New findings suggest that sharing paraphernalia used to cook and prepare injection drugs does not directly lead to transmission of hepatitis C virus.
According to Robert Heimer, PhD, professor of epidemiology and pharmacology at the Yale School of Public Health, and colleagues, this contrasts with past epidemiological studies that reported HCV incidence linked to sharing “cookers” and filters. Heimer said those studies were not clear on whether the results reflected the contamination of such paraphernalia or syringe-mediated contamination among people who inject drugs (PWID).
Heimer and colleagues used lab studies to show that transmission occurs via the needles used in preparing and injecting drugs, not through shared paraphernalia. In light of their results, they said syringe access programs should not spend their limited resources on providing “cookers” and filters to PWID. Instead, Heimer and colleagues said they should focus on distributing more syringes with fixed needles, which are less apt to harbor infectious HCV than those with detachable needles.
HCV is prevalent among PWID, reaching universal levels in some populations, according to Heimer and colleagues. Their experiments attempted to replicate a common scenario in which PWID share bags or balloons of drugs.
“These findings suggest it may not be HCV in shared ‘cookers’ and filters that leads to transmission, but instead that this kind of sharing is a surrogate for situations in which HCV-discordant injectors share drugs,” Heimer and colleagues wrote in The Journal of Infectious Diseases.
“In this scenario, injectors collectively prepare drugs. If a contaminated syringe was used to add water, dissolve and apportion the drug, then some of the contents of the contaminated syringe would pass through the ‘cooker’ and filter and into the syringe of the uninfected person. In such a case, the ‘cookers’ and filters may not even harbor infectious virus, and the distribution of clean ones and warnings about sharing them may have little or no impact on HCV incidence.”
To replicate the real-world scenario in which an injector with HCV shares drugs with an HCV-uninfected person, Heimer and colleagues prepared syringes containing residual liquid contaminated with the virus and used them to simulate the preparation of the next injection, passing the contents through the “cookers” and filters used to prepare the injections and then introducing them into a second syringe. The contents of the syringes, “cookers” and filters were then entered into a microculture system for testing.
In their experiments, Heimer and colleagues could not recover HCV from “cookers” regardless of input syringe type or “cooker” design — in the study, ridged or smooth caps resembling soda bottle tops were used. HCV was recovered in 15.4% of filters when detachable needles were used, compared with 1.4% when fixed needles were used. Recovery of HCV was higher when comparing detachable needles with fixed needles for residue in input syringes (73.8% vs 0%) and receptive syringes (93.8% vs. 45.7%).
Heimer and colleagues said past findings linking HCV transmission to shared “cookers” and filters have led to syringe access programs providing clean “cookers” and filters to PWID, but no evidence exists showing that this intervention reduces HCV incidence. They said their results should lead to a rethinking of these policies.
“At a minimum, our findings should compel programs that serve PWID to focus more on the process of drug preparation and injection and less on the preparation paraphernalia,” they wrote. “Going further, programs may want to reconsider expanding scarce resources to provide supplies that will do little or nothing to prevent HCV transmission. Given the usual situation of limited financial resources facing syringe exchange and related harm-reduction programs, spending money on objects that can have little impact on disease transmission should come to be viewed as profligate.”
By Gerard Gallagher