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Liu D.,Chinese Academy of Forestry | Liu D.,National Bird Banding Center | Xiao W.,Chinese Academy of Forestry | Lu J.,Chinese Academy of Forestry | And 2 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2011

Due to their flight ability and strong geographic dispersal, birds play important roles in the transmission and dissemination of infectous diseases. Since last century, a variety of infectious diseases such as avian cholera, avian tuberculosis, West Nile fever, avian influenza, and so on, have emerged and reemerged, and consequently have resulted in the death of numerous wild birds and poultry and as well as humans, and caused huge economic loss and serious social impact that have raised considerable concern. In this paper, the ecological character of infectious diseases and their impact on wild birds and humans, transmission of bird diseases, surveillance, early warning, prevention, and control of bird diseases, status and prospect of wildlife diseases surveillance, and prevention and control in China are reviewed. Bird diseases can be caused by an array of bacteria, viruses, fungi, parasites, and other pathogens. Different diseases are highly variable in the magnitude of losses, species affected, frequency of recurrence, and geographic spread following initial events. Diseases have been one of the seven biggest threats to global biodiversity since last century. They are causative of physical and physiological dysfunction as well as problems in breeding, behavior, and other aspects that influence the health of birds and reduce their survival ability. Diseases could cause mass death of individuals, resulting in serious impact on bird populations, especially those of endangered species. Some diseases may also impact on habitat selection and geographic distribution of birds. Moreover, birds are also involved in the dissemination of zoonoses that could infect livestock and humans, and affected birds may even be employed in biowarfare and bioterrorism deliberately. Because wild birds act as vectors for various diseases, their movement plays important roles in transmission of diseases. For example, wild birds are the natural vectors for low pathogenic avian influenza. Through direct contact or shedding dropping into soil, water, food, or other taints affected birds could transmit the virus to other birds and poultry periodically, and result in quick geographic dispersal of avian influenza. Birds can also make migrations carrying a variety of pathogens; bird migrations are closely related with outbreaks of many infectious diseases. Therefore the establishment of full-scale surveillance and early warning systems are of great importance for prevention and control of bird diseases. Passive surveillance is aimed at investigation of morbidity and mortality events and monitoring of sentinel species; active surveillance is aimed at early detection of diseases through sampling and testing of animal and environment. Based on these surveillance data, the OIE standard for risk assessment is a widely used method for risk analysis of animal diseases. The State Forestry Administration of China has established an epidemic diseases surveillance network since 2004; 717 cases of animal diseases involving 36, 538 individuals have been detected as of 2008, including the HPAI outbreak of wild birds at Qinghai Lake in 2005. However, we advocate establishment of more surveillance stations in Qinghai-Tibet area, development of related regulations and rules, enhancement of scientific support to the surveillance activities, and improvement of the capacities of local surveillance stations. Source


Liu D.,Chinese Academy of Forestry | Liu D.,National Bird Banding Center | Zhang G.,Chinese Academy of Forestry | Zhang G.,National Bird Banding Center | And 11 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2010

Bar-headed Goose Anser indicus is a large waterbird mainly inhabiting on plateau and migrating across a large geographic area. Understanding its biology and ecology is very crucial in prevention and control of avian influenza because this species is highly susceptible to and a potential transmitter for HPAI. Many studies have been carried out on this species at Qinghai Lake, a breeding ground, since the outbreak of HPAI on this species in 2005. Status of the wintering population of this species in Tibet, however, has not been documented well, although Yaluzangbu River basin of Tibet is one of the most important wintering areas in China. A population survey was conducted in this area in January, 2009, and 44657 Bar-headed geese were recorded, mostly in Linzhou, Rikaze, Bailang, Lazi, Jiangzi and Gongga, accounting for 22.8%, 21.9%, 11.8%, 11.2%,9.7% and 7.2% of the total number sighted, respectively. This number greatly exceeds 10081 Bar-headed geese surveyed in the same area in 1990s. Based on this survey and data of other wintering grounds, we estimated a current world population of at least 70000, comparing to 52000 - 60000 documented by the Wetlands International in 2002. The population distribution mainly depended on the availability of feeding areas, indicating food may be the most important factor for wintering Bar-headed goose. Winter habitats included winter wheat field, winter idle cropland, rivers & lakes, and marsh, with 72. 1% of the total observations recorded in winter idle cropland. Bar-headed goose spent the majority of time to feed in winter idle cropland and winter wheat field, and rested in rivers and lakes at noon and night. The flock size differed significantly among the four habitats, with the average of (208 ± 262) (n =215). Ten Bar-headed Geese were satellite tracked from Qinghai Lake from 2006 to 2008, three of whom successfully arrived at their wintering ground in Yaluzangbu River and Lasa River basins in Tibet of China, and Kohima of indian. The satellite tracking, together with traditional banding recovery outcome, reveals a close connection between the wintering population of these areas in Tibet and the breeding population at Qinghai Lake, therefore a high release risk of HPAI from Qinghai Lake may exist. Bar-headed geese spent (108 ±30) days (n =3) from Nov. to next Mar. in wintering ground, with the overall home range size of (122.22 ± 124.94) km2 (n = 3). The last stopover in fall migration was (103 ± 63) km (n = 3) away from the wintering ground, where the geese spent (14 ± 5) days (n = 3). In the same area, a large number of other waterbirds, including Ruddy Shelduck Tadorna ferruginea, Black-necked Crane Grus nigricollis, Mallard Anas platyrhynchos, Red-crested Pochard Rhodonessa rufina, and Common Pochard Aythya ferina, mostly HPAI H5N1 susceptible, were often seen feeding together with Bar-headed Geese. The Buddhism religion by the Tibetan people who expresses belief in the sacredness of all living creatures, in the wintering ground has contributed well to the conservation of wildlife. The combined crop farming with livestock grazing on the same agricultural areas, however, results in domestic animals commonly mingling in a feeding flock of Bar-headed Geese or vice versa in Tibet, increasing avian influenza virus transmission between them. Minimizing or totally stopping waterfowl-poultry & livestock-Human contact would be essential in HPAI surveillance and prevention. Source

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