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Maedi-visna and sheep pulmonary adenomatosis: a study of concurrent infection
M Dawson1, S H Done, C Venables
1Central Veterinary Laboratory, New Haw, Weybridge.
Abstract:
The transmission of maedi-visna (MV) virus was studied within two groups of sheep, one of which was also affected with sheep pulmonary adenomatosis (SPA). Serological monitoring of sheep kept in contact with both groups indicated that MV virus replication occurred to a greater extent in the group with both diseases, three of five in-contact sheep being seropositive after 1 year's exposure compared with none of six held with MV-virus-only infected lambs.
Insights
Maedi-visna virus (MVV) transmission increased in sheep co-infected with sheep pulmonary adenomatosis (SPA). Concurrent SPA infection appears to enhance MVV replication and spread in affected sheep flocks.
Area of Science:
- Veterinary Virology
- Sheep Pathology
- Infectious Disease Transmission
Background:
- Maedi-visna virus (MVV) causes a progressive multisystemic disease in sheep.
- Sheep pulmonary adenomatosis (SPA) is a neoplastic disease of the ovine lung.
- The interaction between MVV and SPA infections in sheep is not well understood.
Purpose of the Study:
- To investigate the effect of co-infection with sheep pulmonary adenomatosis (SPA) on the transmission of maedi-visna virus (MVV) in sheep.
- To compare MVV replication and spread in sheep with single MVV infection versus those with dual MVV and SPA infections.
Main Methods:
- Two groups of sheep were established: one infected with MVV only, and another with both MVV and SPA.
- Serological monitoring was conducted on in-contact sheep exposed to these infected groups for one year.
- Seropositivity was used as an indicator of MVV replication and transmission.
Main Results:
- In-contact sheep exposed to the group with both MVV and SPA showed higher seropositivity rates.
- Three out of five in-contact sheep exposed to the dual-infected group became seropositive for MVV after one year.
- None of the six in-contact sheep exposed to the MVV-only infected group became seropositive.
Conclusions:
- Co-infection with SPA significantly enhances the transmission and replication of maedi-visna virus in sheep.
- The presence of SPA may exacerbate MVV shedding or increase host susceptibility, facilitating virus spread.
- These findings highlight the importance of managing co-infections in sheep flocks to control viral diseases effectively.