jackiesdaisy1935,
I would trust your vet and ask
him or her, if your area in Calif. has a Heartworm problem. Also depends if you travel outside of your area with your pets.
Heartworm can be life threatening.
I do not like to medicate my pets unless necessary. I do not live in
a Heartworm area, but I travel with my dogs and put them on a Heart Guard Plus 4-5 months out of the year. They are also tested yearly for Heartworm.
There is a fairly new product called Revolution you can get through
vets. It not only treats Heartworm, but fleas and ticks as well etc.
I am waiting a couple more years
for more data to come out on this
product.

Fleas: My vet likes Advantage and Frontline.
I use Frontline for my dogs.
The bio-spot broke off parts of my
female Akita's fur.