Early evidence for a virus-like agent infecting the pest snail Theba pisana (Gastropoda: Pulmonata) in Southern Italy

The Mediterranean land snail Theba pisana (Mollusca: Helicidae) is an introduced agricultural pest in many countries around the world, including Australia, Israel, USA and South Africa. In addition, this snail is an intermediate host of parasites of importance in both human and veterinary medicine. In this study, a natural population of T. pisana snails on the Domitian coast of Italy was surveyed following a mass mortality event. By light microscopy, 30% of the collected individuals showed in the calcium cells of the digestive gland the presence of hypertrophied nuclei containing eosinophilic to weakly basophilic inclusion bodies. Ultrastructural examination by transmission electron microscopy (TEM) showed nuclear inclusions constituted by a reticulated stroma into which unenveloped, roundish virus-like particles (38 +/- 4 nm in diameter) were present. To the best of our knowledge this could be the first evidence for a virus-like agent infecting the gastropod T. pisana, which may open new biocontrol perspectives of the this pest worldwide.