bims-mosdis 2021-10-10 papers

bims-mosdis

Biomed News

on Mosquito distribution and disease

Issue of 2021‒10‒10
23 papers selected by
Richard Halfpenny
Staffordshire University

First Report of Adult Aedes aegypti (Diptera: Culicidae) Resistance to Pyrethroids in Argentina.
The effect of irrigation on malaria vector bionomics and transmission intensity in western Ethiopia.
The determination of effective concentration of acethonilic Ipomoea cairica leaves extract against laboratory and field strains of Aedes albopictus and Aedes aegypti mosquito larvae.
Review of Anopheles Mosquito Species, Abundance, and Distribution in Ethiopia.
Efficacy of targeted indoor residual spraying with the pyrrole insecticide chlorfenapyr against pyrethroid-resistant Aedes aegypti.
Australian mosquito assemblages vary between ground and sub-canopy habitats.
Releasing incompatible males drives strong suppression across populations of wild and Wolbachia-carrying Aedes aegypti in Australia.
Wild populations of malaria vectors can mate both inside and outside human dwellings.
Searching for a sign of exotic Aedes albopictus (Culicidae) introduction in major international seaports on Kyushu Island, Japan.
The vectors of Plasmodium knowlesi and other simian malarias Southeast Asia: challenges in malaria elimination.
Nation-wide vector surveillance on Zika and Dengue did not indicate transmission of the "American lineage pandemic ZIKA virus" in India.
Detection and Establishment of Aedes notoscriptus (Diptera: Culicidae) Mosquitoes in Southern California, United States.
Chemical composition and the insecticidal activity of Aeollanthus pubescens leaf essential oil against Anopheles gambiae sensu stricto.
Genetic characterization of chikungunya virus isolates from Aedes aegypti mosquitoes collected during a recent outbreak in Bangkok, Thailand.
Interaction of climate and socio-ecological environment drives the dengue outbreak in epidemic region of China.
Gene flow between island populations of the malaria mosquito, Anopheles hinesorum, may have contributed to the spread of divergent host preference phenotypes.
Analysis of international traveler mobility patterns in Tokyo to identify geographic foci of dengue fever risk.
Epidemiology of the zoonotic malaria Plasmodium knowlesi in changing landscapes.
Selection of sites for field trials of genetically engineered mosquitoes with gene drive.
The global burden of Plasmodium vivax malaria is obscure and insidious.
West Nile virus in Italy: the reports of its disappearance were greatly exaggerated.
Dengue outbreaks in the COVID-19 era: Alarm raised for Asia.
Malaria parasite species composition of Plasmodium infections among asymptomatic and symptomatic school-age children in rural and urban areas of Kinshasa, Democratic Republic of Congo.

J Med Entomol. 2021 Oct 07. pii: tjab167. [Epub ahead of print]

First Report of Adult Aedes aegypti (Diptera: Culicidae) Resistance to Pyrethroids in Argentina.

Laura Harburguer, Paula V Gonzalez, Eduardo Zerba.

  Severe human arboviral diseases can be transmitted by the mosquito Aedes aegypti (Linnaeus), including dengue, chikungunya, Zika, and yellow fever. Adult control using spatial sprays with adulticides is recommended only when dengue outbreaks occur. In Argentina, mainly pyrethroids, like cis-permethrin, have been used as an adulticide, especially since 2008. The evolution and spread of resistance to insecticides is a major concern for vector control. This study reports for the first time pyrethroid resistance in Ae. aegypti adults from Argentina, in the city of Salvador Mazza (Salta). WHO discriminating doses of 0.75% were used for permethrin, 0.05% for deltamethrin, and 5% for malathion. Also the discriminating dose for cis-permethrin (0.6%) was calculated and evaluated for the first time. We found a resistance ratio 50 (RR50) of 10.3 (9.7-10.4) for cis-permethrin, which is considered as high resistance. Our results also indicated resistance to deltamethrin (22.6% mortality) and permethrin (53.6% mortality), and a total susceptibility to malathion (100% mortality). Results from this study highlight the importance of the correct use of insecticides within an Integrated Vector Management (IVM) approach and of early detection of resistance to enable Ae. aegypti control in Argentina. More studies are needed to determine the spread of mosquito resistance to pyrethroids.

Keywords:  Aedes aegypti; insecticide resistance; malathion; pyrethroids

DOI:  https://doi.org/10.1093/jme/tjab167
Parasit Vectors. 2021 Oct 07. 14(1): 516

The effect of irrigation on malaria vector bionomics and transmission intensity in western Ethiopia.

Werissaw Haileselassie, Endalew Zemene, Ming-Chieh Lee, Daibin Zhong, Guofa Zhou, Behailu Taye, Alemayehu Dagne, Wakgari Deressa, James W Kazura, Guiyun Yan, Delenasaw Yewhalaw.

  BACKGROUND: Irrigation schemes may result in subsequent changes in malaria disease dynamics. Understanding the mechanisms and effects of irrigation on malaria vector bionomics and transmission intensity is essential to develop new or alternative surveillance and control strategies to reduce or control malaria risk. This study was designed to assess the effect of rice irrigation on malaria vector bionomics and transmission intensity in the Gambella Region, Ethiopia.METHODS: Comparative cross-sectional study was conducted in Abobo District of the Gambella Region, Ethiopia. Accordingly, clusters (kebeles) were classified into nearby and faraway clusters depending on their proximity to the irrigation scheme. Adult mosquito survey was conducted in February, August and November 2018 from three nearby and three faraway clusters using Centers for Disease Control and Prevention (CDC) light traps (LTs). During the November survey, human landing catch (HLC) and pyrethrum spray catch (PSC) were also conducted. The collected mosquitoes were morphologically identified to species and tested for Plasmodium infection using circumsporozoite protein enzyme-linked immunosorbent assay (CSP-ELISA). Furthermore, species-specific polymerase chain reaction (PCR) was performed to identify member species of the Anopheles gambiae complex. Chi-square and t-tests were used to analyze the data using the SPSS version 20 software package.
RESULTS: A total of 4319 female anopheline mosquitoes comprising An. gambiae sensu lato, An. funestus group, An. pharoensis, An. coustani complex and An. squamosus were collected. Overall, 84.5% and 15.5% of the anopheline mosquitoes were collected from the nearby and faraway clusters, respectively. Anopheles gambiae s.l. was the predominant (56.2%) anopheline species in the area followed by An. pharoensis (15.7%). The density of anopheline mosquitoes was significantly higher in the nearby clusters in both HLCs [t(3) = 5.14, P = 0.0143] and CDC LT catches [t(271.97) = 7.446, P < 0.0001). The overall sporozoite rate of anopheline species from the nearby clusters was 10-fold higher compared to the faraway clusters.
CONCLUSIONS: Significantly higher mosquito population density was observed in areas close to the irrigation sites. Sporozoite infection rate in the mosquito population was also markedly higher from the nearby clusters. Therefore, the irrigation scheme could increase the risk of malaria in the area.

Keywords:  Ethiopia; Irrigation; Malaria; Mosquito vectors; Transmission intensity

DOI:  https://doi.org/10.1186/s13071-021-04993-y
Trop Biomed. 2021 Sep 01. 38(3): 446-452

The determination of effective concentration of acethonilic Ipomoea cairica leaves extract against laboratory and field strains of Aedes albopictus and Aedes aegypti mosquito larvae.

R Rodzay, W F Zuharah.

Inundated with escalating dengue outbreaks, there is an urgent call to find alternate potential vector control methods as the currently employed method fails to curb the expanding of dengue virus transmission in Malaysia. Supported by this aim, we are interested in exploiting the potential of Ipomoea cairica leaves extract towards primary and secondary vectors of dengue fever, Aedes aegypti and Aedes albopictus. To assess the effectiveness of this plant extracts towards Aedes larvae, we carried out two complementary analyses. First, we observed the comparative effectiveness of larvicidal activity I. cairica extract against the laboratory and field strains of Ae. aegypti and Ae. albopictus. Then, we determined the effective lethal dose of this plant extract against Aedes larvae using log-probit regression analysis of the SPSS 20.0 programme. Results from bioassay demonstrated that I. cairica leaves extract was highly effective to induce larvicidal mortality of Ae. albopictus and Ae. aegypti within 24 and 48 hours post-treatment. Results from the factorial analysis of variance (ANOVA) also indicated that there were significant differences in larvicidal activity between species and strains used (P<0.05). It is interesting to notify that the sequence of effectiveness for the larvicidal activities of I. cairica acethonilic leaves extract is in the manner; Ae. albopictus field strain > Ae. aegypti laboratory strain > Ae. aegypti field strain > Ae. albopictus laboratory strain. The I. cairica leaves extract displayed high larvicidal activity against Ae. albopictus as compared to Ae. aegypti. This is the first evaluation involving the comparison of I. cairica leaves extract effects for the laboratory strain and field strain of Ae. albopictus and Ae. Aegypti.

DOI: https://doi.org/10.47665/tb.38.3.087
J Trop Med. 2021 ;2021 6726622

Review of Anopheles Mosquito Species, Abundance, and Distribution in Ethiopia.

Fasil Adugna, Melaku Wale, Endalkachew Nibret.

Background: Malaria is a major mosquito-borne disease in Ethiopia, and it is one of the leading causes of morbidity and mortality. Plasmodium falciparum and P. vivax are the two malaria-causing parasitic species commonly known to cause human malaria in Ethiopia. To better manage and control vectors transmitting malaria parasites, the abundance, distribution, and updated annotated list of Anopheles species present in Ethiopia are very important.Methods: In order to compile a list of the species recorded in Ethiopia, 33 original research articles were collected. This work gives an updated list of Anopheles mosquito species in Ethiopia and their abundance, distribution, and composition.
Results: According to this review, 110305 Anopheles mosquitoes were collected and 35 Anopheles species were recorded in different parts of Ethiopia. A. arabiensis was the most abundant when compared to other species, whereas A. maculipalpis and A. wilsonii were the least abundant species. The most abundant Anopheles species was recorded in central and the least abundant, from eastern Ethiopia. The second, third, and fourth abundant species were also collected from southern, northern, and western parts of Ethiopia.

DOI: https://doi.org/10.1155/2021/6726622
PLoS Negl Trop Dis. 2021 Oct 04. 15(10): e0009822

Efficacy of targeted indoor residual spraying with the pyrrole insecticide chlorfenapyr against pyrethroid-resistant Aedes aegypti.

Azael Che-Mendoza, Gabriela González-Olvera, Anuar Medina-Barreiro, Carlos Arisqueta-Chablé, Wilberth Bibiano-Marin, Fabián Correa-Morales, Oscar D Kirstein, Pablo Manrique-Saide, Gonzalo M Vazquez-Prokopec.

BACKGROUND: There is an increased need to mitigate the emergence of insecticide resistance and incorporate new formulations and modes of application to control the urban vector Aedes aegypti. Most research and development of insecticide formulations for the control of Ae. aegypti has focused on their peridomestic use as truck-mounted ULV-sprays or thermal fogs despite the widespread knowledge that most resting Ae. aegypti are found indoors. A recent modification of indoor residual spraying (IRS), termed targeted IRS (TIRS) works by restricting applications to 1.5 m down to the floor and on key Ae. aegypti resting sites (under furniture). TIRS also opens the possibility of evaluating novel residual insecticide formulations currently being developed for malaria IRS.METHODS: We evaluated the residual efficacy of chlorfenapyr, formulated as Sylando 240SC, for 12 months on free-flying field-derived pyrethroid-resistant Ae. aegypti using a novel experimental house design in Merida, Mexico. On a monthly basis, 600 female Ae. aegypti were released into the houses and left indoors with access to sugar solution for 24 hours. After the exposure period, dead and alive mosquitoes were counted in houses treated with chlorfenapyr as well as untreated control houses to calculate 24-h mortality. An evaluation for these exposed cohorts of surviving mosquitoes was extended up to seven days under laboratory conditions to quantify "delayed mortality".
RESULTS: Mean acute (24-h) mortality of pyrethroid-resistant Ae. aegypti ranged 80-97% over 5 months, dropping below 30% after 7 months post-TIRS. If delayed mortality was considered (quantifying mosquito mortality up to 7 days after exposure), residual efficacy was above 90% for up to 7 months post-TIRS application. Generalized Additive Mixed Models quantified a residual efficacy of chlorfenapyr of 225 days (ca. 7.5 months).
CONCLUSIONS: Chlorfenapyr represents a new option for TIRS control of Ae. aegypti in urban areas, providing a highly-effective time of protection against indoor Ae. aegypti females of up to 7 months.

DOI: https://doi.org/10.1371/journal.pntd.0009822
Parasit Vectors. 2021 Oct 07. 14(1): 515

Australian mosquito assemblages vary between ground and sub-canopy habitats.

Boni F Sebayang, Tanya L Russell, Kyran M Staunton, Michael Townsend, Christopher Paton, Tovi Lehmann, Thomas R Burkot.

  BACKGROUND: The surveillance and control of mosquito-borne diseases is dependent upon understanding the bionomics and distribution of the vectors. Most studies of mosquito assemblages describe species abundance, richness and composition close to the ground defined often by only one sampling method. In this study, we assessed Australian mosquito species near the ground and in the sub-canopy using two traps baited with a variety of lures.METHODS: Mosquitoes were sampled using a 4 × 4 Latin square design at the Cattana Wetlands, Australia from February to April 2020, using passive box traps with octenol and carbon dioxide and three variations of a sticky net trap (unbaited, and baited with octenol or octenol and carbon dioxide). The traps were deployed at two different heights: ground level (≤ 1 m above the ground) and sub-canopy level (6 m above the ground).
RESULTS: In total, 27 mosquito species were identified across the ground and sub-canopy levels from the different traps. The abundance of mosquitoes at the ground level was twofold greater than at the sub-canopy level. While the species richness at ground and sub-canopy levels was not significantly different, species abundance varied by the collection height.
CONCLUSIONS: The composition of mosquito population assemblages was correlated with the trap types and heights at which they were deployed. Coquillettidia species, which prefer feeding on birds, were mainly found in the sub-canopy whereas Anopheles farauti, Aedes vigilax and Mansonia uniformis, which have a preference for feeding on large mammals, were predominantly found near the ground. In addition to trap height, environmental factors and mosquito bionomic characteristics (e.g. larval habitat, resting behaviour and host blood preferences) may explain the vertical distribution of mosquitoes. This information is useful to better understand how vectors may acquire and transmit pathogens to hosts living at different heights.

Keywords:  Australian mosquitoes; Height; Mosquito traps; Vertical distribution

DOI:  https://doi.org/10.1186/s13071-021-04999-6
Proc Natl Acad Sci U S A. 2021 Oct 12. pii: e2106828118. [Epub ahead of print]118(41):

Releasing incompatible males drives strong suppression across populations of wild and Wolbachia-carrying Aedes aegypti in Australia.

Nigel W Beebe, Dan Pagendam, Brendan J Trewin, Andrew Boomer, Matt Bradford, Andrew Ford, Catherine Liddington, Artiom Bondarenco, Paul J De Barro, Joshua Gilchrist, Christopher Paton, Kyran M Staunton, Brian Johnson, Andrew J Maynard, Gregor J Devine, Leon E Hugo, Gordana Rasic, Helen Cook, Peter Massaro, Nigel Snoad, Jacob E Crawford, Bradley J White, Zhiyong Xi, Scott A Ritchie.

  Releasing sterile or incompatible male insects is a proven method of population management in agricultural systems with the potential to revolutionize mosquito control. Through a collaborative venture with the "Debug" Verily Life Sciences team, we assessed the incompatible insect technique (IIT) with the mosquito vector Aedes aegypti in northern Australia in a replicated treatment control field trial. Backcrossing a US strain of Ae. aegypti carrying Wolbachia wAlbB from Aedes albopictus with a local strain, we generated a wAlbB2-F4 strain incompatible with both the wild-type (no Wolbachia) and wMel-Wolbachia Ae. aegypti now extant in North Queensland. The wAlbB2-F4 strain was manually mass reared with males separated from females using Verily sex-sorting technologies to obtain no detectable female contamination in the field. With community consent, we delivered a total of three million IIT males into three isolated landscapes of over 200 houses each, releasing ∼50 males per house three times a week over 20 wk. Detecting initial overflooding ratios of between 5:1 and 10:1, strong population declines well beyond 80% were detected across all treatment landscapes when compared to controls. Monitoring through the following season to observe the ongoing effect saw one treatment landscape devoid of adult Ae. aegypti early in the season. A second landscape showed reduced adults, and the third recovered fully. These encouraging results in suppressing both wild-type and wMel-Ae. aegypti confirms the utility of bidirectional incompatibility in the field setting, show the IIT to be robust, and indicate that the removal of this arbovirus vector from human-occupied landscapes may be achievable.

Keywords:  Aedes aegypti; arbovirus vector; biological control; incompatible insect technology; vector control

DOI:  https://doi.org/10.1073/pnas.2106828118
Parasit Vectors. 2021 Oct 07. 14(1): 514

Wild populations of malaria vectors can mate both inside and outside human dwellings.

Ismail H Nambunga, Betwel J Msugupakulya, Emmanuel E Hape, Issa H Mshani, Najat F Kahamba, Gustav Mkandawile, Daniel M Mabula, Rukiyah M Njalambaha, Emmanuel W Kaindoa, Letus L Muyaga, Marie R G Hermy, Frederic Tripet, Heather M Ferguson, Halfan S Ngowo, Fredros O Okumu.

  BACKGROUND: Wild populations of Anopheles mosquitoes are generally thought to mate outdoors in swarms, although once colonized, they also mate readily inside laboratory cages. This study investigated whether the malaria vectors Anopheles funestus and Anopheles arabiensis can also naturally mate inside human dwellings.METHOD: Mosquitoes were sampled from three volunteer-occupied experimental huts in a rural Tanzanian village at 6:00 p.m. each evening, after which the huts were completely sealed and sampling was repeated at 11:00 p.m and 6 a.m. the next morning to compare the proportions of inseminated females. Similarly timed collections were done inside local unsealed village houses. Lastly, wild-caught larvae and pupae were introduced inside or outside experimental huts constructed inside two semi-field screened chambers. The huts were then sealed and fitted with exit traps, allowing mosquito egress but not entry. Mating was assessed in subsequent days by sampling and dissecting emergent adults caught indoors, outdoors and in exit traps.
RESULTS: Proportions of inseminated females inside the experimental huts in the village increased from approximately 60% at 6 p.m. to approximately 90% the following morning despite no new mosquitoes entering the huts after 6 p.m. Insemination in the local homes increased from approximately 78% to approximately 93% over the same time points. In the semi-field observations of wild-caught captive mosquitoes, the proportions of inseminated An. funestus were 20.9% (95% confidence interval [CI]: ± 2.8) outdoors, 25.2% (95% CI: ± 3.4) indoors and 16.8% (± 8.3) in exit traps, while the proportions of inseminated An. arabiensis were 42.3% (95% CI: ± 5.5) outdoors, 47.4% (95% CI: ± 4.7) indoors and 37.1% (CI: ± 6.8) in exit traps.
CONCLUSION: Wild populations of An. funestus and An. arabiensis in these study villages can mate both inside and outside human dwellings. Most of the mating clearly happens before the mosquitoes enter houses, but additional mating happens indoors. The ecological significance of such indoor mating remains to be determined. The observed insemination inside the experimental huts fitted with exit traps and in the unsealed village houses suggests that the indoor mating happens voluntarily even under unrestricted egress. These findings may inspire improved vector control, such as by targeting males indoors, and potentially inform alternative methods for colonizing strongly eurygamic Anopheles species (e.g. An. funestus) inside laboratories or semi-field chambers.

Keywords:  Anopheles arabiensis; Anopheles funestus; Eurygamic species; Malaria; Mosquito mating; Tanzania

DOI:  https://doi.org/10.1186/s13071-021-04989-8
PLoS Negl Trop Dis. 2021 Oct 06. 15(10): e0009827

Searching for a sign of exotic Aedes albopictus (Culicidae) introduction in major international seaports on Kyushu Island, Japan.

Chao Yang, Toshihiko Sunahara, Jinping Hu, Kyoko Futami, Hitoshi Kawada, Noboru Minakawa.

BACKGROUND: The Asian tiger mosquito, Aedes albopictus, has spread around the world. The migration was mainly mediated by maritime transportations. This species is known as an efficient vector for arboviruses, and it was responsible for the recent dengue outbreak in Tokyo, Japan. As the vector competence varies among geographical populations, and insecticide resistant populations have emerged, it is important to reveal their movements. The present study uses molecular techniques to search for a sign of introduction of an exotic population in three major international seaports on Kyushu Island.METHODOLOGY/PRINCIPAL FINDINGS: Adults of Ae. albopictus were sampled around the international seaports of Fukuoka, Kitakyushu, and Nagasaki. Pairwise fixation indexes were estimated between the sampled populations based on 13 microsatellite markers. There was no clear genetic differentiation between distant and port populations in Kitakyushu and Nagasaki. However, the analysis found one distinct group near the container terminal in Fukuoka, which handles international freight containers mainly from adjacent countries. DNA samples were also obtained from Goto, Tsushima, Honshu, Ryukyu, Thailand, and the Philippines; and a cluster analysis and discriminant analysis revealed that the distinct group in Fukuoka did not belong to these groups. Combined with the results of phylogenetic analysis based on CO1, these results implied that this group originated from one Asian temperate region outside of Japan. Neutrality test and mismatch distribution analysis suggested that the establishment of this group was not recent.
CONCLUSIONS/SIGNIFICANCE: The present study found a sign of Ae. albopictus introduction from a temperate region of Asia through maritime freight container transportation. The genetically distinct group found in Fukuoka likely originated from a temperate region outside of Japan. Maritime container transportation may introduce to Japan mosquitoes with greater vector competence/insecticide resistance. This is the first study to describe the spatial population structure of Ae. albopictus in Japan using molecular techniques.

DOI: https://doi.org/10.1371/journal.pntd.0009827
Adv Parasitol. 2021 ;pii: S0065-308X(21)00030-0. [Epub ahead of print]113 131-189

The vectors of Plasmodium knowlesi and other simian malarias Southeast Asia: challenges in malaria elimination.

Indra Vythilingam, Tock Hing Chua, Jonathan Wee Kent Liew, Benny O Manin, Heather M Ferguson.

  Plasmodium knowlesi, a simian malaria parasite of great public health concern has been reported from most countries in Southeast Asia and exported to various countries around the world. Currently P. knowlesi is the predominant species infecting humans in Malaysia. Besides this species, other simian malaria parasites such as P. cynomolgi and P. inui are also infecting humans in the region. The vectors of P. knowlesi and other Asian simian malarias belong to the Leucosphyrus Group of Anopheles mosquitoes which are generally forest dwelling species. Continual deforestation has resulted in these species moving into forest fringes, farms, plantations and human settlements along with their macaque hosts. Limited studies have shown that mosquito vectors are attracted to both humans and macaque hosts, preferring to bite outdoors and in the early part of the night. We here review the current status of simian malaria vectors and their parasites, knowledge of vector competence from experimental infections and discuss possible vector control measures. The challenges encountered in simian malaria elimination are also discussed. We highlight key knowledge gaps on vector distribution and ecology that may impede effective control strategies.

Keywords:  Bionomics; Leucosphyrus group of Anopheles; Simian malaria; Transmission; Vectors

DOI:  https://doi.org/10.1016/bs.apar.2021.08.005
Int J Infect Dis. 2021 Sep 30. pii: S1201-9712(21)00780-3. [Epub ahead of print]

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

N Pradeep Kumar, Ashwani Kumar, D Panneer, S Abidha, S Muthukumaravel, T Sankari, P M Ajithlal, Jessu Mathew, Suhana Koothradan, R Paramasivan, M Muniyaraj, Himmat Singh, Rekha Saxena, P Vijayachari, I P Sunish, A N Shriram, Prafulla Dutta, Saurav Jyoti Patgiri, D R Bhattacharyya, S L Hoti, D Chattopadhyay, Subarna Roy, Namita Mahapatra, Sanghamitra Pati, Gyan Chand, A K Mishra, Pradip Barde, P Jambulingam.

  OBJECTIVES: In wake of the Public Health Emergency of International Concern declared on ZIKA by the World Health Organization during 2016, Indian Council of Medical Research (ICMR) carried out countrywide vector surveillance for ZIKA and DENGUE viruses (ZIKV & DENV) in India, as a preparedness measure during 2016-2019.METHODS: High-risk zones distributed to 49 Districts in 14 states/ Union Territories (UT) were included in the study. Seven ICMR Institutions participated, following a uniform Standard Operating Protocol. Aedes specimens sampled on weekly intervals were processed by multiplex Reverse transcriptase PCR for ZIKV/DENV and Real-time RT-PCR of ZIKV (among few samples distributed to all Districts).
RESULTS: Altogether, 79492 Aedes specimens in 6492 pools were processed and three (0.05%) and 63 (0.97%) pools respectively were found positive for ZIKV and DENV. ZIKV infections were recorded in Aedes aegypti sampled during 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/ UTs were found infected with DENV. Besides, both sexes of Ae. albopictus were infected indicating trans-ovarial transmission.
CONCLUSION: This investigation evinced no active transmission of the "American lineage - pandemic ZIKA virus" in India during the pandemic period.

Keywords:  Aedes; India; Vector surveillance; ZIKA

DOI:  https://doi.org/10.1016/j.ijid.2021.09.074
J Med Entomol. 2021 Oct 07. pii: tjab165. [Epub ahead of print]

Detection and Establishment of Aedes notoscriptus (Diptera: Culicidae) Mosquitoes in Southern California, United States.

Marco E Metzger, J Wakoli Wekesa, Susanne Kluh, Kenn K Fujioka, Robert Saviskas, Aaron Arugay, Nathan McConnell, Kiet Nguyen, Laura Krueger, Gregory M Hacker, Renjie Hu, Vicki L Kramer.

  Aedes notoscriptus (Skuse), the Australian backyard mosquito, is a pestiferous daytime-biting species native to Australia and the surrounding southwestern Pacific region. It is suspected to play a role in the transmission of several arboviruses and is considered a competent vector of dog heartworm, Dirofilaria immitis (Leidy). This highly adaptable mosquito thrives in natural and artificial water-holding containers in both forested and urbanized areas, from tropical to temperate climates, and has benefitted from a close association with humans, increasing in abundance within its native range. It invaded and successfully established in New Zealand as well as in previously unoccupied temperate and arid regions of Australia. Ae. notoscriptus was discovered in Los Angeles County, CA, in 2014, marking the first time this species had been found outside the southwestern Pacific region. By the end of 2019, immature and adult mosquitoes had been collected from 364 unique locations within 44 cities spanning three southern California counties. The discovery, establishment, and rapid spread of this species in urban areas may signal the global movement and advent of a new invasive container-inhabiting species. The biting nuisance, public health, and veterinary health implications associated with the invasion of southern California by this mosquito are discussed.

Keywords:   Aedes notoscriptus ; Dirofilaria immitis ; Australian backyard mosquito; California; arbovirus

DOI:  https://doi.org/10.1093/jme/tjab165
Parasit Vectors. 2021 Oct 07. 14(1): 518

Chemical composition and the insecticidal activity of Aeollanthus pubescens leaf essential oil against Anopheles gambiae sensu stricto.

Roméo Barnabé Bohounton, Luc Salako Djogbénou, Oswald Yédjinnavênan Djihinto, Oronce Sedjro-Ludolphe Dedome, Pierre Marie Sovegnon, Bruno Barea, Aristide Adomou, Pierre Villeneuve, Fidèle Paul Tchobo.

  BACKGROUND: The excessive use of synthetic insecticides is responsible for many cases of resistance in insects. Therefore, the use of natural molecules of ecological interest with insecticidal properties is an alternative approach to the use of synthetic insecticides. The aim of this study is to investigating the larvicidal and adulticidal activity and the chemical composition of the essential oil of Aeollanthus pubescens on the major malaria vector, Anopheles gambiae.METHODS: Three reference strains of Anopheles gambiae sensu stricto (Kisumu, Kiskdr and Acerkis) were used in this study. The leaves of A. pubescens were collected in southern Benin. The standard World Health Organisation (WHO) guidelines for larvicide evaluation were used, and the chemical composition of the essential oil was analysed by gas chromatography coupled to mass spectrometry. Adult mosquitoes of each strain were exposed to pieces of net coated with the essential oil for 3 min using the WHO cone bioassay method. Probit regression analysis was used to determine the concentrations that would kill 50 and 95% of each test population (LC50, LC95) and the knockdown time for 50 and 95% of each test population (KDT50, and KDT95). The difference between the mortality-dose regressions for the different strains was analysed using the likelihood ratio test (LRT). The log-rank test was performed to evaluate the difference in survival between the strains.
RESULTS: A total of 14 components were identified, accounting for 98.3% of total oil content. The major components were carvacrol (51.1%), thymyle acetate (14.0%) and ɣ-terpinene (10.6%). The essential oil showed larvicidal properties on the Kisumu, Acerkis and Kiskdr strains, with LC50 of 29.6, 22.9 and 28.4 ppm, respectively. With pieces of netting treated at 165 µg/cm2, the KDT50 of both Acerkis (1.71 s; Z = 3.34, P < 0.001) and Kiskdr (2.67 s; Z = 3.49, P < 0.001) individuals were significantly lower than that of Kisumu (3.8 s). The lifespan of the three mosquito strains decreased to 1 day for Kisumu (χ2 = 99, df = 1, P < 0.001), 2 days for Acerkis (χ2 = 117, df = 1, P < 0.001) and 3 days for Kiskdr (χ2 = 96.9, df = 1, P < 0.001).
CONCLUSION: Our findings show that A. pubescens essential oil has larvicide and adulticide properties against the malaria vector An. gambiae sensu stricto, suggesting that this essential oil may be a potential candidate for the control of the resistant malaria-transmitting vectors.

Keywords:  Aeollanthus pubescens; Anopheles gambiae; Bioinsecticidal activity; Essential oil

DOI:  https://doi.org/10.1186/s13071-021-05012-w
Arch Virol. 2021 Oct 08.

Genetic characterization of chikungunya virus isolates from Aedes aegypti mosquitoes collected during a recent outbreak in Bangkok, Thailand.

Proawpilart Intayot, Atchara Phumee, Kanyarat Kraivichian, Sriwatapron Sor-Suwan, Rungfar Boonserm, Padet Siriyasatien.

Chikungunya virus (CHIKV) is a mosquito-borne emerging pathogen that is transmitted to humans through the bite of female Aedes mosquitoes. CHIKV infection has become a major public health concern worldwide, as it has a significant impact on the healthcare system. Since 2004, the virus has emerged in Africa and subsequently spread to countries located near the Indian Ocean, including India, and to Europe, the Americas, and Asia. In Thailand, a large CHIKV outbreak occurred during 2008-2009 and was caused by a virus originating from the east/central/south African (ECSA) CHIKV genotype. Since then, the ECSA genotype of CHIKV has continued to circulate and has caused sporadic cases in different areas in Thailand. Approximately 20,000 reported cases have been confirmed by the Bureau of Epidemiology, Ministry of Public Health, Thailand, from January 1, 2018 to July 31, 2020. However, the causes of this CHIKV re-emergence remain unclear. To obtain a better understanding of CHIKV circulation during the recent outbreak in Bangkok, Thailand, complete genome analysis of CHIKV isolates from field-caught mosquitoes collected in outbreak areas was performed. A total of 28 Ae. aegypti samples (21 females and 7 males) were collected, and individual mosquitoes were used for CHIKV detection and isolation. Eleven of 28 (39.29%) female and three of 28 (10.71%) male mosquitoes were positive for CHIKV by E1 nested RT-PCR. Four CHIKV isolates were successfully isolated from four female Ae. aegypti mosquitoes. Based on complete genome analysis, several amino acid substitutions were identified in the protein coding region. The E1:K211E and E2:V264A mutations in the background of the E1:226A mutation were observed in all four CHIKV isolates. An important observation was the presence of one amino acid substitution, leading to an E1:K245R change. This mutation was found in all four CHIKV isolates from mosquitoes in this study and in Thai patients described previously. Additionally, phylogenetic analysis indicated that the four CHIKV isolates belonged to the Indian Ocean clade of the ECSA genotype. The results obtained in this study provide detailed information on the molecular characteristics and evolution of currently circulating CHIKV strains in Thailand, which are useful for developing prevention and control strategies.

DOI: https://doi.org/10.1007/s00705-021-05243-3
PLoS Negl Trop Dis. 2021 Oct;15(10): e0009761

Interaction of climate and socio-ecological environment drives the dengue outbreak in epidemic region of China.

Chenlu Li, Xiaoxu Wu, Scott Sheridan, Jay Lee, Xiaofeng Wang, Jie Yin, Jiatong Han.

Transmission of dengue virus is a complex process with interactions between virus, mosquitoes and humans, influenced by multiple factors simultaneously. Studies have examined the impact of climate or socio-ecological factors on dengue, or only analyzed the individual effects of each single factor on dengue transmission. However, little research has addressed the interactive effects by multiple factors on dengue incidence. This study uses the geographical detector method to investigate the interactive effect of climate and socio-ecological factors on dengue incidence from two perspectives: over a long-time series and during outbreak periods; and surmised on the possibility of dengue outbreaks in the future. Results suggest that the temperature plays a dominant role in the long-time series of dengue transmission, while socio-ecological factors have great explanatory power for dengue outbreaks. The interactive effect of any two factors is greater than the impact of single factor on dengue transmission, and the interactions of pairs of climate and socio-ecological factors have more significant impact on dengue. Increasing temperature and surge in travel could cause dengue outbreaks in the future. Based on these results, three recommendations are offered regarding the prevention of dengue outbreaks: mitigating the urban heat island effect, adjusting the time and frequency of vector control intervention, and providing targeted health education to travelers at the border points. This study hopes to provide meaningful clues and a scientific basis for policymakers regarding effective interventions against dengue transmission, even during outbreaks.

DOI: https://doi.org/10.1371/journal.pntd.0009761
Evol Appl. 2021 Sep;14(9): 2244-2257

Gene flow between island populations of the malaria mosquito, Anopheles hinesorum, may have contributed to the spread of divergent host preference phenotypes.

Luke Ambrose, Daniel Ortiz-Barrientos, Robert D Cooper, Neil F Lobo, Thomas R Burkot, Tanya L Russell, Nigel W Beebe.

  Anopheles hinesorum is a mosquito species with variable host preference. Throughout New Guinea and northern Australia, An. hinesorum feeds on humans (it is opportunistically anthropophagic) while in the south-west Pacific's Solomon Archipelago, the species is abundant but has rarely been found biting humans (it is exclusively zoophagic in most populations). There are at least two divergent zoophagic (nonhuman biting) mitochondrial lineages of An. hinesorum in the Solomon Archipelago representing two independent dispersals. Since zoophagy is a derived (nonancestral) trait in this species, this leads to the question: has zoophagy evolved independently in these two populations? Or conversely: has nuclear gene flow or connectivity resulted in the transfer of zoophagy? Although we cannot conclusively answer this, we find close nuclear relationships between Solomon Archipelago populations indicating that recent nuclear gene flow has occurred between zoophagic populations from the divergent mitochondrial lineages. Recent work on isolated islands of the Western Province (Solomon Archipelago) has also revealed an anomalous, anthropophagic island population of An. hinesorum. We find a common shared mitochondrial haplotype between this Solomon Island population and another anthropophagic population from New Guinea. This finding suggests that there has been recent migration from New Guinea into the only known anthropophagic population from the Solomon Islands. Although currently localized to a few islands in the Western Province of the Solomon Archipelago, if anthropophagy presents a selective advantage, we may see An. hinesorum emerge as a new malaria vector in a region that is now working on malaria elimination.

Keywords:  gene flow; host preference evolution; island colonization; malaria; population genetics‐empirical

DOI:  https://doi.org/10.1111/eva.13288
Theor Biol Med Model. 2021 Oct 03. 18(1): 17

Analysis of international traveler mobility patterns in Tokyo to identify geographic foci of dengue fever risk.

Baoyin Yuan, Hyojung Lee, Hiroshi Nishiura.

  Travelers play a role in triggering epidemics of imported dengue fever because they can carry the virus to other countries during the incubation period. If a traveler carrying dengue virus visits open green space and is bitten by mosquitoes, a local outbreak can ensue. In the present study, we aimed to understand the movement patterns of international travelers in Tokyo using mobile phone data, with the goal of identifying geographical foci of dengue transmission. We analyzed datasets based on mobile phone access to WiFi systems and measured the spatial distribution of international visitors in Tokyo on two specific dates (one weekday in July 2017 and another weekday in August 2017). Mobile phone users were classified by nationality into three groups according to risk of dengue transmission. Sixteen national parks were selected based on their involvement in a 2014 dengue outbreak and abundance of Aedes mosquitoes. We found that not all national parks were visited by international travelers and that visits to cemeteries were very infrequent. We also found that travelers from countries with high dengue prevalence were less likely to visit national parks compared with travelers from dengue-free countries. Travelers from countries with sporadic dengue cases and countries with regional transmission tended to visit common destinations. By contrast, the travel footprints of visitors from countries with continuous dengue transmission were focused on non-green spaces. Entomological surveillance in Tokyo has been restricted to national parks since the 2014 dengue outbreak. However, our results indicate that areas subject to surveillance should include both public and private green spaces near tourist sites.

Keywords:  Coherence; Dengue; Imported case; Sightseeing; Tourism; Transmission

DOI:  https://doi.org/10.1186/s12976-021-00149-8
Adv Parasitol. 2021 ;pii: S0065-308X(21)00031-2. [Epub ahead of print]113 225-286

Epidemiology of the zoonotic malaria Plasmodium knowlesi in changing landscapes.

Pablo Ruiz Cuenca, Stephanie Key, Amaziasizamoria Jumail, Henry Surendra, Heather M Ferguson, Chris J Drakeley, Kimberly Fornace.

  Within the past two decades, incidence of human cases of the zoonotic malaria Plasmodium knowlesi has increased markedly. P. knowlesi is now the most common cause of human malaria in Malaysia and threatens to undermine malaria control programmes across Southeast Asia. The emergence of zoonotic malaria corresponds to a period of rapid deforestation within this region. These environmental changes impact the distribution and behaviour of the simian hosts, mosquito vector species and human populations, creating new opportunities for P. knowlesi transmission. Here, we review how landscape changes can drive zoonotic disease emergence, examine the extent and causes of these changes across Southeast and identify how these mechanisms may be impacting P. knowlesi dynamics. We review the current spatial epidemiology of reported P. knowlesi infections in people and assess how these demographic and environmental changes may lead to changes in transmission patterns. Finally, we identify opportunities to improve P. knowlesi surveillance and develop targeted ecological interventions within these landscapes.

Keywords:  Deforestation; Emerging diseases; Land use change; Plasmodium knowlesi; Spatial epidemiology

DOI:  https://doi.org/10.1016/bs.apar.2021.08.006
Evol Appl. 2021 Sep;14(9): 2147-2161

Selection of sites for field trials of genetically engineered mosquitoes with gene drive.

Gregory C Lanzaro, Melina Campos, Marc Crepeau, Anthony Cornel, Abram Estrada, Hans Gripkey, Ziad Haddad, Ana Kormos, Steven Palomares.

  Novel malaria control strategies using genetically engineered mosquitoes (GEMs) are on the horizon. Population modification is one approach wherein mosquitoes are engineered with genes rendering them refractory to the malaria parasite, Plasmodium falciparum, coupled with a low-threshold, Cas9-based gene drive. When released into a wild vector population, GEMs preferentially transmit these parasite-blocking genes to their offspring, ultimately modifying a vector population into a nonvector one. Deploying this technology awaits ecologically contained field trial evaluations. Here, we consider a process for site selection, the first critical step in designing a trial. Our goal is to identify a site that maximizes prospects for success, minimizes risk, and serves as a fair, valid, and convincing test of efficacy and impacts of a GEM product intended for large-scale deployment in Africa. We base site selection on geographic, geological, and biological, rather than social or legal, criteria. We recognize the latter as critically important but not as a first step in selecting a site. We propose physical islands as being the best candidates for a GEM field trial and present an evaluation of 22 African islands. We consider geographic and genetic isolation, biological complexity, island size, and topography and identify two island groups that satisfy key criteria for ideal GEM field trial sites.

Keywords:  Anopheles gambiae; genetic control; islands; malaria; population modification

DOI:  https://doi.org/10.1111/eva.13283
PLoS Med. 2021 Oct;18(10): e1003799

The global burden of Plasmodium vivax malaria is obscure and insidious.

Katherine E Battle, J Kevin Baird.

J. Kevin Baird and colleagues, examine and discuss the estimated global burden of vivax malaria and it's biological, clinical, and public health complexity.

DOI: https://doi.org/10.1371/journal.pmed.1003799
Pathog Glob Health. 2021 Oct 08. 1-2

West Nile virus in Italy: the reports of its disappearance were greatly exaggerated.

Matteo Riccò.



Keywords:  Italy; West Nile neuro-invasive disease; West Nile virus; epidemiology; vector-borne disease

DOI:  https://doi.org/10.1080/20477724.2021.1989187
PLoS Negl Trop Dis. 2021 Oct;15(10): e0009778

Dengue outbreaks in the COVID-19 era: Alarm raised for Asia.

Xinting Lu, Hilary Bambrick, Puntani Pongsumpun, Pandji Wibawa Dhewantara, Do Thi Thanh Toan, Wenbiao Hu.

DOI: https://doi.org/10.1371/journal.pntd.0009778
Malar J. 2021 Oct 02. 20(1): 389

Malaria parasite species composition of Plasmodium infections among asymptomatic and symptomatic school-age children in rural and urban areas of Kinshasa, Democratic Republic of Congo.

Sabin S Nundu, Richard Culleton, Shirley V Simpson, Hiroaki Arima, Jean-Jacques Muyembe, Toshihiro Mita, Steve Ahuka, Taro Yamamoto.

  BACKGROUND: Malaria remains a major public health concern in the Democratic Republic of Congo (DRC), and school-age children are relatively neglected in malaria prevalence surveys and may constitute a significant reservoir of transmission. This study aimed to understand the burden of malaria infections in school-age children in Kinshasa/DRC.METHODS: A total of 634 (427 asymptomatic and 207 symptomatic) blood samples collected from school-age children aged 6 to 14 years were analysed by microscopy, RDT and Nested-PCR.
RESULTS: The overall prevalence of Plasmodium spp. by microscopy, RDT and PCR was 33%, 42% and 62% among asymptomatic children and 59%, 64% and 95% in symptomatic children, respectively. The prevalence of Plasmodium falciparum, Plasmodium malariae and Plasmodium ovale spp. by PCR was 58%, 20% and 11% among asymptomatic and 93%, 13% and 16% in symptomatic children, respectively. Among P. ovale spp., P. ovale curtisi, P. ovale wallikeri and mixed P. ovale curtisi + P. ovale wallikeri accounted for 75%, 24% and 1% of infections, respectively. All Plasmodium species infections were significantly more prevalent in the rural area compared to the urban area in asymptomatic infections (p < 0.001). Living in a rural as opposed to an urban area was associated with a five-fold greater risk of asymptomatic malaria parasite carriage (p < 0.001). Amongst asymptomatic malaria parasite carriers, 43% and 16% of children harboured mixed Plasmodium with P. falciparum infections in the rural and the urban areas, respectively, whereas in symptomatic malaria infections, it was 22% and 26%, respectively. Few children carried single infections of P. malariae (2.2%) and P. ovale spp. (1.9%).
CONCLUSION: School-age children are at significant risk from both asymptomatic and symptomatic malaria infections. Continuous systematic screening and treatment of school-age children in high-transmission settings is needed.

Keywords:  Democratic Republic Congo; Malaria; Plasmodium; School-age children

DOI:  https://doi.org/10.1186/s12936-021-03919-4