If I could just add something to what Dr. Geller wrote - even if you never see a raccoon in your area, leptospirosis can be picked up if your dog wades into a local pond or a shallow creek where wild animals may go for water. If they urinate or defecate at the water's edge and their waste ends up in the water, if your dog drinks the water or even wades in it and then licks his paws he could contract lepto. Even after a heavy rain that leaves large puddles around, you just never know what has been drinking (and relieving itself) in or near those puddles. I just didn't want anyone to make the mistake of thinking that their dog couldn't be exposed to lepto just because they've never actually seen a raccoon or other possible host animal in their area.
Ghilly
1. It sounds like Caesar experienced some "dietary indiscretion", but now things have somewhat normalized thanks to some medication prescribed by your veterinarian and a consistent diet. It is probably very important not to offer him anymore bones or human food in the future. One of the most beneficial treats you could give him is a prescription rawhide chew that is treated with an enzyme that helps maintain dental hygiene. The problem of dogs eating their own, or other dogs', stool is fairly common, and most dogs outgrow it. In the meantime, you must deny him access to his stool by cleaning it up immediately. There are no dietary supplements that have been shown to prevent this problem.
2. Most dog owners cut their dog's nails too short, possibly hitting the "quick" and making future nail trims a rodeo of sorts. Nails should be trimmed even with the bottom of the foot pads. To help maintain nail health, consider giving Caesar some biotin, a dietary supplement.
3. Give him the Interceptor, even if it is late, and make sure he is tested for heartworms next Spring. If you live in an area where there have been Leptospirosis cases, he should be vaccinated for Lepto as well as Rabies and the core vaccines, DA2PPV. A recent published study summarized the number and location of cases of Leptospirosis across the country, so your veterinarian should be able to confirm if it is a risk in your area. Dogs catch Leptospirosis mostly from contact with recently urbanized animals such as racoons, not other dogs.
Some veterinarians are vaccinating dogs less frequently as they get older, so you should discuss that possibility with your veterinarian. As a younger dog, Caesar should probably be fully vaccinated now, and then possibly you can rotate some of the vaccinations in future years. Rabies is a legal requirement in most areas, and only needs to be given every three years once a dog has reached one year of age.
Good luck!
Jon Geller, DVM