The most serious diseases in puppies and kittens aren't contagious between species. For example, parvo, a deadly virus in puppies, can't be transmitted to your kitten. Likewise, feline leukemia can't be transmitted from a sick kitten to a puppy. What puppies and kittens can transfer to each other are parasites.
If your kitten has fleas, you likely have fleas and flea eggs in your house. While the fleas will not be directly contagious from your kitten to your puppy, your puppy will get infested if you don't treat your kitten and house. There are several veterinary products that treat fleas in puppies and kittens such as Advantage, Frontline and Revolution. You should treat both the kitten and the puppy with the product recommended by your veterinarian. Tapeworms, while not contagious from one animal to another, can infect both puppies and kittens and are transmitted by fleas. Tapeworms look like bits of rice in your pet's stool and can be treated with de-worming medications available at pet supply stores or from your veterinarian.
Some types of intestinal parasites are species specific and others can be passed from a kitten to a puppy. Types of intestinal parasites that infect kittens and puppies include roundworms, hookworms and whipworms. These intestinal parasites can be passed when a pet comes in contact with the stool of an infected animal or in contact with soil that has been contaminated. Both kittens and puppies should be on regular de-worming schedules because intestinal parasites are common in young animals of both species.
Ringworm is not a parasite but a fungal infection. It is highly contagious between cats, dogs and humans. Cats are the most common carriers of ringworm, and kittens and puppies are more likely to get infected than older animals. Ringworm infection forms a patch of skin that is red and crusty. There is often hair loss at the infected area and the infected site often forms in a circle. For a definite diagnosis, your veterinarian will do a skin culture. Ringworm can often be treated with over-the-counter anti-fungal medications.
There are different types of ear mites, some of which are species specific and some of which your kitten can pass to your puppy. Signs your kitten has ear mites are a dark-colored discharge from the ears and the kitten pawing at his ears. Some of the veterinary products that prevent flea infestations in dogs and cats will also treat and prevent ear mite infections. If your kitten has ear mites, you should treat both the puppy and the kitten with one of these products. Consult your veterinarian to determine which will be best for your pets.