Populations of free-living stages of Ostertagia ostertagi and O. circumcincta in a winter rainfall region

Abstract

Pats of cattle faeces containing eggs of the trichostrongylid Osferfagia ostertagi and deposits of sheep faecal pellets containing eggs of O. circumcincta were placed on dry and irrigated pasture plots at four times during the period October 1977 to February 1978. Faecal pellets lost moisture far more rapidly than did dung pats. The rate of moisture loss from both faecal deposits was greater on dry plots than on irrigated plots. Despite large differences between irrigated and dry plots in soil temperature and soil and pasture moisture status, the temperatures recorded in both dung pats and faecal pellets were similar on all plots at each time of deposition. A significantly greater proportion of O . circumcincta eggs was recovered as infective larvae in faeces, on herbage and in soil compared with that of O. osterfagi eggs. Irrigation did not result in either substantially more eggs developing to infective larvae in faeces or higher recoveries of larvae from herbage and soil. No significant differences were detected in temperature or moisture measurements or in parameters of free-living development and larval survival between plots with long or short pasture herbage. There were marked differences between the population dynamics of the infective larvae of Ostertagia spp. and between the numbers of larvae on irrigated and dry plots. On dry plots, O . circumcincta migrated in abundance from faecal deposits after smaller falls of rain than were required for migration of O . ostertagi larvae. Larvae of both species persisted in abundance on the herbage of most dry plots until late spring. On irrigated plots, migration of both species of larvae occurred immediately and was independent of rainfall, but survival rate of larvae was lower than on the corresponding dry plots.

Dynamics of the free-living stages of sheep intestinal parasites on pasture in the North Island of New Zealand. 1. Patterns of seasonal development

“…This implies that conditions within the soil are substantially buffered from variations in temperature (Bryan 1976;Young 1983) and moisture that are likely to limit nematode development within faeces on the surface. That this did not occur, on occasions, in T. colubriformis may indicate that this species is less affected by some variable than the other species, although it is unclear what this might be.…”

The integration of grazing management and summer treatments for the control of trichostrongylid infections in Merino weaners

“…Furthermore, high egg output from adult sheep would be restricted to a period from mid-December until February when the second treatment is given, Figure 2, and development of these eggs to infective larvae would be substantially reduced at this time compared with spring or autumn. 13 In addition to limiting worm egg deposition, the new strategy may reduce the number of larvae present on paddocks for weaners in two other ways. The increased number of sheep that than those on the standard strategy paddocks.…”

The relationship between the rate of intake of trichostrongylid larvae and the occurrence of diarrhoea and breech soiling in adult Merino sheep

“…Because of the delay between the deposition of eggs in faeces and the availability of infective larvae on pasture, it is unlikely that eggs deposited after the ewes started grazing the experimental paddocks would have become available as infective larvae, either within 8 weeks after anthelmintic treatment on the first paddock, or within 5 weeks after starting to graze the second paddock. 17,18 The observations on sheep not dosed with L 3 , nor treated with a controlled-release capsule, confirmed that the ingestion of L 3 from pasture was not a confounding factor. Therefore, the dose of L 3 given to sheep in this experiment is a reliable estimate of their total larval intake.…”