Browsing by Author "Hale, Kristina Marjorie"

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Investigations of the West Nile virus transmission cycle at Medicine Lake National Wildlife Refuge, Montana, 2005-2006
(Montana State University - Bozeman, College of Agriculture, 2007) Hale, Kristina Marjorie; Chairperson, Graduate Committee: Gregory D. Johnson.
Outbreaks of West Nile virus (WNV) in American white pelicans (Pelecanus erythrorhynchos Gmelin) at Medicine Lake National Wildlife Refuge, Montana prompted mosquito and WNV surveillance during 2005 - 2006 to describe the epidemiological cycle. A total of 102,118 mosquitoes representing 19 species was collected throughout the refuge from 261 trap nights. Ochlerotatus dorsalis (Meigen), a floodwater mosquito, was the most abundant (45.5%), followed by Aedes vexans (Meigen) (25.6%), Culex tarsalis Coquillett (18.8%) and Ochlerotatus flavescens (Muller) (7.3%). Seasonal light trap indices (LTI) for 2005 and 2006 were 110 and 53, respectively. A total of 4,402 Cx. tarsalis mosquitoes in 2005 was assayed for WNV in 90 pools, six of which were positive. The minimum infection rate (MIR) for the season was 1.36 per 1,000 mosquitoes. In 2006, 64 pools containing 2,810 females were tested, four of which were positive, resulting in an MIR of 1.41 per 1,000 mosquitoes. Avian infection with WNV was monitored with sentinel chickens, which were shown to be ineffective as an early warning system for WNV transmission. Mosquito blood-meal identification was used to assess which species were utilizing pelicans as a host.
Proximate causation of stable fly (Stomoxys calcitrans (L.)) host use : the influence of phenology and host blood suitability
(Montana State University - Bozeman, College of Agriculture, 2011) Hale, Kristina Marjorie; Chairperson, Graduate Committee: Greg Johnson.
The biting fly, Stomoxys calcitrans (L.) (Diptera: Muscidae) has become a cosmopolitan pest of livestock, companion animals, and humans. Both males and females require daily blood meals and will opportunistically feed on many terrestrial mammals. They have rarely been seen to feed on birds, despite the presence of many potential hosts. A unique feeding behavior was documented at a wildlife refuge in northeast Montana when stable flies were seen congregating on the heads and eyes of West Nile-infected American white pelicans. The objectives of this investigation were to describe adult phenology near the pelican colony and to determine daily and lifetime fecundity when fed on cattle, horse, or chicken blood. From 2008-2010, relative adult abundance was measured by placing white Coroplast ® cards near the colony, around confinement lots, and along transects in pasture used by grazing cattle. Results showed that temporal dynamics varied by habitat type (2008: F = 7.4; df = 16, 191; P < 0.001; 2009: F = 17.7; df = 14, 270; P < 0.001) and that local dispersal occurred throughout the season. Weekly changes in abundance were explained by temperature, precipitation, and degree-days in 2008 (F = 12.2; r ² = 0.13) and 2010 (F = 13.8; r ² = 0.27) and by temperature and precipitation in 2009 (F = 164.6; r ² = 0.82). Stable flies from a laboratory-maintained colony were provided with cattle, horse, or chicken blood and daily and lifetime fecundity rates were measured through F 2 adult emergence. Flies fed chicken blood laid more eggs per day than those fed cattle (P = 0.008) or horse blood (P = 0.05), but lifetime fecundity was similar between treatments (x ² = 3.4; df = 2; P = 0.2) because of shorter oviposition periods in cohorts fed chicken blood. These results indicate that the nutritional composition of blood from these hosts does not explain the rarity of stable flies feeding on birds. Implications of host defenses as an explanation for stable fly behavior are discussed.