Clinical Zoo: Helping out a gecko with no name

There’s something exciting about exploratory abdominal surgery. Whether you’re in small animal, large animal or exotics practice, you can’t always predict whether the procedure will be routine or whether you will “peek and shriek”, to borrow an increasingly popular phrase being bandied around at veterinary conferences and surgery workshops.

That element of the unknown is increased when dealing with wildlife species which traditionally receive less veterinary intervention – often not until they are at death’s door.

Wildlife species bred in captivity are monitored closely and represent a population for whom veterinary access and intervention are more accessible and potentially more timely. But when things go wrong with a captive-bred animal which just happens to be an endangered species, whose ongoing health and reproductive capacity is vital not only for the individual animal but for the future of their kind, there’s additional pressure to restore the animal to perfect health.
During a locum at Auckland Zoo, veterinarian Anna Le Souef was presented with just such a patient. An adult female Duvaucel’s gecko with a worryingly distended abdomen. Le Souef knows a thing or two about conservation. She completed a PhD through Murdoch University on the development of prognostic indicators for the successful rehabilitation of black cockatoos (Calyptorhynchus spp.)

Duvaucel’s gecko (Hoplodactylus duvaucelii) is the largest New Zealand gecko, growing up to 16cm long and weighing as much as 120grams. The species are named after French naturalist Alfred Duvaucel, although not for any good reason. Duvaucel explored India, not New Zealand. But the museum specimens taken to Europe were initially credited to him – before their true origin was discovered. Still, the name has stuck.

The species is characterised by a large head and long toes with large pads, enabling them to climb glass should they wish to do so. They are generally grey with a green or olive hue, frequently adored with irregular blotches on the body.

These nocturnal creatures inhabit rocky, forested areas on offshore islands, foraging on the ground and climbing. Fossil records suggest they were once widely distributed on the mainland, but predation by introduced mammal species – especially rats – decimated these populations.

Ironically, the only wild Duvaucel’s gecko spotted on the mainland in the last century was a found dead in a mouse trap within a predator-proof fenced area at the Maungatautari wildlife reserve in the North Island’s northern Waikato region in 2010.

It is hoped that this was a member of a local wild population, but studying the movements of arboreal forest lizards – especially in regions of low density – is challenging.

Conservationists have used a range of techniques including providing lizard houses, different types of traps, artificial retreats and plain-old spotlighting with mixed success. One scientist had better luck capturing lizards using foam covers placed on tree trunks. These appeared superior in areas where the geckos were known to be more abundant.

Duvaucel’s geckos eat insects (including weta and puriri moths), fruit and nectar. They can be kept by licensed herpetologists in New Zealand but their preference for larger prey items does make them a little more challenging to maintain. They also take a relatively long time to reach maturity (around four years) which means that breeding can be a slow process.

Massey University runs a captive breeding program specifically to repopulate certain areas with Duvaucel’s geckos. It was during a routine check of these animals that a carer discovered a breeding female with abdominomegaly.

Le Souef examined the gecko, palpating several firm masses in the abdomen. She didn’t feel like a gravid female should.

Radiographs revealed a diffuse, radio-opaque mass effect in the mid to caudal abdomen, displacing one of the lung fields to the right. Ultrasound demonstrated a large, round, homogenous mass with an echogenic capsule in the caudal abdomen.

“It was so huge it was taking up her whole abdomen,” Le Souef said.

The female, unnamed, was treated with subcutaneous fluids and antibiotics (ceftazidime via intramuscular injection) and hospitalised.

“She had not been passing faeces,” Le Souef said. “It was difficult to tell from the examination whether she had been eating as she had not lost weight, but as she was housed with other animals they may have been eating her share. As she had not passed any faeces we concluded that she had probably not been eating a lot.”

Veterinarians at the zoo were concerned that the gecko may be suffering from marked obstipation or dystocia. The decision was made to perform an exploratory celiotomy with a view to resecting the mass or masses if at all possible.

Anaesthesia was induced with an intramuscular injection of alfaxalone CD. The patient was intubated and maintained on isofluorane in oxygen via intermittent positive pressure ventilation (IPPV). Le Souef performed a paramedian incision and blunt dissected around the hair-raisingly large abdominal vein.

Inadvertent transection of such a vein would be fatal in an animal this size.

“This vein is absolutely enormous,” Le Souef said. “When we opened her up we could see a huge mass protruding – with the abdominal vein sitting right on top of it! The vein was being stretched over the mass.”

Le Souef used cotton buds to gently push the vein out of the way. Using blunt dissection she was able to exteriorise the mass, along with a second, smaller mass.

“I had to keep extending the incision and kept worrying that she might not make it through the surgery – it was quite a long surgery and quite a large mass, but she had a great anaesthetic,” Le Souef said.

“It was apparent that the masses were ovaries. They looked like tumours to begin with – and I expected many more vessels to be attaching to these but there weren’t many. I was able to use small haemostats to clamp them off – apart from that it was a matter of gently dissecting away soft tissue.”

Exploration of the remainder of the abdomen revealed no further lesions. The gastrointestinal tract was empty. The abdomen was lavaged with saline and closed routinely using an everting mattress pattern.

“When you make the incision the wound edges tend to roll inwards which is why I used an everting pattern,” Le Souef said.

Post-operatively, the gecko continued to receive ceftazidime (one injection every 72 hours at standard doses for three weeks), in addition to butorphanol and meloxicam for analgesia and anti-inflammatory action.

At the beginning of the procedure the gecko weighed 65 grams. Following the removal of the masses (10grams and 1 gram respectively), she weighed substantially less at 54grams.

But once the masses were removed, it didn’t take her long to flourish. A few days post-operatively, the gecko weighed a more respectable 60 grams.

Her sutures removed after a skin slough.

Histopathologic evaluation confirmed that the masses were indeed ovaries.

“These geckos give birth to live young, so I think this was a preovulatory stasis.”

Of course, she won’t be able to breed.

“Her future is as an educational animal,” Le Souef said. “She is very easy to handle, so although she won’t be able to directly help with repopulation she can spread the word for her species.”

Reference

Bell TP (2009) A novel technique for monitoring highly cryptic lizard species in forests. Herpetological Conservation and Biology 4(3):415-425.

ANNE FAWCETT