Journal of Vector Borne Diseases最新文献

Background objectives: Leishmaniasis is a major global public health concern but current control measures are unreliable. Vaccination is likely the best control method, but despite efforts to develop a vaccine, none has been approved for human use. This study evaluated the antileishmanial potential of a vaccine combining 2,6,10,14-tetramethylpentadecane (pristane) as an adjuvant plus soluble Leishmania major antigens (SLmAgs) in BALB/c mice.

Methods: Mice were randomly assigned to four groups and treated as: group 1 - SLmAgs + pristane; group 2 - SLmAgs alone; group 3 - BCG + SLmAg (positive control) and group 4 - phosphate buffered saline (negative control). At 31 days post-vaccination, immune response was assessed by measuring the production of interleukin-10 (IL-10); interferon-gamma (IFN-γ) and CD4+/CD8+ T cells using flow cytometry. Protection against cutaneous leishmaniasis was determined after infecting the mice with virulent L. major promastigotes (at 31 days post-vaccination) and measuring the footpad lesion size and determining parasite loads in infected footpads using the limiting dilution assay at 45 days post infection.

Results: Following vaccination with SLmAgs + pristane as an adjuvant, the mice produced higher amounts of Th 1 cytokine- IFN-γ compared to Th2 cytokine IL-10 and a significantly higher amount of CD4+ compared to CD8+ T cells, with corresponding smaller lesion sizes and lower parasite loads.

Interpretation conclusion: The findings in this study demonstrate the potential of pristane as an adjuvant for antileishmanial vaccines, effectively inducing protective Th1 responses. However, safety assessments, dosage optimization and evaluation in non-human primates are recommended to confirm its suitability and enhance vaccine efficacy.

The cases reported the clinical characteristics and viral kinetics of DEN-1 and DEN-4 in two cases of congenital dengue. We describe two neonates born to mothers with recent dengue infections, highlighting their clinical presentation, serological progression and outcomes. Both neonates had early onset of symptoms, with one tested positive for DEN-4 and the other for DEN-1. Both experienced thrombocytopaenia without signs of haemoconcentration and recovered uneventfully. Congenital dengue, although rare, should be considered in neonates with fever and other suggestive symptoms in dengue-endemic areas. The two reported cases are unique in that both had congenital dengue fever with different serotypes, yet demonstrated prolonged NS1 antigen positivity and delayed seroconversion.

Background objectives: Determining the host seeking and resting behaviours of malaria vectors in a locality is vital for the design and implementation of locally adapted vector control strategies. This study investigated the seasonal abundance, host seeking, and resting behaviours of malaria vectors in localities where insecticide-treated nets (ITNs) and indoor residual spraying (IRS) are persistently used in Mazowe and Shamva districts.

Methods: Anopheles mosquitoes were sampled from both living and non-living structures using CDC light traps, Prokopack aspirator, and artificial pit traps in April, July, October, and December 2023. Female Anopheles were identified using morphological keys. R software was used for data analysis. The Kruskal-Wallis test was used to assess differences in the abundance of female Anopheles across collection methods, while a negative binomial Generalized Linear Mixed Model (GLMM) was used to determine the effect of study site, season, and type of structure on the abundance of female Anopheles mosquitoes.

Results: Overall, 787 female Anopheles were caught, comprising An. gambiae sensu lato (s.l.) (33%), An. funestus s.l. (17.4%) and others (49.6%). Relative abundance of female Anopheles mosquitoes based on collection method showed significant difference (Kruskal-Wallis: X2 = 42.33, df = 3, p < 0.001). There were significantly more female Anopheles mosquitoes caught in Shamva district (p = 0.023), during the post-rainfall season (p < 0.001), in traditional-style bedrooms (p < 0.001) and grass thatch toilets (p = 0.045). Notable proportions of An. gambiae s.l. were caught seeking hosts pre-bedtime outdoors (19%) and early morning outdoors (14.3%), and An. funestus s.l. pre-bedtime indoors (14.5%) and early morning outdoors (10.9%). High percentages of An. gambiae s.l. (51.1%) and An. funestus s.l. (35.6%) were caught from non-living structures that lack insecticide treatment.

Interpretation conclusion: Malaria vectors are circumventing current control measures by biting people when they are not protected by ITNs and resting in outdoor areas or indoor structures where insecticides are not applied. Supplementary interventions, including larval source management (LSM) and repellents, are required to reduce the risks of residual malaria transmission.

Background objectives: This study aimed to systematically review the effectiveness of plant-based bioinsecticides in controlling Aedes aegypti larvae, the primary vector of dengue, Zika, and chikungunya. It also sought to explore formulation innovations, identify implementation challenges, and propose directions for future research. A scoping review was conducted following the PRISMA guidelines to ensure comprehensive and structured analysis.

Methods: A literature search was performed in PubMed, ScienceDirect, and Scopus for peer-reviewed articles published between 2020 and 2025. Keywords related were used. Data extraction included study characteristics, plant species, compound type, formulation, concentration, and larvicidal outcomes.

Results: Out of 1,142 identified records, 225 articles were assessed in full, and 21 studies met the final inclusion criteria. Results showed that plant-based bioinsecticides, particularly those using active compounds such as azadirachtin, citronella, and capsaicin, demonstrated significant larvicidal efficacy. Nanoparticle formulations and combinations of multiple plant extracts exhibited higher potency and faster larval mortality rates at lower concentrations.

Interpretation conclusion: Plant-based bioinsecticides present a promising eco-friendly alternative to synthetic insecticides. Effectiveness varies with extraction methods and formulation types. Modern approaches, such as nanoformulations and synergistic plant combinations, enhance larvicidal potential. Future studies should focus on optimizing formulation techniques and validating efficacy through field trials for sustainable vector control.

Visceral leishmaniasis (kala-azar) is caused by a protozoan parasite of genus Leishmania. India and neighboring countries comprise the largest focus of VL. Moderate to higher degree of fever accompanied by rigor and hepatosplenomegaly is the most typical clinical picture. We present a case of 50 years old male from Bhadohi (Uttar Pradesh) with high grade fever for 2 months without hepatosplenomegaly. On evaluation, there was bicytopenia with hyper-gammaglobulinemia. Work-up for tropical fever, tuberculosis, chronic viral etiologies and multiple myeloma was negative. Further evaluation on lines of fever of uncertain cause showed amastigote forms of Leishmania donovani (LD bodies) in bone marrow aspiration smears. Serology test rk-39 was positive. Thus final diagnosis of visceral leishmaniasis (kala-azar) with the atypical presentation without splenomegaly was made. Fever totally resolved in a week of starting treatment and blood parameters improved at 1 month follow-up. As definite treatment options are available, duration of illness and case fatality rate can be reduced by timely detection of atypical cases.

Background objectives: Vector-borne diseases have had a profound global impact causing millions of deaths each year. Essential oils (EOs) offer a promising alternative due to their natural properties. The EO collected from Pulicaria wightiana (DC.) C.B. Clarke was tested for its toxicity against the early life stages of three important vectors of diseases.

Methods: Concentrations of 3.125, 6.25, 12.5, 25 and 50 ppm were tested for their mosquitocidal properties.

Results: The EO from P. wightiana displayed 100% ovicidal mortality against Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti eggs at 50 ppm concentration within 24 hours; it was similar to that of temephos the positive control. Strong mosquitocidal toxicity was observed, with LC50 values of 8.22, 13.27 and 10.80 ppm for larvae of Culex, Anopheles and Aedes, respectively at 24 hours. Caryophyllene oxide (22.44) and D-Limonene (19.08) were the main components in the EO accountable for the observed mosquitocidal toxicity. Toxicity studies indicated that the EO from P. wightiana did not adversely affect the tested predators. Additionally, the EO-mediated formulation presented strong ovicidal (100%) and larvicidal (89-95%) activities with no toxicity to natural predators such as Gambusia affinis and Poecilia reticulata at 24 hours.

Interpretation conclusion: These findings underscore the significance of plant-derived EO from P. wightiana as environmentally friendly and effective tool in combating mosquito-borne diseases, especially in regions facing resource constraints.

Background objectives: Mosquito-borne diseases such as malaria, dengue, zika, chikungunya, and filaria severely affect the health and economy of the countries which are endemic to these diseases. With the revolution in technology, insecticidal paint has been used in to control mosquitoes and other pests in developed countries.

Methods: In Indian market, several of water and oil-based surface coating paints are available that somehow also affect mosquito longevity.

Results: Among these paints, we have selected a few brands for the present study and observed that the water-based paint brand (WBP1) was found to be more potent in reducing vector density with KD50: 9.89, 13.09, 15.75, and 19.69 min; KD90: 25.59, 36.88, 38.88, 60.55 min with 92.5, 75, 75 and 30% mortality after the time period of 3, 30, 60, and 90 days respectively. In another brand paint (WBP2), knockdown time found to be KD50: 8.28, 9.86, 20.84 and 33.83 min; KD90: 24.53, 29.48, 49.55, 81.95 min with mortality of 90, 67.5, 16.66 and 5% after time duration of 3, 30, 60 and 90 days respectively. Oil based paint (OBP1) also found to be mosquitocidal with KD50: 12.11, 19.03, 27.48 and 37.36 min; KD90: 31.74, 53.19, 67.97, 81.38 min having 75, 70, 20 and 10% mortality in the time duration of 3, 30, 60 and 90 days after treatment.

Interpretation conclusion: This study might help open a window for sustainably controlling mosquito borne diseases.

Background objectives: Dengue virus (DENV), a Flaviviridae member, poses a global health challenge due to the absence of effective antiviral therapies. The viral nonstructural protein 5 (NS5), responsible for RNA synthesis and methylation, is a validated drug target. This study aimed to identify potential chalcone-based inhibitors of the NS5 methyltransferase domain.

Methods: Forty chalcone derivatives from the PubChem database were docked against the NS5 methyltransferase domain (PDB ID: 6KR2). The top six compounds were evaluated for drug-likeness (SwissADME) and toxicity (ProTox-II). Electronic properties were assessed using Density Functional Theory (DFT).

Results: Six chalcones showed better binding affinities (≥-7.0 kcal/mol) than the reference ligand S-adenosylhomocysteine (SAH, -6.2 kcal/mol), interacting effectively with the SAM-binding pocket. BL-1 had the strongest docking score (-7.8 kcal/mol) but showed toxicity concerns. BL-3 emerged as the most promising, with strong binding (-7.4 kcal/mol), excellent drug-likeness, low toxicity, and good synthetic accessibility. DFT analysis revealed that BL-4 had the lowest energy gap (ΔE = 3.59 eV), indicating high reactivity, while BL-3 had a stable HOMO (-6.45 eV) and a moderate energy gap (ΔE = 4.22 eV), suggesting a favorable balance of reactivity and stability.

Interpretation conclusion: BL-3 shows strong potential as an NS5 methyltransferase inhibitor due to its optimal binding, safety profile, and electronic properties. It is recommended for further lead optimization and experimental validation as a candidate anti-DENV agent.

Background objectives: Conventionally, the humoral immune response to scrub typhus (ST) is the early appearance of IgM during the first week of infection, followed by IgG after 2-3 weeks. Recent publications reveal different trends in Immunological response to ST.

Methods: Acute and convalescent blood from 55 (Group-I) and single samples from 152 (Group-II), both clinically suspected as ST, were subjected to ST IgM ELISA, ST IgG ELISA, and ST IgG IFA. Acute samples from Group I and single samples from Group II were subjected to Real-Time PCR (q PCR) to target three genes, 56 kDa, 47 kDa, and groEl.

Results: All 262 blood samples were positive for ST IgM ELISA. Positivity for IgG ELISA, IgG IFA and the presence of any one or more gene targets (56kDa/47kDa/groEL) in qPCR among the 55 acute samples was 70.9%, 36.4%, and 89.1%, respectively and 87.3%, 45.5% and 78.3% respectively in convalescent samples. In 152 unpaired samples, IgG ELISA was positive in 52.6% and 19.1% in ST IgG IFA. Among 207 samples (Group-I Acute and Group II) subjected to q PCR, groEl, 56 kDa and 47 kDa were present in 59.4%, 44.0%, and 35.7% respectively.

Interpretation conclusion: In view of the persistence of IgM in ST over months and, in some cases, years, there is a diagnostic dilemma in confirming ST based on single ST IgM, especially in ST-endemic regions. This is compounded by the additional presence of ST IgG in the early days of acute infection. q PCR is recommended to confirm doubtful cases of ST.

Background objectives: Arinta and Erin-Ijesha are popular waterfalls in Southwest Nigeria where preliminary assessments identified blackfly activity, yet data on vector dynamics and Onchocerca infectivity remain unavailable. This study investigated these parameters to assess the risk of onchocerciasis transmission at both sites.

Methods: Adult blackflies were collected for three consecutive days in a month by two dark complexioned adult male human landing catchers from September 2023 to August 2024. For each hour of sampling, 20% of the catches were randomly selected and dissected in real-time to assess parity and infectivity using standard procedure. The remaining flies were morphologically identified as savannah and forest flies and were preserved for O-150 pool screening.

Results: A total of 1090 Simulium flies were caught, Arinta (n=1012) and Erin-Ijesha (n=78). The peak monthly biting rate (MBR) were 3160.0 (Arinta, September) and 289.3 (Erin-Ijesha, October) bites/person/month while the lowest MBRs were 72.3 (Arinta, July) and 0.0 (Erin-Ijesha, January to March, May, July and August) bites/person/month. The MBR at Arinta was significantly higher than at Erin-Ijesha (p=0.02). The Annual biting rate (ABR) at Arinta (10,231.8 bites/person/year) exceeded the WHO threshold of 1000 bites/person/year, while below at Erin-Ijesha (790 bites/person/year). All morphologically examined flies were identified as forest species. No Onchocerca infectivity was detected in dissected or pool-screened (n = 857) flies.

Interpretation conclusion: Findings suggest low risk of onchocerciasis transmission at both waterfalls, with blackflies merely constituting biting nuisance. Continued public health education of tourist is recommended to allay their fears on the public health risk posed by blackfly bites, along with the use of protective clothing and repellents.