The application of faecal egg count results and statistical inference for clinical decision making in foals

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Abstract

This study investigated the impact of variability in Parascaris spp. and strongyle faecal egg counts (FEC)from foals on treatment decision-making and detection of a patent infection. A single faecal sample was collected once daily for three days from 53 foals and a FEC was performed on three separate portions of each sample (total of nine egg counts per foal). Differences in the decision to administer an anthelmintic using the results of a single count (C 1 ), the mean of three (X¯ 1–3 )or nine counts (X¯ 1–9 )and the upper 5% confidence limit of the gamma confidence interval (CI)of the estimate of the distribution mean (μ)from three (UCL 1–3 )and nine counts (UCL 1–9 )were determined for a range of egg count thresholds. The UCL 1–9 was used as the best estimate of μ, hypothesis testing for treatment and the comparison of treatment decision-making using C 1 , X¯ 1–3 , X¯ 1–9 and UCL 1–3 . The results of this study demonstrated that a point estimate (C 1 or X¯ 1–3 )was of limited value for estimating the distribution mean of egg counts in faeces and there was overall poor agreement in treatment decision-making for individual foals using C 1 compared with UCL 1–9 . Of the foals with C 1 of zero eggs per gram, 54% and 47% had Parascaris and strongyle eggs in subsequent counts, respectively. The egg density in faeces is inhomogeneous, resulting in considerable variability in egg count results for an individual foal: between faecal piles, different portions of a faecal pile and days. The use of the negative binomial distribution CI for μ takes this variability into account and is recommended for use when interpreting FEC data from horses.

Original languageEnglish
Pages (from-to)7-12
Number of pages6
JournalVeterinary Parasitology
Volume270
DOIs
Publication statusPublished - 01 Jun 2019

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fecal egg count
foals
Ovum
decision making
Parascaris
Strongylidae
Ascaridoidea
Decision Making
confidence interval
feces
Feces
Eggs
Binomial Distribution
patents
Confidence Intervals
anthelmintics
Anthelmintics
Clinical Decision-Making
Horses
horses

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title = "The application of faecal egg count results and statistical inference for clinical decision making in foals",
abstract = "This study investigated the impact of variability in Parascaris spp. and strongyle faecal egg counts (FEC)from foals on treatment decision-making and detection of a patent infection. A single faecal sample was collected once daily for three days from 53 foals and a FEC was performed on three separate portions of each sample (total of nine egg counts per foal). Differences in the decision to administer an anthelmintic using the results of a single count (C 1 ), the mean of three (X¯ 1–3 )or nine counts (X¯ 1–9 )and the upper 5{\%} confidence limit of the gamma confidence interval (CI)of the estimate of the distribution mean (μ)from three (UCL 1–3 )and nine counts (UCL 1–9 )were determined for a range of egg count thresholds. The UCL 1–9 was used as the best estimate of μ, hypothesis testing for treatment and the comparison of treatment decision-making using C 1 , X¯ 1–3 , X¯ 1–9 and UCL 1–3 . The results of this study demonstrated that a point estimate (C 1 or X¯ 1–3 )was of limited value for estimating the distribution mean of egg counts in faeces and there was overall poor agreement in treatment decision-making for individual foals using C 1 compared with UCL 1–9 . Of the foals with C 1 of zero eggs per gram, 54{\%} and 47{\%} had Parascaris and strongyle eggs in subsequent counts, respectively. The egg density in faeces is inhomogeneous, resulting in considerable variability in egg count results for an individual foal: between faecal piles, different portions of a faecal pile and days. The use of the negative binomial distribution CI for μ takes this variability into account and is recommended for use when interpreting FEC data from horses.",
keywords = "Ascarid, Cyathostomins, Horse, McMaster, Parascaris",
author = "Wilkes, {E. J.A.} and Woodgate, {R. G.} and Raidal, {S. L.} and Hughes, {K. J.}",
year = "2019",
month = "6",
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doi = "10.1016/j.vetpar.2019.04.010",
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T1 - The application of faecal egg count results and statistical inference for clinical decision making in foals

AU - Wilkes, E. J.A.

AU - Woodgate, R. G.

AU - Raidal, S. L.

AU - Hughes, K. J.

PY - 2019/6/1

Y1 - 2019/6/1

N2 - This study investigated the impact of variability in Parascaris spp. and strongyle faecal egg counts (FEC)from foals on treatment decision-making and detection of a patent infection. A single faecal sample was collected once daily for three days from 53 foals and a FEC was performed on three separate portions of each sample (total of nine egg counts per foal). Differences in the decision to administer an anthelmintic using the results of a single count (C 1 ), the mean of three (X¯ 1–3 )or nine counts (X¯ 1–9 )and the upper 5% confidence limit of the gamma confidence interval (CI)of the estimate of the distribution mean (μ)from three (UCL 1–3 )and nine counts (UCL 1–9 )were determined for a range of egg count thresholds. The UCL 1–9 was used as the best estimate of μ, hypothesis testing for treatment and the comparison of treatment decision-making using C 1 , X¯ 1–3 , X¯ 1–9 and UCL 1–3 . The results of this study demonstrated that a point estimate (C 1 or X¯ 1–3 )was of limited value for estimating the distribution mean of egg counts in faeces and there was overall poor agreement in treatment decision-making for individual foals using C 1 compared with UCL 1–9 . Of the foals with C 1 of zero eggs per gram, 54% and 47% had Parascaris and strongyle eggs in subsequent counts, respectively. The egg density in faeces is inhomogeneous, resulting in considerable variability in egg count results for an individual foal: between faecal piles, different portions of a faecal pile and days. The use of the negative binomial distribution CI for μ takes this variability into account and is recommended for use when interpreting FEC data from horses.

AB - This study investigated the impact of variability in Parascaris spp. and strongyle faecal egg counts (FEC)from foals on treatment decision-making and detection of a patent infection. A single faecal sample was collected once daily for three days from 53 foals and a FEC was performed on three separate portions of each sample (total of nine egg counts per foal). Differences in the decision to administer an anthelmintic using the results of a single count (C 1 ), the mean of three (X¯ 1–3 )or nine counts (X¯ 1–9 )and the upper 5% confidence limit of the gamma confidence interval (CI)of the estimate of the distribution mean (μ)from three (UCL 1–3 )and nine counts (UCL 1–9 )were determined for a range of egg count thresholds. The UCL 1–9 was used as the best estimate of μ, hypothesis testing for treatment and the comparison of treatment decision-making using C 1 , X¯ 1–3 , X¯ 1–9 and UCL 1–3 . The results of this study demonstrated that a point estimate (C 1 or X¯ 1–3 )was of limited value for estimating the distribution mean of egg counts in faeces and there was overall poor agreement in treatment decision-making for individual foals using C 1 compared with UCL 1–9 . Of the foals with C 1 of zero eggs per gram, 54% and 47% had Parascaris and strongyle eggs in subsequent counts, respectively. The egg density in faeces is inhomogeneous, resulting in considerable variability in egg count results for an individual foal: between faecal piles, different portions of a faecal pile and days. The use of the negative binomial distribution CI for μ takes this variability into account and is recommended for use when interpreting FEC data from horses.

KW - Ascarid

KW - Cyathostomins

KW - Horse

KW - McMaster

KW - Parascaris

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U2 - 10.1016/j.vetpar.2019.04.010

DO - 10.1016/j.vetpar.2019.04.010

M3 - Article

VL - 270

SP - 7

EP - 12

JO - Veterinary Parasitology

JF - Veterinary Parasitology

SN - 0304-4017

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