Atrophic Rhinitis

Atrophic rhinitis is a contagious respiratory disease of pigs that is highly prevalent throughout the world where modern pig husbandry is practiced. Several agents were suspected to be etiological agents in the early studies. These included bacteria (Pseudomonas, Actinomyces, Sphaerophorus, Corynebacterium, or Mycoplasma), a virus (cytomegalovirus), and trichomonads. However, only certain defined strains of Bordetella bronchiseptica and Pasteurella multocida proved to be able to constantly reproduce marked turbinate atrophy, the most characteristic lesion of atrophic rhinitis. A productive P. multocida infection needs predisposing factors among which B. bronchiseptica preinfection is the most commonly recognized one. This interaction between the two pathogens classifies atrophic rhinitis as a member of the family of polymicrobial infections, and the disease are reviewed with special attention to this aspect. The dominant pathological lesion of atrophic rhinitis is an atrophy of the nasal turbinate bones as assessed by transverse section of the nasal cavity at the level of the first/second upper premolar teeth where the dorsal and ventral conchae are maximally developed in the normal pig. Atrophic rhinitis is thought to reduce growth rates, which makes it an economically important disease for pig producers. Vaccination is widely used to try to reduce the prevalence of atrophic rhinitis in herds affected by the disease. The specific synergistic interactions between B. bronchiseptica and P. multocida support the notion that it is a genuine polymicrobial disease, which in addition may serve as a useful model system for more complex mixed infections.