Meeting Abstract

7.4  Tuesday, Jan. 4  Estimating Duration of Infection Using Antibody Avidity Assays: A Potential Limitation VARNER, Johanna M*; DEARING, M. Denise; University of Utah; University of Utah

The number of recent infections in a host-pathogen system is often reflective of the rate of transmission, or force of infection. Traditionally, laborious mark-recapture studies have been necessary to estimate duration of infection in wildlife. Recently, avidity assays have been used to infer age of infection at individual and population levels; however, these assays may be confounded by antibody concentration. We examined the effect of titer on an enzyme-linked immunosorbent avidity assay for Sin Nombre virus (SNV), a Hantavirus primarily carried by the deer mouse (Peromyscus maniculatus). Avidity indices were positively correlated with anti-SNV serum antibody titers in infected animals; experimental dilution of titer in the avidity assay significantly decreased avidity scores. Furthermore, 20% of samples, mostly older infections with low titers, were misclassified as recent infections. These results suggest that the avidity assay classifies samples with low titers (including some older infections and uninfected juveniles with dilute maternal antibodies) as recent infections regardless of actual infection history. As a result, the assay tends to overestimate the number of recent infections in a population, which may lead to falsely high estimates of public health risk.