Biology subjects

Berthomieu, A.

Publications and source records attributed to Berthomieu, A..

8 recordsLinked to original sources

bioRxiv2026

The genome of the avian malaria parasite Haemoproteus majoris (lineage WW2) and its relationship to other Plasmodium species

Avian malaria parasites form a highly prevalent and genetically diverse group within the haemosporidians, yet they have long been overlooked relative to their human- and rodent-infecting counterparts. Among these, parasites of the genus Haemoproteus (Haemosporida, Haemoproteidae) are widespread and prevalent blood parasites of birds, transmitted by louse flies (Hippoboscidae) and biting midges (Ceratopogonidae). Recent phylogenomic analyses place Haemoproteus parasites at the root of the haemosporidian tree, making genomic data from these taxa essential for understanding the evolutionary origins of malaria parasites. To date, only two avian Plasmodium and one avian Haemoproteus genomes have been sequenced. We present the first assembled genome of Haemoproteus majoris (lineage WW2), a common blood parasite of passerine birds. As avian erythrocytes are nucleated, parasite DNA was enriched by FACS-based sorting to discriminate and isolate the parasite from host cell nuclei prior to whole-genome amplification. The genome was assembled using Nanopore long-read sequencing and polished with Illumina short-reads, yielding 145 contigs with a total assembly size of 23.9Mb and a G+C content of 27.85%. Genome annotation identified 5501 protein-coding genes, 69 non-coding RNA genes, and 57 long terminal repeat retrotransposons (LRT-RTs), including one full-length element. This genomic resource represents a critical step towards elucidating the evolutionary history and genomic architecture of avian malaria parasites. SIGNIFICANCE STATEMENTWe present the first assembled genome of Haemoproteus majoris (lineage WW2), a prevalent and generalist avian malaria parasite. Taxonomic resolution of this genus is difficult as there are few distinct morphological differences among closely-related species. This genome provides a valuable resource for studying the evolution within the Haemoproteus genus and to elucidate the evolutionary history of malaria parasites.

genomics↗

bioRxiv2025

Single cell transcriptomics and development of gametocyte-specific molecular markers for avian malaria parasites

Avian malaria, caused by Plasmodium parasites, poses a significant threat to bird populations worldwide, particularly in vulnerable island ecosystems. Yet, progress in understanding avian malaria transmission dynamics has been hampered by the lack of molecular tools to quantify and sex the transmissible stages of the parasite: the male and female gametocytes. This challenge is compounded by the nucleated erythrocytes of avian hosts and the absence of an in vitro culture system, which have historically hindered the advancement of molecular approaches. Here, we develop and validate the first molecular markers to discriminate between asexual, male, and female gametocytes in the widespread avian malaria parasite Plasmodium relictum. Using single-cell RNA sequencing and orthology-guided stage mapping, we identified conserved, stage-specific transcripts and leveraged this information to develop molecular markers capable of quantifying and distinguishing male and female gametocytes in two parasite cyt-b lineages, pSGS1 and pDELURB. These markers outperformed microscopy in sensitivity, detected gametocytes earlier and for longer, and revealed consistently higher male-to-female gametocyte ratios than estimated by blood smears. The high degree of conservation of these markers across Plasmodium species suggests broad applicability of these markers to other avian lineages.

molecular biology↗

bioRxiv2024

Beyond immunity: a transcriptomic landscape of Plasmodium's modulation of mosquito metabolic pathways

The focus of mosquito-Plasmodium interactions has predominantly been centered on mosquito immunity, revealing key mechanisms by which mosquitoes attempt to combat Plasmodium infection. However, recent evidence suggests that beyond immunity, a multitude of mosquito physiological and metabolic pathways play crucial roles in determining whether the parasite completes its development within the mosquito. We review which of these metabolic pathways are potentially modulated by Plasmodium, revealing a fragmented and occasionally contradictory state of knowledge. We then present a comprehensive transcriptomic analysis of Plasmodium-infected and uninfected mosquitoes, examining gene expression of crucial genes across different stages of the parasites development. These genes range from key enzymes and proteins involved in gut structure and function, to genes involved in egg production and resorption, salivary gland invasion and mosquito behaviour. For this purpose, we use a non-model system consisting of the avian malaria parasite Plasmodium relictum, an invasive parasite threatening bird biodiversity across the world, and its natural vector, the mosquito Culex pipiens. Our results reveal how at each stage of its development within the mosquito, Plasmodium modulates a myriad of mosquito metabolic pathways, in ways that potentially favour its survival and the completion of its life cycle. We discuss whether this constitutes sufficient evidence of parasite-driven manipulation or whether the changes are simply the mosquitos response to the infection, which the parasite may serendipitously exploit to enhance its fitness. Our study extends the comparative transcriptomic analyses of malaria-infected mosquitoes beyond human and rodent parasites, and provides insights into the degree of conservation of metabolic pathways and into the selective pressures exerted by Plasmodium parasites on their vectors.

genomics↗

bioRxiv2024

West Nile virus is transmitted within mosquito populations through infectious mosquito excreta

Understanding transmission routes of arboviruses is key to control their epidemiology and global health burden. Using West Nile virus and Culex mosquitoes, we tested whether arboviruses are transmitted through mosquito excreta. First, we determined the presence of infectious virions in excreta and quantified a high concentration of infectious units per excreta. Second, we showed that virion excretion starts early after oral infection and remains constant for a long period, regardless of mosquito infection level. These results highlight the infectiousness of excreta from infected mosquitoes. Third, we found that both larvae and pupae were susceptible to infection, although pupae were highly permissive. Forth, we established the proof-of-concept that immature mosqui-toes can be infected by infectious excreta, demonstrating a new excreta-mediated mode of transmission. Finally, by mathematically modelling excreta-mediated transmission in the field, we demonstrated its potential impact on arbovirus epidemiology. Our study uncovers a new route of transmission for arboviruses, unveiling mechanisms of viral maintenance in mosquito reservoirs and of vector species shift that contribute to zoonotic emergence.

zoology↗

bioRxiv2023

Cities as parasitic burden? Malaria prevalence and diversity along an urbanization gradient in great tits

Urbanization is a worldwide phenomenon that modifies the environment. By affecting the reservoirs of pathogens and the body and immune conditions of hosts, urbanization alters the epidemiological dynamics and diversity of diseases. Cities could act as areas of pathogen dilution or amplification, depending on whether urban features have positive or negative effects on vectors and hosts. In this study, we focused on a host species and investigated the prevalence and diversity of avian malaria parasites (Plasmodium/Haemoproteus sp. and Leucocytozoon sp.) in great tits (Parus major) living across an urbanization gradient. In general, we observed high prevalence in adult birds (from 95% to 100%), yet lower prevalence in fledglings (from 0% to 38%). We found a slight tendency for increased Plasmodium sp. prevalence with increasing urbanization in adults. Urban nestlings had higher Plasmodium sp. infection rates than non-urban nestlings. We found evidence of higher diversity of parasites in the most natural urban park; however, parasite diversity was similar across other urbanization levels (e.g. from a little artificialized park to a highly anthropized industrial area). Parasite lineages were not habitat specific. Only one Plasmodium sp. lineage (YWT4) was associated with urban areas and some rare lineages (e.g., AFR065) were present only in a zoo area, perhaps because of the presence of African birds. This study suggests that urbanization can lead to a parasite amplification effect and can favor different avian malaria lineages.

ecology↗

bioRxiv2022

Immune gene expression in the mosquito vector Culex quinquefasciatus during an avian malaria infection

Plasmodium relictum is the most widespread avian malaria parasite in the world. It is listed as one of the 100 most dangerous invasive species, having been responsible for the extinction of several endemic bird species, and the near-demise of several others. Here we present the first transcriptomic study examining the effect of P. relictum on the immune system of its vector (the mosquito Culex quinquefasciatus) at different times post-infection. We show that over 50% of immune genes identified as being part of the Toll pathway and 30-40% of the immune genes identified within the Imd pathway are overexpressed during the critical period spanning the parasites oocyst and sporozoite formation (8-12 days), revealing the crucial role played by both these pathways in this natural mosquito-Plasmodium combination. Comparison of infected mosquitoes with their uninfected counterparts also revealed some unexpected RNA expression patterns earlier and later in the infection: Significant differences in expression of several immune effectors were observed as early as 30 minutes after the ingestion of the infected blood meal. In addition, in the later stages of the infection (towards the end of the mosquito lifespan), we observed an unexpected increase in immune investment in uninfected, but not in infected, mosquitoes. In conclusion, our work extends the comparative transcriptomic analyses of malaria-infected mosquitoes beyond human and rodent parasites and provides insights into the degree of conservation of immune pathways and into the selective pressures exerted by Plasmodium parasites on their vectors.

evolutionary biology↗

bioRxiv2022

Fitness costs and benefits in response to artificial artesunate selection in Plasmodium

AO_SCPLOWBSTRACTC_SCPLOWDrug resistance is a major issue in the control of malaria. Mutations linked to drug resistance often target key metabolic pathways and are therefore expected to be associated with biological costs. The spread of drug resistance depends on the balance between the benefits that these mutations provide in the drug-treated host and the costs they incur in the untreated host. The latter may therefore be expressed both in the vertebrate host and in the vector. Research on the costs of drug resistance focusses on interactions with vertebrate host, yet whether they are also expressed in the vector has been overlooked. In this study, we aim to identify the costs and benefits of resistance against artesunate (AS), one of the main artemisinin derivatives used in malaria-endemic countries. For this purpose, we compared different AS-selected lines of the avian malaria parasite Plasmodium relictum to their ancestral (unselected) counterpart. We tested their within host dynamics and virulence both in the vertebrate host and in its natural vector, the mosquito Culex quinquefasciatus. The within-host dynamics of the AS-selected lines in the treated birds was consistent with the phenotype of resistance described in human P. falciparum malaria: a clearance delay during the treatment followed by a recrudescence once the treatment was interrupted. In the absence of treatment, however, we found no significant costs of resistance in the bird. The results of the two experiments to establish the infectivity of the lines to mosquitoes point towards a decreased infectivity of the drug-selected lines as compared to the ancestral, reference one. We discuss the potential implication of these results on the spread of artesunate resistance in the field.

evolutionary biology↗

bioRxiv2020

The transmission-blocking effects antimalarial drugs revisited: mosquito fitness costs and sporontocidal effects of artesunate and sulfadoxine-pyrimethamine

Assays used to evaluate the transmission-blocking activity of antimalarial drugs are largely focused on their potential to inhibit or reduce the infectivity of gametocytes, the blood stages of the parasite that are responsible for the onward transmission to the mosquito vector. For this purpose, the drug is administered concomitantly with the gametocyte-infected blood, and the results are evaluated as the % reduction in the number of oocysts in the mosquito midgut. We report the results of a series of experiments that explore the transmission blocking potential of two key antimalarial drugs, artesunate (AS) and sulfadoxine-pyrimethamine (SP), when administered to mosquitoes already infected from a previous blood meal. For this purpose, uninfected mosquitoes and mosquitoes carrying a 6-day old Plasmodium relictum infection (early oocyst stages) are allowed to feed either on a drug-treated or an untreated host in a fully factorial experiment. This protocol allows us to bypass the gametocyte stages and establish whether the drugs are able to arrest the ongoing development of oocysts and sporozoites, as would be the case when a mosquito takes a post-infection treated blood meal. In a separate experiment, we also explore whether a drug-treated blood meal impacts key life history traits of the mosquito relevant for transmission, and if this depends on their infection status. Our results show that feeding on an AS- or SP-treated host has no epidemiologically relevant effects on the fitness of infected or uninfected mosquitoes. In contrast, when infected mosquitoes feed on an SP-treated host, we observe both a significant increase in the number of oocysts in the midgut, and a drastic decrease in both sporozoite prevalence (-30%) and burden (-80%) compared to the untreated controls. We discuss the potential mechanisms underlying these seemingly contradictory results and contend that, provided the results are translatable to human malaria, the potential epidemiological and evolutionary consequences of the current preventive use of SP in malaria-endemic countries could be substantial.

evolutionary biology↗