Investigating Disease in Declining Thick-Billed Parrot Populations in Northern Mexico
1Wild Animal Park, San Diego Zoo, Escondido, CA, USA; 2San Diego Zoo’s Institute for Conservation Research, Escondido, CA, USA; 3Tecnologico de Monterrey, Campus Monterrey, Monterrey, Nuevo Leon, Mexico; 4College of Veterinary Medicine, Cornell University, Ithaca, NY, USA
Read the Spanish translation: Investigación del Papel de las Enfermedades en la Declinación de las Poblaciones de Loros de Pico Grueso (Cotorra serrana) en el Noreste de Mexico
Thick-billed parrots (TBPs) (Rhynchopsitta pachyrhyncha pachyrhyncha), listed in appendix 1 of CITES as endangered, once ranged from the southwestern United States to northern Mexico. Their current range is limited to the pine forests of Mexico’s Sierra Madre Occidental. Current populations are threatened by habitat destruction and degradation. There is no information available regarding the role of disease in population declines. We hypothesize that climate change leading to changes in vector prevalence increases disease threats to wild populations. In 2003, 20% of all deaths of captive TBPs in the United States were due to West Nile virus (WNV) infection. The impact of WNV on human and animal populations in Mexico has been less than in the U.S. possibly due to prior exposure to other flaviviruses. TBPs nest at elevations >2000 m. These high elevation habitats may limit mosquito activity. If mosquito activity is limited, exposure to other flaviviruses that cross-protect against WNV will also be limited. We initiated a TBP health and habitat monitoring program at four nests sites in the Sierra Madres to better define disease concerns in the region. We identified mosquito vectors for WNV, Culex quinquefasciatus and C. tarsalis, at two sites. Serum samples were collected from 24 TBP chicks and were negative for WNV and St. Louis encephalitis virus. Using a mobile molecular laboratory, in-situ field diagnostics were performed on samples collected from a dead chick. The liver and spleen were positive for a non-WNV flavivirus. We were unable to confirm whether this virus contributed to the bird’s death.