Current state and future trends in the diagnosis of babesiosis

Abstract

An overview is given of the currently available methods to diagnose babesiosis in livestock. Microscopic techniques are still the only appropriate techniques to diagnose acute disease. Thin or thick blood films stained with Giemsa's stain are sufficient. The sensitivity ranges from 10(-5) to 10(-6), i.e. one parasite per 10(5)-10(6) erythrocytes can be detected. Thick films stained with acridine orange (sensitivity approximately 10(-7)) and the Quantitative Buffy Coat (QBC) analysis tube system (sensitivity approximately 10(-7)-10(-8)) are applicable for diagnosis in the laboratory. DNA probes are very specific tools to identify haemoparasites in organs post mortem and in ticks. For the identification of carrier animals the sensitivity (approximately 10(-5)-10(-6)) is generally not sufficient. For the latter the polymerase chain reaction (PCR) technique is a very powerful tool (sensitivity approximately 10(-9)). Many different serodiagnostic tests have been described; however, the immunofluorescence antibody test is the most widely used, while the enzyme-linked immunosorbent assay (ELISA) is the test system which holds the greatest promise for the future. Thus far, improvements to the ELISA have been limited as the quality of antigen preparations made from infected blood is generally poor with a few exceptions (Babesia bovis, Babesia caballi). Potentially, most of the problems associated with crude antigens can be overcome by the production of recombinant antigens. Several ELISAs based on highly defined recombinant antigens have been described and show promise. None of these tests has been validated to the extent that it could be applied globally. Future research requirements as well as the need for coordination of the research effort and collaboration between institutions involved in the diagnosis of babesiosis are discussed.