Quantification of the herpesvirus content in various tissues and organs, and associated post mortem lesions of psittacine birds which died during an epornithic of pacheco's parrot disease (PPD)

Abstract

This paper reports on the viral content of up to 52 tissue and organ samples of 18 individual large psittacines which died during an epornithic of Pacheco's parrot disease (PPD) caused by psittacid herpesvirus 1 (PsHV1). Associated clinical signs and pathological lesions are described. The large spectrum of samples found to be positive for PsHVl suggests that birds succumb to PPD during viraemia. Tissues and organs from which the virus could be isolated included the integument and associated structures, the muscular, respiratory and circulatory system, bone marrow, the nervous system, thyroid and adrenal glands, spleen and liver, the urogenital tract and the gastro‐intestinal tract. Nevertheless, individual and organ (but not species)‐specific variation does occur. Virus isolation appears to be most promising from the respiratory, vascular and nervous system and the liver. Highest titres were obtained from heart blood and liver (up to 7.6 log10/g tissue), airsac, Nervus vagus and pulp and quill of pin feathers. Pin feathers may therefore be suitable for in‐vivo diagnosis. In contrast, HV could not be isolated from any of the feather vanes examined. For the most part, post mortem lesions do not reflect the organ pattern found to be most permissive for virus replication as judged by the success of virus isolation and virus titres. A closer quantitative correlation is indicated for the lungs, spleen and liver, only. Corresponding findings as to frequency of gross pathological lesions and virus quantification appear to be restricted to the liver. In accordance with clinical observations and experimental findings, tissue virus content indicates that horizontal spread of herpesviruses is mediated by cloacal contents or secretions from the respiratory system.