There are currently four types of cat heartworm medicine designed to ensure our pets do not become infected with this dreaded parasite. Two are 'spot on' or topical treatments while the other two are given orally.

You may wish to combine a treatment to prevent heartworm with other parasite controls too. Choosing such a multi-faceted product means you need to have less pet medicines around the home, and less to remember to administer. But, of course, extra protection means extra expense so you will need to decide what parasites are actually a threat to your cat. Lifestyle and location are the primary factors in determining which pests are likely to be a problem for you and your pets.

Another deciding factor in which medicine you choose will be how happy your feline friend is to accept oral treatments. Now that products come in chewable treat form, many cats will accept oral medicines much more easily than before.

So, what are the options available to cat-owners? The four methods of preventing heartworm in cats are:

• Ivermectin given as a monthly chewable, oral treatment.
• Milbemycin oxime as a monthly oral treatment.
• Selamectin given as a monthly topical treatment.
• Imidacloprid and Moxidectin given as a monthly topical treatment.

Firstly, Ivermectin is the most widely used active ingredient used in the treatment of animals already infected with heartworm disease. This means it is a drug which comes under regular scrutiny when used in much larger doses than your cat will receive with its preventative medicine. As well as destroying larval worms in your pets bloodstream this drug will destroy roundworm and hookworm in its gut too. This makes it a good all round de-worming product. At the moment ivermectin is available as the branded product Heartguard from Merial.

The second option for oral heartworm meds is Milbemycin oxime which is branded as Interceptor. It does exactly the same job as the ivemectin based product, eliminating larval heartworms, roundworm and hookworm which have occurred during the thirty days since your pets last treatment.

There is very little to choose from in these two orally administered products, particularly as the price for both is usually about the same. Heartguard has a slight advantage in that ivermectin is shown to destroy larval worms which have been in the system for longer than a month so if you mistime a treatment there is less chance of a problem. But, that effectiveness falls the longer the period between treatments so should never be relied upon to stop your pet contracting heartworm disease.

For a wider spectrum of parasite control the topical treatments are definitely the better option. Side effects are few and far between, and generally confined to a tiny patch of hair loss which really is nothing to worry about, but may indicate that oral treatments are better in future. The topical treatments are administered by pouring an small quantity of oily liquid onto the skin of your pets shoulder blades. The skin should be parted to ensure the skin can absorb it fully. The active ingredients are then sent into the bloodstream to deal with internal parasites, and are also spread via the sebaceous glands to coat the entire body to deal with external parasites.

The first oral heartworm medicine is Selemectin which is branded as Revolution. This is really a complete answer to parasite control as it protects against fleas, mange, ear-mites, heartworm, roundworm and hookworm too. This means one product will deal with all the parasites your cat is likely to come into regular contact with. This medicine is thought to be safe for use on pregnant and lactating cats which makes it the only option for such animals.

Advantage is the final option for cat owners, using Imidacloprid and Moxidectin to destroy flea infestations, ear-mites, heartworm, roundworm and hookworm. Like most medicines this is not proven to be safe for use on pregnant or lactating animals.

If your concern is purely internal parasites the oral treatments are best and cheapest, but if you prefer the convenience of incorporating your cats flea treatment opt for a topical heartworm medicine.

All the options have an extremely good safety record as the amount of active ingredient is so tiny. But, as with any pet meds you should keep an eye on your pet following administering the drugs to ensure they do not show any sign of allergy. Ensure you use the correct dosage as different size cats may need to receive different amounts of the treatment and never use products not specifically confirmed as for use on cats. Which ever option you choose ensure your cat is tested for the disease prior to commencing treatment. Using any pet medicine on poorly, underweight, aged, nursing or pregnant animals should be discussed fully with your vet first, though Revolution topical treatment is considered safe for nursing and pregnant queens.