USA: Sexual transmission of Zika virus typically only occurs in acutely infected mice.

Zika Virus Associated pathology and Antigen presence in the testicle in the Absence of sexual transmission During subacute to Chronic Infection in a Mouse Model

Chad s. Clancy, Arnaud J. Van Wettere, John D. Morrey & Justin G. Julander|Utah Veterinary Diagnostic Laboratory, School of Veterinary Medicine, Department of Animal, Dairy, and Veterinary Sciences, Utah State University, Logan, Utah, 84341, United States of America, Institute for Antiviral Research, Department of Animal, Dairy, and Veterinary Sciences, Utah State University, Logan, Utah, 84322-5600, United States of America|2019|Scientific Reports|9:8325 https://doi.org/10.1038/s41598-019-44582-9

Zika virus (ZIKV) is an arboviral infection that can be sexually transmitted in the ejaculate of infected men. There has been reported persistence of viral RNA from 6 months to nearly one year, with no epidemiological evidence to support sexual transmission during the chronic phase of reproductive tract infection in humans to date. In this study, an animal model using ZIKV-infected male mice was developed to evaluate the potential for sexual transmission from infected males in chronic stages of disease. Quantitative RT-qPCR was performed on Mic qPCR Cycler using whole blood samples to determine the gene expression of ZIKV RNA in both the intravaginal and subcutaneous inoculated groups of female and male mice. The relative number of ZIKV RNA copies was determined by extrapolation from the standard curve and normalised to GAPDH RNA for each sample. It was demonstrated that ZIKV antigens were detectable in epididymal cells during subacute but not chronic infection. ZIKV antigens were not detected in prostate and seminal vesicles during the course of the disease. It was also shown that viral RNA was not detected in females from any intravaginal experimental group and only detected in 20% of subcutaneously inoculated animals, derived from 1 experimentally infected male, 35 days post infection. This indicates that rare transmission of the infectious virus can occur in chronically infected male mice.