Veterinary session

Mermithid nematodes are a special group of the so-called parasitoid organisms, which kill their hosts during their development. They usually, infect arthropods and molluscs. These parasites have not been investigated in Hungary so far and there are no specimen collections of them. The research of these aquatic and terrestrial worms is extremely difficult because the mature specimens can only be found in soil, where they lay their eggs as well. Beetles, ants, wasps, grasshoppers, locusts and other insects, land snails and various kinds of lumbricid worms take larvae of mermithids emerged from eggs and the parasitic larvae grow to adult stage inside them.

Within the phylum Nematoda mermithids represent a distinct order (Mermithida). They are not important for veterinary point of view but are hopeful candidates for agriculture as a form of biological pest control and methods to suppress the populations of mosquitoes which are vectors of malaria. The basic work on mermithids is important for the better understanding of the host-parasite relationship, because they represent an ancient form of parasitism.

We first detected the worm Hexamermis albicans in the Gemenc forestry in Hungary that parasitizes Succinea putris land snails. The Succinea snails, also called amber snails, are the intermediate hosts of protostrongylid lungworms of ruminants and may act as intermediate hosts of more Trematoda species so the discovery of this worm contributed to better exploration of the nature of competing parasites. Remarkable feature of H. albicans is that unlike other parasites, this worm does not damage the reproductive system of snails during its development. Thus, the fertile eggs can be formed by the host snail, despite of the fact that the parasite grows in it. This phenomenon is advantageous even for the worm, because in this way the next generation can find hosts easily.

With external inspection the infection snails cannot be recognized in the effected snails. Therefore, the occurrence of Hexamermis is very rarely detected. I collected my specimens of snails after a heavy summer rain, preserved them in alcohol, and dissected their mantle cavity for the worms. The prevalence and intensity of parasites were detected in snails. The identification of the worms was performed by morphological analysis of preadult stages using manuals. .On the locality of infected snail population I attempted to collect infected individuals more times, which was only partially successful due to the dry summer. I made microscopic slide preparations suitable for subsequent molecular analysis of worms which was removed from the bodies of hosts. I tried to detect the developmental forms of H. albicans in soil, which has not been successful so far.

Further investigation is needed of H. albicans, because it might be possible to maintain the worm in laboratory, which would offer a great opportunity to perform a wide variety of research, for example testing anti-nematode products.