Chevonne Reynolds

In search of a treatment for HIV – current therapies and the role of non-nucleoside reverse transcriptase inhibitors (NNRTIs)

The human immunodeficiency virus (HIV) causes AIDS (acquired immune deficiency syndrome), a disease in which the immune system progressively deteriorates, making sufferers vulnerable to all manner of opportunistic infections. Currently, world-wide there are estimated to be 34 million people living with HIV, with the vast majority of these living in sub-Saharan Africa. Therefore, an important research focus is development of new drugs that can be used in the treatment of HIV/AIDS. This review gives an overview of the disease and addresses the drugs currently used for treatment, with specific emphasis on new developments within the class of allosteric non-nucleoside reverse transcriptase inhibitors (NNRTIs).

A social–ecological approach to landscape epidemiology: geographic variation and avian influenza

ContextLandscape structure influences host–parasite–pathogen dynamics at multiple scales in space and time. Landscape epidemiology, which connects disease ecology and landscape ecology, is still an emerging field.ObjectiveWe argue that landscape epidemiology must move beyond simply studying the influence of landscape configuration and composition on epidemiological processes and towards a more comparative, systems approach that better incorporates social–ecological complexity.MethodsWe illustrate our argument with a detailed review, based on a single conceptual systems model, of geographic variation in drivers of avian influenza in Western Europe, Southeast Asia, and Southern Africa.ResultsOur three study regions are similar in some ways but quite different in others. The same underlying mechanisms apply in all cases, but differences in the attributes of key components and linkages (most notably avian diversity, the abiotic environment, land use and land cover, and food production systems) create significant differences in avian influenza virus prevalence and human risk between regions.ConclusionsLandscape approaches can connect local- and continental-scale elements of epidemiology. Adopting a landscape-focused systems perspective on the problem facilitates the identification of the most important commonalities and differences, guiding both science and policy, and helps to identify elements of the problem on which further research is needed. More generally, our review demonstrates the importance of social–ecological interactions and comparative approaches for landscape epidemiology.

The role of waterbirds in the dispersal of freshwater cladocera and bryozoa in southern Africa

It has long been presumed that waterbirds disperse the propagules of aquatic organisms. However, it is only in recent years that this claim has been empirically explored and little is still known about waterbird-mediated dispersal in southern Africa. Aquatic invertebrates are thought to be well adapted to dispersal by waterbirds because of their ability to produce hardy resting eggs. We explored the capacity of waterbirds to disperse the eggs of both cladocera and bryozoans via endo- and ectozoochory. We examined 283 faecal samples and 394 feather brushings from six waterbird species and two wetland sites in South Africa for the presence of diapausing eggs. A total of 108 intact diaspores were recovered, with intact eggs present in 16% and 7% of the faecal samples and feather brushings, respectively. Our results indicate that southern African waterbirds do take up the resting eggs of aquatic invertebrates and that these eggs can survive intact through the gut or remain attached to the feathers. These results provide evidence that waterbirds may be important vectors for aquatic invertebrates in southern Africa and imply that waterbirds may play a vital role in maintaining connectivity between invertebrate populations in isolated wetland patches.

Grassland Bird Response to Vegetation Structural Heterogeneity and Clearing of Invasive Bramble

Spatial and temporal patterns of disturbance and the subsequent heterogeneity are critical in maintaining biodiversity within grassland ecosystems. Grassland birds have evolved within this ‘shifting mosaic’ to become reliant on specific habitat characteristics maintained under varying levels of both natural and anthropogenic disturbance. Unfortunately, grasslands in South Africa have been extensively transformed and remain poorly conserved, threatening grassland avifauna. Mistbelt grassland is a threatened vegetation type endemic to the province of KwaZulu-Natal, of which only 0.3% is formally protected. This study investigated seasonal and patch type heterogeneity in a Mistbelt grassland avian community by determining avian community structure and composition in four patch types, i.e. i) untransformed open grassland, ii) burnt grassland, iii) bramble-invaded and, iv) bramble-cleared grassland, during winter and summer. Avian assemblages were significantly different between the different patch types for each season. The bramble patch type negatively affected grassland bird species diversity. Bramble-cleared grassland and untransformed grassland had similar vegetation structure and avian communities in the summer, suggesting that the grassland bird community benefitted soon after the clearing of invasive vegetation. This study provides further evidence that bird diversity is enhanced in structurally heterogeneous grassland landscapes. Furthermore, the protection and appropriate management of privately owned Mistbelt grassland, conserved in the form of rangeland, is an important refuge for threatened and endemic avifauna, such as the globally-threatened blue swallow (Hirundo atrocaerulea) and wattled crane (Bugeranus carunculatus).

Inconsistent effects of landscape heterogeneity and land-use on animal diversity in an agricultural mosaic: a multi-scale and multi-taxon investigation

ContextThe landscape heterogeneity hypothesis states that increased heterogeneity in agricultural landscapes will promote biodiversity. However, this hypothesis does not detail which components of landscape heterogeneity (compositional or configurational) most affect biodiversity and how these compare to the effects of surrounding agricultural land-use.ObjectivesOur objectives were to: (1) assess the influence of the components of structural landscape heterogeneity on taxonomic diversity; and (2) compare the effects of landscape heterogeneity to those of different types of agricultural land-use in the same landscape across different taxonomic groups.MethodsWe identified a priori independent gradients of compositional and configurational landscape heterogeneity within an agricultural mosaic of north-eastern Swaziland. We tested how bird, dung beetle, ant and meso-carnivore richness and diversity responded to compositional and configurational heterogeneity and agricultural land-use across five different spatial scales.ResultsCompositional heterogeneity best explained species richness in each taxonomic group. Bird and ant richness were both positively correlated with compositional heterogeneity, whilst dung beetle richness was negatively correlated. Commercial agriculture positively influenced bird species richness and ant diversity, but had a negative influence on dung beetle richness. There was no effect of either component of heterogeneity on the combined taxonomic diversity or richness at any spatial scale.ConclusionsOur results suggest that increasing landscape compositional heterogeneity and limiting the negative effects of intensive commercial agriculture will foster diversity across a greater number of taxonomic groups in agricultural mosaics. This will require the implementation of different strategies across landscapes to balance the contrasting influences of compositional heterogeneity and land-use. Strategies that couple large patches of core habitat across broader scales with landscape structural heterogeneity at finer scales could best benefit biodiversity.

Micro-plastic ingestion by waterbirds from contaminated wetlands in South Africa

Despite a large literature on the impacts of micro-plastic pollution in marine ecosystems, very little research has focused on these pollutants in freshwater ecosystems. Recently, however, a few studies have demonstrated that micro-plastic pollutants are ingested by freshwater taxa, including birds. To explore this potential environmental threat in African freshwater systems we quantified micro-plastic pollutants in the faeces and feather brushings of seven southern African duck species. We analysed 283 faecal samples and 408 feather brushings, and found that 5% of faecal samples and 10% of feather samples contained micro-plastic fibres. The presence and abundance of micro-fibres differed between sampling sites, with significantly higher amounts recorded for the site that received effluent from a sewage treatment facility. Additionally, micro-fibre presence differed across duck species, indicating that foraging behaviour affects plastic ingestion. Our study confirms that African freshwater ecosystems and the biodiversity they support are under threat from micro-plastic contamination.

Dung beetle richness decreases with increasing landscape structural heterogeneity in an African savanna-agricultural mosaic

The landscape heterogeneity hypothesis posits that increasing variance of land cover types in agricultural landscapes will increase landscape level biodiversity. This hypothesis, however, does not detail which component of landscape structural heterogeneity, compositional (the type and amount) or configurational (the shape and arrangement) has the greatest influence on biodiversity and at what spatial scale(s). We investigated how dung beetle (Scarabaeidae) alpha‐diversity responded to landscape structural heterogeneity at a variety of spatial scales in an agricultural mosaic‐landscape in north‐eastern Swaziland. We also compared the effect of these components to the effect of variation in the amounts of major land‐cover types in the landscape and plot level vegetation structure. We used pitfall traps to sample the dung beetle community along a gradient of heterogeneity and used linear mixed effects models to compare the effect of each component on dung beetle richness and Shannon diversity at four separate spatial scales (i.e. 1‐,1.5‐, 2‐ & 3‐km). Land‐cover diversity and number of patches represented compositional and configurational landscape heterogeneity respectively. Landscape compositional heterogeneity was negatively correlated with dung beetle richness at the 1.5‐km and 2‐km spatial scales. The percentage savanna in the landscape was positively correlated with dung beetle richness at the 3‐km and 2‐km scales. Landscape level heterogeneity may enhance diversity of some taxonomic groups, but this was not the case for dung beetles in a southern African savanna. The best way to maintain their diversity is to create or maintain large continuous blocks of savanna while limiting intensive agriculture.

A framework for testing assumptions about foraging scales, body mass, and niche separation using telemetry data

Abstract Ecological theory predicts that if animals with very similar dietary requirements inhabit the same landscape, then they should avoid niche overlap by either exploiting food resources at different times or foraging at different spatial scales. Similarly, it is often assumed that animals that fall in different body mass modes and share the same body plan will use landscapes at different spatial scales. We developed a new methodological framework for understanding the scaling of foraging (i.e. the range and distribution of scales at which animals use their landscapes) by applying a combination of three well‐established methods to satellite telemetry data to quantify foraging patch size distributions: (1) first‐passage time analysis; (2) a movement‐based kernel density estimator; and (3) statistical comparison of resulting histograms and tests for multimodality. We demonstrate our approach using two sympatric, ecologically similar species of African ducks with quite different body masses: Egyptian Geese (actually a shelduck), and Red‐billed Teal. Contrary to theoretical predictions, the two species, which are sympatric throughout the year, foraged at almost identical spatial scales. Our results show how ecologists can use GPS tracking data to explicitly quantify and compare the scales of foraging by different organisms within an animal community. Our analysis demonstrates both a novel approach to foraging data analysis and the need for caution when making assumptions about the relationships among niche separation, diet, and foraging scale.

Susceptibility and Status of Avian Influenza in Ostriches

SUMMARY. The extensive nature of ostrich farming production systems bears the continual risk of point introductions of avian influenza virus (AIV) from wild birds, but immune status, management, population density, and other causes of stress in ostriches are the ultimate determinants of the severity of the disease in this species. From January 2012 to December 2014, more than 70 incidents of AIV in ostriches were reported in South Africa. These included H5N2 and H7N1 low pathogenicity avian influenza (LPAI) in 2012, H7N7 LPAI in 2013, and H5N2 LPAI in 2014. To resolve the molecular epidemiology in South Africa, the entire South African viral repository from ostriches and wild birds from 1991 to 2013 (n = 42) was resequenced by next-generation sequencing technology to obtain complete genomes for comparison. The phylogenetic results were supplemented with serological data for ostriches from 2012 to 2014, and AIV-detection data from surveillance of 17 762 wild birds sampled over the same period. Phylogenetic evidence pointed to wild birds, e.g., African sacred ibis (Threskiornis aethiopicus), in the dissemination of H7N1 LPAI to ostriches in the Eastern and Western Cape provinces during 2012, in separate incidents that could not be epidemiologically linked. In contrast, the H7N7 LPAI outbreaks in 2013 that were restricted to the Western Cape Province appear to have originated from a single-point introduction from wild birds. Two H5N2 viruses detected in ostriches in 2012 were determined to be LPAI strains that were new introductions, epidemiologically unrelated to the 2011 highly pathogenic avian influenza (HPAI) outbreaks. Seventeen of 27 (63%) ostrich viruses contained the polymerase basic 2 (PB2) E627K marker, and 2 of the ostrich isolates that lacked E627K contained the compensatory Q591K mutation, whereas a third virus had a D701N mutation. Ostriches maintain a low upper- to midtracheal temperature as part of their adaptive physiology for desert survival, which may explain the selection in ratites for E627K or its compensatory mutations—markers that facilitate AIV replication at lower temperatures. An AIV prevalence of 5.6% in wild birds was recorded between 2012 and 2014, considerably higher than AIV prevalence for the southern African region of 2.5%–3.6% reported in the period 2007–2009. Serological prevalence of AI in ostriches was 3.7%, 3.6%, and 6.1% for 2012, 2013, and 2014, respectively. An annual seasonal dip in incidence was evident around March/April (late summer/autumn), with peaks around July/August (mid to late winter). H5, H6, H7, and unidentified serotypes were present at varying levels over the 3-yr period.

Landscape heterogeneity shapes taxonomic diversity of non-breeding birds across fragmented savanna landscapes

There is an ongoing need to integrate agricultural production with wildlife conservation to maintain biodiversity, especially in developing countries. The landscape heterogeneity hypothesis identifies a potential means for promoting biodiversity in agricultural landscapes by emphasizing that increasing heterogeneity can increase biodiversity. However, the importance of landscape heterogeneity relative to habitat amount and vegetation structure is poorly understood, particularly regarding the relative importance of different components of landscape heterogeneity. We investigated how taxonomic, functional, and phylogenetic diversity of non-breeding birds responded to two components of landscape heterogeneity, compositional and configurational heterogeneity, and compared the importance of the landscape heterogeneity hypothesis relative to the habitat amount hypothesis and vegetation structural heterogeneity hypothesis. To do so, we conducted point counts at 80 plots across 16 landscapes during June–July 2016 in northeastern Swaziland, a sub-tropical savanna. We found a positive effect of landscape heterogeneity on taxonomic diversity, but no effect of habitat amount or vegetation structure. In contrast to taxonomic diversity, we found a positive trend between the amount of savanna habitat and phylogenetic diversity. In agricultural mosaics in subtropical savannas, conservation value may be created if landscape compositional heterogeneity, landscape configurational heterogeneity, and large areas of habitat are incorporated into land planning. Our findings show that it is important to use multiple measures of diversity in conjunction with various landscape and habitat measures when designing conservation management strategies.