Abstract
BackgroundThe objective of our study was to clinically and etiologically investigate acute outbreaks of respiratory disease in Finland. Our study also aimed to evaluate the clinical use of various methods in diagnosing respiratory infections under field conditions and to describe the antimicrobial resistance profile of the main bacterial pathogen(s) found during the study.MethodsA total of 20 case herds having finishing pigs showing acute respiratory symptoms and eight control herds showing no clinical signs suggesting of respiratory problems were enrolled in the study. Researchers visited each herd twice, examining and bleeding 20 pigs per herd. In addition, nasal swab samples were taken from 20 pigs and three pigs per case herd were necropsied during the first visit. Serology was used to detect Actinobacillus pleuropneumoniae (APP), swine influenza virus (SIV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine respiratory coronavirus (PRCV) and Mycoplasma hyopneumoniae antibodies. Polymerase chain reaction (PCR) was used to investigate the presence of porcine circovirus type 2 (PCV2) in serum and SIV in the nasal and lung samples. Pathology and bacteriology, including antimicrobial resistance determination, were performed on lung samples obtained from the field necropsies.ResultsAccording to the pathology and bacteriology of the lung samples, APP and Ascaris suum were the main causes of respiratory outbreaks in 14 and three herds respectively, while the clinical signs in three other herds had a miscellaneous etiology. SIV, APP and PCV2 caused concurrent infections in certain herds but they were detected serologically or with PCR also in control herds, suggesting possible subclinical infections. APP was isolated from 16 (80%) case herds. Marked resistance was observed against tetracycline for APP, some resistance was detected against trimethoprim/sulfamethoxazole, ampicillin and penicillin, and no resistance against florfenicol, enrofloxacin, tulathromycin or tiamulin was found. Serology, even from paired serum samples, gave inconclusive results for acute APP infection diagnosis.ConclusionsAPP was the most common cause for acute respiratory outbreaks in our study. SIV, A. suum, PCV2 and certain opportunistic bacteria were also detected during the outbreaks; however, viral pathogens appeared less important than bacteria. Necropsies supplemented with microbiology were the most efficient diagnostic methods in characterizing the studied outbreaks.
Highlights
The objective of our study was to clinically and etiologically investigate acute outbreaks of respiratory disease in Finland
The season of the first herd visit was relatively similar in case and control herds: spring 20% of case vs. 0% of control herds, summer 20% vs 25%, autumn 25% vs. 50% and winter 35% vs. 25%
Most of the herd visits were done during the year 2012 (60% of case and 62% of control herds), because that was the time when farmers and practicing veterinarians were actively informed about the project
Summary
A combination of pathogens are involved, e.g. viruses such as porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV2), swine influenza virus (SIV), porcine respiratory coronavirus (PRCV), and various bacteria e.g. Actinobacillus pleuropneumoniae (APP), Mycoplasma hyopneumoniae (MHyo), Mycoplasma hyorhinis, Haemophilus parasuis (H.parasuis), Pasteurella multocida and Streptococcus suis [1,2,3,4,5,6] Often it remains unclear which the primary pathogen is and which one is acting as a predisposing agent for other infections or as a secondary infection [2, 6, 7]. Overall, assessing which respiratory pathogens are involved in acute respiratory disease outbreaks in a country lacking major viral pathogens is very important
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