Canine distemper in Siberian tiger cubs from Zagreb ZOO: case report

Canine distemper is a contagious, potentially lethal disease of mainly domestic and wild canids, but also of many other mammalian species including large felids. In February 2004, two Siberian tiger (Panthera tigris altaica) cubs at the age of six months died at the Zagreb ZOO. The animals were presented for necropsy with two days history of severe digestive disorders, characterized mainly by haemathemesis. Dissections revealed catarrhal to pseudomembranous gastroenteritis (depending on the animal) accompanied with haemorrhagic oedema of the lungs. Necrotic tonsillitis and disseminated depletion of the lymphocytes were the most prominent histological findings in both examined animals, while intranuclear and intracytoplasmatic inclusion bodies were found in the samples of the tongues and intestines. Representative portions of the livers, intestines, tonsils and lymph nodes were submitted for bacteriological and mycological analysis. The presence of Clostridium spp., Campylobacter coli and Escherichia coli was detected in gut samples, coli-like bacteria were found in samples of liver, tonsils and lymph nodes, while Candida sp. was found in the gut and pharynx samples. Toxicological analysis excluded anticoagulant and organophosphorous intoxication as the cause of death. Immunohistochemical analysis was positive for canine distemper virus. Based on all this, epizootiological, clinical and additional findings, canine distemper was recognized as the cause of the observed condition in these animals. Large felids, digestive disorders, virus, immunohistochemistry Canine distemper (CD) is a worldwide infectious disease of mainly domestic dogs, but also of a broad spectrum of other species including large felids (Deem et al. 2000). The disease is caused by a negative-stranded morbilivirus of the Paramyxoviridae family that is closely related to the measles and phocine distemper virus. Despite the fact that CD is probably one of the best examples of a disease that has proved capable of compromising the conservation of several wild carnivore species (i.e. Williams et al. 1988; RoelkeParker et al. 1996; Barret 1999; Kennedy et al. 2000; van de Bildt et al. 2002), it has been repeatedly found that canine distemper virus (CDV) historically is not pathogenic in lions and tigers. This hypothesis was tested by Myers et al. (1997) who examined 42 cases of large cat mortalities in Switzerland and found evidence that 19 samples were positive (the oldest positive sample originated from 1972), indicating that CDV infections in lions and tigers are older and more widespread than previously thought. In the present report we describe clinical, pathological, histological and immunohistochemical findings in a case of naturally occurring canine distemper in captive Siberian tiger cubs. Case report and findings During February 2004, zoo-keepers reported that 2 out of 3 Siberian tiger (Panthera tigris altaica) cubs at the age of 6 months were exhibiting signs of gastrointestinal disorders. The cubs were immediately separated from their mother and the third cub. Their condition progressively deteriorated, with haemathemesis as the most prominent clinical symptom. The observed clinical condition was preliminary diagnosed as anticoagulant intoxication ACTA VET. BRNO 2011, 80: 047–050; doi:10.2754/avb201180010047 Address for correspondence: MVDr. Dean Konjević, Ph.D, Dipl. ECZM (Wildlife Population Health) University of Zagreb, Veterinary Faculty Heinzelova 55, 10 000 Zagreb, Croatia Phone: +385 1 2390 156 E-mail: [email protected] http://www.vfu.cz/acta-vet/actavet.htm and prescribed therapy included vitamin K1 (Konakion ®, Roche, Switzerland), H2 agonist to prevent gastric ulcers (Peptoran®, Pliva, Croatia) and trimethoprim-sulphadiazine combination (Trimetosul® 48%, Pliva, Croatia) as supportive antibacterial therapy. Despite the therapy, one cub died 2 days after the onset of clinical signs, and the other survived for 2 more days. The third cub that remained with the mother exhibited no signs of disease and both of them received a 5-day full therapy. Necropsies revealed ulcerative pharyngitis and tonsillitis, and catarrhal to pseudomembranous gastroenteritis (depending on the animal) accompanied with haemorrhagic oedema of the lungs. Multifocal necroses were found on the liver and pancreas. Along with microscopic lesions underlying the described gross changes, necrotic tonsillitis and disseminated depletion of lymphocytes were the most prominent findings in both examined animals. Intracytoplasmatic and intranuclear inclusion bodies were recognized in the tongue and intestines (Plate III, Fig. 1). Representative portions of the liver, intestines, tonsils and lymph nodes were submitted for bacteriological and mycological analysis. The presence of Clostridium spp., Campylobacter coli and Escherichia coli was detected in gut samples, coli-like bacteria were found in samples of the liver, tonsils and lymph nodes, while Candida sp. was found in the gut and pharynx samples. Toxicological analysis of the samples of blood and gastric content excluded anticoagulant and organophosphorous intoxication as the cause of death. Two years later, paraffin embedded samples of tiger organs were sent to the University of Bern for immunohistochemical analysis (IHC) with positive labelling obtained for the CDV antigen (Plate III, Fig. 2). In brief, the nucleocapsid (N) protein of CDV was detected using a monoclonal antibody D110 diluted 1:2 in TBS. We used goat-anti-mouse antibody diluted 1:40 in TBS as a secondary antibody. Sections were deparaffinized, rehydrated, peroxidase blocked, demasked and incubated with primary and secondary antibodies and visualized with peroxidase antiperoxidase reaction. Due to the similarities in some clinical and pathological findings between infections caused by canine parvovirus and CDV, an IHC staining for parvovirus was performed with negative results. Based on all this, epizootiological, clinical and additional findings, canine distemper was recognized as the cause of the observed condition in the respective animals.