Cases of a killer parasite that enters the lungs of dogs, causing weight loss, breathing difficulties and chronic coughing, are on the rise, according to a new warning issued by an animal charity.

The number of dogs affected by lungworm, which is spread by slugs and snails have rocketed by 35% in just five years, according to PDSA.

The vet charity warned this could be just the tip of the iceberg as many cases of lungworm go unreported.

Comparing data for 2009 and 2014, PDSA vets found there had been a 35% increase in confirmed cases of the worm across its 51 UK pet hospitals.

PDSA Vet Vicki Larkham-Jones said: “There has been a significant increase in the number of confirmed cases of lungworm at our pet hospitals.”

In 2009 there were 49 confirmed cases and this had risen to 66 cases in 2014. However, the true figure is likely to be much higher, as not all infected animals can be positively diagnosed.

The hot spots for cases used to be Wales and southern England, but experts say the problem is now far more widespread.

Vicki added: “The larvae of the lungworm parasite are carried by slugs and snails. The problem arises when dogs eat these common garden pests when rummaging through undergrowth, eating grass, drinking from puddles or outdoor water bowls, or pick them up from their toys.

“Thanks to funding support from players of People’s Postcode Lottery we’ll be delivering over 100,000 worming treatments in 12 months. We’re also able to educate more owners about the dangers and the importance of good, preventive healthcare.”

Foxes can become infected with lungworm, and have been implicated in the spread of the parasite across the country. A recent study by University of Bristol scientists found that in some areas, up to 50% of foxes are infected with lungworm. Frogs can also carry the lungworm larvae, presenting a risk to dogs.

Case study

Staffordshire bull terrier Chloe’s lungworm ordeal highlights how serious the parasite can be.

The beloved five-year-old pet was taken to PDSA’s Bristol Pet Hospital in June by owner Dennis Williams after suffering a severe cough.

Vets examined her and prescribed lungworm medication as a precaution. However, despite initially responding well to treatment, the symptoms returned.

Further tests confirmed the presence of the parasite and vets decided to carry out more aggressive treatment.

PDSA Vet Bekki Pacini said: “It’s good that we saw Chloe when we did, as these infections can be very serious, even fatal. Lungworm can often be difficult to get rid of and despite treatment it can take up to six months in some cases for a dog to recover.

“Chloe has responded well to treatment, but several months on she is still displaying some symptoms. We’re confident that with continued treatment she will go on to make a full recovery.

“This case highlights the importance of regularly worming your dog with a product that specifically targets lungworm because this parasite is becoming a more serious problem across the UK.”

Mr Williams, 47, of Withywood, Bristol, said he had never even heard of lungworm prior to his dog becoming infected.

He said: “Chloe loves playing in the garden and I understand it could have been something as minor as her nuzzling her nose in the grass or playing with a toy where a slug or snail had been for her to contract the lungworm.

“I’m grateful to PDSA for the treatment they’ve given Chloe and I want to help raise awareness of how serious it can be, because people just don’t know. I’ve owned dogs for 30 odd years and I’d never even heard of it.”