Journal of Vector Borne Diseases最新文献

Backgrounds objectives: Recent research in Cameroon reported several occurrences of dengue in urban settings, but concurrent dengue-malaria infection has received less attention, particularly in the East region.

Methods: A two-month cross-sectional and comparative research was performed at Bertoua Regional Hospital which included 50 malaria-positive participants and 90 non-malaria subjects. Participants were selected and provided with a questionnaire to collect sociodemographic data. Blood samples were collected and tested for dengue infection and hematological parameters were assessed.

Results: Dengue fever was found in 14% of malarial patients vs 66.66% of controls. Secondary dengue infection was more prevalent in malarial patients than in non-malarial patients. Gender, age, and place of residence were positively correlated to dengue seropositivity. Platelets were substantially lower (P<0.001) in the malarial group than in the non-malarial group.

Interpretation conclusion: In the study, coinfected patients were found to be more vulnerable to dengue, emphasizing the importance of epidemiological surveillance.

Background objectives: Widespread pyrethroid resistance and plastic-feeding behaviour of most malaria vectors across Africa threaten the efficacy of current insecticide-based vector control interventions like Insecticide-Treated Nets (ITNs) and Indoor Residual Spraying (IRS). This study examined the larvicidal activity ofMorinda citrifolia against Anopheles gambiae larvae and the repellent properties of Morinda citrifolia (Noni), Moringa oleifera (Moringa), and Ocimum basilicum (Basil) as complementary vector control tools against Anopheles gambiae sensu lato (s.l.).

Methods: Noni, Basil, and Moringa oil extracts were obtained with the extraction techniques; Soxhlet, steam distillation and maceration respectively, using hexane and ethanol. The effectiveness of the extracts was assessed using the WHO standard larval susceptibility bioassay and guidelines for repellent efficacy. Following bioassays, effective doses (ED) and lethal concentrations (LC) were determined. Gas Chromatography-Mass Spectroscopy analysis was performed to identify the bioactive chemical components of the extracts of Moringa oleifera and Ocimum basilicum.

Results: Emulsified Morinda citrifolia seed oil had LC50=68.3, LC90=130.9 and LC99.9=222.5, and ED99. 9=308.3%v/v, the ethanolic extract of Moringa oleifera leaves had ED99.9= 1.25g/ml, and essential oil of Ocimum basilicum leaves had ED99.9=0.28g/ml against Anopheles gambiae.

Interpretation conclusion: The results obtained indicated that seed oil of Morinda citrifolia, essential oil of Ocimum basilicum, and crude extract of Moringa oleifera have repellent activity against An. gambiae s.l. The complete protection time (CPT) of Morinda citrifolia, Moringa oleifera, and Ocimum basilicum was 120 min, 72 min and 84 min at ED99.9 respectively. Morinda citrifolia oil exhibited larvicidal effects against the larvae of An. gambiae s.l. The results provide valuable information for the use of the plants as biocides.

Background objectives: In urban areas, upsurge in population has resulted in more breeding sites for malaria vectors, and hence this scenario potentially undermine malaria elimination and control programs. The change in land use due to urbanization may result in the presence and distribution of malaria vectors. Understanding potential malaria vectors is essential for current and future malaria transmission control strategies. This study investigated the effects of rapid urbanization on malaria vectors An. culicifacies s.l. and An. stephensi L. in Ghaziabad district.

Methods: Ghaziabad district which presents several levels of urbanization was selected for this study. Entomological investigations were conducted seasonally from 2014-2016 in the rural, urban, and peri-urban regions. Vector incrimination study was done using ELISA (confirmation by PCR) on suspected Anopheles vectors viz. An. culicifacies, An. stephensi, An. annularis and An. subpictus.

Results: An. culicifacies showed alteration in distribution influenced by rural and agricultural land whereas An. stephensi was found to be influenced by artificial habitats and population growth.

Interpretation conclusion: The study also confirms the association between the abundance of malaria vectors and land use change.

Background objectives: This study reports observation on circulating serotypes and genotypes of Dengue Virus in North India.

Methods: Serum samples were obtained from suspected cases of dengue referred to the virus diagnostic laboratory during 2014 to 2022. All samples were tested for anti-dengue virus IgM antibodies and NS1Ag by ELISA. NS1Ag positive samples were processed for serotyping and genotyping.

Results: Total 41,476 dengue suspected cases were referred to the laboratory of which 12,292 (29.6%) tested positive. Anti-Dengue Virus IgM antibodies, NS1Ag, both IgM and NS1Ag, were positive in 7007 (57.4%); 3200 (26.0%) and 2085 (16.0%) cases respectively. Total 762 strains were serotyped during 9-year period. DENV-1, DENV-2, DENV-3 and DENV-4 serotypes were found in 79 (10.37%), 506 (66.40%), 151 (19.82%) and 26 (3.41%) cases respectively. DENV-1, DENV-2 and DENV-3 were in circulation throughout. Total 105 strains were genotyped. Genotype IV of DENV-1 serotype was circulating till 2014 which was later replaced by genotype V. A distinct seasonality with increase in number of cases in post-monsoon period was seen.

Interpretation conclusion: DENV-1, DENV-2 and DENV-3 were found to be in circulation in North India. Predominant serotype/genotype changed at times, but not at regular intervals.

Background objectives: Insect growth regulators (IGRs) are biological hormone analogue or mimics used as pesticides to inhibit the growth of larva during their molting and skin shedding. This study aimed to test the effect of IGRs on the eggs hatching and post-hatching inhibition of Aedes mosquitoes and understanding its effect in the mosquito breeding habitats for reduction in adult emergence.

Methods: Experiments on the evaluation of three insect growth regulators (IGRs) for the control of different stages of Aedes aegypti was carried out during 2020-21. Each experiment consisted of four treatments viz., Pyriproxyfen, Novaluron, and Larvicol at 1.0 ppm and distilled water as a control. All experiments were carried out in completely randomized design (CRD) except eggs which were carried out in factorial design each with three replications.

Results: All tested IGRs performed better in affecting eggs, larval and pupal stages of Ae. aegypti. Highest eggs hatching inhibition (80%) of fresh eggs occurred in Pyriproxyfen followed by Novaluron (66%) and lowest in Larvicol (62%). Eggs hatch inhibition of embryonated eggs was lower than fresh eggs. Pyriproxyfen caused 69%, Novaluron 59% and Larvicol 39% eggs hatch inhibition of embryonated eggs. Both Pyriproxyfen and Novaluron performed better in causing 98-100% larval mortality followed by Larvicol (39%). Larval development to pupal stage was completely prevented by both Pyriproxyfen and Novaluron. Although Larvicol resulted in lowest eggs hatch and larval inhibition but prevented pupae to emerge as adults. Results further showed 70-89% mortality of 3rd instar larvae of Ae. aegypti when exposed to Pyriproxyfen and Novaluron solutions after 30 days storage at lab. temperature (27±2°C), RH 70±5.

Interpretation conclusion: None of the IGRs was more effective at the pupal stage but showed carry-on activity of growth inhibition and mortality of the successive stages of development when used against eggs stages. Therefore, we recommend early application of IGRs at mosquito habitats during the beginning and onset of the season when very early stages of mosquitoes are available in the field.

Background objectives: Mosquitoes alone transmit diseases to around 700 million individuals annually, killing approximately 0.7 million people every year worldwide. Considering the potential health risks linked with synthetic repellents, it has become vital to identify eco-friendly, natural repellents for mosquito control as well as to understand the underlying mechanism for mosquito repellent activity. To address this, objectives were set to extract essential oils from Citrus macroptera peel and Homalomena aromatica (Spreng.) Schott. rhizomes, evaluate their mosquito repellent activity against Aedes aegypti, and further explore their mosquito odorant receptor inhibition potential.

Methods: The oils were extracted using Clevenger's apparatus, and properties like specific gravity, refractive index, and boiling point were evaluated and characterised using Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectroscopy (GC-MS). Aedes aegypti mosquito eggs collected from the Indian Council of Medical Research (ICMR), Dibrugarh, were reared in the Department of Pharmaceutical Sciences, Research Laboratory, to obtain adult Aedes aegypti mosquitoes for the mosquito repellent activity evaluation of the essential oils using the Human Bait technique'. Molecular docking studies were performed for the oil components against mosquito odorant binding proteins. Further, toxicity studies of these two oils were evaluated against human dermal fibroblast adult (HDFa) cells.

Results: The results revealed the presence of limonene (86.76%) and linalool (52.35%), respectively, in Citrus macroptera and Homalomena aromatica oils. It was found that the combination of the oils in a ratio of 1:1 showed mosquito repellent activity for up to 6.33 ± 0.23 h. Molecular docking studies showed the presence of major oil components having mosquito odorant receptor blocking potential comparable to N, N-diethyl-meta-toluamide (DEET), indicating a rationale for extended mosquito repellent action. Further, both of these oils were found to be non-cytotoxic against HDFa cells after 24 h.

Interpretation conclusion: The encouraging mosquito repellent activity of these two oils as compared to synthetic mosquito repellent DEET might pave the way for the development of novel herbal mosquito repellent formulations containing these essential oils.

Background objectives: Dengue and chikungunya infections are one of the major health problems that have plagued the human population globally. All dengue virus (DENV) serotypes circulate within Malaysia with particular serotypes dominating in different years/outbreaks. In the state of Kelantan, an increasing number of DENV and chikungunya virus (CHIKV) new cases have been reported, including several deaths. This study aimed to isolate and detect these arboviruses from adult mosquitoes in Kelantan.

Methods: Adult mo squito samples were collected from January to August 2019 and were identified according to gender, species and locality. The isolation of the virus was done in C6/36 cells. Dengue NS1 antigen was carried out using direct mosquito lysate and mosquito culture supernatant. Detection and serotyping of the DENV was performed using multiplex RT-PCR and CHIKV detection using a one-step RT-PCR assay.

Results: Of 91 mosquito pools, four were positive for NS1 antigen comprising two pools (2.2%) of male Ae. albopictus (Pulau Melaka and Kubang Siput) and two pools (2.2%) of Ae. aegypti (Kampung Demit Sungai). DENV 1 was detected in one pool (0.9%) of female Ae. albopictus among 114 tested Aedes pools. Two pools of 114 pools (1.7%) from both male Aedes species were positive with double serotypes, DENV 1 and DENV 2 (Pulau Melaka). However, no pool was positive for CHIKV.

Interpretation conclusion: The presence of DENV and the main vectors of arboviruses in Kelantan are pertinent indicators of the need to improve vector controls to reduce arbovirus infections among people in the localities.

Background objectives: Bangladesh is afflicted with periodic dengue outbreak every few years and one of the worst upsurges was recorded in 2019 during which there was an increasing trend of dengue with unusual symptoms which were not so common before. This study aims to describe the experience of three tertiary care centres of Dhaka regarding the clinical and laboratory, hospital outcome and management profile of the Expanded Dengue Syndrome (EDS) cases admitted from the 2019 outbreak.

Methods: The current work was a cross-sectional observational study which took place from August 1 to December 31 2019 at three major tertiary care centres in Dhaka, Bangladesh. Out of total 2017 screened dengue cases, 49 met the inclusion criteria and 39 were enrolled after taking informed written consent. Data was analysed using Microsoft Excel and Graph pad prism 9.3.1. A probability value of p<0.05 was considered statistically significant.

Results: Out of the 39 cases, majority were male (79.49%) with median (±IQR) age of 33(±9) years. Hypertension (4; 10.26%) was the most commonly associated co-morbidity. Among the systemic manifestations, most prevalent was hepatitis (38.49%) followed by encephalopathy (12.82%). Majority of the patients were suffering from primary infection (85%). Case fatality rate was 15.38%. Hepatitis and meningoencephalitis were the predominant cause of death. This study records the only known case report of Acute respiratory dress syndrome (ARDS) complicating dengue from Bangladesh. None of the patients from our cohort were managed by steroids. Only two (5.13%) out of 39 cases received antibiotics.

Interpretation conclusion: In the year 2019, an unusual rise in EDS cases with about 15.4% fatalities were observed in this study. Hepatitis was the most common presentation and cause of death. Here, we report the first ARDS case encountered in Bangladesh. Despite the multifaceted presentation of EDS, indiscriminate use of antibiotics and steroid was minimal. Early recognition of multifarious features of EDS is important for choosing the targeted treatment option which can avert many deaths. The results of this study underline the necessity for more in-depth research into the risk factors that are contributing to mortality in EDS cases.

Background objectives: Kyasanur Forest Disease (KFD) is a tick-borne, zoonotic viral hemorrhagic fever, previously known to be endemic to the state of Karnataka, India. The first outbreak of KFD in Goa state was reported in the Sattari taluka, in North Goa in 2015. This study aimed to investigate the outbreak and report the clinical manifestations and risk factors in people diagnosed with KFD.

Methods: A mixed methods approach was used, which included a case series report and 19 in-depth interviews (IDIs) conducted with people diagnosed with KFD. The recorded IDIs were transcribed and translated and themes were coded for the analysis.

Results: There were 73 suspected cases of which 30 were confirmed to have KFD using RT-PCR. There were four suspected deaths of which two were confirmed by RT-PCR. Most of the affected individuals were found to be dependent on the forest for their livelihood. Most of the people in the region were engaged in cashew plantations and had to travel to the forest to fetch firewood and cashew, hence were at a higher risk. They lived near the forest. The lack of hemorrhagic manifestation was noteworthy in the current outbreak.

Interpretation conclusion: The 'One Health' approach should be implemented to control KFD. Tick bite prevention measures coupled with vaccination of high-risk groups and intensive health education should be carried out, especially before the transmission season. There is a need to have high clinical suspicion for KFD in the region bearing in mind the non-hemorrhagic manifestation in this outbreak.