Preventing hepatitis C virus transmission in Australians who inject drugs

Most people currently dying of HCV infection in Australia are middle-aged or elderly immigrants from Southern Europe, the Middle East and Asia. To date, 31.3% of liver transplants performed for hepatitis C infection in Australia² and 52.4% of hepatocellular carcinomas diagnosed in people with HCV infection in Victoria³ have been in this group. These people have acquired the infection in their country of birth from cultural practices involving skin penetration, or medical interventions, including injections.

In this issue of the Journal, MacDonald et al examine the influence of harm reduction programs by measuring seroprevalence of HCV in people who attended a cross-section of needle and syringe exchange programs throughout Australia in 1995, 1996 and 1997.⁷ Their findings, which show that seroprevalence fell from 63% in 1995 to 50% in 1997, are encouraging. There may have been selection bias, but, if one assumes that this bias applies equally to all three years studied, there has been a 21% reduction in seroprevalence during that time. The results were even more striking in recent users, in whom there has been a 41% reduction.

For some reason there was no additional reduction between 1996 and 1997. Does this mean the effect of harm reduction programs has plateaued? That there is a limit to their efficacy? That only a certain proportion of users can be influenced by education programs? While further studies are needed over the next two or three years to clarify this, these data strongly support the need for ongoing efforts at harm reduction and maintenance of needle and syringe exchange programs.

Can we do more to reduce seroprevalence of HCV in people who inject drugs? There has been a great deal of debate in the public domain about the various prevention and treatment strategies for drug dependency. There is little to add, except to emphasise the need for continuing support services and harm-minimisation programs for those people who decide to embark on or continue with an injecting drug habit. Such support includes widespread availability of needle and syringe exchange programs and ready access to counselling and education facilities. Education includes strategies for primary and secondary prevention of injecting drug use, including diverting users to non-injecting routes of drug administration.

Does antiviral treatment have anything to offer as a strategy to prevent transmission? The combination of interferon alfa and ribavirin has now become the benchmark for treatment of HCV infection, with a long term response rate of over 40% -- double that of interferon alfa monotherapy. As the marker of response (the polymerase chain reaction test for viral RNA) measures viraemia, it can be assumed that those who "respond" are not infectious. It is expected that the combination therapy will be licensed for treatment-na•ve patients in Australia in 2000. Currently, combination treatment is licensed under section 100 (s100) of the National Health Act 1953 (Cwlth) for people who have relapsed after interferon alfa monotherapy.

With a response rate of over 40%, should we not be using this treatment in injecting drug users? The current s100 criteria for interferon alfa do not preclude treatment of current injecting drug users. However, there are three major potential problems which lead to caution in liver clinics. Firstly, there is the risk of reinfection: an injecting drug user needs to use scrupulous technique 100% of the time in order to avoid reinfection. Secondly, there is the risk of serious psychiatric effects with interferon alfa (psychotic reactions, cognitive impairment, severe depression including suicide attempts, and homicidal ideation),⁸ with suicides having occurred in Australia and overseas.⁹ Psychiatric reactions are more common in people with pre-existing psychological problems, chaotic lifestyles and those who lack social networks and supports. Interferon alfa can cause recidivism to injecting drugs, particularly in recent users, and this recidivism has been associated with major psychiatric problems.⁸ Unfortunately, funding for interferon in Australia has not been tied to any funding for counselling or psychiatric services.

Thirdly, the other drug, ribavirin, is clearly teratogenic at low dose in all animal species studied, and can potentially cause embryotoxicity from either male or female parents.¹⁰ Additionally, ribavirin may be present in semen and cause teratogenicity in a woman already pregnant. It has a large volume of distribution and a long half-life (298 hours; see product information, available from Schering-Plough Pty Ltd, PO Box 231, Baulkham Hills, NSW 2153). Thus, people contemplating a course of ribavirin must be counselled about contraception -- both men and women must make sure no pregnancies occur during treatment and for six months afterwards, and additionally there should be no unprotected intercourse with a woman already pregnant. The product information for ribavirin advises two separate methods of contraception, one for the male and one for the female of a partnership.

Clearly, at this stage, antiviral treatment cannot be safely advocated as a widespread public health method of reducing transmission of HCV in people who inject drugs. As a general rule it is safer to defer treatment until individuals have stopped injecting drugs for a long time, particularly as the rate of progression of HCV-related liver disease is so slow. While antiviral treatment may then be effective in clearing virus in those who have stopped injecting, it will have no effect on transmission, as these individuals are no longer part of the injecting population.

The emphasis must therefore remain on concerted efforts to reduce the numbers of Australians who inject drugs, to provide support during this period in their lives, to reduce the number of times they actually inject, and to promote a safe, "self defence" injecting technique with every injection. Maintenance and expansion of needle and syringe exchange programs will remain the single most important component of Australia's harm-minimisation efforts. Adherence to the principles of harm minimisation is the only way to control this epidemic until a vaccine becomes available -- and this is unlikely to occur within a decade.

Katrina J R Watson
Deputy Director
Department of Gastroenterology
St Vincent's Hospital, Melbourne, VIC

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