Tonate Virus and Fetal Abnormalities, French Guiana, 2019

International audienceV enezuelan equine encephalomyelitis (VEE) complex viruses consist of antigenically related arboviruses widely distributed throughout the Americas (1). Only subtype I varieties AB and C cause severe equine epizootics and human outbreaks marked by the occurrence of encephalitis and fetal damage (2). The other subtypes are endemic in small areas of South America (3). In 1973, subtype III-B, the Tonate virus (TONV), was isolated in birds from French Guiana (4). It has since been found in neighboring countries and in South Dakota and Colorado in the United States (5,6). The wild cycle of TONV is still poorly understood. Transmission by Culicidae insects has been observed during the rainy season (4). Birds and bats are the only identifi ed vertebrate hosts (7). In humans in French Guiana, TONV seroprevalence suggests endemic transmission, particularly along the coast of the Bas Maroni region (8). However, clinical descriptions remain scarce, and no adverse pregnancy outcomes or vertical transmission have been reported (9,10). We report a case of vertical transmission of TONV from a pregnant woman to her fetus and describe ultrasonographic and fetopathological fi ndings. The Study During the 2019 rainy season, a 33-year-old woman living in the Bas Maroni region of French Guiana was referred to the prenatal diagnosis unit at West French Guiana Hospital Center (Saint-Laurent-du-Maroni, French Guiana) for fetal anomalies. This healthy G8P7 woman had no history of genetic disorders or birth defects from previous pregnancies. She was asymptomatic during the fi rst trimester of pregnancy and tested negative for syphilis, toxoplasmosis, rubella, cytomegalovirus, chikungunya, and Zika. An ultrasound screening performed at 20 weeks of gestation showed a hydropic fetus with microcephaly. The atrophic cerebral mantle exhibited calcifi cations and moderate ventriculomegaly. The corpus callosum, the cerebellum, and the brain stem were dysplastic. The fetus manifested limb malformations and an absence of swallowing at the time of the serially performed sonograms (Appendix Figure, https:// wwwnc.cdc.gov/EID/article/28/2/21-0884-App1. pdf). Therefore, we performed amniocentesis for etiological investigation. Because of the poor prognosis, the mother elected to terminate the pregnancy. After approval by the multidisciplinary center for prenatal diagnosis, the pregnancy was terminated without complication. The patient gave written informed consent for the publication of her case. Karyotype and array comparative genomic hybridization were normal. Results of screening for metabolic diseases were negative. All PCR and reverse transcription PCR (RT-PCR) for toxoplasmosis, rubella, cytomegalovirus, herpes simplex virus, and common arboviruses from the Amazon were negative. However, we reproducibly detected the presence of a VEE complex virus in the amniotic fl uid with a real-time RT-PCR test yielding cycle threshold values of 30. Furthermore, although maternal serum samples collected 2 months before pregnancy were negative for TONV IgM, the test was positive at the time of pregnancy termination