China's top wildlife experts on Tuesday called for more measures to prevent and control the spread of disease among giant pandas, after a rise this year in the number dying from abnormal or unknown causes.

Globally, 13 pandas died in captivity this year, compared with four in 2011.

"This figure, however, does not include deaths of newborn cubs," said Zhang Zhihe, director of the Chengdu Research Base of Giant Panda Breeding in Southwest China's Sichuan province. He added: "The survival rate of newborn cubs has also dropped this year."

Two cubs born prematurely died at the base, while another two died at a research institute in Shaanxi province.

Experts met in Chengdu, the provincial capital, on Tuesday for the start of a two-day annual conference of the Chinese Committee of Breeding Techniques for Giant Pandas.

Zhang Hemin, director of the China Conservation and Research Center for the Giant Panda, said that like humans, pandas can suffer many diseases, and known causes of death for adult pandas include cardiovascular tumors and cerebral hemorrhages.

"It's good we know these causes," he said. "We have more captive pandas and can therefore find more diseases."

When the committee was set up in 1989, there were just 92 pandas living in captivity worldwide. Today, there are 341, and many of the problems they face, including difficulty to conceive and for cubs to survive, have largely been solved.

However, as captive pandas are kept mainly at the China Conservation and Research Center for the Giant Panda, the Chengdu base, or the Louguantai Center for the Rescue and Breeding of Wild Animals in Shaanxi province, the rise in population density has resulted in a higher risk of infectious diseases.

Pu Anning, director of the general office at the Chengdu breeding base, said: "If a panda catches flu, other pandas fall victim, too."

To cope with the situation, the base has built the Dujiangyan Field Research Center in the foothills of Zhaogong Mountain, where six giant pandas were settled in January.

The base signed an agreement late last month with Changning county in Sichuan to build a new habitat at a bamboo forest in the county, where the Oscar-winning film Crouching Tiger, Hidden Dragon was partly filmed.

Covering 291 hectares, the habitat, to be named Panda World, will comprise 74 hectares of forest, a lake and 58 types of bamboo.

Zhang Zhihe said when the area is completed, it will have 10 pandas.

The China Conservation and Research Center for the Giant Panda at the Wolong Nature Reserve, also in Sichuan, has expanded its panda habitat, increasing the capacity of its dens from housing 20 pandas to 65 since the 2008 Wenchuan earthquake.

Captive pandas also face an increasing threat of infection from the increased contact they have with humans.

Zhang Zhihe said: "Disease prevention, control and treatment for pandas has much room for improvement, especially known conditions like canine distemper."

Canine distemper, which can kill dogs and other members of the canine family, can also infect pandas. It is difficult to cure, and strenuous preventive efforts are being made.

Several institutions housing pandas, in China and abroad, have used vaccines from a distemper gene produced in the United States.

"Results so far show it's a safe and effective vaccine," Zhang Zhihe said. "But it's very difficult to import vaccines from abroad, as they are biological products, and the Chinese government has control over them. Authorities need to do more to assist us to solve the problem."

Due to greater efficiency in panda breeding, the number of overseas panda exhibitions has increased. But at some overseas zoos, pandas suffer from health problems, with experts saying more care is needed when selecting zoos for "panda diplomacy" projects.

In 2010, Xingxing, a 14-year-old male from Wolong Nature Reserve, died at Oji Zoo in Kobe, Japan, after he was given an anesthetic so keepers could collect sperm.

A week-old cub died of pneumonia at Tokyo Zoo in July, while in September a cub of similar age born at the US National Zoo in Washington DC died of liver disease.

Contact the writer at huangzhiling@chinadaily.com.cn