Margaret Stalker, Josepha DeLay, Amy Gaw
Animal Health Laboratory, University of Guelph, Guelph, ON (Stalker, DeLay), Temiskaming Veterinary Service (Gaw)
AHL Newsletter 2022;26(4):10.
An adult ewe experienced an exacerbation of dyspnea shortly after lambing. The producer had previously noted episodes of an “everted nostril” over the past few years. On physical exam, pink tissue protruded from the left nostril, with obstruction of air flow. The ewe was subsequently euthanized and the head was submitted to the AHL for further diagnostic workup.
On external examination, the left side of the nose appeared swollen, with an approximately 2 cm diameter pale smooth-surfaced pink mass protruding from the nostril. Sagittal sectioning of the head revealed a large 5 cm x 15 cm multilobulated tan-pink smooth-surfaced tissue filling the entire left nasal cavity, encompassing the turbinates and extending to the ethmoid turbinate region and into the nasopharynx (Fig. 1). The provisional diagnosis was enzootic nasal tumor.
Histologic sections of the mass revealed well-differentiated nasal respiratory epithelium overlying a fibrous stroma populated by scattered dilated glandular structures surrounded by large numbers of plasma cells, with fewer lymphocytes and neutrophils (Fig. 2). The glandular structures were lined by well-differentiated pseudostratified columnar epithelium with mucin secretion. Closer examination of the respiratory epithelium revealed myriad faintly visible intracytoplasmic bacilli (Fig. 3). Tissue Gram stains confirmed these as gram-negative bacteria.
A tentative diagnosis of chronic proliferative rhinitis was made, and a sample of frozen nasal epithelium was submitted for bacterial culture. Routine culture isolated 2+ Salmonella sp. from the nasal epithelium. The isolate was subsequently serotyped as Salmonella enterica subspecies diarizonae serotype 61:k:1,5,7 (SED).
Chronic proliferative rhinitis associated with intracytoplasmic Salmonella infection of nasal epithelium is an unusual disorder of sheep. The condition was first reported in the USA in 1992. Since then, cases have also been reported in Spain and Switzerland, again associated with SED infection. SED is considered a host-adapted bacterium of sheep, and 66.4% of US sheep flocks are culture-positive asymptomatic carriers of this organism. The bacterium is likely maintained in flocks through fecal-oral transmission, although colonization of the nasal cavity may indicate nasal shedding is also possible, as in this case. An opportunistic pathogen with sporadic reports of enteritis in lambs and abortion, SED is also potentially zoonotic, although human risk is more typically associated with exposure to infected reptiles that also carry the pathogen. AHL
Figure 1. Pale pink edematous tissue filling and occluding the left nasal cavity of a ewe.
Figure 2: Chronic rhinitis with marked plasmacytic inflammation (H&E, 10X).
Figure 3: Numerous intracytoplasmic bacilli within nasal respiratory epithelium (H&E, 60X).
References
1. Meehan IT, et al. Chronic proliferative rhinitis associated with Salmonella arizonae in sheep. Vet Pathol 1992;29:556-559.
2. Lacasta D, et al. Chronic proliferative rhinitis associated with Salmonella enterica subspecies diarizonae serovar 61:k:1,5,(7) in sheep in Spain. J Comp Path 2012;147:406-409.
3. Pritchard J. Salmonella arizonae in sheep. Can Vet J 1990;31:42.
4. Salmonella in US Sheep Operations, 2011. USDA-APHIS, Veterinary Services Info Sheet. June 2013.