Investigating anthelmintic efficacy against gastrointestinal nematodes in cattle by considering appropriate probability distributions for faecal egg count data

Autor: Chris Robertson, Louise A. Kelly, I.A. Nanjiani, Mike Taylor, J.W. Love, H.E. Lester
Rok vydání: 2017
Předmět:
0301 basic medicine
Veterinary medicine
Nematoda
040301 veterinary sciences
Drug Resistance
Negative binomial distribution
Cattle Diseases
Biology
Sensitivity and Specificity
lcsh:Infectious and parasitic diseases
0403 veterinary science
Feces
03 medical and health sciences
Bayes' theorem
FECRT
Zero inflated distributions
medicine
Parasite Egg Count
Animals
SF
Computer Simulation
lcsh:RC109-216
Pharmacology (medical)
Anthelmintic
Nematode Infections
Anthelmintic resistance
Bootstrapping (statistics)
Probability
Anthelmintic efficacy
2. Zero hunger
Pharmacology
QH
Antinematodal Agents
Bayes Theorem
04 agricultural and veterinary sciences
Gold standard (test)
030108 mycology & parasitology
Confidence interval
3. Good health
Infectious Diseases
Invited Article
Cattle
Parasitology
Compound distributions
Arithmetic mean
medicine.drug
Zdroj: International Journal for Parasitology: Drugs and Drug Resistance, Vol 7, Iss 1, Pp 71-82 (2017)
International Journal for Parasitology: Drugs and Drug Resistance
ISSN: 2211-3207
DOI: 10.1016/j.ijpddr.2017.01.002
Popis: The Faecal Egg Count Reduction Test (FECRT) is the most widely used field-based method for estimating anthelmintic efficacy and as an indicator of the presence of anthelmintic resistant nematodes in cattle, despite never having been validated against the gold standard of controlled slaughter studies. The objectives of this study were to assess the normality of cattle faecal egg count (FEC) data and their transformed versions, since confidence intervals used to aid the interpretation of the FECRT, are derived from data assumed to be normally distributed, and violation of this assumption could potentially lead to the misclassification of anthelmintic efficacy. Further, probability distributions and associated parameters were evaluated to determine those most appropriate for representing cattle FEC data, which could be used to estimate percentage reductions and confidence limits. FEC data were analysed from 2175 cattle on 52 farms using a McMaster method at two different diagnostic sensitivities (30 and 15 eggs per gram (epg)) and a sensitive centrifugal flotation technique (SCFT) with a sensitivity of 1 epg. FEC data obtained from all egg count methods were found to be non-normal even upon transformation; therefore, it would be recommended that confidence or credible intervals be generated using either a Bootstrapping or Bayesian approach, respectively, since analyses using these frameworks do not necessarily require the assumption of normality. FEC data obtained using the SCFT method were best represented by distributions associated with the negative binomial and hence arithmetic means could be used in FECRT calculations. Where FEC data were obtained with less sensitive counting techniques (i.e. McMaster 30 or 15 epg), zero-inflated distributions and their associated central tendency were the most appropriate and would be recommended to use, i.e. the arithmetic group mean divided by the proportion of non-zero counts present; otherwise apparent anthelmintic efficacy could be misrepresented.
Graphical abstract Image 1
Highlights • Efficacy can be misrepresented if inappropriate central tendencies are used in calculations. • Sensitivity of counting technique used influences the distributions of best representation. • Confidence intervals assuming normality of data would not be recommended to use with FEC data.
Databáze: OpenAIRE
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