Antibody Testing and Lyme Disease Risk

Elizabeth G. Stone; Eleanor H. Lacombe; Peter W. Rand

Disclosures

Emerging Infectious Diseases. 2005;11(5):722-724. 

In This Article

Abstract and Introduction

Lyme disease test results for > 9,000 dogs were collected from participating veterinary clinics. Testing was conducted by using the IDEXX 3Dx kit, used widely by Maine veterinarians to screen clinically normal dogs during heartworm season. This study demonstrates how this test can be a valuable public health disease surveillance tool.

Lyme disease is the most commonly reported vectorborne disease in the United States; however, many experts believe that the number of cases is underreported. Lyme disease is often regarded as a routine condition or is frequently managed in high-volume settings.[1] Few studies have assessed the accuracy of passive Lyme disease surveillance systems, but 1 study showed a 34% reporting rate.[1] When tick identification services are offered, the identification data can show where disease vectors are found. In 1989, to determine the extent of the recently recognized infestation with Ixodes scapularis , the Maine Medical Center Research Institute's Vector-borne Disease Laboratory offered free tick identification to physicians, hospitals, veterinarians, and the general public. Since that time, > 20,000 ticks, representing 14 species, have been identified. Testing has documented Borrelia burgorferi infection in I. scapularis from all Maine counties except 3.

Mapping of ticks submitted for identification is subject to certain biases, which limits its utility for predicting human risk. Submission rates vary depending on population, education, and local concern, and results show little about disease transmission, particularly in disease-emergent areas where infection rates may lag behind tick distribution. The limitations of passive Lyme disease surveillance and tick identification that provide geographic information about risk can be largely overcome by using canine seroprevalence studies. Dogs are sensitive indicators because they have greater exposure to ticks. In disease-endemic areas, ≥ 50% of unvaccinated dogs have been reported to be infected.[2,3] The prevalence of Lyme borreliosis in dogs correlates with infection in humans,[4,5] as well as entomologic indicators of disease transmission.[6] A newly available enzyme-linked immunosorbent assay (ELISA) kit (SNAP 3Dx, IDEXX Laboratories, Westbrook, ME, USA) is used widely by veterinarians in Maine to screen dogs for B. burgdorferi and heartworm infection. This test is used as part of a health screen during the heartworm testing season and can potentially generate large volumes of unbiased test data for public health application.

The test kit detects antibodies directed against an invariable region (IR6) of the B. burgdorferi surface protein VlsE (Vmp-like sequence, Expressed).[2] The C6 ELISA test is not cross-reactive with antibodies induced by vaccination with either recombinant B. burdorferi outer-surface protein A (OspA) or whole-cell bacterin.[2] This test has a very high accuracy rate, with 94.4% sensitivity and 99.6% specificity reported.[7] In a clinical setting, when 18 dogs with known vaccination history were tested, the test results were 100% consistent with Western blot results.[8]

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