PET charity PDSA has reported a significant rise in the number of pets exposed to harmful parasites this summer.

Its latest animal wellbeing report showed a decline since 2014 of 900,000 cats and dogs receiving preventative medication to protect them from blood-sucking fleas. It means nearly four million pets have been left at risk of infestation.

Meanwhile, milder winters and widespread central heating have provided the ideal conditions for the UK flea population to increase in recent years.

But the PDSA warns an infestation can be deadly in very young pets.

Vet Rebecca Ashman said: “A flea infestation can cause intense suffering for a pet. Their skin will become itchy and inflamed, and some pets will scratch so much that their skin becomes sore and infected. For some, such as young kittens and puppies it can be incredibly serious.

“High infestations of fleas can cause a condition called flea anaemia. This is where the parasites have drained so much blood that they leave the animal desperately weak. In younger and smaller pets this can quickly become life threatening.”

She added it was important for owners to carry out a regular flea treatment regime as recommended by their vet.

“It’s worrying that there’s been such an increase in the number of pets that have never received flea treatments. Even if your pets don’t go outside, flea eggs and larvae can still be brought into the home on clothing and shoes.”