Biology subjects

Rajerison, M.

Publications and source records attributed to Rajerison, M..

3 recordsLinked to original sources

bioRxiv2025

Genetic structure of Rattus rattus populations in an endemic plague focus in Madagascar: implications for rodent surveillance and management

BackgroundPlague remains a major public health concern in Madagascar. In the Central Highlands, where the disease is still endemic, the black rat (Rattus rattus) is the main reservoir of the causative agent Yersinia pestis. Understanding its population dynamics and structure is therefore crucial to inform control strategies, as dispersal may greatly limit the effectiveness of local interventions during outbreaks. In such a context, this study aims at investigating the genetic diversity and temporal structure of R. rattus populations at a fine geographical scale. Methodology/Principal findingsSampling was conducted in six villages of the Ankazobe district, both inside houses and outside villages. A total of 480 individuals, captured in March - May 2019 and 2020, were genotyped at 17 microsatellite loci. Our results show that genetic diversity levels were relatively homogeneous among villages and years. However, subpopulations living outside villages displayed significantly higher genetic diversity and lower genetic differentiation levels than those from inside houses, indicating larger effective population sizes outside villages in the cultivated habitats. These findings suggest more restricted movement among rat subpopulations from the houses, and greater connectivity among subpopulations living outside villages. However, overall genetic differentiation was rather low, suggesting extensive dispersal of rats at the scale of the district, facilitating rapid recolonization after local control efforts. ConclusionAn integrated approach combining flea control within houses together with measures to reduce human-rodent contact would thus appear more appropriate than rodent control only to limit plague transmission.

ecology↗

bioRxiv2024

Global evolutionary patterns of Yersinia pestis and its spread into Africa

The zoonotic pathogen Yersinia pestis, the etiologic agent of plague, has caused three major pandemics and diversified in different lineages currently established in endemic areas worldwide1-3. However, some regions like continental Africa have been poorly covered within the global diversity and epidemiological history of this pathogen2,4-6. Here, we report the whole-genome sequences of 1,124 Y. pestis isolates collected from endemic areas worldwide over 116 years, nearly doubling the available genomic data for the species. By integrating population genomics and historical research, we retrace the introduction of multiple Y. pestis lineages into continental Africa, revealing the diversity of the 1.ANT lineage, its historical emergence and its spread to and within Africa since the late 17th century. We identify key mechanisms of genome evolution, including signatures of adaptive evolution present in virulence and biofilm-related genes such as RovA, a master virulence regulator, which likely play a role in the pathogens adaptation and endemic persistence. Additionally, our findings reveal an increased trajectory of genome degradation and expansion of IS elements in different lineages. This trend appears especially pronounced in 1.ANT genomes, promoting the remarkable genomic variation within this lineage. Taken together, our findings shed light on the introduction and evolutionary history of plague in Africa and provide a comprehensive framework for understanding the global diversity and genome evolution of Y. pestis, revealing potential factors contributing to its long-term adaptation in endemic areas.

microbiology↗

bioRxiv2022

Phylogenetic analysis of the origin and spread of plague in Madagascar

BackgroundPlague is a zoonotic disease caused by the bacterium Yersinia pestis, highly prevalent in the Central Highlands, a mountainous region in the center of Madagascar. After a plague-free period of over 60 years in the northwestern coast city of Mahajanga, the disease reappeared in 1991 and caused several outbreaks until 1999. Previous research indicates that the disease was reintroduced to the city of Mahajanga from the Central Highlands instead of reemerging from a local reservoir. However, it is not clear how many reintroductions occurred and when they took place. Methodology/Principal findingsIn this study we applied a Bayesian phylogeographic model to detect and date migrations of Y. pestis between the two locations that could be linked to the re-emergence of plague in Mahajanga. Genome sequences of 300 Y. pestis strains sampled between 1964 and 2012 were analyzed. Four migrations from the Central Highlands to Mahajanga were detected. Two resulted in persistent transmission in humans, one was responsible for most of the human cases recorded between 1995 and 1999, while the other produced plague cases in 1991 and 1992. We dated the emergence of the Y. pestis sub-branch 1.ORI3, which is only present in Madagascar and Turkey, to the beginning of the 20th century, using a Bayesian molecular dating analysis. The split between 1.ORI3 and its ancestor lineage 1.ORI2 was dated to the second half of the 19th century. Conclusions/SignificanceOur results indicate that two independent migrations from the Central Highlands caused the plague outbreaks in Mahajanga during the 1990s, with both introductions occurring during the early 1980s. They happened over a decade before the detection of human cases, thus the pathogen likely survived in wild reservoirs until the spillover to humans was possible. This study demonstrates the value of Bayesian phylogenetics in elucidating the re-emergence of infectious diseases. Author summaryIn 1991 human cases of plague were reported in the city of Mahajanga, located in the west coast of Madagascar, after 60 years without human cases. Existing evidence suggests that Yersinia pestis, the causal agent of the disease, was reintroduced to the city from a mountainous region known as the Central Highlands. We performed a phylogeographic analysis on 300 Y. pestis genome sequences to determine how many migrations of the pathogen between the two locations were related to the reappearance of the disease in Mahajanga. The results revealed that two migrations from the Central Highlands were the cause of the outbreaks of plague in the west coast of the country during the 1990s. We also aimed to date the emergence of the Y.pestis variant that circulates in Madagascar and is also present in Turkey. To do this, we conducted a molecular dating analysis using an extended data set of 445 sequences, which contained sequences from Turkey and India (the country from which the pathogen was exported to Madagascar for the first time). The analysis indicated that this particular variant emerged in the first decade of the 20th century.

microbiology↗