VECTOR-BORNE AND ZOONOTIC DISEASES Volume 3, Number 1, 2003 © Mary Ann Liebert, Inc. Serologic Survey of Domestic Animals for Zoonotic Arbovirus Infections in the Lacandón Forest Region of Chiapas, Mexico ARMANDO ULLOA, 1,3 STANLEY A. LANGEVIN, 2 J.D. MENDEZ-SANCHEZ, 1 JUAN I. ARREDONDO-JIMENEZ, 1 JANAE L. RAETZ, 2 ANN M. POWERS, 2 C. VILLARREAL-TREVIÑO, 1 DUANE J. GUBLER, 2 and NICHOLAS KOMAR 2 ABSTRACT A serologic survey in domestic animals (birds and mammals) was conducted in four communities located in the Lacandón Forest region of northeastern Chiapas, Mexico, during June 29 to July 1, 2001, with the objective to iden- tify zoonotic arboviruses circulating in this area. We collected 202 serum samples from healthy domestic chick- ens, geese, ducks, turkeys, horses and cattle. The samples were tested by plaque-reduction neutralization test for antibodies to selected mosquito-borne flaviviruses (family Flaviviridae), including St. Louis encephalitis (SLE), Rocio (ROC), Ilheus (ILH), Bussuquara (BSQ), and West Nile (WN) viruses, and selected alphaviruses (family Togaviridae), including Western equine encephalitis (WEE), Eastern equine encephalomyelitis (EEE), and Venezue- lan equine encephalitis (VEE) viruses. Neutralizing antibodies to SLE virus were detected in two (8%) of 26 turkeys, 15 (23%) of 66 cattle, and three (60%) of five horses. Antibodies to VEE virus were detected in 29 (45%) of 65 cat- tle. Because some of these animals were as young as 2 months old, we demonstrated recent activity of these two viruses. Sub-typing of the VEE antibody responses indicated that the etiologic agents of these infections belonged to the IE variety of VEE, which has been reported from other regions of Chiapas. WN virus-neutralizing antibodies were detected in a single cattle specimen (PRNT 90 5 1:80) that also circulated SLE virus-neutralizing antibodies (PRNT 90 5 1:20), suggesting that WN virus may have been introduced into the region. We also detected weak neu- tralizing activity to BSQ virus in four cattle and a chicken specimen, suggesting the presence of this or a closely related virus in Mexico. There was no evidence for transmission of the other viruses (ROC, ILH, EEE, WEE) in the study area. Key Words: Arbovirus—Lacandón Forest—Domestic animals. Vector-Borne Zoonotic Dis. 3, 3–9, 2003. 3 INTRODUCTION T HE TROPICAL FOREST REGION of southern Mex- ico hosts millions of neotropical migrant birds belonging to more than 100 species. These birds may introduce northern viruses into the tropical ecosystems as they travel south during fall migration, and carry viruses northward during spring migration. With the intense ac- tivity of West Nile virus reported in the east- ern United States since 1999 (Marfin et al. 2001; O’Leary et al. 2002), the status of this mosquito- borne zoonotic flavivirus in the American trop- ics is of special interest. The introduction of West Nile virus into tropical America may have significant health impacts on humans and ani- mals throughout the tropics, and could become established in transmission cycles that would annually infect northward migrating birds. Tropical forests are known for their rich 1 Centro de Investigación de Paludismo, Tapachula, Chiapas, Mexico. 2 Centers for Disease Control and Prevention, Division of Vector-Borne Infectious Diseases, Fort Collins, Colorado. 3 Present address: Universidad de Ciencias y Artes de Chiapas, Tuxtla Gutierrez, Chiapas, Mexico.