Biology subjects

Christe, P.

Publications and source records attributed to Christe, P..

5 recordsLinked to original sources

bioRxiv2024

Impact of vertebrate host parasitaemia on Plasmodium development within mosquitoes

BackgroundIn vector-borne diseases, invertebrate hosts are exposed to highly variable quantities of parasites during their blood meal. This heterogeneity may partly explain the overdispersed distribution of parasites within the vector population, as well as the variability in the extrinsic incubation period (EIP) of the parasite. Indeed, the quantity of parasites ingested is often considered as a good predictor of the quantity of parasites that will develop within the vectors, as well as the speed at which they will develop (EIP). However, density-dependent processes can strongly influence the relationship between parasite burden in the vertebrate host and in vectors, making this relationship not always clear. MethodsHere, we used the avian malaria system to investigate whether the proportion of red blood cells infected by sexual and/or asexual stages of malaria parasite influences the intensity of malaria infection and the EIP of Plasmodium within the invertebrate vectors. For this purpose, we have experimentally infected twelve vertebrate hosts in order to generate a range of intensity of infection. More than a thousand mosquitoes took a blood meal on these hosts and the development of Plasmodium within the vectors was followed for more than 20 days. ResultsThe main finding presented in this study reveals a negative relationship between the intensity of infection in the vertebrate host and the EIP. Four days were sufficient for 10% of infected mosquitoes fed on the most infected hosts to become infectious. However, the number of transmissible stages did not significantly vary according to the vertebrate host intensity of infection. ConclusionWhile the quantity of ingested parasites had no impact on the density of transmissible stages in infectious mosquitoes, the EIP was affected. Studies have demonstrated that small changes in the EIP can have a significant effect on the number of mosquitoes living long enough to transmit parasites. Here, we observed a difference of 4-6 days in the detection of the first transmissible stages, depending on the intensity of infection of the bitten vertebrate host. Considering that a gonotrophic cycle lasts 3-4 days, the shortened EIP observed here may have significant effects on Plasmodium transmission.

pathology↗

bioRxiv2023

Spring reproductive success influences autumnal malarial load in a passerine bird

Although avian haemosporidian parasites are widely used as model organisms to study fundamental questions in evolutionary and behavorial ecology of host-parasite interactions, some of their basic characteristics, such as seasonal variations in within-host density, are still mostly unknown. In addition, their interplay with host reproductive success in the wild seems to depend on the interaction of many factors, starting with host and parasite species and the temporal scale under study. Here, we monitored the parasitemia of two haemosporidian parasites - Plasmodium relictum (lineage SGS1) and P. homonucleophilum (lineage SW2) - in two wild populations of great tits (Parus major) in Switzerland over three years, to characterize their dynamics. We also collected data on birds reproductive output - laying date, clutch size, fledging success - to determine whether they were associated with parasitemia before (winter), during (spring) and after (autumn) breeding season. Parasitemia of both species dramatically increased in spring, in a way that was correlated to parasitemia in winter. Parasitemia before and during breeding season did not explain reproductive success. However, the birds which fledged the more chicks had higher parasitemia in autumn, which was not associated with their parasitemia in previous spring. Our results tend to indicate that high haemosporidian parasite loads do not impair reproduction in great tits, but high resource allocation into reproduction can leave birds less able to maintain low parasitemia over the following months.

ecology↗

bioRxiv2021

Determinants of haemosporidian single and co-infections risks in western paleartic birds

Co-infections with multiple pathogens are common in the wild and may act as a strong selective pressure on both host and parasite evolution. Yet, contrary to single infection, the factors that shape co-infection risk are largely under-investigated. Here, we explored the extent to which bird ecology and phylogeny impact single and co-infection probabilities by haemosporidian parasites using large datasets from museum collections and a Bayesian phylogenetic modelling framework. While both phylogeny and species attributes (e.g. size of the geographic range, life-history strategy, migration) were relevant predictors of co-infection risk, these factors were less pertinent in predicting the probability of being single infected. Our study suggests that co-infection risk is under a stronger deterministic control than single-infection risk. These results underscore the combined influence of host evolutionary history and species attributes in determining single and co-infection pattern providing new avenues regarding our ability to predict infection risk in the wild.

ecology↗

bioRxiv2020

Last-come, best served? Mosquito biting order and Plasmodium transmission

A pervasive characteristic of malaria parasite infection in mosquito vector populations is their tendency to be overdispersed. Understanding the mechanisms underlying the overdispersed distribution of parasites is of key importance as it may drastically impact the transmission dynamics of the pathogen. The small fraction of heavily infected individuals might serve as superspreaders and cause a disproportionate number of subsequent infections. Although multiple factors ranging from environmental stochasticity to inter-individual heterogeneity may explain parasite overdispersion, Plasmodium infection has also been observed to be highly overdispersed in inbred mosquito population maintained under standardized laboratory conditions, suggesting that other mechanisms may be at play. Here, we show that the aggregated distribution of Plasmodium within mosquito vectors is partially explained by a temporal heterogeneity in parasite infectivity triggered by the bites of blood-feeding mosquitoes. Several experimental blocks carried out with three different Plasmodium isolates have consistently shown that the transmission of the parasite increases progressively with the order of mosquito bites. Surprisingly the increase in transmission is not associated with an increase in Plasmodium replication rate or higher investment in the production of the transmissible stage (gametocyte). Adjustment of the physiological state of the gametocytes could be, however, an adaptive strategy to respond promptly to mosquito bites. Overall our data show that malaria parasite appears to be able to respond to the bites of mosquitoes to increase its own transmission at a much faster pace than initially thought (hours rather than days). Further work needs to be carried out to elucidate whether these two strategies are complementary and, particularly, what are their respective underlaying mechanisms. Understanding the processes underlying the temporal fluctuations in Plasmodium infectivity throughout vertebrate host-to-mosquito transmission is essential and could lead to the development of new approaches to control malaria transmission. Author summaryPlasmodium parasites are known for being the etiological agents of malaria and for the devastating effects they cause on human populations. A pervasive characteristic of Plasmodium infection is their tendency to be overdispersed in mosquito vector populations: the majority of mosquitoes tend to harbour few or no parasites while a few individuals harbor the vast majority of the parasite population. Understanding the mechanisms underlying Plasmodium overdispersed distribution is of key importance as it may drastically impact the transmission dynamics of the pathogen. Here, we show that the aggregated distribution of Plasmodium parasites within mosquito vectors is partially explained by a temporal heterogeneity in Plasmodium infectivity triggered by the bites of blood-feeding mosquitoes. In other words, mosquitoes that bite at the beginning of a 3h feeding session have significantly fewer parasites than those that bite towards the end. Malaria parasite is therefore capable of responding to the bites of mosquitoes to increase its own transmission at a much faster pace than thought (hours rather than days). Understanding the processes underlying the temporal fluctuations in Plasmodium infectivity throughout vertebrate host-to-mosquito transmission is essential and could lead to the development of new approaches to control malaria transmission.

microbiology↗

bioRxiv2019

Opening Pandora’s Box: Distribution of Plasmodium gametocytes in bloodstream

Malaria, a vector borne disease caused by Plasmodium spp., remains a major global cause of morbidity and mortality. Optimization of the disease control strategies requires a thorough understanding of the fundamental processes underlying parasite transmission. Although the number of transmissible stages of Plasmodium (gametocyte) in human blood is frequently used as an indicator of human-to-mosquito transmission potential, this relationship is not always clear. Important efforts have been made to develop molecular tools to fine-tune gametocyte densities estimation and therefore improve the prediction of mosquito infection rates, but a significant level of uncertainty around this estimate remains. Here we show with both human and avian malaria system that the within-vertebrate host distribution of gametocytes could explain much of this uncertainty. By comparing gametocyte densities in bloodstream between different body parts, we found a difference by nearly 50% in humans and by more than 15% in birds. An estimation of gametocyte density from only one blood sample, as is usually the case, could therefore drastically over- or underestimated the infectivity of gametocyte carriers. This might have important consequences on the epidemiology of the disease since we show, using the avian malaria system, that this variation influences the transmission of the parasite to the mosquito vector. In the light of our results, we argue that it is essential to consider the heterogeneous distribution of gametocyte to improve human diagnosis, identify infectious reservoirs and to test new malaria control strategies.

evolutionary biology↗