加藤 大智

BACKGROUND: With the launch of Sri Lanka's National Strategic Plan for leishmaniasis control, case diagnosis has been identified as a key strategic intervention. However, the routine slit-skin smear (SSS) demonstrates variable sensitivity (33-78%), underscoring the need for rapid and sensitive diagnostic tools. This study evaluated the diagnostic performance of a newly developed nanoparticle-based anti-rKRP42 (recombinant kinesin-related protein antigen-42) IgG immunochromatographic test (rKRP42-ICT) for detecting cutaneous leishmaniasis caused by Leishmania donovani. METHODS: A cross-sectional pilot study was conducted among 58 adults with clinical CL at Base Hospital Tangalle. CL was confirmed by SSS (reference test). Serum from CL patients and Japanese negative controls was tested using rKRP42-ICT, rKRP42 IgG ELISA, and rK39-ICT. Diagnostic performance of the ICT (sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV)) was calculated against SSS. Clinical associations were analysed by Chi-square, and ELISA OD means were compared using non-parametric tests (with 95% confidence interval). RESULTS: The majority of the CL cohort (62%) were male. The mean duration at presentation was 5.1 months. Most had single, small (< 2 cm) lesions, with ulcers being the commonest type (41%). rKRP42-ICT demonstrated a positive rate of 43.1% among the clinical CL cohort while SSS and rK39-ICT positivity was 55.2% and 5.2%, respectively. The rKRP42-ICT showed 43.8% sensitivity, 57.7% specificity, and 56% PPV and 45.5% NPV against the reference test. The rKRP42-ICT could detect positive samples across a wide range of ELISA OD values, from 0.017 to 2.535. rKRP42-ICT positivity correlated with higher ELISA OD values (p < 0.05), but SSS positivity did not. The rKRP42-ICT and SSS agreement was slight (Kappa = 0.014). Negative controls (n = 43) were negative by both ICTs. Male gender, ulcerated, large (> 2 cm), and multiple lesions were associated with higher rKRP42-ICT positivity (p < 0.05) and higher mean ELISA OD values. Defining confirmed cases as clinical CL with either SSS or rKRP42-ICT positivity increased case detection from 55.2 to 74.1% (20%). CONCLUSIONS: The rKRP42 IgG-based ICT showed promise as a supplementary diagnostic tool for CL, potentially improving overall case detection beyond routine microscopy and providing rapid results for clinical decision-making. With further optimization and validation, it may support national diagnostic and surveillance efforts.

Ticks are major public health vectors that rely on long-term extravascular feeding, a process critically dependent on establishing a subcutaneous blood pool. While tick salivary molecules suppress host hemostasis and immunity, the precise mechanism by which vascular integrity is compromised to sustain massive hemorrhage in the deep dermis, outside the tick hypostome's reach, remains a longstanding enigma. Using time-series pathological and multiplex immunohistochemical analyses in a mouse model infected with Haemaphysalis longicornis tick, we redefined the blood pool not as a cystic reservoir, but as a severe inflammatory lesion characterized by massive, diffuse extravasation of red blood cells. We observed that ticks induce pathological angiogenesis, forming fragile microvessels. Crucially, the formation of neutrophil extracellular traps (NETs), known as NETosis surged in clustering neutrophils on Day 3 of feeding, coinciding with the transition to massive hemorrhage. Furthermore, extravasated platelets co-localized with NETs in the hemorrhagic tissue. We propose a sophisticated parasitic strategy, whereby the tick hijacks host immunothrombosis to mediate massive hemorrhage. The dysregulated interaction between NETs and platelets drives a vicious inflammatory cycle, which destroys the fragile, newly formed vasculature and extracellular matrix. This process establishes a blood-soaked, sponge-like stroma, which the tick exploits for efficient blood intake. Our findings redefine the fundamental mechanism of tick feeding success.

BACKGROUND: In tropical to subtropical regions, centipede bites may prompt medical attention, with manifestations largely reflecting venom-related discomfort, although infections, including rare fatal necrotizing soft tissue infection (NSTI), have been reported. However, no reports are available on the commensal bacteria on centipede forcipules. OBJECTIVES: This study aimed to investigate bacterial species residing on and in centipede forcipules and their potential role in post-bite infections. METHODS: Nine Scolopendra mutilans, three Scolopendra japonica, and two Bothropolys rugosus were collected from three regions in Japan. The bacterial composition of their forcipules was analyzed using 16S ribosomal ribonucleic acid gene sequencing and microbiome analysis. FINDINGS: A diverse bacterial community was observed on the centipede forcipules. Among the NSTI-associated genera examined (Escherichia, Staphylococcus, and Streptococcus), only Staphylococcus was identified as a minor population. CONCLUSION: This study provides the first evidence that some bacteria found on centipede forcipules have been previously isolated from centipede bite infections. The risk of infection from bacteria on centipede forcipules during a centipede bite appears low. However, the presence of diverse bacterial species emphasizes the importance of thoroughly cleaning centipede bite wounds to prevent secondary infection.

Anopheles mosquitoes spread malaria, which is caused by Plasmodium parasite infection. In nature, both male and female mosquitoes typically ingest sugars from floral nectar; however, few studies have investigated the effects of sugars as an insecticide for mosquitoes. During our previous work, the lifespan of An. stephensi was shortened by the feeding of high concentrations of lactose. The mechanism by which lactose can shorten the lifespan of mosquitoes is still unidentified. The present study aims to evaluate the potential of lactose as an insecticide against mosquitoes. A sublethal concentration of lactose decreased the lifespan of An. stephensi but did not affect their blood-feeding ratio or the number of eggs they laid. Female Anopheles mosquitoes refused to ingest lactose-containing sugars when a lactose-free sugar is available; however, male mosquitoes ingest them. Both sexes excreted lactose from their bodies after feeding, while other sugars were completely absorbed and digested. An ingestion volume assay using food dye revealed that lactose reduces the volume of the solution in the mosquito body. Female mosquitoes forced to ingest lactose for 3 wk showed a slight change in the composition of their midgut microbiota but not in their relative quantity. These findings suggest that lactose feeding causes osmotic diarrhea-like symptoms in Anopheles mosquitoes. The use of attractive toxic sugar baits with lactose as an insecticide is expected to control male Anopheles mosquitoes.

Dogs are the main reservoir host of Leishmania infantum, etiological agent of zoonotic visceral leishmaniasis (ZVL). An effective vaccine against Canine Visceral Leishmaniasis (CVL) will help the control and elimination of ZVL. In this study, we evaluated in dogs the safety, immunogenicity, and efficacy of a live attenuated Leishmania major Centrin gene-deleted (LmCen-/-) as a vaccine. Two doses (106 or 107) of LmCen-/- vaccine were administered intradermally in a prime-boost regimen. Both vaccine doses induced equally high level of IgG anti-Leishmania and exhibited strong antigen-specific cellular responses with IFN-γ production by CD4 + T cells one-month post-immunization. A second cohort of dogs was vaccinated with 106 LmCen-/- parasites one month prior to their transfer to a CVL endemic focus in Northern Tunisia for exposure to sand fly bites during three successive transmission seasons. Dogs were exposed to bite from naturally infected sandflies for 3-5 months per year. Our results showed that only 1/11 vaccinated dogs became PCR positive for Leishmania and developed clinical signs of CVL. In contrast, 4/11 unvaccinated dogs were tested PCR positive for Leishmania and displayed oligosymptomatic CVL, demonstrating that immunization with LmCen-/- vaccine confers long-term protection with an efficacy of 82.5% against CVL in natural transmission settings.