Human activities link fruit bat presence to Ebola virus disease outbreaks

1. A significant link between forest loss and fragmentation and outbreaks of Ebola virus disease (EVD) in humans has been documented. Deforestation may alter the natural circulation of viruses and change the composition, abundance, behaviour and possibly viral exposure of reservoir species. This in turn might increase contact between infected animals and humans.
2. Fruit bats of the family Pteropodidae have been suspected as reservoirs of the Ebola virus. At present, the only evidence associating fruit bats with EVD is the presence of seropositive individuals in eight species and polymerase chain reaction-positive individuals in three of these.
3. Our study investigates whether human activities can increase African fruit bat geographical ranges and whether this influence overlaps geographically with EVD outbreaks that, in turn, are favoured by deforestation.
4. We use species observation records for the 20 fruit bat species found in favourable areas for the Ebola virus to determine factors affecting the bats' range inside the predicted Ebola virus area. We do this by employing a hypothetico-deductive approach based on favourability modelling.
5. We show that the range of some fruit bat species is linked to human activities within the favourable areas for the Ebola virus. More specifically, the areas where human activities favour the presence of five fruit bat species overlap with the areas where EVD outbreaks in humans were themselves favoured by deforestation. These five species are as follows: Eidolon helvum, Epomops franqueti, Megaloglossus woermanni, Micropteropus pusillus and Rousettus aegyptiacus. Of these five, all but Megaloglossus woermanni have recorded seropositive individuals. For the remaining 15 bat species, we found no biogeographical support for the hypothesis that positive human influence on fruit bats could be associated with EVD outbreaks in deforested areas within the tropical forest biome in West and Central Africa.
6. Our work is a useful first step allowing further investigation of the networks and pathways that may lead to an EVD outbreak. The modelling framework we employ here can be used for other emerging infectious diseases.

     

The natural history of Ebola virus in Africa

Several countries spanning the equatorial forest regions of Africa have had outbreaks of Ebola hemorrhagic fever over the last three decades. This article is an overview of the many published investigations of how Ebola virus circulates in its natural environment, focusing on the viral reservoir, susceptible animal species, environmental conditions favoring inter-species transmission, and how the infection is transmitted to humans. Major breakthroughs have been made in recent years but many outstanding questions must be dealt with if we are to prevent human outbreaks by interfering with the viral life cycle.     

埃博拉病毒/埃博拉病—2014

2014年2月,死亡率极高的埃博拉病(EVD)开始在西部非洲的几内亚暴发流行,接下来,暴发流行出现在塞拉利昂、利比里亚、尼日利亚和塞内加尔另四个西部非洲的国家。现在,几内亚、利比里亚和塞拉利昂的疫情最重。迄今为止,已有4 784人患EVD,且人数仍在倍增,这次暴发流行已成为自40年前EVD被发现以来规模最大的一次,已形成了波及其他地区和国家的巨大危险。在此,综述2014年EVD暴发流行的起因,埃博拉病毒(EBOV)及其传播,EVD的诊断治疗,EBOV疫苗的研制以及EBOV感染的防控。     

Ebola virus disease: a highly fatal infectious disease reemerging in West Africa

Ebolavirus can cause a highly fatal and panic-generating human disease which may jump from bats to other mammals and human. High viral loads in body fluids allow efficient transmission by contact. Lack of effective antivirals, vaccines and public health infrastructures in parts of Africa make it difficult to health workers to contain the outbreak.     

Modelling chestnut biogeography for American chestnut restoration

Aim Chestnuts (Castanea spp.) are ecologically and economically important species. We studied the general biology, distribution and climatic limits of seven chestnut species from around the world. We provided climatic matching of Asiatic species to North America to assist the range‐wide restoration of American chestnut [C. dentata (Marsh.) Borkh.] by incorporating blight‐resistant genes from Asiatic species. Location North America, Europe and East Asia. Methods General chestnut biology was reviewed on the basis of published literature and field observations. Chestnut distributions were established using published range maps and literature. Climatic constraints were analysed for the northern and southern distribution limits and the entire range for each species using principal component analysis (PCA) of fourteen bioclimatic variables. Climatic envelope matching was performed for three Chinese species using Maxent modelling to predict corresponding suitable climate zones for those species in North America. Results Chestnuts are primarily distributed in the warm‐temperate and subtropical zones in the northern hemisphere. PCA results revealed that thermal gradient was the primary control of chestnut distribution. Climatic spaces of different species overlap with one another to different degrees, but strong similarities are shown especially between Chinese species and American species. Climatic envelope matching suggested that large areas in eastern North America have a favourable climate for Chinese species. Main conclusions The general biological traits and climatic limits of the seven chestnut species are very similar. The predictions of Chinese species climatic range corresponded with most of the historical American chestnut range. Thus, a regionally adapted, blight‐resistant, introgressed hybrid American chestnut appears feasible if a sufficiently diverse array of Chinese chestnut germplasm is used as a source of blight resistance. Our study provided a between‐continent climate matching approach to facilitate the range‐wide species restoration, which can be readily applied in planning the restoration of other threatened or endangered species.     

The biogeography of the Anura of sub-equatorial Africa and the prioritisation of areas for their conservation

There is an increasing need for protected areas to conserve biodiversity efficiently. The Anura of sub-equatorial Africa have received little attention, but we quantitatively analyse a database containing presence-only data for anurans of sub-equatorial Africa to determine patterns of distribution and species richness, and discuss the roles of present and past environmental conditions in shaping these patterns. We consider the distribution of areas rich in endemic, range-restricted and Red Data Book (RDB) species to identify areas of significance to conservation. The Eastern Highlands of Zimbabwe and adjacent area in Mozambique, southeastern Malawi and the northern coast of KwaZulu/Natal are particularly species rich, whereas the southwestern Cape of South Africa and northwestern Zambia exhibit high degrees of endemism. Four major biogeographical sub-regions are identified, which can be further subdivided into provinces. All statistically significant, current environmental factors together account for 52.6% of species richness. Annual maximum rainfall, soil type variation, minimum temperature and range of elevation were all positively correlated with species richness. Thus, both habitat influences and history appear to have influenced patterns of anuran richness in the region. Generally, areas of high species richness coincide with those high in range-restricted, endemic and RDB species. In South Africa, the northeastern coast and southwestern Cape are hypothesised to have been both refugia and centres of speciation. Results suggest that the current reserve system in sub-equatorial Africa is inadequate for the conservation of the full complement of anuran species in the region.     

Evaluating Subcriticality during the Ebola Epidemic in West Africa

The 2014–2015 Ebola outbreak is the largest and most widespread to date. In order to estimate ongoing transmission in the affected countries, we estimated the weekly average number of secondary cases caused by one individual infected with Ebola throughout the infectious period for each affected West African country using a stochastic hidden Markov model fitted to case data from the World Health Organization. If the average number of infections caused by one Ebola infection is less than 1.0, the epidemic is subcritical and cannot sustain itself. The epidemics in Liberia and Sierra Leone have approached subcriticality at some point during the epidemic; the epidemic in Guinea is ongoing with no evidence that it is subcritical. Response efforts to control the epidemic should continue in order to eliminate Ebola cases in West Africa.     

埃博拉病毒及其致病机制

自2014年2~3月,西非埃博拉病毒感染的暴发流行已呈播散趋势,受到世界卫生组织的高度重视。我国也提高了防止埃博拉病毒进入国内的警示,并采取了相应措施。现将有关埃博拉病毒的生物学特性、致病机制及相关流行病学与防治策略作简要综述,供参考。     

A simple mathematical model for Ebola in Africa

We deal with the following question: Can the consumption of contaminated bush meat, the funeral practices and the environmental contamination explain the recurrence and persistence of Ebola virus disease outbreaks in Africa? We develop an SIR-type model which, incorporates both the direct and indirect transmissions in such a manner that there is a provision of Ebola viruses. We prove that the full model has one (endemic) equilibrium which is locally asymptotically stable whereas, it is globally asymptotically stable in the absence of the Ebola virus shedding in the environment. For the sub-model without the provision of Ebola viruses, the disease dies out or stabilizes globally at an endemic equilibrium. At the endemic level, the number of infectious is larger for the full model than for the sub-model without provision of Ebola viruses. We design a nonstandard finite difference scheme, which preserves the dynamics of the model. Numerical simulations are provided.     

Parapatric species and the implications for climate change studies: a case study on hares in Europe

Parapatry is a biogeographical term used to refer to organisms whose ranges do not overlap, but are immediately adjacent to each other; they only co‐occur – if at all – in a narrow contact zone. Often there are no environmental barriers in the contact zones, hence competitive interaction is usually advocated as the factor that modulates species distribution ranges. Even though the effects of climate change on species distribution have been widely studied, few studies have explored these effects on the biogeographical relationships between closely related, parapatric, species. We modelled environmental favourability for three parapatric hare species in Europe – Lepus granatensis, L. europaeus and L. timidus – using ecogeographical variables and projected the models into the future according to the IPCC A2 emissions scenario. Favourabilities for present and future scenarios were combined using fuzzy logic with the following aims: (i) to determine the biogeographical relationships between hare species in parapatry, that is L. granatensis/L. europaeus and L. europaeus/L. timidus and (ii) to assess the effects of climate change on each species as well as on their interspecific interactions. In their contact area L. granatensis achieved higher favourability values than L. europaeus, suggesting that if both species have a similar population status, the former species may have some advantages over the latter if competitive relationships are established. Climate change had the most striking effect on the distribution of L. timidus, especially when interspecific interactions with L. europaeus were taken into account, which may compromise the co‐existence of L. timidus. The results of this study are relevant not only for understanding the distribution patterns of the hares studied and the effects of climate change on these patterns, but also for improving the general application of species distribution models to the prediction of the effects of climate change on biodiversity.     

Simulating tick distributions over sub-Saharan Africa: the use of observed and simulated climate surfaces

Aim A broad suit of climate data sets is becoming available for use in predictive species modelling. We compare the efficacy of using interpolated climate surfaces [Center for Resource and Environmental Studies (CRES) and Climate Research Unit (CRU)] or high‐resolution model‐derived climate data [Division of Atmospheric Research limited‐area model (DARLAM)] for predictive species modelling, using tick distributions from sub‐Saharan Africa. Location The analysis is restricted to sub‐Saharan Africa. The study area was subdivided into 3000 grids cells with a resolution of 60 × 60 km. Methods Species distributions were predicted using an established multivariate climate envelope modelling approach and three very different climate data sets. The recorded variance in the climate data sets was quantified by employing omnidirectional variograms. To further compare the interpolated tick distributions that flowed from using three climate data sets, we calculated true positive (TP) predictions, false negative (FN) predictions as well as the proportional overlaps between observed and modelled tick distributions. In addition, the effect of tick data set size on the performance of the climate data sets was evaluated by performing random draws of known tick distribution records without replacement. Results The predicted distributions were consistently wider ranging than the known records when using any of the three climate data sets. However, the proportional overlap between predicted and known distributions varied as follows: for Rhipicephalus appendiculatus Neumann (Acari: Ixodidae), these were 60%, 60% and 70%; for Rhipicephalus longus Neumann (Acari: Ixodidae) 60%, 57% and 75%; for Rhipicephalus zambeziensis Walker, Norval & Corwin (Acari: Ixodidae) 57%, 51% and 62%, and for Rhipicephalus capensis Koch (Acari: Ixodidae) 70%, 60% and 60% using the CRES, CRU and DARLAM climate data sets, respectively. All data sets were sensitive to data size but DARLAM performed better when using smaller species data sets. At a 20% data subsample level, DARLAM was able to capture more than 50% of the known records and captured more than 60% of known records at higher subsample levels. Main conclusions The use of data derived from high‐resolution nested climate models (e.g. DARLAM) provided equal or even better species distribution modelling performance. As the model is dynamic and process based, the output data are available at the modelled resolution, and are not hamstrung by the sampling intensity of observed climate data sets (c. one sample per 30,000 km² for Africa). In addition, when exploring the biodiversity consequences of climate change, these modelled outputs form a more useful basis for comparison with modelled future climate scenarios.     

Moss biogeography in the Tasman Sea region

Abstract

Panbiogeographic track analysis is applied to the distribution of several groups of mosses which occur in the New Zealand region. The analysis highlights areas of biogeographic interest (nodes) in the New Zealand region as follows: 1. New Guinea, 2. New Caledonia, 3. New South Wales/Queensland border in Australia, 4. northern New Zealand, 5. Rapa Island, 6. subantarctic New Zealand.

New Zealand is connected to these nodes by the following standard tracks: 1. New Guinea—New South Wales/Queensland border—Tasmania—subantarctic New Zealand, 2. New Guinea—New Caledonia—New Zealand—subantarctic New Zealand, 3. a central Tasman Sea transversal track; New South Wales/Queensland border—New Caledonia. Rapa Island is connected to the Tasman region by northern New Zealand and New Caledonia.     

Distribution Patterns of Indigenous Freshwater Fishes in the Tagus River Basin, Spain

Classification and ordination methods used to examine the internal complexity of the Mediterranean Tagus River catchment based on fish distribution revealed that it is not a homogeneous biogeographical unit. The indigenous fishes analyzed in this study are distributed through the basin forming geographical communities (chorotypes), some of which are associated with environmental factors like river morphology, water quality or geographical location. Nevertheless, 40% of the variation in species occurrence remains unexplained by either environmental or geographical variables, suggesting that historical factors may influence the freshwater fish distribution patterns. Three main biogeographical areas, delimited by significant boundaries, were identified. Two of them are identified as the upper and the middle-lower basins of the Tagus River catchment; the third corresponds to the Alagón River and seems to be linked to historical factors of the catchment.