Chelonians, which include tortoises, turtles and terrapins, are popular pets in Hong Kong yet are often misunderstood, according to veterinarian David Gething, of Creature Comforts (www.creaturecomforts.com.hk).

"Chelonians are similar in appearance but have some fundamental differences, so it is vital to do the research to ensure that you understand each species' requirements," says Gething.

Turtles, for example, spend their entire lives in water, coming onto land only to lay their eggs. Tortoises are generally land-dwelling and many can't swim. Terrapins split their lives between land and water.

"The most important step in keeping a chelonian happy is to provide the right environment," Gething says.

Habitats vary widely, from dry and arid for species such as the star tortoise or African spurred tortoise - the most common dry-land species in pet shops - to an enclosure requiring both land and water for species such as the red-eared slider - the most common terrapin found in pet shops - to strictly aquatic environments for species such as the pig-nosed turtle.

More than half of the medical conditions Gething sees in pet chelonians are related to their habitat. The second most common cause of illness is incorrect diet. As with habitats and enclosures, dietary requirements vary widely between species, too. Most dry land-dwelling tortoises are vegetarian and feeding them a diet with little fibre, or the wrong type of vegetable and fruit, will result in intestinal disturbances and a nutritional imbalance.

"Terrapins and turtles are often omnivorous and should be fed a mixture of vegetables, fruits, fish and meat."

The diet for all chelonians, Gething says, should include breed-specific tortoise pellets and a mineral and vitamin supplement powder.

Even with the best care and nutrition, however, there are a number of conditions to watch out for.

"The most common diseases we see with pet chelonians are respiratory disease, shell rot, vitamin A deficiency and metabolic bone disease."

Respiratory diseases are common but the symptoms may be subtle. A runny nose, open-mouth breathing, eye infections, heavy breathing or lack of appetite are common signs.

"If a tortoise or terrapin stops eating, is lethargic or seems unwell, it may indicate a respiratory illness. Treatment generally [involves] a course of antibiotics, and, in some cases, injections."

Unhygienic or inappropriate surroundings are a common cause of respiratory infections, so the best prevention is good care.

Shell rot can either be dry (usually a fungal infection) or wet (a bacterial infection).

"Shell rot often starts with an injury, but in some cases can be due to an overly humid environment," Gething says.

The shell may appear cracked, damaged and may even bleed. A twice-daily application of an iodine solution and oral antibiotics should take care of the problem.

Vitamin A deficiency is also a common issue in Hong Kong, as a result of pets spending long hours indoors and being fed a single-ingredient diet. Signs of deficiency include swollen, inflamed eyes that, in severe cases, can result in blindness. Dietary changes and injections can restore the vitamin balance.

Metabolic bone disease occurs when a tortoise or terrapin develops bone weakness and osteoporosis.

"Metabolic bone disease is generally due to a nutritional deficiency, but there are a number of other factors," Gething says.

Tortoises and terrapins need regular exposure to ultraviolet light, such as sunlight or reptile-specific fluorescent lighting, to produce vitamin D3, which is vital for bone growth and development. They also require adequate calcium in the diet. Common signs of the diseases include a weak, flexible shell, swollen jaw, and pathological leg fractures.

"The condition can be treated by improving enclosure lighting or allowing the tortoise to bask in sunlight for a couple of hours per day, in addition to supplementing the diet with calcium."

If an owner suspects that their pet chelonian is not in tip-top shape, they should seek the advice of a vet. These health issues are easy to treat if they are caught early. 

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