Biology subjects

Mercier, A.

Publications and source records attributed to Mercier, A..

3 recordsLinked to original sources

bioRxiv2019

The polyphagous plant pathogenic fungus Botrytis cinerea encompasses host-specialized and generalist populations

The host plant is often the main variable explaining population structure in fungal plant pathogens, because specialization contributes to reduce gene flow between populations associated with different hosts. Previous population genetic analysis revealed that French populations of the grey mould pathogen Botrytis cinerea were structured by hosts tomato and grapevine, suggesting host specialization in this highly polyphagous pathogen. However, these findings raised questions about the magnitude of this specialization and the possibility of specialization to other hosts. Here we report specialization of B. cinerea populations to tomato and grapevine hosts but not to other tested plants. Population genetic analysis revealed two pathogen clusters associated with tomato and grapevine, while the other clusters co-occurred on hydrangea, strawberry and bramble. Measurements of quantitative pathogenicity were consistent with host specialization of populations found on tomato, and to a lesser extent, populations found on grapevine. Pathogen populations from hydrangea and strawberry appeared to be generalist, while populations from bramble may be weakly specialized. Our results suggest that the polyphagous B. cinerea is more accurately described as a collection of generalist and specialist individuals in populations. This work opens new perspectives for grey mold management, while suggesting spatial optimization of crop organization within agricultural landscapes.

microbiology↗

bioRxiv2019

Toxoplasma gondii in house mice Mus musculus domesticus from Dakar, Senegal: clues for oral rather than vertical mode of infection

Toxoplasma gondii is an ubiquitous highly prevalent zoonotic protozoan. Cats are the definitive hosts, while all other warm-blooded animals are intermediate hosts for this parasite. Commensal rodents, being the main preys of cats, are probably the major reservoir for T. gondii. Rodents often develop dormant tissue cysts after ingestion of oocysts shed in the environment by cats in the form of contaminated feces. Experimental evidence that vertical transmission can be sufficient to the perpetuation of transmission between generations of mice has also been found. In natural settings, the relative epidemiological importance of vertical transmission over oral transmission is a matter of debate and raises the question of the possibility of a T. gondii cycle in the absence of cats. In the present study, we took advantage of an extensive survey of commensal rodents in Dakar, Senegal, where the house mouse Mus musculus domesticus is the predominant putative reservoir of T. gondii. Host genotype and spatial location through GPS referencing of all trapping localizations were investigated in relation to T. gondii infection in 12 sites of the city of Dakar and on Goree Island. In each sampled site, the occurrence of over-prevalence zones of T. gondii infection was investigated through Kulldorfs statistic using SaTScan software. For the sites where a possible over-prevalence zone was identified, mice family lines were inferred from Discriminant Analysis of Principal Components (DAPC). In 3 of the 4 identified possible over-prevalence zones, T. gondii infection was not confined to a single family line, which suggested no association between kinship and infection occurrence. This finding rather suggests an environmental source of infection for mice associated with localized putative foci of environmental contamination and supports an oral route of infection for mice from Dakar rather than a cycle based on vertical transmission.

epidemiology↗

bioRxiv2019

The native European Aedes geniculatus mosquito species can transmit Chikungunya virus

Europe is the worlds leading tourism destination and is receiving every year travelers from areas with active arbovirus transmission. There is thus a threat of mosquito-borne virus emergence in Europe due to the presence of the invasive mosquito vector Aedes albopictus. Little attention has been paid about the possible role of indigenous mosquito species as vectors of emerging arboviruses. Here, we assessed the vector competence dynamic of Ae. geniculatus, a European anthropophilic mosquito species, for chikungunya virus (CHIKV) in comparison with Ae. albopictus. We revealed that Ae. geniculatus was highly susceptible to CHIKV infection and could transmit the virus. By specifically exploring the vector competence dynamic in both mosquito species, we revealed that the cumulative distribution of CHIKV incubation period in Ae. geniculatus was delayed by several days as compared to Ae. albopictus. Our results strengthen the importance of considering indigenous species as potential vectors for emerging arboviruses. They also revealed the importance of considering variation in arbovirus dissemination or transmission dynamics in mosquitoes when performing vector competence assays. We will discuss the implications of our results on a CHIKV outbreak dynamic in a theoretical framework. Sentence summaryThe European mosquito Aedes geniculatus is highly susceptible to CHIKV infection but disseminate and transmit the virus several days later than Ae. albopictus.

epidemiology↗