bims-mosdis 2021-12-05 papers

bims-mosdis

Biomed News

on Mosquito distribution and disease

Issue of 2021‒12‒05
seventeen papers selected by
Richard Halfpenny
Staffordshire University

Starvation at the larval stage increases the vector competence of Aedes aegypti females for Zika virus.
Impacts of fungal entomopathogens on survival and immune responses of Aedes albopictus and Culex pipiens mosquitoes in the context of native Wolbachia infections.
Citizen science for monitoring the spatial and temporal dynamics of malaria vectors in relation to environmental risk factors in Ruhuha, Rwanda.
Entomological investigation of an outbreak of Japanese encephalitis in Solan district, Himachal Pradesh.
Spawning behavior of Aedini (Diptera: Culicidae) in a remnant of Atlantic Forest in the state of Rio de Janeiro.
Indoor environmental factors and house structures affect vaporization of active ingredient from spatial repellent devices placed in typical rural houses in south eastern Malawi.
Analysis of chemical compositions and larvicidal activity of nut extracts from Areca catechu Linn against Aedes (Diptera: Culicidae).
Revisiting dengue virus-mosquito interactions: molecular insights into viral fitness.
Marked reduction in antibiotic usage following intensive malaria control in a cohort of Ugandan children.
Standing Water and Missing Data: The Murky Relationship between Flooding and Mosquito-Borne Diseases.
Chikungunya virus infection: molecular biology, clinical characteristics, and epidemiology in Asian countries.
Impact of the introduction of chikungunya and zika viruses on the incidence of dengue in endemic zones of Mexico.
Recent dengue virus infection: epidemiological survey on risk factors associated with infection in a medium-sized city in Mato Grosso.
Low parasite connectivity among three malaria hotspots in Thailand.
Evidence of Chikungunya virus seroprevalence in Myanmar among dengue-suspected patients and healthy volunteers in 2013, 2015, and 2018.
Autochthonous West Nile virus infection in Germany: Increasing numbers and a rare encephalitis case in a kidney transplant recipient.
Dengue during the COVID-19 pandemic.

PLoS Negl Trop Dis. 2021 Nov 29. 15(11): e0010003

Starvation at the larval stage increases the vector competence of Aedes aegypti females for Zika virus.

Christie S Herd, DeAna G Grant, Jingyi Lin, Alexander W E Franz.

Aedes aegypti is the primary vector of Zika virus (ZIKV), a flavivirus which typically presents itself as febrile-like symptoms in humans but can also cause neurological and pregnancy complications. The transmission cycle of mosquito-borne arboviruses such as ZIKV requires that various key tissues in the female mosquito including the salivary glands get productively infected with the virus before the mosquito can transmit the virus to another vertebrate host. Following ingestion of a viremic blood-meal from a vertebrate, ZIKV initially infects the midgut epithelium before exiting the midgut after blood-meal digestion to disseminate to secondary tissues including the salivary glands. Here we investigated whether smaller Ae. aegypti females resulting from food deprivation as larvae exhibited an altered vector competence for blood-meal acquired ZIKV relative to larger mosquitoes. Midguts from small 'Starve' and large 'Control' Ae. aegypti were dissected to visualize by transmission electron microscopy (TEM) the midgut basal lamina (BL) as physical evidence for the midgut escape barrier showing Starve mosquitoes with a significantly thinner midgut BL than Control mosquitoes at two timepoints. ZIKV replication was inhibited in Starve mosquitoes following intrathoracic injection of virus, however, Starve mosquitoes exhibited a significantly higher midgut escape and population dissemination rate at 9 days post-infection (dpi) via blood-meal, with more virus present in saliva and head tissue than Control by 10 dpi and 14 dpi, respectively. These results indicate that Ae. aegypti developing under stressful conditions potentially exhibit higher midgut infection and dissemination rates for ZIKV as adults, Thus, variation in food intake as larvae is potentially a source for variable vector competence levels of the emerged adults for the virus.

DOI: https://doi.org/10.1371/journal.pntd.0010003
PLoS Negl Trop Dis. 2021 Nov 29. 15(11): e0009984

Impacts of fungal entomopathogens on survival and immune responses of Aedes albopictus and Culex pipiens mosquitoes in the context of native Wolbachia infections.

Jose L Ramirez, Molly K Schumacher, Geoff Ower, Debra E Palmquist, Steven A Juliano.

Microbial control of mosquitoes via the use of symbiotic or pathogenic microbes, such as Wolbachia and entomopathogenic fungi, are promising alternatives to synthetic insecticides to tackle the rapid increase in insecticide resistance and vector-borne disease outbreaks. This study evaluated the susceptibility and host responses of two important mosquito vectors, Ae. albopictus and Cx. pipiens, that naturally carry Wolbachia, to infections by entomopathogenic fungi. Our study indicated that while Wolbachia presence did not provide a protective advantage against entomopathogenic fungal infection, it nevertheless influenced the bacterial / fungal load and the expression of select anti-microbial effectors and phenoloxidase cascade genes in mosquitoes. Furthermore, although host responses from Ae. albopictus and Cx. pipiens were mostly similar, we observed contrasting phenotypes with regards to susceptibility and immune responses to fungal entomopathogenic infection in these two mosquitoes. This study provides new insights into the intricate multipartite interaction between the mosquito host, its native symbiont and pathogenic microbes that might be employed to control mosquito populations.

DOI: https://doi.org/10.1371/journal.pntd.0009984
Malar J. 2021 Dec 03. 20(1): 453

Citizen science for monitoring the spatial and temporal dynamics of malaria vectors in relation to environmental risk factors in Ruhuha, Rwanda.

Marilyn Milumbu Murindahabi, Arash Hoseni, L C Corné Vreugdenhil, Arnold J H van Vliet, Jackie Umupfasoni, Alphonse Mutabazi, Emmanuel Hakizimana, P Marijn Poortvliet, Leon Mutesa, Willem Takken, Constantianus J M Koenraadt.

  BACKGROUND: As part of malaria prevention and control efforts, the distribution and density of malaria mosquitoes requires continuous monitoring. Resources for long-term surveillance of malaria vectors, however, are often limited. The aim of the research was to evaluate the value of citizen science in providing insight into potential malaria vector hotspots and other malaria relevant information, and to determine predictors of malaria vector abundance in a region where routine mosquito monitoring has not been established to support vector surveillance.METHODS: A 1-year citizen science programme for malaria mosquito surveillance was implemented in five villages of the Ruhuha sector in Bugesera district, Rwanda. In total, 112 volunteer citizens were enrolled and reported monthly data on mosquitoes collected in their peridomestic environment using handmade carbon-dioxide baited traps. Additionally, they reported mosquito nuisance experienced as well as the number of confirmed malaria cases in their household.
RESULTS: In total, 3793 female mosquitoes were collected, of which 10.8% were anophelines. For the entire period, 16% of the volunteers reported having at least one confirmed malaria case per month, but this varied by village and month. During the study year 66% of the households reported at least one malaria case. From a sector perspective, a higher mosquito and malaria vector abundance was observed in the two villages in the south of the study area. The findings revealed significant positive correlations among nuisance reported and confirmed malaria cases, and also between total number of Culicidae and confirmed malaria cases, but not between the numbers of the malaria vector Anopheles gambiae and malaria cases. At the sector level, of thirteen geographical risk factors considered for inclusion in multiple regression, distance to the river network and elevation played a role in explaining mosquito and malaria mosquito abundance.
CONCLUSIONS: The study demonstrates that a citizen science approach can contribute to mosquito monitoring, and can help to identify areas that, in view of limited resources for control, are at higher risk of malaria.

Keywords:  Citizen science; Environmental risk factors; Malaria; Perceived mosquito nuisance; Rwanda

DOI:  https://doi.org/10.1186/s12936-021-03989-4
J Vector Borne Dis. 2020 Oct-Dec;57(4):57(4): 301-306

Entomological investigation of an outbreak of Japanese encephalitis in Solan district, Himachal Pradesh.

Gaurav Kumar, Shweta Pasi, V P Ojha, Ramesh C Dhiman.

  An outbreak of Japanese encephalitis (JE) was reported in Solan district of Himachal Pradesh, India in May 2018 wherein a total of eight JE cases were reported by the state health department, of which seven cases were confirmed by ELISA. An entomological survey was carried out to investigate the presence of vector mosquitoes in the affected area. Field visits were undertaken in eight villages of two blocks in Solan district. Larval collections were made from the major aquatic sites and emerging mosquito species were identified. Seepage water ditches were the main source of JE vector mosquitoes Culex tritaeniorhynchus and Cx. bitaeniorhynchus. During hand catch collections of adult mosquitoes, three vector species of JE,Culex tritaeniorhynchus (Man Hour Density 1-14), Cx. vishnui (MHD 2) and Cx. bitaeniorhynchus (MHD 1-2) were collected. A few specimens of Cx. tritaeniorhynchus (6 no.) were also collected in light trap collections. Since this was the first reported outbreak of JE from Himachal Pradesh, India, studies on sero-surveillance in addition to bionomics of JE vectors are required for better understanding of epidemiology of JE in Himachal Pradesh. Moreover, there is a need to study the role of climate change especially rising temperature in the context of JE in Himachal Pradesh.

Keywords:  Culex mosquitoes; Japanese encephalitis; breeding habitats; climate change

DOI:  https://doi.org/10.4103/0972-9062.313972
Parasit Vectors. 2021 Nov 27. 14(1): 591

Spawning behavior of Aedini (Diptera: Culicidae) in a remnant of Atlantic Forest in the state of Rio de Janeiro.

Amanda Queiroz Bastos, Paulo José Leite, Jacenir Reis Dos Santos-Mallet, Cecilia Ferreira de Mello, Michele Serdeiro, Júlia Santos Dos Silva, Ronaldo Figueiró, Tatiana Docile, Jeronimo Alencar.

  BACKGROUND: Mosquito assemblages are organized along an ecological gradient, including small habitats where interspecific competition predominates and large permanent habitats where predation predominates. This study aimed to analyze the oviposition behavior of mosquitoes regarding the preference for traps installed at two different heights with regard to ground level and the tendency to share spawning sites in an Atlantic Forest fragment in Nova Iguaçu, State of Rio de Janeiro, Brazil.METHODS: The eggs were collected from April 2018 to March 2019. Twelve ovitraps were used, randomly distributed in trees at ground level and at a height of 3 m in a forest environment.
RESULTS: They were sequentially numbered, monitored, and replaced every 2 weeks. Among the 5818 eggs collected, 3941 hatched, 3756 reached the pupa stage, and 2370 reached the adult stage. The most abundant species were Aedes albopictus (63%) and Haemagogus leucocelaenus (35%), followed by Aedes terrens (2%) and Haemagogus janthinomys (1%). Analyses showed a significant difference of (P = 0.02) between the number of mosquito species collected in the palettes at ground level and the number collected at the height of 3 m. Cluster analysis of species abundance showed that the eggs collected in the palettes at ground level were more abundant than those collected in the palettes at the height of 3 m. We detected co-occurrence of species in the oviposition palettes; according to the null model, such species distribution was not random.
CONCLUSIONS: The exploitation of oviposition sites by mosquito species can represent an event forced by population density facilitated by the ecological valence of individuals of one species. Understanding the aggregate distribution of larvae at the oviposition site allows us to conduct more in-depth studies of the oviposition behavior of female mosquitoes.

Keywords:  Coexistence; Mosquitoes; Natural environment; Oviposition biology

DOI:  https://doi.org/10.1186/s13071-021-05102-9
Jpn J Infect Dis. 2021 Nov 30.

Indoor environmental factors and house structures affect vaporization of active ingredient from spatial repellent devices placed in typical rural houses in south eastern Malawi.

Hitoshi Kawada, Shusuke Nakazawa, Kazunori Ohashi, Eggrey Aisha Kambewa, Dylo Foster Pemba.

  The use of a metofluthrin-impregnated spatial repellent device (MSRD) is a new, practically effective method for preventing mosquito blood feeding. Indoor environmental factors such as room temperature and ventilation rate are thought to be important for MSRD activity. Measurements of room temperature and vaporization of metofluthrin from MSRD in typical rural metal-roof houses and thatched-roof houses in southeastern Malawi were conducted. The relationship between house structure and number of collected Anopheline mosquitoes with and without MSRD treatment was also investigated. The difference between daytime room temperature and nighttime room temperature was significantly higher in metal-roof houses than thatched-roof houses. The vaporization of metofluthrin from the MSRD was not accelerated by the high room temperature, but by the high indoor air flow by ventilation. The number of mosquito collections was significantly higher in thatched-roof houses than in metal-roof houses. MSRD-treated thatched-roof houses have a higher probability of mosquito infestation, but the vaporization of metofluthrin is also higher due to indoor air flow, resulting in a reduction in mosquito numbers. Metal-roof houses with closed eaves reduce the probability of mosquito invasion, and a longer predicted effectiveness occurs with MSRD because of the controlled release of metofluthrin through lower indoor air flow.

Keywords:  Anopheles; House structure; Malawi; metofluthrin; temperature

DOI:  https://doi.org/10.7883/yoken.JJID.2021.584
PLoS One. 2021 ;16(11): e0260281

Analysis of chemical compositions and larvicidal activity of nut extracts from Areca catechu Linn against Aedes (Diptera: Culicidae).

Madhuri Bharathithasan, Darvin R Ravindran, Dinesh Rajendran, Sim Ka Chun, S A Abbas, Sandheep Sugathan, Zary Shariman Yahaya, Abd Rahman Said, Wen-Da Oh, Vijay Kotra, Allan Mathews, Mohamad Faiz Mohd Amin, Intan H Ishak, Rajiv Ravi.

BACKGROUND: There is a growing need to use green alternative larvicidal control for Aedes larvae compared to chemical insecticides. Substantial reliance on chemical insecticides caused insecticide resistance in mosquito populations. Thus, research for alternate chemical compounds from natural products is necessary to control Aedes larvae. This study explores the analysis of chemical compositions from Areca catechu nut as a potential larvicide for Aedes (Diptera: Culicidae).METHODS: The Areca catechu nut collected from Ipoh, Perak, Malaysia was grounded into powder and used for Soxhlet extraction. The chemical analysis of the extracts and their structures were identified using the GCMS-QP2010 Ultra (Shimadzu) system. National Institute of Standards and Technology (NIST) Chemistry WebBook, Standard Reference Database 69 (https://webbook.nist.gov/chemistry/) and PubChem (https://pubchem.ncbi.nlm.nih.gov/), the two databases used to retrieve the synonyms, molecular formula, molecular weight, and 2-dimensional (2D) structure of chemical compounds. Next, following WHO procedures for larval bioassays, the extracts were used to asses larvicidal activity against early 4th instar larvae of Aedes aegypti and Aedes albopictus.
RESULTS: The larvicidal activities were observed against early 4th stage larvae with different concentrations in the range from 200 mg/L to 1600 mg/L. The LC50 and LC95 of Aedes aegypti were 621 mg/L and 2264 mg/L respectively; whereas the LC50 and LC95 of Aedes albopictus were 636 mg/L and 2268 mg/L respectively. Mortality was not observed in the non-target organism test. The analysis using gas chromatography and mass spectrometer recovered several chemical compounds such as Arecaidine, Dodecanoic acid, Methyl tetradecanoate, Tetradecanoic acid <n->, and n-Hexadecanoic acid bioactive components. These chemical constituents were used as additive formulations in pesticides, pest control, insect repellent, and insecticidal agents.
CONCLUSIONS: Our study showed significant outcomes from the extract of Areca catechu nut and it deserves further investigation in relation to chemical components and larvicidal actions between different species of Aedes mosquitoes. Even though all these findings are fundamental, it may have some interesting potentials to be developed as natural bio-larvicidal products.

DOI: https://doi.org/10.1371/journal.pone.0260281
J Gen Virol. 2021 Nov;102(11):

Revisiting dengue virus-mosquito interactions: molecular insights into viral fitness.

Tanamas Siriphanitchakorn, R Manjunatha Kini, Eng Eong Ooi, Milly M Choy.

  Dengue virus (DENV), like other viruses, closely interacts with the host cell machinery to complete its life cycle. Over the course of infection, DENV interacts with several host factors with pro-viral activities to support its infection. Meanwhile, it has to evade or counteract host factors with anti-viral activities which inhibit its infection. These molecular virus-host interactions play a crucial role in determining the success of DENV infection. Deciphering such interactions is thus paramount to understanding viral fitness in its natural hosts. While DENV-mammalian host interactions have been extensively studied, not much has been done to characterize DENV-mosquito host interactions despite its importance in controlling DENV transmission. Here, to provide a snapshot of our current understanding of DENV-mosquito interactions, we review the literature that identified host factors and cellular processes related to DENV infection in its mosquito vectors, Aedes aegypti and Aedes albopictus, with a particular focus on DENV-mosquito omics studies. This knowledge provides fundamental insights into the DENV life cycle, and could contribute to the development of novel antiviral strategies.

Keywords:  dengue virus; mosquitoes; viral fitness; virus-host interactions

DOI:  https://doi.org/10.1099/jgv.0.001693
BMC Med. 2021 Nov 30. 19(1): 294

Marked reduction in antibiotic usage following intensive malaria control in a cohort of Ugandan children.

Paul J Krezanoski, Michelle E Roh, John Rek, Joaniter I Nankabirwa, Emmanuel Arinaitwe, Sarah G Staedke, Susan Nayiga, Michelle S Hsiang, David Smith, Moses Kamya, Grant Dorsey.

  BACKGROUND: Intensive malaria control may have additional benefits beyond reducing the incidence of symptomatic malaria. We compared antibiotic treatment of children before and after the implementation of highly effective malaria control interventions in Tororo, a historically high transmission area of Uganda.METHODS: Two successive cohorts of children, aged 0.5 to 10 years, were followed from September 2011 to October 2019 in a dedicated study clinic. Universal distribution of long-lasting insecticidal nets was conducted in 2013 and 2017. Sustained indoor residual spraying of insecticide (IRS) was initiated in December 2014. Generalized linear mixed-effects models were used to compare the incidence of antimalarial and antibiotic treatments before and after vector control measures were implemented.
RESULTS: Comparing the period prior to the implementation of IRS to the period after IRS had been sustained for 4-5 years, the adjusted incidence of malaria treatments decreased from 2.68 to 0.05 per person-year (incidence rate ratio [IRR] = 0.02, 95% CI 0.01-0.03, p < 0.001), and the adjusted incidence of antibiotic treatments decreased from 4.14 to 1.26 per person-year (IRR = 0.30, 95% CI 0.27-0.34, p < 0.001). The reduction in antibiotic usage was primarily associated with fewer episodes of symptomatic malaria and fewer episodes of fever with sub-microscopic parasitemia, both of which were frequently treated with antibiotics.
CONCLUSIONS: In a historically high transmission setting, the implementation of highly effective vector control interventions was followed by a marked reduction in antibiotic treatment of children. This added benefit of malaria control could have important implications for antibiotic prescribing practices, efforts to curtail antimicrobial resistance, and health system costs.

Keywords:  Antibiotic prescriptions; Antibiotic usage; Malaria; Malaria control; Pediatric infectious diseases; Pediatrics; Prevention

DOI:  https://doi.org/10.1186/s12916-021-02167-2
Environ Health Perspect. 2021 Dec;129(12): 124001

Standing Water and Missing Data: The Murky Relationship between Flooding and Mosquito-Borne Diseases.

Nate Seltenrich.

DOI: https://doi.org/10.1289/EHP10382
J Biomed Sci. 2021 Dec 02. 28(1): 84

Chikungunya virus infection: molecular biology, clinical characteristics, and epidemiology in Asian countries.

Sarawut Khongwichit, Jira Chansaenroj, Chintana Chirathaworn, Yong Poovorawan.

  Chikungunya virus (CHIKV) is a re-emerging mosquito-borne human pathogen that causes chikungunya fever, which is typically accompanied by severe joint pain. In Asia, serological evidence indicated that CHIKV first emerged in 1954. From the 1950's to 2005, sporadic CHIKV infections were attributed to the Asian genotype. However, the massive outbreak of CHIKV in India and the Southwest Indian Ocean Islands in 2005 has since raised chikungunya as a worldwide public health concern. The virus is spreading globally, but mostly in tropical and subtropical regions, particularly in South and Southeast Asia. The emergence of the CHIKV East/Central/South African genotype-Indian Ocean lineage (ECSA-IOL) has caused large outbreaks in South and Southeast Asia affected more than a million people over a decade. Notably, the massive CHIKV outbreaks before 2016 and the more recent outbreak in Asia were driven by distinct ECSA lineages. The first significant CHIKV ECSA strains harbored the Aedes albopictus-adaptive mutation E1: A226V. More recently, another mass CHIKV ECSA outbreak in Asia started in India and spread beyond South and Southeast Asia to Kenya and Italy. This virus lacked the E1: A226V mutation but instead harbored two novel mutations (E1: K211E and E2: V264A) in an E1: 226A background, which enhanced its fitness in Aedes aegypti. The emergence of a novel ECSA strain may lead to a more widespread geographical distribution of CHIKV in the future. This review summarizes the current CHIKV situation in Asian countries and provides a general overview of the molecular virology, disease manifestation, diagnosis, prevalence, genotype distribution, evolutionary relationships, and epidemiology of CHIKV infection in Asian countries over the past 65 years. This knowledge is essential in guiding the epidemiological study, control, prevention of future CHIKV outbreaks, and the development of new vaccines and antivirals targeting CHIKV.

Keywords:  Asia; Chikungunya virus; E1: K211E and E2: V264A; Novel ECSA; Outbreak

DOI:  https://doi.org/10.1186/s12929-021-00778-8
PLoS Negl Trop Dis. 2021 Dec;15(12): e0009922

Impact of the introduction of chikungunya and zika viruses on the incidence of dengue in endemic zones of Mexico.

Larissa Fernandes-Matano, Irma Eloisa Monroy-Muñoz, Hector Daniel Pardavé-Alejandre, Luis Antonio Uribe-Noguez, María de Los Angeles Hernández-Cueto, Teresita Rojas-Mendoza, Clara Esperanza Santacruz-Tinoco, Concepción Grajales-Muñiz, José Esteban Muñoz-Medina.

BACKGROUND: With the arrival of chikungunya (CHIKV) and zika (ZIKV) viruses in Mexico, there was a decrease in diagnosed dengue virus (DENV) cases. During the first years of cocirculation (2015-2017), the algorithms established by epidemiological surveillance systems and the installed capacity limited us to one diagnostic test per sample, so there was an underestimation of cases until September 2017, when a multiplex algorithm was implemented. Therefore, the objective of this study was determine the impact of the introduction of CHIKV and ZIKV on the incidence of diagnosed DENV in endemic areas of Mexico, when performing the rediagnosis, using the multiplex algorithm, in samples from the first three years of co-circulation of these arboviruses.METHODOLOGY AND PRINCIPAL FINDINGS: For this, 1038 samples received by the Central Laboratory of Epidemiology between 2015 and 2017 were selected for this work. Viruses were identified by multiplex RT-qPCR, and the χ2 test was used to compare categorical variables. With the new multiplex algorithm, we identified 2.4 times the rate of arbovirosis as originally reported, evidencing an underestimation of the incidence of the three viruses. Even so, significantly less dengue was observed than in previous years. The high incidence rates of chikungunya and Zika coincided with periods of dengue decline. The endemic channel showed that the cases caused by DENV rose again after the circulation of CHIKV and ZIKV decreased. In addition, 23 cases of coinfection were identified, with combinations between all viruses.
CONCLUSIONS AND SIGNIFICANCE: The results obtained in this study show for the first time the real impact on the detected incidence of dengue after the introduction of CHIKV and ZIKV in Mexico, the degree of underestimation of these arboviruses in the country, as well as the co-infections between these viruses, whose importance clinical and epidemiological are still unknown.

DOI: https://doi.org/10.1371/journal.pntd.0009922
Sao Paulo Med J. 2021 Nov 29. pii: S1516-31802021005028201. [Epub ahead of print]

Recent dengue virus infection: epidemiological survey on risk factors associated with infection in a medium-sized city in Mato Grosso.

Dandára Thaís de Oliveira Ferreira, Marina Atanaka, Mariano Martinez Espinosa, Lavinia Schuler-Faccini, Aline da Silva Caldeira, Juliana Herrero da Silva, Viviane Karolina Vivi-Oliveira, Rayana de Castro da Paz, Vagner Ferreira do Nascimento, Ana Cláudia Pereira Terças-Trettel.

BACKGROUND: Dengue is considered to be the most important arbovirus worldwide, with important complications that increase its lethality. In Brazil, an endemic country, the disease reaches significant incidence levels, with occurrences of serious cases and high costs of hospitalizations for its treatment.OBJECTIVE: To analyze risk factors among individuals with recent histories of dengue infection in a medium-sized city in Mato Grosso.
DESIGN AND SETTING: Descriptive cross-sectional study, of epidemiological-survey type, conducted among the urban population of a city located in mid-northern Mato Grosso.
METHODS: A seroepidemiological survey using questionnaires and collection of biological material was conducted among 596 adults aged ≥ 18 years who had been selected through a cluster sampling process. Positive dengue cases were those with positive results from anti-dengue immunoassays (ELISA). Statistical analyses with descriptive and inferential techniques were used, with 95% confidence intervals and a 5% significance level.
RESULTS: The seroepidemiological profile of the study participants was predominantly female, with ages between 18 and 39 years, self-declared non-white race/color, not more than eight years of education and not living with a companion. Among the sanitary factors analyzed, the following were risk factors for dengue virus infection: no running water at home; no water supply from the public piped network; no waste from drains or toilets sent to the sewage network; endemic disease combat agents visiting the home; and presence of mosquito breeding sites at home.
CONCLUSION: Low schooling levels and previous dengue virus infection were associated with current dengue virus infection.

DOI: https://doi.org/10.1590/1516-3180.2020.0718.R1.18052021
Sci Rep. 2021 Dec 02. 11(1): 23348

Low parasite connectivity among three malaria hotspots in Thailand.

Hsiao-Han Chang, Meng-Chun Chang, Mathew Kiang, Ayesha S Mahmud, Nattwut Ekapirat, Kenth Engø-Monsen, Prayuth Sudathip, Caroline O Buckee, Richard J Maude.

Identifying sources and sinks of malaria transmission is critical for designing effective intervention strategies particularly as countries approach elimination. The number of malaria cases in Thailand decreased 90% between 2012 and 2020, yet elimination has remained a major public health challenge with persistent transmission foci and ongoing importation. There are three main hotspots of malaria transmission in Thailand: Ubon Ratchathani and Sisaket in the Northeast; Tak in the West; and Yala in the South. However, the degree to which these hotspots are connected via travel and importation has not been well characterized. Here, we develop a metapopulation model parameterized by mobile phone call detail record data to estimate parasite flow among these regions. We show that parasite connectivity among these regions was limited, and that each of these provinces independently drove the malaria transmission in nearby provinces. Overall, our results suggest that due to the low probability of domestic importation between the transmission hotspots, control and elimination strategies can be considered separately for each region.

DOI: https://doi.org/10.1038/s41598-021-02746-6
PLoS Negl Trop Dis. 2021 Dec;15(12): e0009961

Evidence of Chikungunya virus seroprevalence in Myanmar among dengue-suspected patients and healthy volunteers in 2013, 2015, and 2018.

Elizabeth Ajema Chebichi Luvai, Aung Kyaw Kyaw, Nundu Sabiti Sabin, Fuxun Yu, Saw Wut Hmone, Kyaw Zin Thant, Shingo Inoue, Kouichi Morita, Mya Myat Ngwe Tun.

INTRODUCTION: Chikungunya virus (CHIKV) is a mosquito-borne virus known to cause acute febrile illness associated with debilitating polyarthritis. In 2019, several institutions in Myanmar reported a CHIKV outbreak. There are no official reports of CHIKV cases between 2011 and 2018. Therefore, this study sought to determine the seroprevalence of CHIKV infection before the 2019 outbreak.METHODS: A total of 1,544 serum samples were collected from healthy volunteers and patients with febrile illnesses in Yangon, Mandalay, and the Myeik district in 2013, 2015, and 2018. Participants ranged from one month to 65 years of age. Antibody screening was performed with in-house anti-CHIKV IgG and IgM ELISA. A neutralization assay was used as a confirmatory test.
RESULTS: The seroprevalence of anti-CHIKV IgM and anti-CHIKV IgG was 8.9% and 28.6%, respectively, with an overall seropositivity rate of 34.5%. A focus reduction neutralization assay confirmed 32.5% seroprevalence of CHIKV in the study population. Age, health status, and region were significantly associated with neutralizing antibodies (NAbs) and CHIKV seropositivity (p < 0.05), while gender was not (p = 0.9). Seroprevalence in 2013, 2015, and 2018 was 32.1%, 28.8%, and 37.3%, respectively. Of the clinical symptoms observed in participants with fevers, arthralgia was mainly noted in CHIKV-seropositive patients.
CONCLUSION: The findings in this study reveal the circulation of CHIKV in Myanmar's Mandalay, Yangon, and Myeik regions before the 2019 CHIKV outbreak. As no treatment or vaccine for CHIKV exists, the virus must be monitored through systematic surveillance in Myanmar.

DOI: https://doi.org/10.1371/journal.pntd.0009961
Transbound Emerg Dis. 2021 Nov 30.

Autochthonous West Nile virus infection in Germany: Increasing numbers and a rare encephalitis case in a kidney transplant recipient.

Julia Schneider, Friederike Bachmann, Mira Choi, Lille Kurvits, Marie Luisa Schmidt, Leon Bergfeld, Iris Meier, Marta Zuchowski, Dirk Werber, Jörg Hofmann, Klemens Ruprecht, Kai-Uwe Eckardt, Terry Carleton Jones, Christian Drosten, Victor Max Corman.

  West Nile Virus (WNV) infections are increasingly detected in birds and horses in central Europe, with a first mosquito-borne autochthonous human infection detected in Germany in 2019. Human infections are typically asymptomatic, with occasional severe neurological disease. Because of a low number of cases in central Europe, awareness regarding potential cases is low and WNV diagnostic is neglected. We tested cerebrospinal fluid (CSF) samples from unsolved encephalitis and meningitis cases from Berlin from 2019 and 2020, and describe a WNV-encephalitis case in a 33-year old kidney transplant recipient. The infectious course was resolved by serology, RT-PCR, and sequencing of stored samples. Phylogenetic sequence analysis revealed a close relationship of the patient's WNV strain to German sequences from 2019 and 2020. A lack of travel history and patient self-isolation during the SARS-CoV-2 pandemic suggest the infection was acquired in the patient's home or garden. Serological tests of four people sharing the living space were negative. Retrospective RT-PCR and WNV-IgM testing of 671 CSF samples from unsolved encephalitis and meningitis cases from Berlin detected no additional infections. The recent increase of WNV cases illustrates the importance of considering WNV in cases of meningoencephalitis, especially in immunocompromised patients, as described here. Proper education and communication and a revised diagnostic strategy will help to raise awareness and to detect future WNV infections. This article is protected by copyright. All rights reserved.

Keywords:  Arboviruses; Diagnostics; Germany; West Nile virus; emerging disease; encephalitis

DOI:  https://doi.org/10.1111/tbed.14406
J Travel Med. 2021 Nov 26. pii: taab183. [Epub ahead of print]

Dengue during the COVID-19 pandemic.

Annelies Wilder-Smith.

Despite COVID-19-related disruptions in controlling dengue, efforts need to be maintained to prevent vector-borne diseases during this pandemic. Although travel restrictions brought a global halt to mobility and therefore also a substantial decline of imported and travel-associated dengue, dengue will become dominant again in travel medicine as soon as international travel resumes.

DOI: https://doi.org/10.1093/jtm/taab183