HCV sexual transmission linked to anal sex, drug use, lower CD4 count

In addition to the usual risk factors for hepatitis C virus (HCV) sexual transmission seen in most previous studies – such as anal sex and having other sexually transmitted infections – researchers in the Netherlands also saw an association with nasal and injection drug use and lower CD4 cell count, they reported in a poster presentation at the recent Conference on Retroviruses and Opportunistic Infections (CROI 2015) in Seattle, USA.

HCV, a blood-borne virus, historically has been most often transmitted via shared drug injection equipment or blood transfusions. But in the early 2000s, researchers in the UK and Europe began reporting outbreaks of apparently sexually transmitted acute HCV infection among HIV-positive men who have sex with men (MSM); similar reports later followed in Australia and in US cities including New York and San Francisco.

Several risk factors have been associated with HCV sexual transmission – including anal intercourse, fisting, group sex, having other sexually transmitted infections (STIs) and non-injection recreational drug use – but these have not been entirely consistent across studies. It is difficult to tease out risk factors because many gay men engage in multiple activities, often on the same occasion. Studies looking at the presence of HCV in semen have also been inconsistent.

Joost Vanhommerig from the Amsterdam Health Service and fellow investigators conducted the MOSAIC study to assess risk factors for acute HCV infection among HIV-positive gay and bi men.

MOSAIC is one of the first studies to look at both biological and behavioural determinants of acute HCV infection, the researchers noted as background. Most previous studies evaluating risk factors for recently acquired HCV infection were initially designed to study HIV, not hepatitis C.

From 2009 onwards, 82 HIV-positive MSM with acute HCV infection were prospectively followed at five outpatient clinics in Amsterdam, Rotterdam and Utrecht. For each case, the analysis also included one or two HIV-positive gay men without HCV as controls (total 131).

The overall median age was 46 years. A majority had HCV genotype 1a (63%), followed by 4d (13%), 2b (12%), 1b (7%) and undetermined (4%). Injection drug use was reported by ten men with HIV/HCV co-infection (12.2%) and two with HIV alone (1.5%).

Study participants completed written questionnaires covering social and demographic characteristics, blood-borne risk factors for HCV infection, and sexual behaviour and drug use during the six months prior to study entry. Clinical data related to HIV and hepatitis C were obtained through linkage with databases from the Dutch HIV Monitoring Foundation.

The following factors were found to be significantly associated with increased likelihood of acute HCV infection in a multivariate analysis, listed in order of strength of association:

• Injection drug use: odds ratio (OR) >10
• Ulcer-causing STIs (syphilis, genital herpes, lymphogranuloma venereum): OR ~5
• Condomless receptive anal intercourse: OR ~5
• Sharing sex toys: OR ~4
• Sharing straws for snorting drugs before or during sex: OR ~3.5
• Unprotected fisting: OR ~3
• Lower CD4 cell count at the last visit before testing HCV-positive: OR ~1.7 per cubic root lower.

However, the number of casual sexual partners, anal rinsing or douching, rectal bleeding and meeting partners at sex parties were not independent risk factors for HCV acquisition in this analysis.

"In the on-going HCV epidemic in which HIV-infected MSM with high-risk sexual behaviour were probably infected first, especially MSM with lower risk profiles may become increasingly affected by acute HCV," the researchers concluded.

This analysis differs from most prior studies in that it saw a significant effect of injection drug use – although the total number of people who reported injecting drugs was quite small, so it is hard to draw definitive conclusions – and did not see an association with having more sexual partners or participating in group sex.

In their printed abstract, the authors noted that further studies are needed to explore the role of CD4 cell count, as it is still unclear whether a lower CD4 count facilitates HCV infection, is a result of acute HCV infection or perhaps both. In fact, many HIV-positive men with sexually transmitted HCV have high CD4 counts.

These findings suggest safer sex and drug use practices that could potentially reduce the risk of HCV transmission in a sexual setting, including using condoms for anal sex and gloves for fisting, covering or not sharing sex toys, and not sharing equipment for nasal or injection drug use. They also support the growing number of experts who recommend regular HCV screening for sexually active gay and bi men.