Biology subjects

Mariën, J.

Publications and source records attributed to Mariën, J..

9 recordsLinked to original sources

bioRxiv2025

Microparasite prevalence in Southern giant pouched rats (Cricetomys ansorgei) in Morogoro, Tanzania.

Rodents play a critical role in the transmission of zoonotic pathogens, with environmental changes and increasing human-wildlife interactions further amplifying disease spillover risks. Cricetomys spp., commonly found in both human dwellings and agricultural fields, are frequently hunted for consumption, potentially facilitating pathogen transmission. However, their roles in pathogen transmission and disease ecology remain poorly understood. This study investigated the prevalence of three microparasite genera, i.e., Bartonella, Hepatozoon, and Anaplasma, in Cricetomys spp. from Morogoro, Tanzania. We observed a prevalence of 71.9% for Bartonella, 17.5% for Hepatozoon, and 1.8% for Anaplasma. To our knowledge, this is the first study to investigate Bartonella, Hepatozoon, and Anaplasma in Cricetomys spp. in Tanzania. Furthermore, preliminary results indicate that Bartonella infection prevalence is influenced by habitat type, with a significantly higher prevalence observed in rural areas compared to urban areas. This study underscores the potential role of Cricetomys spp. as important reservoirs of infectious diseases.

ecology↗

bioRxiv2025

Efficiency of Anthelmintic Treatment and Its Effect on Microparasite Dynamics in Wild Mastomys natalensis

Co-infections between helminths and microparasites can influence disease dynamics with potential public health implications. However, establishing clear cause-and-effect relationships from natural populations remains challenging. One approach to address this is through perturbation experiments, where a specific parasite is selectively reduced to directly observe its impact on co-infecting parasites. While such experiments have been conducted in wild rodent populations, they have not yet been explored in Africa, despite the continents importance for emerging infectious diseases and zoonoses. In this study, we investigated potential helminth-microparasite interactions in wild Mastomys natalensis in Tanzania by using anthelmintics to reduce helminth infections. We first assessed the efficacy of two anthelmintic treatments, ivermectin and pyrantel pamoate, in wild-caught M. natalensis, finding that both treatments significantly reduced gastrointestinal nematodes, with pyrantel pamoate being more effective than ivermectin. Additionally, we examined how helminth reduction influenced microparasite prevalence. Our results show that pyrantel pamoate treatment was associated with a decrease in Morogoro virus seropositivity over time, while anthelmintic treatment had no significant effect on Bartonella infection probability.

ecology↗

bioRxiv2024

A wide diversity of viruses detected in African mammals involved in the wild meat supply chain

The processes involved in acquiring, trading, preparing, and consuming wild meat pose significant risks for the emergence of zoonotic infectious diseases. Several major viral outbreaks have been directly linked to the wild meat supply chain, yet our knowledge of the virome in many mammals involved in this chain remains limited and disproportionately focused on certain mammalian taxa and pathogens. This report presents the findings of a metagenomic viral screening of 99 specimens belonging to 27 wild African mammal species and one domesticated species, all traded for their meat. The study focuses on tissue and swab samples collected from various regions in the Democratic Republic of the Congo and in Brussels, Belgium. A total of fifteen virus strains were detected, belonging to the families Arteriviridae, Retroviridae and Sedoreoviridae (primates), Picobirnaviridae (primates and rodents), Picornaviridae (rodents), Hepadnaviridae (hyrax), Orthoherpesviridae (artiodactylid and carnivore) and Spinareoviridae (carnivore). Several strains were detected in mammalian hosts for the first time, expanding their host range and genetic diversity. Of note is the presence of viruses genetically related to recognised zoonotic pathogens, i.e., human picobirnavirus (Orthopicobirnavirus hominis) (primates and rodents), simian foamy viruses (Simiispumavirus) (primates), and rotavirus A (Rotavirus alphagastroenteritidis) (primates). The presence of these viruses in primates is concerning as non-human primates are phylogenetically closely related to humans, which can facilitate interspecies viral transmission. These findings underscore the high diversity of mammalian viruses and the potential risk of human infection through cross-species transmission during the close interactions with wildlife in the wild meat supply chain.

genomics↗

bioRxiv2024

Assessing Ebola Virus Circulation in the Tshuapa Province (Democratic Republic of the Congo): A One Health Investigation of Wildlife and Human Interactions

The wildlife reservoir and spillover mechanisms of the Ebola virus remain elusive despite extensive research efforts in endemic areas. This study employed a One Health approach to examine the virus circulation in wildlife and the associated human exposure risks in the Tshuapa province of the Democratic Republic of the Congo. In 2021, we collected 1015 samples from 888 animals, predominantly small mammals, and 380 inhabitants of Inkanamongo village, the site of an Ebola virus disease outbreak in 2014. These samples were screened for evidence of current (RNA) or past (IgG antibodies) Ebola virus infections. We also conducted interviews with 167 individuals in the surrounding districts to assess their interactions with wildlife. While no Ebola virus RNA was detected in the wildlife samples, anti-orthoebolavirus IgG antibodies were found in 13 bats and 38 rodents. Among the human participants, 120 individuals had IgG antibodies against at least one orthoebolavirus antigen, with 12 showing seropositivity for two antigens of the same orthoebolavirus, despite not having a prior Ebola disease diagnosis. Furthermore, over 50% of respondents reported frequent visits to the forest to hunt a variety of wild animals, particularly ungulates and rodents, which could account for occasional viral spillovers. The absence of active Ebola virus circulation in wildlife may reflect seasonal patterns in reservoir ecology, like those observed in bats. Similarly, seasonal human activities, like hunting and foraging, may result in periodic exposure risks. These findings highlight the importance of continuous, multidisciplinary surveillance to monitor changes in seasonal spillover risks.

molecular biology↗

bioRxiv2022

Incorporating space in hierarchical capture mark recapture models: can we better capture variance?

Capture mark recapture (CMR) models allow the estimation of various components of animal populations, such as survival and recapture probabilities. In recent years, incorporating the spatial distribution of the devices used to detect an animals presence has become possible. By incorporating spatial information, we explicitly acknowledge the fact that there will be spatial structuring in the ecological processes which give rise to the capture data. Individual detection probability is not heterogeneous for a range of different reasons, for example the location of traps within an individuals home range, the environmental context around the trap or the individual characteristics of an animal such as its age. Spatial capture recapture models incorporate this heterogeneity by including the spatial coordinates of traps, data which is often already collected in standard CMR approaches. Here, we compared how the inclusion of spatial data changed estimations of survival, detection probability, and to some extent the probability of seroconversion to a common arenavirus, using the multimammate mouse as our model system. We used a Bayesian framework to develop non spatial, partially spatial and fully spatial models alongside multievent CMR models. First, we used simulations to test whether certain parameters were sensitive to starting parameters, and whether models were able to return the expected values. Then we applied the non-spatial, partially spatial and fully spatial models to a real dataset. We found that bias and precision were similar for the three different model types, with simulations always returning estimates within the 95% credible intervals. When applying our models to the real data set, we found that the non-spatial model predicted a lower survival of individuals exposed to Morogoro virus (MORV) compared to unexposed individuals, yet in the spatial model survival between exposed and non-exposed individuals was the same. This suggests that the non-spatial model underestimated the survival of seropositive individuals, most likely due to an age effect. We suggest that spatial coordinates of traps should always be recorded when carrying out CMR and spatially explicit methods of analysis should be used whenever possible, particularly as incorporating spatial variation may more easily capture ecological processes without the need for additional data collection that can be challenging to acquire with wild animals.

ecology↗

bioRxiv2021

Insecticide susceptibility of Aedes (Stegomyia) aegypti (Linnaeus, 1762) and Aedes (Stegomyia) albopictus (Skuse, 1894) in Kinshasa, Democratic Republic of the Congo

Aedes aegypti and Aedes albopictus are arbovirus vectors of public health concern. Although the Democratic Republic of the Congo (DRC) faces a long-standing risk of Aedes-borne viruses, data on insecticide resistance of Aedes populations are absent. To address this gap, we investigated insecticide susceptibility of Ae. aegypti and Ae. albopictus in areas with a high risk of arbovirus transmission. We also investigated the frequency of knock-down resistance (kdr) mutations in Ae. aegypti. Immature stages of Ae. aegypti and Ae. albopictus were collected from two sites in Kinshasa (Lingwala and Cite Verte) between April and July 2017 and reared to the adult stage. Wild-caught adult Ae. aegypti were collected in 2016 in another site (Ngaliema). Female Ae. aegypti (from Lingwala) and Ae. albopictus (from Cite Verte) were used in WHO tube insecticide susceptibility tests. The F1534C, V1016I and V410L kdr mutations were genotyped in Ae. aegypti from Lingwala and Ngaliema. We observed Ae. aegypti to be susceptible to bendiocarb, propoxur and malathion, suspected resistant to permethrin, and resistant to deltamethrin and DDT. Aedes albopictus was susceptible to bendiocarb, propoxur, malathion and permethrin, suspected resistant to deltamethrin and resistant to DDT. While F1534C and V1016I were not detected, a few Ae. aegypti from Lingwala were heterozygous for the mutation V410L. This study reports for the first time the insecticide resistance status of Aedes spp. and the detection of the kdr mutation V410L in Ae. aegypti in DRC. Given the resistance profile, carbamates and potentially malathion are recommended insecticide options against Ae. aegypti in Kinshasa. It will be important to develop Aedes control strategies based on the resistance patterns of Aedes in Kinshasa.

ecology↗

bioRxiv2021

Population genetic bottleneck has only marginal effects on fitness evolution and its repeatability in dioecious C. elegans

The predictability of evolution is expected to depend on the relative contribution of deterministic and stochastic processes. This ratio is modulated by effective population size. Smaller effective populations harbor less genetic diversity and stochastic processes are generally expected to play a larger role, leading to less repeatable evolutionary trajectories. Empirical insight into the relationship between effective population size and repeatability is limited and focused mostly on asexual organisms. Here, we tested whether fitness evolution was less repeatable after a population bottleneck in obligately outcrossing populations of Caenorhabditis elegans. Replicated populations founded by 500, 50, or 5 individuals (no/moderate/strong bottleneck) were exposed to a novel environment with a different bacterial prey. As a proxy for fitness, population size was measured after one week of growth before and after 15 weeks of evolution. Surprisingly, we found no significant differences among treatments in their fitness evolution. Even though the strong bottleneck reduced the relative contribution of selection to fitness variation, this did not translate to a significant reduction in the repeatability of fitness evolution. Thus, although a bottleneck reduced the contribution of deterministic processes, we conclude that the predictability of evolution may not universally depend on effective population size, especially in sexual organisms.

evolutionary biology↗

bioRxiv2018

Gene regulatory mechanisms underlying the evolutionary loss of a polygenic trait

Trait loss is a pervasive phenomenon in evolution, yet the underlying molecular causes have been identified in only a handful of cases. Most of these involve loss-of-function mutations in one or more trait-specific genes. Parasitoid insects are fatty acid auxotrophs: they lost the ability to convert dietary sugars into fatty acids, a trait that is ubiquitous among non-parasitoid animals and is enabled by a highly conserved set of genes. Earlier research suggests that lack of lipogenesis is caused by changes in gene regulation, rather than gene decay. We compared transcriptome-wide responses to sugar-feeding in the non-lipogenic parasitoid species Nasonia vitripennis and the lipogenic Drosophila melanogaster. Both species adjusted their metabolism within four hours after feeding, but there was little overlap at the gene level between the responses of the two species. Even at the pathway-level, there were sharp differences between the expression profiles of the two species, especially in carbohydrate and lipid metabolic pathways. Several genes coding for key enzymes in acetyl-CoA metabolism, such as malonyl-CoA decarboxylase (MCD) and HMG-CoA synthase differed in expression between the two species. Their combined action likely blocks lipogenesis in the parasitoid species. Network analysis indicates most genes involved in these pathways to be highly connected, which suggest they have pleiotropic effects and could explain the absence of gene degradation. Our results indicate that modification of expression levels of only a few non-connected genes, such as MCD, is sufficient to enable complete loss of lipogenesis in N. vitripennis.

evolutionary biology↗

bioRxiv2018

Genomic resources for Goniozus legneri, Aleochara bilineata and Paykullia maculata, representing three independent origins of the parasitoid lifestyle in insects

Parasitoid insects are important model systems for a multitude of biological research topics and widely used as biological control agents against insect pests. While the parasitoid lifestyle has evolved numerous times in different insect groups, research has focused almost exclusively on Hymenoptera from the parasitica clade. The genomes of several members of this group have been sequenced, but no genomic resources are available from any of the other, independent evolutionary origins of the parasitoid lifestyle. Our aim here was to develop genomic resources for three parasitoid insects outside the parasitica. We present draft genome assemblies for Goniozus legneri, a parasitoid Hymenopteran more closely related to the non-parasitoid wasps and bees than to the parasitica wasps, the Coleopteran parasitoid Aleochara bilineata and the Dipteran parasitoid Paykullia maculata. The genome assemblies are fragmented, but complete in terms of gene content. We also provide preliminary structural annotations. We anticipate that these genomic resources will be valuable for testing the generality of findings obtained from parasitica wasps in future comparative studies.\n\nData availabilityThe Whole Genome Shotgun projects have been deposited at DDBJ/ENA/GenBank under the accessions NCVS00000000 (G. legneri), NBZA00000000 (A. bilineata) and NDXZ00000000 (P. maculata). The versions described in this paper are versions NCVS01000000, NBZA01000000 and NDXZ01000000, respectively. Mapped reads and genome annotations are available through http://parasitoids.labs.vu.nl/parasitoids/. This website also includes genome browsers and viroblast instances for each genome.

genomics↗