American Heartworm Society FAQ section comments

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Do pets really need medication every month for worms, fleas and ticks?

American Heartworm Society FAQ section comments

Postby malernee » Mon May 08, 2006 4:24 pm

http://www.heartwormsociety.org/FAQ.htm
I heard that yearly tests for heartworms are not recommended anymore. Is this true? How often should I have my dog tested?.

Annual testing for heartworm infection is now highly recommended. Even though heartworm preventives, particularly monthly oral and topical formulations and the injectable product, are essentially 100% in preventing infection when administered according to instructions on the label, animals on heartworm prevention occasionally test positive for heartworms. This apparent lack of efficacy is usually due to owner compliance failure, travel or relocation of the animal to an area of active heartworm transmission, or unknown (or misdiagnosed) prior infection. Annual testing gives owners peace of mind in knowing that their pet is free of heartworms, and in cases where the animal is infected, it assures them of early diagnosis of infection and maximal benefits from heartworm adulticide therapy.
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>>>From http://www.heartwormsociety.org/FAQ.htm

I heard that yearly tests for heartworms are not recommended anymore. Is this true? How often should I have my dog tested?. Annual testing for heartworm infection is now highly recommended.>>>

this american heatworm society guide is a non evidence based guide paid for by those selling heartworm related medical care.



>>> Annual testing gives owners peace of mind in knowing that their pet is free of heartworms, >>>

Why not test every six months to give them six month peace of mind? Why settle for just annual peace of mind. Why not test for 4 times a year peace of mind? How much peace of mind do the 27 out of 28 clients get whose dogs are on a consistent heartworm preventative medication program from false postive test results? When you are told your dog has heartworms and he does not how much peace of mind do you get from that?

see

from canada vet journal volume 41 dec 2000 page 936 I quote " thus for dogs on a consistent preventative medication program, only 1 out of every 28 positive antigen tests is likely to be a true positive."

>>>and in cases where the animal is infected, it assures them of early diagnosis of infection>>

for dogs on a consistent preventative medication program the annual heartworm test almost assures the client NOT of an early diagnosis but of an early misdiagnosis. Evidence base studies out of Canada show, the client paying for the heartworm test whose dog is on a consistent preventative medication program only has one chance out of 28 heartworm positive tests that the pet really has heartworms.



>>> and maximal benefits from heartworm adulticide therapy.>>>

FDA approved Adult Heartworm therapy is labed contraindicated for dogs with sever heartworm disease and has not been shown to increase life expectancy or quality of life any more than letting the adult heartworms die on their own.

Article from peer-reviewed vet journal in Canada.


can vet j volume 41 dec 2000 page 936
"Heartworm infection does not invarably lead to disease and death. In fact it is generally accepted that low heartworm burdens (<20 worms) are rarely of clinical significance (41),although such dogs should be monitored more closely. It would appear from canada more dogs are euthanized because they tested postive than would ever become symptomatic or die from heartworm infection."

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ask yourself
is this evidence about needing an annual heartworm diagnostic test valid?
1. Was there an independent, blind comparison with a reference (gold) standard of diagnosis

2. was the diagnostic test evaluated in an appropriate spectrum of patients (like those in whom we would use in practice?

3. Was the reference standard applied regardless of the diagnostic test result?

4. was the test ( or cluster of test) validated in a second, independent group of patients?
remember every measurement is an approximation

These are all conditions where well validated screening tests exist and for which the benefit of early treatment has been established. My disagreement the American Heartworm Society answer is with the use of a poorly validated or difficult to interpret tests such as one with such a high false positive rate, or where there is no clear benefit to making a diagnosis prior to the advent of clinical signs if the dog is already taking medication to kill heartworms.

From the American Heartworm Society April 2001 Symposium: McCall, Further Evidence of Clinical Prophylactic and Adulticide Activity of Monthly Administration of Ivermectin and Pyrantel Pamoate in Dogs Experimentallly Infected with Heartworms. When started at 5 months post infection, after 36 months, HGplus was 98.7% effective in eliminating adult heartworms.

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Remember Review articles, particularly those written by specialists, tend to be of dubious value, with authors selectively choosing evidence to support their own prejudices. I would argue, however, that most practicing clinicians know this already but find value in following what the so called "experts" say should be done. Animals put into an at risk category may benefit from heartworm testing.
There is no randomized controlled study to justify the cost and risk of serial antigen heartworm testing. Evidence based studys show a 3-5% chance of having heartworm need be present to make any antigen testing worth while in clinical practice. Serial heartworm testing should not be promoted by so called heartworm experts unless promoted as investigational medical care. Members of heartworm associations that are not promoting serial heartworm testing as investigational care need to find another job and stop taking money from heartworm testing and treatment drug companies.



art malernee dvm
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