Search Results (133)

Rift Valley fever virus (RVFV) is a zoonotic, vector-borne disease affecting livestock and humans. The consumption of raw unpasteurized milk has been epidemiologically linked to RVFV exposure in humans and recognized as a potentially important non-vector route for RVFV transmission. This study aims to investigate the potential of RVFV transmission to humans through the consumption of infected raw milk. For this purpose, we conducted agent-based stochastic simulations to assess the potential for RVFV transmission through ingestion of contaminated raw milk. We created synthetic populations of cows, humans, and mosquitoes representing local farm dynamics in Kisumu, Kenya. A total of 1000 farms were simulated with binomial and Poisson distributions utilized to generate cow and human populations, respectively. Given our prior field data, we varied the probability of consuming raw milk from 1% to 80%. We also varied the probability of infectious raw milk causing RVFV infection at 10% and 40%. Results indicate that when the probability of infectious raw milk causing an infection is set at 10%, the cumulative incidence of RVFV infections in humans through raw milk consumption varies between 0.4 and 13% during the inter-epidemic periods. When the probability of infectious raw milk causing an infection is set at 40%, the percentage of cumulative milk infections ranges from 3.7 to 28%. Findings highlight the great potential for RVFV infection and spread through infectious milk consumption and the need for further evaluation of milk as a potential pathway of RVFV transmission to humans. Raw milk consumption in RVFV endemic settings remains an ongoing public health threat. Full article

Rift Valley fever (RVF) is a climate-sensitive mosquito-borne zoonosis long regarded as a rural, pastoral disease, yet accelerating tropical urbanization and intensifying climate variability may be reshaping its epidemiology at the urban–peri-urban interface. This narrative review examines how global climate change and urban-specific climatic conditions jointly shape RVF virus (RVFV) vector habitats, transmission, and burden in tropical and subtropical cities, synthesizing 51 of 412 English-language records identified by a structured, non-systematic search of PubMed, Scopus, Web of Science, and Google Scholar (2009–2026) and selected for relevance to urban and peri-urban RVF. This research draws on human, livestock, and vector evidence from Sub-Saharan Africa, the Arabian Peninsula, and Indian Ocean islands across epidemic and inter-epidemic periods. The synthesis indicates that impervious surfaces, poor drainage, and open water storage can recreate the water-retaining function of rural dambos, sustaining a year-round larval habitat, and that Culex quinquefasciatus dominance together with peri-urban cattle may form an amplification bridge to humans. Direct evidence remains scarce, anchored by a single peri-urban serosurvey and limited urban slaughterhouse entomology. Critical gaps include urban primary-vector ecology, infection-rate data, urban-heat effects, city-specific exposure studies, and coupled climate–urban burden models. We conclude that RVF is a plausible emerging urban threat warranting proactive inter-epidemic surveillance and integration of RVF into urban planning and One Health systems. Full article

Assessing mosquito vector competence for emerging arboviruses, including the underlying determinants of infection, is a foundational line of investigation towards understanding arbovirus transmission dynamics and vector–virus interactions. We developed a novel quantitative immune gene array that measures the relative expression of 22 immune genes with functional representation across five major immune pathways using quantitative reverse-transcriptase polymerase chain reaction. Homologous primers were developed for Culex tarsalis, Cx. quinquefasciatus, and Ae. aegypti mosquitoes. As an initial pilot test for this array, Cx. tarsalis and Ae. aegypti mosquitoes were orally challenged with Rift Valley fever virus (RVFV) MP12 strain. Midguts, legs/wings, and salivary glands were harvested at 3 and 7 days post-challenge. Differential gene expression was measured against Rpl32 as a housekeeping gene. This assay was sensitive enough to generate results for single mosquito midgut and salivary gland tissues, providing an initial snapshot of the types of gene expression patterns that can be observed for two mosquito species infected with MP12. This new tool will be broadly applicable for assessing mosquito immune profiles for arbovirus infection across major immune genes in five key pathways, as well as generating comparable results across mosquito and arbovirus systems. Full article

Rift Valley fever (RVF) is a mosquito-borne viral zoonosis that causes severe illness in livestock and humans, with significant economic and health repercussions. Mauritania is considered an RVF focus in West Africa. A cross-sectional survey was conducted in 2023 in 12 of Mauritania’s 15 provinces. Serum samples from 849 small ruminants (428 goats and 421 sheep) were analyzed by ELISA for IgG and IgM antibodies against RVF virus. Logistic regression analyses were performed to assess associations between seropositivity and species, age, sex, season, and geographic location. In total, 14.1% of the animals tested were positive for anti-RVFV IgG antibodies. There was no association between anti-RVFV IgG positivity and the ruminant species, the sex, the age and the season. Hodh El Gharbi had the highest seroprevalence (40.5%), followed by Adrar (19.8%) and Tagant (19.7%). The lowest levels were recorded in Tiris Zemmour (2%) and Inchiri (3%). Only two animals tested positive for IgM, suggesting limited recent viral activity. This nationwide survey confirms widespread exposure of small ruminants to RVFV in Mauritania. Strengthening longitudinal serological monitoring and integrating ecological and entomological data within the “One Health” approach will be essential to preventing future epidemics and protecting animal and human health. Full article

Rift Valley fever virus (RVFV) and Crimean–Congo hemorrhagic fever virus (CCHFV) are endemic zoonotic pathogens in Senegal, transmitted by mosquitoes and ticks, respectively. Understanding the seasonal and spatial dynamics of their vectors is essential to improve targeted surveillance. This study investigated the abundance, diversity, and viral infection status of vector populations in a transboundary region (Matam) and a non-transboundary region (Thiès) over two seasons from September 2022 to March 2024. We collected mosquitoes using CO₂-baited CDC light traps and sampled ticks directly from domestic small ruminants. A total of 6558 mosquitoes across 23 species and 1904 ticks representing seven species were morphologically identified. Mosquito abundance peaked significantly during the rainy season. Conversely, tick diversity increased during the dry season, with Hyalomma rufipes emerging as the predominant species. Crucially, RVFV was detected exclusively in Aedes vexans mosquito pools from the transboundary Matam region, emphasizing the epidemiological risk associated with cross-border livestock mobility. Viral RNA of CCHFV was detected in multiple tick species across both regions and seasons, confirming a sustained, multi-vector enzootic cycle. These findings demonstrate persistent RVFV and CCHFV circulation in Senegal and highlight the critical need for integrated, season-specific vector surveillance frameworks. Full article

Background: Rift Valley fever virus (RVFV) is a mosquito-borne zoonotic pathogen that has caused repeated epidemics across Africa and the Arabian Peninsula, posing a severe and growing threat to public health and livestock. Infection in ruminants causes high neonatal mortality and catastrophic abortion storms; human disease ranges from self-limiting febrile illness to hemorrhagic fever, encephalitis, and permanent blindness. No licensed human vaccines or specific antiviral therapeutics are available, creating an urgent unmet medical need. Methods: We systematically reviewed the peer-reviewed literature on RVFV neutralizing antibodies (NAbs), extracting and synthesizing data on antibody sources, epitope specificity, in vitro neutralizing potency, in vivo protective efficacy, and molecular mechanisms of action. Results: A growing body of work has identified potent NAbs from immunized rodents, rabbits, alpacas, non-human primates, and convalescent patients. These NAbs predominantly target the Gn and Gc envelope glycoproteins. Their mechanisms include blocking host receptor (LRP1) binding, preventing the pH-dependent conformational rearrangement of the Gn–Gc complex, and directly inhibiting viral membrane fusion. Lead candidates, such as RVFV-268 and RVFV-140, achieve sub-nanogram neutralization and confer robust protection in rodent models against lethal challenge, aerosol exposure, and vertical transmission. Bispecific antibodies and combination strategies further enhance potency and the genetic barrier to viral escape. Conclusions: Substantial progress has illuminated the epitope landscape and neutralization mechanisms of RVFV, yielding promising clinical candidates. Translational challenges remain, including viral immune escape, antibody thermostability, and the need for rigorous preclinical evaluation. Future efforts should prioritize structure-guided engineering, rational antibody combinations, and testing in clinically predictive animal models. Full article

In 2024 Kenya had a population of 4.78 million camels that contributed to the livelihoods of pastoralist communities in northern Kenya. Previous studies in Kenya, Saudi Arabia and eastern Africa demonstrated high seroprevalence of Middle East respiratory syndrome coronavirus (MERS-CoV)-specific antibodies in dromedary camels, as well as sporadic transmission of MERS-CoV from camels to humans. Based on the MERS-CoV data and the very close contact between owners and their camels in northern Kenya, we speculated that camels may also transmit other zoonotic viruses, such as Rift Valley fever virus (RVFV). In this study, 493 camel and 197 human sera were collected in Marsabit, Kenya, through a cross-sectional survey in 2018 and analyzed for the presence of RVFV IgG antibodies using a laboratory-developed indirect enzyme-linked immunosorbent assay (ELISA). Overall, 15.6% of camels and 7.6% of humans were RVFV IgG-positive; IgG-positive camels were predominantly females in large population herds and IgG-positive humans were engaged in farming-related activities and were greater than 18 years old. Of the eight location groups sampled, two had high camel (site 2 and site 6) and two had high human (site 5 and site 6) RVFV seropositivity rates. These data suggest that camelids, such as dromedary camels, may serve as amplifying hosts for vector-borne zoonotic diseases, such as RVFV, and that humans with frequent farming and camel meat, milk, or camel product contact may have increased risk for RVFV exposure or infection. Full article

Rift Valley fever virus (RVFV) and Crimean-Congo hemorrhagic fever virus (CCHFV) are designated by the World Health Organization as priority pathogens due to their epidemic potential, zoonotic transmission, and the absence of licensed therapeutics or vaccines. The development of effective antivirals critically relies on robust in vitro and in vivo models; however, progress is limited by the requirement for high-containment facilities. In this review, we provide a comprehensive overview of the experimental models currently available for RVFV and CCHFV, ranging from cell-based assays to animal models, and discuss their respective advantages, limitations, and translational relevance. We further highlight strategies allowing for BSL-2 experimentations, thereby expanding research accessibility, and accelerating the development of countermeasures against these high-priority pathogens. Full article

Rift Valley fever virus (RVFV) is a re-emerging, vector-borne pathogen endemic to Africa and the Arabian Peninsula, posing an increasing threat to human and animal health. Outbreaks have severe economic and social impacts on farmers, communities, and governments. Current diagnostic methods rely on PCR and ELISA; however, rapid pen-side tests would enable faster, cost-effective monitoring and outbreak control. Here, a species- and immunoglobulin class-independent capillary flow immunodiagnostic assay (lateral flow test; LFT) for detecting RVFV-specific antibodies is described. The assay uses a double-antigen approach, coupling the RVFV nucleocapsid protein, a major viral antigen, both to carbon nanoparticles and to a nitrocellulose membrane. The method was qualified with immune sera from sheep, calves, goats, and humans and benchmarked against a newly developed double-antigen ELISA and a commercial competition ELISA. Both the LFT and double-antigen ELISA demonstrated high specificity and sensitivity. This advancement brings RVFV-specific pen-side testing significantly closer to practical implementation. Full article

Background: Rift Valley fever virus (RVFV) is a significant mosquito-borne zoonotic virus with high public health and veterinary importance in Africa and the Middle East. Reliable diagnostic assays for detecting antibodies and assessing their functional neutralizing capacity are essential for surveillance programs, vaccine monitoring, and outbreak preparedness. Objective: This study evaluates and compares the analytical performance of a competitive enzyme-linked immunosorbent assay (cELISA) and a virus neutralization test (VNT) for detecting RVFV antibodies in vaccinated sheep sera, establishing an integrated laboratory workflow for virus titration, serological detection, and functional neutralization. Methods: Twenty serum samples were collected from sheep pre-vaccination and one month post-vaccination with Smithburn live attenuated RVFV vaccine. Sera were tested using a commercial multispecies RVFV competitive ELISA to detect antibodies specific to the viral nucleocapsid protein. Viral titration was conducted in Vero cells, and 50% tissue culture infective dose (TCID₅₀/0.1 mL) was calculated using the Reed and Muench method. VNT was performed at 24, 48, 72, and 96 h after infection with different viral doses (10² to 10⁵ TCID₅₀/0.1 mL), and the neutralizing ability of serial serum dilutions (1:2 to 1:1024) was tested. Compared with the control, protection was determined by cytopathic effect (CPE) inhibition. Results: ELISA revealed robust antibody signals up to a 1:32 dilution, with signal-to-noise (S/N) < 40%, whereas for higher dilutions, antibody detection became inconclusive or negative. Virus titration was performed to verify a stock concentration of 10^6.5 TCID₅₀/0.1 mL. The VNT exhibited time- and dose-dependent kinetics; high protection rates (≥97) were observed at 1:2–1:8 dilutions against 10²–10³ TCID₅₀/0.1 mL challenge doses; however, neutralizing efficacy decreased significantly at higher viral loads and higher serum dilutions. While cELISA and VNT results correlated strongly at low serum dilutions, the cELISA showed decreased sensitivity at dilutions ≥ 1:64, where the VNT remained capable of detecting functional neutralizing activity. Conclusions/Discussion: The results demonstrate that while both assays correlate well at high antibody concentrations, they diverge at lower concentrations. This discrepancy highlights the functional difference between binding antibodies (N-protein) and neutralizing antibodies (Gn/Gc glycoproteins). Consequently, the cELISA is ideal for rapid screening, whereas the VNT is indispensable for confirming functional immunity. Integrating both assays provides a more accurate immunological profile for RVFV surveillance and vaccine evaluation. Full article

Rift Valley Fever (RVF) is a neglected vector-borne zoonotic disease of significant veterinary and public health concern in Sub-Saharan Africa. This study investigated the seroprevalence of Rift Valley Fever Virus (RVFV) exposure and associated risk factors among camels and horses marketed in northern Nigeria. A total of 1117 animals were sampled, comprising camels (812) and horses (305), across three major livestock markets (Maigatari, Maiduguri, and Illela). The overall seroprevalence was 18.8% (95% CI: 16.6–21.2%), with a striking six-fold disparity: camels showed a prevalence of 24.4% (95% CI: 21.6–27.4%), while horses exhibited only 3.9% (95% CI: 2.1–7.0%). Significant geographic clustering was observed, with Illela camels recording the highest prevalence (34.8%) compared to those in Maigatari (20.3%) and Maiduguri (20.2%). There were no significant associations with age or sex among camels. However, in horses, females were significantly more likely to test positive than males (OR = 0.27, 95% CI: 0.07–0.97). These findings demonstrate endemic RVFV circulation in Nigerian livestock, highlighting species- and location-specific differences, and underscore the zoonotic risks within regional and transboundary livestock trade networks. Full article

The Rift Valley fever virus (RVFV) is a highly pathogenic, mosquito-borne zoonotic virus that poses a significant risk to livestock, human health, and global public health security. Although RVFV is classified by the World Health Organization (WHO) as a priority pathogen with epidemic potential, no licensed vaccines or effective antiviral therapies are currently available. A limited understanding of the molecular mechanisms of RVFV entry has hindered therapeutic development. Here, we elucidate the molecular basis by which the RVFV envelope glycoprotein Gn recognizes its receptor, low-density lipoprotein receptor-related protein 1 (LRP1). Bio-layer interferometry (BLI) demonstrates that full-length LRP1 directly binds the head domain of Gn with nanomolar affinity in a Ca²⁺-dependent manner. Both LRP1 clusters II (CL II) and IV (CL IV) independently interact with Gn, with CL IV exhibiting stronger affinity, indicating a multivalent recognition mode. Structural modeling using AlphaFold 3 reveals pronounced charge complementarity between basic residues on Gn and acidic, Ca²⁺-coordinated pockets within LRP1. Mutations in key acidic residues in CL IV greatly reduced Gn binding, confirming the essential roles of Ca²⁺ coordination and electrostatic interactions. Collectively, our findings define a Ca²⁺-stabilized, electrostatically driven mechanism for RVFV Gn recognition by LRP1, providing molecular insight into viral entry and a structural framework for the rational design of vaccines and antiviral therapeutics. Full article

Apart from some information on dengue virus (DENV), there is limited data on the circulation of arboviruses in Burkina Faso. The aim of this study was to investigate antibody prevalence against six arboviruses in four regions of the country to document previous virus exposure. Serum samples collected between August 2018 and December 2022 from people infected with viral hepatitis B and C in Bobo-Dioulasso were used to detect IgG antibodies against DENV, Chikungunya virus (CHIKV), Zika virus (ZIKV), Yellow fever virus (YFV), Rift Valley fever virus (RVFV) and Crimean-Congo hemorrhagic fever virus (CCHFV) using commercial ELISA kits. A total of 1808 serum samples, accompanied by basic epidemiologic data (sex, age and residency) were included in this study. We observed an IgG antibodies seroprevalence of 75.4% for DENV, 30.8% for CHIKV, 2.9% for ZIKV, 1.2% for RVFV, 1.1% for CCHFV and 1.1% for YFV. Age, sex, and place of residence were significantly associated with seropositivity for DENV and age and sex with CHIKV seropositivity. The results suggested widespread circulation of DENV and CHIKV and possible circulation of CCHFV and RVFV in humans in Burkina Faso. The importance of strengthening arbovirus surveillance by including additional arboviruses in the diagnostic panel is emphasized. Full article

Crimean-Congo hemorrhagic fever (CCHF) and Rift Valley fever (RVF) are major zoonotic diseases, spread by arthropods, with livestock serving as amplifying hosts. Despite Nigeria’s large ruminant population and robust cross-border animal trade, data on the seroprevalence of the viral agents causing these diseases remain limited. A longitudinal serological survey was conducted in five major livestock markets across Nigeria. A total of 3450 animals (cattle, sheep, and goats) were tested for Crimean-Congo hemorrhagic fever virus (CCHFV) and Rift Valley fever virus (RVFV) antibodies using ELISA. Data on species, age, sex, animal origin, and tick infestation were collected and analyzed. Overall seroprevalence was 27.1% (95% CI: 25.6–28.6) for CCHFV and 5.8% (95% CI: 5.1–6.7) for RVFV. Cattle showed the highest prevalence for both CCHFV (55.4%) and RVFV (11.2%), followed by sheep (17.4% and 2.9%) and goats (8.6% and 3.4%). Evidence of mixed exposure to both CCHFV and RVFV antibodies was detected in 8.2% of cattle, 0.7% of sheep, and 0.2% of goats. Seropositivity was higher in older animals, females, tick-infested animals, and those of Nigerian origin compared to imported animals. Market-level variation was observed, with Mubi livestock market showing the highest CCHFV prevalence (35.5%) and Illela livestock market the highest RVF prevalence (11.2%). The detection of con-current CCHFV and RVFV antibodies, alongside high CCHFV prevalence and detectable RVFV circulation among Nigerian livestock highlight the risk of zoonotic spillover, particularly in livestock markets with intense human–animal interaction. Full article

Sentinel animals may play a key role in the surveillance of arbovirus circulation, particularly in developing countries. This study aimed to assess the relevance of using dogs as sentinel animals for Rift Valley fever virus (RVFV) surveillance in Madagascar. Serological surveys were conducted on 513 dogs and 135 cattle in the Ifanadiana district, southeastern Madagascar. In addition, 486 human dry blood samples available from the same area were used. Antibodies against RVFV were detected in 23 of 513 dogs, in 86 of 486 humans, and in 33 of 135 cattle. Serocatalytic models fitted to age-stratified serological data were developed to estimate the RVFV force of infection (FOI) under several hypotheses, ranging from no relationship to proportional RVFV FOIs between humans, cattle, and dogs. The best supported model indicated that RVFV FOI in humans and cattle was proportional to RVFV FOI in dogs. Proportionality parameters were estimated at 2.6 (95% credible interval: [1.4–5.1]) for humans and 3.5 (95% credible interval: [1.3–6.4]) for cattle. Our findings suggested that dog blood samples could be used to identify RVFV circulation in RVF endemic areas and infer the exposure of humans and cattle in these areas in Madagascar. Full article