title: The carrier prevalence of severe combined immunodeficiency, lavender foal syndrome and cerebellar abiotrophy in Arabian horses in South Africa.
abstract: BACKGROUND
  The carrier prevalence of severe combined immunodeficiency (SCID), lavender foal syndrome (LFS) and cerebellar abiotrophy (CA) in Arabian foals in South Africa was determined in order to quantify the potential impact of these conditions locally. Furthermore, the carrier prevalence of SCID prior to and following the introduction of a genetic test was compared to evaluate the effect of testing in the population.
  
  
  OBJECTIVE
  To estimate the carrier prevalence of SCID, LFS and CA in registered purebred Arabians born in South Africa in the 2004/5 and 2009/10 foaling seasons and compare the changes in prevalence in these disorders between the 2 groups of foals.
  
  
  METHODS
  Cross-sectional survey.
  
  
  METHODS
  Samples were collected from individuals randomly selected from 2 populations of purebred Arabian foals born during the 2004/5 and 2009/10 foaling seasons. Genetic testing for SCID, LFS and CA was performed on DNA extracts using specific polymerase chain reactions, with the products being analysed using fragment analysis on a genetic analyser.
  
  
  RESULTS
  The carrier prevalence of LFS and CA for the 2009/10 season was 11.7% (95% confidence interval [CI] 7.6-17.0%) and 5.1% (95% CI 2.5-9.1%), respectively, with no statistically significant change in prevalence between the 2004/5 and 2009/10 foaling seasons. However, the carrier prevalence of SCID was found to have decreased significantly from 6.4% (95% CI 4.8-8.3%) in the 2004/5 foals to 3.4% (95% CI 2.2-5.1%) in the 2009/10 foals (P = 0.009).
  
  
  CONCLUSIONS
  The results of this study indicate that genetic screening of Arabian horses for SCID may have played a role in significantly reducing the carrier prevalence within the breeding population and thereby reducing the birth of clinically affected individuals. This study provides an indication of the positive effect of genetic screening for specific conditions in horses.
authors.affiliation: Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa.
authors.forename: C J
authors.initials: CJ
authors.lastname: Tarr
authors.forename: P N
authors.initials: PN
authors.lastname: Thompson
authors.forename: A J
authors.initials: AJ
authors.lastname: Guthrie
authors.forename: C K
authors.initials: CK
authors.lastname: Harper
mesh_terms: D000818:Animals; D020022:Genetic Predisposition to Disease; D006579:Heterozygote; D006734:Horse Diseases / Q000453:epidemiology / Q000235:genetics*; D006736:Horses; D008297:Male; D016511:Severe Combined Immunodeficiency / Q000453:epidemiology / Q000235:genetics / Q000662:veterinary*; D013019:South Africa / Q000453:epidemiology
keywords: Arabian; cerebellar abiotrophy; horse; lavender foal syndrome; prevalence; severe combined immunodeficiency