A-News / Mini Reviews / Travel

It’s been a Month for Malaria

Source: rollingalpha.com

 

My life-long arch nemesis: mosquitoes, have been enjoying a nice little time in the media spotlight with a promising malarial vaccine for children from PLOS Medicine [1,2] whilst concern is being made at the increasing resistance of Malaria strains to Artemisinin drugs [3,4]. I secretly wish there would be advances on making the host of Plasmodium (the parasite that causes Malaria) i.e. mosquitoes, extinct because really – do they have any purpose at all??

In a perfect world where we’ve made the perfect substance that mosquitoes can not adapt to and we lop off all mosquitoes, there is no way for Malaria/other disease to get into us. Unfortunately, it’s impossible to predict selection pressure and that in itself is impossible to remove. Which brings to question, what is happening with all that genetic modification of mosquitoes [5-10]?

I remember vaguely in high school of the suggestion to breed female mosquitoes incapable of transmitting Plasmodium via an enzyme mutation in the gut that would inhibit its growth within mosquitoes [10] at which I immediately celebrated the end of disease spreading mosquitoes and never thought of them again. Of course, ten years later and I’m still learning about the Malaria cell cycle, getting drilled into me that it’s now one of The Big 3 and staring at dead mosquitoes I’ve stunned in my room, wondering if they’re the tiger mosquitoes that spread Dengue and Chikungunya [11]. So somewhere along the line, I guess that fell through.

Sifting through the recent literature, I learn it’s about the game of evolution – the survival of the fittest [5, 6]. Genetically modifying mosquitoes just don’t make them the stronger species to survive the disease spreading population in the wild. That is until Marelli et al. gave evidence for genetically modified (GM) mosquitoes fitness when feeding on malaria infected mice. Julia Layton explains it significantly more eloquently than I could here [5] but basically, this makes solid that it is possible for GM mosquitoes to hold an advantage over wild population. Yet it still just wasn’t close enough or definite enough to make it certain they could last in the actual Wild Outside having used only a malaria specific mice strain and an unsatisfactory survival rate in an environment where malaria wasn’t present.

Fast forward five years and to 2014, some scientists have decided they’re not going to look at the gut and ingestion of the parasite or making mosquitoes malaria immune, they’re going to get rid of the vector altogether [7-9]. As female mosquitoes are the ones who transmit the parasite, Galizi et al. have inserted an engineered gene that results in fully fertile mosquito strains producing over 95% male offspring. The prospects of breeding out mosquitoes in this way are rather heady with the ideal that mosquitoes become their own enemy as the female population drops. The gene is also rather diverse in that it makes it difficult for resistance to evolve to a specific section.

Trials have actually already been successfully run in small, enclosed environments such as islands [11] but objections have been raised in concerns with “playing God” and not knowing the ecological and evolutionary effect. Now I can’t say this with any solid evidence but in my personal opinion – does anyone know the ecological and evolutionary contribution mosquitoes have?! Because a quick google search does not tell me anything! What eats mosquitoes? Frogs? Spiders? Take mosquitoes out of the equation – we gots ’em flies and other flying insects. I suppose they could drastically decrease without mosquitoes to be eaten…but I can’t really envision that with my teeny undergraduate mind.

But I must grudgingly admit that there is no way to account for possible selection pressures that could force the parasite itself to mutate to a new, male vector.

I have to note though, while Malaria publicity is booming and I have absolutely no complaints about figuring out ways to make mosquitoes extinct – we have to keep in mind that as we get better at fighting the disease with improved vaccines and possible vector extinction, we don’t forget the other ailments that will ultimately gain greater importance as Malaria falls. Even now in sub-saharan Africa, places are slowly but surely no longer to be high endemic areas and it then leaves behind a surfeit of diseases that may become hidden under this Malaria billboard we have gotten so used to seeing that it almost feels like we will never be rid of. Kind of like if Malaria was Kim Kardashian and the neglected diseases are the Melbourne Housewives. I mean, KK may be super important and it feels like she will always be an ever presence in Reality Royalty but as her fame dies down, we forget that there are a wealth of crazy reality stars. KK’s publicity team and her Kanye matrimony keep her ever present but is she actually still that big?

Ok maybe I’ve stretched the KK metaphor too far now and KK does not deserve to be compared to Malaria and I may be getting lost in this very mismatched analogy. What I am trying to say is that soon we will have to split funding from Malaria and gift it to elsewhere and we should welcome that change because then it will mean that Malaria is finally losing. Now it’s a whole another ramble to remain alert and not complacent unlike our TB situation where we slipped and here we are.

Well. I still vote that mosquitoes have absolutely no purpose at all in the cycle of life. They’re useless, annoying, have no contribution at all to the bigger picture  and spread diseases – at least to my knowledge. I mean, look at that picture.

Any biologists who would like to make a defense for the accused?

 

WHAT THE NUMBERS MEAN

[1] ‘Milestone’ for child malaria vaccine, by Smitha Mundasad. BBC News. 29 July 2014. http://www.bbc.com/news/health-28541939

[2] Efficacy and Safety of the RTS,S/AS01 Malaria Vaccine during 18 Months after Vaccination: A Phase 3 Randomized, Controlled Trial in Children and Young Infants at 11 African Sites. PLOS Medicine. 29 July 2014. http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1001685

[3]  “Call for ‘radical action’ on drug resistant malaria” by Helen Briggs. BBC News. 30 July 2014. http://www.bbc.com/news/health-28569966

[4] Ashley et al. “Spread of Artemisinin Resistance in Plasmodium falciparum Malaria” The New England Journal of Medicine. 31 July 2014. http://www.nejm.org/doi/full/10.1056/NEJMoa1314981?query=featured_home

[5] “Can genetically modified mosquitoes wipe out malaria?” By Julia Layton. How Stuff Works. 2007. http://science.howstuffworks.com/life/genetic/gm-mosquito.htm

[6] Marelli et al. “Transgenic malaria-resistant mosquitoes have a fitness advantage when feeding on Plasmodium-infected blood.” March 2007. http://www.pnas.org/content/104/13/5580.abstract

[7] “Genetically modified mosquitoes could wipe out malaria” by Alexandra Sifferlin. Time Magazine. June 10 2014. http://time.com/2852568/genetically-modified-mosquitoes-could-wipe-out-malaria/

[8] “Genetically modified mosquitoes offer hope in malaria fight” by Kate Kelland. Reuters. June 10 2014. http://www.reuters.com/article/2014/06/10/us-health-malaria-mosquitoes-idUSKBN0EL1JM20140610

[9] Galizi et al. “A synthetic sex radio distortion system for the control of the human malaria mosquito.” Nature Communications. June 10 2014. http://www.nature.com/ncomms/2014/140610/ncomms4977/full/ncomms4977.html

[10] Anil K. Ghosh, Paulo E. M. Ribolla, and Marcelo Jacobs-Lorena. “Targeting Plasmodium ligands on mosquito salivary glands and midgut with a phage display peptide library.” http://www.ncbi.nlm.nih.gov/pmc/articles/PMC60861/

[11] “The Asian Tiger Mosquito is on our Doorstep” by Greg Bearup. The Australian. Jan 18 2014. http://www.theaustralian.com.au/news/features/the-asian-tiger-mosquito-is-on-our-doorstep/story-e6frg8h6-1226804215605?nk=35fb93dbde1801dd46334a99a41f64e7

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