Physiological alterations in Pseudosuccinea columella (Mollusca: Gastropoda) after infection by Heterorhabditis baujardi LPP7 (Rhabditida: Heterorhabditidae)

The snail Pseudosuccinea columella participates in the distribution of Fasciola hepatica in the environment by acting as its intermediate host. Therefore, the control of this lymnaeid is one of the ways to prevent hepatic fascioliasis. The objective of this study was to evaluate the susceptibility of P. columella to infective juveniles (IJs) of the entomopathogenic nematode (EPN) Heterorhabditis baujardi in laboratory conditions, as well as to investigate aspects related to the biochemistry and histopathology of snails exposed or not to the EPNs during three weeks. The EPN exposure induced significant reductions in the concentrations of glucose, total proteins and glycogen (gonad-digestive gland complex) in the snails during the onset of the infection, with the levels being restored as the infection progresses. These alterations were accompanied by increased hemolymph activities of aminotransferases and lactate dehydrogenase, as well as the concentrations of uric acid after the first and second weeks of the experiment. The histopathological analyses of the exposed snails revealed cell necrosis at the end of the first week, tissue inflammatory reactions one and two weeks after exposure, and degeneration three weeks afterward in comparison with the unexposed snails. Finally, scanning electronic microscopy revealed proliferation of fibrous connective tissue three weeks after exposure. The results indicate that P. columella is susceptible to H. baujardi. The exposure favored the establishment of a negative energy balance, increased the activity of enzymes related to tissue damages and promoted accumulation of nitrogen compounds in the host snails. Additionally, was observed in P. columella exposed to the EPNs, significant tissue lesions, and demonstrated the strong pathogenic potential of H. baujardi, indicating its possible application for biological control of this snail.