Comparison of Haptoglobin Concentrations Between Microfilaremic and Amicrofilaremic Dogs Infected by Dirofilaria immitis

BACKGROUND: Dirofilariosis, a zoonotic disease caused by Dirofilaria immitis, is associated with cardiovascular damage and systemic inflammation in dogs. OBJECTIVES: This study aimed to present preliminary data on the evaluation of serum haptoglobin (Hp) concentration as a potential biomarker of inflammation in dogs naturally infected with D. immitis, with and without microfilaremia. METHODS: Thirty dogs were categorized into three groups: microfilaremic seropositives (G1, n = 10), amicrofilaremic seropositives (G2, n = 10), and negative controls (CG, n = 10). Serum Hp concentrations were measured using a colorimetric assay and analyzed via one-way ANOVA with Tukey's post-test. RESULTS: Median Hp levels were 10.0 mg/dL (G1), 9.1 mg/dL (G2), and 13.7 mg/dL (CG), with no significant differences among groups. Additionally, no significant correlation was found between microfilarial burden and Hp levels (p = 0.651). CONCLUSIONS: Despite D. immitis infection, Hp concentration did not provide evidence of an inflammatory response in G1 and G2. While previous studies reported decreased Hp in microfilaremic dogs, our findings did not confirm this trend. The seropositive dogs in this study did not show clinical signs, indicating they had relatively mild infections, which may at least in part explain these results. The small sample size and lack of other acute-phase protein assessments restrict the generalizability of our findings and, thus, this study provides limited information about acute phase response dynamics. Nevertheless, these preliminary results highlight the complexity of Hp behavior in D. immitis infection and emphasize the need for further research.