Mosquito and heartworm checklist from my cousin's dog

I have no pet myself but my cousin asked me to watch her Pomeranian while she was in Japan for 2 weeks. Before she left we took the dog to the vet for a check up, and I learned about heartworm from that visit. I didn't know mosquito is the cause. I always thought only village dogs get it. The vet said the blood test is once a year and the medicine is monthly. Some dogs need it all year round, not only in rainy season, because mosquito is still around in Bangkok even in winter. Her dog Pancake is small so the dose is important, the vet checks her weight again every visit. What we did at her condo: we checked the balcony first. There was a plant saucer with water and the aircon drain tray had dirt and a little standing water, so we cleaned it. Then we put a mosquito screen on the balcony door. The juristic office checks the common drain every month which is good, but the water in the roof tank and the old tyres in the parking lot is not their job, so check your own corner. Also the cat. If you have a cat, the medicine is different. Very different. Do not use dog medicine on a cat, ask the vet before you buy online. My cousin almost did that once. I am not a vet so please ask your vet first. I just wanted to share because I was surprised how easy it is to forget.