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However, current transmission of HCV infection in Australia is
occurring largely within the culture of injecting drug use. Although
the risk of transmission by an individual needlestick is not high (up
to 6.1%4), the high prevalence of HCV
infection among users, the frequency of injecting and the practices
used have established a self-perpetuating system of
transmission.5,6 Thus, it is likely that the
future disease burden of hepatitis C-related illness in Australia
will be carried largely by current or past injecting drug users.
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
- Seeff AB. Natural history of hepatitis C. Hepatology 1997;
26 (3 Suppl): 215-285.
-
Zekry A, Whiting P, Crawford D, et al. Long term outcome of hepatitis
C virus infection post liver transplantation. The Australian and New
Zealand experience [abstract]. J Gastroenterol Hepatol
1999; 14: A171.
-
Roberts SK, Sulaiman N, Giles G, et al. Rising incidence and risk
factors for hepatocellular carcinoma in Victoria [abstract]. J
Gastroenterol Hepatol 1999; 14: A194.
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Dore G, Kaldor J, McCaughan G. Systematic review of the role of
polymerase chain reaction in defining infectiousness among people
with hepatitis C virus. BMJ 1997; 315: 333-337.
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Crofts N, Thompson S, Kaldor J. Epidemiology of the hepatitis C
virus. Communicable Diseases Intelligence Technical Report Series
No. 3. Canberra: National Centre for Disease Control, Commonwealth
Department of Health and Aged Care, and Communicable Disease Network
Australia and New Zealand, May 1999.
-
Australian National Council on AIDS and Related Diseases
Hepatitis C Sub-Committee. Hepatitis C Virus Projections Working
Group: estimates and projections of the hepatitis C virus epidemic in
Australia. Sydney: National Centre in HIV Epidemiology and Clinical
Research, University of NSW, August 1998.
-
MacDonald MA, Wodak AD, Dolan KA, et al. Hepatitis C virus antibody
prevalence among injecting drug users at selected needle and syringe
programs in Australia, 1995-1997. Med J Aust 2000; 172:
57-61.
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Dusheiko G. Side effects of alpha interferon in chronic hepatitis
C. Hepatology 1997; 26 (Suppl 1): 1125-1215.
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Hepatitis C National Data Base Project. Final report 1999.
Newcastle: Hepatitis C National Data Base, 1999.
-
Kochbar DM. Effects of exposure to high concentrations of
ribavirin in devloping embryos. Pediatr Infect Dis J 1990; 9
(9 Suppl): S88-S90.
©MJA 2000
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