Background and Aim: Canine filariasis is caused by several species of filarial worms. The pathophysiological response to infection is mainly due to the filaria lifecycle. Laboratory detection methods to assess the pathological alterations characteristic of filariasis are needed urgently. Serum protein profiles and C-reactive protein (CRP) levels are used widely to diagnose several animal diseases. This study aimed to determine the serum protein profiles and CRP levels in dogs infected with Dirofilaria immitis or Brugia pahangi or both parasites.

Materials and Methods: Blood samples were collected from 980 dogs presenting at animal hospitals and veterinary clinics in Bangkok and its vicinity. The presence of microfilaria in samples was determined using a buffy coat smear and staining with Wright–Giemsa. The sheathed and unsheathed microfilaria species were identified by acid phosphatase staining. Forty positive samples were tested. The serum protein profiles were identified by agarose gel electrophoresis. The CRP concentration was measured using a fluorescent immunoassay.

Results: Albumin levels and albumin-to-globulin ratios were significantly lower, and total protein, β2 globulin, and γ globulin levels were significantly elevated in dogs infected with D. immitis and B. pahangi compared with reference values in normal dogs. The average CRP concentrations in dogs infected with D. immitis or B. pahangi were 69.9 and 12.9 mg/L, respectively.

Conclusion: The total protein and γ globulin levels increased in canine filariasis compared with the normal reference range. The CRP concentration in dogs infected with D. immitis was extremely high, whereas that in dog infected with B. pahangi was normal.

Keywords: Brugia pahangi, C-reactive protein, Dirofilaria immitis, dogs, serum protein.