Modeling the potential of introducing different Wolbachia-infected mosquitoes to control Aedes-borne arboviral infections

Samson Ogunlade developed single and multi-Wolbachia strain(s) invasive models in wild-type mosquitoes. He found that the advantage of Wolbachia retainment in mosquitoes strongly outweighed cytoplasmic incompatibility and releasing mosquitoes with two different strains of Wolbachia did not increase their prevalence, compared with a single-strain Wolbachia-infected mosquito introduction and only delayed Wolbachia dominance. These findings contribute to the mitigation or elimination of global arboviral infections in particular, dengue

A Systematic Review of Mathematical Models of Dengue Transmission and Vector Control: 2010–2020

Vector control methods are considered effective in averting dengue transmission. However, several factors may modify their impact. Of these controls, chemical methods, in the long run, may increase mosquitoes’ resistance to chemicides, thereby decreasing control efficacy. The biological methods, which may be self-sustaining and very effective, could be hampered by seasonality or heatwaves (resulting in, e.g., loss of Wolbachia infection). The environmental methods that could be more effective than the chemical methods are under-investigated. In this study, a systematic review is conducted to explore the present understanding of the effectiveness of vector control approaches via dengue transmission models

Modelling the ecological dynamics of mosquito populations with multiple co-circulating Wolbachia strains

Wolbachia intracellular bacteria successfully reduce the transmissibility of arthropod-borne viruses (arboviruses) when introduced into virus-carrying vectors such as mosquitoes. Despite the progress made by introducing Wolbachia bacteria into the Aedes aegypti wild-type population to control arboviral infections, reports suggest that heat-induced loss-of-Wolbachia-infection as a result of climate change may reverse these gains. Novel, supplemental Wolbachia strains that are more resilient to increased temperatures may circumvent these concerns, and could potentially act synergistically with existing variants. In this article, we model the ecological dynamics among three distinct mosquito (sub)populations: a wild-type population free of any Wolbachia infection; an invading population infected with a particular Wolbachia strain; and a second invading population infected with a distinct Wolbachia strain from that of the first invader. We explore how the range of possible characteristics of each Wolbachia strain impacts mosquito prevalence. Further, we analyse the differential system governing the mosquito populations and the Wolbachia infection dynamics by computing the full set of basic and invasive reproduction numbers and use these to establish stability of identified equilibria. Our results show that releasing mosquitoes with two different strains of Wolbachia did not increase their prevalence, compared with a single-strain Wolbachia-infected mosquito introduction and only delayed Wolbachia dominance

A review: Aedes-borne arboviral infections, controls and Wolbachia-based strategies

Arthropod-borne viruses (Arboviruses) continue to generate significant health and economic burdens for people living in endemic regions. Of these viruses, some of the most important (e.g., dengue, Zika, chikungunya, and yellow fever virus), are transmitted mainly by Aedes mosquitoes. Over the years, viral infection control has targeted vector population reduction and inhibition of arboviral replication and transmission. This control includes the vector control methods which are classified into chemical, environmental, and biological methods. Some of these control methods may be largely experimental (both field and laboratory investigations) or widely practised. Perceptively, one of the biological methods of vector control, in particular, Wolbachia-based control, shows a promising control strategy for eradicating Aedes-borne arboviruses. This can either be through the artificial introduction of Wolbachia, a naturally present bacterium that impedes viral growth in mosquitoes into heterologous Aedes aegypti mosquito vectors (vectors that are not natural hosts of Wolbachia) thereby limiting arboviral transmission or via Aedes albopictus mosquitoes, which naturally harbour Wolbachia infection. These strategies are potentially undermined by the tendency of mosquitoes to lose Wolbachia infection in unfavourable weather conditions (e.g., high temperature) and the inhibitory competitive dynamics among co-circulating Wolbachia strains. The main objective of this review was to critically appraise published articles on vector control strategies and specifically highlight the use of Wolbachia-based control to suppress vector population growth or disrupt viral transmission. We retrieved studies on the control strategies for arboviral transmissions via arthropod vectors and discussed the use of Wolbachia control strategies for eradicating arboviral diseases to identify literature gaps that will be instrumental in developing models to estimate the impact of these control strategies and, in essence, the use of different Wolbachia strains and feature

Seroprevalence of Influenza A Virus in Dromedaries in North-Western Nigeria

Although influenza A virus is endemic in wild waterfowl, domestic poultry, swine, humans, bats, cetaceans, dogs, and horses, there is a paucity of data on the potential role of camels in zoonotic transmission of the virus. To estimate the seroprevalence of the influenza A virus in camel populations, four local government areas of Nigeria that share an international border with the Niger Republic were selected. Blood samples from 184 one-hump camels (dromedaries) were collected and tested for influenza IgG antigen by ELISA. Each camel’s demographic variable, such as age, gender, location, production system, and usage, was recorded. The overall seroprevalence rate of influenza virus IgG in this study was 10.33% (95%CI: 6.33–15.66%). In the bivariate model, there was no significant difference in gender, age, site location and production system, except for usage. There was a significantly lower seroprevalence rate among camels used for labour (odds ratio (OR) = 0.34, 95% CI: 0.10–0.97) than those used for meat consumption; however, not after adjusting for other variables in the model. Increase surveillance through early detection, prediction, and risk assessment of pathogens in animal reservoirs and environmental contamination as One Health strategies to reduce potential human spillover is recommended. Molecular epidemiology studies could better elucidate the role of camels in the dynamics of disease transmission pathways

A Systematic Review of Mathematical Models of Dengue Transmission and Vector Control: 2010–2020

Vector control methods are considered effective in averting dengue transmission. However, several factors may modify their impact. Of these controls, chemical methods, in the long run, may increase mosquitoes’ resistance to chemicides, thereby decreasing control efficacy. The biological methods, which may be self-sustaining and very effective, could be hampered by seasonality or heatwaves (resulting in, e.g., loss of Wolbachia infection). The environmental methods that could be more effective than the chemical methods are under-investigated. In this study, a systematic review is conducted to explore the present understanding of the effectiveness of vector control approaches via dengue transmission models

Modeling Malaria Parasite Survival Strategies in the Human Host

This work focuses on the application of mathematical and statistical modeling to understand malaria infection and the corresponding immune responses in the human host in areas of high malaria exposure.In high malaria endemic areas, seasonal transmission occurs such that during the wet season, individuals are highly exposed to malaria infection but are not in the dry season. This work investigates how repeated exposures to malaria parasites contribute to parasite survival in the host during the dry season. By extending an existing mathematical model, exposure of individuals to P.falciparum infections over their lifetimes were simulated, with the models capturing the generation of partial immunity to these infections. Our model predicts that individuals with repeated exposure to malaria parasites acquire partial immunity with time and this partial immunity is not fully protective but elongates the duration of infection. Counterintuitively, the most protected individuals have the longest infections. Accordingly, I present the hypothesis that individuals with the most exposure and protection from malaria may be the ones responsible for carrying the parasites through the dry season.During the blood stage of malaria infection, when a shizont ruptures and releases merozoites, they must find and invade red blood cells (RBCs). However, it is known that the merozoites have a higher preference for infecting some cells (i.e. reticulocytes) compared to others. This work presents a probabilistic model of the invasion strategy a merozoite uses to find the “best” cell given the trade-off between longer search times and the benefit gained by the parasite. I observed that, different strategies of the parasites yield different susceptibilities of those parasites to killing.Overall, this work demonstrates the use of mathematical and statistical modeling concepts to analyse the strategies of malaria parasites survival which will help in contributing to the elimination of the malaria disease

A Systematic Review of Mathematical Models of Dengue Transmission and Vector Control: 2010–2020

Vector control methods are considered effective in averting dengue transmission. However, several factors may modify their impact. Of these controls, chemical methods, in the long run, may increase mosquitoes’ resistance to chemicides, thereby decreasing control efficacy. The biological methods, which may be self-sustaining and very effective, could be hampered by seasonality or heatwaves (resulting in, e.g., loss of Wolbachia infection). The environmental methods that could be more effective than the chemical methods are under-investigated. In this study, a systematic review is conducted to explore the present understanding of the effectiveness of vector control approaches via dengue transmission models

Modelling the ecological dynamics of mosquito populations with multiple co-circulating Wolbachia strains

Abstract Wolbachia intracellular bacteria successfully reduce the transmissibility of arthropod-borne viruses (arboviruses) when introduced into virus-carrying vectors such as mosquitoes. Despite the progress made by introducing Wolbachia bacteria into the Aedes aegypti wild-type population to control arboviral infections, reports suggest that heat-induced loss-of-Wolbachia-infection as a result of climate change may reverse these gains. Novel, supplemental Wolbachia strains that are more resilient to increased temperatures may circumvent these concerns, and could potentially act synergistically with existing variants. In this article, we model the ecological dynamics among three distinct mosquito (sub)populations: a wild-type population free of any Wolbachia infection; an invading population infected with a particular Wolbachia strain; and a second invading population infected with a distinct Wolbachia strain from that of the first invader. We explore how the range of possible characteristics of each Wolbachia strain impacts mosquito prevalence. Further, we analyse the differential system governing the mosquito populations and the Wolbachia infection dynamics by computing the full set of basic and invasive reproduction numbers and use these to establish stability of identified equilibria. Our results show that releasing mosquitoes with two different strains of Wolbachia did not increase their prevalence, compared with a single-strain Wolbachia-infected mosquito introduction and only delayed Wolbachia dominance

Quantifying the impact of Wolbachia releases on dengue infection in Townsville, Australia

Abstract From October 2014 to February 2019, local authorities in Townsville, North Queensland, Australia continually introduced Wolbachia-infected mosquitoes to control seasonal outbreaks of dengue infection. In this study, we develop a mathematical modelling framework to estimate the effectiveness of this intervention as well as the relative dengue transmission rates of Wolbachia-infected and wild-type mosquitoes. We find that the transmission rate of Wolbachia-infected mosquitoes is reduced approximately by a factor of 20 relative to the uninfected wild-type population. In addition, the Townsville Wolbachia release program led to a 65% reduction in predicted dengue incidence during the release period and over 95% reduction in the 24 months that followed. Finally, to investigate the potential impact of other Wolbachia release programs, we use our estimates of relative transmissibility to calculate the relationship between the reproductive number of dengue and the proportion of Wolbachia-infected mosquitoes in the vector population