Recipient Organization
UNIVERSITY OF ILLINOIS
2001 S. Lincoln Ave.
URBANA,IL 61801
Performing Department
VETERINARY PATHOBIOLOGY
Non Technical Summary
Regionalization is an attempt to partition the risk of infection over spatial & temporal scales, minimizing the risk of spreading infectious agents when animals and animal products are moved. Both Bluetongue virus (BTV) & epizootic hemorrhagic disease virus (EHDV)are transmitted by biting midges in the genus Culicoides, are ideally suited to this process of regionalization & risk map development: their distributions are highly heterogeneous geographically & temporally & their presence can impose trade restrictions. Therefore, the specific objectives of this project are to: 1) describe the epidemiology of BTV & EHDV within cattle herds, 2) determine the distribution & abundance of Culicoides spp., and 3) use BTV, EHDV, environmental & insect data to develop a dynamic risk map that can be used for regionalization of BTV & EHDV in the U.S. We will perform a longitudinal 3-year study on approximately 60 dairy operations in Illinois. Animals on each farm will be sampled
once per year in order to calculate the incidence of BTV and EHDV exposure. Using meteorological, environmental, and entomological data, predictive models will be generated for Culicoides distribution. These models will be used to map the predicted distribution of vectors, and, along with seroconversion data, will be used to generate BTV and EHDV risk maps that will form the basis of regionalization. This approach will aid the future sustainability of agriculture and animal industries within the United States by providing a more rational approach to policies related to the movement of animals and animal products.
Animal Health Component
100%
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
Bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) are related Orbiviruses vectored by biting midges in the genus Culicoides. Bluetongue disease (BT), the clinical manifestation of infection with BTV, is the only Organization International des Epizooties (OIE) Schedule A disease that is endemic in a significant portion of the U.S. Not only is BT a threat to the health of domestic and wild ruminants throughout much of the country, but its classification in Schedule A poses a costly impediment to U.S. agricultural trade (particularly of cattle and germplasm). Illinois represents one of the toughest areas of the country in which to assess trade policies and sampling strategies relative to BTV because the prevalence is extremely low (but not zero), both BTV and EHDV are present within the state, both of the potential vectors, C. variipennis sonorensis and C. v. variipennis s. s., are present within the state, and the annual incidence rates of BTV and
EHDV are unknown. A study that assesses the incidence and distribution of BTV, EHDV, their Culicoides vectors, as well as the risk factors for exposure to these viruses would be invaluable for regionalization efforts. Therefore, the specific objectives of this 3-year project are to: 1) Describe the epidemiology of BTV and EHDV within cattle herds in a transitional region of the U.S., 2) Determine the distribution of Culicoides spp. in a transitional region of the U.S. and assess the factors that influence this distribution, and 3) Develop dynamic risk maps that can be used for regionalization of BTV and EHDV in the U.S.
Project Methods
Approximately 60 dairy cattle herds within Illinois will be enrolled. Herds will be selected proportional to herd density and expected incidence of BTV and EHDV seroconversion, using 12 sampling zones within the state. A minimum of 4 herds will be selected per zone, with more herds added in the zones with higher herd density and with a lower expected incidence of BTV and EHDV exposure. The sampling design will enable more precise estimates of incidence in low infection zones. Within selected herds, all animals at least 1 year of age will be blood sampled if herd size is <60. If a herd has >60 animals, then 60 randomly selected individuals over 1 year of age will be blood sampled. All animals enrolled in the study will be blood sampled between March and June of each year of the study. For each animal, origin, date of arrival on the premises (if applicable) and age will be recorded. Herd-level information will be collected, including herd size, stocking rate, geographic
location, proximity to other herds, and proximity to deer herds. The precise geographic location of each herd will be determined. In the Fall of each year, Culicoides spp. larvae will be collected from several sites at each dairy and reared for to adult for identification. Serum will be tested for antibodies to BTV and EHDV. Incidence rates of exposure will be calculated. Logistic regression models will be developed to determine risk factors for exposure to BTV and/or EHDV. For the insect data, we will describe in detail the different species of Culicoides that are associated with livestock within Illinois. We will begin to assess the factors that influence the distribution of C. v. sonorensis and the potential for BTV transmission throughout the state. Finally, we will use a geographic information system, remotely sensed data, the risk factor models and the Culicoides spp. distribution data to develop maps that predict the risk of BTV and EHDV transmission over spatial and temporal
scales. These maps will form the basis for regionalization efforts. This study will greatly increase our basic knowledge of BTV and EHDV epidemiology and Culicoides spp. ecology in a region of the U.S. that has not been intensively studied. In addition, we will apply methodology that will ultimately be useful for creating scientifically valid trade policy.