Occurrence of Orientia tsutsugamushi, the Etiological Agent of Scrub Typhus in Animal Hosts and Mite Vectors in Areas Reporting Human Cases of Acute Encephalitis Syndrome in the Gorakhpur region of Uttar Pradesh, India Candasamy Sadanandane, Purushothaman Jambulingam, Kummankottil P. Paily, Narendran Pradeep Kumar, Ayanar Elango, Kulandaisamy Athisaya Mary, Sundararajan Agatheswaran, Thirumal Sankari, and Bhuwan Bhaskar Mishra Abstract Outbreaks of acute encephalitis syndrome (AES) with high fatality and disability, are reported every year in the Gorakhpur region of Uttar Pradesh, India, with the etiology of >60% of the cases being attributed to scrub typhus. In the present study, the prevalence of Orientia tsutsugamushi, the etiological agent of scrub typhus, was in- vestigated among animal hosts and their ectoparasitic trombiculid mites prevalent in AES-reported areas of Gorakhpur. A total of 154 rodents/shrews were collected using 777 Sherman traps set in 12 study villages, and the overall trap rate was 19.8%. In total, 2726 trombiculid mites belonging to 12 species were collected from 154 rodents/shrews trapped. The shrew mouse Suncus murinus was the predominant animal species (78.6%) collected. The principal vector mite Leptotrombidium deliense was the predominant species (82.7%), and its index was 14.6 per animal. Of 114 rodent/shrew sera samples screened through the Weil–Felix test, 57% were positive for antibodies against O. tsutsugamushi. Of 128 blood samples tested by polymerase chain reaction (PCR), one rodent sample was positive for the gene encoding 56 kDa protein and 25 for 60 kDa. Among 2726 mite samples tested as 315 pools through nested PCR, seven pools were positive for 56 kDa gene. Phylogenetic analysis confirmed circulation of Gilliam, Karp, and TA678 serotypes of O. tsutsugamushi in Gorakhpur. The study clearly dem- onstrated natural infection of O. tsutsugamushi in both small-animal hosts and vector mites in the AES-reporting villages of Gorakhpur, which confirms transmission of the scrub typhus pathogen in this region. The high infestation rate of L. deliense with O. tsutsugamushi infection indicates that the people living in the rural villages of Gorakhpur are at risk of infection with scrub typhus, which might lead to AES. Keywords: Orientia tsutsugamushi, Leptotrombidium deliense, Suncus murinus, scrub typhus, acute encephalitis syndrome, India Introduction O utbreaks of acute encephalitis syndrome (AES) with high mortality and disability have been reported from several states in India, including Assam, Bihar, Karna- taka, Tamil Nadu, and Uttar Pradesh (Borah et al. 2011, Sa- minathan et al. 2013). About 70–75% of the case reports were from Uttar Pradesh, particularly from the Gorakhpur division of the state (Ranjan et al. 2014, Murhekar et al. 2016). Japanese encephalitis ( JE) has been considered as a major cause of AES problem in this region (Ranjan et al. 2014). In Gorakhpur di- vision, JE vaccine was introduced in two rounds of mass vaccination campaign in 2006 and 2010 and in the routine immunization program in 2011. However, analysis of 2002– 2012 AES surveillance data indicated that only 8% of the cases were due to JE, while the etiology of majority of cases remains largely unknown (Ranjan et al. 2014). A recent in- vestigation, conducted by Kasturba Medical College, Mani- pal, India, indicated scrub typhus as a major etiological factor, with 60% of AES cases showing positive reaction in the test ICMR-Vector Control Research Centre, Department of Health Research, Ministry of Health and Family Welfare, Government of India, Puducherry, India. VECTOR-BORNE AND ZOONOTIC DISEASES Volume XX, Number XX, 2018 ª Mary Ann Liebert, Inc. DOI: 10.1089/vbz.2017.2246 1 Downloaded by Tufts University package NERL from www.liebertpub.com at 07/19/18. For personal use only.