Ovine Progressive Pneumonia Virus Is Transmitted More Effectively via Aerosol Nebulization than Oral Administration

Abstract

A new method of experimental infection of ovine progressive pneumonia virus (OPPV), aerosol nebulization (Nb), was compared to intravenous (IV) and oral (PO) methods of experimental infection. Seven month old lambs were given 3.5 × 10 7 TCID 50 of Dubois OPPV LMH19 isolate using IV, PO, or Nb methods and were monitored for infection using cELISA and OPPV quantitative (q) PCR for 35 weeks. Four out of four sheep in the IV group, six out of six sheep in the Nb group, but only two out of six sheep in the PO group became infected by OPPV; whereas the uninoculated controls (n = 2) and a sentinel control (n = 1) remained uninfected during the course of the study. The time to a cELISA or OPPV qPCR positive result in the Nb group was quicker and statistically different from the time to a cELISA or OPPV qPCR positive result in the PO group (cELISA P-value = 0.0021 and OPPV qPCR P-value = 0.0007). When the Nb and IV groups were compared, sheep became cELISA and OPPV qPCR positive at similar times (cELISA P-value = 0.6 and OPPV qPCR P-value = 0.1). In addition, sheep became OPPV qPCR positive prior to cELISA in both the IV and Nb groups (IV P-value = 0.027 and Nb P-value = 0.007). Aerosol nebulization is a more natural experimental method of transmitting OPPV and may be valuable for testing potential vaccines or specific host genetics.

Epidemiology and control of maedi-visna virus: Curing the flock

“…The delay between infection and seroconversion and its variability are well known (e.g., [9]) but have not been accurately quantified because of the difficulty of knowing when natural infections occur. Laboratory infection by efficient routes produces PCR-detectable virus typically within 1-2 months, and seroconversion follows roughly 1-4 months later [39]. Less efficient routes and lower doses of virus take longer to present detectable virus and cause longer seroconversion delays [40].…”

“…It might be expected that sheep become infectious soon after infection given the early viraemic phase 2 to 8 weeks post infection [42] and the presence of PCR-detectable virus before seroconversion (e.g., [39]). We infer from our analysis of Houwers that a latent period exists and is about 15 months, or roughly twice as long as the time from infection to seroconversion ( Table 3).…”

Prevalence of and risk factors associated with ovine progressive pneumonia in Wyoming sheep flocks

“…7 Small ruminant lentiviruses consist of many strains and isolates with differing pathogenicity, which likely accounts for the variability in disease outcomes among infected animals. 1,3,9,10 The virus is also transmitted vertically from infected ewes to lambs by in utero infection or through milk or colostrum. 1,3,9,10 The virus is also transmitted vertically from infected ewes to lambs by in utero infection or through milk or colostrum.…”