[1] IPN, CINVESTAV, Dept Genet & Mol Biol, San Pedro Zacatenco, Mexico
[2] IPN, Escuela Nacl Med & Homeopatia, Secc Estudios Postrado & Invest, Mexico City 07738, DF, Mexico
[3] Univ Autonoma Benito Juarez Oaxaca, Escuela Med Vet & Zootecn, Oaxaca, Mexico
[4] Lab Estatal Salud Publ Oaxaca, Serv Salud Oaxaca, Oaxaca, Mexico
[5] Colorado State Univ, Dept Microbiol Immunol & Pathol, Ft Collins, CO 80523 USA