Effect of enzootic pneumonia of pigs on growth performance

Growing pigs were naturally infected with a field strain of Mycoplasma hyopneumoniae to assess the effect of enzootic pneumonia on production. Both the initial ("breakdown") and endemic stages of infection were evaluated. The pigs were reared under environmental and management conditions commonly found on commercial piggeries in South Australia. Growth rate of pigs held in-contact with inoculated pigs was reduced by 12.7% (p less than 0.01) between 50 to 85 kg bodyweight. In the second trial inoculated gilts were used to naturally infect piglets during suckling. Growth rate of infected pigs was reduced by 15.9% (p less than 0.001) between 8 to 85 kg bodyweight, while feed conversion was depressed by 13.8% (p less than 0.05) between 10 to 25 kg bodyweight. At current feed and production costs this reduced performance added approximately $2.80 to the cost of every pig produced. These losses were recorded in groups of pigs in which enzootic pneumonia was present. At slaughter, 40% of lungs contained gross lesions of enzootic pneumonia which were free of significant secondary bacteria. The nature of the infection was established by gross and microscopic pathology and confirmed by the detection of specific complement fixing antibody in infected pigs and the demonstration of M. hyopneumoniae by direct immunofluorescent staining of lung sections.     

Value of the clinical examination in diagnosing enzootic pneumonia in fattening pigs

The diagnosis of enzootic pneumonia at the herd level should be based on a combination of different methods. Currently, clinical examination is usually considered to be a low value method, particularly compared to the direct detection of Mycoplasma hyopneumoniae in lung lesions by PCR. The present study compared the value of accurate clinical examination (including the quantitation of coughing), PCR on bronchoalveolar lavage fluid, and serological testing of blood samples for the purpose of diagnosing enzootic pneumonia. The coughing index (average % of pigs coughing per minute of observation) was determined in fattening pigs from 59 herds, and ranged from 0% to 6.7% with a median of 2.4%. Five hundred and ninety bronchiolar lavage samples and 1179 serum samples were taken from pigs in those 59 herds and tested for M. hyopneumoniae specific DNA and antibodies, respectively. In herds where ?50% of lavage fluids were PCR positive, the likelihood of a higher coughing index was increased by 76% (OR: 1.76; 95% CI: 1.14-2.72) compared to herds with <50% of positive samples. For antibodies (determined by ELISA) a seroprevalence of ?50% increased the likelihood of a high coughing index by 50% (OR: 1.50; 95% CI: 1.03-2.20). In 78.1% of all herds with a seroprevalence of ?50% against M. hyopneumoniae, the PCR-prevalence and the coughing index were above the median (50% and 2.4%, respectively). It was concluded that in fattening pigs a quantitative assessment of the onset of coughing - typically dry and non-productive - improves the diagnosis of enzootic pneumonia and can occasionally substitute for the detection of M. hyopneumoniae by PCR.     

Experimental chlamydial pneumonia in pigs

Naturally occurring disease in pigs associated with chlamydial infections has not been reported in Britain, though evidence of chlamydial challenge has been demonstrated in two separate serological surveys. An isolate of Chlamydia psittaci (28/68) from an ovine pneumonia produced pneumonia in pigs following intratracheal inoculation. Transient pyrexia at 24 hr was followed by increased respiratory rates and inappetance which lasted for a further 48 hr in challenged pigs. Histologically acute exudative reactions were present in the lungs by 24 hr with proliferative changes predominating after 10 days. While variations in the concentrations of inocula were reflected by corresponding increases and/or decreases in gross lung damage, clinical signs and histological reactions were unaltered. Chlamydial organisms were recovered only from lung tissues.     

A system response to an outbreak of enzootic pneumonia in grow/finish pigs

A Mycoplasma hyopneumoniae-negative commercial swine production system broke with enzootic pneumonia at their grow/finish site in southern Manitoba in October, 2003. System responses included feed medication, depopulation, delayed shipment of pigs to the infected site, vaccination of at risk sow herds, and disinfection when grow/finish site depopulation was completed.