'One in a billion' chance of mad cow disease spreading through blood donation, NZ experts estimate

Embargoed until: Publicly released: 2023-08-25 00:01

New Zealand

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Two infectious disease experts are calling for blood donor policies in Aotearoa to be relaxed. In the year 2000, 10% of the population were unable to donate blood as they were in the UK during the mad cow disease epidemic of the 80s and 90s. Despite periodic blood shortages, the policy has remained in place, as the disease can lay dormant within a person for decades before they develop the fatal illness. However the researchers now estimate the chance of someone contracting mad cow disease from donated blood in NZ to be approximately one in a billion every year. With no new cases of mad cow disease globally since 2019, both Australia and Ireland have relaxed their blood donor policy rules, and the New Zealand authors call for the same to happen in Aotearoa.

Media release

From: Pasifika Medical Association Group

Aotearoa New Zealand excludes potential blood donors who lived in the United Kingdom for 6 months or more between 1980 and 1996. This policy is due to the “mad cow disease” epidemic in cattle there causing variant Creutzfeldt-Jakob disease (vCJD) in humans who could potentially pass on this infection through blood transfusions. As a result, 10% of New Zealand’s active blood donors were excluded, contributing to periodic shortages of some blood products. Cases of vCJD peaked 23 years ago in 2000 and are declining, with no new cases since 2019. Only three confirmed cases have ever been linked to a blood transfusion. We calculated the risk of relaxing these restrictions to lead to approximately 1 in 1 billion risk per year nationally, similar to a recent 1 in 1.45 billion estimate for Australia. This calculation suggests that relaxing current blood donation restrictions, like Ireland and Australia’s recent policy changes, would lead to an extremely low risk of vCJD transfusion transmission in New Zealand. This change would increase the supply of blood products for multiple medical needs.

Journal/
conference: NZMJ

Organisation/s: Massey University, University of Otago

Funder: N/A

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