Of all the parasites that can affect cats, you are almost certain to encounter fleas and worms at some point. Most cat owners will have to treat for both of these repeatedly, and at regular intervals. The makers of the most effective and well-known medications for cat worms and fleas recommend that they are used at least every three months and, if necessary, every month. This is because reinfection can occur comparatively quickly after having the parasites eradicated from your cat. Worms symptoms are typically diverse, and differ according to the specific parasite.
One of the things you need to bear in mind is that fleas and certain types of worms (namely tapeworms) go together. If you treat for one but not the other, you are likely to see the first condition back again soon.
The reason for this is fairly unpleasant but it's worth understanding to give you some insight into the importance of eradicating both fleas and tapeworm simultaneously - or, at least, within short succession of each other. In order to be transmitted from cat to cat, tapeworms need an intermediate host: one capable of hopping from cat to cat and enabling the tapeworm to spread to their new primary host.
The infected cat passes tapeworm eggs in its faeces. These are then eaten by the larvae of fleas. The egg hatches inside the flea, which grows to adulthood. By this time it will have taken up residence on a new cat. In the course of grooming, the cat will swallow the flea; the flea's body is broken down in the cat's digestive system, releasing the young tapeworm, which latches onto the cat's intestinal wall and grows into an adult tapeworm. As it does so, it absorbs nutrients from the cat. Usually, tapeworms are not too dangerous to the animal, but a serious case will weaken it - especially in a young cat. Worms symptoms include lethargy (more than usual), changes in appetite, and general signs of poor health like a dull coat or weeping eyes.
Tapeworms have segmented bodies, and each segment contains more eggs. These break off and are passed by your cat. You may notice them where your cat sleeps - they look a little like rice husks. These are eaten by fleas, and the cycle continues.
This is why it is important to treat for fleas as well as worms. Most medications will kill a wide range of worms, though some only attack a limited range of species. Choose one that is broad, and find a good flea treatment at the same time!
