Heartworm disease has been reported in all 50 states. The American heartworm society recommends year round prevention for all cats and dogs. Heartworm disease has a greater incidence in the southeast where the disease is very common.
The disease is transmitted by mosquitoes. They become infected when feeding on infected animals. After 2 weeks, the infective larvae mature and can infect other animals when the infected mosquito bites again. Interestingly, heartworm disease has been reported in many other animals, too.
Recently, there have been a few cases of positive dogs while receiving heartworm preventative in the Mississippi river delta area (Tennessee, Louisiana, Arkansan and Mississippi). Although certain resistance of the parasite may have occurred, the two common factors related to this lack-of-efficacy cases are inconsistent administration of preventative medications and inappropriate testing intervals. An ongoing study looking into these reported cases in the Mississippi river delta area has shown that 77% of the reported cases were due to gaps in purchase of preventative, 20% were due to compliance on administration of the already purchased preventative and only 3% of the cases were probably due to failure from the medication. Another study in the USA has shown that compliance with heartworm preventative is less than 50%.
The take home message is that:
- Preventative medication must be given every 30 days. Compliance includes not only the time that medication is given, but also appropriate administration or application of the medication in the proper weight range.
- Heartworm prevention must be started at 8 weeks of age. About 13% of the reported cases of lack of efficacy occurred in puppies due to a late beginning in the use of preventative.
-Heartworm disease should be tested every year.
- Heartworm cases have been reported in all 50 states, and for that reason, the American Heartworm Society recommends year round prevention in all USA.
Vey useful website on heartworm disease are:
- The American Heartworm Society http://www.heartwormsociety.org/
For any further questions, please contact me at drdavid@semobilevet.com. I would be happy to answer any questions.
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