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The distribution of Rift Valley fever virus in the mosquito Culex pipiens as revealed by viral titration of dissected organs and tissues.

Distribution of Rift Valley fever virus (RVFV) was studied in the mosquito Culex pipiens. Mosquitoes were dissected on days 1-7 after an infectious bloodmeal, and RVFV plaque assays were performed on the legs, posterior midgut, ovaries, salivary glands, thoracic ganglia, and remaining organs and tissues (remnants). On days 7-12 and 14 following an infectious bloodmeal, mosquitoes were tested for their ability to transmit virus and then dissected. Dissemination (systemic infection) rates averaged 22% on days 1-14 and transmission rates 33% on days 7-14. There were no significant differences in …

Differentiation of a human monocytic cell line associated with increased production of Rift Valley fever virus by infected cells.

Rift Valley fever (RVF) virus is a cause of significant human and animal disease in many parts of Africa. In some cases, it causes a hemorrhagic fever, which is frequently fatal. Prior studies have shown that RVF virus productively infects peritoneal macrophages from susceptible rat strains. The U937 human monocytic cell line was used to determine the effect of monocytic cell differentiation on the degree of viral production by cell cultures infected with RVF virus. Differentiation of U937 cells to more mature monocytic cells by phorbol ester resulted in production of 10 times more infectious …

The pathology of Rift Valley fever. II. Lesions occurring in field cases in adult cattle, calves and aborted foetuses.

Since the original description of Rift Valley fever in sheep, cattle and man in the Rift Valley in Kenya in 1931, very little has been published on the disease in cattle. This report deals with the macroscopic and microscopic pathology of field cases of Rift Valley fever in 22 adult cattle, 8 calves and 8 aborted foetuses. The microscopic liver lesions in 13 adult cattle were characterized by marked centri- and midzonal eosinophilic necrosis, involving almost 2/3 of the lobules, and accompanied by sparsely distributed primary foci of necrosis. In 3 animals, however, the hepatic lesions were mo…

Experimental transmission and field isolation studies implicating Culex pipiens as a vector of Rift Valley fever virus in Egypt.

Attempts were made to isolate virus from wild caught mosquitoes during the 1977 and 1978 Rift Valley fever (RVF) epizootics in Egypt. Over 95% of the 55,126 mosquitoes collected from epizootic areas in the Nile Delta and Valley were Culex pipiens. Two strains of RVF virus were isolated from unengorged female C. pipiens taken in 1978. Laboratory-reared C. pipiens originating from a population sample from the Nile Delta epizootic area transmitted RVF virus. The infection rate of mosquitoes that fed on viremic hamsters was 86.7%; the transmission rate was 40.0% (46.2% based only on infected mosqu…

Investigation and response to rift valley fever outbreak in ruminant livestock from Ngoma District, eastern province of Rwanda, 2024.

BACKGROUND: Rift Valley fever (RVF) is a zoonotic mosquito-borne disease, causing high livestock morbidity and mortality, with potential human spillover. Rwanda has experienced repeated outbreaks, including significant ones in 2018 and 2022. In August 2024, a smaller localized outbreak was reported in Ngoma District, Eastern Province, providing insights into rapid detection, response, and recovery. METHODS: Following confirmation of the index case by RT-PCR, 4062 blood samples were collected through active community and slaughterhouse surveillance. Epidemiological and demographic data were an…

Efficient Identification of Monoclonal Antibodies Against Rift Valley Fever Virus Using High-Throughput Single Lymphocyte Transcriptomics of Immunized Mice.

Background: Rift Valley fever virus (RVFV) is a zoonotic virus that poses a significant threat to both livestock and human health and has caused outbreaks in endemic regions. In humans, most patients experience a febrile illness; however, in some patients, RVF disease may result in hemorrhagic fever, retinitis, or encephalitis. While several veterinary vaccines are being utilized in endemic countries, currently, there are no licensed RVF vaccines or therapeutics for human use. Neutralizing antibodies specifically targeting vulnerable pathogen epitopes are promising candidates for prophylactic …

Molecular detection of Ehrlichia ruminantium in ticks from ruminants during the 2021 Rift Valley fever outbreak in Mananjary, Madagascar.

Ehrlichia ruminantium, the causative agent of heartwater, is a tick-borne pathogen affecting livestock in Africa and the Caribbean. This disease is transmitted primarily by Amblyomma variegatum ticks and poses a significant threat to animal health. In Madagascar, the prevalence of E. ruminantium remains poorly documented. During a Rift Valley fever (RVF) outbreak in Mananjary, Madagascar (April-May 2021), we conducted a field study to assess the circulation of vector-borne pathogens in ticks collected from ruminants. Ticks were morphologically identified, and DNA was extracted for quantitative…

Seasonal variation in mosquito abundance and environmental predictors in semi-pastoral southern Kenya: implications for endemic Rift Valley fever.

BACKGROUND: Ecological variables that vary across time and space shape mosquito populations, creating microenvironments that can become disease transmission hotspots. Rift Valley fever virus (RVFV), a priority zoonotic arbovirus, thrives in diverse conditions and has been detected in over 50 mosquito species. This diversity complicates efforts to identify the key vectors involved in transmission and highlights the need to understand how environmental conditions shape mosquito abundance in high-risk landscapes. METHODS: This study investigated spatio-temporal variation in mosquito abundance ac…

Safety and Efficacy upon Infection in Sheep with Rift Valley Fever Virus ZH548-rA2, a Triple Mutant Rescued Virus.

The introduction of three single nucleotide mutations into the genome of the virulent RVFV ZH548 strain allows for the rescue of a fully attenuated virus in mice (ZH548-rA2). These mutations are located in the viral genes encoding the RdRp and the non-structural protein NSs. This paper shows the results obtained after the subcutaneous inoculation of ZH548-rA2 in adult sheep and the subsequent challenge with the parental virus (ZH548-rC1). Inoculation with the ZH548-rA2 virus caused no detectable clinical or pathological effect in sheep, whereas inoculation of the parental rC1 virus caused lesi

A Lipid Nanoparticle-Formulated Self-Amplifying RNA Rift Valley Fever Vaccine Induces a Robust Humoral Immune Response in Mice.

Rift Valley fever (RVF) is a mosquito-borne viral zoonosis that causes high fetal and neonatal mortality rates in ruminants and sometimes severe to fatal complications like encephalitis and hemorrhagic fever in humans. There is no licensed RVF vaccine for human use while approved livestock vaccines have suboptimal safety or efficacy. We designed self-amplifying RNA (saRNA) RVF vaccines and assessed their humoral immunogenicity in mice. Plasmid DNA encoding the Rift Valley fever virus (RVFV) medium (M) segment consensus sequence (WT consensus) and its derivatives mutated to enhance cell membran…

Development and Validation of Rapid Colorimetric Reverse Transcription Loop-Mediated Isothermal Amplification for Detection of Rift Valley Fever Virus.

Rift Valley fever virus (RVFV) is a high-priority zoonotic pathogen with the ability to cause massive loss during its outbreak within a very short period of time. Lack of a highly sensitive, instant reading diagnostic method for RVFV, which is more suitable for on-site testing, is a big gap that needs to be addressed. The aim of this study was to develop a novel one-step reverse transcription loop-mediated isothermal amplification (RT-LAMP) method for the rapid detection of RVFV. To achieve this, the selected RVFV M segment nucleotide sequences were aligned using Multiple Sequence Comparison b…

Using Multiplex Amplicon PCR Technology to Efficiently and Timely Generate Rift Valley Fever Virus Sequence Data for Genomic Surveillance.

Rift Valley fever (RVF) is a febrile vector-borne disease endemic in Africa and continues to spread in new territories. It is a climate-sensitive disease mostly triggered by abnormal rainfall patterns. The disease is associated with high mortality and morbidity in both humans and livestock. RVF is caused by the Rift Valley fever virus (RVFV) of the genus Phlebovirus in the family Phenuiviridae. It is a tripartite RNA virus with three genomic segments: small (S), medium (M) and large (L). Pathogen genomic sequencing is becoming a routine procedure and a powerful tool for understanding the evolu…

Bacterium-Like Particles Displaying the Rift Valley Fever Virus Gn Head Protein Induces Efficacious Immune Responses in Immunized Mice.

Rift Valley fever virus (RVFV), a mosquito-borne zoonotic phlebovirus, causes serious disease in humans and ruminants. According to the World Health Organization, Rift Valley fever is classified as a priority disease, and as such, vaccine development is of high priority due to the lack of licensed vaccines. In this study, a bacterium-like particle vaccine (BLP), RVFV-BLPs, is constructed. A novel display system is described, which is based on non-living and non-genetically modified Gram-positive bacterial cells, designated as Gram-positive enhancer matrix (GEM). The RVFV Gn head protein was di…

Lithium inhibits NF-κB nuclear translocation and modulate inflammation profiles in Rift valley fever virus-infected Raw 264.7 macrophages.

INTRODUCTION: Rift Valley fever virus (RVFV) is a zoonotic life-threatening viral infection endemic across sub-Saharan African countries and the Arabian Peninsula; however, there is a growing panic of its spread to non-endemic regions. This viral infection triggers a wide spectrum of symptoms that span from fibril illnesses to more severe symptoms such as haemorrhagic fever and encephalitis. These severe symptoms have been associated with dysregulated immune response propagated by the virulence factor, non-structural protein (NSs). Thus, this study investigates the effects of lithium on NF-κB …

Rift Valley fever knowledge, mitigation strategies and communication preferences among male and female livestock farmers in Eastern Province, Rwanda.

The Government of Rwanda reported an outbreak of Rift Valley fever (RVF) in the Eastern Province in 2018. To respond to the outbreak, vaccination and education campaigns about the disease were carried out. Because RVF cases continue to be detected in Rwanda and the disease impacts livelihoods and health, accurate knowledge and communication are imperative. The objectives of this study were to evaluate knowledge and risk perceptions of RVF transmission among livestock farmers in Nyagatare District, Eastern Province, Rwanda, and to compare RVF knowledge, risk perceptions, and farming practices b…

Detection of Rift Valley Fever Virus Lineage H From South Africa Through the Syndromic Sentinel Surveillance Network in Senegal.

BACKGROUND: Rift Valley fever virus (RVFV) is an arbovirus that causes epizootics and epidemics among livestock population and humans. Our surveillance system has revealed multiple emergences and re-emergences of RVFV in West Africa over the last decade. METHODS: The Sentinel Syndromic Surveillance Network in Senegal (4S) has been implemented since 2011. Samples from human suspected arbovirus infection in 4S sentinel sites were sent to Institut Pasteur de Dakar (IPD), where arbovirus diagnosis by enzyme-linked immunosorbent assay (ELISA), real-time reverse transcription polymerase chain react…

Selected wetland soil properties correlate to Rift Valley fever livestock mortalities reported in 2009-10 in central South Africa.

Outbreaks of Rift Valley fever have devastating impacts on ruminants, humans, as well as on regional and national economies. Although numerous studies on the impact and outbreak of Rift Valley fever exist, relatively little is known about the role of environmental factors, especially soil, on the aestivation of the virus. This study thus selected 22 sites for study in central South Africa, known to be the recurrent epicenter of widespread Rift Valley fever outbreaks in Southern Africa. Soils were described, sampled and analyzed in detail at each site. Of all the soil variables analyzed for, on…

Genetic dissection of Rift Valley fever pathogenesis: Rvfs2 locus on mouse chromosome 11 enables survival to early-onset hepatitis.

Infection of mice with Rift Valley fever virus (RVFV) reproduces major pathological features of severe human disease, notably the early-onset hepatitis and delayed-onset encephalitis. We previously reported that the Rvfs2 locus from the susceptible MBT/Pas strain reduces survival time after RVFV infection. Here, we used BALB/cByJ (BALB) mice congenic for Rvfs2 (C.MBT-Rvfs2) to investigate the pathophysiological mechanisms impacted by Rvfs2. Clinical, biochemical and histopathological features indicated similar liver damage in BALB and C.MBT-Rvfs2 mice until day 5 after infection. However, whil…

Recombinant Rift Valley fever viruses encoding bluetongue virus (BTV) antigens: Immunity and efficacy studies upon a BTV-4 challenge.

BACKGROUND: Many ruminant diseases of viral aetiology can be effectively prevented using appropriate vaccination measures. For diseases such as Rift Valley fever (RVF) the long inter-epizootic periods make routine vaccination programs unfeasible. Coupling RVF prophylaxis with seasonal vaccination programmes by means of multivalent vaccine platforms would help to reduce the risk of new RVF outbreaks. METHODOLOGY/PRINCIPAL FINDINGS: In this work we generated recombinant attenuated Rift Valley fever viruses (RVFVs) encoding in place of the virulence factor NSs either the VP2 capsid protein or a …

Межспециализированная сеть, играющая центральную роль, хостинг и развитие в раннем возрасте связаны с носителями вируса лихорадки Рифт-Вэлли.

Вирус лихорадки Рифт-Вэлли (RVFV) несет основное бремя болезней в скотоводческих общинах и сельскохозяйственном секторе на Африканском континенте и Аравийском полуострове. Энзоотическая, эпизоотическая и зоонотическая динамика передачи RVFV остается плохой, особенно из-за слабого понимания роли млекопитающих в эпидемиологической и инфекционной экологии этого арбовируса. С помощью фрагментарной модели структурного уравнения в этом исследовании была предпринята попытка выявить связи между биологическими и экологическими характеристиками видов млекопитающих и документально подтвержденной инфекцие

Совпадение в аннотации оригинала
Rift Valley fever virus (RVFV) is responsible for a substantive disease burden in pastoralist communities and the agricultural sector in the African continent and Arabian Peninsula. Enzootic, epizootic and zoonotic RVFV transmission dynamics remain ill-defined, particularly due to a poor understanding of the role of mammalian hosts in the epidemiology and in…