Well, let’s see what we have learned about that rapidly spreading scourge of heartworm. Firstly, we know that it is transmitted by mosquitoes. Secondly, we know that the adult worms (bundles) live in the right heart chambers (and sometimes in some of the big and important blood vessels), thus greatly compromising the function of the heart. Thirdly, and very importantly, we know that this disease (ie the development of the visible symptoms) sneaks up on the
poor animal, and by the time we begin to see signs of the ailment, the efficiency of many organ systems (liver, kidney, lungs, the heart itself) is impaired.
Lastly, we had documented that the main symptoms were (i) a soft, deep cough (ii) lethargy and (iii) loss of condition (weight loss).
So how do we keep tabs on the possibility of this disease developing? Simple: We check the blood. Your veterinarian can take a droplet of blood and examine it. Once the microfilariae (the immature stage of the heartworm) are seen, that is pretty much indicative of the presence of heartworm in the right heart chambers and possibly in other large blood vessels.
But you remember last week I said that this laboratory diagnosis is neither straightforward nor conclusive.
For one thing, if you don’t find these immature stages of the heartworm in the blood sample, that does not mean that there is no heartworm. Let’s give the reasons why this is so:
i) Some of our veterinarians are using, as a general dewormer, exactly the same drug (Ivermectin) that kills the microfilariae (immature stages of the heartworm)! This means that if that very efficient drug kills the microfilariae then the vet won’t find them; yet the adult heartworms might have been existing in the heart quite happily for some time before the administration of the drug that kills the microfilariae (the drug does not kill the adult). This is a terrible state of affairs. I suppose the solution would be to check the blood for the immature stages of heartworm before administering the drug mentioned above.
ii) The amount of microfilariae that are circulating at the time of sample-taking might be so small that they will not be easily picked up during the microscopic examination of the blood droplet.
iii) Some dogs actually have an immune system that is so strong that it develops antibodies that can kill the microfilariae, but cannot damage the adult heartworm in the heart chambers.
iv) At the time when the blood sample is taken, the worms in the heart might not have reached the stage of actual sexual maturity. In other words they were not quite adult and therefore could not mate and produce offspring (microfilariae).
v) Lastly, and remotely possible, the worms in the heart could all be one of sex only. Consequently, it would not be possible for them to mate and reproduce offspring (microfilariae).
What does all of this demand of your veterinarian? Simply put, your veterinarian must make it a part of his or her routine examination to check the dog’s blood for this parasite. This means (which can be deduced from the points made above) that the samples must be taken at regular intervals! It also means that if after several blood checks there is no sign of the microfilariae, then prophylactic measures (medication) should be introduced. If, on the other hand, the presence of a heartworm burden has been identified, then therapy must immediately be introduced – or your dog will die a slow and excruciating death (guaranteed!) The prevention and cure of heartworm will be dealt with next week.
Please implement disease preventative measures (vaccinations, routine dewormings, monthly anti-heartworm medication, etc) and adopt-a-pet from the GSPCA’s Animal Clinic and Shelter at Robb Street and Orange Walk, if you have the wherewithal to care well for the animals. Do not stray your unwanted pets, take them to the GSPCA Clinic and Shelter instead. If you see anyone being cruel to an animal, get in touch with the Clinic and Shelter by calling 226-4237.
