The United States Department of Agriculture (USDA) has positivelyidentified the pathogenic form of avian flu--H5N1--in samples takenfrom birds last week in Mongolia by field veterinarians from theWildlife Conservation Society (WCS). It is the first instance of thisviral strain occurring in wild migratory birds with no apparent contactto domestic poultry or waterfowl.
Present in Mongolia for a health survey of wild bird populations inthe south and north of the country, WCS field vets Drs. William Kareshand Martin Gilbert responded to initial reports of the most recentavian influenza outbreak in Kovsgol Province near the Russian borderfrom the Mongolian Ministry of Food and Agriculture, which conductedpreliminary testing of birds that died at Erkhel Lake. Their findingcoincided with confirmations of cases of avian influenza in Russia andKazakhstan. Karesh and Gilbert immediately traveled to the site with ateam of Mongolian virologists, veterinarians, and public healthofficials. Approximately 100 dead birds were found at the site.
The team--including personnel from WCS, the Mongolian National Academyof Sciences, the Mongolian Institute of Veterinary Medicine, the StateCentral Veterinary Laboratory, Ministry of Food and AgricultureVeterinary Department, and the Ministry of Health Mongolian Center ofCommunicable Diseases with Natural Foci--collected samples fromhundreds of wild birds, both live and dead including, ruddy shelduck,herring gull, black-headed gull, bar-headed goose, whooper swan, andEurasian wigeon that are all at risk for contracting the virus.
Recent reports of influenza outbreaks in wild birds in China and Russiahave failed to put die-offs in perspective with the numbers ofunaffected birds, thus there was no way to assess the impact. The WCSteam at Erkhel Lake in Mongolia collected this information for thefirst time. Overall, over 6,500 apparently healthy birds of 55 specieswere observed on the lake. The percentage of sick or dead birds wasminiscule according to Gilbert following the survey, suggesting thateither the virus had little effect on the birds or that very few wereactually infected by the bug. Early results suggest that it may be thelatter.
Supported by the U.N.'s Food and Agriculture Organization (F.A.O.), theteam has sent the samples (774 in total) to the U.S.D.A.'s PoultryResearch Laboratory in Athens, Georgia, for further testing todetermine whether this virus is the H5N1 strain that has killed over 50people in Southeast Asia and more than 5,000 wild birds in westernChina. As of today, preliminary tests from one dead whooper swancollected in Mongolia have shown the presence of the H5N1 strain ofAvian Influenza using RT-PCR, while results from 30 live whooper swansliving at the same site and also a nearby lake were negative for thevirus. Samples collected from other live birds at the two sites,including sixty ruddy shelducks, twenty-four bar-headed geese, andtwenty-five black-headed gulls, were found to be negative for thevirus.
Whereas prior outbreaks in wild birds have happened either in closeproximity to infected domestic poultry and waterfowl, or in regionswhere such contact could not be excluded, Mongolia's paucity ofdomestic poultry suggests a new vector of avian flu. Finding the H5N1strain during this expedition suggests that while the highly pathogenicavian influenza can be carried across long distances, the waterfowlspecies typically identified in recent outbreaks appear to be victimsrather than effective carriers of the disease.
The multidisciplinary, collaborative response to this latest outbreakreflects the WCS One World-One Health approach to making informed,multidisciplinary decisions on global health crises that intersecthuman, wildlife, and livestock health. WCS experts are warning that tocontain this potential epidemic, prevention activities must includebetter management practices in farms, especially those that are smalland open-air, where domestic poultry and waterfowl are allowed tointermingle with wild birds. Officials would also need to monitorwildlife markets, where wild and domesticated species are kept in closeproximity, and risk exposure to a wide range of pathogens.
Wildlife and health experts, including the F.A.O., maintain thatindiscriminate culling of wild migratory bird populations would beineffective in preventing the spread of avian flu. "Focusing ourlimited resources on the hubs and activities where humans, livestock,and wildlife come into close contact," says Dr. William Karesh,Director of WCS's Field Veterinary Program, who lead the WCS team inMongolia, is "the best hope for successfully preventing the spread ofavian flu and protecting both people and animals."
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