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Article in English | IMSEAR | ID: sea-162670


In this paper, we examine the association between climate change and outbreak probability of Highly Pathogenic Avian Influenza A virus (HPAI H5N1) in birds. Climate change is a potential factor for the recent spread of H5N1 outbreaks because it can directly alter the conditions involved in persistence of the virus and disease transmission. Also it can contribute indirectly by changing wild bird migration patterns. Econometric analyses using a dynamic Probit model over monthly data from January 2004 to December 2008 found that a 1% rise in winter total precipitation increases the risk of HPAI H5N1 outbreaks by 0.26%. Spring mean temperature was also found to have positive and significant impacts. Our findings are robust across different model specifications and under out-of-sample tests. Using historical data we find the realized climate change of the last 20 years partly explains the recent expansion in outbreaks. Under future climate change projections, we find that countries having higher projected spring temperature or more winter precipitation or both, such as Japan and Romania, will have large increases in outbreak probabilities. This suggests that climate change may play an even greater role in the future, although magnitudes will vary across countries and climate projections. From a policy perspective, future climate conditions may give rise to a need for different disease control and prevention strategies.

Rev. biol. trop ; 60(supl.3): 67-81, nov. 2012. ilus, graf, mapas, tab
Article in English | LILACS-Express | LILACS | ID: lil-672084


Two methods for selecting a subset of simulations and/or general circulation models (GCMs) from a set of 30 available simulations are compared: 1) Selecting the models based on their performance on reproducing 20th century climate, and 2) random sampling. In the first case, it was found that the performance methodology is very sensitive to the type and number of metrics used to rank the models and therefore the results are not robust to these conditions. In general, including more models in a multi-model ensemble according to their rank (of skill in reproducing 20th century climate) results in an increase in the multi-model skill up to a certain point and then the inclusion of more models degrades the skill of the multi-model ensemble. In a similar fashion when the models are introduced in the ensemble at random, there is a point where the inclusion of more models does not change significantly the skill of the multi-model ensemble. For precipitation the subset of models that produces the maximum skill in reproducing 20th century climate also showed some skill in reproducing the climate change projections of the multi-model ensemble of all simulations. For temperature, more models/simulations are needed to be included in the ensemble (at the expense of a decrease in the skill of reproducing the climate of the 20th century for the selection based on their ranks). For precipitation and temperature the use of 7 simulations out of 30 resulted in the maximum skill for both approaches to introduce the models.

Se emplearon dos métodos para escoger un subconjunto a partir de treinta simulaciones de Modelos de Circulación General. El primer método se basó en la habilidad de cada uno de los modelos en reproducir el clima del siglo XX y el segundo en un muestreo aleatorio. Se encontró que el primero de ellos es muy sensible al tipo y métrica usada para categorizar los modelos, lo que no arrojó resultados robustos bajo estas condiciones. En general, la inclusión de más modelos en el agrupamiento de multi-modelos ordenados de acuerdo a su destreza en reproducir el clima del siglo XX, resultó en un aumento en la destreza del agrupamiento de multi-modelos hasta cierto punto, y luego la inclusión de más modelos/simulaciones degrada la destreza del agrupamiento de multi-modelos. De manera similar, en la inclusión de modelos de forma aleatoria, existe un punto en que agregar más modelos no cambia significativamente la destreza del agrupamiento de muti-modelos. Para el caso de la precipitación, el subconjunto de modelos que produce la máxima destreza en reproducir el clima del siglo XX también mostró alguna destreza en reproducir las proyecciones de cambio climático del agrupamiento de multi-modelos para todas las simulaciones. Para temperatura, más modelos/simulaciones son necesarios para ser incluidos en el agrupamiento (con la consecuente disminución en la destreza para reproducir el clima del siglo XX). Para precipitación y temperatura, el uso de 7 simulaciones de 30 posibles resultó en el punto de máxima destreza para ambos métodos de inclusión de modelos.

Rev. biol. trop ; 60(supl.3): 83-112, nov. 2012. ilus, graf
Article in Spanish | LILACS-Express | LILACS | ID: lil-672085


Different climate change scenarios were revised and compared for Cocos Island National Park, Costa Rica. They were generated using different tools (MAGICC/SCENGEN, PRECIS and SDSM) and for the 2080 (2070-2099) time slice. Results shown in general a high dependence with the General Circulation Model, the downscaling technique and the socioeconomic scenario used. All scenarios presented an increase in mean and variance of the air surface temperature annual cycle. That result is also consistent with a future global warming scenario. Results for rainfall are different among each other. Most of the scenarios show an increase in the mean annual rainfall accumulation. However, it is not possible to establish a clear trend when annual variability is considered, mainly because almost all of the scenarios studied projected an increase in the annual rainfall accumulates.

Se revisaron y compararon escenarios de cambio climáticos utilizando distintas técnicas (MAGICC/SCEN- GEN, PRECIS and SDSM) con el objetivo de evaluar posibles cambios de temperatura y precipitación en el Parque Nacional Isla del Coco, Costa Rica, para el horizonte temporal del 2080 (2070-2099). Los resultados reflejan una dependencia importante con el Modelo de Circulación General, el método de ajuste de escala y con el escenario socio-económico usado. Los escenarios obtenidos reflejan un aumento en la media y la varianza del ciclo anual de la temperatura superficial del aire, siendo consistentes con un calentamiento global futuro. Los resultados para la precipitación difieren entre sí. Se observó que la mayoría de los escenarios analizados proyectan aumentos en al acumulado medio del ciclo anual, sin embargo, al considerar su variabilidad, no fue posible establecer una tendencia clara hacia un aumento o una disminución, debido principalmente a que casi todos los escenarios estudiados proyectan un incremento en la variabilidad del acumulado anual de la precipitación.

Article in English | IMSEAR | ID: sea-135087


Background: Many studies have reported the occurrence of lethal acute renal failure after snakebites. Bungarus candidus (Malayan krait) is a medically important venomous snake distributed widely throughout Southeast Asia. The best known features of systemic envenoming by B. candidus are neurotoxic. Objective: Obtain more information on effects of B. candidus venom on changes in systemic and renal hemodynamics in experimental animals. Methods: Twelve adult male New Zealand white rabbits were used to study the effect of B. candidus venom on general circulation and renal hemodynamics. An anesthetized animal was intravenously injected with B. candidus venom at a dosage of 50μg/kg bodyweight. All changes of parameters were observed after initial post venom injection and recorded at 30 min intervals until 150 minutes after envenomation. Results: After envenomation, cardiovascular responses showed a marked decrease in mean arterial pressure within two minutes, afterwards gradually returning closely to baseline values. There were stepwise decreases in heart rate and cardiac output, while total peripheral resistance was slightly increased. The renal hemodynamics significantly decreased by glomerular filtration rate, effective renal plasma flow and effective renal blood flow, while the filtration fraction significantly increased. Envenomed animals showed a reduction in renal fraction, while renal vascular resistance stepwise increased. The plasma potassium level tended to increase. Animals showed stepwise decreases in urinary excretion of Na+, K+ and Cl-. A marked decrease in plasma calcium level was apparent at 120 minutes, while plasma creatine phosphokinase and lactate dehydrogenase levels increased at 30-120 minutes. Conclusion: A significant drop in blood pressure was attributed to a sustained fall in cardiac output, which would be associated with a reduction in heart rate. Sustained hypotension would contribute to reduction of renal blood flow, which results in decreased GFR.