Management Factors Associated with Operation-Level Prevalence of Antibodies to Cache Valley Virus and Other Bunyamwera Serogroup Viruses in Sheep in the United States

Abstract

A cross-sectional study was performed to identify operation-level risk factors associated with prevalence of antibody to Bunyamwera (BUN) serogroup viruses in sheep in the United States. Sera were obtained from 5150 sheep in 270 operations located in 22 states (three in the west, nine central states, and 10 in the east) and tested at a dilution of 1:20 by a plaque reduction neutralization test (PRNT) using Cache Valley virus (CVV). Antibodies that neutralized CVV were identified in 1455 (28%) sheep. Animal-level seroprevalence was higher in the east (49%) than the central (17%) and western (10%) states. A convenient subset (n = 509) of sera with antibodies that neutralized CVV was titrated and further analyzed by PRNT using all six BUN serogroup viruses that occur in the United States: CVV, Lokern virus (LOKV), Main Drain virus (MDV), Northway virus (NORV), Potosi virus (POTV), and Tensaw virus (TENV). Antibodies to CVV and LOKV were identified in sheep in all three geographic regions; MDV and POTV activity was detected in the central and eastern states, NORV activity was restricted to the west, and antibodies to TENV were not detected in any sheep. Several management factors were significantly associated with the presence of antibodies to BUN serogroup viruses. For instance, sheep housed during the lambing season inside structures that contained four walls and a roof and a door closed most of the time were more likely to be seropositive than other sheep. In contrast, herded/open-range sheep were less likely to be seropositive than their counterparts. These data can be used by producers to implement strategies to reduce the likelihood of BUN serogroup virus infection and improve the health and management practices of sheep.

Cache Valley virus: A scoping review of the global evidence

“…Sixteen studies reported the seroprevalence of CVV in sheep ( Ovis aries 12/16 , Ovis ammon 1/16 , Ovis musimon 1/16) and in goats ( Capra aegagrus 3/16), sampling animals during an outbreak ( n = 3 studies), dams of lambs with congenital defects ( n = 1) or selected healthy populations ( n = 14) (Table , Appendix ). The single study quantitatively investigating the association between housing and CVV exposure in sheep described a significant ( p < 0.05) positive association between seroprevalence of CVV and sheep kept outside, relative to sheep kept in housing with four walls, a roof and a door closed most of the time (Meyers et al, ). This finding was consistent with a field experiment conducted in Texas, where sheep housed indoors remained CVV seronegative despite high seroconversion in pastured sheep (Crandell, Livingstone, & Shelton, ).…”

“…This finding was consistent with a field experiment conducted in Texas, where sheep housed indoors remained CVV seronegative despite high seroconversion in pastured sheep (Crandell, Livingstone, & Shelton, ). Other potential risk factors identified for CVV seropositivity included: various flock management factors; increasing age, sex and breed of animals; year of sampling and location in Eastern USA states (Meyers et al, ; Shelton, de la Bermejillo, Willingham, & Mock, ).…”

Cache Valley virus as a cause of fetal abnormalities in a litter of three Boer kids

“…10 Sheep housed inside a four-walled structure with a roof were more likely than sheep housed on open range pasture to have CVV antibodies, and this is thought to be due to fewer mosquito resting sites in open pasture. 10 The herd in this case elected to move their breeding season three weeks to coincide with lesser mosquito and insect activity, and as a result has observed no additional fetal defects, despite most animals in the herd being serologically affected. The owners of the doe reported that historical CVV infections had been present in the neighbour's sheep herd.…”

Culex tarsalis is a competent vector species for Cache Valley virus

“…Cache Valley virus (CVV) is an orthobunyavirus endemic in North America [ 1 – 9 ]. Enzootic transmission of CVV occurs among ungulates through bites of competent arthropod vectors.…”