Seroepidemiology of rickettsial infections in Northeast India.
Resurgence of scrub typhus was reported in Northeast India in 2010 after a gap of 67 years since World War II. However, the presence of other rickettsial infections remained unknown from this region. A seroepidemiological investigation was undertaken in the scrub typhus affected areas from 2013-2015 in Assam, Arunachal Pradesh and Nagaland to assess the exposure to other rickettsial diseases besides scrub typhus.



Samples were collected from people residing in scrub typhus reporting areas. Serology was performed by an indirect ELISA for the three rickettsial agents' viz., scrub typhus group orientiae (STGO), spotted fever group rickettsiae (SFGR) and typhus group rickettsiae (TGR). A sample with total net absorbance ≥1.000 was considered as positive. An entomological survey was also carried out in the affected areas.



Overall, 1265 human blood samples were collected, of which 30.8% (n=390), 13.8% (175) and 4.2% (53) had antibodies against STGO, SFGR and TGR respectively. Presence of antibodies against more than one of the rickettsial groups was also detected. Among the arthropods collected, chiggers of Leptotrombidium deleinse, fleas belonging to Ctenocephalides felis and Pulex irritans, ticks belonging to Rhipicephalus microplus, Haemaphysalis spp. were predominant. Candidatus Rickettsia senegalensis was detected in C. felis.



Our findings confirm wide circulation of rickettsial infections and their probable vectors in the northeast region of India.Accession numbers: KU163367, KU163368, KU499847, KU499848.
Regional Medical Research Centre (ICMR), N.E. Region, Post Box no. 105, Dibrugarh-786001, Assam, India sirajkhanicmr@gmail.com.
Siraj Ahmed
SA
Khan
Regional Medical Research Centre (ICMR), N.E. Region, Post Box no. 105, Dibrugarh-786001, Assam, India.
Trishna
T
Bora
Naval Medical Research Center, Silver Spring, Maryland 20910-7500 USA.
Suchismita
S
Chattopadhyay
Naval Medical Research Center, Silver Spring, Maryland 20910-7500 USA.
Ju
J
Jiang
Naval Medical Research Center, Silver Spring, Maryland 20910-7500 USA.
Allen L
AL
Richards
Regional Medical Research Centre (ICMR), N.E. Region, Post Box no. 105, Dibrugarh-786001, Assam, India.
Prafulla
P
Dutta
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007194:India / Q000453:epidemiology; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D012281:Rickettsia / Q000145:classification; D012282:Rickettsia Infections / Q000453:epidemiology* / Q000276:immunology / Q000382:microbiology; D012612:Scrub Typhus / Q000453:epidemiology* / Q000276:immunology / Q000382:microbiology; D016036:Seroepidemiologic Studies; D005423:Siphonaptera / Q000382:microbiology*; D000073605:Spotted Fever Group Rickettsiosis / Q000453:epidemiology / Q000276:immunology / Q000382:microbiology; D013987:Ticks / Q000382:microbiology*; D014324:Trombiculidae / Q000382:microbiology*; D014438:Typhus, Epidemic Louse-Borne / Q000453:epidemiology / Q000276:immunology / Q000382:microbiology; D055815:Young Adult
D000907:Antibodies, Bacterial
Antibodies; Northeast India; Orientia; Rickettsia; Seroepidemiology