Data/hora: 24/06/2024 05:58:57

Biblioteca(s): 	Embrapa Pantanal.	
Data corrente: 	15/08/1995	
Data da última atualização: 	15/08/1995	
Autoria: 	SILVERMAN, P. H.; CAMPBELL, J. A.	
Título: 	Studies on parasitic worms of sheep in Scotland. I.Embryonic and larval development of Haemonchus contortus at constant conditions.	
Ano de publicação: 	1959	
Fonte/Imprenta: 	Parasitology, v.49, p.23-38, 1959.	
Idioma: 	Inglês	
Conteúdo: 	Laboratory studies on the embryonic and larval development of Haemonchus contortus under constant temperatures of 0.0, 7.2, 11, 14.4, 21.7 and 37C., and varying moisture conditions were carried out. Reports of preliminary studies on Ostertagia spp., Trichostron-
gylus spp. and Oesophagostomum venulosum are included. Observations showed that eggs in the same culture may behave in several ways: (1) eggs may develop at different rates; (2) eggs may exhibit intermittent stages of active and inhibited development; and (3) eggs may fail to develop and die at any stage from unknown causes. At a constant temperature of 21.7C. and with adequate moisture and aeration, frshly passed H. contortus eggs require 5 days before the first of them reach the third larval stage. At 14.4C. it takes 9 days, whilst at 11C. at least 15 days must pass before third-stage larvae first appear. Some larval development can proceed at a temperature as low as 7.2C. Mortality and inhibition vary with temperature. The proportion of eggs which survives to the prehatch stage varies between 10 and 90% with a maximum survival at 11 and 14.4C. Embryonated eggs are found to be very much more resistant to adverse conditions than unembryonated eggs. Embryonated eggs survive at 7.2C for up to 4 months. Excess water was found to inhibit development, probably owing to its interference with aeration. The period of survival of eggs in saturated faecal cultures maintained at different temperatures was determined. Rapid desiccation of faecal pellets resulted in the destruction of the contained nematode eggs unless the eggs were in an advanced stage of embryonation. Eggs in the prehatch stage were found to be extremely resistant and were kept in a dry condition for up to 6 weeks in an unhtched though viable state. Owing to the disparate conditions in faecal cultures which result in varying degree of inhibition, it was found that there is a discontinuous development of first-, second- and third-stage larvae over a considerable period of time. The relation of these laboratory observations to the conditions occurring in the field are discussed, and it is concluded that H. contortus requires about 2 weeks in the summer for development from egg to third-stage larvae and considerably longer periods are needed at other times of the year. From preliminary studies on other strongyloid species, the evidence indicatyes that their cycle of development is even more prolonged and that their ability to endure adverse conditions is better developed.	
Palavras-Chave: 	Desenvolvimento; Development; Embrionic; Larval; Lombriga; Parasita; Parasitic worms.	
Thesagro: 	Carneiro; Embrião; Haemonchus Contortus; Larva.	
Thesaurus Nal: 	sheep.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Pantanal (CPAP)	
Exemplares: 	CPAP - (29173-1) - ADD - SP - -- - SP0841 -  - 0841 - DIS