GEORGE TOWN: Two species of the deadly box jellyfish, previously not thought to exist here, are breeding in the sea around Penang.

Their venom causes Irukandji Syndrome, which includes severe hypertension, extreme lower back pain, nausea, vomiting, intense cramps, breathing difficulty and heart failure.

While not as lethal as the Australian Box Jellyfish (Chironex fleckeri), which can kill an adult human in three minutes, they are still life-threatening to young children, the elderly and the frail, said marine biologist Sim Yee Kwang.

He said the current population density of the two species – Chirop­soides buitendijki and Mor­bakka sp. – in Penang is two in every square kilometre of the sea up to 400m from the shoreline.

“As passive swimmers, they will move closer to shore during the neap tide when sea currents are weak. That is the most dangerous time for swimmers,” he said.

Sim, who is a scientist in the Cen­tre for Marine and Coastal Studies (Cemacs) under Universiti Sains Malay­sia, has been combing the coastline of Teluk Bahang, Batu Ferringhi, Tanjung Bungah, Tanjung Tokong on the island and Pantai Bersih in Butterworth every two weeks since July to catch jellyfish.

The largest box jellyfish was caught 200m from the shore of Pantai Bersih in Butterworth, measuring 18cm from end to end of its cube-shaped body.

Cemacs director Prof Datuk Dr Aileen Tan said box jellyfish were not thought to be in Penang.

“These are invasive species. Most likely, their larvae were carried to our waters in the ballasts of cargo ships,” she said.

She said unpredictable weather that significantly changed the sea’s temperature and salinity may trigger a bloom of the deadly jellyfish around Penang and also throughout the Strait of Malacca.

She said it is vital to develop a reporting mechanism of jellyfish sting victims in hospitals soon.

“We need to track cases of Iru­kandji Syndrome in hospitals to troubleshoot and monitor the spread of box jellyfish,” Dr Tan said.

She added that five years ago, she interviewed a fish farmer who was stung by a jellyfish while cleaning his open sea fish farm cages.

“He told us that in five minutes, he had difficulty breathing and was warded for several days.

“We suspected it was Irukandji Syndrome but did not have the data to confirm it,” Dr Tan said.

In February, a 12-year-old boy swimming in Teluk Bahang was stung by a jellyfish and went into a coma for three days.