A review of the economic evidence of Aedes-borne arboviruses and Aedes-borne arboviral disease prevention and control strategies.

Introduction:Aedes-borne arboviruses contributes substantially to the disease and cost burden.Areas covered: We performed a systematic review of the economic evidence surrounding aedes-borne arboviruses and strategies to prevent and control these diseases to inform disease control policy decisions and research directions. We searched four databases covering an 18-year period (2000-2018) to identify arboviral disease-related cost of illness studies, cost studies of vector control and prevention strategies, cost-effectiveness analyses and cost-benefit analyses. We identified 74 published studies that revealed substantial global total costs in yellow fever virus and dengue virus ranging from 2.1 to 57.3 billion USD. Cost studies of vector control and surveillance programs are limited, but a few studies found that costs of vector control programs ranged from 5.62 to 73.5 million USD. Cost-effectiveness evidence was limited across Aedes-borne diseases, but generally found targeted dengue vaccination programs cost-effective. This review revealed insufficient economic evidence for vaccine introduction and implementation of surveillance and vector control programs.Expert opinion: Evidence of the economic burden of aedes-borne arboviruses and the economic impact of strategies for arboviral disease prevention and control is critical to inform policy decisions and to secure continued financial support for these preventive and control measures.

Entomological Assessment of the Status and Risk of Mosquito-borne Arboviral Transmission in Ghana.

Entomological surveillance is one of the tools used in monitoring and controlling vector-borne diseases. However, the use of entomological surveillance for arboviral infection vector control is often dependent on finding infected individuals. Although this method may suffice in highly endemic areas, it is not as effective in controlling the spread of diseases in low endemic and non-endemic areas. In this study, we examined the efficiency of using entomological markers to assess the status and risk of arbovirus infection in Ghana, which is considered a non-endemic country, by combining mosquito surveillance with virus isolation and detection. This study reports the presence of cryptic species of mosquitoes in Ghana, demonstrating the need to combine morphological identification and molecular techniques in mosquito surveillance. Furthermore, although no medically important viruses were detected, the importance of insect-specific viruses in understanding virus evolution and arbovirus transmission is discussed. This study reports the first mutualistic relationship between dengue virus and the double-stranded RNA Aedes aegypti totivirus. Finally, this study discusses the complexity of the virome of Aedes and Culex mosquitoes and its implication for arbovirus transmission.

External quality assessment for arbovirus diagnostics in the World Health Organization Western Pacific Region, 2013-2016: improving laboratory quality over the years.

Arboviruses continue to pose serious public health threats in the World Health Organization (WHO) Western Pacific Region. As such, laboratories need to be equipped for their accurate detection. In 2011, to ensure test proficiency, the WHO Regional Office for the Western Pacific piloted an external quality assessment (EQA) programme for arbovirus diagnostics. By 2016, it had grown into a global programme with participation of 96 laboratories worldwide, including 25 laboratories from 19 countries, territories and areas in the Region. The test performance of the 25 laboratories in the Region in 2016 was high with 23 (92%) reporting correct results in all specimens for dengue and chikungunya viruses. For Zika virus, 18 (72%) of the 25 laboratories reported correct results in all specimens, while seven (28%) demonstrated at least one error. When comparing iterations of this EQA programme in the Region between 2013 and 2016, the number of participating laboratories increased from 18 to 25. The first round only included dengue virus, while the latest round additionally included chikungunya, Zika and yellow fever viruses. Proficiency for molecular detection of dengue virus remained high (83-94%) over the four-year period. The observed proficiency for arbovirus diagnostics between 2013 and 2016 is an indicator of laboratory quality improvement in the Region.

Simultaneous detection of three arboviruses using a triplex RT-PCR: enzyme hybridization assay.

Arboviruses represent a serious problem to public health and agriculture worldwide. Fast, accurate identification of the viral agents of arbovirus-associated disease is essential for epidemiological surveillance and laboratory investigation. We developed a cost-effective, rapid, and highly sensitive one-step "triplex RT-PCR enzyme hybridization" assay for simultaneous detections of Japanese Encephallitis virus (JEV, Flaviviridae), Getah virus (GETV, Togaviridae), and Tahyna virus (TAHV, Bunyaviridae) using three pairs of primers to amplify three target sequences in one RT-PCR reaction. The analytical sensitivity of this assay was 1 PFU/mL for JEV, 10 PFU/mL for GETV, and 10 PFU/mL for TAHV. This assay is significantly more rapid and less expensive than the traditional serological detection and single RT-PCR reaction methods. When "triplex RT-PCR enzyme hybridization" was applied to 29 cerebrospinal fluid (CSF) samples that were JEV-positive by normal RT-PCR assay, all samples were strongly positive for JEV, but negative for GETV and TAHV, demonstrating a good sensitivity, specificity, and performance at CSF specimen detection.

Seasonal pattern of daily activity of Aedes caspius, Aedes detritus, Culex modestus, and Culex pipiens in the Po Delta of northern Italy and significance for vector-borne disease risk assessment.

The increasing concern about vector-borne diseases such as West Nile disease in northern Italy motivated our analysis of data on the mosquito fauna and the seasonal and daily flight patterns collected in 1998 in the Po Valley. Collections were performed once a week from May to November, with human landing collections and CO(2) traps. Culex pipiens was present from July to October and showed a clearly unimodal nocturnal flight habit. Culex modestus appeared in July-August and showed a bimodal flight pattern, (main peak during the evening and a minor one in the morning). Aedes caspius was present from May to November (highest densities in July-August) and showed a bimodal flight pattern with a major crepuscular peak and a minor dawn peak in the morning. Aedes detritus was the most abundant species in May, with a crepuscular sharply bimodal flight pattern, particularly according to human landing collections. Sunset and sunrise time, in combination with the solar phase (that determines daylight duration and its trend of changing) were the main factors affecting flight behavior. Temperature, relative humidity, and wind speed differently affected the flight behavior of mosquito females according to the species.

Distribution of mosquitoes and mosquito-borne arboviruses in Yunnan Province near the China-Myanmar-Laos border.

Economic development and increased tourism in the southern region of Yunnan Province in China, adjacent to several countries in Southeast Asia, has increased the likelihood of import and export of vectors and vector-borne diseases. We report the results of surveillance of mosquitoes and mosquito-borne arboviruses along the border of China-Myanmar-Laos in 2005 and 2006, and information associating several arboviruses with infections and possibly disease in local human populations. Seventeen mosquito species representing four genera were obtained, and 14 strains of mosquito-borne viruses representing six viruses in five genera were isolated from Culex tritaeniorhynchus. In addition, IgM against Japanese encephalitis virus, Sindbis virus, Yunnan orbivirus and novel Banna virus was detected in acute-phase serum samples obtained from hospitalized patients with fever and encephalitis near the areas where the viruses were isolated. This investigation suggests that Japanese encephalitis virus, Sindbis virus, and lesser-known arboviruses circulate and may be infecting humans in the China-Myanmar-Laos border region.

Diagnóstico laboratorial da dengue: situação atual e perspectivas / Dengue laboratory diagnosis: actual situation and perspectives

0 diagnóstico da infecção pelo vírus da dengue é baseado, em grande parte dos casos, apenas no exame clínico do paciente, já que somente alguns poucos grandes centros possuem laboratórios clinicos que disponibilizam testes diagnósticos para confirmar sintomas clinicos de infecção. Atualmente, o diagnóstico laboratorial da dengue pode ser feito por diferentes tipos de testes. Entre eles estao os métodos de pesquisa sorológica, de isolamento viral, de detecção de antigenos virais e do genoma viral. 0 desenvolvimento continuado de testes diagnósticos baratos, sensíveis, especificos e de fácil execucção, que sejam capazes de proporcionar diagnóstico precoce da infecção pelos virus da dengue, é ainda uma necessidade. Existem também outros obstáculos que nao são especificamente relacionados ao desenvolvimento tecnológico dos métodos diagnósticos. Por exemplo, a infra-estrutura dos laboratórios, o treinamento do pessoal técnico e a capacidade de pesquisa ainda são limitados em muitas partes do Brasil e do mundo, onde a dengue é endêmica. Laboratórios clinicos, principalmente os que atendem às regiões de maior incidência da dengue, devem se interar de todos os métodos diagnósticos disponíveis para a rotina atualmente e definir qual se adapta melhor às suas condições de trabalho e população atendida, com o intuito de salvarvidas.

The diagnosis of the infection caused by the dengue virus relies in most cases on the clinical examination of the patient, since only a few major centers have clinical laboratories providing diagnostic tests to confirm the clinical symptons of infection. Currently, routine laboratory diagnosis can be done by different kinds of testing. Among them the methods ofserological research, virus isolation, detection of viral antigens and of viral genome are included. The continued development of diagnostic tests that are cheap, sensitive, specific, easy to perform, and that are capable of giving early diagnosis of the dengue virus infection is still a need. There are also other obstacles not specifically related to the technological development ofdiagnostic methods. For instance, the laboratories' infrastructure, the workers training and the research capacity are still limited in many parts of Brazil and the world, where dengue is endemic. Clinical laboratories, specially those situated in regions with high incidence of dengue, should be aware of all the diagnostic methods available four routine nowadays, and choose the best one that fulfills their working conditions and populations served, in order to save lives.

Rapid assessment of mosquitoes and arbovirus activity after floods in southeastern Kansas, 2007.

A rapid assessment was conducted in July-August 2007 to determine the impact of heavy rains and early summer floods on the mosquitoes and arbovirus activity in 4 southeastern Kansas counties. During 10 days and nights of collections using different types and styles of mosquito traps, a total of 10,512 adult female mosquitoes representing 29 species were collected, including a new species record for Kansas (Psorophora mathesoni). High numbers of Aedes albopictus were collected. Over 4,000 specimens of 4 Culex species in 235 species-specific pools were tested for the presence of West Nile, St. Louis, and western equine encephalitis viruses. Thirty pools representing 3 Culex species were positive for West Nile virus (WNV). No other arboviruses were detected in the samples. Infection rates of WNV in Culex pipiens complex in 2 counties (10.7/1,000 to 22.6/1,000) and in Culex salinarius in 1 county (6.0/1,000) were sufficiently high to increase the risk of transmission to humans. The infection rate of WNV in Culex erraticus was 1.9/1,000 in one county. Two focal hot spots of intense WNV transmission were identified in Montgomery and Wilson counties, where infection rates in Cx. pipiens complex were 26/ 1,000 and 19.9/1,000, respectively. Despite confirmed evidence of WNV activity in the area, there was no increase in human cases of arboviral disease documented in the 4 counties for the remainder of 2007.

Cost effectiveness of three arbovirus surveillance methods in northern California.

We compared the cost effectiveness of enzootic arbovirus surveillance in northern California by antibody detection in sentinel chickens, virus isolation from mosquitoes, and antibody detection in wild avian hosts. Total and annual recurring costs were determined for each method based on estimated personnel and actual material and travel costs for biweekly surveillance at 3 sites in the Sacramento Valley from May 1 through mid-October 1997 and 1998. Serologic detection of antibodies in wild birds was the most expensive method. Total costs associated with sentinel chickens and mosquitoes combined were less than half of those for the wild bird program. Recurring annual costs for the wild bird and mosquito methods were only slightly less than expenses for those methods during the 1st year of operation, which included nonrecurring setup costs. Recurring costs for sentinel chickens were reduced approximately 40% from total costs during the 1st year of the program and were <14% of recurring costs for wild bird serology. Exceptions and caveats of our analysis are discussed. When considering data from a companion paper on detection of enzootic virus transmission using the 3 methods, we concluded that the current system that combines sentinel chickens and virus isolation from mosquitoes is the most cost-effective and efficient surveillance program and should be retained. Future research efforts should investigate the costs and surveillance efficiency of modifications in the frequency of specimen collection and the placement of chicken flocks and mosquito traps.

Economic comparison of enzyme immunoassay and virus isolation procedures for surveillance of arboviruses in mosquito populations.

Cost-effectiveness analysis of an enzyme immunoassay (EIA) for the surveillance of arboviruses was conducted. The EIA was compared with conventional virus isolation and serologic identification procedures (virus isolation procedures; VIP). Under most circumstances, EIA was more cost-effective than VIP. Costs for processing mosquito pools by VIP increased with the number of viruses included in the surveillance program and with the prevalence rate of each virus. In contrast to VIP, the prevalence rate did not affect costs for processing pools by EIA. In general, EIA was the most cost-effective procedure, followed by cell culture and mouse bioassays. In a 5-year cost-effectiveness analysis of a model surveillance program in which EIA and cell culture bioassays were used, the EIA again proved to be the most cost-effective assay procedure under most circumstances.

Multiple assessment and serum neutralization of arbovirus mixtures.

Mixtures of Venezuelan equine encephalomyelitis, Rift Valley fever, and chikungunya viruses may be assayed by selective immunofluorescence staining of infected cell monolayers. A multiple serum neutralization test is described for quantifying reactions of these viruses with mixtures of serum antibodies.

Direct assessment of viral aerosols on cell cultures.

A technique is described for the direct exposure of cell cultures to airborne virus enabling quantitation of the virus in concentrations as low as one plaque-forming unit per liter of air.