Porcine Mycoplasma hyorhinis Infection – NAVLE Study Guide

Overview and Clinical Importance

Mycoplasma hyorhinis (Mhr) is a small, wall-less bacterium belonging to the class Mollicutes. It is a ubiquitous pathogen in swine populations worldwide and a significant cause of polyserositis and polyarthritis in nursery-age pigs. Although commonly found as a commensal organism in the upper respiratory tract of healthy pigs, M. hyorhinis can cause significant economic losses due to decreased weight gain, increased mortality, and enhanced medical costs when systemic disease develops.

For the NAVLE, understanding M. hyorhinis is essential because it represents a high-yield topic within swine medicine, particularly regarding differential diagnosis of polyserositis (distinguishing it from Glasser disease and streptococcal infections), appropriate antimicrobial selection, and recognition of predisposing factors.

Etiology

Organism Characteristics

Mycoplasma hyorhinis is a member of the family Mycoplasmataceae, class Mollicutes. Key microbiological features include: