Researchers have demonstrated interactions between Porcine Reproductive and Respiratory Syndrome virus (PRRSV) and respiratory infectious agents such as swine influenza virus (1), porcine respiratory corona virus (1), Mycoplasma hyopneumoniae (2), Streptococcus suis (3,4), and Salmonella cholerasuis (5). In Denmark, field observations of increased within-herd seroprevalence of Salmonella enterica have been made concurrently with recent infection of PRRSV. We were interested in investigating whether these observations were random findings or whether recent infection with PRRSV alter the within-herd seroprevalence of Salmonella enterica.