Malaria and deaths in the English marshes

Compounding vulnerabilities: Syndemics and the social determinants of disease in the past

OBJECTIVE

This article explores the theory and utility of a syndemic approach for the study of disease in the past. Syndemic principles are examined alongside other theoretical developments within bioarchaeology. Two case studies are provided to illustrate the efficacy of this approach: Tuberculosis and vitamin D deficiency in 18th and 19th century England, and malaria and helminth infections in Early Medieval England.

MATERIALS

Public health studies of present syndemics, in addition to published bioarchaeological, clinical and social information relating to the chosen case studies.

METHODS

The data from these two historical examples are revisited within a syndemic framework to draw deeper conclusions about disease clustering and heterogeneity in the past.

RESULTS

A syndemic framework can be applied to past contexts using clinical studies of diseases in a modern context and relevant paleopathological, archaeological, and historical data.

CONCLUSIONS

This approach provides a means for providing a deeper, contextualised understanding ancient diseases, and integrates well with extant theoretical tools in bioarchaeology SIGNIFICANCE: Syndemics provides scholars a deep-time perspective on diseases that still impact modern populations.

LIMITATIONS

Many of the variables essential for a truly syndemic approach cannot be obtained from current archaeological, bioarchaeological, or historical methods.

SUGGESTIONS FOR FURTHER RESEARCH

More detailed and in-depth analysis of specific disease clusters within the past and the present, which draws on a comprehensive analysis of the social determinants of health.

The changing risk patterns of Plasmodium vivax malaria in Greece due to climate change

It has great importance to study the potential effects of climate change on Plasmodium vivax malaria in Greece because the country can be the origin of the spread of vivax malaria to the northern areas. The potential lengths of the transmission seasons of Plasmodium vivax malaria were forecasted for 2041-2060 and 2061-2080 and were combined. The potential ranges were predicted by Climate Envelope Modelling Method. The models show moderate areal increase and altitudinal shift in the malaria-endemic areas in Greece in the future. The length of the transmission season is predicted to increase by 1 to 2 months, mainly in the mid-elevation regions and the Aegean Archipelago. The combined factors also predict the decrease of vivax malaria-free area in Greece. It can be concluded that rather the elongation of the transmission season will lead to an increase of the malaria risk in Greece than the increase in the suitability values.

Regional differences in the mid-Victorian diet and their impact on health

The aim of this study was to examine the impact of regional diets on the health of the poor in mid-Victorian Britain. Contemporary surveys of regional diets and living condition were reviewed. This information was compared with mortality data from Britain over the same period. Although there was an overall improvement in life expectancy during the latter part of the 19th century, there were large regional differences in lifestyle, diet and mortality rates. Dietary surveys showed that the poor labouring population in isolated rural areas of England, in the mainland and islands of Scotland and in the west of Ireland enjoyed the most nutritious diets. These regions also showed the lowest mortality rates in Britain. This was not simply the result of better sanitation and less mortality from food and waterborne infections but also fewer deaths from pulmonary tuberculosis, which is typically associated with better nutrition. These more isolated regions where a peasant-style culture provided abundant locally produced cheap foodstuffs such as potatoes, vegetables, whole grains, and milk and fish, were in the process of disappearing in the face of increasing urbanisation. This was to the detriment of many rural poor during the latter half of the century. Conversely, increasing urbanisation, with its improved transport links, brought greater availability and diversity of foods to many others. It was this that that led to an improved nutrition and life expectancy for the majority in urbanising Britain, despite the detrimental effects of increasing food refinement.

Plasmodium vivax Biology: Insights Provided by Genomics, Transcriptomics and Proteomics

During the last decade, the vast omics field has revolutionized biological research, especially the genomics, transcriptomics and proteomics branches, as technological tools become available to the field researcher and allow difficult question-driven studies to be addressed. Parasitology has greatly benefited from next generation sequencing (NGS) projects, which have resulted in a broadened comprehension of basic parasite molecular biology, ecology and epidemiology. Malariology is one example where application of this technology has greatly contributed to a better understanding of Plasmodium spp. biology and host-parasite interactions. Among the several parasite species that cause human malaria, the neglected Plasmodium vivax presents great research challenges, as in vitro culturing is not yet feasible and functional assays are heavily limited. Therefore, there are gaps in our P. vivax biology knowledge that affect decisions for control policies aiming to eradicate vivax malaria in the near future. In this review, we provide a snapshot of key discoveries already achieved in P. vivax sequencing projects, focusing on developments, hurdles, and limitations currently faced by the research community, as well as perspectives on future vivax malaria research.

Immunogenicity of the Plasmodium vivax merozoite surface protein 1 paralog in the induction of naturally acquired antibody and memory B cell responses

Background

The Plasmodium vivax merozoite surface protein 1 paralog (PvMSP1P-19) is a glycosylphosphatidylinositol (GPI)-anchored blood-stage protein that is expressed on the merozoite surface. It is proposed as a blood-stage vaccine candidate against P. vivax because of its ability to induce immune responses upon natural P. vivax exposure and in immunized animals. This study aimed to demonstrate the presence of inhibitory antibodies and memory B cell responses to the PvMSP1P-19 antigen during acute P. vivax infection and after recovery from infection.

Methods

To evaluate the antibody responses to PvMSP1P-19 during and after recovery from P. vivax infection, heparinized blood was collected from P. vivax-infected patients and recovered subjects to detect the total IgG response. The seropositive samples were defined into high and low responders, according to their optical density (OD) values obtained from ELISA. High responders were the subjects who had OD values above the OD of antisera from non-exposed controls plus 4× standard deviations, whereas low responders were the subjects who had OD values less than OD of antisera from non-exposed controls plus 4× standard deviations. The plasma from high and low responders were taken for testing the inhibitory activity against PvMSP1P-19-erythrocyte binding by in vitro EBIA. The sustainability of PvMSP1P-19-specific memory B cell responses after recovery from infection was analysed by ELISPOT.

Results

The anti-PvMSP1P-19 antibody levels were significantly higher in acutely infected P. vivax patients compared to healthy controls (P <  0.0001). Monitoring of the anti-PvMSP1P-19 antibody titre showed that the antibody was maintained for up to 9 months after recovery. Almost all high-responder groups strongly inhibited PvMSP1P-19 binding to erythrocytes, whereas no inhibition was shown in most low-responder samples. Interestingly, the inhibitory activity of the antibodies in some individuals from high-responder samples were stable for at least 12 months. The longevity of the antibody response was associated with the presence of PvMSP1P-19-specific memory B cells at 9 months after recovery from infection.

Conclusions

The PvMSP1P-19 antigen has immunogenicity during the induction of the antibody response, in which both the levels and inhibitory activity are maintained after the patient recovered from P. vivax infection. The maintenance of the antibody response was associated with the response of PvMSP1P-19-specific memory B cells. Therefore, the PvMSP1P-19 antigen should also be considered as a reliable vaccine candidate to develop a blood-stage vaccine against P. vivax.

Unsupervised primaquine for the treatment of Plasmodium vivax malaria relapses in southern Papua: A hospital-based cohort study

BACKGROUND

Primaquine is the only licensed drug for eradicating Plasmodium vivax hypnozoites and, therefore, preventing relapses of vivax malaria. It is a vital component of global malaria elimination efforts. Primaquine is efficacious when supervised in clinical trials, but its effectiveness in real-world settings is unknown. We aimed to determine whether unsupervised primaquine was effective for preventing re-presentation to hospital with vivax malaria in southern Papua, Indonesia.

METHODS AND FINDINGS

Routinely-collected hospital surveillance data were used to undertake a pragmatic comparison of the risk of re-presentation to hospital with vivax malaria in patients prescribed dihydroartemisinin-piperaquine (DHP) combined with primaquine versus those patients prescribed DHP alone. The omission of primaquine was predominantly due to 3 stock outages. Individual clinical, pharmacy, and laboratory data were merged using individual hospital identification numbers and the date of presentation to hospital. Between April 2004 and December 2013, there were 86,797 documented episodes of vivax malaria, of which 62,492 (72.0%) were included in the analysis. The risk of re-presentation with vivax malaria within 1 year was 33.8% (95% confidence Interval [CI] 33.1%-34.5%) after initial monoinfection with P. vivax and 29.2% (95% CI 28.1%-30.4%) after mixed-species infection. The risk of re-presentation with P. vivax malaria was higher in children 1 to <5 years of age (49.6% [95% CI 48.4%-50.9%]) compared to patients 15 years of age or older (24.2% [95% CI 23.4-24.9%]); Adjusted Hazard Ratio (AHR) = 2.23 (95% CI 2.15-2.31), p < 0.001. Overall, the risk of re-presentation was 37.2% (95% CI 35.6%-38.8%) in patients who were prescribed no primaquine compared to 31.6% (95% CI 30.9%-32.3%) in those prescribed either a low (≥1.5 mg/kg and <5 mg/kg) or high (≥5 mg/kg) dose of primaquine (AHR = 0.90 [95% CI 0.86-0.95, p < 0.001]). Limiting the comparison to high dose versus no primaquine in the period during and 12 months before and after a large stock outage resulted in minimal change in the estimated clinical effectiveness of primaquine (AHR 0.91, 95% CI 0.85-0.97, p = 0.003). Our pragmatic study avoided the clinical influences associated with prospective study involvement but was subject to attrition bias caused by passive follow-up.

CONCLUSIONS

Unsupervised primaquine for vivax malaria, prescribed according to the current World Health Organization guidelines, was associated with a minimal reduction in the risk of clinical recurrence within 1 year in Papua, Indonesia. New strategies for the effective radical cure of vivax malaria are needed in resource-poor settings.

Blood-feeding patterns of native mosquitoes and insights into their potential role as pathogen vectors in the Thames estuary region of the United Kingdom

BACKGROUND

The range of vertebrate hosts on which species of mosquito blood-feed is an important parameter for identifying potential vectors and in assessing the risk of incursion and establishment of vector-borne pathogens. In the United Kingdom, studies of mosquito host range have collected relatively few specimens and used techniques that could only broadly identify host species. This study conducted intensive collection and analysis of mosquitoes from a grazing marsh environment in southeast England. This site provides extensive wetland habitat for resident and migratory birds and has abundant human nuisance biting mosquitoes. The aim was to identify the blood-feeding patterns of mosquito species present at the site which could contribute to the transmission of pathogens.

METHODS

Twice-weekly collections of mosquitoes were made from Elmley Nature Reserve, Kent, between June and October 2014. Mosquitoes were collected using resting boxes, by aspiration from man-made structures and using a Mosquito Magnet Pro baited with 1-octen-3-ol. Blood-fed specimens were classified according to the degree of blood meal digestion using the Sella scale and vertebrate origin determined using sequencing of a fragment of the mitochondrial cytochrome C oxidase subunit I gene. Mosquitoes that were morphologically cryptic were identified to species level using multiplex PCR and sequencing methods.

RESULTS

A total of 20,666 mosquitoes of 11 species were collected, and 2,159 (10.4%) were blood-fed (Sella scale II-VI); of these 1,341 blood-fed specimens were selected for blood meal analysis. Vertebrate origin was successfully identified in 964 specimens (72%). Collections of blood-fed individuals were dominated by Anopheles maculipennis complex (73.5%), Culiseta annulata (21.2%) and Culex pipiens form pipiens (10.4%). Nineteen vertebrate hosts comprising five mammals and 14 birds were identified as hosts for mosquitoes, including two migratory bird species. Feeding on birds by Culex modestus and Anopheles atroparvus populations in England was demonstrated.

CONCLUSIONS

This study expands the vertebrate host range of mosquitoes in the Thames estuary region of the UK. Feeding on both resident and migratory bird species by potential arbovirus vectors including Cx. pipiens f. pipiens and Cx. modestus indicates the potential for enzootic transmission of an introduced arbovirus between migratory and local bird species by native mosquito species.

Could Plasmodium vivax malaria trigger malnutrition? Revisiting the Bradford Hill criteria to assess a causal relationship between two neglected problems

The benign characteristics formerly attributed to Plasmodium vivax infections have recently changed owing to the increasing number of reports of severe vivax malaria resulting in a broad spectrum of clinical complications, probably including undernutrition. Causal inference is a complex process, and arriving at a tentative inference of the causal or non-causal nature of an association is a subjective process limited by the existing evidence. Applying classical epidemiology principles, such as the Bradford Hill criteria, may help foster an understanding of causality and lead to appropriate interventions being proposed that may improve quality of life and decrease morbidity in neglected populations. Here, we examined these criteria in the context of the available data suggesting that vivax malaria may substantially contribute to childhood malnutrition. We found the data supported a role for P. vivax in the etiology of undernutrition in endemic areas. Thus, the application of modern causal inference tools, in future studies, may be useful in determining causation.

Seasonal dynamics and habitat specificity of mosquitoes in an English wetland: implications for UK wetland management and restoration

We engaged in field studies of native mosquitoes in a Cambridgeshire Fen, investigating a) the habitat specificity and seasonal dynamics of our native fauna in an intensively managed wetland, b) the impact of water-level and ditch management, and c) their colonization of an arable reversion to flooded grassland wetland expansion project. Studies from April to October, 2010 collected 14,000 adult mosquitoes (15 species) over 292 trap-nights and ∼4,000 pre-imaginal mosquitoes (11 species). Open floodwater species (Aedes caspius and Aedes cinereus, 43.3%) and wet woodland species (Aedes cantans/annulipes and Aedes rusticus, 32.4%) dominated, highlighting the major impact of seasonal water-level management on mosquito populations in an intensively managed wetland. In permanent habitats, managing marginal ditch vegetation and ditch drying significantly affect densities of pre-imaginal anophelines and culicines, respectively. This study presents the first UK field evidence of the implications of wetland expansion through arable reversion on mosquito colonization. Understanding the heterogeneity of mosquito diversity, phenology, and abundance in intensively managed UK wetlands will be crucial to mitigating nuisance and vector species through habitat management and biocidal control.

Mortality attributable to Plasmodium vivax malaria: a clinical audit from Papua, Indonesia

BACKGROUND

Plasmodium vivax causes almost half of all malaria cases in Asia and is recognised as a significant cause of morbidity. In recent years it has been associated with severe and fatal disease. The extent to which P. vivax contributes to death is not known.

METHODS

To define the epidemiology of mortality attributable to vivax malaria in southern Papua, Indonesia, a retrospective clinical records-based audit was conducted of all deaths in patients with vivax malaria at a tertiary referral hospital.

RESULTS

Between January 2004 and September 2009, hospital surveillance identified 3,495 inpatients with P. vivax monoinfection and 65 (1.9%) patients who subsequently died. Charts for 54 of these 65 patients could be reviewed, 40 (74%) of whom had pure P. vivax infections on cross-checking. Using pre-defined conservative criteria, vivax malaria was the primary cause of death in 6 cases, a major contributor in 17 cases and a minor contributor in a further 13 cases. Extreme anaemia was the most common primary cause of death. Malnutrition, sepsis with respiratory and gastrointestinal manifestations, and chronic diseases were the commonest attributed causes of death for patients in the latter two categories. There were an estimated 293,763 cases of pure P. vivax infection in the community during the study period giving an overall minimum case fatality of 0.12 per 1,000 infections. The corresponding case fatality in hospitalised patients was 10.3 per 1,000 infections.

CONCLUSIONS

Although uncommonly directly fatal, vivax malaria is an important indirect cause of death in southern Papua in patients with malnutrition, sepsis syndrome and chronic diseases, including HIV infection.

Plasmodium vivax: clinical spectrum, risk factors and pathogenesis

Vivax malaria was historically described as 'benign tertian malaria' because individual clinical episodes were less likely to cause severe illness than Plasmodium falciparum. Despite this, Plasmodium vivax was, and remains, responsible for major morbidity and significant mortality in vivax-endemic areas. Single infections causing febrile illness in otherwise healthy individuals rarely progress to severe disease. Nevertheless, in the presence of co-morbidities, P. vivax can cause severe illness and fatal outcomes. Recurrent or chronic infections in endemic areas can cause severe anaemia and malnutrition, particularly in early childhood. Other severe manifestations include acute lung injury, acute kidney injury and uncommonly, coma. Multiorgan failure and shock are described but further studies are needed to investigate the role of bacterial and other co-infections in these syndromes. In pregnancy, P. vivax infection can cause maternal anaemia, miscarriage, low birth weight and congenital malaria. Compared to P. falciparum, P. vivax has a greater capacity to elicit an inflammatory response, resulting in a lower pyrogenic threshold. Conversely, cytoadherence of P. vivax to endothelial cells is less frequent and parasite sequestration is not thought to be a significant cause of severe illness in vivax malaria. With a predilection for young red cells, P. vivax does not result in the high parasite biomass associated with severe disease in P. falciparum, but a four to fivefold greater removal of uninfected red cells from the circulation relative to P. falciparum is associated with a similar risk of severe anaemia. Mechanisms underlying the pathogenesis of severe vivax syndromes remain incompletely understood.

Assessing the future threat from vivax malaria in the United Kingdom using two markedly different modelling approaches

Background

The world is facing an increased threat from new and emerging diseases, and there is concern that climate change will expand areas suitable for transmission of vector borne diseases. The likelihood of vivax malaria returning to the UK was explored using two markedly different modelling approaches. First, a simple temperature-dependent, process-based model of malaria growth transmitted by Anopheles atroparvus, the historical vector of malaria in the UK. Second, a statistical model using logistic-regression was used to predict historical malaria incidence between 1917 and 1918 in the UK, based on environmental and demographic data. Using findings from these models and saltmarsh distributions, future risk maps for malaria in the UK were produced based on UKCIP02 climate change scenarios.

Results

The process-based model of climate suitability showed good correspondence with historical records of malaria cases. An analysis of the statistical models showed that mean temperature of the warmest month of the year was the major factor explaining the distribution of malaria, further supporting the use of the temperature-driven processed-based model. The risk maps indicate that large areas of central and southern England could support malaria transmission today and could increase in extent in the future. Confidence in these predictions is increased by the concordance between the processed-based and statistical models.

Conclusion

Although the future climate in the UK is favourable for the transmission of vivax malaria, the future risk of locally transmitted malaria is considered low because of low vector biting rates and the low probability of vectors feeding on a malaria-infected person.

The pathophysiology of vivax malaria

Long considered a benign infection, Plasmodium vivax is now recognized as a cause of severe and fatal malaria, despite its low parasite biomass, the increased deformability of vivax-infected red blood cells and an apparent paucity of parasite sequestration. Severe anemia is associated with recurrent bouts of hemolysis of predominantly uninfected erythrocytes with increased fragility, and lung injury is associated with inflammatory increases in alveolar-capillary membrane permeability. Although rare, vivax-associated coma challenges our understanding of pathobiology caused by Plasmodium spp. Host and parasite factors contribute to the risk of severe disease, and comorbidities might contribute to vivax mortality. In this review, we discuss potential mechanisms underlying the syndromes of uncomplicated and severe vivax malaria, identifying key areas for future research.

How human practices have affected vector-borne diseases in the past: a study of malaria transmission in Alpine valleys

Background

Malaria was endemic in the Rhône-Alpes area of eastern France in the 19^th century and life expectancy was particularly shortened in Alpine valleys. This study was designed to determine how the disease affected people in the area and to identify the factors influencing malaria transmission.

Methods

Demographic data of the 19^th century were collected from death registers of eight villages of the flood-plain of the river Isère. Correlations were performed between these demographic data and reconstructed meteorological data. Archive documents from medical practitioners gave information on symptoms of ill people. Engineer reports provided information on the hydraulic project developments in the Isère valley.

Results

Description of fevers was highly suggestive of endemic malaria transmission in the parishes neighbouring the river Isère. The current status of anopheline mosquitoes in the area supports this hypothesis. Mean temperature and precipitation were poorly correlated with demographic data, whereas the chronology of hydrological events correlated with fluctuations in death rates in the parishes.

Conclusion

Nowadays, most of the river development projects involve the creation of wet areas, enabling controlled flooding events. Flood-flow risk and the re-emergence of vector-borne diseases would probably be influenced by the climate change. The message is not to forget that human disturbance of any functioning hydrosystem has often been linked to malaria transmission in the past.