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The ecology of the free-living stages of Ostertagia circumcincta
THE ECOLOGY OF THE FREE-LIVING ~~~~~~~Gr~ CT~C~~C~~C~A
STAGES
OF
A. P. L. CALLINAN Regional Veterinary
Laboratory,
Victorian Department (Received
of Agriculture,
Hamilton, Victoria, 3300, Australia
1 September t 977)
A. P. L. 1978. The ecology of the free-living stages of Osterfagiu circumcinrfa. lnferafiuna/Journalj~r Parasitology 8: 233-237.The development and survival of the free-living stages 0. circumcincta was studied in western Victoria in 1974-1976. For all plots in which development
Abstract-CALLINAN
occurred, pre-infective larvae (L,- I.,) were recovered within O-8 days, infective larvae (Lj) within 7-30 days and LS on herbage and soil within 4-27 days. The mean minimum development time to L: on herbage and soil was 14.3 A 3.5 days and the mean development time to maximum yield of these was 33.3 + 6.3 days. There were no distinct differences in development rates between plots. Plot yields of LAon herbage and soil varied inversely as the mean of daily temperatures for the period until maximum yield of these. Yields varied from 0 to 16 “/, of the number of eggs put out on each plot and highest yields were obtained from eggs put out during late autumn-winter. No L3 were observed to survive over summer. The migratory habits of LA were such that a mean of 75.1 i 5.67; of L3 on herbage and soil were actually on herbage; the soil was always a significant source of L,. INDEX KEY WORDS: Osrerrta@ circrtlrrincfn;
ecology; translation
INTRODUCTION AN UNDERSTANDING of the ecology of the free-living stages of sheep nematodes is essential if maximum use is to be made of the natural processes controlling nematode populations. For this purpose there is no substitute for conducting local ecological studies (Donald, 1968). Anderson (1972, 1973) found that the most important sheep nematodes in western Victoria were Ostertagia circumcincta, Triehostrongylus axei and Tri~h~~tro~gy/l~s vitrhnrs. It was concluded that most development of first-stage eggs (E,) to thirdstage larvae (L3) on herbage, that is nematode translation, occurred in autumn-spring. To further define this translation process in western Victoria, a study was made of the development and survival of the free-living stages of these species at the Pastoral Research Institute, Hamilton, Victoria, during 1974-76. In this paper, those experiments with 0. circumcincta are reported and discussed.
MATERIALS
AND METHODS
Terminology. In order to maintain a concise presentation, time is indicated by day number of year rather than day number of month and the classification categories of Silverman & Campbell (1958) have been used to denote nematode development stages. These categories comprise 4 egg and 3 larval stages: E,-E,, early blastomere to differentiating gastrula or nonembryonated eggs; E,-E,, tadpole to prehatch larva or embryonated eggs; L,-L,, first to second stage or preinfective larvae; LI third stage or infective larvae.
233
Design. From June 1974 to January 1976, 14 plots were contaminated with sheep faeces containing El-Es of 0. circumcincta. Plots contained up to 200 sites of 0.5 m*. At the centre of each site, 30 g faeecs were deposited in a clump. After contamination, 3 sites from each plot were assayed every second or third day for 2 weeks and weekly or fortnightly thereafter until viable nematodes were not recovered. Sites for assay were selected by use of a table of random numbers. Site. The land used had not been grazed in the previous 2-3 years. Herbage assays showed it to be free of ruminant nematodes. Herbage composition was determined in September 1974; the dominant species were T~j~oiju~? ~l~bterraneum (34 “/,), Phaiaris spp. (I 5.7 %), ffo~~~~ lunatrrs (31.204) and Loiium perenne (17.3 x). Pasture length was limited to 7-15 cm, by mowings in spring. to avoid unrealistic L, survival advantages due to herbage density. It was assumed that L, do not migrate more than a few centimetres in any direction from the site of egg deposition (Michel, 1969) so that none would have been lost in discarded clippings. Nemafode source. Six Merino wetht-r weaners were infected with L, of 0. circum-cinc’ta to provide plot contaimination material. Their initial worm-free status was achieved by extensive anthelmintic treatment and the maintenance thereafter of a pure infection was ensured by the use of sterile housing conditions and processed feeds. Sheep were infected 7 times, then replaced with new weaners to take advantage of the lower nematode resistance status of animals not previously exposed to infection. Nematode assa,vs. Faeces were weighed in 200 .\ 34 g lots, the mean number of E,-E, in each was 55,522. Two Y 2 g samples were taken at random from each and assayed for E, -E,. The remaining 200 30 g were put out on the marked sites within a plot. From sites to be assayed,
234
A. P. L.
faeces were recovered and El,. ., L, counted in 2 lg samples. Because of the limited migratory capacities of L,, a 25 cm quadrat was assumed to encompass all contaminated material. Herbage and the top I cm of soil within the quadrat were carefully removed for larvae assay. E,-E, in faeces were floated in saturated NaCl (spgr. 1.2)and examined in McMaster egg-counting slides. The dilution factor per g faeces was 33 : I. EL,,. ., L, in faeces were examined in McMaster sliding top slides which reduced the dilution factor IO 1.5:1. L, were filtered from soil samples by Baermann Technique and were recovered from herbage and soil sediments by the method Smeal & Hendy (1972). They were then floated in saturated KI (sp.gr. 1.65) and counted in McMaster sliding top slides. at a dilution factor of 4: I. Me&&~fu;gy. fhe experimental site was located within 200 m of a Bureau of Meteorology weather station. As
0
I 250
I 350
C‘ALLINAN
I.J.P. YOI.. x.
197X
well as this register of meteorological observations. lnax~mum and minimum soil temperatures and 9.00 a.m, herbage relative humidity were recorded at the experimental site. Some of these observations are presented in Fig. I. RESULTS The percentages of initial egg output of 0. cimmrcincta found at each sampling day for each plot within the life cycle groups El-E,, L,-L,, and La are shown in Fig. 2. Yields and persistences of these groups and availability, that percentage of LI on herbage and soil actually on herbage, are shown in Tabie 1, together with mean daily soil temperatures and 9.00 a.m. herbage relative humidities up
I
I
85
185
I
I
I
285
20
120
285
20
60-
85
120
220
1976 FIG. I. Mean daily niaxinium and minin~um air and soil temperatures, air and herbage 9.00 am. relative humidities and rainfall, calculated at 7-day intervals from day 153, 1974 to day 199, 1976.
I.J.P.
VOL.
8.
1978
Ecology of Ostertagia circumcincfa
I .i...
_ Trr p-;
FIG. 2. Development and survival of eggs (...‘.“.,), larvae in faeces (- - ~ -) and larvae on soil and herbage (--) of 0. circumcincta, expressed as a percentage of initial egg output. to the time of maximum yield of La on herbage and soil. The lowest mean weekly maximum and minimum soil temperatures recorded (days 188-194, 1974) were 8.6 and 4.5”C. These occurred during the development of plot 1, yet all development percentages were highest for this plot. There was no development at all in plots 5 and 14. These plots were commenced on days when herbage humidities were 53 and SO%, and maximum soil temperatures were 21 and 39°C. Plots I2 and 13 showed some development even though maximum soil temperatures were 27-28°C when they were commenced. Herbage humidities in both cases were above 60% which may explain the development difference between these and plot 5. For all plots in which development occurred, L1L, were recovered within O-8 days, L, in faeces appeared within 7-30 days and La on herbage and
soil within 4-27 days. The mean minimum development time (+ 95% confidence limits) to L? on herbage and soil was 14.3 & 3.5 days. The mean development time to maximum yield of these was 33.3 i 6.3 days and their mean availability was 75.1 l 5.6%. DISCUSSION Crofton (1965) determined a lower limit of 4 C for hatching of eggs of 0. circumcincta. Gibson & Everett (1972) found that in southern England (Surrey), where weekly mean maximum soil temperature ranged from 2 to 23”C, eggs of 0. circumcincta developed at all times of the year. Since the corresponding range at Hamilton was 10.7-32QC, it is not surprising that a lower limit for development was not found. The winter in Surrey was most disadvantageous to development and survival, whereas
236
A. P. L.
TABLF
I
-MAXIMUM
OF L? (PFRC’NTAGE
WCOKDFD OF L,
YIELD
AND
ON SOIL AND
PERSISTENCE
HFRBAGE
l..l.P.
CALLINA~
OF THE FREE-LIVING
ACTUALLY
ON HERBAGE).
STAGES OF 0.
AND
circrtn cinctn.
SCMF CORRFSPO~~DI~.G
VOL.
8.
197x
AVAILABILITY
NF-IFOROLCGICAI
DATA
L,mL, persiyield stence
Starting
persistence
NO.
day/year
(days)
(%I
I
I57/1974 221/1974 287/1974 351/1974 2011975 9911975 142/1975 188/1975 22711975 27211975 307’1975 35611975 711976 1411976
I3 IO 7 2 3 5 9 7 II 4 9 4 2 2
62.2 35.82 45.68 0.44 ~7.08 12+3O 22.80 0.55 663 II.42 0.77 2.35
Plot
2 3 4 5 6 7 8 9 IO II I2 I3 I4
(days) 9 12 5
I ~ 6 9 14 8 5 7 I I
LJ
in faeces
persistence
(days)
t”/;;)
(days)
t%J
88 20 41 I ~~ I4 90 55 21 I I4
16%) I.42 I.47 0.11
I83 112 84 I5
86.74 87.50 69.55 93.93
2.50 4.60 7.39 0.63 0.62 0.99 0.04 0.02
II9 173 I32 89 51 31 I I2
85.76 64.75 69.23 77.23 97.14 78.93 I00~00
t%) 34.5 4.96 25.70 I.17 ~4.80 26.50 7.49 3.02 I.80 IO.42
western Victoria the summer was most disadvantageous. Gibson & Everett (1972) found that the time taken to recover L, of 0. circumcGrta on herbage was l484 days. In the present study the mean minimum time was 4-27 days. The discrepancy may be due to climate differences. In experiments begun in Surrey when weekly mean maximum soil temperatures were approx 7, 9 and I I C, the corresponding minimum times to recover L, on herbage, were 10, 8 and 2 weeks. At Hamilton there were no corresponding temperatures below IO C and so lengthy development periods were not experienced. In Maryland, Kates (1950) found that for experiments begun when weekly mean air temperatures were approx 17, 21 and 26’ C. L:, of 0. circumcimta were first recovered from herbage at 6, 4 and I weeks. Corresponding temperatures at Hamilton were associated with yields of L? on herbage within 2 weeks, if there was development at all. Southcott, Major & Barger (1976) using the tracer sheep technique, found that L, of 0. civcumcincta in northern New South Wales, were available within 2 -12 weeks of egg deposition. It was impossible to be very precise about development times and their relationship to time of egg deposition. Maximum yields were obtained from those plots put out in late autumn-early winter, which is in agreement with the results of the present study. Some development occurred in summer, presumably because northern New South Wales is a summer rainfall region; monthly mean 2.00 p.m. air relative humidities during summer were above 68% and higher than at any other time of the year. The range of maximum yields of L:, of 0. ci,-cumcincfa was 0 I h”;,. High yields (XI”,,) of Tridwin
L, on soil and herbage yield
yield
persistence
Availability
I00~00
Mean daily meterorological data to time of maximum yield of L I on herbage and soil 9Wa.m. Maximum Minimum relative soil temp. soil temp. humidity (‘T) (“C) ( “4 IO.7 12.7 16.2 19.4 23.1 15.9 IO.8 IO.8 12.3 15.6 20.5 27.5 28.3 28.8
6.4 7.6 9.3 Il.1 I I.8 9.9 6.4 7.2 7.7 9.2 12.2 14.0 14.9 15.4
98.6 96.3 93.9 X8.9 68.5 87.X 94. I xx.4 93.8 93.3 91.8 69.0 60, I 59. I
.sfrong~&ls spp. were also recorded by Donald (1968) though others including Boag & Thomas (1975) have estimated that less than I ‘:/, of eggs ever become available as 1~ on herbage. Highest yields of LI were obtained from eggs deposited on pasture during days 99-i 88, indicating that translation of 0. circumcirzcta, in western Victoria, was gteatest in late autumn-winter. Donald (1973) suggested that there are only 2-3 generations per year of Trichostrongylus spp. in winter rainfall districts. Since the present study indicated that some L:, were available on herbage within 14 days of egg deposition, and that nematode translation period was approx 250 days, the theoretical maximum number of generations of nematodes each year is approx 7. The mean development time to maximum yield of L, was 33 days. so that the most probable mean number of generations per year is 4. At no time was inhibited development of the preinfective stages observed. Saturation and desiccation have been shown to inhibit development at E, (Silverman & Campbell, 1958; Donald, 1973). However, in this study, survival of E,-E1 varied only from 2 to I3 days, survival times being shortest in summer and longest in winter. The migratory habits of L, were such that a mean of 75% of L, were found on herbage. Andersen. Levine & Boatman (1970) found that soil was an insignificant source of L3. However, in the present study, L:, were distributed throughout faeces, soil and herbage, though most eventually accumlated on herbage, presumably because that is where conditions are best for survival. The migration of LX from faeces persisted, for as long as the faecal pellet persisted. Persistence was greatest (88~ 90
I.J.P. VOL. 8. 1978
Ecology
of Osterfa&
days) for those plots put out in early winter; cold dry weather favoured pellet preservation. Long survival times (> 2 months) of L, of 0. circun~cimta were demonstrated by Gibson & Everett (1972) and Southcott rt al. (1976). In both localities wet mild summers did not increase L, mortalily. Kates (1950) found that survival of L3 was limited by dry summers. Anderson (1972, 1973) demonstrated similar survival limitation in bestern Victoria. In February 1967 and December, January and February 1967-68, no Lj were recovered from previously infected pasture. In the present study, the maximum survival time of LZ was the time interval bet&eel1 egg deposition and the onset of dry summer weather; no L:, survived after midJanuary 1975 and 1976. Acknowledgen;etzts~This advice and assistance O’Connor.
work was dependant of Dr. N. Anderson and
on the Mr. A.
REFERENCES ANDERSEN F. L., LEVINE N. 0. & BOATMAN P. A. 1970. The survival of third-stage Trichostrongylus colubr-if&n;is larvae on pasture. Journal of Parasiiology 56: 209-322. ANDERSON N. 1972. Trichostrongylid infeclions of shtep in a winter rainfall region. 1. Epizootiolcgical studies in the Western District of Victoria, 1966-67. Austrulim Journal of Agricultural Research 23: I 113~1129. ANDERSON N. 1973. Trichostrongyhd infeclions of shetp in a winter rainfail region. II. Epizootiological studies in the Western District of Victoria, 1967-68. Australia Jomlal of Agricultural Reseat ch 24: 599- 6 1I
circun,cincfa
237
BOAG B. & THOMAS R. J. 1975. The population dynamics of nematode parasites of sheep in northern England. Research in Veterinary Science-19: 293-295. CROFTON H. D. 1965. Ecologv__ and biological nlasticitv of sheep nematodes. I. The effect of temperature on the hatching of eggs of some nematode parasites of sheep. Cornell Veterinarian 55: 243- 250. DONALD A. D. 1968. Ecology of the free-living stages of nematode parasites of sheep. Austmlian Veterinary Journul44: 139-144. DOXALD A. D. 1973. Bionomics of the free-living stages of gastrointestinal nematodes of sheep in relation to epidemiology. Proceedings ho. 19 of Course flit Veterinarians on Parasifology ami Epidemiology, pp. 105~-1 19. University of Sydney. GIBSON T. E. & EVERETT G. 1972. The ecology of the free-living stages of 0ste;tagia circuii.ciurta. Pciuo.ritology 64: 451-460. KALES K. C. 1550. Sulvivai on pasture c,f the free-living siag-s of some common gastrointestinal nematodts of sheep. Proceedings of the Hel,,.ilithologiccrl Society qf Wmhington 17: 39-58. MICHEL J. F. 1969. The epidemioiogy and control of some nematode infections of grazing animals. In Advmces in PmaAitology (Ediied by DAWNS Bth). Vol. 7, pp. 21 l-282. SILVERMAK P. H. & CAMPBELL I. A. 1458. Studies 011 parasitic worms of sheep in Scotiand. I. Embryonic and larval development of Haemonchus contortus at constant conditions. PGxsitology 49: 23-38. SMEAL M. G. & HENDY G. A. 1572. A technique for the recovery of strongyloid iarvac from pasture. Journul of Helminthology 46: 201L2i 1. SOUTHCOIT W. H., MAJOR G. W. & BAKGER I. A. 1976. Seasonal pasture contamination and availability of nematodts for glazing sheep. Austrulim Jo~,/t;crl of Agriculturai Re.m~rh 27: 227 236. I
1
STAGES
OF
A. P. L. CALLINAN Regional Veterinary
Laboratory,
Victorian Department (Received
of Agriculture,
Hamilton, Victoria, 3300, Australia
1 September t 977)
A. P. L. 1978. The ecology of the free-living stages of Osterfagiu circumcinrfa. lnferafiuna/Journalj~r Parasitology 8: 233-237.The development and survival of the free-living stages 0. circumcincta was studied in western Victoria in 1974-1976. For all plots in which development
Abstract-CALLINAN
occurred, pre-infective larvae (L,- I.,) were recovered within O-8 days, infective larvae (Lj) within 7-30 days and LS on herbage and soil within 4-27 days. The mean minimum development time to L: on herbage and soil was 14.3 A 3.5 days and the mean development time to maximum yield of these was 33.3 + 6.3 days. There were no distinct differences in development rates between plots. Plot yields of LAon herbage and soil varied inversely as the mean of daily temperatures for the period until maximum yield of these. Yields varied from 0 to 16 “/, of the number of eggs put out on each plot and highest yields were obtained from eggs put out during late autumn-winter. No L3 were observed to survive over summer. The migratory habits of LA were such that a mean of 75.1 i 5.67; of L3 on herbage and soil were actually on herbage; the soil was always a significant source of L,. INDEX KEY WORDS: Osrerrta@ circrtlrrincfn;
ecology; translation
INTRODUCTION AN UNDERSTANDING of the ecology of the free-living stages of sheep nematodes is essential if maximum use is to be made of the natural processes controlling nematode populations. For this purpose there is no substitute for conducting local ecological studies (Donald, 1968). Anderson (1972, 1973) found that the most important sheep nematodes in western Victoria were Ostertagia circumcincta, Triehostrongylus axei and Tri~h~~tro~gy/l~s vitrhnrs. It was concluded that most development of first-stage eggs (E,) to thirdstage larvae (L3) on herbage, that is nematode translation, occurred in autumn-spring. To further define this translation process in western Victoria, a study was made of the development and survival of the free-living stages of these species at the Pastoral Research Institute, Hamilton, Victoria, during 1974-76. In this paper, those experiments with 0. circumcincta are reported and discussed.
MATERIALS
AND METHODS
Terminology. In order to maintain a concise presentation, time is indicated by day number of year rather than day number of month and the classification categories of Silverman & Campbell (1958) have been used to denote nematode development stages. These categories comprise 4 egg and 3 larval stages: E,-E,, early blastomere to differentiating gastrula or nonembryonated eggs; E,-E,, tadpole to prehatch larva or embryonated eggs; L,-L,, first to second stage or preinfective larvae; LI third stage or infective larvae.
233
Design. From June 1974 to January 1976, 14 plots were contaminated with sheep faeces containing El-Es of 0. circumcincta. Plots contained up to 200 sites of 0.5 m*. At the centre of each site, 30 g faeecs were deposited in a clump. After contamination, 3 sites from each plot were assayed every second or third day for 2 weeks and weekly or fortnightly thereafter until viable nematodes were not recovered. Sites for assay were selected by use of a table of random numbers. Site. The land used had not been grazed in the previous 2-3 years. Herbage assays showed it to be free of ruminant nematodes. Herbage composition was determined in September 1974; the dominant species were T~j~oiju~? ~l~bterraneum (34 “/,), Phaiaris spp. (I 5.7 %), ffo~~~~ lunatrrs (31.204) and Loiium perenne (17.3 x). Pasture length was limited to 7-15 cm, by mowings in spring. to avoid unrealistic L, survival advantages due to herbage density. It was assumed that L, do not migrate more than a few centimetres in any direction from the site of egg deposition (Michel, 1969) so that none would have been lost in discarded clippings. Nemafode source. Six Merino wetht-r weaners were infected with L, of 0. circum-cinc’ta to provide plot contaimination material. Their initial worm-free status was achieved by extensive anthelmintic treatment and the maintenance thereafter of a pure infection was ensured by the use of sterile housing conditions and processed feeds. Sheep were infected 7 times, then replaced with new weaners to take advantage of the lower nematode resistance status of animals not previously exposed to infection. Nematode assa,vs. Faeces were weighed in 200 .\ 34 g lots, the mean number of E,-E, in each was 55,522. Two Y 2 g samples were taken at random from each and assayed for E, -E,. The remaining 200 30 g were put out on the marked sites within a plot. From sites to be assayed,
234
A. P. L.
faeces were recovered and El,. ., L, counted in 2 lg samples. Because of the limited migratory capacities of L,, a 25 cm quadrat was assumed to encompass all contaminated material. Herbage and the top I cm of soil within the quadrat were carefully removed for larvae assay. E,-E, in faeces were floated in saturated NaCl (spgr. 1.2)and examined in McMaster egg-counting slides. The dilution factor per g faeces was 33 : I. EL,,. ., L, in faeces were examined in McMaster sliding top slides which reduced the dilution factor IO 1.5:1. L, were filtered from soil samples by Baermann Technique and were recovered from herbage and soil sediments by the method Smeal & Hendy (1972). They were then floated in saturated KI (sp.gr. 1.65) and counted in McMaster sliding top slides. at a dilution factor of 4: I. Me&&~fu;gy. fhe experimental site was located within 200 m of a Bureau of Meteorology weather station. As
0
I 250
I 350
C‘ALLINAN
I.J.P. YOI.. x.
197X
well as this register of meteorological observations. lnax~mum and minimum soil temperatures and 9.00 a.m, herbage relative humidity were recorded at the experimental site. Some of these observations are presented in Fig. I. RESULTS The percentages of initial egg output of 0. cimmrcincta found at each sampling day for each plot within the life cycle groups El-E,, L,-L,, and La are shown in Fig. 2. Yields and persistences of these groups and availability, that percentage of LI on herbage and soil actually on herbage, are shown in Tabie 1, together with mean daily soil temperatures and 9.00 a.m. herbage relative humidities up
I
I
85
185
I
I
I
285
20
120
285
20
60-
85
120
220
1976 FIG. I. Mean daily niaxinium and minin~um air and soil temperatures, air and herbage 9.00 am. relative humidities and rainfall, calculated at 7-day intervals from day 153, 1974 to day 199, 1976.
I.J.P.
VOL.
8.
1978
Ecology of Ostertagia circumcincfa
I .i...
_ Trr p-;
FIG. 2. Development and survival of eggs (...‘.“.,), larvae in faeces (- - ~ -) and larvae on soil and herbage (--) of 0. circumcincta, expressed as a percentage of initial egg output. to the time of maximum yield of La on herbage and soil. The lowest mean weekly maximum and minimum soil temperatures recorded (days 188-194, 1974) were 8.6 and 4.5”C. These occurred during the development of plot 1, yet all development percentages were highest for this plot. There was no development at all in plots 5 and 14. These plots were commenced on days when herbage humidities were 53 and SO%, and maximum soil temperatures were 21 and 39°C. Plots I2 and 13 showed some development even though maximum soil temperatures were 27-28°C when they were commenced. Herbage humidities in both cases were above 60% which may explain the development difference between these and plot 5. For all plots in which development occurred, L1L, were recovered within O-8 days, L, in faeces appeared within 7-30 days and La on herbage and
soil within 4-27 days. The mean minimum development time (+ 95% confidence limits) to L? on herbage and soil was 14.3 & 3.5 days. The mean development time to maximum yield of these was 33.3 i 6.3 days and their mean availability was 75.1 l 5.6%. DISCUSSION Crofton (1965) determined a lower limit of 4 C for hatching of eggs of 0. circumcincta. Gibson & Everett (1972) found that in southern England (Surrey), where weekly mean maximum soil temperature ranged from 2 to 23”C, eggs of 0. circumcincta developed at all times of the year. Since the corresponding range at Hamilton was 10.7-32QC, it is not surprising that a lower limit for development was not found. The winter in Surrey was most disadvantageous to development and survival, whereas
236
A. P. L.
TABLF
I
-MAXIMUM
OF L? (PFRC’NTAGE
WCOKDFD OF L,
YIELD
AND
ON SOIL AND
PERSISTENCE
HFRBAGE
l..l.P.
CALLINA~
OF THE FREE-LIVING
ACTUALLY
ON HERBAGE).
STAGES OF 0.
AND
circrtn cinctn.
SCMF CORRFSPO~~DI~.G
VOL.
8.
197x
AVAILABILITY
NF-IFOROLCGICAI
DATA
L,mL, persiyield stence
Starting
persistence
NO.
day/year
(days)
(%I
I
I57/1974 221/1974 287/1974 351/1974 2011975 9911975 142/1975 188/1975 22711975 27211975 307’1975 35611975 711976 1411976
I3 IO 7 2 3 5 9 7 II 4 9 4 2 2
62.2 35.82 45.68 0.44 ~7.08 12+3O 22.80 0.55 663 II.42 0.77 2.35
Plot
2 3 4 5 6 7 8 9 IO II I2 I3 I4
(days) 9 12 5
I ~ 6 9 14 8 5 7 I I
LJ
in faeces
persistence
(days)
t”/;;)
(days)
t%J
88 20 41 I ~~ I4 90 55 21 I I4
16%) I.42 I.47 0.11
I83 112 84 I5
86.74 87.50 69.55 93.93
2.50 4.60 7.39 0.63 0.62 0.99 0.04 0.02
II9 173 I32 89 51 31 I I2
85.76 64.75 69.23 77.23 97.14 78.93 I00~00
t%) 34.5 4.96 25.70 I.17 ~4.80 26.50 7.49 3.02 I.80 IO.42
western Victoria the summer was most disadvantageous. Gibson & Everett (1972) found that the time taken to recover L, of 0. circumcGrta on herbage was l484 days. In the present study the mean minimum time was 4-27 days. The discrepancy may be due to climate differences. In experiments begun in Surrey when weekly mean maximum soil temperatures were approx 7, 9 and I I C, the corresponding minimum times to recover L, on herbage, were 10, 8 and 2 weeks. At Hamilton there were no corresponding temperatures below IO C and so lengthy development periods were not experienced. In Maryland, Kates (1950) found that for experiments begun when weekly mean air temperatures were approx 17, 21 and 26’ C. L:, of 0. circumcimta were first recovered from herbage at 6, 4 and I weeks. Corresponding temperatures at Hamilton were associated with yields of L? on herbage within 2 weeks, if there was development at all. Southcott, Major & Barger (1976) using the tracer sheep technique, found that L, of 0. civcumcincta in northern New South Wales, were available within 2 -12 weeks of egg deposition. It was impossible to be very precise about development times and their relationship to time of egg deposition. Maximum yields were obtained from those plots put out in late autumn-early winter, which is in agreement with the results of the present study. Some development occurred in summer, presumably because northern New South Wales is a summer rainfall region; monthly mean 2.00 p.m. air relative humidities during summer were above 68% and higher than at any other time of the year. The range of maximum yields of L:, of 0. ci,-cumcincfa was 0 I h”;,. High yields (XI”,,) of Tridwin
L, on soil and herbage yield
yield
persistence
Availability
I00~00
Mean daily meterorological data to time of maximum yield of L I on herbage and soil 9Wa.m. Maximum Minimum relative soil temp. soil temp. humidity (‘T) (“C) ( “4 IO.7 12.7 16.2 19.4 23.1 15.9 IO.8 IO.8 12.3 15.6 20.5 27.5 28.3 28.8
6.4 7.6 9.3 Il.1 I I.8 9.9 6.4 7.2 7.7 9.2 12.2 14.0 14.9 15.4
98.6 96.3 93.9 X8.9 68.5 87.X 94. I xx.4 93.8 93.3 91.8 69.0 60, I 59. I
.sfrong~&ls spp. were also recorded by Donald (1968) though others including Boag & Thomas (1975) have estimated that less than I ‘:/, of eggs ever become available as 1~ on herbage. Highest yields of LI were obtained from eggs deposited on pasture during days 99-i 88, indicating that translation of 0. circumcirzcta, in western Victoria, was gteatest in late autumn-winter. Donald (1973) suggested that there are only 2-3 generations per year of Trichostrongylus spp. in winter rainfall districts. Since the present study indicated that some L:, were available on herbage within 14 days of egg deposition, and that nematode translation period was approx 250 days, the theoretical maximum number of generations of nematodes each year is approx 7. The mean development time to maximum yield of L, was 33 days. so that the most probable mean number of generations per year is 4. At no time was inhibited development of the preinfective stages observed. Saturation and desiccation have been shown to inhibit development at E, (Silverman & Campbell, 1958; Donald, 1973). However, in this study, survival of E,-E1 varied only from 2 to I3 days, survival times being shortest in summer and longest in winter. The migratory habits of L, were such that a mean of 75% of L, were found on herbage. Andersen. Levine & Boatman (1970) found that soil was an insignificant source of L3. However, in the present study, L:, were distributed throughout faeces, soil and herbage, though most eventually accumlated on herbage, presumably because that is where conditions are best for survival. The migration of LX from faeces persisted, for as long as the faecal pellet persisted. Persistence was greatest (88~ 90
I.J.P. VOL. 8. 1978
Ecology
of Osterfa&
days) for those plots put out in early winter; cold dry weather favoured pellet preservation. Long survival times (> 2 months) of L, of 0. circun~cimta were demonstrated by Gibson & Everett (1972) and Southcott rt al. (1976). In both localities wet mild summers did not increase L, mortalily. Kates (1950) found that survival of L3 was limited by dry summers. Anderson (1972, 1973) demonstrated similar survival limitation in bestern Victoria. In February 1967 and December, January and February 1967-68, no Lj were recovered from previously infected pasture. In the present study, the maximum survival time of LZ was the time interval bet&eel1 egg deposition and the onset of dry summer weather; no L:, survived after midJanuary 1975 and 1976. Acknowledgen;etzts~This advice and assistance O’Connor.
work was dependant of Dr. N. Anderson and
on the Mr. A.
REFERENCES ANDERSEN F. L., LEVINE N. 0. & BOATMAN P. A. 1970. The survival of third-stage Trichostrongylus colubr-if&n;is larvae on pasture. Journal of Parasiiology 56: 209-322. ANDERSON N. 1972. Trichostrongylid infeclions of shtep in a winter rainfall region. 1. Epizootiolcgical studies in the Western District of Victoria, 1966-67. Austrulim Journal of Agricultural Research 23: I 113~1129. ANDERSON N. 1973. Trichostrongyhd infeclions of shetp in a winter rainfail region. II. Epizootiological studies in the Western District of Victoria, 1967-68. Australia Jomlal of Agricultural Reseat ch 24: 599- 6 1I
circun,cincfa
237
BOAG B. & THOMAS R. J. 1975. The population dynamics of nematode parasites of sheep in northern England. Research in Veterinary Science-19: 293-295. CROFTON H. D. 1965. Ecologv__ and biological nlasticitv of sheep nematodes. I. The effect of temperature on the hatching of eggs of some nematode parasites of sheep. Cornell Veterinarian 55: 243- 250. DONALD A. D. 1968. Ecology of the free-living stages of nematode parasites of sheep. Austmlian Veterinary Journul44: 139-144. DOXALD A. D. 1973. Bionomics of the free-living stages of gastrointestinal nematodes of sheep in relation to epidemiology. Proceedings ho. 19 of Course flit Veterinarians on Parasifology ami Epidemiology, pp. 105~-1 19. University of Sydney. GIBSON T. E. & EVERETT G. 1972. The ecology of the free-living stages of 0ste;tagia circuii.ciurta. Pciuo.ritology 64: 451-460. KALES K. C. 1550. Sulvivai on pasture c,f the free-living siag-s of some common gastrointestinal nematodts of sheep. Proceedings of the Hel,,.ilithologiccrl Society qf Wmhington 17: 39-58. MICHEL J. F. 1969. The epidemioiogy and control of some nematode infections of grazing animals. In Advmces in PmaAitology (Ediied by DAWNS Bth). Vol. 7, pp. 21 l-282. SILVERMAK P. H. & CAMPBELL I. A. 1458. Studies 011 parasitic worms of sheep in Scotiand. I. Embryonic and larval development of Haemonchus contortus at constant conditions. PGxsitology 49: 23-38. SMEAL M. G. & HENDY G. A. 1572. A technique for the recovery of strongyloid iarvac from pasture. Journul of Helminthology 46: 201L2i 1. SOUTHCOIT W. H., MAJOR G. W. & BAKGER I. A. 1976. Seasonal pasture contamination and availability of nematodts for glazing sheep. Austrulim Jo~,/t;crl of Agriculturai Re.m~rh 27: 227 236. I
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