Introduction: Chagas disease is a zoonotic tick-transmitted parasitic disease endemic in Latin American countries. In non-endemic countries it is mainly transmitted congenitally or via blood transfusion. There is an increased risk of spread outside South America as a result of migration of asymptomatic parasitemic individuals. A current WHO initiative is to identify strategies to reduce transmission in non-endemic countries to zero. While potential vectors occur in northern Australia only two cases in immigrants from South America have been reported here. The aims of this study were to estimate the risks for congenital and for transfusion transmission of Chagas disease in Australia.
Methods: Census data (2017) on immigration to Australia from South America, births and country of birth of the mother, as well as prevalence in source countries were used to estimate the risk of congenital transmission. The risk of a parasitemic donation was estimated on the basis of reported data from Canada.
Results: Following published methodology it was estimated that 3.37% of South American immigrants were potentially parasitemic, representing 5,971 individuals in Australia, with 2,023 females of childbearing age. For those females, it was estimated that there would be 90 births annually with 4.5 exposed, potentially parasitemic newborns. Based on published data from the Canadian Blood Service, it was estimated that 199 exposed potentially parasitemic individuals are likely to present to donate blood each year, with a risk of 3.6 antibody-positive donations.
Discussion: This study suggests that the risk both of congenital transmission and transfusion transmission is very low in Australia. In addition there is universal leukodepletion of the blood supply in Australia and published data suggests that this filtration step removes the trypanosomes with the result that there is zero risk.
While in Australia identifying Chagas disease in immigrants from endemic regions of South America is an emerging challenge for general practitioners, the risks for secondary congenital or transfusion transmission here are very low.