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Newcastle disease virus (NDV), a major pathogen of poultry worldwide, causes significant economic losses in the poultry industry. To characterize the ability of recently isolated virulent strains of NDV genotypes VI and VII to cause disease in quails, and to evaluate the efficacy of two NDV vaccines against such strains, Japanese quails were experimentally inoculated with either NDV genotype VI (Pigeon F-VI strain) or VII 1.1 (GHB-328 strain) with or without vaccination with inactivated NDV vaccine of genotype II (La Sota strain) or VII (KBNP strain). Mild to severe neurological signs developed in quails inoculated with the Pigeon F-VI strain from 3 to 14 days post infection (PI) and from 4 to 10 days PI in birds infected with the GHB-328 strain. The mortality rates were 46% and 33% for birds inoculated with NDV VI and NDV VII 1.1, respectively. The severity of histopathological changes depended on the viral isolates used. Vaccination with the La Sota or KBNP vaccine strain successfully protected quails against NDV-induced mortality and decreased the severity of clinical signs, pathological changes and cloacal viral shedding. This study showed that these virulent NDV isolates had mild to moderate pathogenicity in quails and that both vaccines protected against challenge with both virus strains. NDV vaccine genotype VII improved the level of protection against challenge with the VII 1.1 genotype compared with the classic vaccine, but failed to protect quails against challenge with the VI genotype.

The infectivity of equine herpesvirus (EHV)-9 has been studied in different animal models including immunocompromised animals. The current study focused on the infectivity of EHV-9 in different mouse strains (C3H, C57BL, DBA, BALB/c-nu/nu, BALB/c and ICR) by intranasal inoculation of 2 × 106 plaque forming units (PFU). Various organs, including head and lungs, were collected 7 days post infection (dpi) to investigate microscopical lesions and the distribution of EHV-9 antigen. Immunopositivity of tissue sections was scored using ImageJ software. Open reading frame (ORF) 30 expression in lung tissues was quantified using quantitative reverse transcriptase polymerase chain reaction. Pathological examination revealed different degrees of rhinitis in the different mouse strains. Severe rhinitis was detected in C3H and BALB/c-nu/nu strains, moderate rhinitis was observed in C57BL and DBA strains and no lesions were detected in BALB/c mice. Immunopositivity for EHV-9 antigens was detected in the olfactory epithelium of C3H and BALB/c-nu/nu strains. Compared with C57BL, DBA, BALB/c-nu/nu, ICR and BALB/c strains, the C3H strain showed greater expression of EHV-9 antigens in the brain. The proportion of areas with high positive to positive immunoreactivity for EHV-9 were 7.57, 3.42, 3.12, 2.51, 1.79 and 0.03% for C3H, C57BL, DBA, BALB/c-nu/nu, ICR and BALB/c strains, respectively. The proportions of areas with low positive to negative immunoreactivity were 92.42, 96.70, 96.87, 97.48, 98.16 and 99.96%, respectively. The highest relative expression levels for EHV-9 ORF30 in the lungs were in C3H mice. No significant differences in the expression of ORF30 were observed in other strains. In conclusion, of the strains examined, C3H, C57BL, DBA, BALB/c-nu/nu and ICR were the most susceptible to EHV-9 infection, and the BALB/c strain was less susceptible.

Pregnant rats were infected experimentally with equine herpesvirus (EHV)-9, a new neurotropic equine herpesvirus serologically similar to EHV-1, during the first and third trimesters. The inoculated dams had mild to severe neurological signs and gave birth to dead fetuses or undersized pups. Rats inoculated during the first and last trimesters had varying degrees of encephalitis as well as abnormalities of the placentas in the form of marked dilation of maternal blood sinusoids and varying degrees of atrophy and necrosis of the trophoblast cells of the labyrinth, the spongiotrophoblasts and the giant cell layer. Virus antigen was detected by immunohistochemistry in the brain and the trophoblast cells of labyrinth, the spongiotrophoblasts and giant cell layer of the placenta in rats inoculated during the first trimester. Virus antigen was detected in fetuses from rats inoculated in the first and last trimesters. Virus DNA was amplified by polymerase chain reaction from the placenta and fetuses of inoculated rats. EHV-9 may induce fetal death and abortion in pregnant dams, possibly caused by direct EHV-9 infection of the placenta and/or fetus as well as the secondary effect of vascular injury.

Summary The pathogenesis and kinetics of oral infection by equine herpesvirus (EHV)-9 were studied in mice and hamsters. After oral inoculation of 105 plaque-forming units (PFU) of virus, 1-week-old suckling hamsters showed varying severity of neurological disease from 72 hours post inoculation (hpi) and all of these animals had died by 96 hpi. Four-week-old ICR mice inoculated orally with 4 × 104 PFU of virus showed no clinical signs, but they developed erosive and ulcerative gastritis from 36 hpi. Varying degrees of encephalitis were seen in infected mice and hamsters, and the hamsters also developed myelitis by 96 hpi. Immunohistochemistry performed on whole body sections of suckling hamsters revealed the kinetics of spread of the virus to the central nervous system. EHV-9 antigen was detected initially in macrophages of the oral and lingual submucosa. At 36 hpi virus antigen was detected in the nerve fibres and pseudounipolar neurons of the trigeminal ganglion and at 96 hpi antigen was present in the myenteric plexuses of the intestine. Virus antigen was also detected in the liver, lungs and heart of affected animals. EHV-9 DNA was detected by polymerase chain reaction in the brain, blood and spinal cord of suckling hamsters at 36, 48 and 96 hpi. These findings show that EHV-9 may spread via the trigeminal nerve when mice and hamsters are inoculated orally with virus.

The kinetics of infection and pathogenicity of equine herpesvirus-9 (EHV-9) was studied in a hamster model. Five-week-old Syrian hamsters and 5-day-old suckling hamsters were inoculated intraperitoneally with 10(5) and 4×10(4) plaque-forming units of EHV-9, respectively. EHV-9 antigens were detected by immunocytochemistry in the peritoneal macrophages, which may be the primary site of virus attachment and propagation at 6h post inoculation (hpi). At 12 hpi, viral antigen was observed in the abdominal nerves and ganglia (mainly the coeliac ganglia). Virus antigen was detected in the dorsal root (spinal) ganglia, in parts of the spinal cord (particularly the mid-lumbar area) and in the myenteric plexuses at 36, 48 and 72 hpi, respectively. At 96 hpi, virus antigen was detected in the most caudal part of the brain. Polymerase chain reaction conducted on samples of the blood, spinal cord and brain revealed EHV-9 DNA in the spinal cord at 36 hpi and in the blood at 48 hpi and for 4 days after this initial detection. It is suggested that after initial propagation in the abdominal macrophages, EHV-9 infected the abdominal ganglia or myenteric plexuses and then travelled to the brain via the peripheral nerves and spinal cord. Examination of other organs also revealed the presence of EHV-9, suggesting that the virus might infect tissues other than those of the nervous system.

The pathogenicity of equine herpesvirus (EHV)-9, a new neurotropic equine herpesvirus isolated from gazelles, was assessed in pregnant rodents (mice and hamsters) following intranasal inoculation. The pregnant female mice and hamsters were inoculated with EHV-9 in the early or late trimesters. The inoculated animals exhibited mild to severe neurological signs and gave birth to dead or undersized fetuses. All three mice and four hamsters inoculated in the first trimester had varying degrees of placental abnormality, characterized by markedly dilated maternal blood sinusoids, atrophy of the trophoblast cells and necrosis of the middle layer of the trophoblast. There was also endometrial blood vessel congestion and necrosis and disorganization of the fetal capillaries in the mice and hamsters inoculated in the last trimester. EHV-9 antigen was detected in the brain of dams and the lungs of the fetuses and in the middle of the trophoblast layer of the placenta in hamsters inoculated in the first trimester. The placental lesions were milder in mice than in the hamsters. The mice and hamsters inoculated in the last trimester had more prominent lesions than the animals inoculated in the first trimester. These results suggest that EHV-9 can cause the death of the fetus or abortion and that these events may be secondary to placental vascular compromise.