Why do we recommend testing for heartworm in the spring?

Heartworm disease, although not currently common in Portland, is a deadly disease found in southern Oregon and other parts of the country that people are likely to travel to with their dogs.
The adult heartworms that take up residence in the blood vessels of the heart and lungs start as baby larvae that are transmitted when a mosquito feeds on an infected dog and then goes on to bite another dog. After 6 months of growing through several larval stages, the adult worm produces the antigen that the standard heartworm test screens for. In other words, a heartworm test won’t detect the presence of heartworm until an adult worm is present, which may take as long as 6 months after the last risk of exposure. In most parts of the country, exposure risk is greatest during the warm months of summer and early fall. Unless your dog came from or has travelled to parts of the country that maintain a very warm climate throughout the year (Florida, Louisiana, or Texas, for example) it’s very unlikely they would have been exposed to heartworm since the previous October. This is why spring is the best time of year to test for heartworm.

Why test when, in the past, heartworm has not been a threat in Portland?

We recommend using a heartworm preventative if you are traveling with your dog outside of Portland and may be entering a heartworm endemic area. A handy resource to check your destination for heartworm prevalence is petsandparasites.org. If any doubt, err on the side of prevention.

Confirming a negative heartworm test is essential before embarking on any heartworm preventative strategy.

There is a degree of uncertainty as to why heartworm is rare in Portland and whether it’s a matter of time before it will become a more serious threat. Climate is a likely factor contributing to the difference in heartworm infections between Portland and places like southern Oregon. Unfortunately it seems like our climate is becoming less predictable and the future risk of exposure is likewise less predictable.

There may be certain situatio ns in which using a heartworm preventative during the summer in Portland may be the right choice. This can be discussed at your pet’s annual exam as part of anindividualized wellness plan.

We would be happy to schedule a heartworm test or wellness exam for your dog. Just give us a call.

Wishing you a happy spring!