Transfer of naturally acquired specific passive immunity against Anaplasma phagocytophilum in foals in Southeastern Pennsylvania and Northern Maryland

Autor: Emily K. Rule, Ashley G. Boyle, Darko Stefanovski, Eman Anis, Jennifer Linton, Olivia Lorello
Jazyk: angličtina
Rok vydání: 2023
Předmět:
Zdroj: Journal of Veterinary Internal Medicine, Vol 37, Iss 5, Pp 1889-1892 (2023)
Druh dokumentu: article
ISSN: 1939-1676
0891-6640
DOI: 10.1111/jvim.16812
Popis: Abstract Background Equine granulocytic anaplasmosis (EGA) is a common disease in adult horses, but clinical disease in foals is rarely reported. The relationship between equine maternal and neonatal antibodies to Anaplasma phagocytophilum is unclear. Hypothesis/Objectives That mares in an endemic region would be seropositive for A. phagocytophilum and that mare and foal serum IgG concentrations for A. phagocytophilum would correlate. Additionally, we hypothesized that foal IgG concentrations for A. phagocytophilum acquired by passive immunity would decline by 6 months of age. Animals Twenty‐two healthy mare‐foal pairs. Methods This prospective observational study investigated serum IgG concentrations specific for A. phagocytophilum in mares and foals using an immunofluorescent antibody test (IFA). The association between foal titer (as a binary variable) and age in months was assessed using a mixed‐effects logistic regression. Results A positive correlation between newborn foal antibody titers and mare titers was identified at both the pre‐foaling (τa = 0.38, τb = 0.50, P = .009) and foaling timepoints (τa = 0.36, τb = 0.47, P = .01). In A. phagocytophilum seropositive neonates, it was unlikely that a positive titer would be detected by 3 months of age (OR = 0.002, P = .02, 95% CI: 0.00001‐0.38). Three out of 20 foals seroconverted between 3 and 6 months of age. Conclusions and Clinical Importance Transfer of specific passive immunity to A. phagocytophilum occurred in 80% of foals born to seropositive mares and declined by 3 months of age. A. phagocytophilum infection should be considered in foals displaying clinical signs consistent with EGA.
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