Identification and Distribution of Causative Agents of Pleurisy in the Brazilian Pig Farming

Abstract

Background: Pleurisy is defined as an inflammation of the pleural membranes, usually caused by bacterial infections. It is considered the second most common reason for condemnations of swine carcass during slaughter. Prior to slaughter, pleurisy can causes discomfort to the animals, and during the slaughter, the carcass from affected animals, has to be trimmed, reducing the value to both the farmer and the plant, increasing the costs of disposal, and line speeds are reduced, increasing processing costs. The objective of this study was to verify the prevalence and to identify the bacterial agents associated with pleurisy lesions in pigs.
Materials, Methods & Results: In this study, were used tissue samples from 4,536 piglets collected from the main swine producing regions of Brazil between the years 2013/2014. Samples were collected from animals that presented respiratory, enteric or nervous symptoms. Samples were sent to pathology and bacteriology examinations in a commercial laboratory. The pathogen isolates were classified according to the agent Pasteurella multocida (P. multocida), Haemophilus parasuis (HPS), Streptococcus suis (S. Suis), Actinobacillus pleuropneumoniae (APP) and Bordetella bronchiseptica (BB) stage of development and regional location of the case. Data were analyzed based on the frequency according to the age group using Fisher-test. Of the total number of animals with clinical cases investigated in this study, 10.63% of them presented pleurisy lesions. When investigating the pleurisy frequency among the states or regions, we have observed that the state of Santa Catarina had the higher prevalence of pleurisy with 35.06% of cases, followed by the state of Minas Gerais with 35.31%, Rio Grande do Sul with 17.22% Paraná with 9.75% and the Midwest region had the lower prevalence with 6.02% of cases. Out of the total isolates, HPS were isolated in 55.0% of the total; P. multocida 31.0%; S. suis 7.0%; APP 6.0% and BB 1.0%. The higher prevalence of HPS was identified in southern states, while in MG, Southeast and Midwest there was equality between HPS and P. multocida isolations. The prevalence of HPS (P < 0.05) was in the nursery phase. P. multocida and APP prevailed in the growth and fattening phases.
Discussion: In the swine industry, respiratory problems are responsible for huge economic losses caused to the animals, including treatment, condemnation of carcass up to the death of the animal, without including the animal pain and discomfort condition. Our data support the previous findings that P. multocida, was observed in higher frequency in the phase of growth (54.08%) and finishing (29.85%), being responsible to 83.93% of the cases in those phases. Therefore it could be considered the most economically important agent, since the HPS lesions are repaired over time, having low identification at later ages and slaughter of the pig. Similar findings were observed with APP. The S. suis and BB have been identified in sporadic forms. Knowing the possible agente causing the lesion based on the animal age and country region it is easier to predict with higher chances better management techniques to prevent the pathogen occurrence or even indicate a better treatment to reduce the lesion levels. Our data supported hypotheses of the identification of clinical cases and the animal growth stage for the most accurate classification for the success of animal treatment.