Laboratory demonstration of the vertical transmission of Rift Valley fever virus by Culex tarsalis mosquitoes

Bergren, Nicholas A.; Borland, Erin M.; Hartman, Daniel A.; Kading, Rebekah C.

doi:10.1371/journal.pntd.0009273

Cited by 19 publications

(20 citation statements)

References 43 publications

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“…Our results showed that, on average, RVF has the ability to remain endemic on the Comoros archipelago provided that the climate conditions remain favourable to support transmission. Within our framework, implicit persistence mechanisms can be ascribed to alternate wildlife hosts 36 , irregular introductions of infected hosts through trade 15 , or maintenance of the virus in local mosquito populations via transovarial transmission 37 , 38 . Serological surveys in potential wildlife hosts, imported animals and mosquito vectors would enable the routes for RVF persistence to be more precisely assessed.…”

Section: Discussionmentioning

confidence: 99%

Modelling the persistence and control of Rift Valley fever virus in a spatially heterogeneous landscape

et al. 2021

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The persistence mechanisms of Rift Valley fever (RVF), a zoonotic arboviral haemorrhagic fever, at both local and broader geographical scales have yet to be fully understood and rigorously quantified. We developed a mathematical metapopulation model describing RVF virus transmission in livestock across the four islands of the Comoros archipelago, accounting for island-specific environments and inter-island animal movements. By fitting our model in a Bayesian framework to 2004–2015 surveillance data, we estimated the importance of environmental drivers and animal movements on disease persistence, and tested the impact of different control scenarios on reducing disease burden throughout the archipelago. Here we report that (i) the archipelago network was able to sustain viral transmission in the absence of explicit disease introduction events after early 2007, (ii) repeated outbreaks during 2004–2020 may have gone under-detected by local surveillance, and (iii) co-ordinated within-island control measures are more effective than between-island animal movement restrictions.

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Section: Discussionmentioning

confidence: 99%

Modelling the persistence and control of Rift Valley fever virus in a spatially heterogeneous landscape

et al. 2021

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“…aegypti (Crabtree et al, 2012;Kading et al, 2014), 58 -95% for Cx. tarsalis (Bergren, Borland, Hartman, & Kading, 2021;Turell, Wilson, & Bennett, 2010) with midgut titers of over 6 log 10 PFU in actively infected Cx. tarsalis (Bergren et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

“…tarsalis (Bergren, Borland, Hartman, & Kading, 2021;Turell, Wilson, & Bennett, 2010) with midgut titers of over 6 log 10 PFU in actively infected Cx. tarsalis (Bergren et al, 2021). Similarly, up to 100% infection occurred MP-12 infected Cx.…”

Section: Discussionmentioning

confidence: 99%

Human vaccine candidate (DDVax) development against Rift Valley Fever: dissemination safety studies in mosquitoes

Campbell

Snell

Bennett

et al. 2021

Preprint

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Rift Valley fever virus (RVFV) is a mosquito-borne pathogen with significant human and veterinary health consequences that periodically emerges in epizootics. RVF causes fetal loss and death in ruminants and in humans can lead to liver and renal disease, delayed-onset encephalitis, retinitis, and in some cases severe hemorrhagic fever. A live attenuated vaccine candidate (DDVax), was developed by the deletion of the virulence factors NSs and NSm from a clinical isolate, ZH501, and has proven safe and immunogenic in rodents, pregnant sheep and non-human primates. Deletion of NSm also severely restricted mosquito midgut infection and inhibited vector-borne transmission. To demonstrate environmental safety, this study investigated the replication, dissemination and transmission efficiency of DDVax in mosquitoes following oral exposure compared to RVFV strains MP-12 and ZH501. Infection and dissemination profiles were also measured in mosquitoes 7 days after feeding on goats inoculated with DDvax or MP-12. Hypothesis: DDVax should infect mosquitoes at significantly lower rates than other RVF strains and, due to lack of NSm, be transmission incompetent. Exposure of Ae. aegypti and Cx. tarsalis to 6-8 log plaque forming units (PFU)/mL DDVax by artificial bloodmeal resulted in significantly reduced DDVax infection rates in mosquito bodies compared to controls. Plaque assays indicated negligible transmission of infectious DDVax in Cx. tarsalis saliva (1/140 sampled) and none in Ae aegypti saliva (0/120). Serum from goats inoculated with DDVax or MP-12 did not harbor detectable infectious virus by plaque assay at 1, 2, or 3 days-post-inoculation; infectious virus was, however, recovered from mosquito bodies that fed on goats vaccinated with MP-12 (13.8% and 4.6%, respectively), but strikingly, DDvax positive mosquito bodies were greatly reduced (4%, and 0%, respectively). Furthermore, DDVax did not disseminate to legs/wings in any of the goat-fed mosquitoes. Collectively, these results are consistent with a beneficial environmental safety profile .

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“…The discovery of vertical transmission within insect vector species other than floodwater Aedes spp. mosquitoes [164] indicates the existence of multiple pathways for local RVFV persistence in different ecosystems during time periods that are in between recognized outbreaks. An additional non-vector route of RVFV transmission to humans, i.e., maternal-fetal transmission, has also been identified recently [165][166][167], and it has been established that RVFV can be an abortifacient in humans [168].…”

Section: Evidence Of Vector Presence and Competence For Interepidemic Rvfvmentioning

confidence: 99%

Paving the way for human vaccination against Rift Valley fever virus: A systematic literature review of RVFV epidemiology from 1999 to 2021

Gerken

LaBeaud

Mandi

et al. 2021

Preprint

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Background: Rift Valley fever virus (RVFV) is a lethal threat to humans and livestock in many parts of Africa, Arabia, and the Indian Ocean. This systematic review’s objective was to consolidate understanding of RVFV epidemiology during 1999-2021 and highlight knowledge gaps relevant to plans for human vaccine trials. Methodology/Principal Findings: The review is registered with PROSPERO (CRD42020221622). Reports of RVFV infection or exposure among humans, animals, and/or vectors in Africa, the Arabian Peninsula, and the Indian Ocean during the period January 1999 to June 2021 were eligible for inclusion. Online databases were searched for publications, and supplemental materials were recovered from official reports and research colleagues. Exposures were classified into five groups: 1) acute human RVF cases, 2) acute animal cases, 3) human RVFV sero-surveys, 4) animal sero-surveys, and 5) insect infections. Human risk factors, circulating RVFV lineages, and surveillance methods were also tabulated. In meta-analysis of risks, summary odds ratios were computed using random-effects modeling. 1104 unique human or animal RVFV transmission events were reported in 39 countries during 1999-2021. Outbreaks among humans or animals occurred at rates of 5.8/year and 12.4/year, respectively, with Mauritania, Madagascar, Kenya, South Africa, and Sudan having the most human outbreak years. Men had greater odds of RVFV infection than women, and animal contact, butchering, milking, and handling aborted material were significantly associated with greater odds of exposure. Animal risk was linked to location, proximity to water, and exposure to other herds or wildlife. RVFV was detected in a variety of mosquito vectors during interepidemic periods, confirming ongoing transmission. Conclusions/Significance: With broad variability in surveillance, case finding, survey design, and RVFV case confirmation, combined with uncertainty about populations-at-risk, there were inconsistent results from location to location. However, it was evident that RVFV transmission is expanding its range and frequency. Gaps assessment indicated the need to harmonize human and animal surveillance and improve diagnostics and genotyping. Given the frequency of RVFV outbreaks, human vaccination has strong potential to mitigate the impact of this now widely endemic disease.

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Laboratory demonstration of the vertical transmission of Rift Valley fever virus by Culex tarsalis mosquitoes

Cited by 19 publications

References 43 publications

Modelling the persistence and control of Rift Valley fever virus in a spatially heterogeneous landscape

Modelling the persistence and control of Rift Valley fever virus in a spatially heterogeneous landscape

Human vaccine candidate (DDVax) development against Rift Valley Fever: dissemination safety studies in mosquitoes

Paving the way for human vaccination against Rift Valley fever virus: A systematic literature review of RVFV epidemiology from 1999 to 2021

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