West Nile Virus Ecology in a Tropical Ecosystem in Guatemala

Abstract

Abstract. West Nile virus ecology has yet to be rigorously investigated in the Caribbean Basin. We identified a transmission focus in Puerto Barrios, Guatemala, and established systematic monitoring of avian abundance and infection, seroconversions in domestic poultry, and viral infections in mosquitoes. West Nile virus transmission was detected annually between May and October from 2005 to 2008. High temperature and low rainfall enhanced the probability of chicken seroconversions, which occurred in both urban and rural sites. West Nile virus was isolated from Culex quinquefasciatus and to a lesser extent, from Culex mollis/Culex inflictus, but not from the most abundant Culex mosquito, Culex nigripalpus. A calculation that combined avian abundance, seroprevalence, and vertebrate reservoir competence suggested that great-tailed grackle (Quiscalus mexicanus) is the major amplifying host in this ecosystem. West Nile virus transmission reached moderate levels in sentinel chickens during 2007, but less than that observed during outbreaks of human disease attributed to West Nile virus in the United States.

Host Selection of Potential West Nile Virus Vectors in Puerto Barrios, Guatemala, 2007

“…A complete description of the transmission focus is published elsewhere. 2 Within the WNV transmission focus, 10 1-km 2 quadrants were selected, each containing a sentinel house at which WNV surveillance activities, including engorged mosquito collections, were conducted. Four of these quadrants were classified as rural, and six sites were urban because of the prevalence of urban facilities (houses, roads, bridges, etc.)…”

“…To generate density and relative abundance data for wild birds and chickens, avian point counts were performed. 2,13 Point counts were conducted along a single transect in each of the 10 1-km 2 quadrants. For each quadrant, four 4-minute counts of bird species seen or heard within 50 m were conducted within the first 3 hours of daylight.…”

“…The clay-colored thrush (Turdus grayi), great-tailed grackle (Quiscalus mexicanus), and domestic chicken (Gallus gallus) have been identified as common and frequently infected resident avian hosts within the transmission focus. 2 In 2007 and 2008, T. grayi and Q. mexicanus were among the more abundant wild bird species with the highest WNV seroprevalence rates in the transmission focus. 2 However, the relative importance of these and other tropical vertebrate species to enzootic transmission of WNV is unknown.…”

“…2 In 2007 and 2008, T. grayi and Q. mexicanus were among the more abundant wild bird species with the highest WNV seroprevalence rates in the transmission focus. 2 However, the relative importance of these and other tropical vertebrate species to enzootic transmission of WNV is unknown. In Puerto Barrios, WNV infections have been detected in Culex (Culex) quinquefasciatus Say, and Cx.…”

“…1 Intensive ecological studies of WNV were initiated within a 80-km 2 transmission focus that incorporated the city of Puerto Barrios and the rural village of Machacas del Mar in the Department of Izabal. The clay-colored thrush (Turdus grayi), great-tailed grackle (Quiscalus mexicanus), and domestic chicken (Gallus gallus) have been identified as common and frequently infected resident avian hosts within the transmission focus.…”