The ecology of Haemonchus contortus in a winter rainfall region in Australia: the development of eggs to infective larvae

1993 ◽  
Vol 45 (3-4) ◽  
pp. 275-292 ◽  
Author(s):  
R.B. Besier ◽  
J.D. Dunsmore
Keyword(s):  
Haemonchus Contortus ◽  
Winter Rainfall ◽  
Infective Larvae ◽  
Rainfall Region

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

1983 ◽  
Vol 34 (5) ◽  
pp. 569 ◽  
Author(s):  
RR Young
Keyword(s):  
Population Dynamics ◽  
Survival Rate ◽  
Larval Survival ◽  
Moisture Loss ◽  
Free Living ◽  
Winter Rainfall ◽  
Faecal Pellets ◽  
Infective Larvae ◽  
Cattle Faeces ◽  
Rainfall Region

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.

Trichostrongylid infections of sheep in a winter rainfall region. I. Epizootiological studies in the Western District of Victoria, 1966-67

1972 ◽  
Vol 23 (6) ◽  
pp. 1113 ◽  
Author(s):  
N Anderson
Keyword(s):  
Haemonchus Contortus ◽  
Seasonal Distribution ◽  
Post Mortem ◽  
Fourth Stage ◽  
Winter Rainfall ◽  
Merino Sheep ◽  
Region I ◽  
Low Levels ◽  
Rainfall Region ◽  
Previous Summer

Regular post-mortem counts from 'tracer' and flock sheep, together with faecal worm egg counts and plasma pepsinogen determinations, formed the basis of an epizootiological study of trichostrongylid infections of Merino sheep in the Western District of Victoria. Species from genera Trichostrongylus, Ostertagia and Nematodirus predominated in the worm counts; Haemonchus contortus was absent. Counts of Ostertagia and Trichostrongylus spp. from successive groups of 'tracer' sheep showed a pronounced seasonal distribution of available larvae in accordance with the temperature and humidity components of the prevailing weather. Mean worm counts ranging from 2000 to 32,000 per fortnight were recorded between May and October, whereas at other times the counts were consistently less than 500. When the availability of larvae was high, faecal worm egg counts of weaners and adult sheep were less than 150 epg. At this time the majority of the worms in the abomasum were early fourth stage larvae. Some weeks after availability had decreased to low levels, mean egg counts increased from 100 to values over 700 epg. It was concluded that the high levels of larval availability were derived from worm eggs deposited in the previous summer and autumn. Resistance to the establishment of worms was evident in both young and mature sheep. It was found that raised plasma pepsinogen levels, indicative of severe abomasal lesions, were closely related to the numbers of newly ingested larvae. Liveweights and fleece weights of weaners treated with 88 mg thiabendazole per kg every 14 days and those from untreated weaners did not differ significantly until the availability of larvae decreased to low levels, after which the treated sheep were heavier and produced 0.52 kg or 14.6% more wool per head.

Occurrence of putatively resistant plantago in the winter rainfall region of South Africa: a survey

2021 ◽  
Vol 38 (5) ◽  
pp. 411-415
Author(s):  
Vhuthu Ndou ◽  
Ethel E Phiri ◽  
Frederik H Eksteen ◽  
Petrus J Pieterse
Keyword(s):  
South Africa ◽  
Winter Rainfall ◽  
Rainfall Region

Improved Methods of Obtaining Clean Larvae of Haemonchus contortus

1963 ◽  
Vol 37 (4) ◽  
pp. 251-254 ◽  
Author(s):  
M. G. Christie ◽  
J. E. Patterson
Keyword(s):  
Free Surface ◽  
Surface Area ◽  
Haemonchus Contortus ◽  
Water Repellent ◽  
Optimum Conditions ◽  
Infective Larvae ◽  
Mucous Coat ◽  
Third Stage ◽  
Free Surface Area ◽  
Improved Methods

A pellet of sheep faeces containing eggs of Haemonchus contortus forms an adequate environment for the development of those eggs to third stage infective larvae, provided that it is kept moist. Observation shows a concentration of developing larvae on the external mucous coat of the pellet. These data suggest that optimum conditions for development would occur when pellets are separated one from another and standing on a water repellent surface, thus presenting the maximum free surface area and minimum opportunity for aggregation and hence of over crowding. The best method of recovering the infective larvae would be one that obtained larvae free from contamination without requiring them to expend energy in separating themselves from the contamination.

Studies on resistance of sheep to infestation with Haemonchus contortus and Trichostrongylus spp. and on the immunological reactions of sheep exposed to infestation. I. The preparation of antigens for the complement fixation test and the reactivity of the biochemical fractions of H. contortus

1950 ◽  
Vol 1 (3) ◽  
pp. 285 ◽  
Author(s):  
DF Stewart
Keyword(s):  
Haemonchus Contortus ◽  
Complement Fixation Test ◽  
Complement Fixation ◽  
Fixation Test ◽  
Mature Adult ◽  
Infective Larvae ◽  
Lipid Fractions ◽  
Significant Difference ◽  
Third Stage ◽  
Free Material

All antigen was developed to detect circulating antibodies by means of the complement fixation test in sheep infested with Haemonchus contortus and Trichostrongylus spp. Extraction of worm material at 100°C. for 10 minutes was found to be the most satisfactory method for the preparation of antigens. Potent antigens were prepared from young adult H. contortus, from third-stage infective larvae, and from the eggs. Old mature adult H. contortus yielded antigens of low potency. No significant difference was found between the potency of antigens prepared from male and female adult H. contortus collected from the same sheep. Both adult Trichostrongylus spp. and third-stage infective larvae consistently yielded antigens of high potency. No significant difference was found in the results obtained with larval or adult H. contortus antigens, adjusted to the same potency and tested with natural H. contortus antisera. H. contortus and Trichostrongylus spp. absorbed the antiserum to each other. It was shown that a lipid was an essential constituent of the boiled antigen in the complement fixation reaction with natural antisera. Lipid-free antigens from H. contortus failed to react with natural antisera. The lipid was not antigenic when injected into rabbits. The carbohydrate fraction of H. contortus did not fix complement in the presence of natural antisera and was not antigenic when injected into rabbits. The lipid fraction of a variety of nematode parasites reacted with natural antisera to H. contortus infestation. Similar lipid fractions of two species of trematodes did not react with natural antisera to H. contortus infestation. Normal saline suspensions of the lipid-free material from a variety of helminths showed a greater degree of specificity when tested with artificially prepared antisera than did the lipid fractions.

Kinetics of exsheathment of infective ovine and bovine strongylid larvae in vivo and in vitro

Parasitology ◽  
2002 ◽  
Vol 125 (1) ◽  
pp. 65-70 ◽  
Author(s):  
H. HERTZBERG ◽  
U. HUWYLER ◽  
L. KOHLER ◽  
St REHBEIN ◽  
M. WANNER
Keyword(s):  
Haemonchus Contortus ◽  
Buffer System ◽  
Bicarbonate Concentration ◽  
Infective Larvae ◽  
Nylon Mesh ◽  
Mesh Bags ◽  
Sheep Rumen ◽  
Kinetics Of

The aim of the study was to investigate the longitudinal changes of exsheathment of ovine and bovine 3rd-stage strongylid larvae in an artificial rumen (RUSITEC) and to compare the results with in vivo data obtained from rumen-fistulated sheep. Infective larvae were incubated in nylon mesh bags in the sheep rumen or the RUSITEC apparatus for periods of 1, 6 and 12 h, respectively. The 12 h exsheathment rates in the rumen and the RUSITEC apparatus (in parentheses) were as follows: Haemonchus contortus: 100% (100%), Ostertagia circumcincta: 100% (76%), O. leptospicularis: 100% (100%), O. ostertagi: 53% (59%), Trichostrongylus axei: 100% (100%), T. colubriformis: 37% (36%), Cooperia curticei: 94% (76%), C. oncophora: 95% (89%), Nematodirus filicollis: 0% (N.D.), N. spathiger: 11% (15%), N. battus: 7% (5%), Oesophagostomum venulosum: 17% (9%), Chabertia ovina: 7% (2%), Dictyocaulus filaria: 1% (N.D.). Larvae of Nematodirus spp. and T. colubriformis showed a quick rise of the exsheathment rate 2 h after transfer into the abomasum. These results confirm that exsheathment generally occurs in the part of the gastrointestinal tract immediately anterior to the habitat of the adult parasite. The overall similar course of exsheathment in both systems indicates that the essential stimuli for exsheathment were generated and maintained under in vitro conditions of the artificial rumen. In both systems, the bicarbonate concentration and the pH reflected a similar status of the H2CO3/HCO buffer system, which is known to provide the essential stimuli for larval exsheathment of the abomasal species. These results give evidence that the RUSITEC system represents a valid system for studying the kinetics of exsheathment of strongylid nematodes under in vitro conditions. For 7 of the species investigated the obtained results represent the first data on larval exsheathment in vivo and in vitro.

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