stray dogs, mosquitoes and heartworm, what I learned in Koh Kaew

I have no dog, but I feed the group of strays near my apartment in Koh Kaew every night, and they get bitten all the time. A local lady who helps them told me about heartworm, which I did not know before. She says the dogs in the area often get it because of the mosquitoes around the water. Heartworm is very serious and treatment is hard, so preventive medicine is the better option. The rescue people do a cheap test for the dogs they catch. I started buying a repellent for the strays, but she told me to be careful with the spray, because not all of them are safe for dogs. So now I just clean up the standing water near my building and cover the bins. Simple things. If you have a stray near you, call a rescue group first before you feed it too much.