Drugs have been developed that will prevent dogs from contracting heartworm. The drug attacks the immature stages of the parasite in the dog and prevents the worms from maturing to the adult stage. Therefore, a dog that is on medication can be repeatedly infected during the mosquito season and remain free of heartworm. The medication available prior to 1983 was quickly excreted by the animal and had to be administered daily throughout the mosquito season. A new drug is now available in tablet form that provides protection for one month.
Preventative medication can cause complications in animals with established heartworm infections.
As a result, the drugs are available only through veterinarians and should be administered under their directions. The use of preventative medication does not exclude periodic blood tests. The combination has saved the lives of many dogs. Protecting dogs from mosquito bites may be necessary in areas where mosquito populations are high. Screening the dog's sleeping quarters is essential to prevent repeated bites.