Scientists in Australia announced today that they have conducted the first successful field trial of a vaccine against chlamydia in koalas.
Chlamydia is a main cause of koala deaths. It can cause blindness and koalas can get reproductive tract disease, which can lead to infertility.
Peter Timms and Adam Polkinghorne, microbiologists at the University of the Sunshine Coast (USC), said this year’s field trial has involved wild koalas roaming in their natural habitat in the Moreton Bay region north of Brisbane, Queensland.
Timms said the results were very promising. Vaccinated animals all showed good immune responses to the vaccine and their chlamydia infection levels were lower than those in the unvaccinated animals.
The vaccine trial is part of a five-year project, which has cost about 750,000 AUD (about 666,000 US$).
The five previous trials involved captive koalas. The field trial involved koalas that were already being tagged and monitored in the area of the Moreton Bay rail project.
Sixty koalas captured as part of the tagging and monitoring programme were included in the trial. Thirty animals received the vaccine and 30 remained unvaccinated as a control group. All 60 koalas were fitted with radio collars so they could be monitored.
None of the vaccinated animals went from having an infection to getting the actual disease, but three of those in the control group did develop disease.
“This large trial has confirmed that the vaccine is safe to give not only to captive koalas, but also to koalas in the wild,” Timms said.
Polkinghorne said: “The trend we have seen, and will hopefully be able to show through future monitoring, is that vaccinated koalas control their infections better, they are less likely to get new infections, and they appear to be more reproductively active than the koalas that were not vaccinated.
“We’ve got six months of data so far, and we will be following those 60 koalas for another 18 months at least and we’ll be monitoring their chlamydial infection rates and their reproductive status.”
Polkinghorne adds that vaccination not only appears to be protecting koalas from chlamydia, but also seems to have a therapeutic value. “Previous research at the Australia Zoo wildlife hospital has already indicated that vaccination can help koalas already showing chlamydia symptoms to fight off their disease.”
This is important, Polkinghorne says, because of the difficulty of getting medication to treat chlamydia. “The company that manufactures the main antibiotic used to treat it just simply stopped production. Thanks to a groundswell of reaction to this, they have since manufactured a few more batches, but there is no security in that.”
The president of Koala Action Inc. in the Moreton Bay region, Wanda Grabowski, who is a veteran koala carer, said she was thrilled by today’s news. “It shows dissenters that funding this type of scientific research has produced a result that is beneficial to koala populations in both the long and short term.
“This breakthrough will no doubt improve the chances of a population already on the brink of extinction in many areas.”
The prevalence of chlamydial disease in koala populations significantly reduces their breeding rate, Grabowski says. “In the long term, any increase in the breeding rate will have a positive impact on the koala populations’ ability to remain sustainable in South East Queensland.”
Chlamydial cystitis, Grabowski says, is a painful and debilitating disease, thickening the bladder wall and resulting in reproductive disease. “To be able to reduce its negative impacts will certainly improve the quality of life of those sick animals in the short term.”
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The next step, Polkinghorne said, will be to try to deploy the vaccine through koala carers. “Hopefully, if we get more funding, we might be able to deploy the vaccine to whole populations rather than individual animals.”
While the scientists’ current funding limits them to completing the Moreton Bay trial, they are already working with the Friends of the Koala group in East Lismore, New South Wales. In a small trial at the Koala Care Centre, which began at the end of August, seven koalas are being studied, six of whom have been vaccinated and one is being monitored as a control.
The vaccine research, which began at the Queensland University of Technology (QUT), has been funded by two Australian Research Council linkage grants totalling more than 550,000 AUD and has received significant industry and government support.
Phase one of the trial took place at the Lone Pine sanctuary near Brisbane in 2007. The aim was to decide which would be the best vaccine adjuvant to use. Phase two was carried out at Queensland’s Australia Zoo in 2010-2011.
At Moreton Bay, the scientists were lucky to be able to ‘piggy-back” onto the tagging and monitoring programme, so they didn’t have to pay for koala captures. “A field trial where we have to capture the koalas ourselves would cost about two and a half million dollars,” Polkinghorne said.
The scientists are hoping for future state and federal financing. A special fund to raise money for the research has been set up by the USC’s development office and the researchers have also launched a crowdfunding campaign.
“A project of this size and cost requires a large team of people, including veterinarians and field teams, in addition to the laboratory work,” Timms said.
Timms says it would be unrealistic to try and vaccinate all Australia’s koalas, but it would make sense to treat the hundreds of animals that go into care centres and animal hospitals. “That’s an ideal opportunity to vaccinate those koalas while they’re already there, before they’re released back into the wild.”
There are also vulnerable populations in regions like Moreton Bay, where human activity is impacting greatly on the koalas and their habitat, Timms says. These animals could be captured and potentially the whole local population could be vaccinated.
There are varying rates of chlamydial disease in different areas of Australia. Many animals who are infected with the disease, and are passing it on, don’t show physical symptoms.
Polkinghorne says that about half of the koalas coming into care at Australia Zoo wildlife hospital have chlamydiosis.
Studies have found that, in South East Queensland, the detectable prevalence of the disease in the wild koala populations is about 47 percent.
On the basis of tests on animals admitted to hospitals, 67 percent of koalas in the Redlands area south of Brisbane have clinical signs of chlamydial disease.
In some koala populations in southeast Queensland up to 50 percent of the females are infertile. “This means that when koalas are killed in car hits or dog attacks the population won’t be replaced,” Polkinghorne said.
It is thought that chlamydia may also be causing infertility in male koalas.
Scientists had thought there was less chlamydial disease among koalas in southern parts of Australia than in Queensland, but Polkinghorne says scientists are now finding that many of the koalas in the south actually do have disease. “We just never looked hard enough to observe it.”
On vaccine safety, Polkinghorne says the Moreton Bay trial is the sixth trial to be carried out, and about 110 koalas have been vaccinated. “Most of the koalas in the Lone Pine sanctuary have now been vaccinated against chlamydia so we now have five years’ worth of data on the health of those animals. They have shown no adverse consequences during the vaccine trial or subsequently, and the koalas in care at the Australia Zoo showed no adverse reactions. With that data, we are quite confident that the vaccine is safe.”
An endangered species
In 2012, the koala was listed as vulnerable in Queensland, New South Wales, and the Australian Capital Territory. Campaigners say this is not enough and the animal should be listed as endangered throughout the country.
As koala habitat continues to be destroyed for urban and industrial development, the iconic creature that tourists queue up to cuddle is already becoming extinct in certain areas. As well as suffering the ravages of disease – including the koala retrovirus, which is also having a devastating impact – thousands of them are dying as a result of car hits and dog attacks. Bushfires continue to kill thousands more and others are sustaining horrific and often fatal injuries on logging plantations.
In 2011, researchers assessed what would need to be done to stabilise the koala population in the Redlands area. “They discovered that you would have to stop 100 percent of deaths caused by car hits and all land clearing, and neither of these things would be possible,” Polkinghorne said, “but you would only need to stop 50 percent of disease to stabilise that population, which shows that chlamydia is an important cause of death and it’s a preventable cause of death.”
When European settlers first arrived in Australia, there were 10 million koalas in the wild. There are now a few hundred thousand at most. A senate inquiry in 2011 was told that there are probably between 50,000 and 100,000.
Over the past 20 years, koala numbers have dropped by 40 per cent in Queensland and by a third in New South Wales. In the Pilliga Forest of northwest New South Wales, three-quarters of the koala population has been wiped out since 2000.
“The perils facing koalas predominantly relate to the loss and fragmentation of habitat which brings them to the ground in search of food, shelter, mates, and dispersal opportunities,” Grabowski said. “It is then that they are in danger of being struck by motor vehicles or attacked by domestic or wild dogs. If more koalas can breed successfully (usually one joey per year when sexually mature), with luck and effective mitigation strategies, many of these joeys will reach adult hood.
“This vaccine will allow local, state, and federal governments time to do what they must to ensure a future for Queensland’s faunal emblem.”
A tough disease to fight
Koalas are affected by two different strains of chlamydia: chlamydia pneumoniae and chlamydia pecorum. Chlamydia pecorum is the most prevalent and the highest rates of infection are in Queensland and northern New South Wales.
Damien Higgins from Sydney University has been examining whether habitat fragmentation affects chlamydial diversity. “When you’ve got large continuous habitat and you’ve got lots of animals, chlamydia is always coming across susceptible hosts, but when you get small fragments there’s a greater tendency for everybody to get exposed, everyone to develop some level of possible immunity against reinfection and that provides stronger evolutionary pressure on chlamydia to diversify so it can dodge the immune system.”
Adam Polkinghorne says scientists have probably completely underestimated the level of infection within wild populations because many studies have purely based their reporting on the presence of disease rather than the shedding of chlamydia.
“We still know very little about the transmission of chlamydia pecorum within an affected population, and between affected populations. We don’t know why some koala populations seem to struggle with their chlamydial infections while, anecdotally, other koala populations don’t.”
Comparing chlamydia from koalas that are showing disease symptoms and those that aren’t, there doesn’t appear to be much difference, Polkinghorne says. “So it might not be the bug; the genetics of the koala will definitely be a factor.”
The scientists are sequencing the genomes of a group of koalas within the Moreton Bay field site, comparing those who developed the disease with those that resolved their infections. “This may show us whether there is some genetic basis for why some koalas develop disease and others don’t.”
Chlamydia also exists in cattle and sheep, and most seriously in sheep, causing arthritis in lambs.
Polkinghorne says the scientists have started a trial vaccinating sheep, starting with a safety trial at the university. “The intention is that over the next three years we will take the prototype vaccine, which is very similar to the one we are using for koalas, and we will hopefully be trialing it on farms in New South Wales.”
Scientists have meanwhile been examining whether there is a relationship between chlamydia in koalas and the disease in cattle. “Data suggests there may well be a link,” Polkinghorne said.
Researchers have been studying short pieces of chlamydia DNA. “There appear to be at least six unique chlamydia pecorum strains identified in koalas and three of those were found in Australian livestock.
“As technology advances, we’re probably going to be at the stage very soon where we will be able to analyse the whole DNA sequence.”
The vaccine trials have shown that the antibody generated is able to recognise significantly different chlamydial strains. This means scientists won’t have to develop different vaccines to treat different types of chlamydia.
In preliminary studies, researchers have discovered that a nasal spray achieves the same results as injections.
Questions remain about whether a “live challenge” trial –in which an animal would be vaccinated and exposed to chlamydia – should be undertaken, who would pay to produce a vaccine, and how exactly it would be used (which koalas should be vaccinated).
Earlier article: Koala extinctions already a reality