Zika virus (ZIKV) has recently surged in human populations, causing an increase in congenital and Guillain-Barré syndromes. While sexual transmission and presence of ZIKV in urine, semen, vaginal secretions, and saliva have been established, the origin of persistent virus shedding into biological secretions is not clear. Using a primary adult murine neuronal culture model, we have determined that ZIKV persistently and productively infects sensory neurons of the trigeminal and dorsal root ganglia, which innervate glands and mucosa of the face and the genitourinary tract, respectively, without apparent injury. Autonomic neurons that innervate these regions are not permissive for infection. However, productive ZIKV infection of satellite glial cells that surround and support sensory and autonomic neurons in peripheral ganglia results in their destruction. Persistent infection of sensory neurons, without affecting their viability, provides a potential reservoir for viral shedding in biological secretions for extended periods of time after infection. Furthermore, viral destruction of satellite glial cells may contribute to the development of Guillain-Barré Syndrome via an alternative mechanism to the established autoimmune response.

Saint Francis Service Dogs (SFSD) trains dogs to aid people with multiple sclerosis, brain injury, and many other conditions. Organizations like SFSD must carefully consider when to neuter dogs to give them the best chance at successfully completing lengthy and expensive training. The objective of this retrospective cohort study was to assess differences in the incidence of health or behavior problems leading to dismissal between dogs neutered at different ages. Data on 245 dogs—including birth date, sex, neuter date, dismissal or successful completion of training, and (where applicable) reason for dismissal—were collected from SFSD records. Age-at-neuter was grouped (<7 months; 7–11 months; > 11 months) and compared for dogs who successfully completed training and dogs who were dismissed. Dogs neutered from 7 to 11 months of age were dismissed at a significantly lower overall rate than dogs neutered at an older or younger age. There were no differences between males and females. Labrador and golden retrievers were less likely to be dismissed than other breeds. This pattern was the same for dismissals for behavioral reasons. Dogs neutered at <7 months had more than twice the risk for health-related dismissals as dogs neutered at any older age and this pattern held for orthopedic dismissals. Labradors were at higher risk for orthopedic-related dismissal than golden retrievers and all other breeds. This study suggests that there is a relationship between dogs' age at neuter and the incidence of health and behavioral problems that can lead to dismissal from service dog training.