Mycoplasmal pneumonia of swine: Update and importance of the disease

Abstract

The paper provides an overview of updated knowledge on this common disease with a strong impact on pig production efficiency. Mycoplasma hyopneumoniae (Mhp), the etiologic agent of the condition, is the smallest self-replicating bacteria, distinguished from most other bacteria by the lack of a cell wall. Colonization of the respiratory cilia is a unique feature of Mhp, which results in a persistent presence of Mhp in the airways and creates a population of infected asymptomatic animals that continually expose other pigs to infection. The economic consequences of a long-term persistence of infection within the herd include a chronic reduction in feed efficiency and increased opportunity for co-infection with other respiratory pathogens, leading to PRDC (porcine respiratory disease complex) syndrome. Chronic Mhp infection in the form of a respiratory disease with high morbidity and low mortality has been estimated to affect up to 70% of pigs worldwide. Diagnostic tools include clinical diagnosis, examination of gross lesions and histopathology. Mycoplasma hyopneumoniaespecific laboratory tests are critical to identify asymptomatic carriers or to detect antibodies as a sign of endemic infection. Tools that demonstrate the presence of Mhp rely on visualizing the organism (culture, FIA) or on detection of nucleic acid (PCR) or antigen specific for that pathogen (ELISA). Control of Mycoplasma hyopneumoniae has been attempted by several widely practiced methods. These include sow vaccination programmes, early vaccination of suckling piglets, use of antibiotics at peak transmission times, introduction of piglet flow in the all-in/all-out system and a segregated system of pig production. Several Mhp elimination protocols have been developed and can be implemented to eradicate this pathogen from the herd. One of them is a partial depopulation procedure, which consists in depopulation of pigs below 9 months of age. The other animals are subjected to medication.