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- Title
Incidence of Ovine Progressive Pneumonia (OPP) in a Flock of Landrace Hair Sheep: Impact on Performance and Implications for Mode of Transmission.
- Authors
Wildeus, S; Tessema, G
- Abstract
Ovine Progressive Pneumonia (OPP) is a viral disease of sheep with an estimated prevalence of 30% in the U.S. Clinical signs are exhibited later in life and include progressive weight loss and hardening of the udder. This project evaluated the incidence of OPP in a flock of hair sheep and its relation to performance. Blood samples were collected by jugular venipuncture in mature animals (n=112) of a Barbados Blackbelly and St. Croix breed hair sheep flock managed on pasture and under accelerated mating. Samples were cooled and forwarded overnight to the State Animal Health Lab for detection of OPP antibodies using an ELISA assay. A competitive enzyme-linked immunosorbent assay (cELISA) test method was used for the detection of antibodies to the gp135 of the OPP virus. Frequency data were analyzed by chi-square analysis and performance data by analysis of variance. Overall infection rate was 52.7%, and was higher (P<0.05) in rams than ewes (66.6 vs. 45.2%), and in Barbados Blackbelly than St. Croix (61.8 vs. 46.3%). There were 42 dam-offspring pairs, and in 71.4% of pairs OPP status of the offspring matched that of the dam. In non-matching pairs, 11.9% of negative dams had positive offspring, and 16.7% of positive dams had negative offspring, suggesting that vertical transmission was not the sole mode of infection in this flock. Analysis of the age structure of the ewe flock (ranging from 1 to 13 years) indicated no changes in frequency of infection rate with age, suggesting that no preferential culling of animals from the ewe flock related to OPP infection due to performance or death had occurred. The effect of OPP status on ewe performance was evaluated by comparing litter size and weight at weaning from the most recent 2-year accelerated mating cycle. There was no difference (P>0.05) in litter size (1.72 vs. 1.62) and 60-day litter weaning weight (22.2 vs. 21.9 kg) in OPP negative and positive ewes. In this flock ewes are routinely assigned an udder score based on signs of hardness and presence of lumps at the time of weaning to assist in ewe culling decision, and again, no difference (P=0.62) in udder score between OPP negative and positive ewes were observed. Data suggest that impact of OPP on performance of this flock was limited and that control measures may have to account for horizontal transmission.
- Subjects
MAEDI-visna disease; HAIR sheep; VIRUS diseases in sheep
- Publication
Journal of Animal Science, 2018, Vol 96, p72
- ISSN
0021-8812
- Publication type
Abstract
- DOI
10.1093/jas/sky027.135