Babesiosis: Analysis of the Evidence for Infections in the United Kingdom.

Human babesiosis is caused when erythrocytes are invaded by Babesia. Infection can occur from the bite of an infected tick, blood transfusion or congenitally. Issues related to the infecting species, symptomology and testing technology are discussed and the implications of accurate incidence and prevalence of the disease discussed. Human babesiosis is considered to be relatively rare in the UK. With a considerable number of non-specific symptoms and diagnostic testing limitations, it is probable that true positives are being missed. Based on co-infection data for Borrelia and Babesia from Rhode Island and Connecticut, and on Borrelia seropositivity data from northeastern France, the prevalence of babesiosis in those aged under 35 years, 35 to 44 years, 45 to 54 years and 55 years and over would be expected to be 0.6%, 1.8%, 2.8% and 3.5%, respectively. Based on the prevalence of infections in ticks and canines and a disease model previously published, it is estimated that the UK incidence of human babesiosis is likely to be approximately 18,500 cases per year.