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The East African : December 23rd 2013
The EastAfrican 32 OUTLOOK DECEMBER 21-27,2013 S CI E N C E Why animals are infecting humans more Many zoonoses are attributable to human actions that have changed the environments By A SPECIAL CORRRESPONDENT IRIN M ore than half of all human infections originate in animals and experts say a multi-sectoral, global response to zoonoses — diseases passing between animals and humans — is urgently needed. With almost half of the 1,000 pathogen species found in livestock and pets able to cross over to humans, poor animal health increases the risk of poor human health. Known zoonoses cause an esti- mated 2.3 billion cases of sickness and 1.7 million human deaths annually, according to the Nairobi-based International Livestock Research Institute (ILRI). Scientists say preventing and con- taining zoonoses requires improved human and animal health surveillance systems, food safety and biodiversity conservation and collaboration among biologists, veterinarians and doctors for people. Many zoonoses (70 per cent of which come from wildlife) are attributable to human actions that have changed the environments, decreasing animals’ resilience against infection and increasing the risk of sickness of humans falling ill. “Changes in farming and mar- keting systems have led to more and more pathogens present in society that human beings have never previously been exposed to,” Yi Guan, the medical doctor and virologist based in Hong Kong who first traced the 2003 outbreak of Severe Acute Respiratory Syndrome (SARS) to live poultry markets in eastern China, told IRIN. The planet’s population is expect- ed to exceed nine billion people by 2050, leading to more pressure on environmental resources and food WAY FORWARD FAO and WHO urge joint campaigns. For example, in 2000, Chad’s Ministries of Livestock and Health joined forces to carry out vaccination campaigns for pastoralists and their animals, resulting, for the first time, in 10 per cent of nomadic children under the age of one being fully immunised wherever the joint campaign was conducted. Major surveillance systems to be based in countries with high wildlife biodiversity and population density (“hotspots for emerging infectious disease”). “Changes in farming and marketing systems have led to more pathogens.” Yi Guan, virologist who traced SARS to live poultry markets in China systems. By that time, the UN Food and Agriculture Organisation (FAO) estimates global meat consumption per person will increase 27 per cent. “Urbanisation is [linked] to the intensification of animal systems [in cities], leading to an increased risk of zoonosis,” said Fred Unger, a Preventing and containing zoonoses requires improved human and animal health surveillance systems. Picture: File veterinary scientist with ILRI. While there are health benefits to moving animal husbandry into cities and slums, there are also zoonotic pathogens brewing in the unhealthy physical conditions animals are kept in, increasing humans’ exposure to those pathogens. Expanding industrialisation, such as extractive industries, frequently establish worker camps in virgin forests, exposing wildlife to people for the first time, said Kaia Tombak, a conservation programme assistant at Wildlife Conservation Society Canada. Development-induced habitat loss is another contributing factor to zoonoses, say biologists. The Nipah virus — a potentially fatal disease with respiratory symptoms that can infect the brain — emerged in Malaysia in the late 1990s, when people destroyed massive sections of rainforest, the natural habitat of fruit bats, in order to build pig farms and cultivate orchards. Researchers theorise that as bats, carriers of the virus, came into closer contact for the first time with densely populated pig farms, they infected a number of pigs, which then infected humans. About 75 per cent of people infected died. Yet, cross-infection can be prevented in these cases, said Tombak. Camps for extractive industries based in forested areas can install screens to prevent bats from roosting indoors and establish responsible waste disposal practices to prevent attracting wild animals to camps, she suggested. Warming temperatures are also a threat. Edward Allen, a research scientist at the Laos Institute for Renewable Energy, based in Vientiane, has noted that even moderate temperature dips and rises within 10 degrees Celsius can lead to more deaths in both groups. These temperature changes kill thousands of animals annually, and can damage surviving animals’ fertility and milk production — affecting human nutrition — according to FAO. Could cutting down some t≥ees help cool the planet? By LENNY BERNSTEIN Washington Post-Bloomberg MILLIONS OF acres of forest are wiped out every year, cut down to make room for agriculture and, increasingly, urban growth, mostly in developing nations. Such deforestation is a major contributor of carbon dioxide to the atmosphere, responsible for 17 per cent of the heat-trapping greenhouse gases that are warming the planet, according to the Environmental Protection Agency. But now two Dartmouth College research- ers are suggesting that in some limited circumstances, the cooling value of an open, snowy field may be greater than the climate benefits that a stand of trees can provide — and that it is possible to calculate where that might be the case. In the short term, they say, such knowledge would be useful in forestry management. In the longer term, nations with vast expanses of snow fields that reflect heat back into space might seek to be credited for contribution to reducing global warming. “In some cases, the cooling influence of albedo can equal and surpass the climatic benefits of carbon sequestration from forest growth,” post-doctoral fellow David Lutz and professor of environmental studies Richard Howarth wrote in their paper. Albedo is the reflectivity of the earth’s surface, the amount of solar energy it sends back into space. White surfaces, such as snow, send back more of this shortwave radiation than dark surfaces, such as green, leafy forests. What that means, in a practical sense, is that when managers are trying to determine when to harvest trees, they might want to account for the benefits of the open field they will leave behind. In places where snow remains on the ground for considerable lengths of time and trees grow slowly, limiting the amount of carbon they can take in, it might make sense to take down trees sooner rather than later and leave fields unplanted longer. “In spruce-fir stands, very short rotation periods of just 25 years become economically optimal when albedo is considered,” Lutz and Howarth wrote. They noted that there is a body of research that shows that cutting down boreal forests can produce “net climatic benefits.” But the pair stressed that their work should not be construed as support for heavy cutting of trees or deforestation. Enough: Soap and water. Pic: File Just how safe a≥e soaps that kill bacte≥ia? By BRIAN CLARK HOWARD The New York Times Syndicate US FEDERAL officials’ questions about antibacterial soaps have raised a lather among environmental and consumer advocates concerned about the safety of controversial ingredients in these cleansers. Reviving a long-running con- troversy over antibacterial soaps and body wash, the US Food and Drug Administration (FDA) announced that the makers of such products will have to prove that they are more effective than plain soap and water in preventing illness and curtailing infection. According to the agency an- nouncement, manufacturers will also need to prove that their products are safe for long-term use. “Our goal is, if a company is making a claim that something is antibacterial and in this case promoting the concept that consumers who use these products can prevent the spread of germs, then there ought to be data behind that,” said Sandra Kweder of the FDA’s Centre for Drug Evaluation and Research, in a statement. Alluding to the controversy around the most common active ingredients in thousands of antibacterial soap products - triclosan (liquid soaps) and triclocarban (bar soaps) — the FDA said, “Further, some data suggest that longterm exposure to certain active ingredients used in antibacterial products could pose health risks, such as bacterial resistance or hormonal effects.” The move comes more than a decade after antibacterial soaps were established on store shelves; one 2001 survey found 45 per cent of soaps contained these antibacterial agents, which act to inhibit or kill off bacteria. Such soaps have been used to kill off odour-causing bacteria since the 1920s, according to the American Cleaning Institute, an industry group. In 2005, an FDA antibacterial soap panel had called for more research on the safety of antibacterial products.
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