Hostname: page-component-78c5997874-mlc7c Total loading time: 0 Render date: 2024-11-10T13:36:22.561Z Has data issue: false hasContentIssue false
  • English
  • Français

Variation among faecal egg counts following natural nematode infection in Scottish Blackface lambs

Published online by Cambridge University Press:  06 October 2005

M. J. STEAR ,
O. ABUAGOB ,
M. BENOTHMAN ,
S. C. BISHOP ,
G. INNOCENT ,
A. KERR  and
S. MITCHELL
M. J. STEAR
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
O. ABUAGOB
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
M. BENOTHMAN
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
S. C. BISHOP
Affiliation:
Roslin Institute (Edinburgh), Roslin, Midlothian EH25 9PS
G. INNOCENT
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
A. KERR
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
S. MITCHELL
Affiliation:
Glasgow University Veterinary School, Bearsden Road, Glasgow G61 1QH
Get access Rights & Permissions [Opens in a new window]

Abstract

Faecal egg counts were examined in 2 flocks of naturally infected Scottish Blackface sheep in southern and central Scotland. The distribution of mean counts was right skewed and similar to a gamma distribution. The counts varied with month, with mean counts rising from May to July, then falling but rising again in October, although data within each year did not always show such a clear pattern. There was no significant difference in mean egg count between the 2 farms examined. The distribution of egg count variances was also right skewed and conformed to a gamma distribution. There was a strong relationship between the mean and the variance for each population, implying that variation among populations in variances largely mirrored variation in mean egg counts. Populations with high mean egg counts and variances did not necessarily have more adult nematodes but had a greater number of adult nematodes from species other than Teladorsagia circumcincta, particularly Cooperia spp., Trichostrongylus axei and Trichostrongylus vitrinus. The contribution of different parasite species to the egg count explains the relatively poor and inconsistent fit of the negative binomial distribution to faecal egg counts in lambs.

Keywords

sheepnematodeegg countsvariancenegative binomial
Type
Research Article
Information
Parasitology , Volume 132 , Issue 2 , February 2006 , pp. 275 - 280
Copyright
2005 Cambridge University Press

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

Anderson, R. M., Gordon, D. M., Crawley, M. J. and Hassell, M. P. ( 1982). Variability in the abundance of animal and plant species. Nature, London 296, 245–248.CrossRefGoogle Scholar
Armour, J., Jarrett, W. F. H. and Jennings, F. W. ( 1966). Experimental Ostertagia circumcincta infections in sheep: Development and pathogenesis of a single infection. American Journal of Veterinary Research 27, 1267–1278.Google Scholar
Bairden, K. ( 1991). Ruminant parasitic gastroenteritis: some observations on epidemiology and control. Ph.D. thesis, University of Glasgow,
Bishop, S. C. and Stear, M. J. ( 2000). The use of a gamma-type function to assess the relationship between the number of adult Teladorsagia circumcincta and total egg output. Parasitology 121, 435–440.CrossRefGoogle Scholar
Bisset, S. A., Morris, C. A., McEwan, J. C. and Vlassoff, A. ( 2001). Breeding sheep in New Zealand that are less reliant on anthelmintics to maintain health and productivity. New Zealand Veterinary Journal 49, 236–246.CrossRefGoogle Scholar
Bliss, C. I. and Fisher, R. A. ( 1953). Fitting the negative binomial distribution to biological data. Biometrics 9, 176–200.CrossRefGoogle Scholar
Boag, B., Hackett, C. A. and Topham, P. B. ( 1992). The use of Taylor's power law to describe the aggregated distribution of gastro-intestinal nematodes of sheep. International Journal for Parasitology 22, 267–270.CrossRefGoogle Scholar
D'Agostino, R. B. and Stephens, M. A. ( 1986). Goodness-of-Fit Techniques. Marcel Dekker, New York.
Gordon, H. M. and Whitlock, H. V. ( 1939). A new technique for counting nematode eggs in sheep faeces. Journal of the Council for Scientific and Industrial Research, Australia 12, 50.Google Scholar
Grafen, A. and Woolhouse, M. E. J. ( 1993). Does the negative binomial distribution add up? Parasitology Today 9, 475–477.Google Scholar
Hunter, G. C. and Quenouille, M. H. ( 1952). A statistical examination of the worm egg count sampling technique for sheep. Journal of Helminthology 26, 157–170.CrossRefGoogle Scholar
Keeling, M. J. ( 2000). Simple stochastic models and their power-law type behaviour. Theoretical Population Biology 58, 21–31.CrossRefGoogle Scholar
Kilpatrick, A. M. and Ives, A. R. ( 2003). Species interactions can explain Taylor's power law for ecological time series. Nature, London 422, 65–68.CrossRefGoogle Scholar
Littell, R. C., Milliken, G. A., Stroup, W. W. and Wolfinger, R. D. ( 1996). SAS System for Mixed Models. SAS Institute, Inc., Cary, North Carolina.
Perry, J. N. ( 1981). Taylor's power law for dependence of variance on mean in animal populations. Applied Statistics 30, 254–263.CrossRefGoogle Scholar
Sokal, R. and Rohlf, F. J. ( 1995). Biometry. 3rd Edn. W. H. Freeman, New York.
Stear, M. J., Bairden, K., Bishop, S. C., Gettinby, G., McKellar, Q. A., Park, M., Strain, S. A. J. and Wallace, D. S. ( 1998). The processes influencing the distribution of parasitic nematodes among naturally infected lambs. Parasitology 117, 165–171.CrossRefGoogle Scholar
Stear, M. J., Bairden, K., Duncan, J. L., Gettinby, G., McKellar, Q. A., Murray, M. and Wallace, D. S. ( 1995). The distribution of faecal nematode egg counts in Scottish Blackface lambs following natural, predominantly Ostertagia circumcincta infection. Parasitology 110, 573–581.CrossRefGoogle Scholar
Stear, M. J., Bairden, K., Innocent, G. T., Mitchell, S., Strain, S. A. J. and Bishop, S. C. ( 2004). The relationship between IgA activity against fourth-stage larvae and density-dependent effects on the number of fourth-stage larvae of Teladorsagia circumcincta in naturally infected sheep. Parasitology 129, 363–369.CrossRefGoogle Scholar
Stear, M. J. and Bishop, S. C. ( 1999). The curvilinear relationship between worm length and fecundity of Teladorsagia circumcincta. International Journal for Parasitology 29, 777–780.CrossRefGoogle Scholar
Stear, M. J., Strain, S. A. J. and Bishop, S. C. ( 1999). How lambs control infection with Ostertagia circumcincta. Veterinary Immunology and Immunopathology 72, 213–218.CrossRefGoogle Scholar
Taylor, L. R. ( 1961). Aggregation, variance and the mean. Nature, London 189, 732–735.CrossRefGoogle Scholar
Thomas, R. J. and Boag, B. ( 1972). Epidemiological studies on gastro-intestinal nematode parasites of sheep. Infection patterns on clean and summer-contaminated pasture. Research in Veterinary Science 13, 61–69.Google Scholar
Woolaston, R. R. and Windon, R. G. ( 2001). Selection of sheep for response to Trichostrongylus colubriformis larvae: genetic parameters. Animal Science 73, 41–48.CrossRefGoogle Scholar