# Specificity Evaluation of a Polyprotein‐Based ELISA Designed for the Detection of Paratuberculosis in Multiple Species

## TL;DR

This study evaluates a new ELISA test for paratuberculosis that shows high specificity in detecting the disease in cattle and other species.

## Contribution

The study introduces a Map polyprotein-based ELISA with improved specificity for diagnosing paratuberculosis.

## Key findings

- Cross-reactivity was negligible or low in cattle, swine, and goats.
- Cross-reactivity ranged between 10% and 12.5% in sheep and cervids.
- The polyprotein-based ELISA is a valuable tool for specific PTB diagnosis in herds.

## Abstract

Paratuberculosis (PTB) is a disease affecting ruminant animals. The etiological agent, Mycobacterium avium subspecies PTB (Map), is a short, Gram‐positive, acid‐fast bacillus. Due to the nature of PTB, diagnosis often occurs at advanced stages of the disease, following the onset of clinical symptoms and prior dissemination of the agent. The specificity of current humoral diagnostic techniques, such as ELISA, is limited, mainly due to the presence of various species of mycobacteria in the environment and other closely related pathogenic mycobacteria that can interfere with the accurate diagnosis of PTB due to the high rate of gene conservation within the genus. In the present study, we evaluated the effectiveness and specificity of an ELISA based on a Map polyprotein for diagnosing bovine PTB. The efficacy of the polyprotein‐based ELISA was assessed using serum samples from healthy, Map‐infected, and Mycobacterium bovis (MB)‐infected cattle. Specificity was further evaluated using serum samples from healthy and MB‐infected wild animals. Our findings revealed that in most cases, the degree of cross‐reactivity was negligible or low, particularly in cattle, swine, and goats, while it ranged between 10% and 12.5% in sheep and cervids, respectively. These results suggest that the Map polyprotein used in the ELISA represents a valuable tool for the specific diagnosis of PTB in herds.