Visna/Maedi: An Experimental study on the distribution of two viral strains with different tissue origins using the intratracheal route

Abstract

[Introduction] Visna-maedi (V/m) infection causes lesions in lungs, CNS, joints and mammary gland. Two autochthonous strains have been previously isolated from field cases where the neurological and articular presentations were the predomina nt clinical forms. The objective of this work was to study the organic distribution and pathogenesis of the different clinical forms, following intratracheal infection using those strains.

[Materials and Methods] 20 lambs, male, Rasa Aragonesa breed, negative by ELISA and PCR for V/m, were split in two groups of eight animals and a control group of four animals. Groups were infected intratracheally twice (0 and 319 dpi), either with the nervous strain (group A) or the articular strain (group B). Control group was mock-infected. Animals were evaluated by ELISA and PCR weekly. Two animals from each group and one control were killed at 134, 273 and 319 dpi.

[Results] Serology or PCR demonstrated infection in all infected animals. Serology OD from group B was higher. The specific viral strain was observed in each group. Most animals from group B presented significant lesions in lung and carpal joint, whereas few animals from group A presented lesions that were observed only at the lung. Microscopically all infected animals presented pulmonary lesions compatible with V/m, and all animals from group B presented V/m lesions on the carpal joint. The 496 strain was detected by qPCR on the carpal joint of the majority of animal s from group B.

[Conclusions] The articular strain showed the more virulent behaviour and reproduced the arthritic lesions confirming its original tropism.