Culex Tritaeniorhynchus Research Articles

Japanese encephalitis in swine in San Jose, Tarlac, Philippines

ObjectivesA systematic review of multidisciplinary studies on Japanese encephalitis (JE) in the Philippines indicated that endemic foci may be found in all 17 administrative regions in the country. MethodsTo establish the etiology of the disease, virus detection and seroprevalence surveys in 198 pigs were conducted in 2010–2011 in four barangays (villages) in the Municipality of San Jose, Tarlac. Prior to the present study, JE virus genotype III (JEV GIII) was recovered from the mosquito, Culex tritaeniorhynchus, in the same municipality where backyard hog-raising and wet rice cultivation were common practices among households located within 1 km radius from the paddies. ResultsJEV GIII was detected from serum and nasal swabs from pigs, 3 to 5-month-old, from barangays Pao, Moriones, and Villa Aglipay. Immunoglobulin (Ig) M and IgG were measured by enzyme-linked immunosorbent assay in pigs < 4 to > 8 months old, with an overall total of 17.2 % and 62.1 %, respectively. The presence of these antibodies in all pigs during four observation periods indicated year-round transmission starting with the rainy season, which encompasses the months of July and September 2010. IgM represented new infections. IgG increased correspondingly with age with repeated infections in older pigs. IgG levels remained high in all barangays. The number of households with any one of the markers: IgM, IgG, reverse transcription-polymerase chain reaction averaged out at 82.5 %, reflecting as it were, vulnerability to JE in barangays where all 198 pigs were examined. This report contributes to knowledge on JE, whereby incidence in humans may be linked to its epizootic spillover from pigs. ConclusionsThe study has shown that four barangays, representing a rice-farming community, supported the enzootic cycle of JE in swine, with mosquitoes previously found to be infected with JEV GIII in San Jose. Thus, infected pigs, rainfall, and proximity of human habitation to breeding sites of vector mosquitoes constituted the risk factors for JE, as it were in other endemic countries in Asia. The finding of viral RNA in nasal swabs suggests the possibility of direct transmission among pigs via the oronasal route. From the standpoint of public health, JE immunization of children and periodic surveillance of swine are recommended.

Survey of mosquito species in intensive pig farms in Hunan province, China.

Mosquitoes (Diptera: Culicidae) are one of the most studied groups of arthropods worldwide due to their high transmission capacity for pathogens, including viruses and parasites. During June to October 2022, the prevalence of mosquito species in 12 intensive pig farms from 12 representative administrative regions in Hunan province of China was investigated using traps with ultraviolet light. All collected mosquitoes were counted and identified to species according to morphological and molecular methods. A total of 4,443 mosquito specimens were collected in the pig farms, and they represented one family, four genera and nine species. Culex pipiens pipiens (24%) was the most common mosquito species, followed by Armigeres subalbatus (23.4%) and Culex tritaeniorhynchus (20.6%). Phylogenetic analyses based on mitochondrial cox1 sequences revealed all mosquito species from present study grouping into distinct monophyletic groups corresponding to nine known mosquito species with strongly supported. The results of the present investigation have implications for the ongoing control of mosquito infestation in pig farms in Hunan province, China. This is the first report of mosquito populations in intensive pig farms in Hunan province, China.

Application of circular statistics in temporal distribution of adult mosquitoes in Qingdao, Shandong Province, China, 2021–2023

BackgroundAnalyses of the temporal distribution of mosquitoes are presented in statistical charts, but it is difficult to prove in statistics whether differences in peak periods exist among different years or habitats. This study aimed to investigate the application of circular statistics in determining the peak period and a comparison of differences.MethodsSurveillance of adult mosquitoes was conducted twice a month by light traps in five different habitats from March to November for 3 years (2021–2023) in Qingdao, Shandong Province, China. The Kruskal–Wallis test was performed to determine the differences in mosquito density among different years and habitats. Circular statistics and line charts were employed to determine the peak period and a comparison of differences.ResultsAmong a total of 14,834 adult mosquitoes comprising five mosquito species from four genera, Culex pipiens pallens was dominant and accounted for 89.6% of the specimens identified. Aedes albopictus, Armigeres subalbatus, and Anopheles sinensis made up 5.7%, 4.2%, and 0.5%, respectively. Culex tritaeniorhynchus accounted for less than 0.1%. The mean mosquito density (females/trap night) for the trapping period was 10.3 in 2021, 5.6 in 2022, and 3.6 in 2023. Among five habitats, the highest mosquito density was 8.9 in livestock sheds, followed by 6.8 in parks, 5.9 in rural dwellings, 5.5 in urban dwellings, and 5.4 in hospitals. No statistically significant differences were found among different years (H = 1.96, d.f. 2, P = 0.376) and habitats (H = 0.45, d.f. 4, P = 0.978). Overall, the peak period of mosquito activity fell in the months from June to September. The peak period among 3 years differed significantly (F(2,7022) = 119.17, P < 0.01), but there were no statistically significant differences in peak period among different habitats (F(4,7020) = −159.09, P > 0.05). ConclusionCircular statistics could be effectively combined with statistical charts to elucidate the peak period of mosquitoes and determine the differences in statistics among different years and habitats. These findings will provide valuable information for mosquito control and public health management.Graphical

Population genetic structure of Culex tritaeniorhynchus in different types of climatic zones in China

BackgroundCulex tritaeniorhynchus is widely distributed in China, from Hainan Island in the south to Heilongjiang in the north, covering tropical, subtropical, and temperate climate zones. Culex tritaeniorhynchus carries 19 types of arboviruses. It is the main vector of the Japanese encephalitis virus (JEV), posing a serious threat to human health. Understanding the effects of environmental factors on Culex tritaeniorhynchus can provide important insights into its population structure or isolation patterns, which is currently unclear.ResultsIn total, 138 COI haplotypes were detected in the 552 amplified sequences, and the haplotype diversity (Hd) value increased from temperate (0.534) to tropical (0.979) regions. The haplotype phylogeny analysis revealed that the haplotypes were divided into two high-support evolutionary branches. Temperate populations were predominantly distributed in evolutionary branch II, showing some genetic isolation from tropical/subtropical populations and less gene flow between groups. The neutral test results of HNQH (Qionghai) and HNHK(Haikou) populations were negative (P < 0.05), indicating many low-frequency mutations in the populations and that the populations might be in the process of expansion. Moreover, Wolbachia infection was detected only in SDJN (Jining) (2.24%), and all Wolbachia genotypes belonged to supergroup B. To understand the influence of environmental factors on mosquito-borne viruses, we examined the prevalence of Culex tritaeniorhynchus infection in three ecological environments in Shandong Province. We discovered that the incidence of JEV infection was notably greater in Culex tritaeniorhynchus from lotus ponds compared to those from irrigation canal regions. In this study, the overall JEV infection rate was 15.27 per 1000, suggesting the current risk of Japanese encephalitis outbreaks in Shandong Province.ConclusionsTropical and subtropical populations of Culex tritaeniorhynchus showed higher genetic diversity and those climatic conditions provide great advantages for the establishment and expansion of Culex tritaeniorhynchus. There are differences in JEV infection rates in wild populations of Culex tritaeniorhynchus under different ecological conditions. Our results suggest a complex interplay of genetic differentiation, population structure, and environmental factors in shaping the dynamics of Culex tritaeniorhynchus. The low prevalence of Wolbachia in wild populations may reflect the recent presence of Wolbachia invasion in Culex tritaeniorhynchus.

Mosquito Vector Ecology in Swamp Ecosystems

This study investigates the ecological dynamics of mosquito vectors in the swamp ecosystems of Desa Kebun Raya, Kecamatan Kintap, Kabupaten Tanah Laut, Kalimantan Selatan. An entomological survey was conducted to assess species composition, abundance, and larval indices in relation to the unique swamp habitat. Four mosquito species were identified: Culex quinquefasciatus, Culex tritaeniorhynchus, Aedes aegypti, and Aedes albopictus. The dominance of Culex species, particularly C. quinquefasciatus, suggests a strong adaptation to the swamp environment. Larval indices indicated a high risk of vector-borne disease transmission, with a House Index (HI) of 35%, Container Index (CI) of 0.14%, and Breteau Index (BI) of 64%. The study highlights the complex interactions between swamp ecology, mosquito population dynamics, and potential disease transmission risks in this understudied region of Indonesia.

An Overview of Japanese Encephalitis

INTRODUCTIONJapanese encephalitis virus (JEV) is a flavivirus, is the main cause viral encephalitis, endemic in South-East Asia, and Western Pacific regions and has become a major public health problem worldwide. JEV is transmitted to humans through the bite of an infected mosquito, mainly Culex tritaeniorhynchus that breeds in flooded rice fields, marshes, standing water around planted fields. Reservoir hosts are Adreid birds (herons and egrets), and pigs serve as amplifier hosts. Though infections are usually asymptomatic, the symptomatic Japanese encephalitis has a case fatality rate as high as 30%. Permanent neurologic or psychiatric sequelae can occur in 30-50% of those with encephalitis. There is no antiviral drug available. Treatment is mainly supportive and symptomatic. Safe and effective vaccines are available to prevent Japanese encephalitis. This article reviews recent advancements in diagnostic methods, prophylactics as well as therapeutic options and challenges to combat this zoonotic emerging and remerging viral encephalitis.

Update on the composition and distribution of the mosquito fauna (Diptera: Culicidae) in Cabo Verde, a country at risk for mosquito-borne diseases.

Mosquitoes play a critical role as vectors of pathogens affecting both humans and animals. Therefore, understanding their biodiversity and distribution is crucial to developing evidence-based vector control strategies. The current study updated the composition and distribution of mosquito species through a comprehensive survey of all municipalities of Cabo Verde. From October 2017 to September 2018, mosquito larvae and pupae were collected from 814 aquatic habitats. Anopheles gambiae (Giles, 1902) and Culex pipiens (Linnaeus, 1758) complexes were subjected to PCR-based techniques for sibling species identification. Ten mosquito species from 5 genera were identified: Aedes aegypti (Linnaeus, 1762), Aedes caspius (Pallas, 1771), Anopheles arabiensis (Patton, 1905), Anopheles pretoriensis (Theobald, 1903), Culex bitaeniorhynchus (Giles, 1901), Cx. pipiens, Culex quinquefasciatus (Say, 1823), Culex tritaeniorhynchus (Giles, 1901), Culiseta longiareolata (Macquart, 1838), and Lutzia tigripes (de Grandpre & de Charmoy, 1901). Santiago Island reported the highest number of species (n = 8). Ae. aegypti and Cx. quinquefasciatus were the most widely distributed species across the country. An. arabiensis was the sole species identified within the An. gambiae complex. The findings from our study will help guide health policy decisions to effectively control mosquito-borne diseases.

Isolation and Genomic Characterization of Kadipiro Virus from Mosquitoes in Yunnan, China.

Background: Kadipiro virus (KDV) is a species of the new 12 segmented RNA virus grouped under the genus Seadornavirus within the Reoviridae family. It has previously been isolated or detected from mosquito, Odonata, and bat feces in Indonesia, China, and Denmark, respectively. Here, we describe the isolation and characterization of a viral strain from mosquitoes in Yunnan Province, China. Methods: Mosquitoes were collected overnight using light traps in Shizong county, on July 17, 2023. Virus was isolated from the mosquito homogenate and grown using baby hamster kidney and Aedes albopictus (C6/36) cells. Preliminary identification of the virus was performed by agarose gel electrophoresis (AGE). The full-genome sequences of the strain were determined by full-length amplification of cDNAs and sequenced using next-generation sequencing. Results: We isolated a viral strain (SZ_M48) from mosquitoes (Culex tritaeniorhynchus Giles) that caused cytopathogenic effects in C6/36 cells. AGE analysis indicated a genome consisting of 12 segments of double-stranded RNA that demonstrated a "6-5-1" pattern, similar to the migrating bands of KDV. Phylogenetic analysis based on the full-genome sequence revealed that SZ_M48 is more clustered with KDV isolates from Hubei and Shangdong in China than with Indonesian and Danish strains. The identity between SZ_M48 and SDKL1625 (Shandong, China) is slightly lower than that of QTM27331 (Hubei, China), and the identity with JKT-7075 (Indonesia) and 21164-6/M.dau/DK (Denmark) is the lowest. Conclusion: The full-genome sequence of the new KDV strain described in this study may be useful for surveillance of the evolutionary characteristics of KDVs. Moreover, these findings extend the knowledge about the genomic diversity, potential vectors, and the distribution of KDVs in China.

Population Genetics of Culex tritaeniorhynchus (Diptera: Culicidae) in Türkiye

PurposeMosquitoes are important vectors of pathogens that can affect humans and animals. Culex tritaeniorhynchus is an important vector of arboviruses such as Japanese encephalitis virus, West Nile virus among various human and animal communities. These diseases are of major public health concern and can have huge economic and health burdens in prevalent countries. Although populations of this important mosquito species have been detected in the Mediterranean and Aegean regions of Türkiye; little is known about its population structure. Our study is to examine the population genetics and genetic composition of Cx. tritaeniorhynchus mosquitoes collected from several localities using cytochrome oxidase subunit I (COI) and the NADH dehydrogenase subunit 5 genes (ND5). This is the first extensive study of Cx. tritaeniorhynchus in the mainland Türkiye with sampling spanning many of provinces.MethodsIn this study, DNA extraction, amplification of mitochondrial COI and ND5 genes and population genetic analyses were performed on ten geographic populations of Culex tritaeniorhynchus in the Aegean and Mediterranean region of Türkiye.ResultsBetween 2019 and 2020, 96 samples were collected from 10 geographic populations in the Aegean and Mediterranean regions; they were molecularly analyzed and 139 sequences (50 sequence for COI and 89 sequence for ND5) were used to determine the population structure and genetic diversity. For ND5 gene region, the samples produced 24 haplotypes derived from 15 variable sites and for COI gene region, 43 haplotypes were derived from 17 variable sites. The haplotype for both gene regions was higher than nucleotide diversity. Haplotype phylogeny revealed two groups present in all populations. AMOVA test results show that the geographical populations were the same for all gene regions. Results suggest that Cx. tritaeniorhynchus is a native population in Türkiye, the species is progressing towards speciation and there is no genetic differentiation between provinces and regions.ConclusionThis study provides useful information on the molecular identifcation and genetic diversity of Cx. tritaeniorhynchus; these results are important to improve mosquito control programs.

Seasonal species composition, abundance and public health importance of mosquito vectors (Diptera: Culicidae) in Huai Tha Khoei Reservoir, Ratchaburi, Thailand

Abstract. Chaiphongpachara T, Laojuna S. 2024. Seasonal species composition, abundance and public health importance of mosquito vectors (Diptera: Culicidae) in Huai Tha Khoei Reservoir, Ratchaburi, Thailand. Biodiversitas 25: 1264-1275. Mosquitoes are vectors for pathogens that cause life-threatening diseases in humans and animals. Significant mosquito-borne diseases include malaria, dengue, chikungunya, Zika, Japanese encephalitis, and filariasis. Anthropogenic environmental changes can significantly impact the dynamics of disease vector populations, which can lead to outbreaks of mosquito-borne diseases. This study investigated the seasonal variation in species composition and abundance of mosquito vectors around the Huai Tha Khoei Reservoir in Ratchaburi Province, Thailand, across cool, hot, and rainy seasons. A total of 1363 mosquitoes, representing 30 species from five genera, were collected. In particular, 25 of these species, accounting for 83.33% of the total, were identified as vectors of human pathogens. The most dominant species across all seasons was Culex tritaeniorhynchus Giles 1901, representing 39.47% (n=538) of the total, followed by Anopheles barbirostris Wulp 1884 s.l. (14.38%, n = 196) and Culex vishnui Theobald 1901 (9.02%, n=123). The Shannon diversity index was highest during the rainy season (H’= 2.144) and lowest in the hot season (H’=1.788). This is consistent with the results of the UPGMA tree based on beta diversity, indicating that mosquito diversity in the rainy season differs significantly from that in the cool and hot seasons. The findings enhance our understanding of the impact of seasonality on mosquito vectors in this region, which is crucial for developing effective disease control strategies. Additionally, this study serves as a valuable reference for understanding the diversity of mosquito vectors in other areas.

Infection, dissemination, and transmission of lumpy skin disease virus in Aedes aegypti (Linnaeus), Culex tritaeniorhynchus (Giles), and Culex quinquefasciatus (Say) mosquitoes

Lumpy skin disease virus (LSDV) is a transboundary viral disease in cattle and water buffaloes. Although this Poxvirus is supposedly transmitted by mechanical vectors, only a few studies have investigated the role of local vectors in the transmission of LSDV. This study examined the infection, dissemination, and transmission rates of LSDV in Aedes aegypti, Culex tritaeniorhynchus, and Culex quinquefasciatus following artificial membrane feeding of 102.7, 103.7, 104.7 TCID50/mL LSDV in sheep blood. The results demonstrated that these mosquito species were susceptible to LSDV, with Cx tritaeniorhynchus exhibiting significantly different characteristics from Ae. aegypti and Cx. quinquefasciatus. These three mosquito species were susceptible to LSDV. Ae. aegypti showed it as early as 2 days post-infection (dpi), indicating swift dissemination in this particular species. The extrinsic incubation period (EIP) of LSDV in Cx. tritaeniorhynchus and Cx. quinquefasciatus was 8 and 14 dpi, respectively. Ingestion of different viral titers in blood did not affect the infection, dissemination, or transmission rates of Cx. tritaeniorhynchus and Cx. quinquefasciatus. All rates remained consistently high at 8–14 dpi for Cx. tritaeniorhynchus. In all three species, LSDV remained detectable until 14 dpi. The present findings indicate that, Ae. aegypti, Cx. tritaeniorhynchus, and Cx. quinquefasciatus may act as vectors during the LSDV outbreak; their involvement may extend beyond being solely mechanical vectors.

Impact of ecological migration village construction on vector mosquito and mosquito-borne disease in the southern Yunnan Province, China

To evaluate the influence of ecological migration village construction on mosquito vector populations and mosquito-borne diseases in southern Yunnan Province. Two vicinal villages in Mengla County, the southern part of Yunnan Province, a native village, and a newly built village, were selected as study sites. Malaria and Japanese Encephalitis vector mosquito population divergence between the two villages were studied. Malaria and Japanese Encephalitis (JE) cases in the two villages were also compared. Anopheles minimus was the dominant population in houses in the newly built village, and An. jeyporiensis dominated the native village. Accordingly, there were nine malaria cases in the new village compared with zero cases in the native village. Culex tritaeniorhynchus, the chief JE vector in the study area, displayed no difference between the two villages; however, there was a higher density of the local secondary JE vector (Cx. pseudovishnui) in the native village than in the new one. The JE cases in the villages corresponded to zero. From the vector-borne disease perspective, our results suggest that local community should pay more attention to malaria and An. minimus during the construction of an ecological migration village in the new Chinese Western Developing Plan (CWDP) in southern Yunnan Province.

Geographical Characteristics of Culex tritaeniorhynchus and Culex orientalis Microbiomes in Korea.

Mosquitoes, the primary vectors of arboviruses, harbor a diverse microbiome that plays a crucial role in their development, immunity, and vector competence. The composition of the mosquito microbiome is heavily influenced by the environment and habitats. Therefore, identifying the relationship between the habitat and the mosquito's microbial community can improve the overall understanding of mosquito biology. However, The microbiome profiles of Culex tritaeniorhynchus and Culex orientalis, known as transmission vectors of the Japanese encephalitis virus, are poorly understood. Using 16S rRNA Illumina sequencing, we hereby investigated the microbial profiles in these two mosquito species collected in several areas in the Republic of Korea. Thirty-six prevalent bacterial families were identified from these mosquito species. The microbial composition variations were primarily influenced by the mosquito collecting sites. Moreover, species biomarkers were identified by utilizing the regional specificity of the mosquito microbiome. Based on the microbiome profiles representing high similarity, Culex orientalis may share an ecological niche with Culex tritaeniorhynchus.

Wing geometric morphometrics and COI barcoding of Culex pipiens subgroup in the Republic of Korea

Two members of the Culex pipiens subgroup, Culex pallens and Culex pipiens f. molestus, are known to occur in the Republic of Korea (ROK). These species exhibit morphologically similar features and are challenging to distinguish below the species level. Therefore, this study utilized wing geometric morphometrics (GM) on the right wing of the Culex pipiens subgroup, alongside sequencing of the cytochrome c oxidase subunit I (COI) region. Mosquitoes were collected from 11 locations between June and October (2020–2022) to minimize regional and seasonal variations. Additionally, Culex pipiens f. pipiens, which is not native to the ROK, was included in the analysis. Culex tritaeniorhynchus, Aedes albopictus, and Anopheles sinensis, the primary vectors in the ROK, were used as outgroups for comparison. All three taxa in the Culex pipiens subgroup could be identified with an 82.4%–97.0% accuracy using GM. However, a comparison of the COI regions of the Culex pipiens subgroup revealed no clear differences between the taxa. These data can be used for accurate identification, contributing to effective mosquito control, in addition to providing a foundation for evolutionary and ecological studies on wing shape differences.

Vector bionomic of Culex species in possible Japanese Encephalitis Transmitted areas of Ein-me Township, Ayayawady Region in Myanmar

Japanese encephalitis is a public health problem in many parts of Myanmar. The diseases are transmitted to human by the biting of vector mosquitoes. The study was conducted in JE suspected cases occurred villages ThaPhan Pinseit and ThaPyu Pinseit villages in ThaPhan Pinseit RHC and PaukGone and SarPhyusu villages in PaukGone village in PaukGone RHC from Ayeyawady Region were selected for JE vector surveillance from December 2023 to March 2024. 50 houses from the pigs were randomly selected from each village. Mosquitoes were collected in all selected houses and pig farms using WHO sucking tubes. Larvae were collected in and around 1 Kilometer radius from study sites. Result found that JE main vector Cx. tritaeniorhynchus was abundantly collected in all study village and the highest number of vectors Cx. tritaeniorhynchus was collected from SarPhyusu village 2284 followed by ThaPyu Pinseit 1890 and lowest number of main vectors was collected in ThaPhan Pinseit village (1268). In overall collected mosquitoes, the highest density was found 74.18% of main vector Cx. tritaeniorhynchus followed by suspected vector Cx. vishnui 10.04%, and lowest density was observed Mansonia and An. vagus 0.33% each. Peak biting time of main vector Cx. tritaeniorhynchus was found 9-10 pm. Suspected vector Cx. vishnui was also collected in high number in all villages. Nine species of mosquitoes were collected from the study villages. Of this only four species of An. hyrcanus, An. barbirostris, An. vagus and An. tesellatus were collected. These Anopheles species were available in PaukGone and SarPhyusu villages. Anopheles hyrcanus was collected from all villages. Culex tritaeniorhynchus larvae were abundantly collected from rice fields, polluted water pools and stagnant water pools with plenty of hyacinth plants and also larvae were collected in concrete jars, Bago jars and metal drums water which water was stored for fire water. High density of main vector and suspected vector were collected in all JE suspected villages, pig farms, pigs, and breeding sources of vectors mosquitoes were available in the villages and also JE suspected cases are available in the all villages. This study provides information of high collection of main vector adult and larvae on risk of further transmission in the study areas. Environmental and ecological factors are responsible for the spread of JE virus. Therefore, awareness of community to vector borne diseases control activities and health education to all family members should be strengthened to prevent JE transmission in the villages.

Serological Investigation of Japanese Encephalitis Virus Infection in Commercially Reared Pigs, Southwestern Nigeria.

Japanese encephalitis virus (JEV) is a zoonotic arbovirus that causes abortion, stillbirth, and congenital defects in pigs, and epidemic encephalitis in humans. Currently, there is scarcity of information on JEV infection in pigs in Nigeria. Since the Culex tritaeniorhynchus vector of JEV is present in Nigeria and considering recent anecdotal reports of abortions and birth of weak piglets in some pig farms in southwestern Nigeria, there is a need for studies on the presence of the virus and its true burden among pig populations in the country. Serum samples (n=368) obtained from farm-reared pigs in four States of southwestern Nigeria were screened for JEV-specific IgG antibodies using a commercial ELISA kit. An overall JEV seropositivity of 35.1% (95% CI: 30.18 - 39.93%) was obtained, with detectable antibodies in pigs of all age groups, breeds, sex, and locations. Our results suggest natural exposure of these unvaccinated intensively reared pigs to JEV circulating silently in the swine population with significant association of the seropositivity with location (state/community in which the pig farms exist) and breed of the pigs studied. This first report of detection of anti-JEV antibodies in pigs in Nigeria indicates that JEV circulated among these pigs and underscores the need for active surveillance for JEV in humans, pigs, and mosquitoes to provide valuable epidemiological data for the design of effective control strategies against the virus, thus forestalling potential future outbreaks of the infection.

The spatiotemporal distribution and prognostic factors of Japanese encephalitis in Shanxi Province, China, 2005-2022.

Japanese encephalitis (JE) is a naturally occurring localized disease caused by the Japanese encephalitis virus, which is spread by the Culex tritaeniorhynchus. China has a high rate of JE. Shanxi, located in North China, has a high prevalence of adult JE. Adult JE has more severe complications, mortality, and a higher disease burden, making it a public health issue. This retrospective study examined the dynamic epidemic changes, high-risk areas of JE, and clinical characteristics and prognostic factors of adult JE in Shanxi Province. The findings revealed that July to September was the primary epidemic season of JE and that JE cases were mainly in individuals over the age of 40. The incidence of JE from 2005 to 2022 demonstrated a positive spatial correlation with significant clustering characteristics, with high-incidence clusters in the south and southeast. Multivariate logistic regression analysis revealed that higher cerebrospinal fluid pressure, higher white blood cell counts, higher neutrophil percentage, deep coma, and lower albumin were independent factors for poor prognosis of adult JE. The developed risk prediction model holds great promise in early prognosis assessment of patients, providing a basis for clinical decision-making and early clinical intervention.

Using MALDI-TOF MS to Identify Mosquitoes from Senegal and the Origin of Their Blood Meals.

Mosquitoes are arthropods that represent a real public health problem in Africa. Morphology and molecular biology techniques are usually used to identify different mosquito species. In recent years, an innovative tool, matrix-assisted desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), has been used to identify many arthropods quickly and at low cost, where equipment is available. We evaluated the ability of MALDI-TOF MS to identify mosquitoes collected in Senegal and stored for several months in silica gel, and to determine the origin of their blood meal. A total of 582 mosquitoes were collected and analysed. We obtained 329/582 (56.52%) MALDI-TOF MS good-quality spectra from mosquito legs and 123/157 (78.34%) good-quality spectra from engorged abdomens. We updated our home-made MALDI-TOF MS arthropod spectra database by adding 23 spectra of five mosquito species from Senegal that had been identified morphologically and molecularly. These included legs from Anopheles gambiae, Anopheles arabiensis, Anopheles cf. rivulorum, Culex nebulosus, Anopheles funestus, and three spectra from abdomens engorged with human blood. Having updated the database, all mosquitoes tested by MALDI-TOF MS were identified with scores greater than or equal to 1.7 as An. gambiae (n = 64), Anopheles coluzzii (n = 12), An. arabiensis (n = 1), An. funestus (n = 7), An. cf rivulorum (n = 1), Lutzia tigripes (n = 3), Cx. nebulosus (n = 211), Culex quinquefasciatus (n = 2), Culex duttoni (n = 1), Culex perfescus (n = 1), Culex tritaeniorhynchus (n = 1), and Aedes aegypti (n = 2). Blood meal identification by MALDI-TOF MS revealed that mosquitoes had fed on the blood of humans (n = 97), cows (n = 6), dogs (n = 2), goats (n = 1), sheep (n = 1), and bats (n = 1). Mixed meals were also detected. These results confirm that MALDI-TOF MS is a promising technique for identifying mosquitoes and the origin of their blood meal.

The identification and genetic characteristics of Quang Binh virus from field-captured Culex tritaeniorhynchus (Diptera: Culicidae) from Guizhou Province, China

BackgroundMosquitoes carry a variety of viruses that can cause disease in humans, animals and livestock. Surveys for viruses carried by wild mosquitoes can significantly contribute to surveillance efforts and early detection systems. In addition to mosquito-borne viruses, mosquitoes harbor many insect-specific viruses (ISVs). Quang Binh virus (QBV) is one such example, categorized as an ISV within the Flavivirus genus (family Flaviviridae). QBV has been specifically documented in Vietnam and China, with reports limited to several mosquito species.MethodsThe homogenate obtained from female mosquitoes was cultured on C6/36 (Aedes albopictus) and BHK-21 (baby hamster kidney) cell lines. Positive cultures were identified by reverse transcription-polymerase chain reaction (RT‒PCR) with taxon- or species-specific primers. Next-generation sequencing was employed to sequence the complete genomes of the identified positive samples. Subsequently, phylogenetic, gene homology, molecular evolutionary and genetic variation analyses were conducted.ResultIn 2021, a total of 32,177 adult female mosquitoes were collected from 15 counties in Guizhou Province, China. The predominant mosquito species identified were Culex tritaeniorhynchus, Armigeres subalbatus and Anopheles sinensis. Among the collected mosquitoes, three positive cultures were obtained from Cx. tritaeniorhynchus pools, revealing the presence of Quang Binh virus (QBV) RNA sequences. Phylogenetic analysis indicated that the three Guizhou isolates, along with the prototype isolate from Vietnam, formed distinct branches. These branches were primarily closely related to other QBV isolates reported in China. Comparative analysis revealed a high degree of nucleotide and amino acid homology between the Guizhou isolates and both Vietnamese and other indigenous Chinese isolates. Additionally, nonsynonymous single-nucleotide variants (SNVs) were observed in these strains compared to the QBV prototype strain.ConclusionThis study represents the first report of QBV presences in Cx. tritaeniorhynchus mosquitoes in Guizhou Province, China. Phylogenetic tree analysis showed that the three Guizhou isolates were most closely related to the QBV genes found in China. In addition, the study of the genetic characteristics and variation of this virus provided a deeper understanding of QBV and enriched the baseline data of these insect-specific flaviviruses (ISFVs).Graphical

Genotype Change in Circulating JEV Strains in Fujian Province, China.

Japanese encephalitis (JE), found in pigs, is a serious mosquito-borne zoonotic infectious disease caused by the Japanese encephalitis virus (JEV). JEV is maintained in an enzootic cycle between mosquitoes and amplifying vertebrate hosts, mainly pigs and wading birds. It is transmitted to humans through the bite of an infected mosquito, allowing the pathogen to spread and cause disease epidemics. However, there is little research on JEV genotype variation in mosquitoes and pigs in Fujian province. Previous studies have shown that the main epidemic strain of JEV in Fujian Province is genotype III. In this study, a survey of mosquito species diversity in pig farms and molecular evolutionary analyses of JEV were conducted in Fujian, China, in the summer of 2019. A total of 19,177 mosquitoes were collected at four sites by UV trap. Four genera were identified, of which the Culex tritaeniorhynchus was the most common mosquito species, accounting for 76.4% of the total (14,651/19,177). Anopheles sinensi (19.25%, 3691/19,177) was the second largest species. High mosquito infection rateswere an important factor in the outbreak. The captured mosquito samples were milled and screened with JEV-specific primers. Five viruses were isolated, FJ1901, FJ1902, FJ1903, FJ1904, and FJ1905. Genetic affinity was determined by analyzing the envelope (E) gene variants. The results showed that they are JEV gene type I and most closely related to the strains SH-53 and SD0810. In this study, it was found through genetic evolution analysis that the main epidemic strain of JE in pig farms changed from gene type III to gene type I. Compared with the SH-53 and SD0810 strains, we found no change in key sites related to antigenic activity and neurovirulence of JEV in Fujian JEV and pig mosquito strains, respectively. The results of the study provide basic data for analyzing the genotypic shift of JEV in Fujian Province and support the prevention and control of JEV.