Increased parasite resistance and recurrent airway obstruction in horses of a high-prevalence family.
BACKGROUND
Equine recurrent airway obstruction (RAO) shares many characteristics with human asthma. In humans, an inverse relationship between susceptibility to asthma and resistance to parasites is suspected.


OBJECTIVE
Members of a high-incidence RAO half-sibling family (F) shed fewer strongylid eggs compared with RAO-unaffected pasture mates (PM) and that RAO-affected horses shed fewer eggs than RAO-unaffected half-siblings.


METHODS
Seventy-three F and 73 unrelated, age matched PM.


METHODS
Cases and controls kept under the same management and deworming regime were examined. Each individual was classified as RAO affected or RAO unaffected and fecal samples were collected before and 1-3 weeks and 3 months after deworming. Samples were analyzed by combined sedimentation-flotation and modified McMaster methods and classified into 3 categories of 0 eggs per gram of feces (EpG), 1-100 EpG, and > 100 EpG, respectively.


RESULTS
PM compared with RAO-affected F had a 16.7 (95% confidence interval [CI]: 2.0-136.3) times higher risk for shedding > 100 EpG compared with 0 EpG and a 5.3 (95% CI: 1.0-27.4) times higher risk for shedding > 100 EpG compared with 0 EpG. There was no significant effect when RAO-unaffected F were compared with their PM. RAO-unaffected compared with RAO-affected offspring had a 5.8 (95% CI: 0.0-1.0) times higher risk for shedding 1-100 EpG. Age, sex, breed, and sharing pastures with other species had no significant confounding effects.


CONCLUSIONS
RAO is associated with resistance against strongylid parasites in a high-prevalence family.
Neuhaus
S
S
Equine Clinic, Department of Clinical Veterinary Medicine, Vetsuisse Faculty, University of Berne, Länggass-str. 124, CH-3012 Berne, Switzerland.
Bruendler
P
P
Frey
C F
CF
Gottstein
B
B
Doherr
M G
MG
Gerber
V
V
D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use; D005243:Feces / Q000469:parasitology; D005260:Female; D020022:Genetic Predisposition to Disease; D006734:Horse Diseases / Q000188:drug therapy / Q000235:genetics / Q000276:immunology*; D006736:Horses; D016015:Logistic Models; D008173:Lung Diseases, Obstructive / Q000235:genetics / Q000276:immunology / Q000662:veterinary*; D008297:Male; D010270:Parasite Egg Count / Q000662:veterinary; D015995:Prevalence; D017183:Strongylida / Q000302:isolation & purification; D017206:Strongylida Infections / Q000188:drug therapy / Q000235:genetics / Q000276:immunology / Q000662:veterinary*
D000871:Anthelmintics