Dynamics of Coxiella Burnetii Dna in milk and phase-specific serological response in dairy cows

Abstract

In dairy cows shedding of Coxiella burnetii in milk can be persistent, sporadic to absent. Persistent heavy shedder cows are mostly highly-seropositive. Serological response due to C. burnetii antigenic phase demonstrates acute or chronic infection (serological response to phase II (PhII) or phase I (PhI) antigen, respectively). The aim of this study was to detect dynamics of C. burnetii DNA in milk and phase-specific serological response. In this study, the sera samples from 46 animals and milk samples from 34 were collected initially. Milk and sera samples from 36 animals were collected repeatedly. Samples were collected in five herds with previous history of C. burnetii infection from different parishes in Latvia - in 2017 and 2018. Milk samples were tested by detection of C. burnetii DNA by realtime PCR amplification using 'ADIAVET™ COX REALTIME' (ADIAGENE). Sera were tested by 'VetLine Coxiella Phase1 and Phase2 ELISA' (NOVATEC). Three cows (9%) in the first sampling and five (14%) in second sampling demonstrated shedding of C. burnetii DNA in milk. Six cows (13%) in the first sampling and eight (22%) in second sampling demonstrated positive serological response to PhI. Three cows (7%) in the first sampling and one (3%) in second sampling demonstrated a questionable serological response to PhI. Two cows (6%) in the second sampling demonstrated a questionable serological response to PhII. In herds with previous history of C. burnetii infection the number of animals demonstrating PhI positve serological response increases significantly (p < 0.05) during six months. In cows demonstrating positive serological response to PhI it continues and mostly remains unchanged during six months.