Vector-borne parasites Dirofilaria repens and Babesia canis: haematological indices and immune response profiles in naturally infected and co-infected dogs

Abstract text

Co-infections with Dirofilaria repens and Babesia canis are rarely reported in the literature and there is very limited knowledge of their impact on canine health. Central Poland is endemic for both parasites, posing a risk of co-infections in dogs.

Our aim was to determine the effect of co-infection on canine health. We also tested the hypothesis that infection with filariae would drive the host response towards Th2-type immunity. This in turn should result in a reduction of proinflammatory Th1-type responses that are crucial for the elimination of intracellular pathogens, such as B. canis.

To evaluate the impact of co-infection on canine health, four groups of dogs were examined: healthy dogs, dogs infected with B. canis, dogs infected with D. repens and co-infected dogs. Blood parameters indicative of anaemia, kidney and liver damage were analysed statistically. Expression levels of immune response genes were determined and compared by qPCR reaction, in order to determine the type of immune response in mono-infection and co-infection.

In dogs infected with D. repens, no major alterations in blood parameters were observed. Dogs infected with B. canis suffered from anaemia, kidney and liver insufficiency. Co-infected dogs showed milder alternation in blood biochemical parameters associated with liver (ALP activity) and kidney (serum urea and creatinine levels) dysfunction, compared to dogs infected only with B. canis. The expression of genes associated with cellular (Th1-mediated) (STAT4 and INF-γ), humoral (Th2-mediated) (STAT6, GATA3, SOCS3, IL-13) and regulatory IL-10 responses was quantified. All the tested factors, except INF-γ, were found to be expressed in dogs infected with D. repens. The expression of IL-13 was predominant in dogs infected with D. repens, and the expression of STAT6 and IL-10 predominated in dogs with co-infections.

In summary, with just a few exceptions, no major alterations were found in blood parameters in D. repens infected dogs, and these dogs predominantly expressed Th2-related factors. While some features of Th1, T-regulatory and Th2 responses were observed in co-infected dogs, the Th2-related response appeared to predominate in these animals, and values of biochemical parameters were closer to those of healthy dogs than those solely infected with B. canis, suggesting a milder course of babesiosis in these animals.

The study was funded by the National Science Centre (NCN) OPUS grant no. 2017/27/B/NZ6/01691