1. Introduction

In the developing parts of the world, sexually transmitted infections (STIs) are among the key sources of health, and financial adversities, causing extensive morbidity, mortality and stigma [1]. A remarkable variation of frequency and prevalence of the four curable STIs, which are syphilis, chlamydia, gonorrhea and trichomoniasis are observed with the spatiotemporal variation [2]. Studies suggest that the prevalence of these four STIs among general people has a range of 0-3.9% in India [3], but the STI burden is considerably higher among key populations having high-risk behaviour like men who have sex with men (MSM), female sex worker (FSW) hijras with transgender, and people who inject drugs (PWID). However, there are inadequate literature till date to report STI burden in Indian key populations and all of the information have not been unified to enlighten the general spatiotemporal tendencies of STI infections in various key or high-risk population. To gain insight of the status of the prevalence and spatiotemporal distribution of four STIs viz. syphilis (by Treponema pallidum), gonorrhea (by Neisseria gonorrhoeae or NG), chlamydia (by Chlamydia trachomatis or CT), and trichomoniasis (by Trichomonas vaginalis or TV) among different key populations such are, men who have sex with men (MSM), female sex workers (FSW), hijras with transgenders (H/TG) and people who inject drugs (PWID) in India, present systematic review has been initiated using existing published evidence [3-4].

2. Materials and Methods

A study protocol was developed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. All available peer reviewed published articles are extracted using suitable search terms [5] in PUBMED, MEDLINE, EMBASE, Cochrane Library, Science Direct, Google Scholar and Psychinfo along with published re-ports (as grey literature) from reliable sources, comprising all studies from January 2000 to December 2023.

A protocol for the systematic review was prepared and registered in the PROSPERO, having the registration number CRD42022357425 and published subsequently [5].

2.1. Evaluation of the methodological quality

Evaluation of selected studies was performed through title, text and abstract prior to the accumulation of it into the decisive analysis. Evaluation was performed with the help of modified Newcastle - Ottawa Quality Assessment tool [6]. Evaluation was completed be-fore collection of information.

2.2. Geographical distribution with spatiotemporal attributes

Geographical distributions of previously mentioned STIs in Indian key population were presented using heat map and choropleth maps, generated with the help of Quantum GIS (Ver. 3.18 Zurich) [7]. An administrative map of India containing the latest information of states and union territories is georeferenced and the resulting polygon was used as the base map layer. State-level STI prevalence data were added as comma delimited layers. Prevalence data from accepted studies were added as spatiotemporal attributes in separate layers respectively. Finally, maps were generated for overall included studies for each key population with prevalence of four curable STIs in histogram format in a separate layer. Multiple points were used to generate heat map of STI prevalence. Data based on regional distribution of STIs among key population has been entered into the newly pre-pared maps as non-spatial attributes [8].

3. Results

The present findings would be vital to understand the STI status among key population and to design evidence-based strategies for STI prevention in key population in India. There are total of 8919 publications are selected initially. The abstract and titles were screened for eligibility and duplicates were removed. A total of forty articles were included from peer reviewed journals. Among the 70 reports (grey literature)- excluding Sankalak Reports (two documents), published by several competent national, international, and state agencies, any reports could not be included based on the screening tool. Details of the inclusion and exclusion criteria, along with the, number of each category of articles are described through PRISMA flow Diagram [Figure 1].

Search of relevant databases (PUBMED. Google Scholar, Mendeley, Cochrane Library, Scopus, Science Direct and EMBASE) yielded 40 articles which met the inclusion criteria set in the protocol for the present systematic review. However, it is found that published articles were not available from all geographical regions in India. Most of the studies were conducted in southern and western part. However, four studies were also reported from north-eastern part of India. A few studies form northern India was also conducted in Del-hi and Lucknow (Figure 2).

Figure 1: PRISMA Flow Diagram.

Figure 2: Map of India indicating the regions where included studies were conducted.

Maximum numbers of studies reported on STI prevalence, were belongs to MSM and FSW population followed by H/TG and PWID and mostly based on syphilis seroprevalence. Data on chlamydia and gonorrhea were less available, trichomoniasis was least reported STI. While synthesizing data, articles which included more than one key population was counted separately. Eighteen articles reported STI prevalence among FSWs [1-4,8-23]. These eighteen articles included twenty-six different studies based on prevalence data of different STIs, different FSW subgroups and diverse geographical region. All data related to FSW was presented through two different diagnostic methods, aetiological [1-4,8-20] (Table 1) and syndromic [20,23] (Table 2). STI prevalence among MSM was reported in nineteen articles [3,15,24-40]. Based on different STIs and geographical regions total forty studies were recorded for this review. Relevant extracted data on MSM was recorded un-der aetiological diagnosis [3,15,24-40] (Table 3) and syndromic [33,40] (Table 4) diagnosis. Four articles on H/TG included four studies on STI prevalence among H/TG based on different STI and geographical region [18,29,31,41]. Data on H/TG under aetiological diagnosis was presented in Table 5. There was no data available for syndromic diagnosis. Two articles [15,42] were available for STI prevalence among PWID. These two articles comprise six studies on prevalence of different STIs among PWID population in India (Table 6).

CH- Cohort study; CS- Cross-sectional study; TLC- Time Location Cluster, CCS- Conventional Cluster Sampling, NR- Not Reported; TPHA- Treponema Pallidum Heamagglutination Test, RPR Rapid Plasma Reagin; NAAT- Nucleic Acid Amplification Test

Table 1: Aetiological diagnosis and prevalence of four curable STIs among FSW from available published articles from different parts of India.

CH- Cohort study; CS- Cross-sectional study; NR- Not reported; TLC- Time Location Cluster,  RDS- Respondent Driven Sampling

Table 2: Syndromic diagnosis and prevalence of four curable STIs among FSW from available published articles from different parts of India.

CH- Cohort study; CS- Cross-sectional study; TLC- Time Location Cluster, NR- Not Reported; TPHA- Treponema Pallidum Heamagglutination Test, RPR Rapid Plasma Reagin; NAAT- Nucleic Acid Amplification Test

Table 3: Aetiological diagnosis and prevalence of four curable STIs among MSM from available published articles from different parts of India.

CH- Cohort study; CS- Cross-sectional study; NR- Not Reported,, ; TLC- Time Location Cluster, PSSw- Painful Scrotal Swelling

Table 4: Syndromic diagnosis and prevalence of four curable STIs among MSMs from available published articles from different parts of India.

3.1 Findings among FSW

As per the search, there are eighteen articles comprises of twenty-six studies, which were find out, tell us out about the different STIs among FSW (Table 1 and 2), most of these studies were conducted in Andhra Pradesh, Telangana, Karnataka, Maharashtra, Uttar Pradesh, West Bengal, and Nagaland. Almost half of the studies were conducted in facilities like STI clinics or tertiary care hospitals (Figure 2). Out of 26 studies, most of the studies reported prevalence through aetiological diagnosis (Table 1). Most of the studies reported on single STI, namely syphilis. Among the published articles, an article from Beksinska et al. was published in 2018 [22], however, the study period was 2011. There was very little published article on STI prevalence estimation among FSW after 2011. This cross-sectional study on syphilis among FSW performed in Karnataka and the estimated prevalence was 3.2. Screening was done through RPR followed by TPHA.

Figure 3: Representation of published articles on four curable STIs among FSWs in India.

Out of all available studies on FSW, a facility level cross-sectional study with a little lower sample size of 45, estimated very high syphilis prevalence (28.8) in West-Bengal [15]. A study conducted in Mumbai during the period of 2007- 2008. [11] and published in 2011, estimate prevalence of syphilis among two groups of sex workers, brothel based FSW had highest syphilis prevalence of 6.6 and the bar-based sex workers had lowest prevalence of 1.3. Trichomoniasis was the least examined and hence least reported STI among FSW (Figure. 3). A study, which based on syndromic diagnosis, was conducted in Nellore, Andhra Pradesh during the period of January to December, 2011, unveiled genital herpetic and non-herpetic ulcer, cervical discharge, Inguinal buboes vaginal discharge and ano-rectal discharge in FSWs (Table 2). The highest reported symptom was vaginal discharge (50.7%) [20]. There was a single reported study each from Nagaland, West Bengal, and Maharashtra, two from Karnataka and Tamil Nadu and three studies from Andhra Pradesh. Most of the district level studies were reported from Karnataka and Andhra Pradesh. Four district level or small studies were reported from Mumbai and two each from Bangalore and Mysore (Figure 3).

3.2 Findings among MSM

Nineteen articles [3,15,24-40] on MSM were find out through literature search. Most of them were conducted in Tamil Nadu, West Bengal, Andhra Pradesh, Telangana, Karnataka, and Maharashtra (Figure 5). Almost half of the studies reported from facility level such as STI clinics or tertiary care hospitals. Most of the studies reported prevalence through aetiological diagnosis (Table 3). The most recent available publication reported through literature search, was by Swamiappan et al. [40] and by Safren et al. [39] and both published in 2020. The study conducted in Chennai during July 2016 to June 2019 [40] was reported prevalence of syphilis (8.8) through RPR without mentioning any confirmatory test. Along with the aetiological diagnosis, this study [40] reported symptoms of Urethral Discharge (2%), Genital herpetic Ulcer (3.1%) and Non-herpetic Ulcer (2%). Another cross-sectional study conducted in Mumbai and Chennai without specifying any study period (Table 4), reported prevalence of syphilis, gonorrhoea, and chlamydia as 16.1, 8.3 and 11.3 respectively in Chennai and 14.8, 16, 18.2 respectively in Mumbai [39]. Most of the studies reported Syphilis as none of the studies reported Trichomoniasis. Gonorrhoea and chlamydia were also examined by many of these studies. For aetiological diagnosis RPR screening test followed by TPHA confirmatory test were administered for syphilis and PCR and NAAT for gonorrhoea and chlamydia. Similarly, a cross-sectional community-based study [3] in Andhra Pradesh, estimate a very high syphilis prevalence of 20.0, during the study period of 2003 to 2007. In the same state, Andhra Pradesh a cross-sectional study was conducted in Vijayawada and Vizag, during 2012-2013 and had estimated prevalence of 4.4, and 2.1 respectively [28]. As per the literature search, there are single study from each state of Karnataka, West Bengal and Maharashtra was reported whereas; two studies were reported from Andhra Pradesh and Tamil Nadu. A considerable number of studies were reported from Mumbai, Chennai, and Pune. A few sporadic studies were also evident from Delhi, Lucknow, Bhopal, and Hyderabad. There \was no published article from North-eastern India. Studies from Mumbai, Chennai and Pune showed higher STI prevalence. Similar to FSW population, prevalence of syphilis was reported in most of the studies, whereas a fewer study reported studies on trichomonas (Figure 4).

Figure 4: Representation of published articles on four curable STIs among MSMs in India.

Figure 5: Geographical representation of published four curable STIs among H/TGs in India.

3.3 Findings among H/TG

From the literature search it was revealed that among the all STIs, syphilis was only re-ported among H/TGs in India. Present search finds out. four articles [11,29,31,41]. The recent published article on facility level study [41], which was conducted in a cohort of a sub group of males to female transgenders estimates prevalence of syphilis was 20.7 (Figure 5). Other four studies reveal from the present search, are reported from Tamilnadu, Mumbai, Chennai, and Pune. Although current finding shows a poor regional representation of H/TG on STI prevalence (Table 5).

CH- Cohort study; CS- Cross-sectional study; TLC- Time Location Cluster, NR- Not Reported; TPHA- Treponema Pallidum Heamagglutination Test, RPR Rapid Plasma Reagin; NAAT- Nucleic Acid Amplification Test

Table 5: Aetiological diagnosis and prevalence of four curable STIs among H/TG people from available published articles from different parts of India.

3.4 Findings among PWID

There were only four articles reported STI prevalence among PWID [11,42-44], found chlamydia in India. A cross-sectional study on PWID published on 2008 carried out in Manipur, Nagaland and Maharashtra (Mumbai, and Thane), which reported seroprevalence of syphilis and gonorrhea as 19.5% and 1.6 respectively at Wokha, and 11.4% as chlamydia for 0Phek Nagaland [42]. without mentioning any specific study period. Another article comprised of data from North-eastern India viz. Phek, Wokha, Churachandpur, Bishnupur along with Mumbai-Thane [43] reported on prevalence of syphilis and chlamydia. Representation from North-eastern region was reported during present literature search (Figure 6), but no STI prevalence was reported from West Bengal. The data also implied a weak regional representation of STI prevalence among PWID (Table 6) in India.

Figure 6: Representation of published articles on four curable STIs among PWIDs in India.

CH- Cohort study; CS- Cross-sectional study; TLC- Time Location Cluster, NR- Not Reported; TPHA- Treponema Pallidum Heamagglutination Test, RPR Rapid Plasma Reagin; NAAT- Nucleic Acid Amplification Test

Table 6: Aetiological diagnosis and prevalence of four curable STIs among PWID from available published articles from different parts of India.

3.5 Key findings

Forty articles were included in this systematic review after screening for inclusion criteria. Ghosh et al., 2012 reported a very high syphilis prevalence is 28.8 among FSW in West Bengal for a very small sample size of 45. A very low syphilis prevalence 0.8 was reporte [28] among MSM in Belgaum, where the sample size was 1003. A facility based cross-sectional study was conducted in Mumbai and Hyderabad for a sample size of 149 [30] reported a very high prevalence for Gonorrhea (14.8) among MSM. However, a community based cross sectional study conducted in Tamilnadu [31] reported a very low gonorrhea prevalence (0.07) among MSM with the sample size of 1621.Only nine articles reported Chlamydia among key population. A very high chlamydia prevalence (22.2) was reported by Medhi et al. [16] a community based cross-sectional study conducted on FSW in Nagaland with a sample size of 423. A similar community based cross-sectional study conducted in Tamilnadu [33] reported a very low chlamydia prevalence, 0.3 for MSM, Trichomoniasis was reported only by 1/10th [ n=40] of the reviewed articles. From the available data of the included studies, it was found that STI prevalence was high when samples were taken from facility setting irrespective of region and key populations.

3.6. Quality of the selected studies

The modified Newcastle - Ottawa Quality Assessment Scale was applied to determined quality of included studies and the result was presented pictorially (Figure 7). Here, it must be noted that, quality of all the included studies calculated and presented here is only to accomplish the demands of present systematic review, except this author have no purposeful intention (Figure 7).

Figure 7: Quality Assessment Performance Matrix.

4. Strength and limitations

The prevalence of STIs shows considerable heterogeneity by geographical setting and key population group. At the same time, limited numbers of study reported STI prevalence, sampling heterogeneity across studies prevent definite conclusions and how the prevalence of STIs varies among key populations. All the included studies in the present systematic review used probability-based sampling and both in facility as well as community-based setting. However, there were limited data points from all regions in India. The variation among included studies highlights a limitation of the present review, as the findings can vary based on the electronic databases and selected search terms. However, present article summarizes of all study that allows pre-defined acceptance criteria and qualify the quality assessment tool (Tables 1-6).

5. Discussion

Forty articles were included in this systematic review after screening for inclusion criteria. State- wise distribution revealed that Tamilnadu, Andhra Pradesh, Karnataka, Maharashtra were study locations for 3/4th of the included articles [ n=40]. Two articles determined prevalence of the four STIs among PWID in Manipur and Nagaland. Three articles with the prevalence of STIs among FSW and MSM in the cities of central and Northern India. One article was found from West Bengal. There were three articles that reported aetiological as well as syndromic prevalence among key population. One article reported only syndromic prevalence for FSW. Remaining articles reported the prevalence of four STIs among key populations through aetiological diagnosis. RPR and TPHA tests were con-ducted for diagnosing syphilis; NAAT or Gen Probe APTIMA were used for diagnosing gonorrhoea and chlamydia; kupferburges culture, wet mount microscopy tests were con-ducted for diagnosing trichomoniasis. Over the last two decades, the National AIDS Control Program of India (NACP) implemented by National AIDS Control Organization (NACO) which, undertakes prevention of STI as one of the key strategies. NACO through its network of designated STI or RTI (reproductive tract infection) clinics (situated at government health care facilities located mostly at the district level and above) is providing free standardized STI/RTI services. These clinics have been branded as “Suraksha Clinics” and provide sexual and reproductive health services [45]. Function of these Centre is to provide validation of syndromic case management by doing etiologic testing, antibiotic susceptibility testing for Gonococci, EQAS for syphilis, and conducting operations re-search providing evidence to the programme. [46]. Still, there is a limited literature till date to report pooled prevalence among key populations across India and these data have not been integrated to inform the overall geographical and temporal trends of STI infections among various key populations in India.

5. Conclusion

The present systemic review had generated on the prevalence and spatiotemporal distribution of the four STIs in Indian key population. Prevalence of STIs showed extensive het-erogeneity through spatiotemporal setting and people practicing high-risk beheviour in India. A national STI surveillance cum prevention programme is essential among key populations in India. In the light of present findings and with the identified limitations, it can be concluded that existing HIV surveillance system under NACP, can be utilized with additional bio-specimen collection to determine STI prevalence among high risk populations. However, in future, with the availability of the comparable data from most of the regions in India, it will be possible to conduct a systemic review with pooled prevalence on the spatiotemporal distribution of the four curable STIs in the general population of India.

Supplementary Materials: The following supporting information can be downloaded at: www.mdpi.com/xxx/s1, Table S1: search terms and search strategy; Table S2 PRISMA chart.

Author Contributions: MB, SB, AR, BTV, BSB, TLNP, LS, ND and SD Conceptualize and design the study. Data curation was done by MB, UG, PG, PB, and SB. Investigation MB, UG, PG, PB, SA, and SB. Methodology MB, UG, PB, SA, SB, AKD, DC, CB, GKM, BSB, FD and SD. Formal analysis UG, PG, MB, PGG, PK, BSB, GKM and PB. Funding acquisition AR, RA, and SD. Project admin-istration MB, TLNP, LS, ND, SB, RA, and SD. Supervised by BTV, TLNP, LS, MB, ND, PR, CB, RA, AKD, GKM and DC. Resources DC, AKD, AR, RA, and FD. Writing – original draft MB, UG, PK, PB, and SB; and Writing – review & editing MB, AM, TLNP, PR, PK, PGG, BSB, SA, SB, and SD. All authors read the manuscript before they have given the final approval for publication.

Funding: Fund for this research is provided by World Health Organization (Reg. No. 2024/1456501). Moreover, the funders had no role in the study design, data collection, analysis, the decision to publish, or the preparation of the manuscript.

Data Availability Statement: No separate datasets were generated or analyzed during the cur-rent study. All relevant data from this study are available with the present article.

Acknowledgments: Authors are acknowledging all the technical, administrative officials of ICMR-NIRBI, Kolkata. Cochrane, London UK; NACO, Ministry of Health and Family Welfare, Govt. of India, and World Health Organization.

Conflicts of Interest: The authors have declared that no competing interests exist.

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