Comparative pathology and tissue tropism of two indigenous strains (H-90 AND R-98) of equine herpes virus 1 in pregnant balb/C mice towards occurrence of respiratory affections and abortions subsequent to intranasal inoculation

The present studies were carried out to study the comparative pathology and tissue tropism of indigenous strains (H-90 and R-98) of EHV-1 (Equine Herpes Virus-1) for affections of respiratory and reproductive system. Twenty, 8–10 weeks old pregnant BALB/c mice at 13–14 days of gestation were divided into three groups namely A, B and C and inoculated intranasally with H-90 (10^7.4 TCID₅₀/mice), R-98 strain (10^7.0 TCID₅₀/mice) and RK-13 cell lysate, respectively. Mice of groups A and B showed severe symptoms and lesions of respiratory system characterized by dyspnoea, ruffled fur and crouching in corners. However, the mice of group B in addition showed the lesions of vaginal discharge and abortion. Microscopically, lesions in lungs were characterized by presence of intranuclear inclusion bodies, infiltration of neutrophils and lymphocytes, ballooning, rounding and hyperplasia of epithelial cells of bronchi in early stages followed by necrosis of parenchymal tissue. Lesions in the placenta varied in two strains markedly. Strain H-90 could produce only congestion of sinusoids at 3 dpi (day post-inoculation) in mice and patchy necrosis of chorionic plate in one mouse on 5 dpi. R-98 strain produced severe congestion of sinusoids, chorionic plate necrosis and necrosis in trophoblastic tissue.