Avian Malaria

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Carter T Atkinson - One of the best experts on this subject based on the ideXlab platform.

  • facilitated adaptation for conservation can gene editing save hawaii s endangered birds from climate driven Avian Malaria
    2020
    Co-Authors: Michael D Samuel, Carter T Atkinson, Wei Liao, Dennis A Lapointe
    Abstract:

    Abstract Avian Malaria has played a significant role in causing extinctions, population declines, and limiting the elevational distribution of Hawaiian honeycreepers. Most threatened and endangered honeycreepers only exist in high-elevation forests where the risk of Malaria infection is limited. Because Culex mosquito vectors and Avian Malaria dynamics are strongly influenced by temperature and rainfall, future climate change is predicted to expand Malaria infection to high-elevation forests and intensify Malaria infection at lower elevations, likely resulting in future extinctions and loss of Avian biodiversity in Hawaii. Novel, landscape-level mosquito control strategies are promising, but are logistically challenging and require costly long-term efforts. As an alternative or supplemental strategy, we evaluated the potential of releasing a gene-edited Malaria-resistant honeycreeper (Iiwi, Drepanis coccinea) in Hawaiian rainforests; a strategy known as facilitated adaptation. While this approach also has significant technical challenges and costs, it may offer a more permanent solution to increasing Malaria threats. If Malaria-resistant honeycreepers can be developed, facilitated adaptation may provide a practical strategy for the reestablishment of abundant Avian populations in Hawaiian forests. A successful strategy could be the release of Malaria-resistant Iiwi in mid-elevation forests where development of a resistant population has the best chance of success. Establishment of a resistant Iiwi population could provide a source for dispersal and development of resistant populations in high-elevation forests and a permanent source of resistant individuals for translocation to other vulnerable areas.

  • mitigating future Avian Malaria threats to hawaiian forest birds from climate change
    2017
    Co-Authors: Wei Liao, Dennis A Lapointe, Carter T Atkinson, Michael D Samuel
    Abstract:

    Avian Malaria, transmitted by Culex quinquefasciatus mosquitoes in the Hawaiian Islands, has been a primary contributor to population range limitations, declines, and extinctions for many endemic Hawaiian honeycreepers. Avian Malaria is strongly influenced by climate; therefore, predicted future changes are expected to expand transmission into higher elevations and intensify and lengthen existing transmission periods at lower elevations, leading to further population declines and potential extinction of highly susceptible honeycreepers in mid- and high-elevation forests. Based on future climate changes and resulting Malaria risk, we evaluated the viability of alternative conservation strategies to preserve endemic Hawaiian birds at mid and high elevations through the 21st century. We linked an epidemiological model with three alternative climatic projections from the Coupled Model Intercomparison Project to predict future Malaria risk and bird population dynamics for the coming century. Based on climate change predictions, proposed strategies included mosquito population suppression using modified males, release of genetically modified refractory mosquitoes, competition from other introduced mosquitoes that are not competent vectors, evolved Malaria-tolerance in native honeycreepers, feral pig control to reduce mosquito larval habitats, and predator control to improve bird demographics. Transmission rates of Malaria are predicted to be higher than currently observed and are likely to have larger impacts in high-elevation forests where current low rates of transmission create a refuge for highly-susceptible birds. As a result, several current and proposed conservation strategies will be insufficient to maintain existing forest bird populations. We concluded that mitigating Malaria transmission at high elevations should be a primary conservation goal. Conservation strategies that maintain highly susceptible species like Iiwi (Drepanis coccinea) will likely benefit other threatened and endangered Hawai’i species, especially in high-elevation forests. Our results showed that mosquito control strategies offer potential long-term benefits to high elevation Hawaiian honeycreepers. However, combined strategies will likely be needed to preserve endemic birds at mid elevations. Given the delay required to research, develop, evaluate, and improve several of these currently untested conservation strategies we suggest that planning should begin expeditiously.

  • global phylogeography of the Avian Malaria pathogen plasmodium relictum based on msp1 allelic diversity
    2015
    Co-Authors: Olof Hellgren, Dimitar Dimitrov, Carter T Atkinson, Staffan Bensch, Marcos Robalinho Lima, Tamer Albayrak, John G Ewen, Kyeong Soon Kim, Lynn B Martin, Vaidas Palinauskas
    Abstract:

    Knowing the genetic variation that occurs in pathogen populations and how it is distributed across geographical areas is essential to understand parasite epidemiology, local patterns of virulence, and evolution of host-resistance. In addition, it is important to identify populations of pathogens that are evolutionarily independent and thus free' to adapt to hosts and environments. Here, we investigated genetic variation in the globally distributed, highly invasive Avian Malaria parasite Plasmodium relictum, which has several distinctive mitochondrial haplotyps (cyt b lineages, SGS1, GRW11 and GRW4). The phylogeography of P. relictum was accessed using the highly variable nuclear gene merozoite surface protein 1 (MSP1), a gene linked to the invasion biology of the parasite. We show that the lineage GRW4 is evolutionarily independent of GRW11 and SGS1 whereas GRW11 and SGS1 share MSP1 alleles and thus suggesting the presence of two distinct species (GRW4 versus SGS1 and GRW11). Further, there were significant differences in the global distribution of MSP1 alleles with differences between GRW4 alleles in the New and the Old World. For SGS1, a lineage formerly believed to have both tropical and temperate transmission, there were clear differences in MSP1 alleles transmitted in tropical Africa compared to the temperate regions of Europe and Asia. Further, we highlight the occurrence of multiple MSP1 alleles in GRW4 isolates from the Hawaiian Islands, where the parasite has contributed to declines and extinctions of endemic forest birds since it was introduced. This study stresses the importance of multiple independent loci for understanding patterns of transmission and evolutionary independence across Avian Malaria parasites. (Less)

  • Avian Malaria in hawaiian forest birds infection and population impacts across species and elevations
    2015
    Co-Authors: Michael D Samuel, Carter T Atkinson, Bethany L Woodworth, Patrick J Hart, Dennis A Lapointe
    Abstract:

    Wildlife diseases can present significant threats to ecological systems and biological diversity, as well as domestic animal and human health. However, determining the dynamics of wildlife diseases and understanding the impact on host populations is a significant challenge. In Hawai‘i, there is ample circumstantial evidence that introduced Avian Malaria (Plasmodium relictum) has played an important role in the decline and extinction of many native forest birds. However, few studies have attempted to estimate disease transmission and mortality, survival, and individual species impacts in this distinctive ecosystem. We combined multi-state capture-recapture (longitudinal) models with cumulative age-prevalence (cross-sectional) models to evaluate these patterns in Apapane, Hawai‘i Amakihi, and Iiwi in low-, mid-, and high-elevation forests on the island of Hawai‘i based on four longitudinal studies of 3–7 years in length. We found species-specific patterns of Malaria prevalence, transmission, and mortality r...

  • Experimental Evidence for Evolved Tolerance to Avian Malaria in a Wild Population of Low Elevation Hawai‘i ‘Amakihi (Hemignathus virens)
    2013
    Co-Authors: Carter T Atkinson, Katerine S. Saili, Ruth B. Utzurrum, Susan I. Jarvi
    Abstract:

    Introduced vector-borne diseases, particularly Avian Malaria ( Plasmodium relictum ) and Avian pox virus ( Avipoxvirus spp.), continue to play significant roles in the decline and extinction of native forest birds in the Hawaiian Islands. Hawaiian honeycreepers are particularly susceptible to Avian Malaria and have survived into this century largely because of persistence of high elevation refugia on Kaua‘i, Maui, and Hawai‘i Islands, where transmission is limited by cool temperatures. The long term stability of these refugia is increasingly threatened by warming trends associated with global climate change. Since cost effective and practical methods of vector control in many of these remote, rugged areas are lacking, adaptation through processes of natural selection may be the best long-term hope for recovery of many of these species. We document emergence of tolerance rather than resistance to Avian Malaria in a recent, rapidly expanding low elevation population of Hawai‘i ‘Amakihi ( Hemignathus virens ) on the island of Hawai‘i. Experimentally infected low elevation birds had lower mortality, lower reticulocyte counts during recovery from acute infection, lower weight loss, and no declines in food consumption relative to experimentally infected high elevation Hawai‘i ‘Amakihi in spite of similar intensities of infection. Emergence of this population provides an exceptional opportunity for determining physiological mechanisms and genetic markers associated with Malaria tolerance that can be used to evaluate whether other, more threatened species have the capacity to adapt to this disease.

Dennis A Lapointe - One of the best experts on this subject based on the ideXlab platform.

  • facilitated adaptation for conservation can gene editing save hawaii s endangered birds from climate driven Avian Malaria
    2020
    Co-Authors: Michael D Samuel, Carter T Atkinson, Wei Liao, Dennis A Lapointe
    Abstract:

    Abstract Avian Malaria has played a significant role in causing extinctions, population declines, and limiting the elevational distribution of Hawaiian honeycreepers. Most threatened and endangered honeycreepers only exist in high-elevation forests where the risk of Malaria infection is limited. Because Culex mosquito vectors and Avian Malaria dynamics are strongly influenced by temperature and rainfall, future climate change is predicted to expand Malaria infection to high-elevation forests and intensify Malaria infection at lower elevations, likely resulting in future extinctions and loss of Avian biodiversity in Hawaii. Novel, landscape-level mosquito control strategies are promising, but are logistically challenging and require costly long-term efforts. As an alternative or supplemental strategy, we evaluated the potential of releasing a gene-edited Malaria-resistant honeycreeper (Iiwi, Drepanis coccinea) in Hawaiian rainforests; a strategy known as facilitated adaptation. While this approach also has significant technical challenges and costs, it may offer a more permanent solution to increasing Malaria threats. If Malaria-resistant honeycreepers can be developed, facilitated adaptation may provide a practical strategy for the reestablishment of abundant Avian populations in Hawaiian forests. A successful strategy could be the release of Malaria-resistant Iiwi in mid-elevation forests where development of a resistant population has the best chance of success. Establishment of a resistant Iiwi population could provide a source for dispersal and development of resistant populations in high-elevation forests and a permanent source of resistant individuals for translocation to other vulnerable areas.

  • mitigating future Avian Malaria threats to hawaiian forest birds from climate change
    2017
    Co-Authors: Wei Liao, Dennis A Lapointe, Carter T Atkinson, Michael D Samuel
    Abstract:

    Avian Malaria, transmitted by Culex quinquefasciatus mosquitoes in the Hawaiian Islands, has been a primary contributor to population range limitations, declines, and extinctions for many endemic Hawaiian honeycreepers. Avian Malaria is strongly influenced by climate; therefore, predicted future changes are expected to expand transmission into higher elevations and intensify and lengthen existing transmission periods at lower elevations, leading to further population declines and potential extinction of highly susceptible honeycreepers in mid- and high-elevation forests. Based on future climate changes and resulting Malaria risk, we evaluated the viability of alternative conservation strategies to preserve endemic Hawaiian birds at mid and high elevations through the 21st century. We linked an epidemiological model with three alternative climatic projections from the Coupled Model Intercomparison Project to predict future Malaria risk and bird population dynamics for the coming century. Based on climate change predictions, proposed strategies included mosquito population suppression using modified males, release of genetically modified refractory mosquitoes, competition from other introduced mosquitoes that are not competent vectors, evolved Malaria-tolerance in native honeycreepers, feral pig control to reduce mosquito larval habitats, and predator control to improve bird demographics. Transmission rates of Malaria are predicted to be higher than currently observed and are likely to have larger impacts in high-elevation forests where current low rates of transmission create a refuge for highly-susceptible birds. As a result, several current and proposed conservation strategies will be insufficient to maintain existing forest bird populations. We concluded that mitigating Malaria transmission at high elevations should be a primary conservation goal. Conservation strategies that maintain highly susceptible species like Iiwi (Drepanis coccinea) will likely benefit other threatened and endangered Hawai’i species, especially in high-elevation forests. Our results showed that mosquito control strategies offer potential long-term benefits to high elevation Hawaiian honeycreepers. However, combined strategies will likely be needed to preserve endemic birds at mid elevations. Given the delay required to research, develop, evaluate, and improve several of these currently untested conservation strategies we suggest that planning should begin expeditiously.

  • Avian Malaria in hawaiian forest birds infection and population impacts across species and elevations
    2015
    Co-Authors: Michael D Samuel, Carter T Atkinson, Bethany L Woodworth, Patrick J Hart, Dennis A Lapointe
    Abstract:

    Wildlife diseases can present significant threats to ecological systems and biological diversity, as well as domestic animal and human health. However, determining the dynamics of wildlife diseases and understanding the impact on host populations is a significant challenge. In Hawai‘i, there is ample circumstantial evidence that introduced Avian Malaria (Plasmodium relictum) has played an important role in the decline and extinction of many native forest birds. However, few studies have attempted to estimate disease transmission and mortality, survival, and individual species impacts in this distinctive ecosystem. We combined multi-state capture-recapture (longitudinal) models with cumulative age-prevalence (cross-sectional) models to evaluate these patterns in Apapane, Hawai‘i Amakihi, and Iiwi in low-, mid-, and high-elevation forests on the island of Hawai‘i based on four longitudinal studies of 3–7 years in length. We found species-specific patterns of Malaria prevalence, transmission, and mortality r...

  • ecology and conservation biology of Avian Malaria
    2012
    Co-Authors: Dennis A Lapointe, Carter T Atkinson, Michael D Samuel
    Abstract:

    Avian Malaria is a worldwide mosquito-borne disease caused by Plasmodium parasites. These parasites occur in many Avian species but primarily affect passerine birds that have not evolved with the parasite. Host pathogenicity, fitness, and population impacts are poorly understood. In contrast to continental species, introduced Avian Malaria poses a substantial threat to naive birds on Hawaii, the Galapagos, and other archipelagoes. In Hawaii, transmission is maintained by susceptible native birds, competence and abundance of mosquitoes, and a disease reservoir of chronically infected native birds. Although vector habitat and Avian communities determine the geographic distribution of disease, climate drives transmission patterns ranging from continuous high infection in warm lowland forests, seasonal infection in midelevation forests, and disease-free refugia in cool high-elevation forests. Global warming is expected to increase the occurrence, distribution, and intensity of Avian Malaria across this elevational gradient and threaten high-elevation refugia, which is the key to survival of many susceptible Hawaiian birds. Increased temperatures may have already increased global Avian Malaria prevalence and contributed to an emergence of disease in New Zealand.

  • thermal constraints to the sporogonic development and altitudinal distribution of Avian Malaria plasmodium relictum in hawai i
    2010
    Co-Authors: Dennis A Lapointe, Lee M Goff, Carter T Atkinson
    Abstract:

    Abstract More than half of the Hawaiian honeycreepers (Drepanidinae) known from historical records are now extinct. Introduced mosquito-borne disease, in particular the Avian Malaria Plasmodium relictum, has been incriminated as a leading cause of extinction during the 20th century and a major limiting factor in the recovery of remaining species populations. Today, most native Hawaiian bird species reach their highest densities and diversity in high elevation (>1,800 m above sea level) forests. We determined the thermal requirements for sporogonic development of P. relictum in the natural vector, Culex quinquefasciatus, and assessed the current distribution of native bird species in light of this information. Sporogonic development was completed at constant laboratory and mean field temperatures between 30 and 17 C, but development, prevalence, and intensity decreased significantly below 21 C. Using a degree-day (DD) model, we estimated a minimum threshold temperature of 12.97 C and a thermal requirement ...

Ravinder Nm Sehgal - One of the best experts on this subject based on the ideXlab platform.

  • Avian Malaria co-infections confound infectivity and vector competence assays of Plasmodium homopolare
    2018
    Co-Authors: Jenny S. Carlson, Ravinder Nm Sehgal, Brittany Nelms, Christopher M. Barker, William K. Reisen, Anthony J. Cornel
    Abstract:

    Currently, there are very few studies of Avian Malaria that investigate relationships among the host-vector-parasite triad concomitantly. In the current study, we experimentally measured the vector competence of several Culex mosquitoes for a newly described Avian Malaria parasite, Plasmodium homopolare . Song sparrow ( Melospiza melodia ) blood infected with a low P . homopolare parasitemia was inoculated into a naïve domestic canary ( Serinus canaria forma domestica ). Within 5 to 10 days post infection (dpi), the canary unexpectedly developed a simultaneous high parasitemic infection of Plasmodium cathemerium (Pcat6) and a low parasitemic infection of P . homopolare , both of which were detected in blood smears. During this infection period, PCR detected Pcat6, but not P . homopolare in the canary. Between 10 and 60 dpi, Pcat6 blood stages were no longer visible and PCR no longer amplified Pcat6 parasite DNA from canary blood. However, P . homopolare blood stages remained visible, albeit still at very low parasitemias, and PCR was able to amplify P . homopolare DNA. This pattern of mixed Pcat6 and P . homopolare infection was repeated in three secondary infected canaries that were injected with blood from the first infected canary. Mosquitoes that blood-fed on the secondary infected canaries developed infections with Pcat6 as well as another P . cathemerium lineage (Pcat8); none developed PCR detectable P . homopolare infections. These observations suggest that the original P . homopolare -infected songbird also had two un-detectable P . cathemerium lineages/strains. The vector and host infectivity trials in this study demonstrated that current molecular assays may significantly underreport the extent of mixed Avian Malaria infections in vectors and hosts.

  • identifying Avian Malaria vectors sampling methods influence outcomes
    2015
    Co-Authors: Jenny S. Carlson, Ravinder Nm Sehgal, Christopher M. Barker, Erika L Walther, Rebecca Troutfryxell, Sarah Staley, Lisa A Tell, Anthony J. Cornel
    Abstract:

    The role of vectors in the transmission of Avian Malaria parasites is currently understudied. Many studies that investigate parasite-vector relationships use limited trapping techniques and/or identify potential competent vectors in the field in such ways that cannot distinguish between an infected or infectious vector. Without the use of multiple trapping techniques that address the specific biology of diverse mosquito species, and without looking at the infection status of individual mosquitoes, it is not possible to make dependable conclusions on the role of mosquitoes in the transmission of Avian Malaria parasites. We conducted two years of mosquito collections at a riparian preserve in California where a wide diversity of species were collected with multiple trap types. We hypothesized that competent mosquito species can influence the distribution and diversity of Avian Malaria parasites by acting as a compatibility filter for specific Plasmodium species. To determine the infection status of all individual mosquitoes for Plasmodium species/lineages, amplification within the cytochrome b gene was carried out on over 3000 individual mosquito thoraxes, and for those that tested positive we then repeated the same process for abdomens and salivary glands. Our data show heterogeneity in the transmissibility of Plasmodium among ornithophillic mosquito species. More specifically, Culex stigmatosoma appears to not be a vector of Plasmodium homopolare, a parasite that is prevalent in the Avian population, but is a vector of multiple other Plasmodium species/lineages. Our results suggest that conclusions made on the role of vectors from studies that do not use different mosquito trapping methods should be re-evaluated with caution, as we documented the potential for trapping biases, which may cause studies to miss important roles of specific mosquito species in the transmission of Avian Malaria. Moreover, we document heterogeneity in the transmission of Plasmodium spp. by mosquitoes can influence Plasmodium diversity and prevalence in specific locations to Plasmodium-vector incompatibilities.

  • coevolutionary patterns and diversification of Avian Malaria parasites in african sunbirds family nectariniidae
    2015
    Co-Authors: Elvin J Lauron, Claire Loiseau, Thomas B. Smith, Martim Melo, Rauri C K Bowie, Greg S Spicer, Ravinder Nm Sehgal
    Abstract:

    The coevolutionary relationships between Avian Malaria parasites and their hosts influence the host specificity, geographical distribution and pathogenicity of these parasites. However, to understand fine scale coevolutionary host-parasite relationships, robust and widespread sampling from closely related hosts is needed. We thus sought to explore the coevolutionary history of Avian Plasmodium and the widespread African sunbirds, family Nectariniidae. These birds are distributed throughout Africa and occupy a variety of habitats. Considering the role that habitat plays in influencing host-specificity and the role that host-specificity plays in coevolutionary relationships, African sunbirds provide an exceptional model system to study the processes that govern the distribution and diversity of Avian Malaria. Here we evaluated the coevolutionary histories using a multi-gene phylogeny for Nectariniidae and Avian Plasmodium found in Nectariniidae. We then assessed the host-parasite biogeography and the structuring of parasite assemblages. We recovered Plasmodium lineages concurrently in East, West, South and Island regions of Africa. However, several Plasmodium lineages were recovered exclusively within one respective region, despite being found in widely distributed hosts. In addition, we inferred the biogeographic history of these parasites and provide evidence supporting a model of biotic diversification in Avian Plasmodium of African sunbirds.

  • Invasive Avian Malaria as an emerging parasitic disease in native birds of Peru
    2015
    Co-Authors: Alfonso Marzal, Jorge M. Cárdenas Callirgos, Luz García-longoria, Ravinder Nm Sehgal
    Abstract:

    Some species of Avian Malaria parasites are invaders and responsible for diversity losses worldwide. Here we analyze the prevalence and genetic characterization of Avian Malaria and related haemosporidian parasites in Neotropical birds from two different regions of Peru. We detected an overall prevalence of 32.4 % comprising 12 infected bird species. The pathogen Plasmodium relictum SGS1 was widespread and the most prevalent parasite found in our study (39 % of the total infections), infecting 8 host species in both localities. To the best of our knowledge, this is the first report of this invasive pathogen in the mainland Americas, thus representing a possible menace to over one-third of all bird species in the world.

  • balancing biodiversity with agriculture land sharing mitigates Avian Malaria prevalence
    2013
    Co-Authors: Chase D Mendenhall, Holly M Archer, Federico Oviedo Brenes, Cagan H Sekercioglu, Ravinder Nm Sehgal
    Abstract:

    Debate over balancing agricultural production and biodiversity conservation has generated two opposing strategies: a “land sparing” approach involving large-scale nature reserves, versus a “land sharing” approach where agricultural areas support wildlife through fine-scale conservation. As a result of this debate, studies focus almost exclusively on species diversity and food production, while ignoring other critical ecosystem processes such as disease dynamics. Here we quantify how tropical Avian Malaria in an abundant sedentary bird species responds at fine spatial scales in a “land sharing” system. We find the proportion and configuration of countryside forest elements within a radius of 400 m, proximity to the nearest river, and habitat type explains Malaria prevalence across the region. We simulate “land sparing” and “land sharing” land use strategies and model Malaria prevalence to find that land sharing mitigates Malaria prevalence more effectively. With these analyses, we gain a better understanding of how biodiversity, ecosystem services, agricultural yield, and human well-being intersect in complex ecosystems.

Ana Rivero - One of the best experts on this subject based on the ideXlab platform.

  • Gene regulation of the Avian Malaria parasite Plasmodium relictum, during the different stages within the mosquito vector
    2020
    Co-Authors: V. Sekar, Ana Rivero, R. Pigeault, S. Gandon, A. Drews, Dag Ahren, O. Hellgren
    Abstract:

    The Malaria parasite Plasmodium relictum is one of the most widespread species of Avian Malaria. As is the case in its human counterparts, bird Plasmodium undergoes a complex life cycle infecting two hosts: the arthropod vector and the vertebrate host. In this study, we examine the transcriptome of P. relictum (SGS1) during crucial timepoints within its natural vector, Culex pipiens quinquefasciatus . Differential gene-expression analyses identified genes linked to the parasites life-stages at: i) a few minutes after the blood meal is ingested, ii) during peak oocyst production phase, iii) during peak sporozoite phase and iv) during the late-stages of the infection. A large amount of genes coding for functions linked to host-immune invasion and multifunctional genes was active throughout the infection cycle. One gene associated with a conserved Plasmodium membrane protein with unknown function was upregulated throughout the parasite development in the vector, suggesting an important role in the successful completion of the sporogonic cycle. Transcript annotation further revealed novel genes, which were significantly differentially expressed during the infection in the vector as well as upregulation of reticulocyte-binding proteins, which raises the possibility of the multifunctionality of these RBPs. We establish the existence of highly stage-specific pathways being overexpressed during the infection. This first study of gene-expression of a non-human Plasmodium species in its natural vector provides a comprehensive insight into the molecular mechanisms of the common Avian Malaria parasite P. relictum and provides essential information on the evolutionary diversity in gene regulation of the Plasmodium’s vector stages.

  • evolutionary ecology of Avian Malaria past to present
    2018
    Co-Authors: Ana Rivero, Sylvain Gandon
    Abstract:

    Avian Malaria is the oldest experimental system for investigating the biology and transmission of Plasmodium parasites. Recent molecular protocols for detecting and characterizing Avian Malaria lineages in the field are providing an ever-growing picture of the prevalence, distribution, host range, and diversity hotspots of Avian Malaria across the world. The unparalleled genetic diversity uncovered rivals anything that has been found in other vertebrate Malarias and seems to be matched by an equally rich phenotypic diversity, providing endless opportunities for exploring the selective pressures under which hosts and parasites evolve. We review the most important milestones in Avian Plasmodium research and explain why this is a unique animal model to understand the ecology and evolution of Malaria.

  • mosquito age and Avian Malaria infection
    2015
    Co-Authors: Romain Pigeault, Antoine Nicot, Sylvain Gandon, Ana Rivero
    Abstract:

    The immune system of many insects wanes dramatically with age, leading to the general prediction that older insects should be more susceptible to infection than their younger counterparts. This prediction is however challenged by numerous studies showing that older insects are more resistant to a range of pathogens. The effect of age on susceptibility to infections is particularly relevant for mosquitoes given their role as vectors of Malaria and other diseases. Despite this, the effect of mosquito age on Plasmodium susceptibility has been rarely explored, either experimentally or theoretically. Experiments were carried out using the Avian Malaria parasite Plasmodium relictum and its natural vector in the field, the mosquito Culex pipiens. Both innate immune responses (number and type of circulating haemocytes) and Plasmodium susceptibility (prevalence and burden) were quantified in seven- and 17-day old females. Whether immunity or Plasmodium susceptibility are modulated by the previous blood feeding history of the mosquito was also investigated. To ensure repeatability, two different experimental blocks were carried out several weeks apart. Haemocyte numbers decrease drastically as the mosquitoes age. Despite this, older mosquitoes are significantly more resistant to a Plasmodium infection than their younger counterparts. Crucially, however, the age effect is entirely reversed when old mosquitoes have taken one previous non-infected blood meal. The results agree with previous studies showing that older insects are often more resistant to infections than younger ones. These results suggest that structural and functional alterations in mosquito physiology with age may be more important than immunity in determining the probability of a Plasmodium infection in old mosquitoes. Possible explanations for why the effect is reversed in blood-fed mosquitoes are discussed. The reversal of the age effect in blood fed mosquitoes implies that age is unlikely to have a significant impact on mosquito susceptibility in the field.

  • Avian Malaria a new lease of life for an old experimental model to study the evolutionary ecology of plasmodium
    2015
    Co-Authors: Romain Pigeault, Sylvain Gandon, Antoine Nicot, Julien Vezilier, Stephane Cornet, Flore Zele, Philippe Perret, Ana Rivero
    Abstract:

    Avian Malaria has historically played an important role as a model in the study of human Malaria, being a stimulus for the development of medical parasitology. Avian Malaria has recently come back to the research scene as a unique animal model to understand the ecology and evolution of the disease, both in the field and in the laboratory. Avian Malaria is highly prevalent in birds and mosquitoes around the world and is amenable to laboratory experimentation at each stage of the parasite's life cycle. Here, we take stock of 5 years of experimental laboratory research carried out using Plasmodium relictum SGS1, the most prevalent Avian Malaria lineage in Europe, and its natural vector, the mosquito Culex pipiens. For this purpose, we compile and analyse data obtained in our laboratory in 14 different experiments. We provide statistical relationships between different infection-related parameters, including parasitaemia, gametocytaemia, host morbidity (anaemia) and transmission rates to mosquitoes. This analysis provides a wide-ranging picture of the within-host and between-host parameters that may bear on Malaria transmission and epidemiology.

  • dynamics of prevalence and diversity of Avian Malaria infections in wild culex pipiens mosquitoes the effects of wolbachia filarial nematodes and insecticide resistance
    2014
    Co-Authors: Flore Zele, Ana Rivero, Sylvain Gandon, Antoine Nicot, Juilen Vezilier, Gregory Lambert, Olivier Duron
    Abstract:

    Background: Identifying the parasites transmitted by a particular vector and the factors that render this vector susceptible to the parasite are key steps to understanding disease transmission. Although Avian Malaria has become a model system for the investigation of the ecological and evolutionary dynamics of Plasmodium parasites, little is still known about the field prevalence, diversity and distribution of Avian Plasmodium species within the vectors, or about the extrinsic factors affecting Plasmodium population dynamics in the wild. Methods: We examined changes in Avian Malaria prevalence and Plasmodium lineage composition in female Culex pipiens caught throughout one field season in 2006, across four sampling sites in southern France. Using site occupancy models, we correct the naive estimates of Plasmodium prevalence to account for PCR-based imperfect detection. To establish the importance of different factors that may bear on the prevalence and diversity of Avian Plasmodium in field mosquitoes, we focus on Wolbachia and filarial parasite co-infections, as well as on the insecticide resistance status of the mosquito. Results: Plasmodium prevalence in Cx. pipiens increased from February (0%) to October (15.8%) and did not vary significantly among the four sampling sites. The application of site occupancy models leads to a 4% increase in this initial (naive) estimate of prevalence. The parasite community was composed of 15 different haemosporidian lineages, 13 of which belonged to the Plasmodium genus, and 2 to the Haemoproteus genus. Neither the presence of different Wolbachia types and of filarial parasites co-infecting the mosquitoes, nor their insecticide resistance status were found to affect the Plasmodium prevalence and diversity. Conclusion: We found that haemosporidian parasites are common and diverse in wild-caught Cx. pipiens mosquitoes in Southern France. The prevalence of the infection in mosquitoes is unaffected by Wolbachia and filarial co-infections as well as the insecticide resistant status of the vector. These factors may thus have a negligible impact on the transmission of Avian Malaria. In contrast, the steady increase in prevalence from February to October indicates that the dynamics of Avian Malaria is driven by seasonality and supports that infected birds are the reservoir of a diverse community of lineages in southern France.

Sylvain Gandon - One of the best experts on this subject based on the ideXlab platform.

  • evolutionary ecology of Avian Malaria past to present
    2018
    Co-Authors: Ana Rivero, Sylvain Gandon
    Abstract:

    Avian Malaria is the oldest experimental system for investigating the biology and transmission of Plasmodium parasites. Recent molecular protocols for detecting and characterizing Avian Malaria lineages in the field are providing an ever-growing picture of the prevalence, distribution, host range, and diversity hotspots of Avian Malaria across the world. The unparalleled genetic diversity uncovered rivals anything that has been found in other vertebrate Malarias and seems to be matched by an equally rich phenotypic diversity, providing endless opportunities for exploring the selective pressures under which hosts and parasites evolve. We review the most important milestones in Avian Plasmodium research and explain why this is a unique animal model to understand the ecology and evolution of Malaria.

  • Complete Avian Malaria parasite genomes reveal features associated with lineage-specific evolution in birds and mammals
    2018
    Co-Authors: Ulrike Bohme, Sylvain Gandon, James Cotton, Sascha Steinbiss, Mandy Sanders, Samuel O Oyola, Antoine Nicot, Thomas Otto, Kailash Patra, Colin Herd
    Abstract:

    Avian Malaria parasites are prevalent around the world and infect a wide diversity of bird species. Here, we report the se-quencing and analysis of high-quality draft genome sequences for two Avian Malaria species, Plasmodium relictum and Plasmodium gallinaceum. We identify 50 genes that are specific to Avian Malaria, located in an otherwise conserved core of the genome that shares gene synteny with all other sequenced Malaria genomes. Phylogenetic analysis suggests that the avi-an Malaria species form an outgroup to the mammalian Plasmodium species, and using amino acid divergence between species, we estimate the Avian-and mammalian-infective lineages diverged in the order of 10 million years ago. Consistent with their phylogenetic position, we identify orthologs of genes that had previously appeared to be restricted to the clades of parasites containing Plasmodium falciparum and Plasmodium vivax, the species with the greatest impact on human health. From these ortho-logs, we explore differential diversifying selection across the genus and show that the Avian lineage is remarkable in the extent to which invasion-related genes are evolving. The subtelomeres of the P. relictum and P. gallinaceum genomes contain several novel gene families, including an expanded surf multigene family. We also identify an expansion of reticulocyte binding protein homologs in P. relictum, and within these proteins, we detect distinct regions that are specific to nonhuman primate , humans, rodent, and Avian hosts. For the first time in the Plasmodium lineage, we find evidence of transposable elements, including several hundred fragments of LTR-retrotransposons in both species and an apparently complete LTR-retrotransposon in the genome of P. gallinaceum.

  • complete Avian Malaria parasite genomes reveal features associated with lineage specific evolution in birds and mammals
    2018
    Co-Authors: Ulrike Bohme, Sylvain Gandon, Thomas D Otto, James Cotton, Sascha Steinbiss, Mandy Sanders, Samuel O Oyola, Antoine Nicot, Kailash P Patra
    Abstract:

    Avian Malaria parasites are prevalent around the world and infect a wide diversity of bird species. Here, we report the sequencing and analysis of high-quality draft genome sequences for two Avian ...

  • complete Avian Malaria parasite genomes reveal host specific parasite evolution in birds and mammals
    2016
    Co-Authors: Ulrike Boehme, Sylvain Gandon, Thomas D Otto, James Cotton, Sascha Steinbiss, Mandy Sanders, Samuel O Oyola, Antoine Nicot, Kailash P Patra, Colin Herd
    Abstract:

    Avian Malaria parasites are prevalent around the world, and infect a wide diversity of bird species. Here we report the sequencing and analysis of high quality draft genome sequences for two Avian Malaria species, Plasmodium relictum and Plasmodium gallinaceum. We identify 50 genes that are specific to Avian Malaria, located in an otherwise conserved core of the genome that shares gene synteny with all other sequenced Malaria genomes. Phylogenetic analysis suggests that the Avian Malaria species form an outgroup to the mammalian Plasmodium species. Consistent with their phylogenetic position, we identify orthologs of genes that had previously appeared to be restricted to the clades of parasites containing P. falciparum and P. vivax - the species with the greatest impact on human health. The subtelomeres of P. relictum and P. gallinaceum contain several novel gene families, including an expanded surf multigene family. We also identify an expansion of reticulocyte binding protein homologs in P. relictum and within these proteins proteins, we detect distinct regions that are specific to non-human primate, humans, rodent and Avian hosts. For the first time in the Plasmodium lineage we find evidence of transposable elements, including several hundred fragments of LTR-retrotransposons in both species and an apparently complete LTR-retrotransposon in the genome of P. gallinaceum.

  • mosquito age and Avian Malaria infection
    2015
    Co-Authors: Romain Pigeault, Antoine Nicot, Sylvain Gandon, Ana Rivero
    Abstract:

    The immune system of many insects wanes dramatically with age, leading to the general prediction that older insects should be more susceptible to infection than their younger counterparts. This prediction is however challenged by numerous studies showing that older insects are more resistant to a range of pathogens. The effect of age on susceptibility to infections is particularly relevant for mosquitoes given their role as vectors of Malaria and other diseases. Despite this, the effect of mosquito age on Plasmodium susceptibility has been rarely explored, either experimentally or theoretically. Experiments were carried out using the Avian Malaria parasite Plasmodium relictum and its natural vector in the field, the mosquito Culex pipiens. Both innate immune responses (number and type of circulating haemocytes) and Plasmodium susceptibility (prevalence and burden) were quantified in seven- and 17-day old females. Whether immunity or Plasmodium susceptibility are modulated by the previous blood feeding history of the mosquito was also investigated. To ensure repeatability, two different experimental blocks were carried out several weeks apart. Haemocyte numbers decrease drastically as the mosquitoes age. Despite this, older mosquitoes are significantly more resistant to a Plasmodium infection than their younger counterparts. Crucially, however, the age effect is entirely reversed when old mosquitoes have taken one previous non-infected blood meal. The results agree with previous studies showing that older insects are often more resistant to infections than younger ones. These results suggest that structural and functional alterations in mosquito physiology with age may be more important than immunity in determining the probability of a Plasmodium infection in old mosquitoes. Possible explanations for why the effect is reversed in blood-fed mosquitoes are discussed. The reversal of the age effect in blood fed mosquitoes implies that age is unlikely to have a significant impact on mosquito susceptibility in the field.

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