Pet Health with Helen Woodward Animal Center: Heartworm disease, facts and fiction

SAN DIEGO (KUSI) – In San Diego most people do not have a problem with mosquitoes and heartworm is not a common disease but there are important reasons your veterinarian recommends heartworm testing on your dog, according to Dr. Patricia Carter with Helen Woodward Animal Center.

Heartworms can only be spread by mosquitoes; a recent San Diego news article reported the presence of new mosquito species in our County. The humidity and heat are helping them to exist here.
In today’s world we live in a very mobile society, it is easy for any dog to come from an area where heartworm disease is prevalent and end up in your dog’s neighborhood. If you live by a natural area with free standing water, or there are water features or pools in your neighborhood that are not maintained, mosquitoes can start to breed. If an infected dog and mosquitoes are in the same area then all other uninfected dogs are at risk.
All wild and domestic canids, or dog relatives, are susceptible to heartworms. However dogs outdoors all the time are 5 times more likely to be infected. Cats can also be infected with heartworms. This is called an aberrant host and is very rare especially here in San Diego where mosquitoes are not as prevalent. Heartworm infestations in mosquitoes have been found throughout the United States but the incidence of disease transmission to dogs is highest in the southern United States, on the Eastern Seaboard, along the Mississippi river and its tributaries. Heartworm disease is found in Mexico and is endemic in Japan, Australia and some Mediterranean countries.
A blood sample is needed to check for heartworm disease. Fecals only check for parasites in the GI system. Adult heartworms live in the blood vessels of the heart and lungs. The important thing to know here is that once a dog is infected by heartworm it will take 6 months for the juvenile stage injected by the mosquito to develop into an adult heartworm that now resides in the heart and veins. Testing a dog prior to the age of 6 months will always be negative. If your dog was exposed to mosquitoes and acquired an infection it will take a minimum of 6 months before any test will be positive. So a negative test does not ensure that your dog is truly negative. However the dog is negative for the stage of heartworm that causes the problems to the heart.

Length of coat or staying indoors is not a preventative as mosquitoes can get into the house.
A blood transfusion will not give your dog heartworm disease; the life cycle has to go through the mosquito before it can be infectious to a dog.
A dog with heartworm disease cannot be on preventative. They can and it is recommended that they be on preventative prior to receiving the treatment to kill the adult heartworms.

Ideally every dog should be tested for heartworms annual. Even if your dog is on heartworm preventative every month it should still be tested once a year. The reason is to ensure that no infection slipped through from maybe vomiting up a dose that you were not aware of etc. It also helps to track if heartworm disease is becoming more prevalent in our area.
Heartworm preventative is once a month, it does not stay in the dogs system for a month. It works by killing any new infection acquired in the previous 6 weeks with a pulse of medication that is out of the system within 24 hours.
If you travel, go camping, hiking etc. with your dog or you live in an area with mosquitos then it is best to leave them on preventative year round.
Certain breeds like Collies. Shelties, Australian Shepherds may be more sensitive to preventatives that contain ivermectin and will need to be on preventative with selemectin or other but even for most dogs of the above mentioned breeds they can use ivermectin since the preventative dose is so small but they should be watched over several hours the first time they are using a new product.


Categories: Good Morning San Diego, Health