Encephalomyelitis and Pneumonitis in Hamsters Infected with Newcastle Disease Virus by Different Routes.

Abstract

Intracerebral injection of Newcastle disease virus (NDV) has been shown to cause encephalomyelitis in hamsters ( 1 ) and monkeys (2). Similarly, mice (3.4) and cats ( 5 . 6) develop encephalomyelitis. pneumoni tis or both following intracerebral or intranasal administration of this virus. Among mammals, there have been no reports of successful infection with this virus administered by routes other than these. The purpose of this communication is to describe the pattern of disease and pathological findings of encephalomyelitis and pneumonitis in hamsters caused by h'DV injected by peripheral routes.Materials and ~rzethods. The virulent chicken-adapted CG strain of XI)V was obtained from F. B. Bang. The pool of infected allantoic fluid harvested 48 hours after inoculation of 11-day-old embryonated eggs and used in these experiments titered 1W2 plaque forming units (PFU) per ml in chick embryo fibroblasts.The virus, diluted in phosphate buffered saline, was administered by either the intranasal (0.05 ml) : intracerebral (0.05 ml), intramuscular (0.1 5 ml) , subcutaneous (0.10 ml) or intraperitoneal (0.5 ml) routes to 2 1 -day-old hamsters obtained from Lakeview Farm, Newfield, N. J. Virus was administered intranasally by dropping diluted inocula into the external nares of anesthetized animals and hyperextending the head to allow adequate contact of the nasopharyngeal mucosa with infective material. Intracere-bra1 injections were made through the mid point of the skull. Subcutaneous. intraperitoneal, and intramuscular inoculations were made into the interscapular region, through the lower right abdominal wall and into the right thigh respectively. In each experi-*Aided by grants from USPHS and the Whitehall Foundation.t Kenny Foundation Scholar. ment, sterile diluent fluid was administered to a control group of hamsters by the same route as the virus. The hamsters were placed in individual cages and examined daily during a period of 3 weeks for signs of illness or death. Partial autopsies were performed on nearly all animals and complete autopsies were made on the 1 79 animals examined histologically. Tissues were fixed in 10% formol-saline. Brains were embedded in celloidin and sectioned coronally or sagittally at 20 p and stained with cresyl violet or hematoxylin and eosin. Other organs were embedded in parafin, sectioned a t 8-10 p, and stained with hematoxylin and eosin.In some experiments, brains and lungs were removed aseptically, ground in Ten Broeck grinders, and diluted to 10% (W/V) with buffered saline (0.01 M phosphate, pH 7.3). Virus isolations from tissue homogenates were made by subinoculations of 180 mm X 16 mm tube cultures of chick embryo fibroblast or 10-day-old embryonated eggs. The chick fibroblast cultures were inoculated 2 days after seeding, and maintained with mixture 199 and 10% calf serum for a week. Tissue culture fluids collected from cultures showing cytopathic effect were also tested for their capacity to agglutinate chick red blood cells. Ten-day-old embryonated eggs were injected into ...