Worms and your dog

Are there different sorts of worms?
Broadly there are two types of worms that cause problems in the dog: nematodes (roundworms) and cestodes (tapeworms). Common nematodes are Toxocara canis (intestinal roundworm) and Angiostrongylus vasorum, the lung worm. Important cestode parasites include Dipylidium caninum, Taenia species and Echinococcus species. Hookworms (Ancylostoma species) are also occasionally encountered.

Are these parasitic infestations serious in the dog?
In adult dogs intestinal worms – both roundworms and tapeworms – are usually not life-threatening, except in seriously debilitated dogs or those that are immunocompromised.

Heartworm disease

This is a condition is not found in Ireland but which is increasingly being diagnosed in Great Britain probably as a result of the relaxation of quarantine restrictions allowing British dogs to travel to areas such as southern Europe and certain parts of the USA (e.g. Florida) where the causal organism, Dirofilaria immitis, is prevalent. Heartworm disease is considered to be one of the most important conditions seen in small animal practice in the United States. Transmission depends upon mosquito types only recently found in parts of Britain, possibly associated with milder conditions.


No intermediate host is required.
Nematodes (roundworms) are free living in the bowel. In puppies they can present problems if not controlled. In large numbers they can stunt growth, cause serious digestive upsets and result in a lot of gas formation. This results in a typical ‘pot bellied’ appearance. Roundworms can be spread directly from dog to dog via infective eggs.
These eggs can also prove a health risk to people, especially children, and in rare cases can cause damage to the eye.


An intermediate host is required.

Dipylidium caninum is the common tapeworm of the dog . It causes few problems in the adult host but in the growing puppy can result in digestive upsets and stunting. Diplydium is spread by the flea as intermediate host and effective treatment for this parasite involves an effective wormer, and effective flea control medication and also must include environmental flea control to prevent re-infestation.

Echinococcus spp, another type of tapeworm, are important because they may be zoonotic, i.e. people can be infected. Currently the zoonotic forms are thought not to occur in Ireland but do pose a significant health risk in parts of continental Europe. This is the reason that pets travelling from abroad need to be treated for tapeworms shortly before they are allowed to enter the UK or Ireland. Dogs are infected by eating an infected intermediate host (sometimes small rodents or uncooked offal from sheep). Control measures involving regular deworming of the dog together with avoidance of feeding raw or under-cooked offal.

Tapeworms found in adult dogs usually cause few problems. However occasionally puppies are infested and depending on the type of worm involved, their sheer volume can cause serious blockages to the bowel.


Hookworms, particularly Ancylostoma spp are one of the most pathogenic parasites of the dog. Although not a major problem in Irish dogs, this tropical hookworm, approximately 1-2 cm (½ to 1 in) long, attaches itself to the lining of the bowel and as a result of blood sucking activities can cause severe anaemia. The infective larvae enter the host either by mouth or through the skin (particularly of the feet). Eczema and secondary bacterial infection can result due to irritation as they burrow through the skin.
As a result of increased foreign travel by British dogs under the Pets Passport Scheme, hookworm disease is being more regularly diagnosed in Britain.


These are a major problem in parts of southern Europe and the United States. They are large worms, adults reaching 16 cm (5½ in). They are chiefly located in the right ventricle of the heart and adjacent blood vessels. As mentioned previously heart worm disease is considered to be one of the most important conditions seen in small animal practice in the United States. .
The period of development to the adult stage is about six months after infection following a bite by a mosquito carrying the infective larvae (microfilariae). The typical signs are fatigue on exercise, coughing and poor condition.

Treatment against worms

Today many effective drugs are available to control worms in the dog. Effective worm control in the dog however involves the choice of an appropriate preparation which has to be regularly repeated. Please contact us and we will be happy to advise and supply a suitable preparation together with appropriate dosing instructions.