Health and wellness

Hiking tips: deadly snakes and poisonous plants explained in three new Hong Kong guides to the countryside

Hong Kong has over 50 snake species, most of which are harmless; some, though, are potentially lethal, and it’s often hard to tell them apart. A website has been created to remedy this, along with guides to dangerous local plants

PUBLISHED : Saturday, 11 August, 2018, 2:31pm
UPDATED : Sunday, 12 August, 2018, 7:18pm

In summer and autumn, the delicate yellow flowers of the Gelsemium elegans plant, also known as graceful jesamine, brighten Hong Kong’s countryside. But don’t be fooled by its innocent appearance.

Every part of the plant – root, leaf, flower, fruit and stem – is highly toxic. Eating any part of it can cause failure of the respiratory and central nervous systems, and even death.

In March 2007, an elderly couple discovered its toxic powers when they ate it while collecting plants on Lantau Island. They had mistaken it for the non-poisonous Mussaenda pubescens, a plant from the coffee family known as Buddha’s lamp.

The 69-year-old man developed dizziness while his 65-year-old wife suffered respiratory failure and needed eight days in hospital. The case was outlined in the Hong Kong Journal of Emergency Medicine.

It is an example of the hazards nature – and sometimes traditional Chinese medicine – has in store for the unwary. Snakes are another. Three new guides to identifying poisonous snakes and plants have recently been published to help users of traditional Chinese medicine and visitors to the countryside stay safe.

Hong Kong is geographically small, but big on biodiversity, with 57 species of mammals, 540 bird species, and 86 species of reptiles. It also has more than 3,300 species of plants. Some have medicinal value and are used in traditional Chinese medicine. Others, like graceful jesamine, are poisonous and can cause death.

Each year doctors treat poisoning cases, whether from accidental or intentional exposure to plants. In the past decade the Hospital Authority has reported 30 cases of plant poisoning, a third involving graceful jesamine.

In 2008, a 51-year-old woman was admitted with nausea, vomiting and hepatitis after consuming sticky germander (Teucrium glandulosum), prescribed by a Chinese medicine practitioner for lower back pain. It took two months for her liver function to normalise.

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Mushrooms are a common source of poisoning. Between 2013 and 2016 there were six cases involving powder cap amanita (Amanita atkinsoniana); three patients suffered acute liver failure, while one needed a liver transplant.

To help educate people about what’s toxic and what’s not, the Hospital Authority in April released a digital version of the Atlas of Poisonous Plants in Hong Kong – A Clinical Toxicology Perspective, which lists 117 poisonous plants found in Hong Kong.

The publication took five years to compile, a huge task, says one of the contributors.

“Imagine hunting all over Hong Kong to track down more than 100 poisonous plants, some of which are incredibly rare,” says Tony Mak, chief of service of the department of pathology at Princess Margaret Hospital. His team spent many weekends climbing up hills and wading through streams to photograph plants during the height of their flowering and fruiting stages, he says.

Each plant – and nature lovers will recognise many of them – has clear images, details about which part is poisonous, what happens if you eat it, what role if any it has in traditional Chinese medicine, and local and international poisoning cases involving that plant.

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It’s both a fascinating and frightening read.

Take the air potato (Dioscorea bulbifera), the first plant on the list. Two men in Hong Kong who took “potato mash”, as it’s called, prepared from aerial bulbs of the plant, were poisoned, with one suffering liver damage.

Further down the list, sea mango (Cerbera manghas) catches the eye. If you thought it sounds appetising, you’d be wrong. The whole plant, one familiar to hikers, is poisonous, especially the fruit and seeds. In China and Sri Lanka, it’s used for suicide and murder. Just half a seed is needed for a lethal dose.

The Hospital Authority is not the only body seeking to raise awareness of poisonous plants. The University of Hong Kong’s Ecology & Biodiversity Society has compiled an in-house field guide, Poisonous Plant Field Trip.

Society member Nicole Yu says the book relates to a field trip to The Peak.

“Our members were surprised by the toxicity of many of Hong Kong plants. We hope this helps raise awareness,” she says.

Yu says many plants are misidentified. “Take the Buddha's lamp … It’s not poisonous but is often confused with Gelsemium, which is highly toxic.”

Wanda Huang is well aware how toxic the Hong Kong countryside is.

Huang is a professional forager who spends much of her time scouring the countryside searching for seasonal ingredients to supply the city’s restaurants. She knows Hong Kong plant species like the back of her hand.

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“There are more than 100 toxic plants in Hong Kong, ranging from mildly toxic – with symptoms such as skin irritation, swelling, sores, itchiness, diarrhoea and nausea – to deadly.”

Huang says prevention is the best approach: “Don’t test unknown plants orally and wear long sleeves and pants when foraging.

“There are also many lookalikes. Some poisonous plants give off fumes, so burning them isn’t a good way to dispose of them. … Some common garden and park plants found around Hong Kong, from the mildly poisonous such as the poinsettia (Euphorbia pulcherrima) and hydrangeaceae families to the poisonous apocynaceae family – are also poisonous when ingested by humans and animals.

“One of the most dangerous plants in Hong Kong is the rosary pea (Abrus precatorius) – the seeds contain the poison abrin. Ingestion of a single seed, well chewed, is fatal for adults and children.”

Huang says anyone who comes into contact or has ingested a poisonous plant/mushroom should save any remaining pieces for identifying, remove any portion of the plant from the mouth, and not to induce vomiting as it may cause more damage coming up,” she says, adding the best thing to do is rinse the mouth, or wipe the area clean with a wet cloth, then head to hospital.

Also helping hikers deal with hazards in the hills is a new website, Hong Kong Snake ID.

Launched by wildlife photographers and nature lovers Adam Francis and Robert Ferguson, the site expands on the government’s limited database.

Ferguson, who has spent more than 20 years gathering information on Hong Kong wildlife, says the site was created to meet popular demand.

“So many people were asking me about the differences between venomous and non-venomous snakes. It made sense. There was a lot of conflicting information out there.”

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Hong Kong has 55 species of snakes. Serious health issues can result if a person is bitten by any of seven species commonly seen on land: the bamboo snake, banded krait, many-banded krait, Chinese cobra, king cobra, coral snake and the red-necked keelback. There are two more rarely seen species that can cause a nasty bite – the mountain pit viper and pointed-scale viper.

Unless you are an expert, it is hard to tell whether the one slithering next to you on a hike, or curled up on your terrace, is venomous or not.

The comprehensive guide contains information about what to do if you get bitten by a snake, what to do if you find a snake in your flat, and how to tell a harmless rat snake from a venomous cobra.

It has clear photos taken by Francis and Ferguson, and videos, such as this one taken by Francis on a morning hike:

They plan to have the guide translated into Chinese.