heartworms already lodged in its heart or lungs can only be eradicated by administering a stronger dose, physically removing the parasites through surgical procedure, or just waiting a couple of years until the parasites die off.

Some pet owners have expressed some concern on the possibility of a correlation between the preventive medication, Heartgard, and infertility in the animal to which it is administered.

Considering the relative ease by which heartworms can be transmitted from one dog to another through mosquito bite, pet dogs are normally placed on preventive medication. Because of this lifetime medication, dog breeders notice that only two-thirds of breedings result in conceptions. Consequently, they feel that there is a connection between Heartgard and infertility in dogs.

Dogs are man’s best friend, and are often times considered as part of the family, too. That is why dog owners are often painfully locked in the horns of a dilemma—between wanting to put their pet on preventive medication, and at the same time dreading at the thought that their pet might lose in the process its capability to perpetuate its own specie. Concerned dog breeders always worriedly ask themselves: “Are the misses in my dog’s conception indicative of a correlation between Heartgard and infertility?”

There have been no published studies that point to a correlation between Heartgard and infertility in dogs. And it would be more reasonable to assume that these misses are simply natural failures in conception. Following this reasoning, it would be logical to think that if the preventive medication indeed causes infertility, then this would result in a total absence of conception and not just misses. Aside from dogs, it has also been determined that there is also no connection between Heartgard and infertility in other species such as cattle, horses, cats, rodents and even birds and chickens.

It is also interesting to note that ivermectin, the primary ingredient in Heartgard, is also present in broad spectrum medication that is used to treat humans of worm infestations. There have also been cases of its off label use in the treatment of scabies and mites which have proven resistant to topical applications. Because of its use as an anti-parasitic agent in humans, the World Health Organization conducted laboratory tests on ivermectin and have found no conclusive evidence linking ivermectin, the primary ingredient in Heartgard, and infertility in humans.

A Fallacy… Heartgard Causes Dog Infertility Heartgard has no known side effects if the recommended dosage is followed. The dog would have dilated pupils, a considerable body weight loss, manifest shaking or trembling movement if an over...