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1.
Biomedica. 2015 Dec;35(4):572-581.

Aedes aegypti anti-salivary gland antibody concentration and dengue virus exposure history in healthy individuals living in an endemic area in Colombia.

Author information

  • 1Grupo de Investigaciones en Enfermedades Parasitarias e Infecciosas, Universidad de Pamplona, Norte de Santander, Colombia.
  • 2Hospital Local Los Patios, Norte de Santander, Colombia.
  • 3Pathobiological Sciences, Vector-borne Disease Laboratories, School of Veterinary Medicine, Louisiana State University.
  • 4School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA, USA.
  • 5Department of Pathology, Microbiology and Immunology, University of South Carolina, Columbia, SC, USA.

Abstract

INTRODUCTION:

Mosquito salivary proteins are able to induce an antibody response that reflects the level of human-vector contact. IgG antibodies against dengue virus (DENV-IgG) are indicators of previous exposure. The risk of DENV transmission is not only associated to mosquito or dengue factors, but also to socioeconomic factors that may play an important role in the disease epidemiology.

OBJECTIVE:

To determine the effect of the presence of Aedes aegypti mosquitos in different stages in households and the history of dengue exposure on vector-human contact determined by the level of anti-salivary protein antibodies in people living in a Colombian endemic area.

MATERIALS AND METHODS:

A pilot study of 58 households and 55 human subjects was conducted in Norte de Santander, Colombia. A questionnaire for socioeconomic factors was administered and houses were examined for the presence of Ae. aegypti specimens in the aquatic stages. The level of DENV-IgG antibodies (DENV-IgG), in addition to IgG and IgM anti- Ae. aegypti salivary gland extract (SGE) antibodies (SGE-IgG, SGE-IgM) were evaluated by ELISA using blood collected in filter paper.

RESULTS:

We found a significant higher level of SGE-IgG antibodies in subjects living in houses with Ae. aegypti in aquatic stages. We also found a higher concentration of SGE-IgG antibodies in people exposed to DENV, a positive correlation between IgM-SGE and IgG-DENV and a negative correlation with IgG-SGE.

CONCLUSION:

Anti-salivary proteins antibodies are consistent with the presence of Ae. aegypti aquatic stages inside houses and DENV-IgG antibodies concentrations.

PMID:
26844447
[PubMed - as supplied by publisher]
2.
Parasit Vectors. 2015 Oct 13;8:533. doi: 10.1186/s13071-015-1160-3.

An. gambiae gSG6-P1 evaluation as a proxy for human-vector contact in the Americas: a pilot study.

Author information

  • 1Department of Pathology, Microbiology and Immunology, University of South Carolina, Columbia, SC, USA. blondono@uscmed.sc.edu.
  • 2Department of Pathology, Microbiology and Immunology, University of South Carolina School of Medicine, 6439 Garners Ferry Rd, Bldg 2 Rm C3, Columbia, SC, 29209, USA. blondono@uscmed.sc.edu.
  • 3Laboratory of Parasitic Diseases, National Institutes of Health, NIAID, Bethesda, MD, USA. dramepm@niaid.nih.gov.
  • 4Laboratorio Clínico/Programa Medicina del Viajero, Clínica Alemana, Universidad del Desarrollo, Santiago, Chile. thomas.weitzel@gmail.com.
  • 5Hospital Militar, Santiago, Chile. reinaldo.rosas@gmail.com.
  • 6Department of Tropical Medicine, Tulane University, New Orleans, LA, USA. cgrippin@tulane.edu.
  • 7Hospital Los Patios, Los Patios, Norte de Santander, Colombia. carocardenasg@hotmail.com.
  • 8Hospital Emiro Quintero Canizales, Ocana, Norte de Santander, Colombia. marcealvareza@gmail.com.
  • 9Department of Tropical Medicine, Tulane University, New Orleans, LA, USA. wesson@tulane.edu.
  • 10Institut de Recherche pour le Développement-IRD, Bouaké, Côte d'Ivoire. anne.poinsignon@ird.fr.
  • 11Institut de Recherche pour le Développement-IRD, Bouaké, Côte d'Ivoire. franck.remoue@ird.fr.
  • 12Department of Pathology, Microbiology and Immunology, University of South Carolina, Columbia, SC, USA. Tonya.Colpitts@uscmed.sc.edu.

Abstract

BACKGROUND:

During blood meal, the female mosquito injects saliva able to elicit an immune response in the vertebrate. This immune response has been proven to reflect the intensity of exposure to mosquito bites and risk of infection for vector transmitted pathogens such as malaria. The peptide gSG6-P1 of An. gambiae saliva has been demonstrated to be antigenic and highly specific to Anopheles as a genus. However, the applicability of gSG6-P1 to measure exposure to different Anopheles species endemic in the Americas has yet to be evaluated. The purpose of this pilot study was to test whether human participants living in American countries present antibodies able to recognize the gSG6-P1, and whether these antibodies are useful as a proxy for mosquito bite exposure and malaria risk.

METHODS:

We tested human serum samples from Colombia, Chile, and the United States for the presence of IgG antibodies against gSG6-P1 by ELISA. Antibody concentrations were expressed as delta optical density (ΔOD) of each sera tested in duplicates. The difference in the antibody concentrations between groups was tested using the nonparametric Mann Whitney test (independent groups) and the nonparametric Wilcoxon matched-pairs signed rank test (dependent groups). All differences were considered significant with a P < 0.05.

RESULTS:

We found that the concentration of gSG6-P1 antibodies was significantly correlated with malaria infection status and mosquito bite exposure history. People with clinical malaria presented significantly higher concentrations of IgG anti-gSG6-P1 antibodies than healthy controls. Additionally, a significant raise in antibody concentrations was observed in subjects returning from malaria endemic areas.

CONCLUSION:

Our data shows that gSG6-P1 is a suitable candidate for the evaluation of exposure to Anopheles mosquito bites, risk of malaria transmission, and effectiveness of protection measures against mosquito bites in the Americas.

PMID:
26464073
[PubMed - in process]
PMCID:
PMC4605097
Free PMC Article
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3.
Parasit Vectors. 2015 Sep 23;8:486. doi: 10.1186/s13071-015-1068-y.

Oviposition responses of Aedes mosquitoes to bacterial isolates from attractive bamboo infusions.

Author information

  • 1Department of Entomology and W. M. Keck Center for Behavioral Biology, North Carolina State University, Campus Box 7613, Raleigh, NC, 27695-7613, USA. loganathan_ponnusamy@ncsu.edu.
  • 2Department of Entomology and W. M. Keck Center for Behavioral Biology, North Carolina State University, Campus Box 7613, Raleigh, NC, 27695-7613, USA. coby@ncsu.edu.
  • 3Department of Tropical Medicine, Tulane Health Sciences Center, Tulane University, New Orleans, LA, 70112, USA. wesson@tulane.edu.
  • 4Department of Statistics, North Carolina State University, Raleigh, NC, 27695, USA. carella@ncsu.edu.
  • 5Department of Entomology and W. M. Keck Center for Behavioral Biology, North Carolina State University, Campus Box 7613, Raleigh, NC, 27695-7613, USA. apperson@ncsu.edu.

Abstract

BACKGROUND:

The mosquitoes Aedes aegypti and Aedes albopictus are vectors of pathogenic viruses that cause major human illnesses including dengue, yellow fever and chikungunya. Both mosquito species are expanding their geographic distributions and now occur worldwide in temperate and tropical climates. Collection of eggs in oviposition traps (ovitraps) is commonly used for monitoring and surveillance of container-inhabiting Aedes populations by public health agencies charged with managing mosquito-transmitted illness. Addition of an organic infusion in these traps increases the number of eggs deposited. Gravid females are guided to ovitraps by volatile chemicals produced from the breakdown of organic matter by microbes.

METHODS:

We previously isolated and cultured 14 species of bacteria from attractive experimental infusions, made from the senescent leaves of canebrake bamboo (Arundinaria gigantea). Cultures were grown for 24 h at 28 °C with constant shaking (120 rpm) and cell densities were determined with a hemocytometer. Behavioral responses to single bacterial isolates and to a mix of isolates at different cell densities were evaluated using two-choice sticky-screen bioassay methods with gravid Ae. aegypti and Ae. albopictus.

RESULTS:

In behavioral assays of a mix of 14 bacterial isolates, significantly greater attraction responses were exhibited by Ae. aegypti and Ae. albopictus to bacterial densities of 10(7) and 10(8) cells/mL than to the control medium. When we tested single bacterial isolates, seven isolates (B1, B2, B3, B5, B12, B13 and B14) were significantly attractive to Ae. aegypti, and six isolates (B1, B5, B7, B10, B13 and B14) significantly attracted Ae. albopictus. Among all the isolates tested at three different cell densities, bacterial isolates B1, B5, B13 and B14 were highly attractive to both Aedes species.

CONCLUSIONS:

Our results show that at specific cell densities, some bacteria significantly influence the attraction of gravid Ae. aegypti and Ae. albopictus females to potential oviposition sites. Attractive bacterial isolates, when formulated for sustained release of attractants, could be coupled with an ovitrap containing a toxicant to achieve area-wide management of Aedes mosquitoes.

PMID:
26399712
[PubMed - in process]
PMCID:
PMC4581471
Free PMC Article
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4.
J Med Entomol. 2015 Jul;52(4):726-9. doi: 10.1093/jme/tjv048. Epub 2015 May 7.

Evidence for Aedes aegypti (Diptera: Culicidae) Oviposition on Boats in the Peruvian Amazon.

Author information

  • 1Department of Environmental Sciences, Emory University, Atlanta, GA 30322. sguagli@emory.edu.
  • 2Department of Entomology and Nematology, University of California, Davis, CA 95616.
  • 3La Escuela de Postgrado, Universidad Nacional de la Amazonía Peruana, Iquitos, Peru.
  • 4Department of Tropical Medicine, Tulane University, New Orleans, LA 70112.
  • 5Department of Entomology, North Carolina State University, Raleigh, NC 27695.
  • 6Department of Virology and Emerging Infections, U. S. Naval Medical Research Unit No.6 (NAMRU-6) Iquitos Laboratory, Iquitos, Peru.
  • 7Department of Environmental Sciences, Emory University, Atlanta, GA 30322.

Abstract

Dengue vector Aedes aegypti L. is invading peri-urban and rural areas throughout Latin America. Our previous research in the Peruvian Amazon has shown that river boats are heavily infested with immature and adult Ae. aegypti mosquitoes, likely playing a major role in their long-distance dispersal and successful invasion. However, the presence of immature mosquitoes provides no information about the timing of oviposition, and whether it took place in the boats. Here, we used baited ovitraps deployed on river boats to test the hypothesis that Ae. aegypti oviposition occurs during boat travel. We deployed 360 ovitraps on 60 different barges during August and October of 2013, and February 2014 (with 20 barges sampled during each month). We found that Ae. aegypti mosquitoes in 22 individual ovitraps from 15 of the 60 barges (premise index 25%) across all sampling dates. Further, the distribution of Ae. aegypti egg abundance was highly aggregated: 2.6% of traps (N=7) were responsible for 71.8% of eggs found, and 1.5% of traps (N=4) were responsible for all (100%) of the larvae found. Similarly, 5% of boats were responsible for the 71.47% of eggs. Our results provide strong evidence that Ae. aegypti oviposition commonly occurs during boat travel. Baited ovitraps could represent a cost-effective means of monitoring and controlling mosquito populations on boats.

© The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

KEYWORDS:

Aedes aegypti; boat; oviposition; ovitrap

PMID:
26335482
[PubMed - indexed for MEDLINE]
PMCID:
PMC4592347
[Available on 2016-07-01]
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5.
Am J Trop Med Hyg. 2015 Oct;93(4):869-74. doi: 10.4269/ajtmh.15-0130. Epub 2015 Jul 20.

Long-Lasting Permethrin-Impregnated Clothing Protects Against Mosquito Bites in Outdoor Workers.

Author information

  • 1Department of Pathology, Immunology and Microbiology, University of South Carolina, Columbia, South Carolina; Department of Tropical Medicine, Tulane University, New Orleans, Louisiana; Department of Epidemiology, Gillings School of Global Public Health, Chapel Hill, North Carolina; Department of Entomology, North Carolina State University, Raleigh, North Carolina; Department of Pathobiological Sciences, Louisiana State University, Baton Rouge, Louisiana berlinlondo@yahoo.com.
  • 2Department of Pathology, Immunology and Microbiology, University of South Carolina, Columbia, South Carolina; Department of Tropical Medicine, Tulane University, New Orleans, Louisiana; Department of Epidemiology, Gillings School of Global Public Health, Chapel Hill, North Carolina; Department of Entomology, North Carolina State University, Raleigh, North Carolina; Department of Pathobiological Sciences, Louisiana State University, Baton Rouge, Louisiana.

Abstract

Outdoor exposure to mosquitoes is a risk factor for many diseases, including malaria and dengue. We have previously shown that long-lasting permethrin-impregnated clothing protects against tick and chigger bites in a double-blind randomized controlled trial in North Carolina outdoor workers. Here, we evaluated whether this clothing is protective against mosquito bites by measuring changes in antibody titers to mosquito salivary gland extracts. On average, there was a 10-fold increase in titer during the spring and summer when mosquito exposure was likely to be the highest. During the first year of the study, the increase in titer in subjects wearing treated uniforms was 2- to 2.5-fold lower than that of control subjects. This finding suggests that long-lasting permethrin-impregnated clothing provided protection against mosquito bites.

© The American Society of Tropical Medicine and Hygiene.

PMID:
26195460
[PubMed - indexed for MEDLINE]
PMCID:
PMC4596613
[Available on 2016-10-07]
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6.
Parasit Vectors. 2015 Feb 24;8:123. doi: 10.1186/s13071-015-0730-8.

Genotype diversity of Trypanosoma cruzi in small rodents and Triatoma sanguisuga from a rural area in New Orleans, Louisiana.

Author information

  • 1Department of Tropical Medicine, Vector-Borne Infectious Disease Research Center, School of Public Health and Tropical Medicine, Tulane University, 1440 Canal Street, Rm. 1824, New Orleans, LA, 70112, USA. cherrera@tulane.edu.
  • 2Department of Tropical Medicine, Vector-Borne Infectious Disease Research Center, School of Public Health and Tropical Medicine, Tulane University, 1440 Canal Street, Rm. 1824, New Orleans, LA, 70112, USA. mlicon@tulane.edu.
  • 3Department of Tropical Medicine, Vector-Borne Infectious Disease Research Center, School of Public Health and Tropical Medicine, Tulane University, 1440 Canal Street, Rm. 1824, New Orleans, LA, 70112, USA. cnation@tulane.edu.
  • 4Department of Tropical Medicine, Vector-Borne Infectious Disease Research Center, School of Public Health and Tropical Medicine, Tulane University, 1440 Canal Street, Rm. 1824, New Orleans, LA, 70112, USA. sbishop@tulane.edu.
  • 5Department of Tropical Medicine, Vector-Borne Infectious Disease Research Center, School of Public Health and Tropical Medicine, Tulane University, 1440 Canal Street, Rm. 1824, New Orleans, LA, 70112, USA. wesson@tulane.edu.

Abstract

BACKGROUND:

Chagas disease is an anthropozoonosis caused by the protozoan parasite Trypanosoma cruzi that represents a major public health problem in Latin America. Although the United States is defined as non-endemic for Chagas disease due to the rarity of human cases, the presence of T. cruzi has now been amply demonstrated as enzootic in different regions of the south of the country from Georgia to California. In southeastern Louisiana, a high T. cruzi infection rate has been demonstrated in Triatoma sanguisuga, the local vector in this area. However, little is known about the role of small mammals in the wild and peridomestic transmission cycles.

METHODS:

This study focused on the molecular identification and genotyping of T. cruzi in both small rodents and T. sanguisuga from a rural area of New Orleans, Louisiana. DNA extractions were prepared from rodent heart, liver, spleen and skeletal muscle tissues and from cultures established from vector feces. T. cruzi infection was determined by standard PCR using primers specific for the minicircle variable region of the kinetoplastid DNA (kDNA) and the highly repetitive genomic satellite DNA (satDNA). Genotyping of discrete typing units (DTUs) was performed by amplification of mini-exon and 18S and 24Sα rRNA genes and subsequent sequence analysis.

RESULTS:

The DTUs TcI, TcIV and, for the first time, TcII, were identified in tissues of mice and rats naturally infected with T. cruzi captured in an area of New Orleans, close to the house where the first human case of Chagas disease was reported in Louisiana. The T. cruzi infection rate in 59 captured rodents was 76%. The frequencies of the detected DTUs in such mammals were TcI 82%, TcII 22% and TcIV 9%; 13% of all infections contained more than one DTU.

CONCLUSIONS:

Our results indicate a probable presence of a considerably greater diversity in T. cruzi DTUs circulating in the southeastern United States than previously reported. Understanding T. cruzi transmission dynamics in sylvatic and peridomestic cycles in mammals and insect vectors will be crucial to estimating the risk of local, vector-borne transmission of T. cruzi to humans in the United States.

PMID:
25890064
[PubMed - in process]
PMCID:
PMC4344744
Free PMC Article
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7.
Am J Trop Med Hyg. 2015 Jul;93(1):189-93. doi: 10.4269/ajtmh.14-0718. Epub 2015 Apr 13.

Evidence of limited polyandry in a natural population of Aedes aegypti.

Author information

  • 1Department of Ecology and Evolution, Yale University, New Haven, Connecticut; School of Public Health and Tropical Medicine, Tulane University, New Orleans, Louisiana joshua.richardson@yale.edu.
  • 2Department of Ecology and Evolution, Yale University, New Haven, Connecticut; School of Public Health and Tropical Medicine, Tulane University, New Orleans, Louisiana.

Abstract

The mosquito Aedes aegypti is a vector of yellow fever, dengue, and chikungunya. Control of the insect is crucial to stop the spread of dengue and chikungunya, so it is critically important to understand its mating behavior. Primarily, based on laboratory behavior, it has long been assumed that Ae. aegypti females mate once in their lifetime. However, multiple inseminations have been observed in semi-field and laboratory settings, and in closely related species. Here, we report the first evidence of polyandry in a natural population of Ae. aegypti. Female Ae. aegypti were captured around the New Orleans, LA, metropolitan area. They were offered a blood meal and allowed to lay eggs, which were reared to the third-instar larval stage. A parentage analysis using four microsatellite loci was performed. Out of 48 families, 3 showed evidence of multiple paternity. An expanded analysis of these three families found that one family group included offspring contributed by three fathers, and the other two included offspring from two fathers. This result establishes that polyandry can occur in a small proportion of Ae. aegypti females in a natural setting. This could complicate future genetic control efforts and has implications for sampling for population genetics.

© The American Society of Tropical Medicine and Hygiene.

PMID:
25870424
[PubMed - indexed for MEDLINE]
PMCID:
PMC4497895
[Available on 2016-07-08]
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8.
J Biol Dyn. 2015;9:52-72. doi: 10.1080/17513758.2015.1005698.

A network-patch methodology for adapting agent-based models for directly transmitted disease to mosquito-borne disease.

Author information

  • 1a Center for Computational Science , Department of Mathematics , Tulane University , New Orleans , LA   70118 , USA.

Abstract

Mosquito-borne diseases cause significant public health burden and are widely re-emerging or emerging. Understanding, predicting, and mitigating the spread of mosquito-borne disease in diverse populations and geographies are ongoing modelling challenges. We propose a hybrid network-patch model for the spread of mosquito-borne pathogens that accounts for individual movement through mosquito habitats, extending the capabilities of existing agent-based models (ABMs) to include vector-borne diseases. The ABM are coupled with differential equations representing 'clouds' of mosquitoes in patches accounting for mosquito ecology. We adapted an ABM for humans using this method and investigated the importance of heterogeneity in pathogen spread, motivating the utility of models of individual behaviour. We observed that the final epidemic size is greater in patch models with a high risk patch frequently visited than in a homogeneous model. Our hybrid model quantifies the importance of the heterogeneity in the spread of mosquito-borne pathogens, guiding mitigation strategies.

KEYWORDS:

37C10; 92D30; 92D40; chikungunya; dengue; differential equationsmodel; individual-based model; mosquito-borne disease; network; patch

PMID:
25648061
[PubMed - indexed for MEDLINE]
9.
J Med Entomol. 2014 Sep;51(5):1043-50.

Factors associated with peridomestic Triatoma sanguisuga (Hemiptera: Reduviidae) presence in southeastern Louisiana.

Abstract

Although rare, there have been isolated reports of autochthonous transmission of Trypanosoma cruzi Chagas in the United States. In June 2006, a human case of domestically transmitted T. cruzi was identified in southern Louisiana. To examine the localized risk of human T. cruzi infection in the area surrounding the initial human case, environmental surveys of households in the area and a serological survey of the residents were performed between September 2008 and November 2009. Human T. cruzi infection was determined using a rapid antigen field test, followed by confirmatory enzyme-linked immunosorbent assay testing in the laboratory. A perimeter search of each participating residence for Triatoma sanguisuga (LeConte), the predominant local triatomine species, was also performed. No participating individuals were positive for antibodies against T. cruzi; however, high levels of T. cruzi infection (62.4%) were detected in collected T. sanguisuga. Households with T. sanguisuga presence were less likely to use air conditioning, and more likely to have either chickens or cats on the property. While the human risk for T cruzi infection in southeastern Louisiana is low, a high prevalence of infected T. sanguisuga does indicate a substantial latent risk for T. cruzi peridomestic transmission. Further examination of the behavior and ecology of T. sanguisuga in the region will assist in refining local T. cruzi risk associations.

PMID:
25276935
[PubMed - indexed for MEDLINE]
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10.
Birth Defects Res A Clin Mol Teratol. 2014 Oct;100(10):792-6. doi: 10.1002/bdra.23297. Epub 2014 Sep 5.

Developmental outcomes in young children born to mothers with West Nile illness during pregnancy.

Author information

  • 1Tulane University, New Orleans, Louisiana.

Abstract

BACKGROUND:

West Nile virus (WNV) infection is associated with acute morbidity and mortality in adults and children. Information on the effects of maternal WNV illness during pregnancy on early childhood development is limited. This study was designed to examine the relationship between maternal WNV illness during pregnancy and birth and developmental outcomes at age 3 years.

METHODS:

Mother-child participants were identified using a national surveillance registry for women with WNV illness during pregnancy. Maternal and infant health data and relevant family characteristics were obtained through medical record reviews and maternal questionnaires. All infants received ophthalmologic examinations. Child development was evaluated at age 3 years using the Bayley Scales of Infant and Toddler Development-Third Edition (Bayley-III).

RESULTS:

As a group, the children's (N = 11) birth weight, head circumference, and infant ophthalmologic examination results were within age expectations; one child was born preterm (gestational age 36 weeks). Mean (SD) age at the time of Bayley-III testing was 36.7 (3.8) months. The group's mean performance on the Bayley-III was at or above age level in all domains, but one child showed a mild delay in the Adaptive domain. The variability observed in this sample (1/53 [1.9%] Domain scores < -2.0 SDs) was consistent with expectations based upon the distribution of Bayley-III Domain scores in the general population.

CONCLUSION:

Maternal WNV infection does not appear to be associated with global developmental delays in young children. These results are preliminary, however, and require confirmation in future research.

© 2014 Wiley Periodicals, Inc.

KEYWORDS:

West Nile virus; early childhood development; infancy; pregnancy

PMID:
25196266
[PubMed - indexed for MEDLINE]
PMCID:
PMC4573576
Free PMC Article
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11.
PLoS Curr. 2014 May 30;6. pii: ecurrents.outbreaks.f0b3978230599a56830ce30cb9ce0500. doi: 10.1371/currents.outbreaks.f0b3978230599a56830ce30cb9ce0500.

Towards an early warning system for forecasting human west nile virus incidence.

Author information

  • 1Center for Computational Science, Tulane University, New Orleans, Louisiana, USA.
  • 2School of Public Health and Tropical Medicine, Tulane University, New Orleans, Louisiana, USA.
  • 3Department of Pathobiological Sciences, Louisiana State University, Baton Rouge, Louisiana, USA.
  • 4Department of Mathematics, Tulane University, New Orleans, Louisiana, USA.
  • 5Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana, USA.

Abstract

We have identified environmental and demographic variables, available in January, that predict the relative magnitude and spatial distribution of West Nile virus (WNV) for the following summer. The yearly magnitude and spatial distribution for WNV incidence in humans in the United States (US) have varied wildly in the past decade. Mosquito control measures are expensive and having better estimates of the expected relative size of a future WNV outbreak can help in planning for the mitigation efforts and costs. West Nile virus is spread primarily between mosquitoes and birds; humans are an incidental host. Previous efforts have demonstrated a strong correlation between environmental factors and the incidence of WNV. A predictive model for human cases must include both the environmental factors for the mosquito-bird epidemic and an anthropological model for the risk of humans being bitten by a mosquito. Using weather data and demographic data available in January for every county in the US, we use logistic regression analysis to predict the probability that the county will have at least one WNV case the following summer. We validate our approach and the spatial and temporal WNV incidence in the US from 2005 to 2013. The methodology was applied to forecast the 2014 WNV incidence in late January 2014. We find the most significant predictors for a county to have a case of WNV to be the mean minimum temperature in January, the deviation of this minimum temperature from the expected minimum temperature, the total population of the county, publicly available samples of local bird populations, and if the county had a case of WNV the previous year.

KEYWORDS:

West Nile virus; arbovirus; disease model; infectious disease; principal components; statistical model; statistics

PMID:
25914857
[PubMed]
PMCID:
PMC4398566
Free PMC Article
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12.
PLoS One. 2013 Dec 2;8(12):e81211. doi: 10.1371/journal.pone.0081211. eCollection 2013.

Use of anti-Aedes aegypti salivary extract antibody concentration to correlate risk of vector exposure and dengue transmission risk in Colombia.

Author information

  • 1Louisiana State University, Baton Rouge, Louisiana, United States of America ; Universidad de Pamplona, Pamplona, Colombia.

Abstract

Norte de Santander is a region in Colombia with a high incidence of dengue virus (DENV). In this study, we examined the serum concentration of anti-Aedes salivary gland extract (SGE) antibodies as a biomarker of DENV infection and transmission, and assessed the duration of anti-SGE antibody concentration after exposure to the vector ceased. We also determined whether SGE antibody concentration could differentiate between positive and negative DENV infected individuals and whether there are differences in exposure for each DENV serotype. We observed a significant decrease in the concentration of IgG antibodies at least 40 days after returning to an "Ae. aegypti-free" area. In addition, we found significantly higher anti-SGE IgG concentrations in DENV positive patients with some difference in exposure to mosquito bites among DENV serotypes. We conclude that the concentration of IgG antibodies against SGE is an accurate indicator of risk of dengue virus transmission and disease presence.

PMID:
24312537
[PubMed - indexed for MEDLINE]
PMCID:
PMC3846924
Free PMC Article
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13.
Am J Trop Med Hyg. 2013 May;88(5):986-96. doi: 10.4269/ajtmh.12-0109. Epub 2013 Mar 11.

Ecology of potential West Nile virus vectors in Southeastern Louisiana: enzootic transmission in the relative absence of Culex quinquefasciatus.

Author information

  • 1Division of Vector-Borne Diseases, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO 80521, USA. mjg9@cdc.gov

Abstract

A study of West Nile virus (WNV) ecology was conducted in St. Tammany Parish, Louisiana, from 2002 to 2004. Mosquitoes were collected weekly throughout the year using Centers for Disease Control and Prevention (CDC) light traps placed at 1.5 and 6 m above the ground and gravid traps. A total of 379,466 mosquitoes was collected. WNV was identified in 32 pools of mosquitoes comprising four species; 23 positive pools were from Culex nigripalpus collected during 2003. Significantly more positive pools were obtained from Cx. nigripalpus collected in traps placed at 6 m than 1.5 m that year, but abundance did not differ by trap height. In contrast, Cx. nigripalpus abundance was significantly greater in traps placed at 6 m in 2002 and 2004. Annual temporal variation in Cx. nigripalpus peak seasonal abundance has important implications for WNV transmission in Louisiana. One WNV-positive pool, from Cx. erraticus, was collected during the winter of 2004, showing year-round transmission. The potential roles of additional mosquito species in WNV transmission in southeastern Louisiana are discussed.

PMID:
23478575
[PubMed - indexed for MEDLINE]
PMCID:
PMC3752769
Free PMC Article
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14.
J Med Entomol. 2012 Nov;49(6):1189-97.

Sequence, secondary structure, and phylogenetic analyses of the ribosomal internal transcribed spacer 2 (ITS2) in members of the North American Signifera Group of Orthopodomyia (Diptera: Culicidae).

Author information

  • 1Department of Tropical Medicine, School of Public Health and Tropical Medicine, Tulane University, New Orleans, LA 70112, USA. bdbyrd@email.wcu.edu

Abstract

Mosquitoes of the genus Orthopodomyia (Diptera: Culicidae) are little known and of uncertain epidemiological importance. In the United States, there are three Orthopodomyia species (i.e., Or. signifera (Coquillett), Or. alba Baker, and Or. kummi Edwards); they are all members of the Signifera Group based on the current morphological taxonomy. In the course of identifying recently collected specimens, a problem was found with the current key morphological characters for separating the fourth instar larvae of Or. signifera and Or. kummi. Internal transcribed spacer two sequences of the rDNA were obtained to resolve the identities. The Orthopodomyia internal transcribed spacer two ranged in size from 193 (Or. kummi) to 244 bp (Or. signifera) (mean = 218 bp) and were slightly Adenine/Thymine enriched (44.7% Guanine/Cytosine on average). Putative secondary structures reveal structural homologies (four domains) consistent between species that also feature conserved sequences specific to mosquitoes (e.g., a conserved motif on the 3' aspect of the longest helix: GARTACATCC). Sequence analyses suggest that in certain areas of southwestern North America, hybridization may occur between Or. kummi and Or. signifera. Furthermore, our analyses confirm that Or. californica (a junior synonym of Or. signifera) is indeed Or. signifera. To our knowledge, this is the first sequence-based phylogenetic and molecular analysis of the Orthopodomyia.

PMID:
23270146
[PubMed - indexed for MEDLINE]
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15.
Med Vet Entomol. 2013 Sep;27(3):284-97. doi: 10.1111/j.1365-2915.2012.01048.x. Epub 2012 Oct 18.

Proof of concept for a novel insecticide bioassay based on sugar feeding by adult Aedes aegypti (Stegomyia aegypti).

Author information

  • 1Department of Entomology, North Carolina State University, Raleigh, NC 27695, U.S.A.

Abstract

Aedes aegypti L. (Stegomyia aegypti) (Diptera: Culicidae) is the principal vector of dengue and yellow fever viruses in tropical and subtropical regions of the world. Disease management is largely based on mosquito control achieved by insecticides applied to interior resting surfaces and through space sprays. Population monitoring to detect insecticide resistance is a significant component of integrated disease management programmes. We developed a bioassay method for assessing insecticide susceptibility based on the feeding activity of mosquitoes on plant sugars. Our prototype sugar-insecticide feeding bioassay system was composed of inexpensive, disposable components, contained minimal volumes of insecticide, and was compact and highly transportable. Individual mosquitoes were assayed in a plastic cup that contained a sucrose-permethrin solution. Trypan blue dye was added to create a visual marker in the mosquito's abdomen for ingested sucrose-permethrin solution. Blue faecal spots provided further evidence of solution ingestion. With the sugar-insecticide feeding bioassay, the permethrin susceptibility of Ae. aegypti females from two field-collected strains was characterized by probit analysis of dosage-response data. The field strains were also tested by forced contact of females with permethrin residues on filter paper. Dosage-response patterns were similar, indicating that the sugar-insecticide feeding bioassay had appropriately characterized the permethrin susceptibility of the two strains.

© 2012 The Royal Entomological Society.

KEYWORDS:

Aedes aegypti; anthrone; bioassay; insecticide resistance; permethrin; sugar feeding

PMID:
23077986
[PubMed - indexed for MEDLINE]
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16.
J Med Entomol. 2012 Sep;49(5):1092-102.

Host preference of the arbovirus vector Culex erraticus (Diptera: Culicidae) at Sonso Lake, Cauca Valley Department, Colombia.

Author information

  • 1Department of Tropical Medicine, Tulane University, 1440 Canal St, Suite 2210, New Orleans, LA 70112, USA. ian.mendenhall@duke-nus.edu.sg

Abstract

Culex erraticus (Dyar & Knab) is a competent vector of Eastern equine encephalitis virus and subtype IC Venezuelan equine encephalitis virus, and both St. Louis encephalitis virus and West Nile virus have been isolated from field-collected specimens. Previous bloodmeal analysis studies have shown this species to be a generalist, feeding on a variety of mammals, birds, reptiles, and amphibians. This behavior can bridge arboviral transmission across different vertebrate groups. Our study examined the host preference of Cx. erraticus at Sonso Lake in Colombia. From July to August 2008, blood-engorged mosquitoes were collected from resting boxes, while vertebrate abundance was determined to calculate host preference. Based on mitochondrial DNA analysis of bloodmeals, birds were the predominant hosts (57.6%), followed by mammals (30.8%), and reptiles (6.7%); 9.5% of the bloodmeals were mixed. The most commonly fed upon species were: limpkin, black-crowned night-heron, striated heron, human, and capybara. Forage ratios showed the least bittern, limpkin, Cocoi heron, striated heron, capybara, and black-crowned night heron were preferred hosts across all vertebrates. Of the available avifauna, the least bittern, limpkin, striated heron, Cocoi heron, and black-crowned night heron were preferred, whereas the bare faced ibis, great egret, snowy egret, and cattle egret were under-used. This study shows that while Cx. erraticus is an opportunistic feeder, using diverse vertebrate hosts in the environment, certain avian species are targeted preferentially for bloodmeals.

PMID:
23025191
[PubMed - indexed for MEDLINE]
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17.
Malar J. 2012 Jun 10;11:193. doi: 10.1186/1475-2875-11-193.

PCR detection of malaria parasites in desiccated Anopheles mosquitoes is uninhibited by storage time and temperature.

Author information

  • 1Department of Tropical Medicine, Tulane University, New Orleans, LA 70112, USA. mrider@tulane.edu

Abstract

BACKGROUND:

Reliable methods to preserve mosquito vectors for malaria studies are necessary for detecting Plasmodium parasites. In field settings, however, maintaining a cold chain of storage from the time of collection until laboratory processing, or accessing other reliable means of sample preservation is often logistically impractical or cost prohibitive. As the Plasmodium infection rate of Anopheles mosquitoes is a central component of the entomological inoculation rate and other indicators of transmission intensity, storage conditions that affect pathogen detection may bias malaria surveillance indicators. This study investigated the effect of storage time and temperature on the ability to detect Plasmodium parasites in desiccated Anopheles mosquitoes by real-time polymerase chain reaction (PCR).

METHODS:

Laboratory-infected Anopheles stephensi mosquitoes were chloroform-killed and stored over desiccant for 0, 1, 3, and 6 months while being held at four different temperatures: 28, 37, -20 and -80°C. The detection of Plasmodium DNA was evaluated by real-time PCR amplification of a 111 base pair region of block 4 of the merozoite surface protein.

RESULTS:

Varying the storage time and temperature of desiccated mosquitoes did not impact the sensitivity of parasite detection. A two-way factorial analysis of variance suggested that storage time and temperature were not associated with a loss in the ability to detect parasites. Storage of samples at 28°C resulted in a significant increase in the ability to detect parasite DNA, though no other positive associations were observed between the experimental storage treatments and PCR amplification.

CONCLUSIONS:

Cold chain maintenance of desiccated mosquito samples is not necessary for real-time PCR detection of parasite DNA. Though field-collected mosquitoes may be subjected to variable conditions prior to molecular processing, the storage of samples over an inexpensive and logistically accessible desiccant will likely ensure accurate assessment of malaria parasite presence without diminishing PCR-detection of parasites in mosquitoes stored for at least six months.

PMID:
22682161
[PubMed - indexed for MEDLINE]
PMCID:
PMC3405449
Free PMC Article
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18.
J Med Entomol. 2012 May;49(3):522-34.

Genetic structure of Culex erraticus populations across the Americas.

Author information

  • 1Department of Tropical Medicine, Tulane University, New Orleans, LA 70112, USA. ian.mendenhall@duke-nus.edu.sg

Abstract

Culex erraticus (Dyar & Knab) is a potential competent vector for several arboviruses such as Eastern and Venezuelan equine encephalitis viruses and West Nile virus. It therefore may play a role in the maintenance and spread of viral populations in areas of concern, including the United States where it occurs in >33 states. However, little information is available on potential barriers to movement across the species' distribution. Here, we analyze genetic variation among Cx. erraticus collected from Colombia, Guatemala, and nine locations in the United States to better understand population structure and connectivity. Comparative sequence analysis of the second internal transcribed spacer and mitochondrial NADH dehydrogenase genes identified two major lineages of sampled populations. One lineage represented the central and eastern United States, whereas the other corresponded to Central America, South America, and the western United States. Hierarchical analysis of genetic variation provided further evidence of regional population structure, although the majority of genetic variation was found to reside within populations, suggestive of large population sizes. Although significant physical barriers such as the Chihuahuan Desert probably constrain the spread of Cx. erraticus, large population sizes and connectivity within regions remain important risk factors that probably contribute to the movement of arboviruses within and between these regions.

PMID:
22679859
[PubMed - indexed for MEDLINE]
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Publication Types, MeSH Terms, Secondary Source ID, Grant Support

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Secondary Source ID

Grant Support

19.
Trans R Soc Trop Med Hyg. 2012 Jun;106(6):387-9. doi: 10.1016/j.trstmh.2012.02.007. Epub 2012 Apr 20.

Yellow fever virus susceptibility of two mosquito vectors from Kenya, East Africa.

Author information

  • 1Department of Tropical Medicine, Tulane University, 1440 Canal Street Suite 2210-SL17, New Orleans, Louisiana 70112, USA. brett.ellis@duke-nus.edu.sg

Abstract

Yellow fever is an unpredictable disease of increasing epidemic threat in East Africa. Aedes (Stegomyia) aegypti has never been implicated as a vector in this region and recent outbreaks have involved a newly emerging virus genotype (East African). To better understand the increasing epidemic risk of yellow fever in East Africa, this study is the first to investigate the vector competence for an emerging East African virus genotype in Kenyan A. aegypti sensu latu (s.l) and A. (Stegomyia) simpsoni s.l. mosquito species. Using first filial generation mosquitoes and a low passage yellow fever virus, this study demonstrated that although A. aegypti s.l. is a competent vector, A. simpsoni s.l. is likely a more efficient vector.

Copyright © 2012 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved.

PMID:
22521217
[PubMed - indexed for MEDLINE]
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20.
J Med Entomol. 2011 Nov;48(6):1210-3.

Disproportionate mosquito feeding on aggregated hosts.

Author information

  • 1Department of Epidemiology, Tulane University, School of Public Health and Tropical Medicine, 1400 Canal Street, New Orleans, LA 70112, USA. ivo.foppa@gmail.com

Abstract

Despite the importance of per-capita feeding rates for mosquito-borne transmission dynamics, the relationship between host aggregation and per-capita feeding rates remains poorly characterized. We conducted indoor experiments to investigate how Culex quinquefasciatus (Say) mosquitoes distribute their blood feeding on variably aggregated domestic chickens (Callus gallus domesticus L.) (one chicken vs. a flock of seven to nine birds). Mosquitoes were always more likely to feed on the larger chicken group; yet, the single chicken tended to be fed on at a higher per-capita rate. When 10 chickens were available the feeding intensity was 4.5 times higher for the single chicken compared with the flock. We conclude that more highly aggregated hosts may experience lower exposure to mosquito bites than less aggregated hosts.

PMID:
22238881
[PubMed - indexed for MEDLINE]
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