Molecular detection of Orientia tsutsugamushi in ectoparasites & their small mammal hosts captured from scrub typhus endemic areas in Madurai district, India.

BACKGROUND OBJECTIVES: Scrub typhus, caused by Orientia tsutsugamushi present in small mammals harbouring the ectoparasites. A study was undertaken to detect the pathogen present in small mammals and its ectoparasites in the scrub typhus-reported areas. METHODS: The small mammals (rodents/shrews) and its ectoparasites were screened for O. tsutsugamushi using nested PCR amplification of the groEL gene. Small mammals were collected by trapping and screened for ectoparasites (mites, ticks and fleas) by combing method. RESULTS: All the chigger mites collected were tested negative for O. tsutsugamushi . Interestingly, adult non-trombiculid mites ( Oribatida sp., Dermanyssus gallinae ), fleas ( Xenopsylla astia, X. cheopis, Ctenophalides felis and Ctenophalides sp.) and ticks ( Rhipicephalus sanguineus , R. haemaphysaloides ) screened were found to be positive for O. tsutsugamushi , which the authors believe is the first report on these species globally. Bandicota bengalensis with O. tsutsugamushi infection is reported for the first time in India. The O. tsutsugamushi groEL sequences from the positive samples were similar to the reference strains, Karp and Ikeda and phylogenetically clustered in clade IV with less evolutionary divergence. The blood samples of Rattus rattus , Suncus murinus and B. bengalensis collected from this area were tested positive for O. tsutsugamushi ; interestingly, the sequence similarity was much pronounced with their ectoparasites indicating the transmission of the pathogen to host or vice versa . INTERPRETATION CONCLUSIONS: The outcome of the present investigations widened our scope on the pathogens present in ectoparasites and rodents/shrews from this area. This will help to formulate the required vector control methods to combat zoonotic diseases.

Current status of mites and mite-borne diseases in India.

Mites act as the vectors of zoonotic vector-borne disease scrub typhus caused by the rickettsial pathogen Orientia tsutsugamushi. In India, scrub typhus is transmitted by the mite Leptotrombidium deliense. Rodents are the reservoirs and support the spread of this disease. Sarcoptes scabiei or the itch mite is causing scabies which is a common skin infection in India. Dermatitis, trombiculosis, and mite dust allergy are common mite-borne diseases transmitted by Pyemotidae family. D. brevis folliculorum and Demodex brevis are two major mite species found on humans also causing a disease; "Demodicosis", common in India. Dermanyssus gallinae, fowl mite causes pruritis in poultry birds, transmits infections to poultry workers when they come into contact with birds. There is a re-emergence of mite-borne diseases, especially scrub typhus, in many parts of India requiring urgent attention for its control. This review is aimed to update the available information on mites and mite transmitted diseases prevalent in India to highlight the importance of rodent and chigger mite vector control to prevent forthcoming mite-borne diseases in India.

A review of public health important fleas (Insecta, Siphonaptera) and flea-borne diseases in India.

Fleas (Insecta, Siphonaptera) are important vectors of plague and murine typhus in many parts of the world. Currently, about 2700 flea species were described in the world. The most common vector flea Xenopsylla cheopis is found throughout India, but X. astia, and X. brasiliensis are found less and limited in distribution associated with the domestic rats such as Rattus rattus, R. norvegicus, Mus musculus, and Bandicota bengalensis. Bubonic plague is a major flea-borne disease caused by the bacterial pathogen Yersinia pestis, transmitted from rats to humans via the rodent flea, X. cheopis. A major outbreak of plague and high mortality occurred in India. After 1966 with the 3 decadal intervals, plague cases occurred only during the year 1994 reported in 5 different states (Gujarat, Maharashtra, Karnataka, Uttar Pradesh, Madhya Pradesh and New Delhi and subsequently plague cases occurred during 2002 and 2004 after the one-decade interval in Himachal Pradesh (2002). Another outbreak of bubonic plague was reported in Dangud village, Barkhot tehsil, Uttarkashi district, Uttarakhand during October 2004. Ctenocephalides fleas are common in cats and dogs, which are the main vectors of bacteria rickettsiae, such as Rickettsia typhi, R. felis, R. conorii, and Bartonella henselae. Molecular and serological evidence also confirms the presence of R. typhi, R. conorii R. felis and B. henselae pathogens in cats and other fleas in India. Flea bites and flea-borne dermatitis are common in men and pet animals. Because of the re-emergence of the plague, updated information on fleas and flea-borne diseases are essential to control the flea vectors and flea-borne diseases in India. Hence, this comprehensive review updates the available information on fleas and fleas transmitted diseases in India.

Dengue infection among tribal population in the Nilgiris district, Tamil Nadu, India.

BACKGROUND & OBJECTIVES: Dengue emerged as an important public health problem in Tamil Nadu from 2000 onwards, reported in all the districts as an endemic disease of Tamil Nadu except Nilgiris district. So this study was carried out to understand the dengue epidemiology in Nilgiris district. METHODS: Block-wise study was made at the Nilgiris district. The clinicians at the Nilgiris Adivasi Welfare Association hospitals (NAWA) situated in Kotagiri, Kozhikarai and Primary Health Centers from Kunjpannai, Arayoor, and Soloor Mattam, examined and recorded symptoms and collected blood samples from the dengue-suspected patients. These samples were centrifuged at 4°C and stored. Serum samples (267 nos.) collected from dengue-suspected patients for two years period from 2014 to 2016 were screened for dengue infection. RESULTS: First year study conducted during 2014-15 showed 13 dengue positives (8.39%) mainly from Kotagiri block (9 nos. - 69.2%) and the second year study conducted during 2015-16 showed 12 dengue positives (10.71%) found mostly from Udagamandalam block (6 nos.- 50%). People belonging to 6 different tribes - Irular, Toda, Kota, Kurumba, Kattunaickan, and Paniya were found infected with dengue and more Irular positives were recorded in both the years (5 Irular-2014-15 & 11 Irular -2015-16). First year detected more female positives (92.3%) whereas the second year showed 5 males (41.7%) and 7 females (58.3%). INTERPRETATION & CONCLUSION: This study unearthed the hidden disease dengue to be prevalent among the tribal community and emphasized the need for the establishment of a permanent dengue surveillance system with improved disease diagnostics, to initiate effective vector control efforts to stop dengue transmission from this hilly region.

Bdelloid rotifer, Philodina species in the breeding containers of Aedes aegypti and Aedes albopictus.

The vector mosquitoes of dengue and chikungunya fever, Aedes aegypti and Aedes albopictus have adapted to feed on humans and undergo larval and pupal development in natural and artificial freshwater collections. Although several studies reported, still, much information is required to understand the successful survival of Aedes mosquitoes in small temporary containers. In an investigation conducted in the chikungunya affected areas of Kerala state, India, the presence of Bdelloid rotifer, Philodina in 95% of breeding habitats of Ae. aegypti and Ae. albopictus was recorded. The role of Philodina in the breeding containers was investigated. It was found that while in control the number of Philodina was found increasing in the water sample during the study period of seven days, the number found decreased in the containers with larvae of Aedes. The gut content analysis also confirmed the presence of the rotating wheel, corona of Philodina in some of the specimen suggests its role as major larval food.