Socioeconomic and behavior risk factors of human alveolar echinococcosis in Tibetan communities in Sichuan, People's Republic of China.
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Data from two cross-sectional investigations on 7,138 subjects were used to explore risk factors of human alveolar echinococcosis (AE) in Tibetan communities. The overall human AE prevalence was 3.1% (223 of 7,138), females had a higher prevalence (3.6%, 132 of 3,713) than males (2.7%, 91 of 3,425; P = 0.011), and herdsmen had a higher prevalence (5.2%, 154 of 2,955) than farmers (1.8%, 12 of 661; P < 0.001) and urban populations (2.1%, 49 of 2,360; P < 0.001). Age in all populations, number of dogs kept, fox skin ownership in farmers, not preventing flies from landing on food in herdsmen, using open streams as drinking water sources, and playing with dogs in urban populations were statistically significant risk factors. The results suggest that AE is highly endemic in the eastern Tibetan plateau, in Sichuan Province, the role of the dog is important for human infection, and other factors associated with environmental contamination may vary according to structure and practices of communities. (+info)
Pasture types and Echinococcus multilocularis, Tibetan communities.
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Our study showed that open pastures had more small mammal burrows than fenced pastures in Tibetan pastoralist communities in 2003. This characteristic was linked to a higher prevalence of Echinococcus multilocularis in dogs and indicates that pasture type may affect E. multilocularis transmission. (+info)
Dangerous journey: documenting the experience of Tibetan refugees.
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OBJECTIVES: Since the 1950 invasion of Tibet by China, Tibetan refugees have attempted to flee into Nepal over the Himalayan mountains. We documented the experiences of a group of refugees making this journey. METHODS: We conducted semistructured interviews with 50 recent refugees at the Tibetan Refugee Transit Centre in Kathmandu, Nepal. RESULTS: Participants ranged in age from 8 to 56 years, and 21 were female. The average length of their journey from Tibet to Nepal was 34 days. During their journey, a majority of the refugees encountered authorities or became involved in altercations with Nepali Maoist groups. Most of these interactions resulted in extortion and threats of expulsion. Several Tibetans were tortured, beaten with weapons, threatened with being shot, and robbed. Three women were sexually assaulted at gunpoint. CONCLUSIONS: The refugees who took part in this study experienced physical and mental hardships and, often, human rights abuses on their journey to Nepal. International pressure is needed to prevent human rights violations and reduce potential long-term physical and mental health effects associated with this dangerous crossing. (+info)
Impact of overgrazing on the transmission of Echinococcus multilocularis in Tibetan pastoral communities of Sichuan Province, China.
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BACKGROUND: Overgrazing was assumed to increase the population density of small mammals that are the intermediate hosts of Echinococcus multilocularis, the pathogen of alveolar echinococcosis in the Qinghai Tibet Plateau. This research tested the hypothesis that overgrazing might promote Echinococcus multilocularis transmission through increasing populations of small mammal, intermediate hosts in Tibetan pastoral communities. METHODS: Grazing practices, small mammal indices and dog Echinococcus multilocularis infection data were collected to analyze the relation between overgrazing and Echinococcus multilocularis transmission using nonparametric tests and multiple stepwise logistic regression. RESULTS: In the investigated area, raising livestock was a key industry. The communal pastures existed and the available forage was deficient for grazing. Open (common) pastures were overgrazed and had higher burrow density of small mammals compared with neighboring fenced (private) pastures; this high overgrazing pressure on the open pastures measured by neighboring fenced area led to higher burrow density of small mammals in open pastures. The median burrow density of small mammals in open pastures was independently associated with nearby canine Echinococcus multilocularis infection (P = 0.003, OR = 1.048). CONCLUSION: Overgrazing may promote the transmission of Echinococcus multilocularis through increasing the population density of small mammals. (+info)
The Himalayas as a directional barrier to gene flow.
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High-resolution Y-chromosome haplogroup analyses coupled with Y-short tandem repeat (STR) haplotypes were used to (1) investigate the genetic affinities of three populations from Nepal--including Newar, Tamang, and people from cosmopolitan Kathmandu (referred to as "Kathmandu" subsequently)--as well as a collection from Tibet and (2) evaluate whether the Himalayan mountain range represents a geographic barrier for gene flow between the Tibetan plateau and the South Asian subcontinent. The results suggest that the Tibetans and Nepalese are in part descendants of Tibeto-Burman-speaking groups originating from Northeast Asia. All four populations are represented predominantly by haplogroup O3a5-M134-derived chromosomes, whose Y-STR-based age (+/-SE) was estimated at 8.1+/-2.9 thousand years ago (KYA), more recent than its Southeast Asian counterpart. The most pronounced difference between the two regions is reflected in the opposing high-frequency distributions of haplogroups D in Tibet and R in Nepal. With the exception of Tamang, both Newar and Kathmandu exhibit considerable similarities to the Indian Y-haplogroup distribution, particularly in their haplogroup R and H composition. These results indicate gene flow from the Indian subcontinent and, in the case of haplogroup R, from Eurasia as well, a conclusion that is also supported by the admixture analysis. In contrast, whereas haplogroup D is completely absent in Nepal, it accounts for 50.6% of the Tibetan Y-chromosome gene pool. Coalescent analyses suggest that the expansion of haplogroup D derivatives--namely, D1-M15 and D3-P47 in Tibet--involved two different demographic events (5.1+/-1.8 and 11.3+/-3.7 KYA, respectively) that are more recent than those of D2-M55 representatives common in Japan. Low frequencies, relative to Nepal, of haplogroup J and R lineages in Tibet are also consistent with restricted gene flow from the subcontinent. Yet the presence of haplogroup O3a5-M134 representatives in Nepal indicates that the Himalayas have been permeable to dispersals from the east. These genetic patterns suggest that this cordillera has been a biased bidirectional barrier. (+info)
Maternal and neonatal outcomes of hospital vaginal deliveries in Tibet.
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INTRODUCTION: To determine the outcomes of vaginal deliveries in three study hospitals in Lhasa, Tibet Autonomous Region (TAR), People's Republic of China (PRC), at high altitude (3650 m). METHODS: Prospective observational study of 1121 vaginal deliveries. RESULTS: Pre-eclampsia/gestational hypertension (PE/GH) was the most common maternal complication 18.9% (n=212), followed by postpartum hemorrhage (blood loss > or = 500 ml) 13.4%. There were no maternal deaths. Neonatal complications included: low birth weight (10.2%), small for gestational age (13.7%), pre-term delivery (4.1%) and low Apgar (3.7%). There were 11 stillbirths (9.8/1000 live births) and 19 early neonatal deaths (17/1000 live births). CONCLUSION: This is the largest study of maternal and newborn outcomes in Tibet. It provides information on the outcomes of institutional vaginal births among women delivering infants at high altitude. There was a higher incidence of PE/GH and low birth weight; rates of PPH were not increased compared to those at lower altitudes. (+info)
Two routes to functional adaptation: Tibetan and Andean high-altitude natives.
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Populations native to the Tibetan and Andean Plateaus are descended from colonizers who arrived perhaps 25,000 and 11,000 years ago, respectively. Both have been exposed to the opportunity for natural selection for traits that offset the unavoidable environmental stress of severe lifelong high-altitude hypoxia. This paper presents evidence that Tibetan and Andean high-altitude natives have adapted differently, as indicated by large quantitative differences in numerous physiological traits comprising the oxygen delivery process. These findings suggest the hypothesis that evolutionary processes have tinkered differently on the two founding populations and their descendents, with the result that the two followed different routes to the same functional outcome of successful oxygen delivery, long-term persistence and high function. Assessed on the basis of basal and maximal oxygen consumption, both populations avail themselves of essentially the full range of oxygen-using metabolism as populations at sea level, in contrast with the curtailed range available to visitors at high altitudes. Efforts to identify the genetic bases of these traits have included quantitative genetics, genetic admixture, and candidate gene approaches. These reveal generally more genetic variance in the Tibetan population and more potential for natural selection. There is evidence that natural selection is ongoing in the Tibetan population, where women estimated to have genotypes for high oxygen saturation of hemoglobin (and less physiological stress) have higher offspring survival. Identifying the genetic bases of these traits is crucial to discovering the steps along the Tibetan and Andean routes to functional adaptation. (+info)
Higher blood flow and circulating NO products offset high-altitude hypoxia among Tibetans.
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The low barometric pressure at high altitude causes lower arterial oxygen content among Tibetan highlanders, who maintain normal levels of oxygen use as indicated by basal and maximal oxygen consumption levels that are consistent with sea level predictions. This study tested the hypothesis that Tibetans resident at 4,200 m offset physiological hypoxia and achieve normal oxygen delivery by means of higher blood flow enabled by higher levels of bioactive forms of NO, the main endothelial factor regulating blood flow and vascular resistance. The natural experimental study design compared Tibetans at 4,200 m and U.S. residents at 206 m. Eighty-eight Tibetan and 50 U.S. resident volunteers (18-56 years of age, healthy, nonsmoking, nonhypertensive, not pregnant, with normal pulmonary function) participated. Forearm blood flow, an indicator of systemic blood flow, was measured noninvasively by using plethysmography at rest, after breathing supplemental oxygen, and after exercise. The Tibetans had more than double the forearm blood flow of low-altitude residents, resulting in greater than sea level oxygen delivery to tissues. In comparison to sea level controls, Tibetans had >10-fold-higher circulating concentrations of bioactive NO products, including plasma and red blood cell nitrate and nitroso proteins and plasma nitrite, but lower concentrations of iron nitrosyl complexes (HbFeIINO) in red blood cells. This suggests that NO production is increased and that metabolic pathways controlling formation of NO products are regulated differently among Tibetans. These findings shift attention from the traditional focus on pulmonary and hematological systems to vascular factors contributing to adaptation to high-altitude hypoxia. (+info)