When to test for intestinal parasites
The only time we would run a fecal is when a dog has diarrhea, we're very fair with our clients and do not want to waste their money on tests that have a high chance of a negative result especially when our dewormers take out the most common parasites we see.
What dewormer to use
This is very much dependent on your location as risks of parasites will vary from country to country or province to province (state in your case).
In Ottawa we have risk of heartworm disease and lyme disease so all of our dewormers need to focus on heartworm and should be bundled with a flea & tick product.
- Flea & tick prevention to be given from March until December
- Heartworm prevention to be given from June until November
We pair up Interceptor (heartworm, roundworm, hookworm, whipworm) with Advantix (Fleas, ticks, black flies, mosquitoes etc.).
If you are not concerned about ticks Advantage Multi (fleas, heartworm, roundworm, hookworm, whipworm, mange) would be a great choice.
Bayer recommends us to use Advantix + Advantage multi but we feel like it's way too much liquid to put on a pet and it's a bit of an overkill.
San Diego I'm not overly familiar with what parasites you have there so call up your local vet and ask them what bugs you have in the area and how many months of the year should you treat for, they shouldn't charge you for asking a question.
In US states that are always hot, flea treatment is a must for 12 months of the year.
In some US states you can pick up some over the counter fenbendazole at farm animal pharmacies without a prescription. I suspect this only applies to states that are known for farming. This will cover your roundworms, whipworms, hookworms, giardia and some tapeworms.
What to stay away from
Anything by Hartz, their products kill pets - most over the counter pet store dewormers aren't 100% effective.
If heartworm disease is prevalent in your area and your dog has not been consistently protected from it it is HIGHLY recommended to test your dog for heartworm disease BEFORE giving heartworm medication. Killing an infestation can cause death to your pet - this should be done under veterinary supervision and guidance.
At the end of the day your most reliable medications for deworming are provided to you by your DVM, if diarrhea is present a fecal test should be ran to rule out less common protozoa such as giardia and coccidia as treatment will be different.