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The East African : June 23rd 2014
The EastAfrican 32 OUTLOOK JUNE 21-27,2014 S CI E N C E Using GM mosquitoes to fight malaria Idea of using ‘sex-disto≥ting’ genetic defect to cont≥ol pest populations is not new but this one is p≥actical By PAUL REDFERN Special Correspondent S cientists from the UK have come one step closer to pro- ducing a genetically modified mosquito that will only produce male offspring, potentially offering a weapon in the fight against malaria. Following research by a team at Imperial College London, which involves injecting mosquitoes with a gene that causes the vast majority of their offspring to be male, further tests will be carried out to investigate the viability of the research in the wild and how the introduction of such mosquitoes will affect the ecosystem. The results of the study published in the Londonbased journal Nature Communications on June 10 said that scientists have now created mosquitoes that produce 95 per cent male offspring. The research centred on flooding cages of normal mosquitoes with the new strain of GM mosquitoes that caused a shortage of females and a population crash within six generations. “Shredding of the paternal X chromosome prevents it from being transmitted to the next generation, resulting in fully fertile mosquito strains that produce more than 95 per cent male offspring,” the Nature Communications report said. “This leaves very few X-car- rying sperm to produce female embryos.” In the wild the aim would be to slash the numbers of malariaspreading mosquitoes, which cause more than a million people a year to die, most of whom live in sub-Saharan Africa. “You have a short-term benefit because males don’t bite humans [and transmit malaria],” Andrea Crisanti, one of the authors of the You have a short-term benefit because males don’t bite humans [and transmit malaria].” Prof Andrea Christani, one of the authors of the study tribution to eradicating malaria. The engineering is a quantum leap in terms of what has been done before.” Although probably several years THE RESEARCH A gene from a slime mould was transferred into the African malaria mosquito Anopheles gambiae. This gene produces an enzyme called an “endonuclease” that chops up DNA when it recognises a particular sequence. The change is passed down through the generations, so that male mosquitoes pass it on to about half their male offspring . If the artificial strain is released into a population, it should spread until most males are only producing male offspring. away from field trials, researchers say the discovery marks an important step forward in the effort to produce a genetic control strategy. The scientific idea of using a “sex-distorting” genetic defect to control pest populations is not new but this is the first time it has been practically demonstrated. The researchers, led by Prof Andrea Crisanti and Dr Nikolai Windbichler of Imperial Col- lege London, transferred a gene from a slime mould into the African malaria mosquito Anoph- eles gambiae. This gene produces an enzyme called an “endonuclease” that chops up DNA when it recognises a particular sequence. The change is passed down new study told the Guardian. “But in the long term you will eventually eradicate or substantially reduce mosquitoes. This could make a substantial con- through the generations, so that male mosquitoes pass it on to about half their male offspring. This means if the artificial strain is released into a population, it should spread until most males are only producing male offspring, perhaps eradicating the population altogether. “Theoretically, if you have it on the Y [chromosome], one single individual could knock out an entire population.” Prof Andrea Crisanti said. The report said that in five test cages that started with 50 males and 50 females, when the team introduced 150 of the new GMaltered males, the number of females plummeted within four generations. Do monogamous women still need a pap smea≥? By TARA PARKER POPE New York TImes THE ANNUAL pap smear has been a cornerstone of women’s health for at least 60 years, and is credited with preventing millions of deaths from cervical cancer. However, in 2012, the US Preventive Services Task Force made decisive recommendations advising women to undergo pap smear screening less often. The goal is to test women often enough to catch early warning signs of cervical cancer, but not so often that women are subjected to unnecessary and invasive tests. Given that most cases of cervical cancer are linked to the sexually transmitted human papillomavirus, or HPV, it would seem that a monogamous woman who tests negative for HPV would not need regular pap smears. However, doctors advise that these women should still undergo pap smears as recommended for their age and medical history. Why? One reason is that many HPV infections clear up on their own without causing any problems, and it’s possible that a woman who tests negative for HPV still harbours a dormant form of the virus. While dormant HPV does not appear to be an immediate health risk or contagious to a partner, it could become active again if the immune system is compromised by another virus or health problem. A pap smear detects cervical cell changes that can result from a persistent case of HPV. A separate test, called an HPV test, detects only the presence of an active virus. “HPV never leaves your body,” said Laura Corio, an obstetrician and associate professor at Mount Sinai Hospital in New York. “It can come out at various times in your life.” Then there is the more complicated issue of monogamy. Just because a woman is monogamous, that doesn’t mean her partner is or always will be. Men and women in the most committed relation- ships may stray on occasion, and many will never admit this, even to their doctor. Estimated infidelity rates range from about 25 per cent of couples to as high as 70 per cent. A new sexual partner by either person in a relationship is a risk factor for the woman’s contracting HPV. Because of the possibility of a dormant virus and the potential for infidelity, doctors err on the side of caution and continue to offer Pap smears to monogamous women. Under the current guidelines, women should be screened no more than every three years. Women are advised to begin screening at age 21 regardless of sexual history. The task force also recommends against pap tests for women over 65, as long as they have had adequate prior screening and are not otherwise at high risk for cervical cancer. Women over 30 who do not want a pap test every three years can opt for one every five years along with an HPV test. Women who have unusual symptoms, an unusual pap test result or a history of cervical dysplasia, cervical cancer, HIV or other illnesses are likely to be screened more frequently. BRIEFS Daily intake of processed meats causes heart attack Men who eat lots of sausages and cold cuts are more likely to wind up with the hospital for heart failure, according to a study from Sweden. Researchers from the Karolinska Institute in Stockholm say processed meat, besides having quite a lot of salt, may also include nitrites and phosphate-containing additives. A single serving of deli ham is usually 57 grammes. The study said each 50-gramme increase in daily processed meat intake was associated with an eight per cent higher risk of heart failure and a 38 per cent higher risk of death from heart failure. Varsities link up to study malnutrition A regional inter-university initiative that seeks to boost training and research in East and Southern Africa has been launched at the Jomo Kenyatta University of Science and Technology. The partnership, which involves three universities; Makerere (Uganda), Stellenbosch (South Africa) and JKUAT, seeks to enhance the universities’ capacity to address malnutrition in Africa. They will review existing food and nutrition science programmes, develop course material, conduct short-term courses for technical and academic staff and conduct joint research and teaching through virtual teaching and learning facilities. Researchers declare ‘war’ on banana wilt An African consortium of international researchers and growers, backed by policymakers in regional blocs of East and Southern Africa have declared “war” against a highly pathogenic form of the Banana wilt known as Foc TR4 previously confined to Asia. Known as “The Stellenbosch Declaration on addressing the threat of Fusarium oxysporum f. sp. cubense tropical race 4 to banana production in Africa,” the policy recommendations have been signed by member states and endorsing institutions. Banana wilt has affected production. Picture: File Truvada pill protects HIV-discordant couples People taking PrEP in the form of a daily Truvada pill have a super-high rate of protection (98 per cent), according to a study by Columbia University’s Mailman School of Public Health. However, the effectiveness of the treatment goes down if multiple doses are missed. An injection every few months, the researchers said, would erase the fear of missing the daily dose. The treatment would be of greatest benefit to sero-discordant couples.
June 16th 2014
June 30th 2014