David Hayman | Massey University (original) (raw)

Papers by David Hayman

BMJ Global Health, 2023

Global health requires evidence-based approaches to improve health and decrease inequalities. In ... more Global health requires evidence-based approaches to improve health and decrease inequalities. In a roundtable discussion between health practitioners, funders, academics and policy-makers, we recognised key areas for improvement to deliver better-informed, sustainable and equitable global health practices. These focus on considering information-sharing mechanisms and developing evidence-based frameworks that take an adaptive function-based approach, grounded in the ability to perform and respond to prioritised needs. Increasing social engagement as well as sector and participant diversity in whole-of-society decision-making, and collaborating with and optimising on hyperlocal and global regional entities, will improve prioritisation of global health capabilities. Since the skills required to navigate drivers of pandemics, and the challenges in prioritising, capacity building and response do not sit squarely in the health sector, it is essential to integrate expertise from a broad range of fields to maximise on available knowledge during decision-making and system development. Here, we review the current assessment tools and provide seven discussion points for how improvements to implementation of evidence-based prioritisation can improve global health.

Parasitology, 2020

Parasites sometimes expand their host range and cause new disease aetiologies. Genetic changes ca... more Parasites sometimes expand their host range and cause new disease aetiologies. Genetic changes can then occur due to host-specific adaptive alterations, particularly when parasites cross between evolutionarily distant hosts. Characterizing genetic variation in
Cryptosporidium from humans and other animals may have important implications for understanding disease dynamics and transmission. We analyse sequences from four loci (gp60, HSP-70, COWP and actin) representing multiple Cryptosporidium species reported in humans. We predicted low genetic diversity in species that present unusual human infections due to founder events and bottlenecks. High genetic diversity was observed in isolates from humans of C. meleagridis, C. cuniculus, C. hominis and C. parvum. A deviation of expected values of neutrality using Tajima’s D was observed in C. cuniculus and C. meleagridis. The
high genetic diversity in C. meleagridis and C. cuniculus did not match our expectations but deviations from neutrality indicate a recent decrease in genetic variability through a population bottleneck after an expansion event. Cryptosporidium hominis was also found with a significant Tajima’s D positive value likely caused by recent population expansion of unusual genotypes in humans. These insights indicate that changes in genetic diversity can help us to understand host-parasite adaptation and evolution.

Journal of Applied Microbiology, 2020

Aim The aim of our study was to assess the presence and risk of waterborne pathogens in the drink... more Aim
The aim of our study was to assess the presence and risk of waterborne pathogens in the drinking water of outdoor facilities in New Zealand and track potential sources of microbial contamination in water sources.

Methods and results
A serial cross‐sectional study with a risk‐based sample collection strategy was conducted at 15 public campgrounds over two summer seasons (2011–2012 and 2012–2013). Drinking water supplied to these campgrounds was not compliant with national standards, based on Escherichia coli as an indicator organism, in more than half of the sampling occasions. Campylobacter contamination of drinking water at the campgrounds was likely to be of wild bird origin. Faecal samples from rails (pukeko and weka) were 35 times more likely to return a Campylobacter‐positive result compared to passerines. Water treatment using ultraviolet (UV) irradiation or a combination of filtration and UV irradiation or chemicals was more likely to result in water that was compliant with the national standards than water from a tap without any treatment. The use of filters alone was not associated with the likelihood of compliance.

Conclusions
Providing microbiologically safe drinking water at outdoor recreational facilities is imperative to avoid gastroenteritis outbreaks. This requires an in‐depth understanding of potential sources of contamination in drinking water sources and the installation of adequate water treatment facilities.

Significance and Impact of the Study
Our study provides evidence that drinking water without treatment or filter‐only treatment in public campgrounds is unlikely to comply with national standards for human consumption and extra water treatment measures such as UV irradiation or chemical treatment are needed.

Rabies virus kills tens of thousands of people globally each year, especially in resource-limited... more Rabies virus kills tens of thousands of people globally each year, especially in resource-limited countries. Yet, there are genetically-and antigenically-related lyssaviruses, all capable of causing the disease rabies, circulating globally among bats without causing conspicuous disease outbreaks. The species richness and greater genetic diversity of African lyssa-viruses, along with the lack of antibody cross-reactivity among them, has led to the hypothesis that Africa is the origin of lyssaviruses. This hypothesis was tested using a probabilistic phylogeographical approach. The nucleoprotein gene sequences from 153 representatives of 16 lyssavirus species, collected between 1956 and 2015, were used to develop a phylo-genetic tree which incorporated relevant geographic and temporal data relating to the viruses. In addition, complete genome sequences from all 16 (putative) species were analysed. The most probable ancestral distribution for the internal nodes was inferred using three different approaches and was confirmed by analysis of complete genomes. These results support a Palearctic origin for lyssaviruses (posterior probability = 0.85), challenging the 'out of Africa' hypothesis, and suggest three independent transmission events to the Afrotropical region, representing the three phylogroups that form the three major lyssavirus clades. Rabies virus kills tens of thousands of people globally each year and causes indescribable misery and family disturbance, especially in developing countries. Yet in much of the world there are related viruses, called lyssaviruses, which circulate among bats without causing conspicuous outbreaks. The greater diversity of African lyssaviruses has led to the hypothesis that Africa is the origin of these viruses. To test this hypothesis, the genetic data from 153 representative viruses from 16 available lyssavirus species from across the world dated between 1956 and 2015 were analysed. Statistical models were used to reconstruct the historical processes that lead to the contemporary distribution of these viruses.

ABSTRACT Background/Question/Methods . Rabies is an acute viral infection that is invariably fata... more ABSTRACT Background/Question/Methods . Rabies is an acute viral infection that is invariably fatal in humans, and globally causes over 55000 human deaths per annum. Models of rabies virus (RABV) dynamics have concentrated on terrestrial mammal systems (e.g., dogs, raccoons and foxes). However, the vast majority of lyssaviruses, of which RABV is only one, have bats as their reservoir hosts and phylogenetic analyses suggest RABV originated from bats. Additionally, lyssaviruses such as Lagos bat virus (LBV), which circulates in African bats, are phenotypically divergent enough from RABV that current vaccines are not protective. Given the potential for spillover and infection emergence of such viruses, and that bats are reservoirs for numerous emerging zoonotic viruses, understanding mechanisms which allow these infections to be maintained within bat populations is important to understand spillover and infection emergence into new populations. A study of RABV in big brown bats (Eptesicus fuscus) in Colorado used a mathematical model to determine that life history patterns, such as seasonally variable mortality rates including reduced mortality during hibernation, allow for rabies virus maintenance in temperate zone bats. This, therefore, poses the question as to what mechanisms allow for lyssavirus infection persistence in bat populations in tropical regions that do not hibernate. Results/Conclusions . Data collected from a 5 year study of a migratory African fruit bat species, Eidolon helvum, and its associated lyssavirus, LBV, will be presented. These data on host demographic and infection related parameters for the E. helvum-LBV system suggest the species is a long-lived K-selected species (annual survival probability 0.83, 95% CI 0.73-0.93), with a seasonal birth pulse. Infection with LBV is endemic with a high proportion of individuals become immune following infection, and probability of being seropositive increases with age. Using these data in a stochastic mechanistic model that incorporates seasonal births and transmission, different mechanisms of persistence for LBV within an E. helvum colony are tested and compared to those in the temperate E. fuscus-RABV system to determine which aspects of host ecology allow persistence in this system.

Ecology Letters, 2015

Bats are natural reservoirs of several important emerging viruses. Cross-species transmission app... more Bats are natural reservoirs of several important emerging viruses. Cross-species transmission appears to be quite common among bats, which may contribute to their unique reservoir potential. Therefore, understanding the importance of bats as reservoirs requires examining them in a community context rather than concentrating on individual species. Here, we use a network approach to identify ecological and biological correlates of cross-species virus transmission in bats and rodents, another important host group. We show that given our current knowledge the bat viral sharing network is more connected than the rodent network, suggesting viruses may pass more easily between bat species. We identify host traits associated with important reservoir species: gregarious bats are more likely to share more viruses and bats which migrate regionally are important for spreading viruses through the network. We identify multiple communities of viral sharing within bats and rodents and highlight potential species traits that can help guide studies of novel pathogen emergence.

Background/Question/Methods A central question in disease ecology is how pathogen diversity is ge... more Background/Question/Methods A central question in disease ecology is how pathogen diversity is generated and maintained in host populations and its influence on disease dynamics. We use Bartonella in African fruit bats to explore how host population structure supports high pathogen diversity and infection prevalence. Bartonella are facultative intracellular bacteria that infect a variety of mammals worldwide, showing particularly high prevalence and diversity in bats. Bartonella species are transmitted by hematophagous arthropods and it is hypothesized that ectoparasitic bat flies are vectors of the bacteria in bats. However, little is known about how bat and bat fly ecology contribute to Bartonella transmission dynamics. Recent studies show that the fruit bat Eidolon helvum is panmictic across its African range. We hypothesize that this level of connectivity allows for high transmission of Bartonella among distant populations, resulting in minimal population structure and high dive...

The ecology of infectious disease in wildlife has become a pivotal theme in animal and public hea... more The ecology of infectious disease in wildlife has become a pivotal theme in animal and public health. Studies of infectious disease ecology rely on robust surveillance of pathogens in reservoir hosts, often based on serology, which is the detection of specific antibodies in the blood and is used to infer infection history. However, serological data can be inaccurate for inference to infection history for a variety of reasons. Two major aspects in any serological test can substantially impact results and interpretation of antibody prevalence data: cross-reactivity and cut-off thresholds used to discriminate positive and negative reactions. Given the ubiquitous use of serology as a tool for surveillance and epidemiological modeling of wildlife diseases, it is imperative to consider the strengths and limitations of serological test methodologies and interpretation of results, particularly when using data that may affect management and policy for the prevention and control of infectious diseases in wildlife. Greater consideration of population age structure and cohort representation, serological test suitability and standardized sample collection protocols can ensure that reliable data are obtained for downstream modeling applications to characterize, and evaluate interventions for, wildlife disease systems.

Proceedings of the Royal Society B: Biological Sciences, 2014

Proceedings. Biological sciences / The Royal Society, Jan 22, 2015

Filoviruses Ebolavirus (EBOV) and Marburgvirus (MARV) cause haemorrhagic fevers with high mortali... more Filoviruses Ebolavirus (EBOV) and Marburgvirus (MARV) cause haemorrhagic fevers with high mortality rates, posing significant threats to public health. To understand transmission into human populations, filovirus dynamics within reservoir host populations must be understood. Studies have directly linked filoviruses to bats, but the mechanisms allowing viral persistence within bat populations are poorly understood. Theory suggests seasonal birthing may decrease the probability of pathogen persistence within populations, but data suggest MARV may persist within colonies of seasonally breeding Egyptian fruit bats, Rousettus aegyptiacus. I synthesize available filovirus and bat data in a stochastic compartmental model to explore fundamental questions relating to filovirus ecology: can filoviruses persist within isolated bat colonies; do critical community sizes exist; and how do host-pathogen relationships affect spillover transmission potential? Synchronous annual breeding and shorter ...

Viruses, 2014

Filoviruses, including Ebolavirus and Marburgvirus, pose significant threats to public health and... more Filoviruses, including Ebolavirus and Marburgvirus, pose significant threats to public health and species conservation by causing hemorrhagic fever outbreaks with high mortality rates. Since the first outbreak in 1967, their origins, natural history, and ecology remained elusive until recent studies linked them through molecular, serological, and virological studies to bats. We review the ecology, epidemiology, and natural history of these systems, drawing on examples from other bat-borne zoonoses, and highlight key areas for future research. We compare and contrast results from ecological and virological studies of bats and filoviruses with those of other systems. We also highlight how advanced methods, such as more recent serological assays, can be interlinked with flexible statistical methods and experimental studies to inform the field studies necessary to understand filovirus persistence in wildlife populations and cross-species transmission leading to outbreaks. We highlight the need for a more unified, global surveillance strategy for filoviruses in wildlife, and advocate for more integrated, multi-disciplinary approaches to understand dynamics in bat populations to ultimately mitigate or prevent potentially devastating disease outbreaks.

Current Topics in Microbiology and Immunology, 2012

Henipaviruses cause fatal infection in humans and domestic animals. Transmission from fruit bats,... more Henipaviruses cause fatal infection in humans and domestic animals. Transmission from fruit bats, the wildlife reservoirs of henipaviruses, is putatively driven (at least in part) by anthropogenic changes that alter host ecology. Human and domestic animal fatalities occur regularly in Asia and Australia, but recent findings suggest henipaviruses are present in bats across the Old World tropics. We review the application of the One Health approach to henipavirus research in three

PLoS neglected tropical diseases, 2015

Bartonellae are facultative intracellular bacteria and are highly adapted to their mammalian host... more Bartonellae are facultative intracellular bacteria and are highly adapted to their mammalian host cell niches. Straw-colored fruit bats (Eidolon helvum) are commonly infected with several bartonella strains. To elucidate the genetic diversity of these bartonella strains, we analyzed 79 bartonella isolates from straw-colored fruit bats in seven countries across Africa (Cameroon, Annobon island of Equatorial Guinea, Ghana, Kenya, Nigeria, Tanzania, and Uganda) using a multi-locus sequencing typing (MLST) approach based on nucleotide sequences of eight loci (ftsZ, gltA, nuoG, ribC, rpoB, ssrA, ITS, and 16S rRNA). The analysis of each locus but ribC demonstrated clustering of the isolates into six genogroups (E1 - E5 and Ew), while ribC was absent in the isolates belonging to the genogroup Ew. In general, grouping of all isolates by each locus was mutually supportive; however, nuoG, gltA, and rpoB showed some incongruity with other loci in several strains, suggesting a possibility of re...

Parasites & Vectors, 2015

Background: Vector control remains the primary defense against dengue fever. Its success relies o... more Background: Vector control remains the primary defense against dengue fever. Its success relies on the assumption that vector density is related to disease transmission. Two operational issues include the amount by which mosquito density should be reduced to minimize transmission and the spatio-temporal allotment of resources needed to reduce mosquito density in a cost-effective manner. Recently, a novel technology, MI-Dengue, was implemented city-wide in several Brazilian cities to provide real-time mosquito surveillance data for spatial prioritization of vector control resources. We sought to understand the role of city-wide mosquito density data in predicting disease incidence in order to provide guidance for prioritization of vector control work.