Development ofNeostrongylus linearisinCernuella (Cernuella) virgataexperimentally infected and maintained in the subhumid climate of Galicia in northwest Spain

Abstract

Twelve batches of the mollusc Cernuella (Cernuella) virgata (Mollusca: Helicidae) were deposited monthly directly on faeces containing first-stage larvae of Neostrongylus linearis, so that they were naturally infected. Every two weeks the molluscs were examined to study the larval development of N. linearis. No correlation was found between the number of first-stage larvae of N. linearis on the faeces and the number of total larvae and third-stage larvae which developed in the snails. However, a negative correlation was found between temperature and the days needed to reach the different larval stages. Thus, the molluscs harboured third-stage larvae from mid-spring to mid-autumn, the period of time which carries the greatest risk of infection for the definitive hosts.

Larval development of Neostrongylus linearis (Nematoda, Protostrongylidae) in the mollusc Cochlicella barbara infected and maintained in a subhumid area (north-west Spain) and its possible influence on the infection of small ruminants

“…Taking into consideration the results of this study and those obtained in previous works by MorrondoPelayo et al (1992b) and Lo´pez et al (1997) carried out in this area, we conclude that, although small ruminants can be infected throughout the year, they are more likely to get infected from mid-spring to mid-autumn, and particularly in summer months. Thus it will be of interest to modify the grazing habits of small ruminants, avoiding these periods of maximum risk.…”

“…It seems that temperature is also associated with larval development, because a delay in larval development was observed in the batches of molluscs deposited in winter months, especially in January and December, that registered the lowest temperatures and in which no L3 were found. This delay was also observed by Lo´pez et al (1997) in C. virgata infected with N. linearis and maintained under natural conditions in this area, whereas Cabaret (1986) only found a delay in the development of the larvae in molluscs when the temperature was below 10°C.…”

“…Once a month, for 12 months (January-December 2002), we placed 400 g of faeces containing L1 of N. linearis and 100 uninfected C. barbara specimens in plots of 0.5 · 0.5 m constructed as in previous works (Morrondo-Pelayo et al 1987;Prieto-Novoa et al 1993;Lo´pez et al 1997); at the same time, 100 molluscs were placed in an adjacent plot without faeces acting as a control batch. The total number of plots was 24: 12 with naturally infected snails and 12 with the control ones.…”

“…Neostrongylus linearis (Marotel 1913) Gebauer 1932, is one of the most prevalent Protostrongylidae in small ruminants from the north-west of Spain (Lo´pez et al 1997). Sheep and goats excrete first-stage larvae (L1) in their faeces and to continue their development L1 have to penetrate the foot of terrestrial molluscs, which act as intermediate hosts (IHs) where they develop into thirdstage larvae (L3), which infect definitive hosts (DHs).…”

Larval development of Aelurostrongylus abstrusus (Nematoda, Angiostrongylidae) in experimentally infected Cernuella (Cernuella) virgata (Mollusca, Helicidae)

“…In this area, the snail has been demonstrated to be a suitable I.H. for different species of protostrongylids such as Muellerius capillaris and Neostrongylus linearis (Morrondo et al 1980;Lo´pez et al 1997).…”