Institute of Tropical Medicine Antwerp
Foundation of Public Utility

Validation of the FAMACHA((c)) eye colour chart using sensitivity/specificity analysis on two South African sheep farms

DSpace/Manakin Repository

Show simple item record

dc.contributor.author Reynecke, D. P.
dc.contributor.author van Wyk, J. A.
dc.contributor.author Gummow, B.
dc.contributor.author Dorny, P.
dc.contributor.author Boomker, J.
dc.date.accessioned 2011-04-29T12:56:46Z
dc.date.available 2011-04-29T12:56:46Z
dc.date.issued 2011
dc.identifier.issn 0304-4017
dc.identifier.doi http://dx.doi.org/10.1016/j.vetpar.2009.08.023
dc.identifier.other ITG-A4A
dc.identifier.other ANIMAL
dc.identifier.other U-VHELM
dc.identifier.other JIF
dc.identifier.other DOI
dc.identifier.other Abstract
dc.identifier.other UPD33
dc.identifier.uri http://hdl.handle.net/10390/6560
dc.description.abstract A validation study of the FAMACHA((c)) system for clinical evaluation of anaemia due to Haemonchus contortus was conducted on two commercial sheep farms in the summer rainfall region of South Africa. In this region, the Haemonchus season lasts from October to April. On Farm 1 the system was tested over a period of five successive years in consecutive sets of young stud Merino replacement rams and ewes examined at intervals of 3-5 weeks over each Haemonchus season, under routine farming conditions. When FAMACHA((c)) scores of 3, 4, and 5 and haematocrit values of </=22%, </=19%, and </=15% were separately considered to be anaemic, sensitivity on Farm 1 ranged from a maximum of 83% for a haematocrit cut-off of </=15%, to 40% for a haematocrit cut-off of </=22%. Sensitivity increased to 93% when FAMACHA((c)) scores of 2, 3, 4, and 5 were considered anaemic at a cut-off value of </=19%, but the positive predictive value decreased to 0.43, indicating that many non-anaemic animals would be treated. The analysis indicated a high level of classification bias on Farm 1, with the animals consistently being classified one FAMACHA((c)) category lower (i.e. less anaemic) than reality. On Farm 2 the test was conducted over two successive years in yearling rams evaluated at weekly to fortnightly intervals during each worm season. Every ram judged to be in FAMACHA((c)) category 4 or 5 was bled for haematocrit determination, and it was only dewormed with effective anthelmintics if the haematocrit was 15% or lower. When FAMACHA((c)) scores of 3, 4, and 5 and haematocrit values of </=22% and </=19% were separately considered to be anaemic on Farm 2, sensitivity ranged from 64% for a haematocrit cut-off of </=22%, to 80% for a cut-off of </=19%. For identical haematocrit cut-off values and proportions of the sampled flock considered to be diseased as for Farm 1, sensitivity was always higher for Farm 2. On the other hand, further analysis of the data indicated that the magnitude of the error on Farm 1 was very consistent on average over the entire trial period. The results of this study indicate that (i) persons introduced to the system should not only be trained, but also be evaluated for accuracy of application; (ii) the sensitivity of the FAMACHA((c)) diagnostic system should ideally be evaluated at shorter intervals to avoid production losses due to failure to detect anaemic animals which may be at risk of death; (iii) that calibration of the FAMACHA((c)) scoring is essential per individual evaluator, and (iv) that animals should be examined at weekly intervals during periods of the highest worm challenge. en
dc.language English en
dc.subject Animal diseases en
dc.subject Haemonchosis en
dc.subject Haemonchus contortus en
dc.subject Anemia en
dc.subject Sheep en
dc.subject Hematocrit en
dc.subject Clinical examination en
dc.subject Diagnosis en
dc.subject Validation en
dc.subject Specificity en
dc.subject Sensitivity en
dc.subject Classification en
dc.subject Seasonality en
dc.subject Rainfall en
dc.subject Training en
dc.subject Application en
dc.subject Quality control en
dc.subject South Africa en
dc.subject Africa, Southern en
dc.title Validation of the FAMACHA((c)) eye colour chart using sensitivity/specificity analysis on two South African sheep farms en
dc.type Article en
dc.citation.issue 3-4 en
dc.citation.jtitle Veterinary Parasitology en
dc.citation.volume 177 en
dc.citation.pages 203-211 en
dc.identifier.pmid http://www.ncbi.nlm.nih.gov/pubmed/19775816
dc.citation.jabbreviation Vet Parasitol en


Files in this item

Files Size Format View

There are no files associated with this item.

This item appears in the following Collection(s)

Show simple item record