ASK THE VETS: The danger of heartworm disease is high; stick to your pet's medication regimen.
Question: My Friends Dog was taking the same heartworm medication that I use for mine. Her dog died in the emergency room last week from an illness known as IMHA. It could have been related to the heartworm treatment she had given two days before or the Lyme disease vaccine she had given a week before, according to the emergency doctor. Is it necessary for me to switch heartworm medications?
Because of this story, please do not adjust your heartworm meds or, even worse, cease giving heartworm preventives. Immune mediated hemolytic anemia, or IMHA, is a failure of the immune system in which the body attacks and destroys its own red blood cells.
We don't know enough about the immune system to know for sure why it malfunctions on sometimes. We do know that the IMHA condition has a hereditary component. The gene can be found in particular breeds and lines. In every case, this is the only certain cause. However, we also know that any immune system stimulation might cause an attack in susceptible animals.
The immune system is stimulated by thousands of different challenges every day. The immune system is stimulated by bacteria in the mouth or on the skin. It is triggered by viruses and pollen in the air. Environmental chemicals and detergents stimulate the immune system. An immunological response can be triggered by bug bites and protein in meals.
Vaccines are intended to promote an immunological response, thus they can actually cause a crisis in IMHA patients. If an animal is susceptible to a drug, it has the ability to boost the immune system. When a patient with IMHA has a crisis, it's usually impossible to pinpoint what caused it—unless it's linked to a vaccine or a known insect bite.
While the specifics will have to wait for a future post, I am a firm believer in Lyme disease immunization for practically all dogs. I like the newer recombinant-DNA vaccines, which are gentler on the immune system than the older "whole cell" immunizations, which are more prone to trigger a reaction.
Vaccines should be avoided as much as possible in a pet with a history of IMHA or a family history of the disease. Consult your veterinarian about the best regimen for your particular pet.
Heartworm preventives are frequently blamed by pet owners for IMHA reactions, although there is no scientific evidence that they stimulate the immune system any more than other drugs and substances that pets are exposed to. It turns out that one out of every five dogs suffering from a IMHA crisis had taken a heartworm preventative within the previous week.
Many individuals take the easy way out and claim that this is proof of a link. However, correlation does not always imply causality. A heartworm tablet was given to the same percentage of dogs hit by autos in the previous week. Why? Not because the drugs cause vehicle accidents, but because most dogs only get these medicines once a month!
The essential message here is that you should not adjust your pet's routine based on your friend's sad circumstances unless your pet is closely tied to hers. In Virginia, the danger of contracting heartworm disease is extremely high. Every year, between 4,000 and 6,000 canines in our state are diagnosed with the condition.
Intestinal parasites, which infect as many as one in every three dogs and pose a serious threat to human health, are also reduced by the preventatives. Almost every dog in Virginia should receive a dose monthly.
Every year, we see an increase in Lyme disease cases. I've seen a lot more dogs get Lyme illness and even die from it than I've seen IMHA.
Clevengers Corner Veterinary Care in Amissville is owned by Dr. Michael J. Watts.