Dog - Lungworm (Angiostrongylus vasorum)
The bowel is not the only organ that can become infested by canine parasitic worms. Heartworms and lungworms are relatively common in certain parts of the world. For many years Angiostrongylosis, canine lungworm, has been known to exist in the UK but was confined to parts of Wales and Southern England. Over the last few years lungworm infestation in Scotland and parts of Northern England has been reported. It now appears that the problem is widespread across the whole of Britain.
What is lungworm disease?
In both cats and dogs the disease is caused by a small roundworm known as a Metastrongyle. This family of roundworms are all known to live in the lungs themselves or the nearby blood vessels.
Angiostrongylus vasorum, the canine lungworm, lives not in the lung tissue itself but in the associated blood vessels and sometimes in the heart. The resulting signs are little different from those in the cat where the problem is caused by an entirely different worm Aelurostrongylus abstrusus which lives in the lung tissue.
What are the signs?
The difficulty with canine lungworm is that affected dogs may not show any signs at all (i.e. the disease is sub-clinical). With the majority of healthy dogs that become infected the condition runs a chronic course with non-specific, often intermittent signs such as lethargy, weight loss and occasional vomiting. This can sometimes progress to true cardio-respiratory signs such as a cough with difficulty in breathing (dyspnoea) and reduced exercise tolerance.
Other signs include blood clotting problems so that the dog may occasionally cough up blood, or have intermittent nose bleeds, progressing to more serious bleeding tendencies. In some dogs it appears to affect the nervous system so that lethargy, sometimes spinal pain or paralysis, followed by fits may occur.
Angiostrongylus vasorum, the canine lungworm, is usually prevalent in relatively young dogs and therefore these signs may be picked up more readily. The condition has been diagnosed in dogs as young as 10 months of age.
Present position in the UK
Lungworm has been known to be present in the UK for years but appeared to be confined to southern areas of England and Wales. Today it is far more widespread. It is now considered to be endemic for the whole of the south of England and south Wales and there have been reports of incidences in the north west of England. Thus it is reasonable to consider that there is a risk of this condition throughout England and certainly many parts of Wales.
Scotland, until recently, was considered to be free but there have now been some confirmed cases.
Why has this spread occurred?
To understand this we have to consider the life cycle of Angiostrongylus vasorumthe canine lungworm. Adult worms live in the pulmonary (lung) blood vessels or in the heart. They measure up to 2.5 cm (1 inch). They lay eggs which are carried to the smaller blood vessels and capillaries where they hatch into larvae (L1). These immature worms (L1 larvae) break through the vessel walls and enter the lung tissue from which they are coughed up and then swallowed. Ultimately they are passed out in the faeces. The life cycle is then continued when they enter a suitable snail or slug (mollusc) which in turn has to be ingested by a dog for the life cycle to be completed. Maturation of the larvae occurs first in the bowel and then in the pulmonary blood vessels of the dog.
Slugs and snails have become very much more prevalent in Britain as a result of our warmer, wetter weather and it is to this that the now countrywide spread of lungworm is attributed.
Slugs and snails are very common garden pests. The dog does not need to deliberately eat them in order to become infected. Tiny slugs and snails are just as potentially hazardous. These can often be ingested accidentally when the dog eats grass, drinks from puddles or outdoor water bowls. They can also be accidentally swallowed from outdoor toys with which the dog plays. It is also suggested that live larvae can be present in the slime track left by the snail and thus dogs eating such slime covered grass can be infected.
How is it diagnosed?
Today there are specific tests available that can diagnose Angiostrongylosis even if the dog is not showing any signs at all, although the most reliable laboratory test involves detection of larval worms in a faeces sample.
How is it treated?
Routine roundworm remedies may be effective but you should check with us on each occasion. There are very effective treatments for Angiostrongylus vasorum available. These treatments will specifically target lungworm as well as other intestinal parasites both roundworms, tapeworms and sometimes, external parasites, fleas and lice etc.
Some 'spot-on' preparations particularly Advocate (Bayer) are very effective.
Prognosis
Once diagnosed and treated most dogs make a full recovery with no further problems.
However it is important to maintain a regular de-worming programme that is effective for lungworm. It is also important that action is taken early. The difficulty is that some dogs may be infected and be asymptomatic (not showing any signs), this problem can be overcome with routine worming using appropriate products. Please consult us.
It should be remembered that some dogs can be infested if they have been in contact with foxes or their excrement or also rodents or birds that may have been infected by eating infected molluscs.
If you would like to discuss any particular concerns, please feel free to contact us.