Fighting Infections, Old And New

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Aedes aegypti mosquito is the causative agent of Chikungunya, Zika fever and Dengue fever Credit: Pixabay

Soon after the Zika virus outbreak started in Brazil in 2015, the country embarked on an ambitious program targeting the Aedes aegypti mosquito, which was widely believed to be the main culprit in the virus’s transmission.

“When I went to a conference focused on the Aedes aegypti at the time, however, I came away wondering why there was such an emphasis on the species when nobody had any infection data at all to support the claim that Zika was being transmitted by it in Brazil,” said Professor Fiona Hunter, one of Canada’s top medical entomologists.

Professor Hunter, who has studied biting insects for more than 25 years and has a laboratory at the Brock University in Ontario, Canada, was one of the speakers at the recent Commonwealth Science Conference 2017, a gathering in Singapore of more than 400 scientists from 37 Commonwealth countries.

Organized by Singapore’s National Research Foundation and Britain’s Royal Society, the conference had “Emerging Infectious Diseases” as one of its themes, as it is a common challenge for all of the participating countries.

The Zika conundrum

Professor Fiona Hunter, Brock University spoke at the Commonwealth Science Conference 2017 in Singapore, June 2017, co-organised by the UK’s The Royal Society and Singapore’s National Research Foundation.
Photo Credit: National Research Foundation

Prof Hunter said that her research during the worldwide Zika virus epidemic – it was designated a “global public health emergency” from February to November 2016 by the World Health Organisation (WHO) – showed the importance of keeping an open mind when combating emerging infectious diseases.

“After the conference, I went home and looked through the literature, and found that precisely eight papers had been written about mosquitos and the Zika virus between 1952 and 2014. When I started looking at things more closely, there was not a lot of evidence for Aedes aegypti being the major vector at all,” she said.

“Here was this huge effort in Brazil to control the Aedes aegypti, and yet the data supporting that conclusion was really sparse. In fact, some of the studies that have been done more recently say that the species is a very poor vector,” she added.

While a few research papers had concluded that the mosquito is a fantastic vector with 100 percent transmission efficiency, these were based on a sample size of eight mosquito individuals, and the mosquitos had been fed a different diet compared to the other studies, she noted.

New research shared at science conferences months into the Zika virus outbreak suggested that another mosquito species that is much more widespread in Brazil, the Culex quinquefasciatus, could be involved in the virus’s transmission, although the researchers’ findings were disputed by others.

“As an evolutionary biologist, I went to the phylogeny, and in fact, that shows clearly that the West Nile, Saint Louis encephalitis virus and Zika virus are really closely related, and perhaps we should move the bar and say that those three viruses are all Culex-associated,” said Prof Hunter.

Her own research on 50 wild-caught Culex pipiens pipiens mosquitoes found that 11 of them had picked up the virus, and at least one of them had it in its saliva – a necessary precursor to spreading it.

“What I’d really like to suggest is that we keep an open mind. Instead of saying that the Zika virus must absolutely be an Aedes-associated virus, maybe we can open our minds and say that there is room for other species to be involved,” she said.

The superbug threat

Even as emerging infectious diseases dominate headlines, an equally important battle must be waged against antimicrobial resistance, said Professor Hsu Li Yang, the programme leader of the Antimicrobial Resistance Programme at the National University of Singapore’s (NUS) Saw Swee Hock School of Public Health.


Dr Hsu Li Yang, National University of Singapore, spoke at the Commonwealth Science Conference 2017 in Singapore, June 2017, co-organised by the UK’s The Royal Society and Singapore’s National Research Foundation.
Photo Credit: National Research Foundation

Prof Hsu, whose research includes the genomics and epidemiology of Methicillinresistant Staphylococcus aureus, a bacterium that is resistant to many antibiotics and causes various health problems, is also deputy clinical director of the Singapore Ministry of Health’s Communicable Diseases Centre, and senior consultant and head of the Department of Infectious Diseases at the country’s Tan Tock Seng Hospital.

In February 2017, the WHO published its first ever list of antibiotic-resistant “priority pathogens”, specifying 12 families of bacteria that pose the greatest threat to human health.

“Antibiotic resistance is growing, and we are fast running out of treatment options. If we leave it to market forces alone, the new antibiotics we most urgently need are not going to be developed in time,” said Dr Marie-Paule Kieny, WHO’s assistant director-general for health systems and innovation, at the time.

Such antibiotic resistance could render key medical surgeries, including organ transplants, caesarean sections and chemotherapy, too dangerous to perform. “Our ability to do complicated surgeries is based on our ability to control or prevent infections as they arrive, and treat them if we are unable to prevent them,” said Prof Hsu.

“In the past two decades, we have seen no new classes of antimicrobial drugs being developed, and we will see our medical progress regress because of drug resistance if this is not addressed,” he said.

He noted that antimicrobial resistance is caused by several factors, including the inappropriate and excessive use of antibiotics, both for medical treatment and in animal farms.

Poorly handled medical tourism and emergency medical care, where patients are transferred between hospitals and across countries with little to no safeguards against what they may be bringing with them, are another cause for concern.

Several countries and organizations have stepped up their efforts against antimicrobial resistance. In December 2016, Singapore announced that it is developing a national action plan to tackle the problem, with the Ministry of Health, Agri-Food and Veterinary Authority, National Environment Agency and NUS working together to develop strategies.

The Combating Antibiotic Resistant Bacteria Biopharmaceutical Accelerator, or CARB-X, which comprises partners such as the United States’ Boston University and Britain’s Wellcome Trust, a biomedical research-funding charity, also awarded US$24 million in March 2017 to 11 biotech companies and research teams working on new antibiotics and diagnostics targeting drug-resistant superbugs.

Through CARB-X, at least one new antimicrobial drug will be registered by 2027, with several more expected as well.

While these efforts are all laudable, more also needs to be done to teach young children about proper antibiotic use, said Prof Hsu. “That will be more useful than all of the media warnings that we could possibly put out, and will have benefits for future generations.”

Editorial Credit: NRF