Description, Causes and Risk Factors:
Atrophic rhinitis is the term commonly used to refer to the condition of a sneezing pig with a crooked, bleeding snout and tear-stained face. The term “atrophic” means that the turbinate bones inside the snout are shrunken and distorted. These bones are lined with mucous membranes and filter the air the pig inhales, and so they are vulnerable to irritation and infection by changes and contaminants in the environment. Atrophy of the turbinate bones without external signs, like a crooked nose, is called “turbinate atrophy.” Producers and veterinarians often refer to any or all of these conditions as atrophic rhinitis.
The etiology is complex and involves at least two organisms. Various infections (eg, inclusion body rhinitis and pseudorabies) and noninfectious agents (eg, dust or high ammonia levels) cause sneezing and tear-staining, usually without leading to atrophic rhinitis. Bordetella bronchiseptica has long been implicated as a major cause. This bacterium is not host-specific, although strains that cause atrophic rhinitis are generally isolated only from pigs. Dogs, cats, rodents, and other species may harbor B bronchiseptica for long periods, but their role in the spread of atrophic rhinitis in pigs is uncertain. Certain toxigenic strains of Pasteurella multocida (types A and D), often acting with B bronchiseptica , cause permanent turbinate atrophy and nasal distortion. Both organisms can cause clinical atrophic rhinitis. The disease has been divided into 2 forms: nonprogressive atrophic rhinitis, due to B bronchiseptica , is mild and transient and probably does not greatly affect the animal's growth and performance; progressive atrophic rhinitis, due to toxigenic P multocida , is severe, permanent, and usually accompanied by poor growth.
Outbreaks of disease usually follow either the introduction of infected pigs or mixing of pigs from different sources. Piglets may be affected at any age, especially with P multocida , which also may infect mature animals. Crowding, inadequate ventilation, mixing and moving, and other concurrent diseases are important contributory factors in intensification of the disease.
Acute signs, which usually appear at 3-8 weeks of age, include sneezing, coughing, and inflammation of the lacrimal duct. In more severe cases, nasal hemorrhage may occur. The lacrimal ducts may become occluded, and tear stains then appear below the medial canthi of the eyes. Some severely affected pigs may develop lateral deviation or shortening of the upper jaw, while others may suffer some degree of turbinate atrophy with no apparent outward distortion. The degree of distortion can be judged from the relationship of the upper and lower incisors if breed variations are considered. In addition to the above clinical signs, outbreaks frequently impair growth rate and feed conversion.
The severity of atrophic rhinitis in a herd depends largely on the presence of toxigenic strains of P multocida, the level of management, and the immune status of the herd. The latter is related to both vaccination status and the parity distribution of the sow herd, because younger sows tend to shed more organisms and produce less lactogenic immunity for their nursing piglets than do older multiparous sows.
Lesions: The degree of atrophy and distortion is best assessed by examining a transverse section at the level of the second premolar tooth (the first cheek tooth, up to 7-9 mo of age); some recommend additional parallel sections. In the active stages of inflammation, the mucosa has a blanched appearance, and purulent material may be present on the surface. In later stages, the nasal cavities may be clear, but there may be variable degrees of softening, atrophy, or grooving of the turbinates; deviation of the nasal septum; and asymmetric distortion of the surrounding bone structure.
The findings of atrophic rhinitis are easily recognizable. The first sign often is the smell of the patient. In some cases, this can be severe. Paradoxically, this likely will cause distress to everyone except the patient, due to the prevalent finding of anosmia (absence of the sense of smell (as by damage to olfactory nasal tissue or the olfactory nerve or by obstruction of the nasal passages). Patients may relate that others have informed them of the smell. Some patients have also been noted to have clinical depression at presentation due to the social implications of the disease. Another prominent finding is nasal crusting. The crusts are often extensive, filling the entire nasal cavity, and may be present even if the patient reports recent sinus irrigations. Removal of these crusts may induce bleeding. Once the crusts have been removed, several other features may be noted. The mucosa is generally atrophic, with elements of squamous metaplasia present. The volume of the nasal cavity may appear large, either due to absence of turbinate tissue, or lateralization of the lateral nasal walls. Purulent discharge and septal perforations are not uncommon.
Veterinarians can diagnose bacterialrhinitis, atrophic rhinitis, and turbinate atrophy in liveanimals by swabbing the turbinate bonesthrough the snout and producing abacterial culture. Testing several animals ina group provides better results than testinga single animal. Visual inspection is anothermethod of live-animal diagnosis. Purchasedbreeding stock should be isolated beforethey are introduced into the herd so thatobviously affected animals may be culled.Even so, the producer should be aware thateven normal-appearing penmates couldbring in atrophic rhinitis. Purchased feeder and showpigs are also visually appraised for atrophicrhinitis. Because live-animal diagnosis of atrophic rhinitis is indefinite, decisions on whether ornot to allow slightly affected atrophic rhinitis animals toenter a herd should be based more onperformance and health in the seller's herdand knowledge of atrophic rhinitis prevalence and performancein the buyer's herd.
Elimination or prevention of all turbinate atrophy and/or atrophic in a commercial herd is neither cost-effective nor realistic. A good health program, however, can greatly reduce the effect of this disease. Antibacterials in the feed or water, injections of antibiotics, vaccination, and environment modification have been used separately or together to control the clinical signs of atrophic rhinitis. An obvious decrease in clinical signs, such as sneezing, after the use of antibacterial therapy in young pigs may strongly suggest atrophic rhinitis as the diagnosis.
Vaccination may be indicated to control atrophic rhinitis in some herds. Vaccines containing killed B. bronchioseptica, P. multocida type D and type A, plus toxoids to P. multocida type D toxin or P. multocida types D and A toxins may be used. Vaccines containing killed bacteria and toxoids are called bacterin/toxoids. Excellent combination bacterin/toxoids that are now available include Score™ by Oxford Labs (available through a veterinarian) and NOBLVAC-DART® by NOBL Laboratories. Vaccinate sows prefarrowing and pigs preweaning, according to label instructions. Vaccination of feeder pigs may be too late to be effective. Live B. bronchi vaccines is “reversion to virulence”—meaning that they may change back to a disease causing state. Before using an intranasal atrophic rhinitis vaccine, ask the company to provide research data indicating that reversion to virulence is unlikely. Combination vaccines such as bacterin/toxoids may furnish superior protection in severely affected herds. Since each herd situation may vary considerably, consult a veterinarian for advice on vaccine use.
With uncorrected environmental problems, the effectiveness of atrophic rhinitis vaccines is usually poor. In many cases, correcting the environment alone may give as good a response as vaccination with environment correction. For this reason, vaccination may not be cost-effective. But when vaccination gives a good response, a producer is not locked into continual vaccine use, because the breeding herd develops a natural immunity and, as a result, the number of organisms spreading from sow to pig decreases over time. When young pigs are exposed to fewer organisms, the severity of atrophic rhinitis in the herd decreases.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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