Fine morphology and phylogeny of Spiroplasma sp. isolated from eyes of scrapie sheep

Abstract

Spiroplasma sp. isolated from eyes of sheep with terminal scrapie were reported previously to produce intracellular pathology typical for neurodegenerative diseases in experimentally infected cell lines (Bastian et al., 2014). These isolates have not been yet characterized morphologically or genetically. The paper presents light and electron microscopic description, as well as 16SrDNA sequence data-based phylogenetic analysis of these isolates grown cell-free. The microorganisms were elongated cells of transient helicity up to 10 μm long, and about 100 nm in diameter. Transmission and scanning electron microscopies revealed variable morphology, including presence of helical and non-helical forms. The 16SrDNA from the novel isolates revealed >99.9% similarity to the orthologues from S. chrysopicola and S. syrphidicola, common commensals of tabanid and syrphid flies. On phylogenetic trees the scrapie sheep isolates fell into the S. chrysopicola—S. syrphidicola—TAAS group of Diptera-associated species suggesting likely route of infection through flies contacting eyes of sheep in pastures. The question, whether microorganisms occasionally contaminate eyes of sheep with terminal scrapie upon contacts with flies, or spiroplasmas are linked with the disease, and tabanids play a role of their obligate or facultative vectors and reservoirs, warrants further investigation.