Dr. Bruce Williams (in response to Sandra) said:
>>I have a question regarding doing a snap test for a heartworm check in a
>>ferret--if a ferret can harbor only one or two adult worms, what if they
>>happen to be male worms?  I understand that a snap test only indicates
>>if an adult female is the culprit; apparently it detects the hormones
>>put out by a female?
 
>While I am not an expert in the occult heartworm test, I believe that the
>antigen that is used is a saline extract of whole female worms, not a
>hormone that they put out.  This means that the test looks for sustances
>that would be part of the body of the worm, and should be present in both
>sexes.  As such, I think that even exclusively male infections should be
>picked up by the test.
 
Here's ANOTHER thing that the FML has taught me - and I learn a whole
lot from the FML.  Within 24 hours of this post, another vet with more
knowledge on this subject has straightened me out on the composition of
the antigen used in the occult heartworm test.  (I am not reprinting their
name as they sent the message to me offline, but I will find out if they
would like credit and report back.)
 
They write: "...I just wanted to comment that the antigen test looks for
somatic antigens on the heartworm cuticle.  The specific antigen is found
only in female worms.  Therefore, an exclusively male population would be
missed by this test.  This is the case for dogs, cats, and ferrets.
However, the test may also miss one or two worm infections as well because
the antigen load may be below detectable levels.  As you are acutely aware,
no test can really be 100% sensitive and we must combine test results with
clinical interpretation and ancillary test results to achieve a proper
diagnosis.  "
 
With kindest regards,
Bruce Williams, dVM
[Posted in FML issue 3234]