Biology subjects

Zohdy, S.

Publications and source records attributed to Zohdy, S..

11 recordsLinked to original sources

bioRxiv2026

Evidence of Anopheles stephensi involvement in the transmission of Plasmodium vivax in Djibouti, 2024

PurposeAnopheles stephensi is a malaria mosquito vector that has been raising international concern due to its invasive nature in Africa, including the nation of Djibouti. Since its initial detection in Djibouti in 2012, malaria morbidity and mortality have increased exponentially in the county. While there is an observed association increase in human malaria cases since the arrival of An. stephensi, high-quality evidence of An. stephensi carrying infective sporozoites is essential to determine the role of the invasive vector in malaria dynamics in Djibouti. This study seeks to confirm the link between An. stephensi and malaria transmission in Djibouti and examine genetic relatedness between Djiboutian An. stephensi populations and populations across the Horn of Africa. Such information regarding the An. stephensi populations and the Plasmodium species they transmit is necessary to devise appropriate control strategies and limit malaria transmission within and beyond the country. MethodsOne hundred and ninety-six adult An. stephensi mosquitoes from Djibouti were collected, molecularly confirmed, analyzed for a portion of the cytochrome c oxidase subunit 1 (COI), and tested for infective sporozoites using a highly sensitive and specific multiplex circumsporozoite enzyme linked immunosorbent assay (csELISA) bead assay. The COI sequences of one hundred and fourteen samples were further used to characterize the population genetic structure of the sampled An. stephensi and its genetic relatedness to other An. stephensi populations across the Horn of Africa. ResultsAll 196 samples were morphologically and molecularly confirmed to be An. stephensi. Plasmodium vivax210 sporozoites were detected with a positivity rate of 1.02%. An analysis of the COI region showed that the infected An. stephensi have the most prevalent COI haplotypes of invasive An. stephensi circulating in the Horn of Africa. ConclusionsThe findings from this study confirm the involvement of An. stephensi in P. vivax transmission in Djibouti and describe the genetic relatedness of Djiboutian An. stephensi populations to other populations across the Horn of Africa. This highlights the threat of An. stephensi invasion and supports a rapid and comprehensive response to mitigate the harm that An. stephensi populations cause, particularly through surveillance and control of adult populations. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=119 SRC="FIGDIR/small/707780v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@19f762corg.highwire.dtl.DTLVardef@7624forg.highwire.dtl.DTLVardef@c7492borg.highwire.dtl.DTLVardef@194c11f_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2025

An evaluation of longitudinal Anopheles stephensi egg viability and resistance to desiccation over time

Anopheles stephensi, a malaria vector in South Asia and parts of the Middle East, has been detected as an invasive species in numerous African countries in recent years. It threatens to increase malaria disease burden and reverse gains made in malaria control and elimination over the past decades on the continent. To halt further expansion, it is critical to understand the biological characteristics that may have facilitated An. stephensi range expansion to Africa. In its invasive range, An. stephensi larvae have been found to colonize artificial containers, many of which are shared with Aedes aegypti. The success of Ae. aegypti as an invasive vector is often attributed to the use of artificial containers and the ability of Ae. aegypti eggs to remain viable in the absence of water for months. While An. stephensi is found in artificial containers, it is unclear whether the eggs can remain viable without water for extended periods. Anopheles stephensi eggs were reported to remain viable in soil for up to 12 days in a study done almost 100 years ago, but this work has not been revisited since. Thus, in this present study, we used egg batches (>100 eggs per batch) from two laboratory strains of An. stephensi (SDA500 and STE2) from South Asia and one Ae. aegypti strain (LVP-IB12) to evaluate 1) whether An. stephensi eggs can remain viable like Ae. aegypti when egg substrates are completely dried following standard insectary methods for drying out Aedes aegypti egg sheets, and 2) assess egg viability duration at varying temperatures (15{degrees}C, 20{degrees}C, 25{degrees}C 30{degrees}C, 35{degrees}C) when eggs are held on a moistened substrate in a high humidity environment. Anopheles stephensi egg viability and subsequent larval survival was observed consistently when moistened egg sheets were held at 15{degrees}C in a high humidity (>75% RH) environment for up to 14 days in both strains. Anopheles stephensi eggs were not viable when dried following standard insectary Aedes aegypti methods for drying out egg sheets, except when the protocol was amended to include a 15{degrees}C storage temperature. Though egg viability and larval survival was observed in the amended protocol for SDA500 and STE2 (16% and 21% respectively), it was significantly less than that of LVP-IB12 (83%) and was only observed in the egg batches stored for the shortest timepoint (seven days post egg collection, three days post complete drying of egg sheets). These findings suggest that An. stephensi may remain viable if eggs are transported under ideal conditions (15{degrees}C and >75% RH) through trade or commerce routes. Thus, the persistence of An. stephensi eggs in the absence of water should be considered in programs that engage in surveillance and control of An. stephensi in Africa.

ecology↗

bioRxiv2025

Anopheles stephensi larval habitat superproductivity and its relevance for larval source management in Africa

The invasion of Africa by Anopheles stephensi poses a significant threat to malaria elimination. As An. stephensi exploits a wide array of urban artificial larval habitats, it may be less impacted by rainfall variability compared to other native Anopheles species. We empirically investigated this assumption by quantifying the seasonal transition of an established population from eastern Ethiopia between rainy and dry periods. Monthly larval surveys generated evidence of significant heterogeneity between seasons in the type of habitat and their productivity. As the dry season progressed, An. stephensi productivity significantly concentrated in large water reservoirs (for drinking and construction) to a point in which up to 77% of all larvae originated from 23% of the sites. Such superproductive sites were primarily water cisterns used for residential or construction purposes. A two-patch metapopulation model of An. stephensi linked to rainfall data recreated the seasonal larval dynamics observed in the field and predicted that larval control targeted on superproducer water reservoirs, when implemented at coverages higher than 60%, may lead to An. stephensi elimination. Our findings highlight the role of environmental variability in regulating An. stephensi populations and open the window for the deployment of control strategies that exploit major mosquito population bottlenecks.

ecology↗

bioRxiv2024

Community-Based Entomological Surveillance and Control of Vector-Borne Diseases: A Scoping Review

Community-based surveillance and control methods (CBMs) present opportunities to decentralize surveillance and control efforts while simultaneously enhancing community education, leadership, and participation in the fight against vector-borne diseases (VBDs). A scoping review was conducted to describe how CBMs are being utilized currently to combat malaria, dengue fever, Chagas disease, tick-borne diseases (TBDs) and other mosquito-borne diseases (MBD) exclusive of dengue and malaria, and to overall highlight key approaches, lessons learned, potential challenges, and recommendations. A total of 304 potential publications were identified among which 82 met the inclusion criteria. This scoping review highlighted the following benefits to CBMs: cost savings, increased sustainability, increased community knowledge, human behavior changes, increased surveillance coverage, ease in deployment, and the creation of larger, more diverse entomological datasets. Potential challenges highlighted include: participant retention and motivation, participant recruitment and incentives, continued governmental support, data quality, and collaboration with local municipal authorities. CBMs are commonly and successfully used in vector surveillance and control systems, but the chosen vector management method varies by vector-borne disease and region of the world. Additional research is needed to support the implementation of CBMs including cost-effectiveness studies and those studies with negative outcomes. Taken together, this scoping review highlights key aspects, potential challenges, and benefits of CBMs, and outlines potential future directions for incorporating CBMs into VBD control and elimination programming, and potential for community based integrated vector management (IVM) approaches.

scientific communication and education↗

bioRxiv2024

Insecticide resistance and population structure of the invasive malaria vector, Anopheles stephensi, from Fiq, Ethiopia

Anopheles stephensi invasion in Ethiopia poses a risk of increased malaria disease burden in the region. Thus, understanding the insecticide resistance profile and population structure of the recently detected An. stephensi population in Fiq, Ethiopia, is critical to inform vector control to stop the spread of this invasive malaria species in the country. Following entomological surveillance for An. stephensi in Fiq, Somali region, Ethiopia, we confirmed the presence of An. stephensi morphologically and molecularly in Fiq. Characterization of larval habitats and insecticide susceptibility tests revealed that Fiq An. stephensi is most often found in artificial containers and is resistant to most adult insecticides tested (organophosphates, carbamates, pyrethroids) except for pirimiphos-methyl and PBO-pyrethroids. However, the immature larval stage was susceptible to temephos. Further comparative genomic analyses with previous An. stephensi populations from Ethiopia using 1,704 biallelic SNPs revealed genetic relatedness between Fiq An. stephensi and east-central Ethiopia An. stephensi populations, particularly Jigjiga An. stephensi. Our findings of the insecticide resistance profile, coupled with the likely source population of Fiq An. stephensi, can inform vector control strategies against this malaria vector in Fiq and Jigjiga to limit further spread out of these two locations to other parts of the country and continent.

evolutionary biology↗

bioRxiv2024

A rapid, cost-effective, colorimetric LAMP assay (CLASS) for detecting invasive malaria vector, Anopheles stephensi

Anopheles stephensi, an invasive malaria vector in Africa, has the potential to impact the landscape of malaria on the continent, threatening to put an additional 126 million people per year at risk of malaria, largely in peri-urban/urban areas. To accelerate the early detection and rapid response to An. stephensi and ensure no gains made in malaria control and elimination are lost, it is critical to confirm the presence of the species and the geographic extent of its spread to inform control. However, morphological identification may be misinterpreted if specimens are damaged and existing molecular species confirmation assays require specialized laboratory equipment and training and may be challenging to interpret, requiring additional sequencing confirmation. A colorimetric rapid loop-mediated isothermal amplification (LAMP) assay for molecular An. stephensi species identification was developed and optimized. The colorimetric assay requires only a heat source and reagents and can be used with or without DNA extraction resulting in positive color change in 30-35 minutes. To determine analytical sensitivity, a 1:10 dilution series of the DNA extract was conducted showing 100% assay sensitivity down to 0.003 nanograms. To determine specificity, three different An. stephensi laboratory strains (STE2, SDA 500, UCI), 8 other Anopheles mosquito species, and Aedes aegypti were compared, and the results indicated 100% specificity across these species. To determine use without the need for DNA extraction, samples evaluated included a single mosquito leg, whole adult or larval mosquitoes, and pooled DNA extract from several mosquito species. A total of 1687 individual reactions were tested during optimization and all LAMP assay results were compared against the conventional PCR assay and confirmed through Sanger sequencing. To validate the optimized assay on wild caught specimens, DNA extracted from 12 wild caught, sequence-confirmed An. stephensi from Marsabit, Kenya, were tested and the colorimetric assay was accurate in identifying all of the specimens as An. stephensi. The assay described presents an opportunity to accelerate An. stephensi molecular identification in new and existing locations in Africa, within its endemic range, and globally. These findings present a simple, rapid, unique alternative to existing PCR and sequencing-based An. stephensi species identification and confirmation strategies. With additional field validation studies, molecular screening tools like the colorimetric LAMP-based An. stephensi species identification (CLASS) assay fill an important gap of rapid confirmation of this invasive vector and presents an ideal opportunity to better understand the spread of the species in Africa and other recently invaded areas, thus accelerating a response to mitigate its long-term impacts on malaria on the continent.

molecular biology↗

bioRxiv2023

A regional One Health approach to the risk of invasion by Anopheles stephensi in Mauritius

BackgroundAnopheles stephensi is an invasive malaria vector in Africa that threatens to put an additional 126 million people at risk of malaria if it continues to spread. The island nation of Mauritius is highly connected to Asia and Africa and is at risk of introduction due to this connectivity. For early detection of An. stephensi, the Vector Biology and Control Division under the Ministry of Health in Mauritius, leveraged a well-established Aedes program, as An. stephensi is known to share Aedes habitats. These efforts triggered multisectoral coordination and cascading benefits of integrated vector and One Health approaches. MethodsBeginning June 2021, entomological surveys were conducted at points of entry (seaport, airport) and on ships transporting livestock in collaboration with the Civil Aviation Department, the Mauritian Port Authority and National Veterinary Services. A total of 39, 18, 723 mosquito larval surveys were respectively conducted in the seaport, airport and other localities in Mauritius while 20, two and 26 adult mosquito surveys were respectively conducted in the seaport, airport and twenty-six animal points. Alongside adult mosquito surveys, surveillance of vectors of veterinary importance (e.g.- licoides spp.) was also carried out in collaboration with National Parks and Conservation Service and land owners. ResultsA total of 8,428 adult mosquitoes were collected and 1,844 larval habitats were positive for mosquitoes. All collected mosquitoes were morphologically identified and 151 Anopheles and 339 Aedes mosquitoes were also molecularly characterized. Mosquito species detected were Aedes albopictus, Anopheles arabiensis, An. coustani, An. merus, Culex quinquefasciatus, Cx. thalassius and Lutzia tigripes. Anopheles stephensi was not detected. The One Health approach was shared with the French Agricultural Research Centre for International Development (CIRAD), strengthening collaboration between Mauritius and Reunion Island on vector surveillance at entry points and insecticide resistance monitoring. The Indian Ocean Commission (IOC) was also alerted to the risk of An. stephensi, leading to regional efforts supporting trainings and development of a response strategy to An. stephensi bringing together stakeholders from Comoros, Madagascar, Mauritius, Reunion Island and Seychelles. ConclusionsMauritius is a model system showing how existing public health entomology capabilities can be used to enhance vector surveillance and control and create multisectoral networks to respond to any emerging public and veterinary health vector-borne disease threat. Author summaryThe malaria mosquito, Anopheles stephensi, is invasive in Africa where it threatens to put an additional 126 million people at risk of malaria if it continues to spread throughout the continent. The island nation of Mauritius is highly connected to Asia and Africa through maritime trade and therefore may be at risk of An. stephensi introduction and establishment. Mauritius implemented a One Health approach, enhancing entomological surveillance at entry points and collaborating across sectors (e.g. veterinary services, sea and air port authorities, national parks and conservation, communities, etc.) conducted extensive integrated vector surveillance, inspecting 85,071 larval habitats, and analyzing 8,428 adult mosquitoes morphologically and molecularly. Although An. stephensi was not detected, the initiative catalyzed and strengthened multisectoral partnerships nationally and across the Indian Ocean region member states (Comoros, Madagascar, Mauritius, Reunion Island and Seychelles). Leveraging the threat of An. stephensi, Mauritius exemplifies utilizing existing capabilities to create multisectoral networks for effective vector surveillance and response.

ecology↗

bioRxiv2022

Mosquito invasion via the global shipping network is slowed in high-risk areas by on-shore and ship-board monitoring

The global shipping network (GSN) has been suggested as a pathway for the establishment and reintroduction of Aedes aegypti and Aedes albopictus primarily via the tire trade. We used historical maritime movement data in combination with an agent-based model to understand invasion risk in the United States Gulf Coast and how the risk of these invasions could be reduced. We found a strong correlation between the total number of cargo ship arrivals at each port and likelihood of arrival by both Ae. aegypti and Ae. albopictus. Additionally, in 2012, 99.2% of the arrivals into target ports had most recently visited ports occupied by both Ae. aegypti and Ae. albopictus, increasing risk of Aedes invasion. Model results indicated that detection and removal of mosquitoes from containers when they are unloaded at a port may be more effective in reducing the establishment of mosquito populations compared to eradication efforts that occur while onboard the vessel, suggesting detection efforts should be focused on unloaded containers. To reduce the risk of invasion and reintroduction of Ae. aegypti and Ae. albopictus, surveillance and control efforts should be employed when containers leave high risk locations and when they arrive in ports at high risk of establishment.

ecology↗

bioRxiv2022

Parasite and pathogen prevalence in our closest animal companions is determined by accessibility of sanitation services

Despite the critical role parasites play in ecosystem functioning and their considerable influence on human society, little is known about their variations in abundance on a global scale. This gap in knowledge is amplified by a lack of holistic understanding on how the abundance of parasites of wildlife and humans varies across environmental and socioeconomic gradients, despite a need to integrate study of parasites across social and environmental spheres. Free-roaming companion animals (e.g., domestic cats (Felis catus) and dogs (Canis lupus familiaris)) share pathogens and have frequent contact with humans and wildlife. Thus, they are an effective model to understand how parasite and pathogen prevalence of humans and wildlife varies across environmental and socioeconomic gradients. Through a global systematic review and analysis of socioeconomic and environmental variables, including per capita GDP, income disparity, sanitation, biodiversity, island habitation, and latitude, we find that sanitation and island habitation best explained free-roaming companion animal parasite and pathogen prevalence. Sanitation was significantly associated with parasite and pathogen prevalence in free-roaming companion animals, such that for every 10% increase in the proportion of the human population with improved sanitation access, parasite and pathogen prevalence in free-roaming companion animals decreased by 12% (5-19%, 95% C.L.; p = 0.0023). Since companion animals share many parasites with humans and wildlife, these results suggest that actionable interventions to improve sanitation access could reduce parasite and pathogen exposure risks from companion animals to humans and wildlife. Significance StatementIn addition to playing a critical role in ecosystem functioning, parasites also influence human health, behavior, and society. Further, parasites are also impacted by human activities, as much as by ecological phenomena in natural environments. Despite these dualities, little is known about their variations in abundance on a global scale across environmental and socioeconomic gradients. Using free-roaming companion animals (e.g., domestic cats (Felis catus) and dogs (Canis lupus familiaris)) as a model system, we find that access to safely managed sanitation services is strongly associated with parasite and pathogen prevalence. This finding underscores improvements to sanitation as an actionable One Health intervention that could reduce parasite and pathogen exposure risks from companion animals to humans and wildlife.

ecology↗

bioRxiv2021

Using marine cargo traffic to identify countries in Africa with greatest risk of invasion by Anopheles stephensi

Anopheles stephensi is an efficient malaria vector commonly found in South Asia and the Arabian Peninsula, but in recent years it has established as an invasive species in the Horn of Africa (HoA). In this region, An. stephensi was first detected in a livestock quarantine station near a major seaport in Djibouti in 2012, in Ethiopia in 2016, in Sudan in 2018 and Somalia in 2019. Anopheles stephensi often uses artificial containers as larval habitats, which may facilitate introduction through maritime trade as has been seen with other invasive container breeding mosquitoes. If An. stephensi is being introduced through maritime traffic, prioritization exercises are needed to identify locations at greatest risk of An. stephensi introduction for early detection and rapid response, limiting further invasion opportunities. Here, we use UNCTAD maritime trade data to 1) identify coastal African countries which were most highly connected to select An. stephensi endemic countries in 2011, prior to initial detection in Africa, 2) develop a ranked prioritization list of countries based on likelihood of An. stephensi introduction for 2016 and 2020 based on maritime trade alone and maritime trade and habitat suitability, and 3) use network analysis to describe intracontinental maritime trade and eigenvector centrality to determine likely paths of further introduction on the continent if An. stephensi is detected in a new location. Our results show that in 2011, Sudan and Djibouti were ranked as the top two countries with likelihood of An. stephensi introduction based on maritime trade alone, and these were indeed the first two coastal countries in the HoA where An. stephensi was detected. Trade data from 2020 with Djibouti and Sudan included as source populations identify Egypt, Kenya, Mauritius, Tanzania, and Morocco as the top five countries with likelihood of An. stephensi introduction. When factoring in habitat suitability, Egypt, Kenya, Tanzania, Morocco, and Libya are ranked highest. Network analysis revealed that the countries with the highest eigenvector centrality scores, and therefore highest degrees of connectivity with other coastal African nations were South Africa (0.175), Mauritius (0.159), Ghana (0.159), Togo (0.157), and Morocco (0.044) and therefore detection of An. stephensi in any one of these locations has a higher potential to cascade further across the continent via maritime trade than those with lower eigenvector centrality scores. Taken together, these data could serve as tools to prioritize efforts for An. stephensi surveillance and control in Africa. Surveillance in seaports of countries at greatest risk of introduction may serve as an early warning system for the detection of An. stephensi, providing opportunities to limit further introduction and expansion of this invasive malaria vector in Africa.

ecology↗

bioRxiv2021

Tracking of Anopheles stephensi in Ethiopia using mitochondrial DNA reveals pattern of spread

The recent detection of the South Asian malaria vector Anopheles stephensi in the Horn of Africa (HOA) raises concerns about the impact of this mosquito on malaria transmission in the region. The mode and history of introduction is important for predicting the likelihood of continued introduction and future spread. Analysis of An. stephensi genetic diversity and population structure can provide insight into the history of the mosquito in the HOA. We investigated genetic diversity of An. stephensi in eastern Ethiopia where detection suggests a range expansion to this region to understand the history of this invasive population. We sequenced the cytochrome oxidase subunit I (COI) and cytochrome B gene (CytB) in 187 An. stephensi collected from 10 sites in Ethiopia in 2018. Phylogenetic analyses using a maximum-likelihood approach and minimum spanning network were conducted for Ethiopian sequences. Molecular identification of bloodmeal sources was also performed using universal vertebrate CytB sequencing. Six COI-CytB haplotypes were observed based on five segregating sites, with the highest number of haplotypes in the northeastern sites (Semera, Bati, and Gewana towns) relative to the southeastern sites (Kebridehar, Godey, and Degehabur) in eastern Ethiopia. In the phylogenetic and network analysis, we observed population differentiation based on the distribution of the haplotypes across the northeastern and central sites (Erer Gota, Dire Dawa, and Awash Sebat Kilo) compared to the southeastern sites and evidence of a South Asian origin of the HOA An. stephensi lineages. The presence of the putative South Asian haplotype of origin at sites closest to Ethiopias northeastern borders support route of introductions into Ethiopia from the northeast. Finally, molecular bloodmeal analysis revealed evidence of feeding on bovines, goats, dogs, and humans, as well as evidence of multiple (mixed) blood meals. In conclusion, we find support for the hypothesis for the recent expansion of An. stephensi into southeastern Ethiopia with multiple introductions. We also find evidence that supports the hypothesis that HOA An. stephensi populations originate from South Asia rather than the Arabian Peninsula. The evidence of both zoophagic and anthropophagic feeding support the potential for livestock movement to play a role in vector spread in this region.

ecology↗