Biology subjects

de Jong, M. C. M.

Publications and source records attributed to de Jong, M. C. M..

4 recordsLinked to original sources

bioRxiv2024

Biological tick control: modeling the potential impact of entomopathogenic fungi on the transmission of East Coast fever in cattle

Biological control of ticks using entomopathogenic fungi (EPF) is a highly desired alternative to chemical acaricides for the control of tick-borne pathogens. For Metarhizium anisopliae isolate ICIPE 7, one of these EPFs, efficacy against multiple tick species has been demonstrated in laboratory and field settings. However, we currently have little quantitative understanding of how EPFs can impact transmission. We developed a deterministic model of tick-host-pathogen interactions to explore how the effects of EPF on Rhipicephalus appendiculatus ticks may impact the transmission dynamics of East Coast fever (ECF) in cattle populations. We parameterized the multi-faceted effects of EPFs on tick dynamics using experimental data on Tickoff(R) biopesticide (a novel formulation of M. anisopliae ICIPE 7) and related EPFs. The epidemiological impact of EPF was evaluated across a range of product profiles and implementation strategies. Model results indicate that, for the explored product profiles, EPF derives most of its epidemiological impact through the delayed mortality effect. This EPF-induced mortality could not only reduce the onward Theileria parva transmission to cattle (both treated and untreated) but could also cause a reduction in the tick-to-host ratio and thus cattle exposure to ticks. The effects of EPF on reproduction fitness and engorgement of ticks elicit negligible impact. High levels of population coverage and treatment frequency are needed to reduce the tick population size and reach meaningful epidemiological impact in cattle populations. Additionally, increasing the persistence time of fungal conidia on cattle skin - through technological improvements to the EPF formulation - can substantially reduce acute infections when combined with appreciable population coverage levels, treatment frequency, and efficient spraying techniques. Our model analysis provides insights into the potential impact of EPF when deployed at a population level, and lends support to further research and development of this biological tick control tool.

microbiology↗

bioRxiv2023

Quantifying Rift Valley fever virus transmission efficiency in a lamb-mosquito-lamb model

Rift Valley fever virus (RVFV) is a (re)emerging mosquito-borne pathogen impacting human and animal health. How RVFV spreads through a population depends on population-level interactions between hosts and vectors (e.g., vector-to-host ratio and biting preference) and also on potential differences in individual following virus exposure (e.g., transmission efficiencies from host to vector and vice versa). Here, we estimated the probability for RVFV to transmit to naive animals by experimentally exposing lambs to a bite of an infectious mosquito (the transmission efficiency) and assessed if and how RVFV infection subsequently developed in the exposed animal. Aedes aegypti mosquitoes, previously infected via feeding on a viremic lamb, were used to expose naive lambs to the virus. Lambs were either exposed to 1-3 (low exposure) or 7-9 (high exposure) infectious mosquitoes. All lambs in the high exposure group became viremic and showed characteristic signs of Rift Valley fever within 2-4 days post exposure. In contrast, 3 out of 12 lambs in the low exposure group developed viremia and disease, with similar peaks in viremia as the high exposure group but with some heterogeneity in the onset of viremia. These results suggest that the likelihood for successful infection of a ruminant host is affected by the number of infectious mosquitoes biting, but also highlights that a lamb can be infected by a single mosquito. The per bite mosquito-to-host transmission efficiency was estimated at 28% (95% confidence interval: 15 - 47%). We subsequently combined this transmission efficiency with estimates for mosquito life traits into a Ross-McDonald mathematical model to illustrate scenarios under which major RVFV outbreaks could occur in naive populations (i.e., R0 >1). The model revealed that for efficient RVFV transmission relatively high vector-to-host ratios as well as strong feeding preference for competent hosts are required. Altogether, this study highlights the importance of experiments that mimic natural exposure to RVFV. The experiments facilitate a better understanding of the natural progression of disease and a direct way to obtain epidemiological parameters for mathematical models.

microbiology↗

bioRxiv2022

Efficient direct and limited environmental transmission of SARS-CoV-2 lineage B.1.22 in domestic cats

Susceptibility of domestic cats for infection with SARS-CoV-2 has been demonstrated by several experimental studies and field observations. We performed an extensive study to further characterize transmission of SARS-CoV-2 between cats, both by direct contact as well as by indirect contact. To that end, we estimated the transmission rate parameter and the decay parameter for infectivity in the environment. Using four groups of pair-transmission experiment, all donor (inoculated) cats became infected, shed virus and seroconverted, while three out of four direct contact cats got infected, shed virus and two of those seroconverted. One out of eight cats exposed to a SARS-CoV-2-contaminated environment became infected but did not seroconvert. Statistical analysis of the transmission data gives a reproduction number R0 of 2.18 (95% CI: (0.92-4.08), a transmission rate parameter {beta} of 0.23 day-1 (95% CI: 0.06-0.54), and a virus decay rate parameter of 2.73 day-1 (95% CI: 0.77-15.82). These data indicate that transmission between cats can be sustained (R0>1), however, infectiousness of a contaminated environment decays rapidly (mean duration of infectiousness 1/2.73 days). Infections of cats via exposure to a SARS-CoV-2-contaminated environment cannot be excluded if cats are exposed shortly after contamination.

microbiology↗

bioRxiv2021

Habitat loss exacerbates pathogen spread: An Agent-based model of avian influenza infection in migratory waterfowl

Habitat availability determines the distribution of migratory waterfowl along their flyway, which further influences the transmission and spatial spread of avian influenza viruses (AIVs). The extensive habitat loss in the East Asian-Australasian Flyway (EAAF) may have potentially altered the virus transmission and spread, but those consequences are rarely studied. We constructed 6 fall migration networks that differed in their level of habitat loss, wherein an increase in habitat loss resulted in smaller networks with fewer sites. The networks were integrated with an agent-based model and a susceptible-infected-recovered model to simulate waterfowl migration and AIV transmission. We found that extensive habitat loss in the EAAF can 1) relocate the outbreaks northwards responding to the distribution changes of wintering waterfowl geese, 2) increase the outbreak risk in remaining sites due to larger bird congregations, and 3) facilitate AIV transmission among wintering geese. Our modelling output suggested that there was a certain system resilience of migration network to confront the site removal. In addition, the outputs were in line with the predictions from the concept of "migratory escape", affecting the pattern of infection prevalence in the waterfowl population. Our modelling shed light on the potential consequences of habitat loss in transmitting and spreading AIV at the flyway scale, and suggested the driving mechanisms behind these effects, advocating the importance of nature conservation in changing spatial and temporal patterns of AIV outbreak. Author summaryWhat are the possible consequences of extensive habitat loss on the transmission and spread of avian influenza viruses (AIVs)? We used a logistic regression model to select the suitable habitats of Greater white-fronted goose in the East Asian-Australasian Flyway and treated these habitats as sites to construct 6 fall migration networks that differed in their level of habitat loss (i.e., site removal). We then simulate geese migration in these networks, and explore the impacts of habitat loss on habitat connectivity and AIV transmission. We found the extensive habitat loss can cause relocation of the outbreaks and increase the outbreak risk and AIV transmission. Our modelling outputs suggested a certain network resilience to confront the site loss, and a "migratory escape" to change the spatial and temporal pattern of infection prevalence in the population. Overall, our study showed that land use changes and habitat loss can affect disease distribution and prevalence, suggested the importance of habitat conservation in changing the spatial and temporal pattern of AIVs transmission and spread.

ecology↗