High Transmission Potential of West Nile Virus Lineage 1 for Cx. pipiens s.l. of Iran

Abstract

Vector competence is an important parameter in evaluating whether a species plays a role in transmission of an arbovirus. Although the protocols are similar, interpretation of results is unique given the specific interactions that exist between a mosquito population and a viral genotype. Here, we assessed the infection (IR), dissemination (DR), and transmission (TR) rates of Cx. pipiens s.l., collected from Iran, for West Nile virus (WNV) lineage 1a. We showed that Cx. pipiens s.l. mosquitoes in Iran were susceptible to WNV with IR up to 89.7%, 93.6%, and 83.9% at 7, 14, and 21 days post-infection (dpi) respectively. In addition, DR and TR reached respectively 92.3% and 75.0% at 21 dpi, and the number of viral particles delivered with saliva reached up to 1.33 × 105 particles. Therefore, an unexpected high risk of WNV dissemination in the region where Cx. pipiens s.l. mosquitoes are well established should be considered carefully and surveillance measures implemented accordingly.

Vectorial Competence Potential of Culex Quinquefasciatus (Say, 1923) from the Amazon Region to Transmit West Nile Virus Isolated in Brazil

“…In our study, saliva samples from the 14th pi were not positive in any of the tests performed, being possible to identify and quantify the viral load only in the samples of 21rst pi, with titers ranging from 2x10 2 to 4x10 2 PFU/mL, values that are high when analyzing saliva in isolation, but when evaluating the saliva samples together with the head and body samples belonging to the same pi, a reduction in the viral load in the saliva is observed. These data are similar to those identi ed by Bakhshi et al [41] in research with Cx. pipiens, where it was observed that despite the presence of WNV in saliva after 21 days after infection, the viral titer is lower than that observed in body and head samples belonging to the same group.…”

“…It was observed that the studied population has high susceptibility to the WNV strain used, since the virus was identi ed in all body samples of 7th, 14th and 21rst pi, as well as it was possible to quantify the viral titer in the same samples in the same period, corroborating with data presented by Bakhshi et al [41] which demonstrates that Cx. pipiens species also showed high susceptibility to WNV strain belonging to 1a lineage isolated in Iran, with infection rates varying from 70% to 88% at 7th and 21rst pi.…”

“…quinquefasciatus samples orally infected with different WNV isolates, the high infection rate is not necessarily related to a similar increase in the transmission rate. Bakhshi et al [41] highlights that although the infection rates found in their study did not show statistical differences, the viral titer of the body samples also exhibited signi cant growth as the days post-infection increased.…”

“…quinquefasciatus body occurred in a similar way to our study, in which the viral dissemination rate at the 7th pi was 58%, followed by a decrease in this rate for only 36% at the 14th pi and for a new growth at the 21st pi (55%). In the study by Bakhshi et al [41] with Cx. pipiens, there was a dissemination rate of 92.3% on the 21st pi, but no statistical differences in the analysis of viral titles.…”

Pathogenicity and virulence of West Nile virus revisited eight decades after its first isolation

“…Clade 1a is globally spread, clade 1b, or Kunjin virus (KUNV), mainly circulates in Australia, and clade 1c (now reassigned to Lin 5) has only been described in India [ 34 ]. Lin 2 has been reported in Africa, Europe, and the Middle East [ 35 ]. Lin 3, or Rabensburg virus, Lin 4, and a putative Lin 6 (closely related to Lin 4) were described in Czech Republic, Russia, and Spain, respectively [ 33 ].…”