Table 1. Brief description of main clinical signs and lesions produced by the respiratory pathogens assessed. The type of assay carried out to diagnose them is also shown.

Pathogen	Type of assay	Clinical signs and lesions	Source
Bacteria
Mycoplasma hyopneumoniae	blocking-ELISA	Associated with Enzootic Pneumonia, M. hyopneumoniae plays a primary role in the porcine respiratory complex causing important economic losses.	[60]
Actinobacillus pleuropneumoniae	PCR	It causes pleuropneumonia that results in death, chronic or subclinical disease causing losses by mortality, reduced production, and increased costs of medication or vaccination.	[61]
Haemophilus parasuis	PCR	It is the etiological agent of the porcine arthritis poliserositis (Glasser's Disease) that may produce important losses mainly in intensive farm. Pneumonia in pigs as a primary or secondary agent.	[62]
Viruses
Porcine Circovirus type2	indirect-ELISA	PCV2 infection has been associated with postweaning multisystemic wasting syndrome (PMWS), porcine dermatitis and nephropathy syndrome (PDNS), porcine respiratory disease complex, and reproductive disorders.	[63]
Aujeszky's Disease Virus	indirect-ELISA	May produce high mortality in piglets with neurological disorders. Weaners may show pneumonic symptoms whereas in non-immune sows may produce reproductive disorders.	[64]
Swine Influenza virus	indirect-ELISA	Cause of bronchointerstitial pneumonia and respiratory disease in pigs throughout large parts of the world.	[65]
Porcine Reproductive and Respiratory Syndrome virus	indirect-ELISA	PRRSV infections produce severe reproductive losses, interstitial pneumonia in pigs, reduction of growth performance, and increased mortality.	[66]
Helminths
Metastrongylus spp	Direct retrieval at necropsy	It produces chronic granulomatous pneumonic lesions mainly in caudal lobes of the lungs. Cough with minimal other signs.	[67]