Just because we're entering into the Autumn season does not mean that dog owners can slack off about giving heartworm preventative. On my website, under Recommended Vaccinations & Wormers, I have advice from Dr. Jean Dodds, Hemopet. 

She advises using heartworm preventatives for healthy dogs if the ambient temperature is above 57 degrees Fahrenheit (14 degrees Centigrade) for approximately two weeks and mosquitoes are prevalent. A basic rule of thumb is Mid-April through November for the majority of the country and basically year-round for the southern states.

However, we are experiencing climate change worldwide. Therefore, it would be wise for those living in the four-seasons regions to keep dosing with heartworm preventative through December just to be safe. This past late Autumn into early winter, I recall mowing my pastures despite the calendar being the end of December! At the same time, be prepared to begin dosing earlier than April if there is a much warmer than usual forecast. Still, first, you must have a heartworm blood test performed. I prefer Snap 4DX tests, which also screen for  Anaplasma, Ehrlichia, and Lyme tick diseases.

The most important tip for everyone to know when dispensing heartworm preventatives is that the dog MUST chew the tablet. Since many heartworm preventatives are in chewables forms, people get complacent and think that when they give it to their dog, they'll munch on it. But, if your dogs are like mine, they simply swallow it without chewing. So my policy is to GRIND the pills into tiny pieces or even a powder in a small bowl and add it to a small handful of ground meat. Then I administer it to each of the hounds. This method guarantees that the pill has been crushed without chewing! 

Why the big deal? Because pharmaceutical companies require dogs to chew and NOT to swallow their preventative whole for the effectiveness of the pill. Many, many dog owners are completely unaware of this issue. Over the years, I have heard stories about dogs diagnosed with the disease despite taking monthly preventatives. The owners contacted the company and were informed that, most likely, their dog never chewed the pill! That is not what you want to hear after the fact. 

Lastly, I urge you to use heartworm preventative medicines. But choose carefully, as there are several options on the market with varying degrees of side effects for specific breeds. For example, some Herding Breed dogs have a genetic mutation that makes them dangerously oversensitive to ivermectin, as well as white colored-dogs, and dogs prone to seizures. Additionally, Sighthounds are very sensitive and are best suited with plain milbemycin oxime. I discuss heartworm preventatives and wormers in detail on my website, so please take a moment and visit Recommended Vaccinations & Wormers.