adam ,The problem is that Sentinel only reduces the number of fleas. New fleas introduced from outside are not killed. They ingest Lufenuron when they feed on the dog’s blood, and their eggs are subsequently sterile. Over time the population dynamics come into play. However, most people do not want fleas. Period.
Your question depends entirely on location. Where I am located, heartworm is a very minor problem. Close to 90% of the population I see is not on a heartworm product, yet the only cases I’ve seen have been in pets that have been taken to other areas. The eastern part of Pennsylvania is pretty bad for heartworm, yet Western PA is not.
The same is true with ticks and tick-borne disease. In my area most people have never seen a tick. Erlichiosis and RMSF are very rare here. There have been changes the past few years and that is changing, however. It also matters what pets you have. IME Advantix is not a good product to apply to your dog if there is a cat ion the same household.
Generally, a heartworm product (Ivermectin or Milbemycin) along with a flea/tick product is great.
As an aside, many heartworm products are formulated so that the tablet cannot be divided and still give accurate dosage. If you take the product for a 100 pound dog and quarter the tab to treat four 5 pound dogs, there is not an equal amount of drug in each quarter.
