Welcome to Yorkietalk & Nevada
I think Pahrump is simular to Vegas as far as humidity levels & mosquitoes. It gets alittle colder in Pahrump though, and snows more. You are in a valley with mountains around you, just like Vegas. Pahrump elevations ranges 2550 to 2750 ft above sea level & Vegas elevations is around 2030 ft or so
I know what you mean, I was in Florida for a short time in 1995 and I had to use Off spray before I could take the dogs out to potty - LOL. It was bad. The pups I had then (in FL) were on all the necessary medications to keep them safe. It won't hurt your pup being on heartworm meds, like your vet said.
I have one yorkie & one mixed yorkie/doxie. What is your pup mixed with?