Incompatibility Between Miracidia of Schistosoma mansoni and Helisoma duryi Occurs at Two Stages: Penetration and Intramolluscan Establishment

Abstract

Helisoma spp. snails are not susceptible to infection with miracidia of Schistosoma mansoni because the miracidia do not penetrate them. However, in view of the phylogenetic proximity and histocompatibility between Helisoma spp. and the normal intermediate host, Biomphalaria glabrata , schistosome miracidia conceivably could survive if experimentally introduced into the hemocoel of Helisoma spp. To test this hypothesis, schistosome-susceptible NIH albino B. glabrata, schistosome-resistant Salvador B. glabrata, and Helisoma duryi were injected with miracidia of S. mansoni, and the outcome was followed both by monitoring snails for infection for several weeks and by histological examination at 24 and 48 hr post-injection (PI). Patent infections developed in most NIH albino snails but in none of the Salvador B. glabrata or H. duryi individuals. Histological analysis showed a higher proportion of normal sporocysts in various tissues of NIH albino snails at both time periods relative to Salvador snails, which contained mostly sporocysts undergoing hemocytic encapsulation. In H. duryi , nearly all sporocysts were dead by 48 hr PI.

Potamopyrgus antipodarumas a potential defender against swimmer’s itch in European recreational water bodies—experimental study

“…According to Sullivan & Yeung (2011) , miracidia that were experimentally injected into snails were encapsulated inside incompatible hosts, but survived and developed in the compatible ones only. The result shows that real recognition of the intruder by the immune system of the host depends on the internal milieu of the snail.…”

Digenean-gastropod host associations inform on aspects of specific immunity in snails

“…Species of Helisoma , the sister genus of Biomphalaria , are uniformly refractory to S. mansoni infection. Many other planorbid snails from different genera have been exposed to S. mansoni but consistently fail to take the infection (see Sullivan and Yeung, 2011). Similarly, Schistosoma haematobium normally develops only in certain species of Bulinus snails (Rollinson et al, 2001).…”

“…In several instances, a good case has been made that miracidia exert behavioral discrimination such that they penetrate appropriate snail hosts and avoid penetration of inappropriate hosts (Haas, 2003; Sullivan and Yeung, 2011). Yet there are many cases known in which miracidia readily attach to and penetrate inappropriate hosts that are not favorable to their subsequent development (see Sapp and Loker, 2000a and references therein), so much so that the use of incompatible “decoy” snails to harmlessly exhaust or absorb schistosome miracidia has been mentioned repeatedly as a means to control schistosomiasis (Chernin and Perelstein, 1971; Combes and Moné, 1987; Johnson et al, 2009).…”

“…The difference was ascribed to greater similarity between the surface carbohydrates of the sporocysts and hemocytes of the susceptible host than with sporocysts and hemocytes of the incompatible host species (Kawasaki et al, 2013). Miracidia that are experimentally injected into snails are often encapsulated in incompatible hosts, but can survive and develop in compatible hosts (Heyneman, 1966; Nunez and De Jong-Brink, 1997; Sullivan and Yeung, 2011), implying that recognition and destruction by immune system components can occur once within the internal milieu of the snail. Nunez and DeJong-Brink (1997) noted that secretory-excretory products derived from sporocysts of Trichobilharzia ocellata had a suppressive effect on bacterial clearance by hemocytes of the host snail Lymnaea stagnalis , but had no comparable effect on the hemocytes of the non-host species Planorbis corneus .…”

The immunobiological interplay between Pseudosuccinea columella resistant/susceptible snails with Fasciola hepatica: Hemocytes in the spotlight

“…Gorbushin and Iakovleva, 2008, Larson et al, 2014, Oliveira et al, 2010 or where parasite killing is effected by hemocyte-mediated cytotoxicity (e.g. Sullivan and Yeung, 2011, Gutiérrez et al, 2003b, Coustau et al, 2015. Therefore, the study of hemocytes is essential to fully understand the immunological interplay between snails and trematode parasites.…”