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Environmental stochasticity and intraspecific competition influence the population dynamics of Culex quinquefasciatus (Diptera: Culicidae).

ABSTRACT: BACKGROUND:Members of the Culex pipiens complex (Cx. pipiens quinquefasciatus in Southern USA) play a critical role in the spillover of urban arboviruses such as West Nile virus or St. Louis encephalitis virus. Field studies have shown strong correlation between the periodicity of rainfall events and larval proliferation. However, mechanistic determinants driving this relationship are poorly understood. We hypothesize that rainfall events decrease strain from intraspecific competition through the associated reduction of immature density and the introduction of detritus. RESULTS:To address our hypothesis, we used laboratory competition experiments to inform a deterministic matrix projection model consisting of an age-structured larval matrix coupled with a stage-structured adult mosquito matrix. Rain events were simulated in a competition-based metabolic age model and compared to a null model including environmental variability. Variable rain delays in two-event simulations showed optimal proliferation occurring with rain delays between 16 and 21 days when including density-dependent effects. CONCLUSIONS:These results are comparable to the pattern observed in natural populations, indicating that Cx. quinquefasciatus proliferation rates can be modeled mechanistically as a density-dependent system. The empirical understanding of density-dependence as it relates to environmental stochasticity provides a theoretical platform for the study of larval dynamics and the impact of larval control in this medically relevant disease vector.

SUBMITTER: Koval WT

PROVIDER: S-EPMC5828118 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Environmental stochasticity and intraspecific competition influence the population dynamics of Culex quinquefasciatus (Diptera: Culicidae).

Koval William T WT Vazquez-Prokopec Gonzalo M GM

Parasites & vectors 20180227 1

<h4>Background</h4>Members of the Culex pipiens complex (Cx. pipiens quinquefasciatus in Southern USA) play a critical role in the spillover of urban arboviruses such as West Nile virus or St. Louis encephalitis virus. Field studies have shown strong correlation between the periodicity of rainfall events and larval proliferation. However, mechanistic determinants driving this relationship are poorly understood. We hypothesize that rainfall events decrease strain from intraspecific competition th ...[more]

PMID: 29482608

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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:BackgroundWater quality is known to influence the development and survival of larval mosquitoes, which affects mosquito-borne pathogen transmission as a function of the number of mosquitoes that reach adulthood and blood feed. Although water properties are known to affect mosquito development, few studies have investigated the link among soil properties, water quality, and mosquito development. Given the large number of ground-breeding mosquito species, this linkage is a potentially important factor to consider in mosquito ecology. In this study, we explored the effects of different soils on multiple life history parameters of the ground-breeding mosquito species Culex quinquefasciatus (Diptera: Culicidae).MethodsCx. quinquefasciatus larvae were reared in water combined with different soil substrates (sandy, silt, or clay loam textures) at increasing soil to water volume ratios, with and without the addition of organic matter (fish food). Gravid mosquitoes were offered different soil-water extracts to investigate soil effects on oviposition preference.ResultsWithout the addition of organic matter, larval survival and development differed significantly among waters with different soil textures and volumes of substrate. Mosquitoes in water with clay loam soil survived longer and developed further than mosquitoes in other soil waters. Larvae survived for longer periods of time with increased volumes of soil substrate. Adding organic matter reduced the differences in larval survival time, development, and pupation among soil-water extracts. Adult female mosquitoes oviposited more frequently in water with clay loam soil, but the addition of organic matter reduced the soil effects on oviposition preference.ConclusionsThis study suggests soil composition affects larval mosquito survival and development, as well as the oviposition preference of gravid females. Future studies could differentiate abiotic and biotic soil features that affect mosquitoes and incorporate soil variation at the landscape scale into models to predict mosquito population dynamics and mosquito-borne pathogen transmission.

Project description:This study examined pyrethroid resistance intensity and mechanisms in Culex quinquefasciatus (Say) (Diptera: Culicidae) populations from Jigawa, North-West Nigeria. Resistance statuses to permethrin, lambda-cyhalothrin and alphacypermethrin were determined with both WHO and CDC resistance bioassays. Synergist assay was conducted by pre-exposing the populations to Piperonyl butoxide (PBO) using the WHO method. Resistance intensities to 2x, 5x and 10x of diagnostic concentrations were determined with the CDC bottle method. Species analysis and presence of knockdown mutation (Leu-Phe) were done using Polymerase Chain Reaction (PCR). Results showed that Cx. quinquefasciatus was the only Culex spp. present and "Kdr-west" mutation was not detected in all analyzed samples. Using WHO method, Cx. quinquefasciatus resistance to permethrin was detected in Dutse (12.2%) and Kafin-Hausa (77.78%). Lambda-cyhalothrin resistance was recorded only in Kafin-Hausa (83.95%) with resistance suspected in Ringim (90%). Resistance to alphacypermethrin was recorded in all locations. Pre-exposure to PBO led to 100% mortality to alphacypermethrin and lambda-cyhalothrin in Ringim while mortality to permethrin and alphacypermethrin in Dutse increased from 12.2% to 97.5% and 64.37% to 79.52% respectively. Using CDC bottle bioassay, resistance was also recorded in all populations and the result shows a significant positive correlation (R2 = 0.728, p = 0.026) with the result from the WHO bioassay. Results of resistance intensity revealed a very high level of resistance in Kafin-Hausa with susceptibility to lambda-cyhalothrin and alphacypermethrin not achieved at 10x of diagnostic doses. Resistance intensity was also high in Dutse with susceptibility to all insecticides not achieved at 5x of diagnostic doses. Widespread and high intensity of resistance in Cx. quinquefasciatus from North-West Nigeria is a major threat to the control of diseases transmitted by Culex and other mosquito species. It is a challenge that needs to be adequately addressed so as to prevent the failure of pyrethroid-based vector control tools.

Dataset Information

Environmental stochasticity and intraspecific competition influence the population dynamics of Culex quinquefasciatus (Diptera: Culicidae).

Publications

Environmental stochasticity and intraspecific competition influence the population dynamics of Culex quinquefasciatus (Diptera: Culicidae).

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