bims-mosdis 2021-10-03 papers

bims-mosdis

Biomed News

on Mosquito distribution and disease

Issue of 2021‒10‒03
sixteen papers selected by
Richard Halfpenny
Staffordshire University

Insecticide resistance in Aedes aegypti from Tapachula, Mexico: Spatial variation and response to historical insecticide use.
Preliminary Report of the Insecticide Susceptibility Status of Aedes Albopictus in Bangladesh.
Aedes Mosquito Distribution along a Transect from Rural to Urban Settings in Yaoundé, Cameroon.
Aedes aegypti in the Mediterranean container ports at the time of climate change: A time bomb on the mosquito vector map of Europe.
Protective effect of house-screening against indoor Aedes aegypti in Mérida, Mexico: a cluster randomized controlled trial.
Effects of Selection to Diflubenzuron and Bacillus thuringiensis Var. Israelensis on the Overwintering Successes of Aedes albopictus (Diptera: Culicidae).
A Framework for Weather-Driven Dengue Virus Transmission Dynamics in Different Brazilian Regions.
"Mosquito-Free Villages": Practice, Exploration, and Prospects of Sustainable Mosquito Control - Zhejiang, China.
Updated distribution of anopheline mosquitoes in Hokkaido, Japan, and the first evidence of Anopheles belenrae in Japan.
Analysis of the spatial distribution of Aedes albopictus in an urban area of Shanghai, China.
Pyrethroid and Etofenprox Resistance in Anopheles gambiae and Anopheles coluzzii from Vegetable Farms in Yaoundé, Cameroon: Dynamics, Intensity and Molecular Basis.
Nonrandom Selection and Multiple Blood Feeding of Human Hosts by Anopheles Vectors: Implications for Malaria Transmission in Papua New Guinea.
An Outbreak of Dengue Virus Type 1 - Jiangxi Province, China, 2019.
Autoregressive spatial modeling of possible cases of dengue, chikungunya, and Zika in the capital of Northeastern Brazil.
Estimating the annual dengue force of infection from the age of reporting primary infections across urban centres in endemic countries.
Incidence of Zika Virus Infection from a Dengue Epidemiological Study of Children in Ratchaburi Province, Thailand.

PLoS Negl Trop Dis. 2021 Sep;15(9): e0009746

Insecticide resistance in Aedes aegypti from Tapachula, Mexico: Spatial variation and response to historical insecticide use.

Francisco Solis-Santoyo, Americo D Rodriguez, R Patricia Penilla-Navarro, Daniel Sanchez, Alfredo Castillo-Vera, Alma D Lopez-Solis, Eduardo D Vazquez-Lopez, Saul Lozano, William C Black, Karla Saavedra-Rodriguez.

BACKGROUND: Insecticide use continues as the main strategy to control Aedes aegypti, the vector of dengue, Zika, chikungunya, and yellow fever. In the city of Tapachula, Mexico, mosquito control programs switched from pyrethroids to organophosphates for outdoor spatial spraying in 2013. Additionally, the spraying scheme switched from total coverage to focused control, prioritizing areas with higher entomological-virological risk. Five years after this strategy had been implemented, we evaluated the status and variability of insecticide resistance among Ae. aegypti collected at 26 sites in Tapachula.METHODOLOGY/PRINCIPAL FINDINGS: We determined the lethal concentrations at 50% of the tested populations (LC50) using a bottle bioassay, and then, we calculated the resistance ratio (RR) relative to the susceptible New Orleans strain. Permethrin and deltamethrin (pyrethroids), chlorpyrifos and malathion (organophosphates), and bendiocarb (carbamate) were tested. The frequencies of the substitutions V1016I and F1534C, which are in the voltage-gated sodium channel and confer knockdown-resistance (kdr) to pyrethroid insecticides, were calculated. Despite 5 years having passed since the removal of pyrethroids from the control programs, Ae. aegypti remained highly resistant to permethrin and deltamethrin (RR > 10-fold). In addition, following 5 years of chlorpyrifos use, mosquitoes at 15 of 26 sites showed moderate resistance to chlorpyrifos (5- to 10-fold), and the mosquitoes from one site were highly resistant. All sites had low resistance to malathion (< 5-fold). Resistance to bendiocarb was low at 19 sites, moderate at five, and high at two. Frequencies of the V1016I ranged from 0.16-0.71, while C1534 approached fixation at 23 sites (0.8-1). Resistance profiles and kdr allele frequencies varied across Tapachula. The variability was not associated with a spatial pattern at the scale of the sampling.
CONCLUSION/SIGNIFICANCE: Mosquito populations respond to selection pressure at a focal scale in the field. Spatial variation across sites highlights the importance of testing multiple sites within geographical regions.

DOI: https://doi.org/10.1371/journal.pntd.0009746
Am J Trop Med Hyg. 2021 Sep 27. pii: tpmd210454. [Epub ahead of print]

Preliminary Report of the Insecticide Susceptibility Status of Aedes Albopictus in Bangladesh.

Hasan Mohammad Al-Amin, Seth Irish, Audrey Lenhart, Mohammad Shafiul Alam.

Aedes albopictus is a highly invasive mosquito species and a vector of human arboviral diseases including dengue, chikungunya, and Zika. There are no effective drugs or vaccines for the treatment or prevention of most of these diseases, so the primary option for disease prevention and control is to target mosquitoes, often using insecticides. Despite vector control efforts, cases of arboviral diseases are increasing in Bangladesh and it is important to understand if this escalation is associated with the presence of insecticide resistance in Aedes populations, including Ae. albopictus. The CDC bottle bioassays performed on Ae. albopictus from two districts in Bangladesh detected resistance to permethrin but susceptibility to deltamethrin, malathion, and bendiocarb. The detection of permethrin resistance is worrisome, since arbovirus vector control strategies in Bangladesh currently include the use of permethrin. Routine monitoring of the susceptibility status of key vector populations in Bangladesh will allow a better understanding of resistance trends, enabling the strengthening of control strategies.

DOI: https://doi.org/10.4269/ajtmh.21-0454
Insects. 2021 Sep 12. pii: 819. [Epub ahead of print]12(9):

Aedes Mosquito Distribution along a Transect from Rural to Urban Settings in Yaoundé, Cameroon.

Borel Djiappi-Tchamen, Mariette Stella Nana-Ndjangwo, Timoléon Tchuinkam, Idene Makoudjou, Elysée Nchoutpouen, Edmond Kopya, Abdou Talipouo, Roland Bamou, Marie Paul Audrey Mayi, Parfait Awono-Ambene, Charles Wondji, Christophe Antonio-Nkondjio.

  INTRODUCTION: The surveillance of mosquito vectors is important for the control of arboviruses diseases worldwide. Detailed information on the bionomics and distribution of their main vectors, Aedes aegypti and Aedes albopictus, is essential for assessing disease transmission risk and for better planning of control interventions.METHODS: Entomological surveys were carried out from November 2019 to November 2020 in six localities of Yaoundé city following a transect from urban to rural settings: two urban (Obili, Mvan), two peri-urban (Simbock, Ahala) and two rural areas (Lendom, Elig-essomballa)-during rainy and dry seasons. All water containers were inspected. Aedes mosquito abundance, species distribution and seasonal distribution patterns were compared using generalized linear models. Stegomyia indexes were estimated to determine the risk of arbovirus transmission.
RESULTS: A total of 6332 mosquitoes larvae were collected (2342 in urban areas, 1694 in peri-urban areas and 2296 in rural sites). Aedes species recorded included Ae. albopictus, Ae. aegytpi, Ae. simpsoni and Aedes spp. High mosquito abundance was registered in the rainy season (4706) compared to the dry season (1626) (p < 0.0001). Ae. albopictus was the most abundant Aedes species in urban (96.89%) and peri-urban (95.09%) sites whereas Ae. aegypti was more prevalent in rural sites (68.56%) (p < 0.0001). Both species were found together in 71 larval habitats. Ae. albopictus was mostly found in discarded tires (42.51%), whereas Ae. aegypti was more prevalent in plastic containers used for storing water (65.87%). The majority of Aedes mosquitoes' breeding places were situated close to human dwellings (0-10 m).
CONCLUSION: Uncontrolled urbanization seems to greatly favour the presence of Aedes mosquito species around human dwellings in Yaoundé. Controlling Aedes mosquito distribution is becoming urgent to reduce the risk of arbovirus outbreaks in the city of Yaoundé.

Keywords:  Aedes aegypti; Aedes albopictus; Cameroon; Yaoundé; breeding site; peri-urban; rural; urban

DOI:  https://doi.org/10.3390/insects12090819
Heliyon. 2021 Sep;7(9): e07981

Aedes aegypti in the Mediterranean container ports at the time of climate change: A time bomb on the mosquito vector map of Europe.

Attila J Trájer.

  In the past, Aedes aegypti was present in Southern Europe. Although the mosquito was eradicated from the Mediterranean region, its regional ecotype survived the second half of the 20th century in the eastern Black Sea area. The aim of the study was to model the changes in the altering climatic suitability, ontogenetic development time and the survival rate of Aedes aegypti from first-stage larvae to adulthood in Southern Europe. The modelled present climatic suitability patterns of the mosquito show that large areas of the lower altitude Mediterranean regions, including the coastal areas of the Balkan Peninsula, South France, and large regions of the Apennines and the Iberian Peninsulas could be suitable for Ae. aegypti. The future (2041-2060 and 2061-2080) projections predict the potential northward shift of the northern occurrence of the species in the circum-Mediterranean and Black Sea areas. Both, the potential development time, and survival rate of Ae. aegypti in the late 19th and the early 20th century could be like in the present times along the Mediterranean coast. The current climatic conditions cannot explain the absence of the mosquito in wide areas of the Mediterranean and sub-Mediterranean ecoregions. The future models predict the notable increase in the development time and survival rate of the mosquito in the southern and central regions of Europe. In general, the container ports of the Alboran, Balearic, and Aegean seas seem to be the most suitable sites for the re-colonization of the mosquito, and such northern parts of the Mediterranean Sea like the Gulf of Lion, the Ligurian, and Adriatic Seas are in less extent.

Keywords:  Climate change; Development time; Ecological forecasting; Mosquito-borne diseases; Survival rate

DOI:  https://doi.org/10.1016/j.heliyon.2021.e07981
Trop Med Int Health. 2021 Sep 29.

Protective effect of house-screening against indoor Aedes aegypti in Mérida, Mexico: a cluster randomized controlled trial.

P Manrique-Saide, J Herrera-Bojórquez, J Villegas-Chim, H Puerta-Guardo, G Ayora-Talavera, M Parra-Cardeña, A Medina-Barreiro, M Ramírez-Medina, A Chi-Ku, E Trujillo-Peña, R E Méndez-Vales, H Delfín-González, M E Toledo-Romaní, R Bazzani, E Bolio-Arceo, H Gómez-Dantés, A Che-Mendoza, N Pavía-Ruz, Oscar D Kirstein, G M Vazquez-Prokopec.

  OBJECTIVE: To evaluate the protective effect of house-screening (HS) on indoor Ae. aegypti infestation, abundance and arboviral infection in Merida, Mexico.METHODS: In 2019, we performed a cluster randomized controlled trial (6 control and 6 intervention areas: 100 households/area). Intervention clusters received permanently fixed fiberglass HS on all windows and doors. The study included two cross-sectional entomologic surveys, one baseline (dry season in May 2019) and one post-intervention (PI, rainy season between September-October 2019). The presence and number of indoor Aedes females and blood-fed females (indoor mosquito infestation) as well as arboviral infections with dengue (DENV) and Zika (ZIKV) viruses were evaluated in a subsample of 30 houses within each cluster.
RESULTS: HS houses had significatively lower risk for having Aedes aegypti female mosquitoes (odds ratio [OR]=0.56, 95% C. I. 0.33-0.97, P=0.04) and blood-fed females (OR=0.53, 95% C. I. 0.28-0.97, P=0.04) than unscreened households from the control arm. Compared to control houses, HS houses had significantly lower indoor Ae. aegypti abundance (rate ratio [RR]=0.50, 95% C. I. 0.30-0.83, P=0.01), blood-fed Ae. aegypti females (RR=0.48, 95% C. I. 0.27-0.85, P=0.01) and female Ae. aegypti positive for arboviruses (OR=0.29, 95% CI 0.10-0.86, P=0.02). The estimated intervention efficacy in reducing Ae. aegypti arbovirus infection was 71%.
CONCLUSIONS: These results provide evidence supporting the use of HS as an effective pesticide-free method to control house infestations with Aedes aegypti and reduce the transmission of Aedes-transmitted viruses such as DENV, chikungunya (CHIKV), and ZIKV.

Keywords:   Aedes aegypti ; Aedes-transmitted viruses; House-screening; Merida; arboviruses

DOI:  https://doi.org/10.1111/tmi.13680
Insects. 2021 Sep 13. pii: 822. [Epub ahead of print]12(9):

Effects of Selection to Diflubenzuron and Bacillus thuringiensis Var. Israelensis on the Overwintering Successes of Aedes albopictus (Diptera: Culicidae).

Charalampos S Ioannou, Christos Hadjichristodoulou, Varvara A Mouchtouri, Nikos T Papadopoulos.

  Aedes albopictus is an invasive mosquito species responsible for local transmission of chikungunya and dengue viruses in Europe. In the absence of available treatments, insecticides-based control remains one of the most important viable strategies to prevent emerging problems. Diflubenzuron (DFB) and Bacillus thuringiensis var. israelensis (Bti) are among the most commonly used larvicides for Ae. albopictus control with consequent concerns for the potential development of resistance. Studies on the resistance emergence in Ae. albopictus and its persistence in the wild to both DFB and Bti are essential for the efficient and sustainable planning of the control programmes. In this context, larvae from a recently laboratory established population were subjected to increasing selective pressure for nine successive generations using both DFB and Bti. The resistance levels and the overwintering success of the selected populations relative to control (colonies that received no selection) were determined. Results revealed an 8.5- and 1.6-fold increase on the resistance levels following selection with DFB and Bti, respectively. The selection process to both larvicides had no apparent impacts on the overwintering capability relative to control, suggesting the successful persistence of the selected individuals in the wild on an annual base.

Keywords:  Asian tiger mosquito; eggs diapause; insecticides efficacy; mosquito control

DOI:  https://doi.org/10.3390/insects12090822
Int J Environ Res Public Health. 2021 Sep 09. pii: 9493. [Epub ahead of print]18(18):

A Framework for Weather-Driven Dengue Virus Transmission Dynamics in Different Brazilian Regions.

Leon Diniz Alves, Raquel Martins Lana, Flávio Codeço Coelho.

  This study investigated a model to assess the role of climate fluctuations on dengue (DENV) dynamics from 2010 to 2019 in four Brazilian municipalities. The proposed transmission model was based on a preexisting SEI-SIR model, but also incorporates the vector vertical transmission and the vector's egg compartment, thus allowing rainfall to be introduced to modulate egg-hatching. Temperature and rainfall satellite data throughout the decade were used as climatic model inputs. A sensitivity analysis was performed to understand the role of each parameter. The model-simulated scenario was compared to the observed dengue incidence and the findings indicate that the model was able to capture the observed seasonal dengue incidence pattern with good accuracy until 2016, although higher deviations were observed from 2016 to 2019. The results further demonstrate that vertical transmission fluctuations can affect attack transmission rates and patterns, suggesting the need to investigate the contribution of vertical transmission to dengue transmission dynamics in future assessments. The improved understanding of the relationship between different environment variables and dengue transmission achieved by the proposed model can contribute to public health policies regarding mosquito-borne diseases.

Keywords:  Aedes aegypti; dengue; environment variables; transmission model; tropical diseases

DOI:  https://doi.org/10.3390/ijerph18189493
China CDC Wkly. 2019 Dec;1(5): 70-74

"Mosquito-Free Villages": Practice, Exploration, and Prospects of Sustainable Mosquito Control - Zhejiang, China.

Song Guo, Wenzhong Huang, Jimin Sun, Zhenyu Gong, Feng Ling, Hongzhao Wu, Enfu Chen.

Mosquitoes and mosquito-borne diseases have always been a great threat to human health. Mosquito control based on sustainable vector management strategy is particularly important. In Zhejiang Province, exemplary villages of sustainable mosquito control ("mosquito-free villages") have been successful operated, providing a new model of mosquito control in rural areas based on local conditions. The construction of "mosquito-free village" will apply environmentally-friendly and appropriate technologies to eliminate and transform mosquito breeding sites and to establish mechanisms of cultivating villagers' health literacy of scientific mosquito control and voluntary participation in control activities to keep mosquito density low long-term.
Parasit Vectors. 2021 Sep 26. 14(1): 494

Updated distribution of anopheline mosquitoes in Hokkaido, Japan, and the first evidence of Anopheles belenrae in Japan.

Kyoko Sawabe, Nozomi Imanishi-Kobayashi, Yoshihide Maekawa, Yukiko Higa, Kyeong Soon Kim, Keita Hoshino, Yoshio Tsuda, Toshihiko Hayashi, Naoko Nihei, Kenji Takai, Takeshi Kurihara, Mutsuo Kobayashi.

  BACKGROUND: In Hokkaido, northern island of Japan, at least seven cases of falciparum malaria were reported by 1951. A survey conducted at that time was unsuccessful in implicating any mosquito species as the possible vector. Although active anopheline mosquito surveillance continued until the middle of the 1980s, there is very limited information on their current status and distribution in Japan. Therefore, this study is an update on the current status and distribution of anopheline mosquitoes in Hokkaido based on a 15-year entomological surveillance between 2001 and 2015.METHODS: A survey of mosquitoes was conducted at 22 sites in Hokkaido, Japan, from 2001 to 2015. Adult mosquitoes were collected from cowsheds, lakesides, shrubs, and habitats ranging from open grassland to coniferous forest using a Centers for Disease Control and Prevention (CDC) miniature light trap enhanced with dry ice, aspirators, and sweeping nets. Larvae were collected from lakes, ponds, swamps, stagnant and flowing rivers, and paddy fields. All specimens were morphologically identified and subjected to polymerase chain reaction (PCR)-based sequence analysis of the internal transcribed spacer 2 ( ITS2) region of rDNA. Phylogenetic trees were reconstructed using the neighbor-joining method with the Kimura 2-parameter model on MEGA X version 10.2.2.
RESULTS: A total of 46 anopheline specimens were used for the phylogenetic analysis. During the survey, a new member of the Anopheles hyrcanus group, An. belenrae, was discovered in eastern Hokkaido in 2004. Anopheles belenrae has since then been consistently found and confirmed to inhabit only this area of Japan. Four members of the An. hyrcanus group, namely An. belenrae, An. engarensis, An. lesteri, and An. sineroides, have been found in Hokkaido. The results also suggest that An. sinensis, formerly a dominant species throughout Japan, has become a rarely found species, at least currently in Hokkaido.
CONCLUSION: The updated distribution of anopheline mosquitoes in Hokkaido, Japan, showed considerable differences from that observed in previous surveys conducted from 1969 to 1984. In particular, areas where An. sinensis was previously distributed may have been greatly reduced in Hokkaido. The phylogenetic analysis revealed a novel An. hyrcanus group member identified as An. belenrae, described in South Korea in 2005. It is interesting that An. belenrae was confirmed to inhabit only eastern Hokkaido, Japan.

Keywords:  Anopheles hyrcanus group mosquitoes; Hokkaido Japan; ITS2 sequence

DOI:  https://doi.org/10.1186/s13071-021-04995-w
Parasit Vectors. 2021 Sep 26. 14(1): 501

Analysis of the spatial distribution of Aedes albopictus in an urban area of Shanghai, China.

Yibin Zhou, Hongxia Liu, Peien Leng, Jiang Zhu, Shenjun Yao, Yiyi Zhu, Huanyu Wu.

  BACKGROUND: Aedes albopictus is a vector of major arboviral diseases and a primary pest in tropical and temperate regions of China. In most cities of China, the current monitoring system for the spread of Ae. albopictus is based on the subdistrict scale and does not consider spatial distribution for analysis of species density. Thus, the system is not sufficiently accurate for epidemic investigations, especially in large cities.METHODS: This study used an improved surveillance program, with the mosquito oviposition trap (MOT) method, integrating the actual monitoring locations to investigate the temporal and spatial distribution of Ae. albopictus abundance in an urban area of Shanghai, China from 2018 to 2019. A total of 133 monitoring units were selected for surveillance of Ae. albopictus density in the study area, which was composed of 14 subdistricts. The vector abundance and spatial structure of Ae. albopictus were predicted using a binomial areal kriging model based on eight MOTs in each unit. Results were compared to the light trap (LT) method of the traditional monitoring scheme.
RESULTS: A total of 8,192 MOTs were placed in the study area in 2018, and 7917 (96.6%) were retrieved, with a positive rate of 6.45%. In 2019, 22,715 (97.0%) of 23,408 MOTs were recovered, with a positive rate of 5.44%. Using the LT method, 273 (93.5%) and 312 (94.5%) adult female Ae. albopictus were gathered in 2018 and 2019, respectively. The Ae. albopictus populations increased slowly from May, reached a peak in July, and declined gradually from September. The MOT positivity index (MPI) showed significant positive spatial autocorrelation across the study area, whereas LT collections indicated a nonsignificant spatial autocorrelation. The MPI was suitable for spatial interpolation using the binomial areal kriging model and showed different hot spots in different years.
CONCLUSIONS: The improved surveillance system integrated with a geographical information system (GIS) can improve our understanding of the spatial and temporal distribution of Ae. albopictus in urban areas and provide a practical method for decision-makers to implement vector control and mosquito management.

Keywords:  Aedes albopictus; Binomial areal kriging model; Mosquito oviposition trap; Spatial distribution

DOI:  https://doi.org/10.1186/s13071-021-05022-8
Molecules. 2021 Sep 13. pii: 5543. [Epub ahead of print]26(18):

Pyrethroid and Etofenprox Resistance in Anopheles gambiae and Anopheles coluzzii from Vegetable Farms in Yaoundé, Cameroon: Dynamics, Intensity and Molecular Basis.

Michael Piameu, Philippe Nwane, Wilson Toussile, Konstantinos Mavridis, Nadja Christina Wipf, Paraudie France Kouadio, Lili Ranaise Mbakop, Stanislas Mandeng, Wolfgang Eyisap Ekoko, Jean Claude Toto, Kelly Lionelle Ngaffo, Petronile Klorane Ngo Etounde, Arthur Titcho Ngantchou, Mouhamadou Chouaibou, Pie Müller, Parfait Awono-Ambene, John Vontas, Josiane Etang.

  Previous studies have indicated widespread insecticide resistance in malaria vector populations from Cameroon. However, the intensity of this resistance and underlying mechanisms are poorly known. Therefore, we conducted three cross-sectional resistance surveys between April 2018 and October 2019, using the revised World Health Organization protocol, which includes resistance incidences and intensity assessments. Field-collected Anopheles gambiae s.l. populations from Nkolondom, Nkolbisson and Ekié vegetable farms in the city of Yaoundé were tested with deltamethrin, permethrin, alpha-cypermethrin and etofenprox, using 1× insecticide diagnostic concentrations for resistance incidence, then 5× and 10× concentrations for resistance intensity. Subsamples were analyzed for species identification and the detection of resistance-associated molecular markers using TaqMan® qPCR assays. In Nkolbisson, both An. coluzzii (96%) and An. gambiae s.s. (4%) were found together, whereas only An. gambiae s.s. was present in Nkolondom, and only An. coluzzii was present in Ekié. All three populations were resistant to the four insecticides (<75% mortality rates-MR1×), with intensity generally fluctuating over the time between mod-erate (<98%-MR5×; ≥98%-MR10×) and high (76-97%-MR10×). The kdr L995F, L995S, and N1570Y, and the Ace-1 G280S-resistant alleles were found in An. gambiae from Nkolondom, at 73%, 1%, 16% and 13% frequencies, respectively, whereas only the kdr L995F was found in An. gambiae s.s. from Nkolbisson at a 50% frequency. In An. coluzzii from Nkolbisson and Ekié, we detected only the kdr L995F allele at 65% and 60% frequencies, respectively. Furthermore, expression levels of Cyp6m2, Cyp9k1, and Gste2 metabolic genes were highly upregulated (over fivefold) in Nkolondom and Nkolbisson. Pyrethroid and etofenprox-based vector control interventions may be jeopardized in the prospected areas, due to high resistance intensity, with multiple mechanisms in An. gambiae s.s. and An. coluzzii.

Keywords:  Anopheles coluzzii; Anopheles gambiae; Cameroon; insecticides; malaria; resistance intensity; urban areas; vector control

DOI:  https://doi.org/10.3390/molecules26185543
Am J Trop Med Hyg. 2021 Sep 27. pii: tpmd210210. [Epub ahead of print]

Nonrandom Selection and Multiple Blood Feeding of Human Hosts by Anopheles Vectors: Implications for Malaria Transmission in Papua New Guinea.

John B Keven, Michelle Katusele, Rebecca Vinit, Daniela Rodríguez-Rodríguez, Manuel W Hetzel, Leanne J Robinson, Moses Laman, Stephan Karl, David R Foran, Edward D Walker.

Nonrandom selection and multiple blood feeding of human hosts by Anopheles mosquitoes may exacerbate malaria transmission. Both patterns of blood feeding and their relationship to malaria epidemiology were investigated in Anopheles vectors in Papua New Guinea (PNG). Blood samples from humans and mosquito blood meals were collected in villages and human genetic profiles ("fingerprints") were analyzed by genotyping 23 microsatellites and a sex-specific marker. Frequency of blood meals acquired from different humans, identified by unique genetic profiles, was fitted to Poisson and negative binomial distributions to test for nonrandom patterns of host selection. Blood meals with more than one genetic profiles were classified as mosquitoes that fed on multiple humans. The age of a person bitten by a mosquito was determined by matching the blood-meal genetic profile to the villagers' genetic profiles. Malaria infection in humans was determined by PCR test of blood samples. The results show nonrandom distribution of blood feeding among humans, with biased selection toward males and individuals aged 15-30 years. Prevalence of Plasmodium falciparum infection was higher in this age group, suggesting males in this age range could be super-spreaders of malaria parasites. The proportion of mosquitoes that fed on multiple humans ranged from 6% to 13% among villages. The patterns of host utilization observed here can amplify transmission and contribute to the persistence of malaria in PNG despite efforts to suppress it with insecticidal bed nets. Excessive feeding on males aged 15-30 years underscores the importance of targeted interventions focusing on this demographic group.

DOI: https://doi.org/10.4269/ajtmh.21-0210
China CDC Wkly. 2020 Aug 28. 2(35): 684-687

An Outbreak of Dengue Virus Type 1 - Jiangxi Province, China, 2019.

Fuqiang Yang, Guanghui Xia, Zhili Zeng, Zhongjian Li, Huijian Cheng, Daping Che, Jun Zong, Jianxiong Li, Tian Gong, Guihua Liu, Weidong Zhou, Bihai Wei, Xiaobo Liu, Jiandong Li, Sheng Ding.

What is known about this topic? Dengue fever is an acute febrile illness caused by four types of dengue virus (DENV 1-4), and is a mosquito-borne infectious disease. The incidence of dengue has increased dramatically around the world in recent decades. An estimated of 3.9 billion people in 128 countries are at risk of infection with dengue viruses, 70% of whom are in Asia. In 2017, the first local infections of dengue virus (DENV-2) in Jiangxi Province was reported in Zhanggong District, Ganzhou City.
What is added by this report?
From August to September 2019, the first dengue outbreak happened in Xin'gan County, where 81 local dengue fever cases were reported, 35 were laboratory-confirmed cases, and 46 were clinically-diagnosed cases; all cases were dengue virus type 1. The DENV-virus strains isolated from the cases of Xin'gan County were close to the strains isolated in Singapore (MF033254|25657|Singapore|2016) and Henan (MK905537|Henan201903|China: Henan Province|2019).
What are the implications for public health practice?
The outbreak might have been caused by imported cases or covert infections. The outbreak in Xin'gan County indicated that more proactive countermeasures should be taken during the dengue epidemic period such as intensifying surveillance for dengue cases, virus serotype, and Aedes vector density and strengthening cooperation with customs and tourism departments. Moreover, the outbreak should prompt training in medical institutions and improved ability for doctor's to diagnose dengue fever, which is very important for early detection of dengue cases and taking preventive measures.

DOI: https://doi.org/10.46234/ccdcw2020.138
Rev Soc Bras Med Trop. 2021 ;pii: S0037-86822021000100336. [Epub ahead of print]54 e0223

Autoregressive spatial modeling of possible cases of dengue, chikungunya, and Zika in the capital of Northeastern Brazil.

Silmery da Silva Brito Costa, Maria Dos Remédios Freitas Carvalho Branco, Vitor Vieira Vasconcelos, Rejane Christine de Sousa Queiroz, Adriana Soraya Araujo, Ana Patrícia Barros Câmara, Angela Terumi Fushita, Maria do Socorro da Silva, Antônio Augusto Moura da Silva, Alcione Miranda Dos Santos.

INTRODUCTION: Dengue, chikungunya, and Zika are a growing global health problem. This study analyzed the spatial distribution of dengue, chikungunya, and Zika cases in São Luís, Maranhão, from 2015 to 2016 and investigated the association between socio-environmental and economic factors and hotspots for mosquito proliferation.METHODS: This was a socio-ecological study using data from the National Information System of Notifiable Diseases. The spatial units of analysis were census tracts. The incidence rates of the combined cases of the three diseases were calculated and smoothed using empirical local Bayes estimates. The spatial autocorrelation of the smoothed incidence rate was measured using Local Moran's I and Global Moran's I. Multiple linear regression and spatial autoregressive models were fitted using the log of the smoothed disease incidence rate as the dependent variable and socio-environmental factors, demographics, and mosquito hotspots as independent variables.
RESULTS: The findings showed a significant spatial autocorrelation of the smoothed incidence rate. The model that best fit the data was the spatial lag model, revealing a positive association between disease incidence and the proportion of households with surrounding garbage accumulation.
CONCLUSIONS: The distribution of dengue, chikungunya, and Zika cases showed a significant spatial pattern, in which the high-risk areas for the three diseases were explained by the variable "garbage accumulated in the surrounding environment," demonstrating the need for an intersectoral approach for vector control and prevention that goes beyond health actions.

DOI: https://doi.org/10.1590/0037-8682-0223-2021
BMC Med. 2021 Sep 30. 19(1): 217

Estimating the annual dengue force of infection from the age of reporting primary infections across urban centres in endemic countries.

Joseph R Biggs, Ava Kristy Sy, Katharine Sherratt, Oliver J Brady, Adam J Kucharski, Sebastian Funk, Mary Anne Joy Reyes, Mary Ann Quinones, William Jones-Warner, Ferchito L Avelino, Nemia L Sucaldito, Amado O Tandoc, Eva Cutiongco-de la Paz, Maria Rosario Z Capeding, Carmencita D Padilla, Julius Clemence R Hafalla, Martin L Hibberd.

  BACKGROUND: Stratifying dengue risk within endemic countries is crucial for allocating limited control interventions. Current methods of monitoring dengue transmission intensity rely on potentially inaccurate incidence estimates. We investigated whether incidence or alternate metrics obtained from standard, or laboratory, surveillance operations represent accurate surrogate indicators of the burden of dengue and can be used to monitor the force of infection (FOI) across urban centres.METHODS: Among those who reported and resided in 13 cities across the Philippines, we collected epidemiological data from all dengue case reports between 2014 and 2017 (N 80,043) and additional laboratory data from a cross-section of sampled case reports (N 11,906) between 2014 and 2018. At the city level, we estimated the aggregated annual FOI from age-accumulated IgG among the non-dengue reporting population using catalytic modelling. We compared city-aggregated FOI estimates to aggregated incidence and the mean age of clinically and laboratory diagnosed dengue cases using Pearson's Correlation coefficient and generated predicted FOI estimates using regression modelling.
RESULTS: We observed spatial heterogeneity in the dengue average annual FOI across sampled cities, ranging from 0.054 [0.036-0.081] to 0.249 [0.223-0.279]. Compared to FOI estimates, the mean age of primary dengue infections had the strongest association (ρ -0.848, p value<0.001) followed by the mean age of those reporting with warning signs (ρ -0.642, p value 0.018). Using regression modelling, we estimated the predicted annual dengue FOI across urban centres from the age of those reporting with primary infections and revealed prominent spatio-temporal heterogeneity in transmission intensity.
CONCLUSIONS: We show the mean age of those reporting with their first dengue infection or those reporting with warning signs of dengue represent superior indicators of the dengue FOI compared to crude incidence across urban centres. Our work provides a framework for national dengue surveillance to routinely monitor transmission and target control interventions to populations most in need.

Keywords:  Dengue; Flavivirus; Philippines; Primary; Serology; Surveillance

DOI:  https://doi.org/10.1186/s12916-021-02101-6
Viruses. 2021 Sep 10. pii: 1802. [Epub ahead of print]13(9):

Incidence of Zika Virus Infection from a Dengue Epidemiological Study of Children in Ratchaburi Province, Thailand.

Pimolpachr Sriburin, Pichamon Sittikul, Nathamon Kosoltanapiwat, Salin Sirinam, Watcharee Arunsodsai, Chukiat Sirivichayakul, Kriengsak Limkittikul, Supawat Chatchen.

  Zika virus (ZIKV) is the mosquito-transmitted virus that the WHO declared a Public Health Emergency of International Concern in 2016 due to the consequence of microcephaly from infected pregnancies. The incidence of Zika infection has been unclear in many countries because most infected people have nonspecific febrile illnesses. This study's aim is to investigate the incidence of symptomatic Zika virus infections from the archived samples of a dengue cohort study of children in central Thailand from 2006 to 2009. We performed Zika NS1 immunoglobulin (Ig)G enzyme-linked immunosorbent assay (ELISA) screening to identify symptomatic Zika infections in paired acute/convalescent serum samples. Symptomatic Zika infections were confirmed by reverse transcription polymerase chain reactions (RT-PCR) of acute serum samples. The comparison of the Zika NS1 IgG ELISA results between acute and convalescent samples showed 290/955 (30.4%) seropositive cases. Zika RT-PCR results were positive in 28 febrile cases (15 females, 13 males). Zika RT-PCR showed that symptomatic Zika infection occurred in children aged 4-11 years in Ratchaburi province, Thailand (2007-2009, first case in April 2007), and the symptomatic Zika:dengue infection ratio was 28 Zika:394 dengue (1:14). Phylogenetic analysis showed that all Zika viruses were of Asian lineage. Zika NS1 IgG ELISA identified Zika-infected patients and showed a low Zika:dengue ratio.

Keywords:  ELISA; RT-PCR; Thailand; Zika virus; incidence; symptomatic infection

DOI:  https://doi.org/10.3390/v13091802