Isolation of West Nile and Sindbis Viruses from Mosquitoes Collected in the Nile Valley of Egypt During an Outbreak of Rift Valley Fever: Table 1

Abstract

As part of an evaluation of potential vectors of arboviruses during a Rift Valley fever (RVF) outbreak in the Nile Valley of Egypt in August 1993, we collected mosquitoes in villages with known RVF viral activity. Mosquitoes were sorted to species, pooled, and processed for virus isolation both by intracerebral inoculation into suckling mice and by inoculation into cell culture. A total of 33 virus isolates was made from 36,024 mosquitoes. Viruses were initially identified by indirect fluorescent antibody testing and consisted of 30 flaviviruses (all members of the Japanese encephalitis complex, most probably West Nile [WN] virus) and three alphaviruses (all members of western equine encephalitis complex, most probably Sindbis). The identity of selected viruses was confirmed by reverse transcriptase-polymerase chain reaction and sequencing. Culex antennatus (Becker) and Culex perexiguus Theobald accounted for five (17%) and 23 (77%) of the WN virus isolations, respectively. Despite isolation of viruses from 32 pools of mosquitoes (both WN and Sindbis viruses were isolated from a single pool), RVF virus was not isolated from these mosquitoes, even though most of them are known competent vectors collected during an ongoing RVF outbreak. Thus, it should be remembered, that even during a known arbovirus outbreak, other arboviruses may still be circulating and causing disease.

Multiple Virus Lineages Sharing Recent Common Ancestry Were Associated with a Large Rift Valley Fever Outbreak among Livestock in Kenya during 2006-2007

“…Our findings of RVF virus activity and population expansion without accompanying reports of human or livestock illness suggests that appropriate disease surveillance programs, coupled with the predictive power of NDVI, could identify areas with enhanced RVF virus activity risk and increase the likelihood of detecting otherwise cryptic RVF virus activity (7,57). Additionally, the early warning potential of NDVI analyses could allow for a window of opportunity for the prophylactic deployment of safe and effective RVF virus vaccines to target either areas at greatest risk or highly valuable livestock animals in areas in which the virus is endemic.…”

A Comprehensive Review of Common Bacterial, Parasitic and Viral Zoonoses at the Human-Animal Interface in Egypt

“…The virus was isolated from various species of domestic animals (e.g., sheep, cows, buffaloes, camels, goats, horses, and rats) as well as humans [ 288 , 289 ].The epizootics of RVF in Egypt were reported every year round. The effects of rainfall and river discharge in addition to optimal constellation of interconnected hydrologic, entomologic (high mosquitoes’ populations), and social conditions were incriminated in the spread of the virus [ 286 , 290 , 291 , 292 , 293 , 294 , 295 ]. Moreover, anti-RVFV antibodies were detected in pigs in 2008 [ 296 ], domestic and imported cattle and buffaloes in 2009 [ 87 ] and non-immunized dairy cattle from different localities in Egypt in 2013–2015 [ 297 ].…”

Virus isolations and high population density implicate Culex antennatus (Becker) (Diptera: Culicidae) as a vector of Rift Valley Fever virus during an outbreak in the Nile Delta of Egypt

“…Culex antennatus and three other species made up just 6% of the mosquitoes collected during that epidemic. During Egypt's 1993 RVF outbreak, screening of more than 36,000 Culicines trapped at the epicenter of infection, in Aswan governorate, failed to yield any RVFV isolates (Turell et al, 2002). Culex antennatus accounted for just 7.5% of these mosquitoes (Gad et al, 1999).…”