Risk factors and distribution of oncogenic strains of human papilloma virus in women presenting for cervical cancer screening in Port Harcourt, Nigeria

Introduction Human papilloma virus(HPV) accounts for most cases of cervical cancer with high risk HPV(hrHPV) genotypes largely responsible. The objective is to ascertain the distribution of oncogenic strains of human papilloma virus genotypes and predisposing risk factors in women presenting for cervical cancer screening in Nigeria. Methods A cross-sectional study of 80 women who presented for cervical cancer screening. The biodata of the participants, the presence of risk factors to HPV were recorded and hrHPV were identified using PCR technique. The information obtained was processed using the SPSS version 20 software. Results were presented in tables, test of significance and association done using student's t-test and Odds ratio, with P value < 0.05 as significant. Results The age range of patients was 19-62 years with prevalence of hrHPV of 10%. HrHPV are more in patients with more than one life time sexual partner (OR 1.26,95%CI 0.13-29.99), multiple sexual partners (OR 1.55, 95% CI 0.28-8.70), early coitarche (OR 1.57, 95% CI 0.14-15.00) and previous STI (OR 150, 95%CI 9.53-1979. 62). Four hrHPV genotypes: 16, 18, 31 and 35 were detected. Conclusion HPV genotype 18 was predominant in Port Harcourt, Nigeria. High risk sexual behaviours are associated with acquisition of hrHPV.


Introduction
Cervical cancer is a malignant lesion of the cervix. The squamous cell carcinoma constitute about 90-95% of cases while adenocarcinoma make up about 5-10% [1]. Worldwide, every two minutes, a woman dies of cervical cancer and it is the leading cause of cancer deaths with women in developing countries accounting for 85% of these deaths [2]. About 99% of cases of cervical cancer have been associated with human papilloma virus infection which is a sexually transmitted disease [2]. Out of about 200 types of HPV isolated so far, at least 30 different types target genital mucosa and approximately 15 of these are oncogenic [2,3]. About 80% of women will acquire an HPV infection in their lifetime and HPV genotypes 16, 18, 45, 31 and 33 are the most common types associated with cervical cancer worldwide [2,3]. About six percent of cervical cancer cases had been associated with multiple HPV infections [2]. HPV is a relatively small virus containing circular double-stranded deoxyribonucleic acid within a spherical shell (capsid).It infects cutaneous epithelium and mucosal epithelium (cervical and other anogenital mucosae). HPV is transmitted through sexual intercourse and/or genital skin-to-skin contact [3]. It is the most common sexually acquired infection in the world with a prevalence of about 50% in young sexually active adolescents [3,4].
Most of the infections are self-limiting and harmless and the persistence of the oncogenic HPV types cause cervical cancer in women [4,5]. The prevalence of HPV genotypes has been documented from different studies in different countries and regions [4][5][6][7]. However, the prevalence of HPV genotypes has not been well studied in the South -South region of Nigeria. It is based on this premise that this study seeks to determine the predominant high risk HPV genotypes in the region; in addition to elucidating the risk factors associated with this infection so as to facilitate measures of reducing the scourge of cervical cancer in the populace, which has been linked to human papilloma virus infection.

Methods
This was a cross sectional prevalence study carried out, between August 2014 and December 2014 in the cancer screening centre of UPTH on women who presented for cervical cancer screening in the University of Port Harcourt Teaching Hospital, Port Harcourt. All women between the ages of 15 to 70 years were included in the study after due counseling and obtaining consent to be involved in the study. Women were excluded from the study if they refused to give consent, had total abdominal hysterectomy, had been treated for premalignant lesion of the cervix, were adequately immunized against the human papilloma virus or had received antineoplastic therapy or immunotherapy. The sample size was determined using the Leshe-kish formula for single proportion [8] which is n=Z 2 p(1p)/d 2 ; where P is the HPV prevalence in Ibadan Nigeria [4]. Allowing for 100% degree of accuracy and allowing a ten percent attrition, a total of 80 women who presented for cervical cancer screening were recruited. Patients were recruited as they presented until the required number was achieved.
A structured study proforma was administered on each of the women. The following information was obtained from the women: age, occupation level of education, marital status and parity. Other information obtained from the women included the history of smoking, age at coitarche; number of lifetime sexual partners and history of previous sexually transmissible infections. The presence of partners who had multiple sexual consorts was also ascertained.
The phone numbers of the participants were collected for disclosure of the results, counseling and advice on further management where necessary.
The collection of the sample was done in the presence of a female nurse who also served as a chaperone. In collecting the sample, the women were placed in lithotomy position, the cervix was exposed using the bivalve speculum and then inspected. The specimen for the HPV genotyping was collected using the cyto-brush, cut short at the brush end and inserted into an already numbered specimen bottle, which contained a physiological saline. All collected samples with the cyto-brush were packaged in an ice pack in a container and were sent to the Safety Molecular Pathology laboratory at Enugu, Frequency tables were generated and the results tested of significance using student t-test and chi-square. The age-specific prevalence and the contribution of other socio-demographic factors were computed. The risk of acquiring hrHPV was estimated with odds ratio. Statistical test of association was carried out at the level of significance set at P value <0.05 at 95% confidence interval.
Ethical considerations: Ethical clearance for the study was obtained from the ethics committee of the Teaching Hospital before the commencement of the study.

Results
A total of 80 women who met the inclusion criteria were recruited for the study. The age range of the participants was 19-62 years.
The median age was 39 ± 5 years. Eight women out of the 80 women who participated in the study were positive for the oncogenic strains of human papilloma virus giving a prevalence of 10%.
In Table 1, the socio-demographic characteristics of the women showed that 50% (4) of the women who had HPV were less than 25 years. The peak age prevalence was between 30-39 years at 37%.
Eighty seven percent of the women with HPV had 3 or more deliveries. Among women with hrHPV, 87.5% (7)

Discussion
The prevalence of human papilloma virus (HPV) in this study was 10% which is similar to the adjusted global prevalence of 10.41% in a study on epidemiology and transmission dynamics of genital HPV infection [9]. However, higher prevalence of 24.8% and 21.6% were found in a population-based study in Ibadan and Okene, Nigeria respectively where oncogenic strains were identified in 19.7 and 16.6% respectively [4,10]. Prevalence of 11% was also found in women who tested negative to human immunodeficiency virus in Lagos, Nigeria [11] though the retroviral status of patients was not evaluated in this survey. There is a global variation in the prevalence of oncogenic strains as evident by observations in Benin, West Africa and Puebla in Mexico where prevalence of 32.2% and 24.4% respectively had been noted [12,13]. The study in Benin discovered that the high risk HPV genotypes of 16, 18, 35, 58 and 59 were found in 88% of the infections [12]. The HPV genotypes of 16, 18,31 and 35 found in this study was relatively similar to types 16,31,35 and 58 noticed in Ibadan, Nigeria [4]. Similarly, epidemiological studies in Ghana and South Africa revealed that types 16, 18, 35 and 45 were the most common HPV types in Sub-Saharan African women [14]. However, type 45 was not isolated in this study.
The human papilloma virus type 18 was the predominant genotype identified. A review of patients with proven cervical cancer in Ghana and South African also identified serotype 18 as being contributory in about 17.2% of cases reviewed [14]. The study in Mexico revealed that HPV type 18 contributed 35.7% of the detected HPV genotypes [13]. An interface of the various studies and noticing higher HPV prevalence in this study compared to the patients with cancer, will give credence to the fact that there is spontaneous resolution of HPV infection irrespective of the oncogenic potential of the virus while the remaining persistent strains cause the dysplastic changes cumulating to cervical cancer [4,5]. Mixed infection among women has been documented [2] and multiple infections occur more in women with HIV infection and other immunosuppressive conditions [14]. A mixed infection rate of 12.5% was observed involving strains 18 and 35, which is lower than the occurrence of multiple infections in 33.5% of the women with HPV in the Ibadan study [14]. The retroviral status of the participants in this study was, however not tested. The peak of prevalence of HPV in this study was noticed in 2 age groups of 20 and 29 years and 30 and 39 years of age. These groups represent the women in their reproductive peak who are sexually active and thus not surprising so that the high oncogenic strains are more in the age distribution.

Conclusion
The high prevalence of the high risk HPV genotypes noted in this study exposes the magnitude of the burden of HPV infection in our environment. There is need to increase the level of surveillance on females at risk of cervical cancer in this environment, since significant proportion of highly oncogenic strains with a high propensity to transformation to malignancy were observed in this study. Furthermore, there is need to encourage Government agencies to promote a more inclusive HPV vaccine such as Gardasil-9 in their national immunization scheme which has a wider coverage as against those currently available in most countries. This should be administered to girls at the appropriate age if transmission of HPV is to be reduced. There is also need for sexual behaviour modification in order to reduce the impact of the risks factors identified in this study.
What is known about this topic  Oncogenic strains of HPV are responsible for 99% of cervical cancer  Natural history of cervical cancer  HPV genotyping is a screening method for cervical cancer

What this study adds
 This is the first study of its kind in South-South Nigeria

Competing interests
Authors declare no competing interests.  Table 1: Socio-demographic characteristics of the participants