Rhinitis in pigs is very common and can be caused by a variety of bacteria and irritant substances. Rhinitis may result in damage of the nasal turbinates.
Progressive Atrophic Rhinitis (PAR) describes a specific disease where the nose tissues permanently atrophy. It is caused by specific toxin producing strains of Pasteurella multocidia.
Pasteurella multocida is a normal commensal in the respiratory tract of pigs. The strains causing Progressive Atrophic Rhinitis (PAR) produce a powerful toxin, the dermonecrotoxin, which is responsible for the changes seen in the disease. Pasteurella multocida can easily be cultivated and recognized by the colony produced, but strains involve in PAR can only be distinguished by demonstrating their ability to produce toxin.
Pasteurella multocida will only colonise the nasal passages in sufficient numbers to cause disease if the mucosae are already. The damaging agent is usually the bacterium Bordetella bronchiseptica which causes inflammation in the nasal cavity and allows P. multocida to grow produce toxins and cause disease.
Toxins produced are absorbed and affect bone production and remodeling. In young fast growing piglets the nasal bones become distorted.
Milder rhinitis, non progressive disease, in which the turbinate bones heal and regenerate, may be caused by the following.
Clinical Signs of Progressive Atrophic
In piglets between 1 and 8 weeks of age sneezing, snuffling, nasal discharge, tear staining and sometimes nosebleeds may be seen. The sneezing gradually lessens but after 14 days bony changes become visible. As the disease progresses, the upper jaw become displaced and grows slower than the soft tissue and lower jaw. The skin over the snout appears corrugated and the lower jaw protrudes. Signs of pneumonia or stunting may also be seen. Severally affected animals may have difficulty in eating and the nasal changes may be seen in pigs of all ages in affected herds. Daily weight gain is reduced.
In some animals, sneezing may be transitory with few other clinical signs but turbinate atrophy may be found at slaughter. This form is most common where infection does not occur until after weaning and or where immunity is present.
Diagnosis is based on clinical signs. Progressive atrophic rhinitis should be considered when outbreaks of severe sneezing occur in piglets and further evidence is provided by the changes in the snout which appear as the piglets age.
The disease is easily identified by post-mortem examinations of the nose and culture of the organism from nasal swabs. At slaughter the snout is sectioned at the level of the second premolar tooth and an assessment of the degree of atrophy of the turbinate bones made. The snouts are graded from 0 to 5.
|Grade 0||Normal snout|
|Grade 1||Slight loss of symmetry of the nose|
|Grade 2||A slight loss of turbinate tissue|
|Grade 3||A moderate amount of loss of turbinate tissue|
|Grades 4 and 5||Severe progressive loss of tissue, PAR suspected|
Grade 0 - snout not affected, intact conchae
Grade 3 - moderate loss of turbinate tissue
Culture of the toxigenic P. multocida from nasal swabs and demonstration of the toxin confirms the diagnosis of PAR.
Antibody to the toxin can be demonstrated in serum from recovered and vaccinated pigs.