Respiratory diseases on pig farms are among the most serious problems affecting the development of the livestock industry. They are known as the “three no” diseases: they do not cause death, do not support growth, and do not resolve.

 

I. Determine the type of respiratory disease

 

Symptoms of uncomplicated respiratory disease include coughing, difficulty breathing, reduced appetite, lower feed utilization, and slower growth. Overall mortality is not high, but the disease has a serious impact on the economic performance of pig farms. Respiratory diseases involving mixed infections are mainly caused by coinfection with Mycoplasma pneumoniae, PRRS virus, porcine circovirus type II, and parasites. Clinical symptoms include acute abdominal breathing, severe difficulty breathing, persistent fever, and a sharp drop in feed intake; some pigs may even refuse to eat. Mortality is extremely high. 

 

II. Identify the causes of respiratory disease

 

1, Infectious factors

 

During disease outbreaks, large numbers of bacteria and viruses proliferate in pig barns. When the herd’s resistance declines, pathogens that cause endogenous infections are activated, triggering outbreaks of respiratory disease. Respiratory disease can also be caused by introducing breeding pigs or piglets from outside without quarantining them, or with an insufficient quarantine period, leaving pathogens not fully eliminated.　　

 

 

2, Feeding and management factors

 

During periods when respiratory diseases are prevalent, some pig farms use dry feeding, which results in more dust in the pig houses. High stocking density, enclosed pig houses, and poor ventilation lead to high ammonia and carbon dioxide concentrations. When the ammonia concentration in a pig house exceeds 50 ppm and the carbon dioxide content exceeds 0.2%, this can damage the respiratory mucosa and increase harmful substances in the blood, triggering respiratory inflammation. Respiratory diseases are especially prevalent in late autumn, winter, and spring.　　

 

3, Pathogen infection

 

The main pathogens that cause respiratory diseases include Mycoplasma pneumonia, contagious pleuropneumonia, Haemophilus parasuis, atrophic rhinitis, and swine pasteurellosis. Almost 80% of pig farms have Mycoplasma pneumonia infection, making it the most common respiratory disease (asthma). It can occur during the piglet weaning, nursery, and fattening stages.　　

 

 

4, Viral infection

 

These mainly include porcine reproductive and respiratory syndrome, pseudorabies, and swine influenza. Respiratory disease caused by PRRS is most apparent in piglets in the farrowing room and in nursery pigs; porcine circovirus type II infection can cause pneumonia in nursery pigs; swine influenza is common during seasons with pronounced temperature fluctuations, spreads rapidly, and lasts only a short time.　　

 

5, parasitic infection

 

These respiratory diseases are mainly caused by larvae or adult worms of pig roundworms, Metastrongylus, and lungworms parasitizing the bronchi and bronchioles of pigs. Before death, eggs can be detected in pig feces; after death, the presence of worms in the trachea, lungs, and intestines can be used to make a diagnosis.　　

 

Once the cause has been identified, pig farmers can administer the appropriate treatment and treat respiratory diseases in pigs more effectively.