Emergence of Schoengastiella ligula as the vector of scrub typhus outbreak in Darjeeling: Has Leptotrombidium deliense been replaced.

Background: Following a suspected outbreak of scrub typhus in Kurseong, Darjeeling, the Armed Forces Medical College, Pune was requested by the National Institute of Epidemiology and the State authorities to undertake investigation of the ongoing scrub typhus outbreak and suggest containment measures. Materials and Methods:The epidemic team undertook clinical, entomological and serological studies to understand the local disease pattern and delineate high risk areas, host diversity by rodent trapping using Sherman traps, mite fauna diversity, abundance and vector species identification by phase contrast microscopy for preparation of electronic database and rodent and human serological studies by Weil Felix and PCR. Results:The results indicate no association of scrub typhus with age and sex (P=0.37 and 0.74 respectively). The maximum cases occurred amongst the tea garden workers (73%) in the age group of 25-44 years. The predominant clinical presentation was fever (100%) with headache (75%), lymphadenopathy (45%) and presence of eschar (76.7%). The dominant host species (50% of trapped rodents) was shrew Suncus murinus, the index animal for scrub typhus, which contributed maximally to the vector abundance (52.96%) with a chigger index of 61.56. The trombiculid mite Schoengastiella ligula was the vector species much against the expected mite vector Leptotrombidium deliense, in the area. The study found the presence and abundance of vector species which corroborated well with the occurrence of cases in the various localities within the subdivisions. Conclusion:The study thus establishes Schoengastiella ligula as the vector of scrub typhus outbreak in Kurseong, Darjeeling. Preventive and containment measures with emphasis on reduction of man - vector contact were suggested to the state authorities to contain the outbreak.

Effectiveness of Diflubenzuron in the control of houseflies.

Background & objectives: Houseflies are one of the major pest problems worldwide. The current housefly control strategy in the country hinges on the use of Dichlorvos as a housefly larvicide and pyrethrum spray in kitchens/dining areas. The present study was undertaken to evaluate the newer housefly control options in the wake of concerns about human toxicity of Dichlorvos and its continued use in public health. Methods: Efficacy of Diflubenzuron WP and granule formulations (chitin synthesis inhibitor) visà- vis Dichlorvos EC in the control of housefly was assessed in laboratory by adult emergence inhibition after treatment and in field conditions by estimation of density post-application up to three weeks using standard methods. Results: Dichlorvos EC and Diflubenzuron formulations (WP and granule) brought about 100% inhibition of adult emergence under laboratory conditions. However, in the field evaluation, effective suppression of housefly population was brought about by Dichlorvos and Diflubenzuron granule formulation (though delayed). Conclusion: Dichlorvos EC and Diflubenzuron granule formulation are effective housefly larvicides. It is recommended that Diflubenzuron WP formulation be evaluated at a higher frequency to enhance its effectiveness and its use may be considered in conjunction with an initial suppression of housefly adults with an adulticide, e.g. Cyphenothrin, etc.