A deadly strain of avian-malaria which killed six penguins at London Zoo cannot be contracted by human beings, officials say.

The birds contracted the disease from mosquito bites, despite zookeepers increasing their dosage of anti-malarial medicine at the start of the summer.

Their death in the summer has been put down to this year’s damp muggy conditions, in which mosquitoes tend to thrive.

A spokesman said the current colony is given a daily dose of medicine in tablets with its fish and mosquito traps have been put inside the birds’ enclosure.

Lavender trees have also been planted inside the enclosure and a lavender scent sprayed to ward off mosquitoes.

She added: “The malaria was contracted directly from a mosquito bites and cannot be passed between birds.

“There was no risk to zoo visitors at any point and all of our penguins are in very good health.”