Slobbering sheep: Bibersteinia trehalosi septicemia in lambs

Jan Shapiro

Animal Health Laboratory, University of Guelph, Kemptville, ON.

AHL Newsletter 2019;23(3):6-7.

In May 2019, three 4-mo-old weaned meat lambs were submitted for postmortem to the Animal Health Laboratory, Kemptville. Of ~100 at risk, 13 had died within 2 wk. Lambs had acute onset of drooling while continuing to try to eat and drink, but over a 24-36 h period became recumbent and died. Neither lameness nor stiffness was observed. Lambs were kept in a multi-age group pen, with no additions to the flock within 6 mo. Only lambs had clinical signs.

Gross postmortem examination revealed multifocal erosion and ulceration of the digestive tract of all 3 lambs, specifically, erosions on the dorsum of the tongue and hard palate of lamb 1, and a jejunal ulcer in lamb 2. Mucosal ulcers covered by plaques of fibrin were in the proximal 1/3 of the esophagus in lambs 1 and 3 (Fig. 1). All 3 lambs had numerous petechiae throughout the lungs, and diffuse hyperplasia of mesenteric, bronchial, and retropharyngeal lymph nodes. There were no gross lesions of the lips, muzzle, dental pad, or hooves, and vesicles were not observed.

Figure 1. Mucosal ulcers covered by plaques of fibrin in the proximal 1/3 of the esophagus (arrows).

Histologically, mucosal erosions and ulcers were covered with fibrin, enmeshed neutrophils, caseous debris, and large numbers of intralesional bacteria. Lamina propria was congested and some blood vessels had thrombi. In lung, lymph nodes, liver, spleen, and brain, bacterial colonies and fibrin thrombi were seen in blood vessels, and bacterial colonies were in parenchyma, sometimes accompanied by caseous necrosis. The diagnosis of acute bacterial septicemia was supported by isolation of Bibersteinia trehalosi from lung, liver, and spleen.

Bibersteinia trehalosi is a sporadic cause of septicemia in sheep, usually occurring in weaned lambs. B. trehalosi normally resides in the tonsils and nasopharynx of apparently healthy animals, but can progress from the tonsils to the lungs and bloodstream to cause systemic disease under exposure to various stresses, such as inclement weather, change of pasture or feed, overcrowding, poor ventilation, handling, and transport. Clinical signs may include fever, anorexia, lethargy, or sudden death with no signs. Common postmortem lesions are petechial and ecchymotic hemorrhages in subcutis, intermuscular fascia, pleura, lungs, epicardium, and mesentery, and swollen lymph nodes. Pneumonia is also frequently seen, and in many cases B. trehalosi is isolated in mixed culture with Mannheimia haemolytica, Pasteurella multocida, or Trueperella pyogenes.

Erosion and ulceration of the oral cavity, tongue and esophagus are not consistent lesions of Bibersteinia trehalosi septicemia, but when they occur, some owners report drooling as the prominent clinical sign. Observation of these lesions prompted consultation with CFIA regarding reportable disease differential diagnoses such as foot-and-mouth disease, bluetongue, peste des petits ruminants, and vesicular stomatitis. More common etiologies include parapoxvirus infection (orf), oral trauma, and bacterial infections.

Ovine herpesvirus type 2 (OHV-2) was also detected in lamb tissues by PCR. OHV-2 is believed to be endemic, and usually asymptomatic, in Ontario sheep flocks. However, experimentally, it may cause MCF-like mucosal disease in sheep. The possibility that OHV-2 could cause similar disease under field conditions, and the significance of OHV-2 in this case is unknown. AHL

References

Caswell JL, Williams KJ. Respiratory system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer’s Pathology of Domestic Animals, 6^th ed. Elsevier, 2016, vol 2:562-563.

Constable PD, et al. Systemic and multi-organ diseases. In: Veterinary Medicine, 11^th ed, vol 2. Elsevier, 2017:2042-2043.