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 × 107 TCID50 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.
Highlights
The small ruminant lentiviruses (SRLVs) include ovine progressive pneumonia virus (OPPV), visna/maedi virus (VMV) and caprine arthritis-encephalitis virus (CAEV)
Six sheep were aerosol nebulized with 3.5 × 107 tissue culture infectious doses at 50% (TCID50) of Dubois OPPV LMH19 and all six became OPPV infected based on a positive result by cELISA and OPPV quantitative PCR (qPCR) at two consecutive time points, and a positive western blot result at 211 days post-infection
Only two out of six sheep PBS was given orally (PO) administered with Dubois OPPV LMH19 became OPPV infected as determined by cELISA, OPPV qPCR, and western blot analysis
Summary
The small ruminant lentiviruses (SRLVs) include ovine progressive pneumonia virus (OPPV), visna/maedi virus (VMV) and caprine arthritis-encephalitis virus (CAEV). OPPV infection at a minimum results in life-long persistent infection of sheep and may cause clinical signs and histopathological lesions as sheep age. Swollen carpal joints, wasting, dypsnea, and ataxia, and histopathological lesions are detected in the congruent tissues such as mammary gland, synovial membranes, lung, and brain. Since clinical signs are variable and histopathological assessment is performed post-mortem, antemortem detection of infection is reliant upon highly sensitive and specific serological and molecular diagnostic tests [1,2,3]. Since there is no known treatment or effective vaccine for SRLVs, annual diagnostic testing followed by removal or separation of infected animals has been the main tool in controlling the number of infected animals
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