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15 June 2023

As a JCU PhD student, Lincoln Timinao elected to spend the entire COVID-19 lockdown period with his test subjects – mosquitoes – at the Papua New Guinea Institute of Medical Research (PNGIMR). A decision which has led to breakthroughs in malaria research.

Rather than focus on mosquito-to-human disease transmission, his study, completed late last year, did the opposite. It investigated the transmission of a major, but understudied malaria parasite species, Plasmodium vivax, from infected humans to colony-reared mosquitoes in a laboratory setting – creating new opportunities to test potential transmission-blocking vaccines and antimalarials.

Based at PNGIMR in Madang, the researcher also relied on the support of local study participants from communities willing to donate blood to feed the mosquitoes for his study – which helped confirm that people in PNG who are infected, but asymptomatic (show no symptoms) can still transmit malaria parasites.

“This means the whole World Health Organization agenda of trying to eliminate malaria within the region by 2050 will be challenging,” said Dr Timinao, who was appointed deputy head of the Vector-borne Diseases Unit at PNGIMR earlier this year.

The Papua New Guinean researcher studied biology and chemistry as an undergraduate at the University of Papua New Guinea (UPNG), then obtained a Swiss government grant in 2012 to undertake a Master of Science degree in Infection Biology at the University of Basel.

When AITHM Principal Research Fellow, Malaria and Vector Biology, Associate Professor Stephan Karl, who has close research links to the PNGIMR, suggested the then Senior Scientific Officer embark on a PhD project in 2018 that would utilise his sound knowledge of the colony mosquitoes, he agreed, although the proposed study goals were by no means easy.

The first was to develop an artificial system to feed the mosquitoes with infected human blood. The second, to confirm that even asymptomatic infected PNG residents were capable of transferring malaria parasites via their blood to the mosquitoes.

Establishing a reliable method to induce as many test mosquitoes as possible to drink the blood samples – in a controlled clinical setting – was not easy. Contrary to popular belief, wild mosquitoes mainly feed on nectar. Only female mosquitoes feed on blood once they have mated, as the blood is needed for their egg development. Mosquitoes in the PNGIMR colony are usually fed a sugar water solution via cotton-soaked pads.

Dr Timinao’s construction materials for the feeding system ranged from rubber bands and large paper cups (obtained from local shops) to glass tubes and two types of membrane designed to mimic skin – one was Parafilm (a plastic material) and the other was fashioned from thin, dried slices of pig’s gut.

Mosquitoes were collected in the cups, then trapped beneath mesh lids, secured by rubber bands. Glass tubes containing blood with the artificial skin membrane wrapped over the opening were then upended and pressed against the paper cup mesh to enable the mosquitoes to extend their mouthpieces through the mesh and pierce the membrane to feed.

Initial trials revealed that only 50 per cent of the mosquitoes were feeding, so Dr Timinao set about finding ways to improve their dining experience. He found they preferred to feed from the pig’s gut membrane, and starving overnight boosted their appetite. The feeding rate was increased to 85 percent.

In 2020, when the global pandemic hit and many colleagues left the Institute to go into isolation with their families, Dr Timinao chose to stay, anchored by his research, which could not be transferred to another location. It was a decision which meant he would not see his own family, who lived in another province, for one and a half years.

“It was hard,” he said.

With reduced staff, routine work also became a daily challenge; tending the mosquito colony throughout their different stages of development, from egg, aquatic life and pupa to adult insect, is labour intensive. “We were really struggling through the COVID period.”

In addition, the researcher also needed to raise more funds to continue his study and support himself. He managed to secure more than $60,000 from a range of sources, including The Australian Centre of Research Excellence in Malaria Elimination, the United States National Institute of Allergy and Infectious Diseases, and Rotarians Against Malaria, Australia.

The trials to fine tune the feeding regime had utilised uninfected blood donated by colleagues at the Institute. The next step involved obtaining infected blood. A nurse stationed at a local clinic asked patients presenting with malaria-like symptoms if they would be willing to donate blood for the study, which had full approval from PNG’s Medical Research Advisory Committee. Those that agreed underwent a malaria rapid diagnostic test. If it proved positive, their blood was rushed to the laboratory. Time was of the essence.

“We tried to reduce the time between ‘bleeding and feeding’ to no more than 10 minutes, as any changes, like a drop in temperature, affect the development of the parasite within the mosquito,” said Dr Timinao.

After several trials, he succeeded. “When I looked under the microscope and saw the mosquito guts had become infected, I think that was the best day of my life,” he said simply.

PNGIMR is now equipped to play a major role in testing potential malaria transmission blocking vaccines and other antimalarial drugs. It is currently collaborating with the prestigious, Melbourne-based Burnet Institute and Cambridge University to test some of their vaccines.

“We really want to be recognised and seen as equal partners in this kind of research,” said Dr Timinao, who managed to find time to publish three scientific papers during his PhD study, as well as several co-authored papers.

The former student who raised $60,000 to support his PhD project, is now co-investigator on a million-dollar United Kingdom Medical Research Council study and is one of the in-country leads of an International Centre of Excellence in Malaria Research $7 million-plus renewal application, in which JCU is a leading consortium partner.

“It feels really nice to be able to contribute back to the Institute, to do research again and be part of the whole research agenda. It's rewarding to be part of the whole research community,” he said.

That includes mentoring young researchers following a similar trajectory; highfliers such as Michelle Katusele and Rebecca Vinit, who will be undertaking their PhDs jointly between AITHM/JCU, UPNG and PNGIMR.

Both students have Master’s degrees from international institutions, more than a decade of experience in vector-borne diseases research, and published papers in prestigious scientific journals.

“I have always enjoyed assisting other researchers, so I am looking forward to mentoring them,” said Dr Timinao.  

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