Serum concentrations of
immunoglobulin G (
IgG),
IgM, and
IgA were measured in 9 Cavalier King Charles Spaniels with
pneumonia caused by Pneumocystis sp that were examined at 4 veterinary surgeries in the United Kingdom (UK) between September 2001 and November 2002.
Pneumocystis pneumonia was confirmed in all dogs by visualization of the organism in bronchoalveolar lavage fluid or a transthoracic lung aspirate. Two dogs had a history of demodicosis.
Immunoglobulin concentrations also were measured in breed-and age-matched dogs sampled over the same period.
IgG concentrations were significantly (P = .000) lower in the affected dogs (median 3.2 mg/mL) than in the control dogs (median 8.5 mg/mL).
IgM concentrations were significantly (P = .002) higher in the affected dogs (median 1.95 mg/mL) than in the control dogs (median 1.12 mg/mL). One affected dog had no change in
IgG concentration more than 3 months after resolution of
infection or vaccination, but did have reduction in
IgM concentration after resolution of
infection and vaccination. Control dogs had low serum
IgG and
IgM concentrations, compared with the reference interval for all dogs. Lymphocyte count in blood was normal or high in 7 of 8 affected dogs. The results of this study suggest that there is a defect in immunity in Cavalier King Charles Spaniels that underlies the susceptibility of these dogs to
pneumocystosis. Further studies are indicated to elucidate the mechanisms behind the defect, the prevalence within the breed, and the potential mode of inheritance of the problem.