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The Porcine Respiratory Complex and its characteristics


Animal diseases

The Porcine Respiratory Complex and its characteristics

In Spain, the pig sector is one of the most important livestock sectors, both in terms of production and sales. That is why the study of diseases that affect this cattle is so important. And among them the porcine respiratory complex stands out.

Generalities about the Porcine Respiratory Complex

Since the twentieth century, many infectious diseases are no longer understood as produced by a single microorganism, but are referred to multifactorial complexes. Within the swine species, one of the most relevant polymicrobial diseases is the porcine respiratory complex –CRP onwards–, where we include:

  • The SRRP virus – Porcine Reproductive and Respiratory Syndrome -.
  • Auzjesky’s disease.
  • The influenza virus.
  • The Porcine Respiratory Coronavirus.
  • The Circovirus
  • Mycoplasma spp.
  • Bordetella spp., Pasteurella spp.
  • Haemophilus spp., Streptococcus spp., Escherichia coli

There are a number of pathogenic mechanisms that favor this type of diseases, such as:

  • The synergies of the different agents.
  • The blockage of the immune system.
  • Alterations of the respiratory mucosa.
  • Metabolic, physiological and physical alterations.
  • The release of inflammatory components that will increase the severity of the disease.

Description of the porcine respiratory complex

This disease constitutes one of the most complex clinical pictures with the greatest negative impact on pig production.

It is a very frequent pathology in intensive pig farms, although it also occurs, to a lesser extent, in extensive farms. It causes large economic losses, derived from the delay in the fattening of animals, and in the multiple slaughter needs.

Primary pathogens

Within the CRP there are primary pathogens, capable of altering defense mechanisms and establishing themselves in the pig host. If they are the only pathogens involved in the disease, this usually remits in a short time.

The problem is in the complications developed with the presence of secondary or opportunistic pathogens. This generates much larger economic losses.

Opportunistic pathogens

The rest of pathogens are considered “opportunistic”, because they take advantage of the virulence factors of the previous ones to also trigger a disease. Depending on the interactions and the complexity of the process, some microorganisms may behave as “primary” agents or as “opportunists.” But others are unequivocally linked to one of the two categories.

What does the pig eat

The evolution of the porcine respiratory complex

During the last 30 years there have been substantial changes in pig production. It has gone from extensive production to the proliferation of intensive farms with a high density of animals. And this favors the spread of respiratory diseases.

Factors that favor the onset of the disease

First, overpopulation, coupled with poor ventilation, become a powerful ally of stress. To this are added, secondly, high levels of dust and ammonia, which generate a negative impact on the respiratory system of pigs.

And thirdly, other negative factors, such as the constant flow of animals, with the arrival and departure of individuals constantly, aggravating the spread of diseases. In addition, most respiratory pathogens are very ubiquitous, and it becomes almost impossible to find a batch of animals completely free of them.

Critical moments for the porcine respiratory complex

Even when sanitary conditions are maximized, there are critical moments for the appearance of the complex. For example, when maternal immunity drops – after weaning – where piglets are more likely to become infected. In turn, diseases can enter the farm through vectors, new animals, wild animals, and even the operators themselves.

Porcine Respiratory Complex


To conclude, the multifactorial etiology of the CRP can vary, not only between countries, but between different production systems. And within the same farm, it can vary over time. Therefore, its study is highly complex, although necessary.

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