Prevalence and determinants of Human Papillomavirus (HPV) infection in Kerala, India

Abstract

The present study has addressed the prevalence and determinants of HPV infection in a general population in Kerala, India and considered the implications for the control of HPV infection and cervical cancer.

In a suburban region of Trivandrum, the capital city of Kerala State in the Indian Union, a cohort of married women from the general population was formed. Nine thousand three hundred and twenty women were identified as eligible and were invited to clinics held in the field for interview and biological samples were collected after obtaining an informed consent. The overall compliance was 43.5% giving 4056 women for the study. Two thousand five hundred and thirty five women were interviewed for details on sexual behaviour and genital hygiene.

Testing for HPV was done by PCR as per standard protocol at the Institute of Cancer Research Laboratories in Sutton, UK. Prevalence and determinants were studied for all types of HPV.

The overall HPV prevalence was 6.1%. The prevalence was almost steady across the age groups. Women in the low socio-economic strata had a higher prevalence, 7.3% compared to 4% for those in the higher socio-economic strata. Women who were separated from their husband's had a prevalence of 8.4% compared to 5.9% for those who were living with their husbands. Women whose husbands used condoms had a low prevalence of 2.9% compared to 6% for those who did not practise any method of contraception. However this was based only on 2 HPV positive women and may not be reliable.

Genital hygiene of husband and wife were combined into one variable and those who did not practice genital hygiene had a high prevalence (24% versus 7%). Women who reported promiscuity had a prevalence of 18.5% compared to 8.3% for those who did not. The prevalence rate was 10.2% for women whose husbands had promiscuity compared to 7.8% for those who had no report of promiscuity among husbands.

Poor socio-economic status, lack of genital hygiene of the couple and promiscuity of women emerged as the independent predictors of HPV infection in this population. The odds ratio for women in the lower social class was 2.16 (95 % CI 1.54-3.02) compared to those in the lower social class. The odds ratio was 3.76 (95% CI 2.56- 5.51) for having HPV if they and their partners did not practise genital hygiene compared to those with good hygiene. Women who had a history of multiple sexual partners had an odds ratio of 2.17 (95% CI 1.12-4.22) for HPV compared to those who reported no promiscuity.

If the factors low socio-economic status, poor genital hygiene and promiscuity of women are considered responsible for HPV infection in this population, then 40.6% of the infection can be prevented by improving the socio-economic status of the women, 14.2% can be prevented by improving genital hygienic practises of the couple and 2.3% can be prevented by women avoiding promiscuity.

The reported prevalence of HPV infection is mainly from western populations and they are not comparable to the socio-cultural milieu of the population in Kerala. Premarital sex is considered forbidden and multiple partnerships for women are negligible. Extramarital sexual relations of men seem to be in frequenting commercial sex workers.

Identification of genital hygiene and socio-economic status as independent predictors suggests that control of HPV infection can be achieved by improving the living standards of women. The cervical cancer incidence in Trivandrum Cancer Registry was 15 per 100,000 in 1991-92 and there are no organised cervical cytology screening programmes in the area. The subgroup of women who harbour HPV and who might ultimately develop cervical cancer are likely to be those in the low socio-economic strata with poor genital hygiene and multiple sexual partners.

This study has raised the problems of general population based epidemiological studies in low resource settings and identified the strategies to overcome them. The main limitation of this study was that all HPV types were considered together in the analysis. The subtyping of HPV was made available later and showed that 50% were high risk HPV types. Low socio-economic status and poor genital hygiene seem to be exerting their effects independently and this may also suggest a non-sexual route of HPV transmission. Identification of risk factors separately for the oncogenic and non-oncogenic types will be undertaken later as more data accrues and this will help to delineate the differences.

The prospects of HPV vaccination and HPV based screening are being considered as options for cervical cancer control. It might take many years for poor countries to establish organised population based screening programmes. Empowerment of women, improvement of living standards, and health education coupled with low intensity Pap smear and provision of equitable resources for treatment can control HPV infection and bring down the cervical cancer incidence in the poor countries of the world.

The present study has addressed the prevalence and determinants of HPV infection in a general population in Kerala, India and considered the implications for the control of HPV infection and cervical cancer.

In a suburban region of Trivandrum, the capital city of Kerala State in the Indian Union, a cohort of married women from the general population was formed. Nine thousand three hundred and twenty women were identified as eligible and were invited to clinics held in the field for interview and biological samples were collected after obtaining an informed consent. The overall compliance was 43.5% giving 4056 women for the study. Two thousand five hundred and thirty five women were interviewed for details on sexual behaviour and genital hygiene.

Testing for HPV was done by PCR as per standard protocol at the Institute of Cancer Research Laboratories in Sutton, UK. Prevalence and determinants were studied for all types of HPV.

The overall HPV prevalence was 6.1%. The prevalence was almost steady across the age groups. Women in the low socio-economic strata had a higher prevalence, 7.3% compared to 4% for those in the higher socio-economic strata. Women who were separated from their husband's had a prevalence of 8.4% compared to 5.9% for those who were living with their husbands. Women whose husbands used condoms had a low prevalence of 2.9% compared to 6% for those who did not practise any method of contraception. However this was based only on 2 HPV positive women and may not be reliable.

Genital hygiene of husband and wife were combined into one variable and those who did not practice genital hygiene had a high prevalence (24% versus 7%). Women who reported promiscuity had a prevalence of 18.5% compared to 8.3% for those who did not. The prevalence rate was 10.2% for women whose husbands had promiscuity compared to 7.8% for those who had no report of promiscuity among husbands.

Poor socio-economic status, lack of genital hygiene of the couple and promiscuity of women emerged as the independent predictors of HPV infection in this population. The odds ratio for women in the lower social class was 2.16 (95 % CI 1.54-3.02) compared to those in the lower social class. The odds ratio was 3.76 (95% CI 2.56- 5.51) for having HPV if they and their partners did not practise genital hygiene compared to those with good hygiene. Women who had a history of multiple sexual partners had an odds ratio of 2.17 (95% CI 1.12-4.22) for HPV compared to those who reported no promiscuity.

If the factors low socio-economic status, poor genital hygiene and promiscuity of women are considered responsible for HPV infection in this population, then 40.6% of the infection can be prevented by improving the socio-economic status of the women, 14.2% can be prevented by improving genital hygienic practises of the couple and 2.3% can be prevented by women avoiding promiscuity.

The reported prevalence of HPV infection is mainly from western populations and they are not comparable to the socio-cultural milieu of the population in Kerala. Premarital sex is considered forbidden and multiple partnerships for women are negligible. Extramarital sexual relations of men seem to be in frequenting commercial sex workers.

Identification of genital hygiene and socio-economic status as independent predictors suggests that control of HPV infection can be achieved by improving the living standards of women. The cervical cancer incidence in Trivandrum Cancer Registry was 15 per 100,000 in 1991-92 and there are no organised cervical cytology screening programmes in the area. The subgroup of women who harbour HPV and who might ultimately develop cervical cancer are likely to be those in the low socio-economic strata with poor genital hygiene and multiple sexual partners.

This study has raised the problems of general population based epidemiological studies in low resource settings and identified the strategies to overcome them. The main limitation of this study was that all HPV types were considered together in the analysis. The subtyping of HPV was made available later and showed that 50% were high risk HPV types. Low socio-economic status and poor genital hygiene seem to be exerting their effects independently and this may also suggest a non-sexual route of HPV transmission. Identification of risk factors separately for the oncogenic and non-oncogenic types will be undertaken later as more data accrues and this will help to delineate the differences.

The prospects of HPV vaccination and HPV based screening are being considered as options for cervical cancer control. It might take many years for poor countries to establish organised population based screening programmes. Empowerment of women, improvement of living standards, and health education coupled with low intensity Pap smear and provision of equitable resources for treatment can control HPV infection and bring down the cervical cancer incidence in the poor countries of the world.