All 27 penguins at Marwell Zoo in Hampshire have died, Edinburgh Zoo has reported the loss of several birds since the beginning of the summer, and Bristol Zoo says eight of its birds have succumbed in the last two months.

Jane O'Brien reports from Bristol Zoo

Penguin experts have linked the deaths to a type of avian malaria which eats into the brain. This leaves the birds weak and leads to a speedy death.

The malaria is spread by native birds such as thrushes and blackbirds. The mosquitoes are thought to have bred in the penguin pool and then infected Marwell's 22 African and five Macaroni penguins.

Bristol has lost eight birds

Some of the birds started to fall ill in early summer but appeared to recover after veterinary treatment. However, the disease took hold again in August and September killing the entire population very rapidly.

It is a big blow to the zoo which only opened its new penguin enclosure in 1997, in the presence of the Princess Royal, Princess Anne.

The disease has also hit Bristol Zoo, which has just opened what it is probably the UK's finest penguin enclosure, built at a cost of over �2M. One bird died in August and another seven died in September.

"It affects the liver, it affects the spleen, and in some cases will affect the brains of the birds as well," says Bristol's Dr Brian Carroll. "It really is quite devastating."

Marwell will restock after taking advice from penguin experts

Experts hope the onset of autumn and the colder weather, which should kill off mosquitoes, will bring an end to the outbreak. However, zoo populations will need constant monitoring over the next few months.

London Zoo, which has 41 penguins, said it had no immediate problems - although it has lost five birds in the past 15 years to the disease. A spokeswoman said it had no plans to take special precautions, "but we will be keeping a very close eye out now".

She also said there were no problems at Chessington Zoo, whose penguins come under the control of the London gardens.

Marwell will be holding a meeting of penguin experts in late October to review the situation. It then plans to restock its Penguin World enclosure.