Levels of herpes simplex virus 1 (HSV-1) and HSV-2 DNA in dorsal root ganglia (DRG) and spinal cord (SC) were quantified after inoculation of guinea pig genitals and footpads. In genital infection, viral DNA reached SC and DRG simultaneously (at 2 to 3 days after inoculation) but was more abundant in SC than in DRG. After inoculation of footpads, which lack parasympathetic innervation, the viruses spread more efficiently to DRG than to SC. These results show important differences between genital and footpad infections, including independence of spread to DRG and SC, and imply that autonomic neurons may play an important role in the pathogenesis of viral latency after genital inoculation.The related species herpes simplex virus 1 (HSV-1) and HSV-2 exhibit differences in latency and recurrence patterns. While both viruses establish latency in sensory ganglia and reactivate to cause recurrent disease, HSV-1 reactivates more efficiently from trigeminal ganglia to cause cold sores or keratitis and HSV-2 reactivates more efficiently from lumbosacral dorsal root ganglia (DRG) to cause genital herpes (8). HSV-1 and HSV-2 also display different tropisms for nociceptive sensory neurons, with HSV-1 more likely to be detected during latency in murine neurons displaying the surface marker A5 and HSV-2 in those displaying KH10 (9). Both of these findings are associated with HSV-1 or HSV-2 viral species-specific latency-associated transcript (LAT) sequences (9, 18).Although most studies have focused on viral latency in sensory neurons of either the dorsal root or trigeminal ganglia, we recently showed that levels of virus DNA in spinal cord exceeded those in the corresponding DRG, suggesting that other sites of latency may be important (1). After genital infection of guinea pigs, the quantities of latent HSV-1 DNA are greater in the thoracolumbar spinal cord than in the sacral spinal cord, while latent HSV-2 DNA is more abundant in the sacral spinal cord. Mutations in the LAT did not influence this tropism for different spinal cord levels. Because sympathetic neurons have their origin in the thoracolumbar cord and parasympathetic neurons arise in the sacral cord, we hypothesized that these findings may be related to viral infection of autonomic ganglia (2). Both HSV-1 and HSV-2 are able to infect autonomic neurons (3,5,7,10,12,(14)(15)(16)(17). HSV-2 infection of autonomic neurons can give rise to transient bladder paralysis in humans, and latently infected murine parasympathetic neurons express the latency-associated transcript (12). Viral infection of autonomic ganglia is difficult to study directly in animal models of HSV-2 infection because perigenital ganglia are very small, are located in the perigenital fat, and are difficult to identify. In the present study, we used genital (6) and footpad models of HSV infection to further examine these phenomena that are potentially related to differences in autonomic neuronal infections with HSV-1 and HSV-2.To further investigate the spread of virus to the spinal cord, we examined ...