Pathologic and Molecular Virologic Characterization of a Canine Distemper Outbreak in Farmed Civets.

Abstract

In October 2011, a fatal disease outbreak occurred in 3 civet species farmed for their use in the coffee industry in Thailand. The disease quickly killed 20 animals in a mixed population of Asian palm civets (Paradoxurus hermaphroditus; n = 18), a masked palm civet (Paguma larvata; n = 1), and small Indian civet (Viverricula indica; n = 1). Clinical signs consisted of severe lethargy, weakness, vomiting, and diarrhea with associated dehydration, dyspnea, nasal and footpad hyperkeratosis, and seizures. All civets were positive for canine morbillivirus using the commercial canine distemper virus (CDV) antigen test kit. Consistently observed necropsy findings consisted of severe pneumonia and hemorrhagic enteritis. Microscopic examination revealed severe gastroenteritis, bronchointerstitial pneumonia, lymphadenitis, necrotizing dermatitis, nonsuppurative polioencephalitis, and characteristic intranuclear/intracytoplasmic eosinophilic viral inclusions in multiple tissues. Immunohistochemical analysis revealed immunoreactivity of varying intensity, while virus isolation demonstrated typical cytopathic effects. To confirm CDV infection, reverse transcription-polymerase chain reaction against fusion (F), phosphoprotein (P), and hemagglutinin (H) genes showed bands of expected size using conjunctival swabs (9 civets, 1 dog [Canis lupus familiaris] living on the farm). Phylogenetic analyses and restriction fragment length polymorphism results indicated that the civets were infected by the Asia-1 strain of CDV commonly found in dogs in Thailand. The deduced amino acid sequences of the signaling lymphocyte activation molecule binding region of the CDV-H proteins revealed a Y549H mutation in both CDV-infected Asian palm civets (n = 4) and a co-located dog. We report a canine distemper outbreak in a civet colony with lineage classification and a Y549H mutation in noncanid species in Thailand.