Seroprevalence & seroincidence of Orientia tsutsugamushi infection in Gorakhpur, Uttar Pradesh, India: A community-based serosurvey during lean (April-May) & epidemic (October-November) periods for acute encephalitis syndrome

Abstract

Background & objectives: In India, acute encephalitis syndrome (AES) cases are frequently reported from Gorakhpur district in Uttar Pradesh. Scrub typhus is one of the predominant aetiological agents for these cases. In order to delineate the extent of the background of scrub typhus seroprevalence and the associated risk factors at community level, serosurveys during both lean and epidemic periods (phase 1 and phase 2, respectively) of AES outbreaks were conducted in this region. Methods: Two community-based serosurveys were conducted during lean (April-May 2016) and epidemic AES (October-November 2016) periods. A total of 1085 and 906 individuals were enrolled during lean and epidemic AES periods, respectively, from different villages reporting recent AES cases. Scrub typhus-seronegative individuals (n=254) during the lean period were tested again during the epidemic period to estimate the incidence of scrub typhus. Results: The seroprevalence of Orientia tsutsugamushi during AES epidemic period [immunoglobulin (Ig) IgG: 70.8%, IgM: 4.4%] was high as compared to that of lean AES period (IgG: 50.6%, P <0.001; IgM: 3.4%). The factors independently associated with O. tsutsugamushi positivity during lean AES period were female gender, illiteracy, not wearing footwear, not taking bath after work whereas increasing age, close contact with animals, source of drinking water and open-air defecation emerged as additional risk factors during the epidemic AES season. IgM positivity was significantly higher among febrile individuals compared to those without fever (7.7 vs. 3.5%, P =0.006). The seroincidence for O. tsutsugamushi was 19.7 per cent, and the subclinical infection rate was 54 per cent. Interpretation & conclusions: The community-based surveys identified endemicity of O. tsutsugamushi and the associated risk factors in Gorakhpur region. The findings will be helpful for planning appropriate interventional strategies to control scrub typhus.

Rickettsial infections: A blind spot in our view of neglected tropical diseases

“…However, multiple published fever and seroprevalence studies, and associated meta-analyses, attest that rickettsial infections, particularly scrub typhus and murine typhus, constitute a major disease burden in many parts of the world [ 7 , 8 ] as great or greater than many of the diseases already on the World Health Organization (WHO) and PLOS Neglected Tropical Diseases lists. Seroprevalence studies in Bangladesh, India, Indonesia, Laos, Malaysia, Papua New Guinea, and Sri Lanka yielded rates for Orientia tsutsugamushi exposure of between 9.3% and 51.6% [ 7 , 9 ]. In a review of acute febrile illness studies in India, scrub typhus was found to be the cause of illness in 16.1% to 47.5% of incident patients, and a rate of 96.9% in an investigation of an outbreak of fever of unknown origin in Arunachal Pradesh [ 7 ].…”

Outbreak prone communicable diseases of public health importance in the northern districts of West Bengal – Current status & the way forward

“…Among India, Bangladesh, Nepal and Bhutan, only Bhutan has declared ST as a notifiable disease so far. Community and hospital based serosurveillance reports are available from these four countries providing evidence of endemicity of ST 8 10 42 43 44 . Similar reports are also available for Assam and Bihar 45 46 .…”

“…A community based study among febrile persons in Gorakhpur showed a seropositivity of 19.7 per cent against O. tsutsugamushi 42 Reports on annual incidence of ST in the five North Bengal districts and the total incidence in the State were obtained from 2018 to 2020. Personal communications of the physicians at Mirik Rural and Kurseong sub-divisional hospitals in Darjeeling district on estimated incidence of clinical ST cases encountered and managed revealed more than 200 cases annually from 2018 to 2020.…”

“… i awareness to be increased on ST being an important cause for AES and AFI in the region and capacity building of the healthcare providers on early detection and management of ST; ( ii ) use of empirical treatment of clinically suspected ST cases with doxycycline/azithromycin, as applicable, to prevent delayed treatment and complications prior to laboratory confirmation; ( iii ) promotion of personal protective measures including avoiding woods/forests/shrubs, wearing protective clothing and gumboots to work, use of mite repellents and insecticide treated clothes during work, avoiding sitting on grass or shrubs, bathing after work and changing clothes, rearing cattle away from home, avoiding close contact with peri-domestic animals and strict avoidance of open-air defecation 18 42 ; ( iv ) Institution of rodent control measures and proper disposal of dead rodents 17 ; ( v ) The State Health department may consider the following: providing facilities for Weil-Felix test (which is not cost intensive) for confirmation of ST in the primary and secondary tier hospitals in the high risk areas, which have no ELISA facility for IgM testing. This would help early confirmation of ST cases and early referral of complicated cases issuing of order declaring ST as a notifiable disease so that there is a comprehensive capture of data on ST to help understand the true burden of the disease and plan appropriate public health action strengthening disease surveillance (case based reporting, reporting of all cases – lab confirmed as well as clinically suspected cases and efforts to get all suspected cases tested for confirmation) in the region given its strategic location, the heavy population movement and it being a tourist destination, business hub and gateway to the North Eastern States of the country Undertaking epidemiological, entomological, and sero-surveillance studies in different parts of the State to identify the local risk factors, the predominant vertebrate hosts and vector mites and the endemicity of O. tsutsugamushi to help plan appropriate interventional strategies involving different non-health sectors to prevent and control ST 42 . …”

“…awareness to be increased on ST being an important cause for AES and AFI in the region and capacity building of the healthcare providers on early detection and management of ST; ( ii ) use of empirical treatment of clinically suspected ST cases with doxycycline/azithromycin, as applicable, to prevent delayed treatment and complications prior to laboratory confirmation; ( iii ) promotion of personal protective measures including avoiding woods/forests/shrubs, wearing protective clothing and gumboots to work, use of mite repellents and insecticide treated clothes during work, avoiding sitting on grass or shrubs, bathing after work and changing clothes, rearing cattle away from home, avoiding close contact with peri-domestic animals and strict avoidance of open-air defecation 18 42 ; ( iv ) Institution of rodent control measures and proper disposal of dead rodents 17 ; ( v ) The State Health department may consider the following:…”