Rainbow Closer

Photo courtesy of Dušan Veverkolog via Unsplash

The rainbow lorikeet (Trichoglossus haematodus) is well known to most Australians, especially on the eastern seaboard, where it dwells in bushland and urban settings, such as Sydney.

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There wasn't much Dr. Claude Lacasse could do a decade ago when she first encountered patients suffering from a severe bout of lorikeet paralysis syndrome.

The rainbow lorikeets, a brilliantly colored native parrot common in eastern Australia, were almost entirely frozen by the mysterious condition. They couldn't walk, let alone fly, and had to be force-fed.

"We would give them a few weeks and they wouldn't get much better," she said. "So we'd end up euthanizing them."

Hope flickered a few years later after Lacasse became a wildlife veterinarian at the Royal Society for the Prevention of Cruelty to Animals (RSPCA) in the state of Queensland. She realized she had two of the charity's large aviaries at her disposal, providing her with an opportunity to experiment.

"I put a few [sick] lorikeets in one, to just leave them and see if they ever got better," she said. "And, after three or four months, they were perfect!"

Lacasse had discovered a treatment method — give sufferers plenty of time to recover on their own, with supportive care. But she still didn't know much about the disease. She contacted Dr. David Phalen, a bird expert and professor at the University of Sydney, to see if he would help her take the aviary experiments further.

Now, their years-long research, which includes contributions from several other practitioners, has been published in the Australian Veterinary Journal.

It provides, for the first time, a detailed analysis of the frequency of occurrence of LPS, as the syndrome is known, and its severity, treatment options and prognosis, based on 1,119 cases diagnosed during 2017 and 2018 at two RSPCA wildlife hospitals in Queensland.

Crucially, it also identifies a suspected cause: a toxin from a plant — though the type of plant is yet to be determined.

The lowdown on a curious condition

Rainbow lorikeets (Trichoglossus haematodus) are gregarious parrots that dwell anywhere from rainforest and coastal bushland to urban settings, mostly along Australia's eastern seaboard. LPS sufferers, however, tend to be confined to northern New South Wales and southern Queensland. The syndrome has been identified less commonly in other species of lorikeets in Australia.

As described in the new research, clinical signs vary in severity and include an inability to fly, flaccid paralysis of all limbs and the neck, an inability to blink, paralysis of the tongue, an inability to swallow and voice change.

Some birds die from immediate complications associated with severe paralysis, such as an inability to eat or breathe. Many others die from indirect causes, such as being picked off by predators while on the ground or hit by cars because they can't fly or move properly.

"I can only imagine what they must be going through, thinking about not being able to move and wondering how their end is going to come," Phalen said.

In general, paralysis as a disease symptom can have several possible causes. For example, botulism, a type of food poisoning resulting from a toxin produced by the bacterium Clostridium botulinum, can paralyze muscles, including those used to breathe, and affects all kinds of animals, including cattle and humans.

Cedar waxwings in North America have been known to lose muscle coordination after getting drunk on fermented berries. Swamp harriers in New Zealand have developed clenched-feet paralysis due to suspected lead poisoning.

Lorikeets in other parts of Australia, such as in Sydney or the southern state of Victoria, are sometimes afflicted with various forms of paralysis, including clenched claws, which at least one study said could be caused by a virus. Lacasse said she's seen lorikeets develop clenched-claw paralysis from flying into a window and bumping their heads, becoming partially stunned.

LPS, she and Phalen agree, is a distinct condition with a unique set of signs. Lacasse, who's seen thousands of LPS cases, says telltale signs are an inability to blink and a change in voice to a lower, slower call. "I know if it's LPS just by hearing them in a box," she said. "I don't even have to look at them."

A puzzler decades in the making

According to the new study, the number of LPS cases each year ranges from hundreds to thousands, making it "one of the most important wildlife diseases and animal welfare concerns in Australia." Little information exists about how long LPS has been around. Phalen is aware of anecdotal accounts in the scientific community of "those botulism lorikeets" dating back to the 1980s. He and Lacasse say the number of affected birds they see each year is increasing.

Their research found that LPS is a seasonal disease seen in October through June, and peaking in December, January and February, which are the summer months in Australia.

To assess severity, the researchers grouped the 1,119 sufferers, none of which could fly, into four categories prior to treatment. Category four was the mildest — the birds were able to blink, swallow, walk and hop — and category one the most severe — they were unable to stand, blink and swallow.

Treatment consisted, where appropriate, of subcutaneous fluids, assisted feeding, the pain reliever meloxicam and Systane eye drops.

Of 571 lorikeets in category one, 27 were treated intensively, and of those, 60% survived. The prognosis gradually improved per category: Of the 130 in category four, only three died following treatment.

Still, even mildly affected birds were intensively cared for by veterinarians. Moreover, recovery times were slow for all four categories: The median number of days in care for category one cases, including treatment and rehabilitation, was 106, declining to a still-substantial 53 days for birds in the least-severe category four.

Caring for lorikeets in category one likely would tax the resources of wildlife veterinarians and carers, the paper says, perhaps making birds presenting with less severe signs better candidates for treatment.

Cracking the code: The final hurdle

To identify a culprit, the researchers painstakingly ran tests to rule suspects in or out. The involvement of a virus, they determined, is highly unlikely, in part because no inflammatory lesions were found in the brains they examined.

A couple of lorikeets were found to have high concentrations of heavy metals in their systems, namely cadmium and lead, but others had either no exposure or concentrations that weren't in the toxic range. Alcohol and clostridial toxins also were ruled out.

That left one likely cause: a relatively fast-acting plant toxin that works at the level of the neuromuscular junction, the researchers deduced.

They have another telling clue to work with: The fact that lorikeets get sick during warmer months indicates that the potentially toxic plant might bloom or have fruit seasonally — as well as having a relatively limited range to that of northern NSW and southern Queensland.

Steps to pinpoint a plant species are underway. The University of Sydney has set up a "citizen scientists" project asking members of the public to report what they see rainbow lorikeets eating.

Lacasse and Phalen, noting that the number of LPS sufferers seems to be growing each year, suspect the culprit isn't a native plant.

"Our hunch, which is unsubstantiated at this point, is that it is caused by an introduced species," Phalen said. "And it might be that this introduced species has become a little bit more popular over the last several decades and people are planting more and more of it."

Lacasse adds that while thousands of rainbow lorikeets are unfortunate enough to get LPS, that's still a reasonably small number of the entire population, recently estimated at 19 million. "It's not a main food — otherwise, all the lorikeets would be dropping out of the sky," she said.

Feeding trials pose an ethical dilemma

Finding the culprit is tough work because the toxin appears to take effect quickly but not immediately, giving sufferers time to fly away from the source of intoxication. Lorikeets tend to digest their food rapidly, and none presenting with LPS in the study had food in their gut. Sufferers weren't found under major roosts, indicating they were succumbing to the toxin before returning to roost each night.

Lacasse has been trying to sort through feces for signs of a culprit, but droppings are in short supply because patients have already passed the food, or haven't been able to eat much before being admitted for care. "It's a nightmare of a disease to investigate," she said.

That leaves the citizen scientists project, which the researchers hope will help them identify a culprit next year, or earlier if they get lucky.

If they can at least shrink down the suspect list, Lacasse and Phalen could consider feeding trials, though they admit this would be a less-than-palatable option because those might, by design, cause birds to develop LPS.

"If you had some lorikeets that couldn't be released back into the wild for whatever reason, you might be able to feed them suspects, then if they develop severe signs, euthanize them humanely," Phalen said. "It's something you'd need to be very careful about explaining to people, including the reasoning behind what you're doing."

The payoff would be obtaining valuable information that could be used to reduce the incidence of LPS. For instance, should a specific plant species be identified, the general public could be discouraged from planting it, or could perhaps cover its berries during the warmer months.

Knowing more about the cause also might allow veterinarians to work out more optimal treatment plans.

"For a veterinarian, they're nice patients because they can't bite you as much as usual," Lacasse joked. "But it's not fun for them, and it's amazing to watch them recover from it. Knowing the cause could make it easier for us to help them fly again."