Anti-complement and anticoagulant activities from the salivary glands and gut of Ctenocephalides felis felis (Siphonaptera: Pulicidae) in wild and domestic Carnivora hosts.

Ctenocephalides felis felis is an ectoparasite of global relevance, causing impacts at the One Health interface. The process of hematophagy depends on evolutionary adaptations, in which arthropods have evolved inhibitors of host hemostatic and immunological responses, mediated by salivary and intestinal molecules. However, fleas remain among the least studied hematophagous arthropod taxa, with their salivary and intestinal antihemostatic and immunomodulatory mechanisms still largely unknown. The present study aimed to investigate the interactions of the salivary glands and intestine of C. felis felis with blood coagulation and the classical and alternative pathways of the complement system in three natural hosts: the maned wolf (Chrysocyon brachyurus), dog (Canis familiaris), and cat (Felis catus). Salivary gland extracts (SGE) and intestinal extracts (IE) were obtained from dissected C. felis felis, and coagulation and hemolytic assays were quantified by measuring absorbance using an ELISA plate reader. The results showed that SGEs exhibited anticoagulant activity, prolonging coagulation time by 53% in dogs, 35.5% in maned wolves, and 37% in cats, whereas IEs had no significant effect. In contrast, IEs demonstrated the ability to inhibit the classical pathway, while SGEs showed no detectable anticomplement activity. IEs inhibition reached 63.7 ± 5.8% for dogs, 30.3 ± 12.1% for maned wolves, and 20.7 ± 1.5% for cats. None of the evaluated samples affected the alternative pathway of the complement system. These findings contribute to the understanding of parasite-host interactions and fill previously unexplored knowledge gaps regarding this insect.