Some of the most popular pets in Hong Kong have been banned from flying Cathay Pacific.

From Monday flat-faced or snub-nosed dogs and cats -- or, to give them their scientific name, brachycephalic animals -- will not be allowed on board by the city's flagship airline amid fears for their health.

A message on Cathay's website yesterday said the animals "will not be accepted for carriage as check-in baggage".

Until now, pets were transported in temperature-controlled cargo areas of the plane.

The ban includes canine breeds such as Boston terriers, boxers, chow chows, shih tzus, and their feline counterparts such as Persians. The breeds typically have very small nasal openings, causing respiratory problems.

They are also very sensitive to heat and at a high risk of suffering heatstroke. The airline says transporting them can have a "negative health impact".

Stanley Browning, veterinarian at Sha Tin Animal Clinic, said if the temperature becomes too hot, tissues in the throat swell and prevent the dog from breathing properly.

"If the ventilation is not good, or if it is too hot, they may die," Browning said, adding that the chances of it happening were slim unless conditions were really poor.

According to the vet, brachycephalic dogs make up the majority of Hong Kong's dog population.

Cathay's move was made in view of the "increased concern in the industry", according to Elin Wong, corporate communications manager at Cathay Pacific.

British Airways announced a ban on carrying brachycephalic animals in 2009. Cathay Pacific did not specify any alternative solution for owners wanting to transport their pets.