Acute-phase response in Babesia canis and Dirofilaria immitis co-infections in dogs

- Asymptomatic D. immitis infection does not aggravate acute-phase response in acute B. canis infection.
- Asymptomatic D. immitis and acute B. canis co-infections increase haemolysis, dehydration and antibody production.
- Asymptomatic D. immitis and acute B. canis co-infections do not increase SAA concentration.

Babesia canis and Dirofilaria immitis are emerging and geographically overlapping vector-borne pathogens in dogs. Infection with B. canis leads to acute-phase response (APR) that can be mild to severe and results in either non-complicated or complicated forms of the disease. The aim of this study was to determine whether acute B. canis infection is more severe in dogs with underlying asymptomatic D. immitis infection. Dogs of both sexes, different ages and breeds, with naturally occurring mono-infections with B. canis (n = 13) and D. immitis (n = 18) and co-infected dogs (n = 7) were enrolled as well as healthy controls (n = 15). Routine haematology and biochemistry, agarose gel electrophoresis (agEF) protein fraction separation and enzyme-linked immunosorbent assay (ELISA) for serum amyloid A (SAA) were performed. Based on clinical and laboratory findings, sepsis was diagnosed in the majority of dogs with acute B. canis infection with or without underlying asymptomatic D. immitis infection. Overall, haematology, biochemistry and agEF pattern changes were induced and dictated by acute B. canis infection whether or not the dogs had an asymptomatic D. immitis infection. D. immitis infection slightly influenced the level of anaemia, slightly aggravated the level of dehydration and increased the concentration of γ-globulins in acute-phase B. canis infection. D. immitis infection prevented B. canis-induced leukopenia. SAA equally increased in dogs with acute B. canis infection with or without underlying D. immitis infection. The level of SAA was not changed in dogs with asymptomatic D. immitis when compared to the controls. In conclusion, asymptomatic D. immitis infection does not influence overall APR after acute B. canis infection.