Mosquito-borne Tropical Disease Research Articles

Commercial Enzyme-Linked Immunosorbent Assay Kit Is Useful for Detection of Recombinant and Secretory Nonstructural-1 Protein Antigen of Dengue Virus.

Background: Dengue is a mosquito-borne tropical disease, caused by the Dengue virus (DENV). It has become a severe problem and is a rising threat to public health. In this study, we have evaluated commercial Merilisa i Dengue NS1 Antigen kit (Meril LifeSciences India Pvt. Ltd.) to detect recombinant dengue virus 2 NS1 antigen (rDNS1Ag) and secreted forms of NS1 antigen (sDNS1Ag). Methods: To determine the detection limit of the kit, 100 nanogram (ng) to 0.001 ng rDNS1Ag was tested. The sensitivity and specificity of the kit was determined using recombinant NS1 antigens of all serotypes of DENV and other flaviviruses. For testing sDNS1Ag, the culture supernatant of the Vero cell lines infected with DENV-2 was tested. Further, a spiking experiment was carried out to check the sensitivity of the kit to detect rDNS1Ag in the pools of Aedes aegypti mosquitoes. Results: It was observed that the kit can detect the rDNS1Ag at 1 ng concentration. The kit was sensitive to detect NS1 antigen of DENV-1, DENV-2 and DENV-3 serotypes and specific for detection of only DNS1Ag as it did not cross-react with NS1 antigen of flaviviruses. The kit was sensitive to detect rDNS1Ag in the mosquito pools as well. In addition, the kit was able to detect the sDNS1Ag in Vero cell culture supernatant. Conclusions: Overall, we observed that the Merilisa i Dengue NS1 Ag kit is sensitive and specific for the detection of DNS1Ag both in recombinant and secretory forms.

Surveillance and Control of Malaria Vectors in Hainan Province, China from 1950 to 2021: A Retrospective Review

Malaria is a serious mosquito-borne tropical disease impacting populations in tropical regions across the world. Malaria was previously hyperendemic in Hainan Province. Due to large-scale anti-malarial intervention, malaria elimination in the province was achieved in 2019. This paper reviews the literature on the ecology, bionomics, and control of malaria vectors in Hainan from 1951 to 2021. We searched PubMed, and the China national knowledge infrastructure (CNKI) database for relevant articles published and included three other important books published in Chinese or English in order to summarize research on species, distribution, vectorial capacity, ecology, the resistance of malaria vectors to insecticides, and malaria vector control in Hainan Province. A total of 239 references were identified, 79 of which met the criteria for inclusion in our review. A total of six references dealt with the salivary gland infection of Anophelines, six with vectorial capacity, 41 with mosquito species and distribution, seven with seasonality, three with blood preference, four with nocturnal activity, two with flight distance, 13 with resistance to insecticides, and 14 with vector control. Only 16 published papers met the criteria of addressing malaria vectors in Hainan over the last 10 years (2012-2021). Anopheles dirus and Anopheles minimus are primary malaria vectors, mainly distributed in the southern and central areas of Hainan. Indoor residual spraying with DDT and the use of ITNs with pyrethroid insecticides were the main interventions taken for malaria control. Previous studies on ecology, bionomics, and resistance of vectors provided scientific evidence for optimizing malaria vector control and contributed to malaria elimination in Hainan Province. We hope our study will contribute to preventing malaria reestablishment caused by imported malaria in Hainan. Research on malaria vectors should be updated to provide scientific evidence for malaria vector control strategies post-elimination as the ecology, bionomics, and resistance of vectors to insecticides may change with changes in the environment.

Dengue prediction using time series forcasting I.E ARIMA model

Dengue fever is a mosquito-borne tropical disease caused by the dengue virus. It is a life threatening disease lots of person died due to dengue because its symptoms are not detected at early stages many parson thought that it was a normal fever or headache so that they just ignore it which cause there are in danger situations and in worst case they loss their life.

3D-printing of the polymer/insect-repellent system poly(l-lactic acid)/ethyl butylacetylaminopropionate (PLLA/IR3535)

The polymer/solvent system poly(l-lactic acid)/ethyl butylacetylaminopropionate (PLLA/IR3535) is regarded as an insect-repellent-delivery system, serving, e.g., for fighting mosquito-borne tropical diseases. In such systems the solid polymer hosts the liquid repellent, with the latter slowly released to the environment, expelling mosquitoes. As a new approach, exceeding prior work about application of different technologies to obtain such devices, in this work, samples of the polymer/repellent system PLLA/IR3535 were prepared by 3D-printing. The experiments showed that it is possible to print 3D-parts containing up to 25 m% repellent, with an only minor loss of repellent during the printing process. For samples containing low amount of repellent, crystallization of PLLA was suppressed due to the rather fast cooling step and the low bed temperature of around 25 °C, being lower than the glass transition temperature of the homogeneous polymer/repellent strands. At higher repellent concentration, due to the lowering of the glass transition temperature to near or even below ambient temperature, the crystallinity slowly increased during storage after printing. For all samples, regardless of the initial repellent concentration, the repellent-release rate increases with temperature, and at ambient temperature the release-time constant is in the order of 10 days. The study successfully proved the applicability of the technology of extrusion-based 3D-printing for the preparation of polymer parts with a specific shape/design containing mosquito-repellent at a concentration which raises the expectation to be used as a repellent delivery-device.

Analysis of exhaled breath for dengue disease detection by low-cost electronic nose system

This paper presents a procedure and a set-up of an electronic nose system analyzing exhaled breath to detect the patients suffering from dengue – a mosquito-borne tropical disease. Low-power resistive gas sensors (MiCS-6814, TGS8100) were used to detect volatile organic compounds (VOCs) in the exhaled breath. The end-tidal phase of patients exhaled breath was collected with a BioVOCTM breath sampler. Two strategies were assessed for breath samples measurement: either direct transfer from the BioVOCTM into the sensors test chamber, or storage in Tenax TA sorbent tubes followed by VOCs release through thermal desorption and then transfer into sensors test chamber. DC sensor resistances were recorded and processed by multivariate classifier algorithms to detect infected patients. The experimental studies were run on a group of 26 individuals (16 dengue diagnosed patients and 10 control volunteers). The detection accuracy of dengue patients was over 90%.

Rhamnolipids and essential oils in the control of mosquito-borne tropical diseases.

The diseases transmitted by mosquito vectors are a great public health issue. Thus, effective vector control becomes the main strategy to reduce their prevalence. However, insecticide resistance has become a huge concern for the mitigation of mosquitoes; here, we propose the use of rhamnolipids in emulsion with clove oil against Aedes aegypti and Culex quinquefasciatus. The toxicity of rhamnolipids and clove oil to two species of mosquitoes transmitting tropical diseases was investigated. After 24h, the LC50 was 140mg/L when rhamnolipids were used and 154mg/L when clove oil was used against Aedes aegypti larvae. In the case of Culex quinquefasciatus, the LC50 was 130mg/L for rhamnolipids and 19mg/L for clove oil. When the concentrations of the upper limits of one of the solutions (rhamnolipid or clove oil) were mixed, 100% mortality was obtained after 24h. The bioassay of insecticidal action for solutions of rhamnolipids and clove oil in the lower limit, upper limit, and lethal concentration 50 to determine the effect on 50% of the population (KD50) achieved low results from KD50 to the upper limit compared to the other concentrations for both Aedes aegypti and Culex quinquefasciatus. The rhamnolipids and clove oil at the upper limit concentration had the greatest repellent activity against the two mosquito species. Bioassays using different concentrations of rhamnolipids revealed variations in the morphology of the intestinal epithelium (800mg/L). A concentration of 900mg/L led to the most severe morphological changes in the organization of the epithelium and the cells lining the intestines of these larvae. When larvae were exposed to a concentration of 1000mg/L, the marginalization of chromatin in the nucleus of epithelial cells was very severe, indicating the onset of cell death.Key points• The toxicity of rhamnolipids and clove oil has a larvicidal, insecticidal, and repellent effect.• The combination of concentrations of these compounds enhances their action.• Different concentrations of rhamnolipids led to severe morphological changes in the organization of the epithelium and the cells and the intestines of larvae.

CARICA PAPAYA LEAF EXTRACT FOR TREATING THROMBOCYTOPENIA IN DENGUE FEVER- AN EXPERIENCE FROM A TERTIARY CARE CENTRE IN EASTERN PART OF INDIA

Background: Dengue fever is the most common arboviral mosquito-borne tropical disease of humans caused by the dengue virus. The incidence has increased many fold in India due to unplanned urbanization and migration of population to urban areas. Aim -To study if Carica papaya leaf extract will significantly increase the platelet count in cases of thrombocytopenia associated with Dengue fever. Materials and Methods- The case control study was conducted in the Department of Medicine of Tata Main Hospital,Jamshedpur.All participants were randomised into two groups, study group (n=50) and control group (50); the study group was given papaya leaf extract capsule of 1100 mg thrice daily for five days but the control group did not receive it. The basic supportive treatment of dengue fever was provided to both the groups. Results- On the first day,platelet count of study group and control group was (63.68 ± 16.88, 3 and 57.07 ± 17.46×10 respectively, p value=0.0573). The mean platelet count on Day 2, Day 3, Day 4 of CPC 3 3 3 administration (mean± S.D) was 80.34 ± 18.54×10 ,104.14 ± 20.42×10 ,135.08 ± 19.91×10 in the case group and 64.48 ± 3 3 3 17.02×10 ,77.02 ± 16.88×10 ,100.70 ± 18.33×10 in the control group respectively.The mean duration of stay in the study group was 4.6± 0.67 days and 6.76±1.54 days in the control group (p<0.01). Conclusion- Carica papaya leaves extract capsules offer a cheap and possibly effective treatment for increasing the platelet count in dengue

A study on the usefulness of band form count as a marker of severity in dengue fever

Background: Dengue fever is a mosquito borne tropical disease caused by dengue virus. Clinical features of dengue fever are varied and ranges from asymptomatic to life threatening shock and death. A set of investigations is used in the monitoring of the disease apart from the tests done for confirmation. No single test is the gold standard in the evaluation of dengue patients that can be used as marker of clinical severity and fatality. Aim of this study is to evaluate the usefulness of band form count as a marker of severity in dengue fever. Materials and Methods: Peripheral smears are made for all dengue cases confirmed with Immunochromatography test for NS1, IgM and IgG. The cases were categorised in to clinically stable dengue fever patients and severe dengue based on their clinical findings. The band form count was done by manual differential count. The correlation between band form count and clinical severity was assessed. A total of 124 cases were studied that included 23 cases of severe dengue. Results: A significant relationship between band form count and clinical severity was obtained. 22/23 cases of severe hemorrhagic fever had significant increase in band form count of above 20%. All the other cases diagnosed as dengue fever had band form count Conclusion: Hence, band form count can be used in the set of investigations used in the evaluation of patients with dengue fever to assess the severity of the disease. Considering its role in assessing the severity, further research is required to evaluate the usefulness in the evaluation and management of patients with severe dengue. Keywords: Dengue, Severe dengue, Severe dengue hemorrhagic fever, Bandemia, Band forms.

Dynamic proteomic analysis of Aedes aegypti Aag-2 cells infected with Mayaro virus

BackgroundMayaro virus (MAYV) is responsible for a mosquito-borne tropical disease with clinical symptoms similar to dengue or chikungunya virus fevers. In addition to the recent territorial expansion of MAYV, this virus may be responsible for an increasing number of outbreaks. Currently, no vaccine is available. Aedes aegypti is promiscuous in its viral transmission and thus an interesting model to understand MAYV-vector interactions. While the life-cycle of MAYV is known, the mechanisms by which this arbovirus affects mosquito host cells are not clearly understood.MethodsAfter defining the best conditions for cell culture harvesting using the highest virus titer, Ae. aegypti Aag-2 cells were infected with a Brazilian MAYV isolate at a MOI of 1 in order to perform a comparative proteomic analysis of MAYV-infected Aag-2 cells by using a label-free semi-quantitative bottom-up proteomic analysis. Time-course analyses were performed at 12 and 48 h post-infection (hpi). After spectrum alignment between the triplicates of each time point and changes of the relative abundance level calculation, the identified proteins were annotated and using Gene Ontology database and protein pathways were annotated using the Kyoto Encyclopedia of Genes and Genomes.ResultsAfter three reproducible biological replicates, the total proteome analysis allowed for the identification of 5330 peptides and the mapping of 459, 376 and 251 protein groups, at time 0, 12 hpi and 48 hpi, respectively. A total of 161 mosquito proteins were found to be differentially abundant during the time-course, mostly related to host cell processes, including redox metabolism, translation, energy metabolism, and host cell defense. MAYV infection also increased host protein expression implicated in viral replication.ConclusionsTo our knowledge, this first proteomic time-course analysis of MAYV-infected mosquito cells sheds light on the molecular basis of the viral infection process and host cell response during the first 48 hpi. Our data highlight several mosquito proteins modulated by the virus, revealing that MAYV manipulates mosquito cell metabolism for its propagation.

Detection of dengue virus in Eastern India

Background: Dengue fever is a mosquito-borne tropical disease caused by the dengue virus. Symptoms typically begin three to fourteen days after infection. The virus has four serotypes; infection with one type usually gives lifelong immunity to that type, but only short-term immunity to the others. Subsequent infection with different dengue virus increases the risk of severe complications. A number of tests are available to confirm the diagnosis including detection via Dengue NS1Ag Microlisa and Dengue IgM/IgG Microlisa antibody by ELISA Method. Methods: There are three methods followed in particular to detect the dengue virus: (A) Dengue NS1 AG Microlisa is designed for in-vitro qualitative detection of Dengue NS1 antigen in human serum or plasma and is used as a screening test for testing of collected blood samples suspected for DENGUE. This method detects all four subtypes; DEN1, DEN2, DEN3 & DEN4 of Dengue Virus. (B) Dengue IgM Microlisa designed for in-vitro qualitative detection of Dengue IgM Antibody in human serum or plasma and is used as a screening test for testing of collected’ blood samples suspected for DENGUE. This method also detects all four subtypes; DEN1, DEN2, DEN3 & DEN4 of Dengue Virus. (C) Dengue IgG Microlisa designed for in vitro qualitative defection on Dengue IgG antibody in human serum / plasma. Duration – 6 months – July, August, September, October, November, December 2019 at KPC Medical College and Hospital, Kolkata West Bengal. Results: Among 1860 dengue samp1es, 420 sâmp1es were found to be NS1Ag positive 160 samples were found to be IgM positive and 24 samples were found to be IgG positive. Rest Samples negative for all three parameters. Conclusion: Dengue is a mosquito borne viral infection causing a severe flu like illness and sometimes causing a potentially lethal complication called severe dengue. The incidence of dengue has increased 30 fold over the last 50 years. Up to 50-100 million infections are now estimated to occur annually in over 100 endemic countries, putting almost half of the world’s population at risk. If sever dengue fever can damage the lungs, liver or heart or multiorgan failure. Blood pressure can drop to dangerous levels, causing shock and in some cases death.

Joint Multilevel Model for Analyzing Length of Stay through Competing Endpoints in Dengue Epidemiology

Dengue is a common mosquito-borne tropical disease caused by a virus. It is a life threatening disease since it sometimes leads to death within a short period of time. Multilevel modeling is a form of statistical modeling when data is at different levels. Due to dengue seriousness and risk being more similar for patients within districts than between districts, there is correlation between patients within districts. Thus district has to be taken as a cluster variable. A frequently encountered response in epidemiological studies is the length of Stay (LOS) of a patient, which measures the time until the event of interest occurs. Complexity arises with the different states/destinations of the time event and competing risk modelling is a more appropriate method for handling such states. The association of platelet count and length of stay of a dengue patient leads to the joint modelling approach for analyzing the dengue patients. Formulation criteria for the joint model with clustered data is to link these models through two sub models that is by using the multilevel multinomial logistic model for the LOS of dengue patients with different destinations and multilevel continuous model for the log platelet count. The linkage between two responses was derived by sharing a common random effect. Factors that have an effect on different destinations of LOS are, time indicators, year, age, classification, rainfall, temperature and humidity, while age, sex, classification, year place treated, rainfall, temp and humidity are associated factors for the log platelet count of dengue patients. Moreover, supremacy of joint modelling was proved by the AIC and BIC values over two separate univariate models.

Knowledge and preventive practices on dengue among slum dwellers of middle adulthood in Jhapa district of Nepal

Introduction: Dengue is a mosquito–borne tropical disease which is a major health concern across the globe. The year 2016 was characterized by large dengue outbreak worldwide. In Nepal, the first dengue case was reported in 2004 whereas Nepal had experienced a major outbreak of Dengue in several districts in 2010. Since there is no specific vaccine available, awareness to prevent and control is a must. Objective: This study is aimed to assess the knowledge and preventive practices of dengue among slum dwellers of middle adulthood (40–65years) in Jhapa district of Nepal. Methodology: A descriptive cross–sectional study was conducted from March of 2018. Non–probability purposive sampling technique was applied to collect data among 109 households through face to face interview using semi–structured questionnaire for knowledge and checklist for practice assessment. Then data was analyzed in SPSS version– 20. Total knowledge and practice score were calculated and association between different variables was measured. Result: Maximum 85.3% and 14.7% of the respondent had medium and high knowledge about Dengue respectively. More than half (54%) had poor practice, 41.3% had fair and 4.6% had least (4.6%) of the respondent had good preventive practice. There was association between knowledge, age and occupation of the respondent and preventive practices. Conclusion: Majority of the respondent had medium knowledge level on Dengue while the overall preventive practices were below average. Hence, health education and awareness program can be launched to upgrade existing knowledge and its preventive practices.

Awareness of dengue fever among the parents of children coming to the dental outpatient department – A questionnaire study

Aim: The aim of this study is to establish the awareness of dengue fever among the parents of children coming to dental OutPatient department (OP). Objective: The objective was to design and complete a questionnaire to evaluate the awareness of dengue fever among the parents of children coming to dental OP. Background: The World Health Organization declares dengue to be endemic in South Asia. Dengue fever, also known as breakbone fever, is a mosquito-borne tropical disease caused by the dengue virus. Despite the magnitude of problem, no documented evidence exists on the awareness and preventive methods regarding dengue. This study is conducted to establish awareness, knowledge, and prevention regarding dengue fever among the parents of children coming to dental OP. Reason: To increase the awareness and thereby gaining the knowledge about the signs and symptoms of dengue fever for the early diagnosis and treatment. Materials and Methods: A cross-sectional study was performed among the parents of children coming to dental outpatient department. Around 80 parents were randomly selected for the questionnaire survey study. To assess awareness on dengue, the questionnaire was covered about knowledge on the signs and symptoms, mode of transmission, mosquito bite time, preventive measures, and source of their knowledge. Results and Conclusion: The study shows a low prevalence of sufficient knowledge in the population based on overall knowledge score on dengue. The isolated knowledge on signs and symptoms, prevention is adequate, with preventive measures mainly focused toward protection from mosquito bites.

The Diagnosis of Dengue Disease

This article describes how Dengue fever is a fatal and hazardous disease resulting from the bite of several species of the female mosquito (principally, Aedesaegypti). Symptoms of the dengue fever mimic those of a number of other infectious and/or mosquito-borne tropical diseases such as Viral flu, Chikungunya, and Zika fever. Yet, with dengue fever, human life can be more at risk due to severe depletion of blood platelets. Thus, early detection of dengue disease can ensure saving lives; furthermore, it can help in making a preventive move before the disease progresses to epidemic proportion. Hence, the target of this article is to propose a model for an early detection and precise diagnosis of dengue disease. In this article, three prevalent machine learning methodologies, including, Artificial Neural Network (ANN), Decision Tree (DT) and Naive Bayes (NB) are evaluated for designing a diagnostic model. The performance of these models is assessed utilizing available dengue datasets. Results comparing and contrasting performance of diagnostic models utilizing accuracy, sensitivity, specificity and error rate parameters showed that ANN-based diagnostic model appears to yield better performance measures over both the DT and NB models.

Dengue fatality prediction using data mining

Dengue fever, a mosquito-borne tropical disease caused by the dengue virus is life-threatening. In Malaysia, although necessary control measures have been carried out, the number of dengue fever cases keeps increasing. Among the measures, dengue vector control appears to be the most effective way to control the spread of the dengue virus particularly in Malaysia. The aim of this research is to study the current implementation of dengue outbreak control in Malaysia and predict dengue fever cases using data mining techniques. Real data on dengue fever and weather are collected from the Ministry of Health in its Perak Tengah district office and Perak Meteorological office respectively. Different data mining classification techniques are applied onto these data with the performance of each technique is measured. The results highlight the best performance among techniques used.

Evaluation of Toxicity of Phenolic Compounds Using <i>Aedes aegypti</i> (Diptera: Culicidae) and <i>Artemia salina</i>

Nowadays, dengue fever, a mosquito-borne tropical disease, has become widely distributed in Brazil. In order to prevent such disease, the population of Aedes aegypti mosquito has to be controlled. Then, the aim of this study is to assess the toxicological effects of phenolic compounds against dengue mosquitos. Hence, the larvicidal activity and toxicity of phenolic compounds against Ae. aegypti larvae and A. salina, are evaluated, respectively. The phenolic compounds 2,6-diiodophenol and 4-chloro-2,6-diiodophenol have different toxicity and larvicidal activity. The compound 4-chloro-2,6-diiodophenol shows the highest toxicity for larvae of Ae. aegypti, exhibiting higher toxicity than 2,6-diiodophenol. Although less toxic than Temephos®(organophosphate), the phenolic compounds evaluated by this research, are proved to be effective against Ae. aegypti larvae. This study demonstrates the importance of controlling the dengue mosquito, considering toxicological aspects of phenolic compounds to prevent environmental impacts.

Male mosquitoes make waves in paradise

Invited Commentary on ‘Open release of male mosquitoes infected with a Wolbachia biopesticide: field performance and infection containment’, O’Connor et al. While the ‘neglected’ mosquito-borne tropical diseases dengue and chikungunya often dominate attention, lymphatic filariasis continues to be a threat to over a billion people. The obvious subdivision provided by islands of the south Pacific provide what is arguably low-hanging fruit for a progressive mass-drug-administration program to eliminate this endemic disease, but this has met with surprising difficulty.1 The usual hurdles of ensuring compliance and consistent program implementation contribute, but these are exacerbated by what is apparently a very efficient vector, even at low densities, Aedes polynesiensis. Often hiding in crab holes and rat-gnawed coconut shells, Ae. polysiensis is protected from exposure to insecticides, so unconventional approaches to control are being considered including methoprene-impregnated baits that the crabs ‘auto-disseminate’ to their burrows2 and fabric resting targets.3 Isolated island mosquito populations have traditionally been favorite targets for genetic control strategies, so the combination of a stubborn vector, a significant disease and hundreds of islands makes the south Pacific a perfect target. Stephen Dobson’s lab at the University of Kentucky has exploited this opportunity to explore sexual sterility for control by infecting Ae. polynesiensis with particular Wolbachia endosymbionts. Unlike the population replacement goal of the Australia Ae. aegypti Wolbachia program,4 Dobson’s lab is using Wolbachia solely for the male sterility that occurs when infected males mate with uninfected wild females. A similar approach has been used previously, most dramatically against Culex quinquefasciatus.5 O’Conner et al.6 have now reported the results of a field release of male Ae. polynesiensis infected (via introgression) with an Ae. riversi Wolbachia. This endosymbiont causes bidirectional sexual sterility when mated to wild Ae. polynesiensis. By releasing approximately 100 000 carefully selected males, they were able to demonstrate population suppression on Toamaro atoll (French Polynesia) relative to two control sites. They also demonstrated that the likelihood of males transfering Wolbachia to Ae. polynesiensis, Ae. Aegypti, or Ae. albopictus is, at best, extremely low. Essential to this approach is that females cannot be released (at least in large numbers) since they can cause population replacement rather than elimination. On the scale of production of this experiment, they were able to accomplish this and argue that replacement is not likely regardless. All results were good preliminary demonstrations of safety and efficaciousness. In spite of arguments that population replacement is not likely, stringent removal of females will continue to be necessary until their inability to establish is demonstrated to be a fact. Considering this requirement, the main advantage of bi-directional sexual incompatibility over classical irradiation-based sterile male release may be good mating competitiveness: this was demonstrated. This project revives an approach whose performance must compete head-to-head with other options for producing similar sterile-male effects: classical sterile insect technique and transgenesis. Critical to further development of the technology is the ability to successfully eliminate females on a large scale during production, a technology that is not yet available. However, continued development of such methods as this team has demonstrated should move ahead until their potential in area-wide programs is soundly assessed.

WolbachiastrainwMel induces cytoplasmic incompatibility and blocks dengue transmission inAedes albopictus

Wolbachia inherited bacteria are able to invade insect populations using cytoplasmic incompatibility and provide new strategies for controlling mosquito-borne tropical diseases, such as dengue. The overreplicating wMelPop strain was recently shown to strongly inhibit the replication of dengue virus when introduced into Aedes aegypti mosquitoes, as well as to stimulate chronic immune up-regulation. Here we show that stable introduction of the wMel strain of Drosophila melanogaster into Aedes albopictus, a vector of dengue and other arboviruses, abolished the transmission capacity of dengue virus-challenged mosquitoes. Immune up-regulation was observed in the transinfected line, but at a much lower level than that previously found for transinfected Ae. aegypti. Transient infection experiments suggest that this difference is related to Ae. albopictus immunotolerance of Wolbachia, rather than to the Wolbachia strain used. This study provides an example of strong pathogen inhibition in a naturally Wolbachia-infected mosquito species, demonstrating that this inhibition is not limited to naturally naïve species, and suggests that the Wolbachia strain is more important than host background for viral inhibition. Complete bidirectional cytoplasmic incompatibility was observed with WT strains infected with the naturally occurring Ae. albopictus Wolbachia, and this provides a mechanism for introducing wMel into natural populations of this species.

Discriminant Value of Volume, Conductivity and Scatter Properties of Leucocytes (VCS Technology) for Rapid and Reliable Diagnosis of Malaria and Dengue Fever

Abstract 4731 Introduction:Malaria and dengue are highly prevalent mosquito-borne tropical diseases that share several clinical and haematological features: a peak incidence in the rainy season, presentations with malaise, body ache and high fever, almost invariable thrombocytopenia and a propensity to develop DIC with bleeding and adverse outcomes if neglected or misdiagnosed. They are challenging to differentiate clinically from each other and also from the more common viral infections. Current laboratory tests are relatively time consuming and/or require specialized expertise or equipment. Expected findings of leukopenia and thrombocytopenia may be absent, or the parasites missed, thus delaying the ordering of confirmatory testing and definitive therapy.Beckman Coulter analyzers incorporate VCS technology to quantify morphological characteristics of neutrophils, lymphocytes, monocytes and eosinophils: cell volume by voltage impedance (V); cytoplasmic/nuclear ratio by radiofrequency conductivity (C); and cytoplasmic granularity/nuclear complexity by laser light scatter (S). All these measurements (Mean and Standard Deviations (SD)) are reported as numerical values, called Cell Population Data (CPD) for every sample.VCS has helped improve the diagnosis of malaria and septicaemia in adults and neonates.We compared the VCS parameters in dengue fever, malaria and other febrile illnesses with a view to generate automated factors for the identification of these illnesses. Methods:We studied CBC parameters and VCS indices from 115 malaria patients (diagnosed by blood smear examination and immunochromatographic strip test for the plasmodium LDH and histidine rich protein-2) along with 105 patients with dengue fever diagnosed on positive NS1 antigen or IgM ELISA assays along with 105 control patients referred for testing for febrile illnesses who were negative for both malaria and dengue by all the above tests.We used the originally developed program “EMMA” [Sukhachev DV, Zefirov NS. 10th European Symposium on Structure-Activity relationships: QSAR and molecular modeling. Barcelona, 4–9. 1994:A104] to generate discriminant functions to differentiate between the groups. The program uses combinatorial algorithms of selected parameters for regression equations by a modified stepwise procedure. It allows computation of a number of “best” regression equations with different parameter combinations. Only parameters statistically significantly different between the groups (checked with Mann-Whitney U test) are included in the discriminant functions. The diagnostic performances of various functions thus generated were assessed by ROC curve analysis with calculation of areas-under-the-curves (AUC). Results:The following equations were generated:To discriminate Malaria from Controls:Improved Malaria Factor =-0.473-0.00163*PLT+0.0524*LySDV+0.0302*LySDCTo discriminate Dengue from Controls:Dengue Factor =0.3-0.00183*PLT+0.00619*LY%+0.0335*LySDCTo discriminate Malaria versus Dengue: =5.51+0.0579*MCHC+0.00549*NE%+0.0138*LyMV+0.00956MoMV +0.027*MoSDVThe performance characteristics of these 3 factors are shown in Table 1.Table 1Performance characteristics of the discriminant factors generated for diagnosis of malaria and dengue and distinguishing them from other febrile illnesses.FactorCut-offSensSpecAUC95% Confidence IntervalSignificance level P (Area=0.5)Improved malaria factor>0.55690.488.60.9310.889 to 0.961<0.0001Dengue factor>0.47881.077.10.8370.780 to 0.884<0.0001Malaria versus Dengue Factor>0.60185.191.40.9370.896 to 0.965<0.0001 Conclusions:The parasitic/virological stimuli elicit strong immune responses resulting in leukocyte abnormalities in malaria and dengue that permit their distinction from other causes of fever. Our discriminant functions are easily calculable by LIS and flags thus generated are likely to have a high sensitivity and specificity for dengue and malaria. Our Improved Malaria Factor represents an enhancement over the original result by Briggs et al (In the ROC curves analysis Malaria Factor has AUC = 0.864, cut-off >4.25, Sens 86%, Spec 78%). Since the VCS data are obtained automatically as part of any CBC-diff, these results can greatly improve the detection of serious febrile illnesses in a timely and cost effective manner. Disclosures:No relevant conflicts of interest to declare.