Laboratory Diagnosis of Tick-Borne Infections

Potential Disadvantages

July 2010

Another potential disadvantage of PCR in this setting is that PCR may detect residual DNA when no viable organism is present. In a study by Krause and colleagues, babesial DNA persisted for a mean of 16 days in 22 subjects following treatment, so it can take some time to clear all of the DNA from the blood stream. Also, PCR tests for babesiosis may not detect all species, and the clinician needs to be familiar with the specificity of the test used by the laboratory.

In addition to Babesia microti, there are several different species of Babesia that cause human babesiosis, including Babesia divergens, Babesia duncani (which was previously referred to as WA-1 because it was first isolated in Washington state), and the newly described MO-1 strain from Missouri State. And these organisms are genetically distinct; so they may not be detected by PCR assays that are specific for Babesia microti.

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Jump to section:

• Introduction
• Presentation Outline
• Tick-Borne Diseases
• Advantages and Limitations of Conventional Tests
• Molecular Diagnostic Methods Potential Advantages
• Molecular Diagnostic Methods Potential Disadvantages
• Treatment and Diagnostic Recommendations
• Case 1
• Diagnostic Workup
• Representative Image Giemsa-stained Peripheral Blood Smear
• Differential Diagnosis
• Which one is Plasmodium falciparum?
• Main Morphologic Features Table
• Classic Maltese Cross
• Extracellular Forms of Babesiosis
• Side-by-Side Comparison
• Further Workup
• Malaria PCR
• Babesia microti PCR
• Advantages/Uses of PCR
• Potential Disadvantages
• Potential Disadvantages
• Case 2
• Lyme Disease: Diagnostic Approach
• Reported Cases of Lyme Disease, 2008
• Serologic Assay: Test of Choice for Diagnosis of Lyme Disease
• Case 2, Further Workup
• Potential Roles for PCR
• Which Specimens Should be Tested by PCR?
• PCR for Detection of Borrelia burgdorferi DNA in Blood
• Case 3
• Live Tick Image
• Tick Image Close Up
• IDSA Guidelines
• IDSA Guidelines, continued
• Testing of Ticks by PCR
• Case 4
• Tick-Borne PCR Panel
• Diagnostic Tests for HME and HGA
• PCR for Diagnosis of Ehrlichiosis/Anaplasmosis
• Ehrlichia and Anaplasma PCR Assay Graph
• Phylogenetic Tree
• Ehrlichia muris-like Organism
• All Patients with EML had Tick Exposure
• Prevention of Tick-Borne Diseases
• Conclusions
• Conclusions, continued
• Questions?