|Year : 2021 | Volume
| Issue : 2 | Page : 135-140
Molecular xenomonitoring of Dengue, Chikungunya and Zika infections: a year-round study from two Dengue endemic districts of central India
Gyan Chand, Subhash Godbole, L Shivlata, Lalit Kumar Sahare, Mahendra Ukey, LS Kaushal, Pradip V Barde
ICMR-National Institute of Research in Tribal Health (NIRTH), Nagpur Road, Garha, Jabalpur, India
|Date of Submission||20-Sep-2019|
|Date of Acceptance||16-Jan-2020|
|Date of Web Publication||13-Jan-2022|
Dr. Pradip V Barde
Scientist E, ICMR-National Institute of Research in Tribal Health (NIRTH), Nagpur Road, Garha, Jabalpur
Source of Support: None, Conflict of Interest: None
Background & objectives: Infections caused by arboviruses and transmitted by Aedes species mosquitoes are a serious health concern. India is endemic for diseases like Dengue, Chikungunya and recently Zika has been reported from few states. Vector control is the only way to contain these diseases, however, data regarding vectors from central India is lacking; to fulfill the lacuna we conducted this study.
Methods: Entomological surveys were conducted from November 2017 to December 2018 for Aedes species in Dengue endemic areas of central India. The mosquitoes were identified, pooled and tested for the presence of Dengue, Chikungunya and Zika viruses by RT-PCR. The PCR products were sequenced to identify serotypes and genotypes of viruses.
Results: A total of 2991 adults of Aedes specimens were collected and tested. Ae. aegypti (94.6%) was found to be the most abundant species. Highest mosquito density was recorded in the monsoon periods. Dengue (n=5) and Chikungunya (n=4) virus were detected from pools of female Ae. aegypti. One pool of male Ae. aegypti was positive for Dengue virus-3 and Chikungunya virus. Zika virus was not detected from any pool.
Interpretation & conclusion: The findings suggest that Ae. aegypti is the principal vector of Dengue and Chikungunya, which is capable to transmit these viruses vertically. The findings have epidemiological importance and will be helpful to program managers.
Keywords: Aedes; Chikungunya; Dengue; vertical transmission; Zika
|How to cite this article:|
Chand G, Godbole S, Shivlata L, Sahare LK, Ukey M, Kaushal L S, Barde PV. Molecular xenomonitoring of Dengue, Chikungunya and Zika infections: a year-round study from two Dengue endemic districts of central India. J Vector Borne Dis 2021;58:135-40
|How to cite this URL:|
Chand G, Godbole S, Shivlata L, Sahare LK, Ukey M, Kaushal L S, Barde PV. Molecular xenomonitoring of Dengue, Chikungunya and Zika infections: a year-round study from two Dengue endemic districts of central India. J Vector Borne Dis [serial online] 2021 [cited 2022 Jan 29];58:135-40. Available from: https://www.jvbd.org/text.asp?2021/58/2/135/321753
| Introduction|| |
Arboviruses, transmitted by insect vectors upon infection cause an array of symptoms in humans, ranging from mild fever to deadly hemorrhagic fever, shock syndrome, hepatitis, encephalitis and microcephaly in newborns etc. and thus are responsible for huge health and economic burden across the world, especially in the tropics and subtropics. The species of Aedes mosquitoes, Ae. aegypti and Ae. albopictus are incriminated as vectors of Dengue virus (DENV), Chikungunya virus (CHIKV), Yellow fever Virus (YFV) and Zika Virus (ZIKV) in the tropical and subtropical countries,. Dengue (DEN) and Chikungunya (CHIK) are important arboviral diseases in India and Ae. Aegypti is the principal vector; these viruses are also detected from Ae. albopictus and Ae. vittatus mosquitoes,,. In the recent past, Zika emerged as a new public health threat in Brazil and since 2015, it has reached to a pandemic level after its spread to Mexico, Central America, the Caribbean and South Americas. Subsequently, cases were detected in India from Rajasthan, Gujarat and Tamil Nadu states,,,,.
These viruses are generally maintained in man-mosquito-man cycle, however, they can also be transmitted vertically from infected mother to offspring and this phenomenon is known as transovarial transmission (TOT),,,. The TOT is presumed to be epidemiologically important as it can not only trigger new transmission cycle, but also can help in maintaining the viruses among the mosquito population during the inter-epidemic seasons,. Each of Aedes species has typical behavioral pattern, feeding and egg laying preferences,. Identifying important vector species and its behavior in a given area can help in targeting specific ecological niches preferred by the particular species and can not only have better control but also can save lot of precious resources.
In the absence of any specific treatment and licensed vaccine, vector control is the only tool for combating these diseases. However, very limited information is available regarding vectors and xenodiagnosis of arboviruses from the central part of India. We conducted year-round xeno-monitoring for DENV, CHIKV and ZIKV in two known DEN endemic areas of central India with the objective to understand intricacies of vector dynamics of the area.
| Material & Methods|| |
Study period and areas
The study was conducted from November 2017 to December 2018. Two areas of known DEN activities in central India were selected. One was from Jabalpur city (urban) (23°10’N 79°56’E) and another was the villages of Narsinghpur district (22.9466° N, 79.1944° E) (rural) that was about 120 km away from Jabalpur. The climatic conditions of both areas are quite similar. In summer, the maximum temperature rises up to 45°C and in winters the temperature drops to minimum 5°C. These areas enjoy good rainfall in monsoon, which averages to 120 cm. The place experienced outbreaks of DEN in the recent past,. Further, we had observed DEN positivity around 24% among suspected cases in earlier year (2016) from these areas.
Mosquito surveys and identification
Door to door (indoor and outdoor) larval surveys were carried out once every month in each study area to identify preferred breeding (oviposition) habitats and establish Breteau index (BI). The adult Aedes mosquitoes were collected every fortnight. The adults were collected using mouth aspirators and a torch. The collected mosquitoes were transported to the laboratory in a labeled glass test tube maintaining the cold chain. On every visit at least 100 randomly picked households were surveyed by same trained survey team. The containers having mosquito larvae/pupas were recorded and the larvae/pupas in the containers were destroyed. The collected adults were identified using standard key.
The identified specimens were categorized as male or female, females were further categorized as unfed or fed based on abdominal condition. Specimens with the same gender, abdominal condition collected from a same area, during the same visit, belonging to same species were pooled together. Based on mosquitoes collected during a particular field visit, the pool size varied from 1 to 10. The pools were preserved at -70°C until tested by RT-PCR.
The pool mosquitoes were homogenized in 100 μl of TRI reagents (Molecular Research Centre Cat No -TR118 Cincinati, OH, USA) and then, this was made up to 200 μl, vortexed and used for RNA extraction using the manufacturer’s protocol. The final pellet was dissolved in 30 μl nuclease free water. The extracted RNA was used for detecting the presence of DENV, CHIKV and ZIKV using the protocol described by Lanciotti et al. (1992), Kumar et al. (2007) and Faye et. al. (2008), respectively,,. The RT-PCRs were done using Invitrogen kit (Cat. No.: 12574-026, California, USA) and the resulting RT-PCR products were visualized on 2% agarose gel. The RNAs from positive samples were amplified for sequencing using Invitogen kit with proof reading activity (Cat. No.: 11708-13, California, USA). The RT-PCR products bands (511 bp for DENV and 330 bp for CHIKV) was gel excised, eluted and subjected to sequencing analysis as described earlier.
Human samples testing
The samples of patients suspected of DEN and CHIK were referred for diagnosis to this institute’s virology lab as it is designated as Apex Referral Laboratory for DEN and CHIK by National Vector Borne Disease Control Program (NVBDCP) for central India. The samples collected during the study period in the acute phase of illness (< 5 days of illness) from the study area were tested by CDCs Trioplex real time RT-PCR (qRTPCR).
To identify serotype, genotype and examine the identity and diversity among the viral sequences from mosquitoes and human samples, the nucleotide sequences obtained were manually curated and BLAST analysis of the nucleotide sequences was performed to find the homology and viral serotype and genotype. Amino acid sequences deduced from nucleotide sequences were compared with amino acid sequences of DENV and CHIKV samples collected from humans.
The data were first entered into MS Excel. To study season-wise differences in mosquito density, the mosquitoes collected per household per month was calculated. The resulting figures were compared using student’s t test. The differences in Breteau index (BI) over a period was analyzed using ANOVA. The correlation coefficient (r2) between BI and number of DENV and CHIKV qRT-PCR cases were analyzed using online software,.
The study was approved by ICMR-National Institute for Research in Tribal Health’s Institutional Ethics Committee in meeting held on 14 March 2017 vide. No: 201701/12. The mosquito surveys and mosquito collections in and around houses was done after taking house owner’s informed oral consent. The human samples were collected and tested after taking informed written consent from the patients.
| Results|| |
A total of 11,860 (Urban: 5290, Rural: 6570) households from both the study areas were surveyed during the study period; of this, 11.67% [1385 (Urban: 628, Rural: 757)] households were found positive for immature stages of Aedes species. The larvae were mainly detected in cement tanks (Urban: 25.70%, Rural: 22.77%), air cooler (Urban: 7.94%, Rural: 2.5%), followed by discarded plastic, mud and metal containers metal drums, and overhead water tanks.
A total of 2991 adult Aedes mosquitoes of both sexes were collected during the study period. The adult and immature stages of Aedes species of mosquitoes were detected all around the year in both the areas. The overall BI was significantly higher (f= 39.225 P=0.0001) in the monsoon and post-monsoon months as compared to the summer in both areas [Figure 1]A & [Figure 1]B. Similarly, significantly higher numbers of adult Aedes were detected in the monsoon from urban (P=0.001) area, although higher number of adults were detected in a rural area in the monsoon, but the difference was not significant (P=0.29) when compared with that of the summer. The gender-wise details of Aedes species collected, tested during the study period are given in [Table 1]. Ae. Aegypti was the most dominant species with 94.6% of the total collected population during the study period in both the areas. Interestingly, Ae. vittaus was detected from urban areas. On the other hand, Ae. albopictus, was detected from the villages of Narsinghpur [Table 1].
|Figure 1: A. [Jabalpur (urban area)] and B. [Narsinghpur (rural area)]; showing month and year over 14 months on X axis, Breteau index on Y axis, the human cases positive for Dengue and Chikungunya by qRT-PCR on secondary X axis.|
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|Table 1: Showing mosquitoes collected and tested by RT PCR for DENV, CHIKV and ZIKV during study period|
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A total of 394 pools of different species of mosquitoes were tested by RT-PCR and five pools of female Ae. aegypti from Jabalpur were positive for DENV and similarly four pools of female Ae. aegypti from Jabalpur were found positive for CHIKV. The minimum infection rate (MIR) for urban area was 4.5 and 3.6 per 1000 mosquitoes for DENV and CHIKV, respectively. One pool of male Ae. aegypti was positive for DENV and CHIKV [Table 1]. ZIKV was not detected from any pool. A total of 2078 suspected cases were tested by RTPCR during the study period from study areas, of which 518 (24.9%) and 676 (32.5%) were positive for of DEN and CHIK respectively. No human case of Zika was detected. Peak in human cases of DEN and CHIK was noted in August and September months [Figure 1].
The correlation analysis between BI and DENV and CHIKV RTPCR positive cases showed that the DENV (r2=0.54) and CHIKV (r2=0.87) cases were positively correlated to BI in urban area; however, there was a weak correlation in DENV (r2=0.23) and CHIKV (r2= 0.09) cases in rural area [Figure A] & [Figure B]. On the other hand, adult densities and RTPCR positive cases did not correlate in urban and rural areas and coefficient of determination (r2) for DENV and CHIKV were 0.33 and 0.42 respectively in urban area and in rural area r2 was 0.004 for DENV and 0.00 for CHIKV.
The sequence analysis revealed that among five pools positive for DENV, the serotype of the four samples were DENV-3 (accession no. MK829132 and MK829134-36) and one was DENV-1 (accession no. MK829133). On further analysis of DENV sequences from mosquitoes showed that genotype III of DENV-3 and genotype I of DENV-1 were in circulation. The sequence analysis of CHIKV (Accession no. MK829137-38) showed that ECSA genotype was present in the mosquito. Further detailed analysis and comparison of contemporary sequences of DENV and CHIKV viruses from human samples from same area showed that there was no change in CHIKV and DENV from mosquito at the amino acid level.
| Discussion|| |
We present for the first time a comprehensive entomological picture in relation to important vector-borne viral diseases from urban and rural parts of central India. Door to door surveys conducted by our teams round the year demonstrated the perennial presence of Aedes mosquitoes in both the study areas. Ae. aegypti was the most dominant species detected in the study areas. Though we detected other species of Aedes, but DENV and CHIKV were not detected among them, confirming Ae. aegypti as principal vector of these diseases in central India.
The BI was highest in the monsoon and the post monsoon season due to favorable humidity and temperature for mosquito breeding and similar findings were documented earlier from other parts of the country,,. The observation regarding breeding sites is different than the study by Jain et.al. (2016) detected maximum breeding in underground cement tanks, we detected maximum larvae and pupa in indoor cement tanks; these tanks are only topped-up and rarely emptied and cleaned, thus, provide best oviposition sites for indoor resting Ae. aegypti. Although, the prevalence (BI) of Aedes was low in the peak the summer, in the area during the study period; it is worthwhile to mention that outbreaks are documented in summer from other parts of the country, because of erratic water supply in the summer leading to water storing practices, providing Aedes oviposition sites. The health authorities need to be vigilant to avoid such situation.
Ae. aegypti is day biting highly anthropophilic mosquito and prefers to stay indoors, thus giving ample opportunities for interaction with human,,,. Ae. albopictus was detected from the villages of Narsinghpur, and this species is a potent vector of DENV and CHIKV and becomes more so when harboring A226V mutation in envelope (E1) gene. Further monitoring and in-depth vector competence/susceptibility studies are needed on this species,,. Earlier, we have detected Ae. vitattus from peridemostic, rocky areas of central India during out-breaks and this species was detected from urban area this time. These entomological observations will provide vital information for program managers to focus their vector control efforts and keep a vigilant eye on the new emerging vectors in the area.
We observed a significant correlation between the numbers of positive cases and BI in urban area, however, the same was not seen in rural areas. It could be due to scanty population, resulting in less human-mosquito contact; on the other hand, we might have missed few human cases owing remoteness of rural area. The data clearly show the importance of vector density in contorting the DENV and CHIKV infections. Further, we observed weak correlation between adult index verses cases indicating BI monitoring is a better tool for vector surveillance than adult index monitoring. Aedes adult mosquito surveys, although sensitive; are labor intensive and time consuming thus, BI or pupal monitoring which are easy to practice could prove efficient in vector surveillance indicating risks of outbreaks. The policy makers need to prepare a program of vector control, especially to reduce egg laying sites and conduct information, education communication (IEC) and behavior change communication (BCC) for social mobilization and launch it pre-monsoon periods to avoid an outbreak like situations.
DENV and CHIKV were detected from female mosquitoes caught from urban area, however, not from rural area and probably because of a lesser number of cases. Zika virus was not detected from any sample. Detection of DENV-3 in maximum pools was in concordance with the higher number of human cases infected with DENV- 3 in this area. Moreover, the pools were positive in the month of September and October, and in the same months, when the maximum human cases for DENV and CHIKV were observed. Studies have reported MIR up to 35 and we detected comparatively lower MIR. The probable reason of lower MIR is that the study test was performed only on field collected adult mosquitoes and not with adults reared from field collected larvae, which may have a higher chance of carrying these viruses,,. We have seen the dominance of DENV-3 among human cases in the recent years in central India. It will be worthwhile to evaluate vector competence of Ae. aegypti for all serotypes of DENV to understand the intricacy of dengue epidemiology. Genotype III of DENV, genotype I of DENV-1 and ECSA genotype of CHIKV detected in the mosquito population showing 100% similarity at the amino acid level with viral sequences detected from human indicate the circulation of homologous population of viruses, but we suggest to conduct complete envelope gene sequencing of these viruses as it has been shown that even a single amino acid mutation in the envelope protein may affect vector competence, immune response and virus binding to host cell,,.
Vertical transmission is the phenomenon by which arboviruses are maintained in nature escaping vertebrate host especially in the inter-epidemic period, moreover it can start a fresh transmission cycle,,,,,. The vertical/ TOT of DENV is well documented in DEN endemic countries including India,. Although, all four serotypes of DENV have been shown to undergo vertical transmission, but DENV 2 and DENV 3 are the most frequently detected serotypes. In India, DENV-3 is more frequently reported from males or immature stage and we too detected DENV-3 from one pool of male mosquitoes,,. On the other hand, the TOT/Vertical transmission of CHIKV is a rare event. However, the ECSA genotype seems to have adapted for this phenomenon,. This is the first report of vertical transmission of DENV and CHIKV from central India.
Not testing immature stage of mosquitoes for viruses under surveillance and conducting the sequencing on limited parts of the genome of CHIKV and DENV are few of the limitations of the study. However, this year-round study gives sufficient information as it has sufficient numbers to support the findings.
| Conclusion|| |
This study for the first time provides a picture of vectors of DENV and CHIKV in two DEN endemic regions of central India. Ae. aegypti was incriminated as vector which was capable of transmitting the virus vertically. Breteau index was found to be a more efficient monitoring tool than adult index. This study will not only serve as base line for future studies but also help program managers to plan evidence-based vector control operations.
Conflict of interest: None
| Acknowledgements|| |
The authors are grateful to the Secretary to the Government of India, DHR, MoH & FW, and The Director General, ICMR for funding under establishment of grade II virology lab (Grant No. VIR/43/2011-ECD-I) and Vector surveillance for ZIKV in selected high-risk areas in India (Grant No. VIR/09/2017-ECD-I). The authors also thank project staff of both the projects for technical help. The authors thank by Dr. Aparup Das, Director, ICMR-NIRTH, Jabalpur for encouragement during the study. Authors are thankful to Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Disease, division of Vector-Borne Diseases, DEN Branch, San Juan USA providing DENV diagnosis kits for qRT-PCR. The manuscript has been approved by the publication screening committee of ICMR - NIRTH, Jabalpur and assigned with the number ICMR-NIRTH/ PSC/10/2019.
| References|| |
Paixão ES, Teixeira MG, Rodrigues LC. Zika, chikungunya and dengue: the causes and threats of new and re-emerging arboviral diseases. BMJ Glob Health
2018; 3(Suppl 1): e000530.
Moyes CL, Vontas J, Martins AJ, Ng LC, Koou SY, Dusfour I, et al
. Contemporary status of insecticide resistance in the major Aedes vectors of arboviruses infecting humans. PLoS Negl Trop Dis
2017; 11(7): e0005625.
Guidelines for integrated vector management for control of dengue/dengue heamorragic fever. Available from: nvbdcp.gov. in/Doc/dengue_1_.%20Director_Desk%20DGHS%20meeting%20OCT%2006
. (Accessed on January 1, 2019)
Sudeep AB, Shil P. Aedes vittatus (Bigot) mosquito: An emerging threat to public health. J Vector Borne Dis
Kumar NP, Bashir A, Abidha S, Sabesan S, Jambulingam P. Predatory potential of Platynectes sp. (Coleoptera: Dytiscidae) on Aedes albopictus
, the vector of dengue/chikungunya in Kerala, India. Trop Biomed
Kumar NP, Sabesan S, Krishnamoorthy K, Jambulingam P. Detection of Chikungunya virus in wild populations of Aedes albopictus
in Kerala State, India. Vector Borne Zoonotic Dis
. 2012; 12(10): 907–11.
Pan American Health Organisation. Zika virus infection – Epidemiological updates: Available from: www.paho.org
(Accessed on January 1, 2019)
Sapkal GN, Yadav PD, Vegad MM, Viswanathan R, Gupta N, Mourya DT. First laboratory confirmation on the existence of Zika virus disease in India. J Infect
. 2018; 76(3): 314–317.
Yadav PD, Malhotra B, Sapkal G, Nyayanit DA, Deshpande G, Gupta N, et al
. Zika virus outbreak in Rajasthan, India in 2018 was caused by a virus endemic to Asia. Infect Genet Evol
Lima VH, Lima TN. Natural vertical transmission of dengue virus in Aedes aegypti
and Aedes albopictus:
a systematic review. Parasit Vectors
. 2018; 11
Jain J, Kushwah RBS, Singh SS, Sharma A, Adak T, Singh O P, et al
. Evidence for natural vertical transmission of chikungu- nya viruses in field populations of Aedes aegypti
in Delhi and Haryana states in India-a preliminary report. Acta Trop
Smartt CT, Stenn TMS, Chen TY, Teixeira MG, Queiroz EP, Souza Dos Santos L, et al
. Evidence of Zika virus RNA fragments in Aedes albopictus
(Diptera: Culicidae) field-collected eggs from Camaçari, Bahia, Brazil. J Med Entomol
Dzul-Manzanilla F, Martínez NE, Cruz-Nolasco M Gutiérrez- Castro C, López-Damián L, Ibarra-López J, et al
. Evidence of vertical transmission and co-circulation of chikungunya and dengue viruses in field populations of Aedes aegypti
(L.) from Guerrero, Mexico. Trans R Soc Trop Med Hyg
2015; 110(2): 141–4.
Arunachalam N, Tewari SC, Thenmozhi V, Rajendran R, Paramasivan R, Manavalan R, et al
. Natural vertical transmission of dengue viruses by Aedes aegypti
in Chennai, Tamil Nadu, India. Indian J Med Res
2008; 127(4): 395–7.
Rosen L. Further observations on the mechanism of vertical transmission of flaviviruses by Aedes mosquitoes. Am J Trop Med Hyg
Day J F. Mosquito Oviposition Behavior and Vector Control. Insects
2016; 7(4): 65.
David Roiz, Anne L. Wilson, Thomas W. Scott, Dina M. Fonseca, Frédéric Jourdain, Pie Müller, et al
. Integrated Aedes management for the control of Aedes-borne diseases. PLoS Negl Trop Dis
. 2018; 12(12): e0006845.
Barde PV, Kori BK, Shukla MK, Bharti PK, Chand G, Kumar G, et al
. Maiden outbreaks of dengue virus 1 genotype III in rural central India. Epidemiol Infect
2015; 143(2): 412–8.
Singh N, Shukla M, Chand G, Barde PV, Singh MP. Vector-borne diseases in central India, with reference to malaria, filaria, dengue and chikungunya. WHO South East Asia J Public Health
2014; 3(1): 28–35.
Barraud, P. J. The Fauna of British India, including Ceylon and Burma. Diptera
. Vol. 5. Family Culieldae. Tribes Megarhinini and Culicini. 1934; pp.xxviii + 463 pp. ref.106.
Lanciotti R S, Calisher C H, Gubler D J, Chang G J, Vorndam A V. Rapid detection and typing of dengue viruses from clinical samples by using reverse transcriptase-polymerase chain reaction. J Clin Microbiol
1992; 30(3): 545–51.
Kumar C.V.M. Anthony A.M. Sai Gopal D.V.R. Molecular characterization of chikungunya virus from Andhra Pradesh, India & phylogenetic relationship with Central African isolates. Indian J Med Res 2007; 126(6): 534–540.
Faye O, Faye O, Dupressoir A, Weidmann M, Ndiaye M, Alpha Sall A. One-step RT-PCR for detection of Zika virus. J Clin Virol
2008; 43(1): 96–101.
Barde PV, Godbole S, Bharti PK, Gyan Chand, Agarwal M, Neeru Singh. Detection of dengue virus 4 from central India. Indian J Med Res
2012; 136(3): 491–4.
Biswas D, Dey S, Dutta RN, Hati AK. Observations on the breeding habitats of Aedes aegypti
in Calcutta following an episode of dengue haemorrhagic fever. Indian J Med Res
Wai KT, Arunachalam N, Tana S, Espino F, Kittayapong P, Abeyewickreme W, et al
. Estimating dengue vector abundance in the wet and dry season: implications for targeted vector control in urban and peri-urban Asia. Pathog Glob Health
2012; 106(8): 436–45.
Chouhan GS, Rodrigues FM, Shaikh BH, Ilkal MA, Khangaro SS, Mathur KN, et al
. Clinical & virological study of dengue fever outbreak in Jalore city, Rajasthan 1985. Indian J Med Res
Gubler, D.J. Epidemic Dengue/Dengue Hemorrhagic Fever as a Public Health, Social and Economic Problem in the 21st Century. Trends Microbiology
2002; 10(2): 100–103.
Christophers, S.R. Aedes aegypti (L.). In: Yellow Fever Mosquito
. Cambridge University Press: London, UK, 1960.
Delatte H, Desvars A, Bouétard A, Bord S, Gimonneau G, Vourc’h G, et al
. Blood-feeding behavior of Aedes albopictus
, a vector of Chikungunya on La Réunion. Vector-Borne Zoonotic Dis
2010; 10(3): 249–258.
Harrington LC, Edman, JD, Scott, TW. Why do female Aedes aegypti
(Diptera: Culicidae) feed preferentially and frequently on human blood? J. Med. Entomol
Medlock JM, Leach SA. Effect of climate change on vector-borne disease risk in the UK. Lancet Infect Dis
2015; 15(6): 721–30.
Knudsen AB. Global distribution and continuing spread of Aedes albopictus. Parassitologia
1995; 37(2-3): 91–7.
Cecílio AB, Campanelli ES, Souza KP, Figueiredo LB, Resende MC. Natural vertical transmission by Stegomyia albopicta as dengue vector in Brazil. Braz J Biol
2009; 69(1): 123–7.
Vazeille M, Moutailler S, Coudrier D, Rousseaux C, Khun H, Huerre M, et al
. Two Chikungunya Isolates from the Outbreak of La Reunion (Indian Ocean) Exhibit Different Patterns of Infection in the Mosquito Aedes albopictus. PLoS ONE
2007; 2(11): e1168.
Tsetsarkin KA, Vanlandingham DL, McGee CE, Higgs S. Single mutation in chikungunya virus affects vector specificity and epidemic potential. PLoS Pathog
2007; 3(12): e201.
Dowd KA, DeMaso CR, Pierson TC. Genotypic Differences in Dengue Virus Neutralization Are Explained by a Single Amino Acid Mutation That Modulates Virus Breathing. M Bio
2015; 6(6): e01559–15.
Joshi V, Singhi M, Chaudhary RC. Transovarial transmission of dengue 3 virus by Aedes aegypti. Trans R Soc Trop Med Hyg
1996; 90(6): 643–4.
Joshi V, Mourya DT, Sharma RC. Persistence of dengue-3 virus through transovarial transmission passage in successive generations of Aedes aegypti
mosquitoes. Am J Trop Med Hyg
2002; 67(2): 158–61.
Mourya DT. Absence of transovarial transmission of Chikungunya virus in Aedes aegypti
& Ae. albopictus
mosquitoes. Indian J Med Res
Mavale M, Parashar D, Sudeep A, Gokhale M, Ghodke Y, Ge-evarghese G, et al
. Venereal transmission of chikungunya virus by Aedes aegypti
mosquitoes (Diptera: Culicidae). Am J Trop Med Hyg
2010; 83(6): 1242–4.