Atrophic Rhinitis (AR) and Progressive Atrophic Rhinitis (PAR)

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.

About AR and PAR

• Etiology
• Contributing Factors
• Clinical Signs
• Diagnosis
• Treatment and Control

Etiology
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.

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Contributing factors to Atrophic Rhinitis and Progressive Atrophic Rhinitis

• More common in young herds particularly those containing large numbers of gilts.
• Large permanently populated farrowing houses.
• Poor environmental conditions - poor ventilation, low humidity, dust
• The presence of other diseases such as Enzootic Pneumonia, PRRS, Haemophilus parasuis and Aujeszky's disease in the herd.

Milder rhinitis, non progressive disease, in which the turbinate bones heal and regenerate, may be caused by the following.

• Air containing high bacterial counts.
• Aujeszky's disease (pseudorabies).
• Bordetella bronchiseptica infection.
• Chronic respiratory disease.
• Dust.
• Glässers disease.
• High levels of ammonia.
• Porcine cytomegalovirus infection (inclusion body rhinitis).
• Porcine reproductive and respiratory syndrome (PRRS).
• Poor humidity

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Clinical Signs of Progressive Atrophic Rhinitis
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.

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Diagnosis
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 - 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.

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• Elimination of infection with toxigenic P. multocida prevents the development of the bony lesions and prevents production effects. Acute disease in piglets can be treated with potentiated sulphonamides, ampicillin, tetracyclines, ceftiofur or enrofloxacin. Support therapy such as additional food and electrolytes may be necessary.
• Weaned pigs at risk may be given a course of antimicrobial treatment in feed or water at therapeutic levels. Medication of groups of animals entering airspace in an all-in, all-out system is the most efficient method.
• Vaccination of sows with the toxoid (inactivated toxin) to give protection via the colostrum to piglets. See Vaccines.
• Infection can be eradicated by depopulation and restocking and clean herds may be maintained free from PAR by isolation and the use of clean breeding stock. Monitoring for infection is done by culture of nasal swabs for toxigenic P. multocida.

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Atrophic rhinitis: moderate conchae atrophia