SURVIVAL OF SHEEP AND GOAT 1ST STAGE PROTOSTRONGYLID LARVAE IN EXPERIMENTAL CONDITIONS - INFLUENCE OF HUMIDITY AND TEMPERATURE

The survival of first-stage larvae of a laboratory strain of Muellerius capillaris and of a natural multispecific infection (Neostrongylus linearis, Cystocaulus nigrescens, Protostrongylus rufescens) was studied for 10 to 12 day periods. The survival was estimated either on larvae in faeces or kept in tap water. Temperature (-18-degrees-C to 37-degrees-C) and desiccation were the ecological factors investigated. M. capillaris was the most tolerant to these factors but showed better survival at 4-degrees-C (and at -18-degrees-C on one occasion). N. linearis survived better at 25-degrees-C or -18-degrees-C and C. nigrescens at 4-degrees-C and -18-degrees-C. Humidification of faeces was unfavourable to the latter species. All the species could stand desiccation of faeces up to 67% of dry-matter for M. capillaris or 82% for other species. Larval survival estimated for L1 in tap water was different from that estimated for larvae in faeces. The variation in resistance to unfavourable temperatures or moisture conditions may account partly for the geographical distribution of the species.