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Vector competence of Culex pipiens quinquefasciatus (Diptera: Culicidae) for West Nile virus isolates from Florida.

ABSTRACT: To assess vector competence (infection, dissemination and transmission) of Culex pipiens quinquefasciatus for Florida (FL) West Nile virus (WNV) isolates.West Nile virus isolates (WN-FL-03: NY99 genotype; WN-FL-05-558, WN-FL-05-2186, WN-FL-05-510: WN02 genotype) collected from different regions of FL were used for vector competence experiments in Cx. p. quinquefasciatus from Alachua County and Indian River County in FL. Mosquitoes from both colonies were fed blood containing 7.9 ± 0.2 log10 plaque-forming units WNV/ml ± SE and incubated at 28 °C for 14 days. Vector competence, including rates of infection, dissemination, and transmission, was compared between colonies for WN-FL-03 using chi-squared. Virus titres in bodies, legs and saliva were compared using anova. Daily measurements of in vitro replication of WNV isolates were evaluated in Vero cells so that a standardised virus dose for each isolate could be delivered to mosquitoes.Infection and dissemination rates were high (? 95%) and not affected by isolate or colony (infection, P = 0.679; dissemination, P = 0.799). Transmission rates were low (? 20%), detected in one colony and affected by isolate (P = 0.008). Body and leg titres differed between isolates (body titre, P = 0.031; leg titre, P = 0.044) and colonies (body titre, P = 0.001; leg titre, P = 0.013) while saliva titre did not differ between isolates (P = 0.462).Variation in vector competence of mosquito populations may be attributed, in part, to exposures to WNV with genetic differences leading to different rates of replication in mosquitoes. Evaluation of vector competence for different WNV isolates may help us understand vector-virus interactions and, hence, the role of vectors in complex virus transmission cycles in nature.

SUBMITTER: Richards SL

PROVIDER: S-EPMC4101994 | biostudies-literature | 2014 May

REPOSITORIES: biostudies-literature

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Vector competence of Culex pipiens quinquefasciatus (Diptera: Culicidae) for West Nile virus isolates from Florida.

Richards Stephanie L SL Anderson Sheri L SL Lord Cynthia C CC

Tropical medicine & international health : TM & IH 20140212 5

<h4>Objectives</h4>To assess vector competence (infection, dissemination and transmission) of Culex pipiens quinquefasciatus for Florida (FL) West Nile virus (WNV) isolates.<h4>Methods</h4>West Nile virus isolates (WN-FL-03: NY99 genotype; WN-FL-05-558, WN-FL-05-2186, WN-FL-05-510: WN02 genotype) collected from different regions of FL were used for vector competence experiments in Cx. p. quinquefasciatus from Alachua County and Indian River County in FL. Mosquitoes from both colonies were fed bl ...[more]

PMID: 24898274

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Project description:BACKGROUND: Culex spp. mosquitoes are considered to be the most important vectors of West Nile virus (WNV) detected in at least 34 species of mosquitoes in the United States. In North America, Culex pipiens pipiens, Culex pipiens quinquefasciatus, and Culex tarsalis are all competent vectors of WNV, which is considered to be enzootic in the United States and has also been detected in equines and birds in many states of Mexico and in humans in Nuevo Leon. There is potential for WNV to be introduced into Mexico City by various means including infected mosquitoes on airplanes, migrating birds, ground transportation and infected humans. Little is known of the geographic distribution of Culex pipiens complex mosquitoes and hybrids in Mexico City. Culex pipiens pipiens preferentially feed on avian hosts; Culex pipiens quinquefasciatus have historically been considered to prefer mammalian hosts; and hybrids of these two species could theoretically serve as bridge vectors to transmit WNV from avian hosts to humans and other mammalian hosts. In order to address the potential of WNV being introduced into Mexico City, we have determined the identity and spatial distribution of Culex pipiens complex mosquitoes and their hybrids. RESULTS: Mosquito larvae collected from 103 sites throughout Mexico City during 2004-2005 were identified as Culex, Culiseta or Ochlerotatus by morphological analysis. Within the genus Culex, specimens were further identified as Culex tarsalis or as belonging to the Culex pipiens complex. Members of the Culex pipiens complex were separated by measuring the ratio of the dorsal and ventral arms (DV/D ratio) of the male genitalia and also by using diagnostic primers designed for the Ace.2 gene. Culex pipiens quinquefasciatus was the most abundant form collected. CONCLUSIONS: Important WNV vectors species, Cx. p. pipiens, Cx. p. quinquefasciatus and Cx. tarsalis, are all present in Mexico City. Hybrids of Cx. p. pipiens and Cx. p. quinquefasciatus were also collected and identified. The presence and abundance of these WNV competent vectors is a cause for concern. Understanding the distribution of these vectors can help improve viral surveillance activities and mosquito control efforts in Mexico City.

Project description:BackgroundUnderstanding mechanisms that contribute to viral dissemination in mosquito vectors will contribute to our ability to interfere with the transmission of viral pathogens that impact public health. The expression of genes in two Culex pipiens quinquefasciatus populations from Florida with known differences in vector competence to West Nile virus (WNV) were compared using high throughput sequencing.ResultsA total of 15,176 transcripts were combined for comparison of expression differences between the two populations and 118 transcripts were differentially expressed (p < 0.05). The fold change in expression of the differentially expressed genes ranged from -7.5 - 6.13. The more competent population for WNV (Gainesville) over expressed 77 genes and down regulated 44 genes, compared with the less competent population for WNV (Vero Beach). Also, splicing analysis identified 3 transcripts with significantly different splice forms between the two populations. The functional analysis showed that the largest proportion of transcripts was included in the catalytic activity and transporter activity groups except for those in the unknown group. Interestingly, the up- regulated gene set contained most of the catalytic activity function and the down- regulated gene set had a notable proportion of transcripts with transporter activity function. Immune response category was shown in only the down regulated gene set, although those represent a relatively small portion of the function. Several different vitellogenin genes were expressed differentially. Based on the RNAseq data analysis, ovary development was compared across the populations and following WNV infection. There were significant differences among the compared groups.ConclusionsThis study suggests that ovary development is correlated to vector competence in two Culex populations in Florida. Both populations control energy allocations to reproduction as a response to WNV. This result provides novel insight into the defense mechanism used by Culex spp. mosquitoes against WNV.

Dataset Information

Vector competence of Culex pipiens quinquefasciatus (Diptera: Culicidae) for West Nile virus isolates from Florida.

Publications

Vector competence of Culex pipiens quinquefasciatus (Diptera: Culicidae) for West Nile virus isolates from Florida.

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