Control study of Musca domestica (Diptera, Muscidae) in Misan Province.

Background: Houseflies are the most common type of Diptera, specifically Muscidae, worldwide, representing more than 90% of all species. This family has over 170 genera and 4200 species, but a few are of medical significance. This study aimed to estimate and assessing the measures to control and prevent grow-up inside houses and flying of the housefly ( Musca domestica Linnaeus, 1758) in Misan. Methods: The study occurred over 12 months, from December 2020 to December 2021. Using plastic containers, Musca domestica were collected from all potential breeding sites in the study region (inside and around houses). Sticky oil paper and traps were used to collect the insects. The collected insects were transferred to sealed plastic containers and then to the laboratory of the Department of Microbiology.Out of 200 randomly selected houses, 150 (75%) contained insects. Light traps and sticky oil papers were the most effective control measures, with 26.7% and 25.9% of the Musca domestica collected from these methods, respectively. The ratio of male (233) to female (456) Musca was 1:2, with a significant difference between the frequencies (P<0.05). A large population of houseflies was collected during the hot season (501, 72.7%), whereas fewer Musca were collected during the cold months (188, 27.3%), with a strongly significant difference (P<0.05). The percentage of HI was 54.4%, the CI was 21.9%, and the BI was 79.9%. The overall larval densities (LD) were at a medium level. Conclusions: Misan has a high density of Musca domestica, with females being more prominent than males. Hot climate, humid sites, and dirty places are responsible for the breeding of houseflies. The overall larval density was medium. Therefore, the risk of transmitting infectious diseases by houseflies is high within the boundaries of Misan province, and effective control parameters should include measures like light traps and sticky oil.

Understanding dengue solution and larval indices surveillance system among village health volunteers in high- and low-risk dengue villages in southern Thailand.

Background: Successful dengue solutions require community collaboration between agencies engaged in human health, vector control and the environment. In Thailand, village health volunteers emphasize the need for a health working group to interact, collaborate, and coordinate actions. The objectives of this study were to acquire an understanding of dengue solutions, as well as the larval indices surveillance system of village health volunteers in high- and low-risk dengue villages. Methods: After 12 months of training in dengue prevention and setting larval indices surveillance systems, an analytical cross-sectional survey was conducted. A total of 117 villages were included in the 18 primary care facilities within one district in southern Thailand, and they were divided into 71 high-risk and 46 low-risk dengue villages. Sample size was determined using the G*power formula. The content validity index and reliability values of Cronbach's alpha coefficient for the questionnaires were 0.91 and 0.83, respectively. A random sampling approach was used to acquire data. The chi-square test, t-test, and odds ratio were used to assess the sample's level of understanding. Results: The study included 1302 village health volunteers, including 895 and 407 from high- and low-risk dengue communities, respectively. In total, 87.9% were female, 51.6% were 20-35 years old, 48.8% had worked as a village health volunteer for 11-20 years, 27.1% had an upper elementary education, and 59.1% had dengue in the previous 12 months. Understanding of the dengue solution and larval indices surveillance system varied across high- and low-risk dengue villages. Village health volunteers with a high level of understanding of the dengue solution and larval indies surveillance system were 1.064 and 1.504 times more likely to stay in high-risk dengue villages, respectively (odds ratio [OR] = 1.064, 95% confidence interval [CI]:0.798-1.419, p = 0.672 and OR = 1.504, 95% CI:1.044-2.167, p = 0.028). Conclusions: Village health volunteers require ongoing training to understand the prevention and control of dengue and larval indices surveillance systems, promote awareness, and monitor dengue in both high- and low-risk dengue villages.

Mosquito larva distribution and natural Wolbachia infection in campus areas of Nakhon Ratchasima, Thailand

Objective: To determine the prevalence of mosquito larvae in campus areas and the infection rate of endosymbiotic bacteria, Wolbachia in mosquito larvae. Method: The mosquito larvae samples were collected in residential areas and academic buildings of Suranaree University of Technology located in Northeastern Thailand during 2017-2018. Mosquito species identification was performed using GLOBE mosquito protocols and Rattanarithikul & Panthusiri's keys. The gene encoding for the surface protein of Wolbachia was amplified by PCR and confirmed by DNA sequencing. Results: Armigeres sp. is the highest proportion of mosquito larvae followed by Culex spp., Aedes albopictus, Aedes aegypti, and Toxorynchites spp., respectively. Aedes aegypti have breeding sites mostly in the containers found indoors, whereas the main breeding sites of Aedes albopictus were found in both outdoors and indoors. The House Index and Breteau Index for Aedes spp. was more than 5% and 20%, respectively, in both areas, indicating that these areas are dengue sensitive. The highest proportion of Wolbachia infection was found in the larvae of Culex spp. (86.21%), followed by Aedes albopictus (69.23%) and rarely detected in Aedes aegypti (9.09%). Conclusion: The present study reported the first natural infection of Wolbachia in mosquito larvae in Thailand. Our result suggested that the mosquito species containing higher proportion of Wolbachia are less likely to be vectors for dengue. Therefore, Wolbachia transfection in mosquito larvae could be applied as a biocontrol for dengue and other mosquito-borne disease prevention.

Infestation measured by Aedes aegypti larval surveys as an indication of future dengue epidemics: an evaluation for Brazil.

BACKGROUND: Aedes aegypti rapid larval surveys are mandatory in Brazil. Here, we retrospectively examined whether the house index estimated by larval surveys served as a useful tool in anticipating epidemics within Brazilian municipalities from 2009-2015. METHODS: We used correlation indices and classification analysis stratified by year, region, population size and time after the national larval survey. RESULTS: We found no association between the house index and the proportion of municipalities experiencing an epidemic. The sensitivity of a high score house index in predicting an epidemic was 7.20% (95% CI 6.22 to 8.33%) for all years combined. The positive predictive value of a high score house index to predict a 'true epidemic' was 38.96%, lower than the negative predictive values of a low score house index for predicting 'no epidemic' (56.96%). The highest overall sensitivity was observed in the North region (20.15%; 95% CI 17.14 to 23.53%). The sensitivity of a high score house index demonstrated a monotonic decrease with increasing time from larval collection. CONCLUSIONS: Larval surveys are surveillance tools with the potential to risk-stratify and guide dengue control programs towards judicious resource allocation. However, the national rapid larval survey performed in Brazil, in its present form, consistently underpredicts dengue epidemics.

Chikungunya fever outbreak identified in North Bali, Indonesia.

Background: Chikungunya virus (CHIKV) infections have been reported sporadically within the last 5 years in several areas of Indonesia including Bali. Most of the reports, however, have lacked laboratory confirmation. Method: A recent fever outbreak in a village in the North Bali area was investigated using extensive viral diagnostic testing including both molecular and serological approaches. Results and conclusions: Ten out of 15 acute febrile illness samples were confirmed to have CHIKV infection by real-time PCR or CHIKV-specific IgM enzyme-linked immunosorbent assay (ELISA). The outbreak strain belonged to the Asian genotype with highest homology to other CHIKV strains currently circulating in Indonesia. The results are of public health concern particularly because Bali is a popular tourist destination in Indonesia and thereby the potential to spread the virus to non-endemic areas is high. GenBank accession numbers: KY885022, KY885023, KY885024, KY885025, KY885026, KY885027.

Epidemic resurgence of dengue fever in Singapore in 2013-2014: A virological and entomological perspective.

BACKGROUND: Dengue resurged in Singapore during 2013-14, causing an outbreak with unprecedented number of cases in the country. In the present study, we summarise the epidemiological, virological and entomological findings gathered through the dengue surveillance programme and highlight the drivers of the epidemic. We also describe how the surveillance system facilitated the preparedness to moderate epidemic transmission of dengue in the country. METHODS: The case surveillance was based on a mandatory notification system that requires all medical practitioners to report clinically-suspected and laboratory-confirmed cases within 24 hours. The circulating Dengue virus (DENV) populations were monitored through an island wide virus surveillance programme aimed at determining the serotypes and genotypes of circulating virus strains. Entomological surveillance included adult Aedes surveillance as well as premise checks for larval breeding. RESULTS: A switch in the dominant serotype from DENV-2 to DENV-1 in March 2013 signalled a potential spike in cases, and the alert was corroborated by an increase in average Aedes house index. The alert triggered preparedness and early response to moderate the impending outbreak. The two-year outbreak led to 22,170 cases in 2013 and 18,338 in 2014, corresponding to an incidence rate of 410.6 and 335.0 per 100,000 population, respectively. DENV-1 was the dominant serotype in 2013 (61.7 %, n = 5,071) and 2014 (79.2 %, n = 5,226), contributed largely by a newly-introduced DENV-1 genotype III strain. The percentage of houses with Ae. aegypti breeding increased significantly (p < 0.001) from 2012 (annual average of 0.07 %) to 2013 (annual average of 0.14 %), followed by a drop in 2014 (annual average of 0.10 %). Aedes breeding data further showed a wide spread distribution of Ae. aegypti in the country that corresponded with the dengue case distribution pattern in 2013 and 2014. The adult Aedes data from 34 gravitrap sentinel sites revealed that approximately 1/3 of the monitored sites remained at high risk of DENV transmission in 2013. CONCLUSIONS: The culmination of the latest epidemic is likely to be due to a number of demographic, social, virological, entomological, immunological, climatic and ecological factors that contribute to DENV transmission. A multi-pronged approach backed by the epidemiological, virological and entomological understanding paved way to moderate the case burden through an integrated vector management approach.

Updating the geographical distribution and frequency of Aedes albopictus in Brazil with remarks regarding its range in the Americas

The geographical distribution of Aedes albopictus in Brazil was updated according to the data recorded across the country over the last eight years. Countrywide house indexes (HI) for Ae. albopictus in urban and suburban areas were described for the first time using a sample of Brazilian municipalities. This mosquito is currently present in at least 59% of the Brazilian municipalities and in 24 of the 27 federal units (i.e., 26 states and the Federal District). In 34 Brazilian municipalities, the HI values for Ae. albopictus were higher than those recorded for Ae. aegypti, reaching figures as high as HI = 7.72 in the Southeast Region. Remarks regarding the current range of this mosquito species in the Americas are also presented. Nineteen American countries are currently infested and few mainland American countries have not confirmed the occurrence of Ae. albopictus. The large distribution and high frequency of Ae. albopictus in the Americas may become a critical factor in the spread of arboviruses like chikungunya in the new world.

Study on Entomological Surveillance and its Significance during a Dengue Outbreak in the District of Tirunelveli in Tamil Nadu, India.

OBJECTIVES: TO STUDY THE SIGNIFICANCE OF ENTOMOLOGICAL SURVEILLANCE, THE HOUSE INDEX (HI), CONTAINER INDEX (CI), AND BRETEAU INDEX (BI) WERE DETERMINED TO ESTIMATE THE DEGREE OF A MAJOR DENGUE OUTBREAK IN TIRUNELVELI, TAMIL NADU, INDIA (LATITUDE: 8°42'N; Longitude: 77°42'E) in May 2012. METHODS: The HI, CI, and BI were determined in a primary health center (PHC) in the village of Maruthamputhur (Pappakudi taluk, Tirunelveli) by carrying out an antilarval (AL) work that involved door-to-door search for immature stages of Aedes spp. mosquitoes by trained field workers and volunteers. The work of field workers was evaluated by a junior and senior entomologist the following day. RESULTS: Before the AL work, the reported numbers of fever cases from Week 1 to 5 in Maruthamputhur were 211, 394, 244, 222, and 144 with two deaths. By contrast, after the AL work, these numbers were considerably reduced and there was no fever-related death (the HI was reduced from 48.2% to 1.6%, the CI from 28.6% to 0.4%, and the BI from 48.2 to 1.6). CONCLUSION: Because no specific medicine and vaccines are available to treat dengue fever and dengue hemorrhagic fever, entomological surveillance and its significance can be used to halt the outbreak of dengue as shown in this study.

Vector density and the control of kala-azar in Bihar, India

Bihar, India has been in the grip of kala-azar for many years. Its rampant and severe spread has made life miserable in most parts of the state. Such conditions require a comprehensive understanding of this affliction. The numbers coming out of the districts prone to the disease in the north and south Ganges have provided us with several startling revelations, as there are striking uniformities on both sides, including similar vegetation, water storage facilities, house construction and little change in risk factors. The northern areas have been regularly sprayed with DDT since 1977, but eradication of the disease appears to be a distant dream. In 2007 alone, there were as many as 37,738 cases in that region. In contrast, the southern districts of Patna and Nalanda have never had the disease in its epidemic form and endemic disease has been present in only some pockets of the two districts. In those cases, two rounds of spraying with DDT had very positive results, with successful control and no new established foci. In addition, an eleven-year longitudinal study of the man hour density and house index for the vector Phlebotomus argentipes demonstrated that they were quite high in Patna and Nalanda and quite low in north Bihar. Given these facts, an attempt has been made to unravel the role of P. argentipes saliva (salivary gland) in the epidemiology of kala-azar. It was determined that patchy DDT spraying should be avoided for effective control of kala-azar.