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Understanding the link between malaria risk and climate.

ABSTRACT: The incubation period for malaria parasites within the mosquito is exquisitely temperature-sensitive, so that temperature is a major determinant of malaria risk. Epidemiological models are increasingly used to guide allocation of disease control resources and to assess the likely impact of climate change on global malaria burdens. Temperature-based malaria transmission is generally incorporated into these models using mean monthly temperatures, yet temperatures fluctuate throughout the diurnal cycle. Here we use a thermodynamic malaria development model to demonstrate that temperature fluctuation can substantially alter the incubation period of the parasite, and hence malaria transmission rates. We find that, in general, temperature fluctuation reduces the impact of increases in mean temperature. Diurnal temperature fluctuation around means >21 degrees C slows parasite development compared with constant temperatures, whereas fluctuation around <21 degrees C speeds development. Consequently, models which ignore diurnal variation overestimate malaria risk in warmer environments and underestimate risk in cooler environments. To illustrate the implications further, we explore the influence of diurnal temperature fluctuation on malaria transmission at a site in the Kenyan Highlands. Based on local meteorological data, we find that the annual epidemics of malaria at this site cannot be explained without invoking the influence of diurnal temperature fluctuation. Moreover, while temperature fluctuation reduces the relative influence of a subtle warming trend apparent over the last 20 years, it nonetheless makes the effects biologically more significant. Such effects of short-term temperature fluctuations have not previously been considered but are central to understanding current malaria transmission and the consequences of climate change.

SUBMITTER: Paaijmans KP

PROVIDER: S-EPMC2720408 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The United Nation's sustainable development goal for 2030 is to eradicate the global malaria epidemic, primarily as the disease continues to be one of the major concerns for public health in sub-Saharan Africa. In 2015, the region accounted for 90% of malaria deaths. Mozambique recorded a malaria mortality rate of 42.75 (per 100,000). In Chimoio, Mozambique's fifth largest city, malaria is the fourth leading cause of death (9.4%). Few data on malaria mortality exists in Mozambique, particularly in relation to Chimoio. The objective of this study was to characterize malaria mortality trends and its spatial distribution in Chimoio.Malaria mortality data and climate data were extracted from the Chimoio Civil Registration records, and the Regional Weather station, from 2010 to 2014. The malaria crude mortality rate was calculated. ANOVA, Tukey's, Chi square, and time series were carried out and an intervention analysis ARIMA model developed.A total of 944 malaria death cases were registered in Chimoio, 729 of these among Chimoio residents (77%). The average malaria mortality by gender was 44.9% for females and 55.1% for males. The age of death varied from 0 to 96 years, with an average age of 25.9 (SE = 0.79) years old. January presented the highest average of malaria deaths, and urban areas presented a lower crude malaria mortality rate. Rural neighbourhoods with good accessibility present the highest malaria crude mortality rate, over 85 per 100,000. Seasonal ARMA (2,0)(1,0)12 fitted the data although it was not able to capture malaria mortality peaks occurring during malaria outbreaks. Intervention effect properly fit the mortality peaks and reduced ARMA's root mean square error by almost 25%.Malaria mortality is increasing in Chimoio; children between 1 and 4 years old represent 13% of Chimoio population, but account for 25% of malaria mortality. Malaria mortality shows seasonal and spatial characteristics. More studies should be carried out for malaria eradication in the municipality.

Project description:BackgroundDue to low vaccination uptake and measles outbreaks across Europe, public health authorities have paid increasing attention to anthroposophic communities. Public media outlets have further described these communities as vaccine refusers or "anti-vaxxers". The aim of this review was to understand the scope of the problem and explore assumptions about vaccination beliefs in anthroposophic communities. For the purpose of this review, we define anthroposophic communities as people following some/certain views more or less loosely connected to the philosophies of anthroposophy. The systematic review addresses three research questions and (1) collates evidence documenting outbreaks linked to anthroposophic communities, (2) literature on vaccination coverage in anthroposophic communities, and (3) lastly describes literature that summarizes theories and factors influencing vaccine decision-making in anthroposophic communities.MethodsThis is a systematic review using the following databases: Medline, Web of Science, Psycinfo, and CINAHL. Double-blinded article screening was conducted by two researchers. Data was summarized to address the research questions. For the qualitative research question the data was analysed using thematic analysis with the assistance of Nvivo12.0.ResultsThere were 12 articles documenting 18 measles outbreaks linked to anthroposophic communities between the years 2000 and 2012. Seven articles describe lower vaccination uptake in anthroposophic communities than in other communities, although one article describes that vaccination coverage in low-income communities with a migrant background was lower than in the anthroposophic community they studied. We found eight articles examining factors and theories influencing vaccine decision making in anthroposophic communities. The qualitative analysis revealed four common themes. Firstly, there was a very broad spectrum of vaccine beliefs among the anthroposophic communities. Secondly, there was a consistent narrative about problems or concerns with vaccines, including toxicity and lack of trust in the system. Thirdly, there was a strong notion of the importance of making individual and well-informed choices as opposed to simply following the masses. Lastly, making vaccine choices different from public health guidelines was highly stigmatized by those outside of the anthroposophic community but also those within the community.ConclusionContinuing to further knowledge of vaccine beliefs in anthroposophic communities is particularly important in view of increasing measles rates and potential sudden reliance on vaccines for emerging diseases. However, popular assumptions about vaccine beliefs in anthroposophic communities are challenged by the data presented in this systematic review.

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Understanding the link between malaria risk and climate.

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