Incrimination of Aedes aegypti and Aedes albopictus as vectors of dengue virus serotypes 1, 2 and 3 from four states of Northeast India

Mosquito-borne diseases in India over the past 50 years and their Global Public Health Implications: A Systematic Review

Mosquito-borne diseases (MBDs) pose a significant public health concern globally, and India, with its unique eco-sociodemographic characteristics, is particularly vulnerable to these diseases. This comprehensive review aims to provide an in-depth overview of MBDs in India, emphasizing their impact and potential implications for global health. The article explores distribution, epidemiology, control or elimination, and economic burden of the prevalent diseases such as malaria, dengue, chikungunya, Japanese encephalitis, and lymphatic filariasis, which collectively contribute to millions of cases annually. It sheds light on their profound effects on morbidity, mortality, and socioeconomic burdens and the potential for international transmission through travel and trade. The challenges and perspectives associated with controlling mosquito populations are highlighted, underscoring the importance of effective public health communication for prevention and early detection. The potential for these diseases to spread beyond national borders is recognized, necessitating a holistic approach to address the challenge. A comprehensive literature search was conducted, covering the past five decades (1972-2022), utilizing databases such as Web of Science, PubMed, and Google Scholar, in addition to in-person library consultations. The literature review analyzed 4,082 articles initially identified through various databases. After screening and eligibility assessment, 252 articles were included for analysis. The review focused on malaria, dengue, chikungunya, Japanese encephalitis, and lymphatic filariasis. The included studies focused on MBDs occurrence in India, while those conducted outside India, lacking statistical analysis, or published before 1970 were excluded. This review provides valuable insights into the status of MBDs in India and underscores the need for concerted efforts to combat these diseases on both national and global scales through consilience.

Molecular surveillance of dengue virus in field-collected Aedes mosquitoes from Bhopal, central India: evidence of circulation of a new lineage of serotype 2

Introduction

Dengue fever is hyperendemic in several Southeast and South Asian countries, including India, with all four serotypes (DENV 1-4) circulating at different periods and in different locations. Sustainable and improved virological and entomological surveillance is the only tool to prevent dengue and other vector-borne diseases.

Objectives

The present study has been carried out to detect and characterize the circulating dengue virus (DENV) in field-collected Aedes mosquitoes in Bhopal, Central India.

Methods

Aedes mosquitoes were collected from 29 localities within Bhopal city during October 2020 to September 2022. DENV infection was assessed in the individual head and thorax regions of Aedes mosquitoes using reverse transcriptase PCR. Positive samples were sequenced, and the circulating serotypes and genotypes were determined using phylogenetic analysis.

Results

DENV RNA was detected in 7 Aedes aegypti and 1 Aedes albopictus, with infection rates of 0.59 and 0.14%, respectively. Phylogenetic analysis revealed all the isolates belonged to DENV serotype 2 and distinctly clustered with the non-Indian lineage (cosmopolitan genotype 4a), which was not recorded from the study area earlier. The time to most common recent ancestor (TMRCA) of these sequences was 7.4 years old, with the highest posterior density (HPD) of 3.5-12.2 years, indicating that this new lineage emerged during the year 2014. This is the first report on the DENV incrimination in both Ae. aegypti and Ae. albopictus mosquitoes collected from Bhopal, Central India.

Conclusion

The observed emergence of the non-Indian lineage of DENV-2 in Bhopal, which again is a first report from the area, coincides with the gradual increase in DENV cases in Bhopal since 2014. This study emphasizes the importance of DENV surveillance and risk assessment in this strategically important part of the country to decipher its outbreak and severe disease-causing potential.

Molecular Evidence of Wolbachia Species in Wild-Caught Aedes albopictus and Aedes aegypti Mosquitoes in Four States of Northeast India

Wolbachia, a Gram-negative intracellular bacterium, naturally infects many arthropods, including mosquito vectors responsible for the spread of arboviral diseases such as Zika, chikungunya, and dengue fever. Certain Wolbachia strains are involved in inhibiting arbovirus replication in mosquitoes, and this phenomenon is currently being studied to combat disease vectors. A study was conducted in four states in north-eastern India to investigate the presence of natural Wolbachia infection in wild-caught Aedes albopictus and Aedes aegypti mosquitoes, the established vectors of dengue. The detection of a Wolbachia infection was confirmed by nested PCR and sequencing in the two mosquito species Ae. aegypti and Ae. albopictus. Positivity rates observed in Ae. aegypti and Ae. albopictus pools were 38% (44 of 115) and 85% (41 of 48), respectively, and the difference was significant (chi-square = 28.3174, p = 0.00000010). Sequencing revealed that all detected Wolbachia strains belonged to supergroup B. Although Wolbachia infection in Ae. aegypti has been previously reported from India, no such reports are available from north-eastern India. Data on naturally occurring Wolbachia strains are essential for selecting the optimal strain for the development of Wolbachia-based control measures. This information will be helpful for the future application of Wolbachia-based vector control measures in this part of the country.

First Report of Rubber Collection Bowls & Plastic and Bamboo Water Containers as the Major Breeding Source of Ae. albopictus with the Indigenous Transmission of Dengue and Chikungunya in Rural Forested Malaria-Endemic Villages of Dhalai District, Tripura, India: The Importance of Molecular Identification

BACKGROUND

With the reports of indigenous cases of dengue and chikungunya in the forest-covered rural tribal malaria-endemic villages of Dhalai District, Tripura, India, an exploratory study was undertaken to identify the vector breeding sites.

METHODS

From June 2021 to August 2022, mosquito larvae were collected from both natural and artificial sources in the villages, house premises, and their nearby forested areas outside of the houses. Other than morphological characterisation, Aedes species were confirmed by polymerase chain reaction targeting both nuclear (ITS2) and mitochondrial genes (COI) followed by bidirectional Sanger sequencing.

RESULTS

Aedes albopictus was abundantly found in this area in both natural and artificial containers, whereas Ae. aegypti was absent. Among the breeding sources of molecularly confirmed Ae. albopictus species, rubber collection bowls were found to be a breeding source reported for the first time. Plastic and indigenously made bamboo-polythene containers for storing supply water and harvesting rainwater in the villages with a shortage of water were found to be other major breeding sources, which calls for specific vector control strategies. Natural sources like ponds and rainwater collected on Tectona grandis leaves and Colocasia axil were also found to harbour the breeding, along with other commonly found sources like bamboo stumps and tree holes. No artificial containers as a breeding source were found inside the houses. Mixed breeding was observed in many containers with other Aedes and other mosquito species, necessitating molecular identification. We report six haplotypes in this study, among which two are reported for the first time. However, Aedes aegypti was not found in the area. Additionally, rubber collection bowls, ponds, and water containers also showed the presence of Culex quinquefasciatus and Culex vishnui, known JE vectors from this area, and reported JE cases as well. Different Anopheles vector spp. from this known malaria-endemic area were also found, corroborating this area as a hotbed of several vectors and vector-borne diseases.

CONCLUSIONS

This study, for the first time, reports the breeding sources of Aedes albopictus in the forested areas of Tripura, with rubber collection bowls and large water storage containers as major sources. Also, for the first time, this study reports the molecular characterisation of the Ae. albopictus species of Tripura, elucidating the limitations of morphological identification and highlighting the importance of molecular studies for designing appropriate vector control strategies. The study also reports the co-breeding of JE and malaria vectors for the first time in the area reporting these vector-borne diseases.

Nation-wide vector surveillance on Zika and Dengue did not indicate transmission of the American lineage-pandemic Zika virus in India

OBJECTIVES

Following the Public Health Emergency of International Concern declared on Zika by the World Health Organization during 2016, the Indian Council of Medical Research carried out nationwide vector surveillance for Zika and Dengue viruses (ZIKV and DENV) in India as a preparedness measure in 2016-19.

METHODS

High-risk zones distributed to 49 Districts in 14 states/union territories were included in the study. Seven ICMR institutions participated, following a standard operating protocol. Aedes specimens sampled weekly were processed by multiplex reverse transcriptase-polymerase chain reaction (RT-PCR) for ZIKV/DENV and random samples crosschecked with real-time RT-PCR for ZIKV.

RESULTS

Altogether, 79 492 Aedes specimens in 6492 pools were processed; 3 (0.05%) and 63 (0.97%) pools, respectively, were found positive for ZIKV and DENV. ZIKV infections were recorded in Aedes aegypti sampled during the 2018 sporadic Zika outbreak in Jaipur, Rajasthan. However, these belonged to the Asian lineage of the virus, already circulating in the country. Both Ae. aegypti and Aedes albopictus distributed to 8 states/union territories were found to be infected with DENV. Both sexes of Ae. albopictus were infected, indicating transovarial transmission.

CONCLUSION

This investigation evinced no active transmission of the American lineage-pandemic Zika virus in India during the pandemic period.

Dengue-2 and Guadeloupe Mosquito Virus RNA Detected in Aedes (Stegomyia) spp. Collected in a Vehicle Impound Yard in Santo André, SP, Brazil

In 2018-2019, we conducted mosquito collections in a municipal vehicle impound yard, which is 10 km from the Serra do Mar Environmental Protection Area in Santo André, SP, Brazil. Our aim is to study arboviruses in the impound yard, to understand the transmission of arboviruses in an urban environment in Brazil. We captured the mosquitoes using human-landing catches and processed them for arbovirus detection by conventional and quantitative RT-PCR assays. We captured two mosquito species, Aedes aegypti (73 total specimens; 18 females and 55 males) and Ae. albopictus (34 specimens; 27 females and 7 males). The minimum infection rate for DENV-2 was 11.5 per 1000 (CI95%: 1-33.9). The detection of DENV-2 RNA in an Ae. albopictus female suggests that this virus might occur in high infection rates in the sampled mosquito population and is endemic in the urban areas of Santo André. In addition, Guadeloupe mosquito virus RNA was detected in an Ae. aegypti female. To our knowledge, this was the first detection of the Guadeloupe mosquito virus in Brazil.