Effect of ivermectin on the integument and dorsoventral muscles of the tick Argas (Persicargas) persicus (Oken) (Ixodoidea: Argasidae)

Light and transmission electron microscopy (TEM) revealed that integument of Argas persicus consisted of cuticle underlined with epidermal cells. Cuticle consisted of outer epicuticle and inner procuticle. Epicuticle is further subdivided into thin wax, thin electron dense cuticulin, and thick less electron dense protein epicuticle layers. The procuticle consisted of exo-, endo-, and subcuticle. The procuticle contained numerous pore canals emerged from epidermal cells. Dermal glands were scattered between epidermal cells. TEM showed that each muscle cell contained two types of myofilaments and numerous electron dense bodies. Cytoplasmic organelles are peripherally located and plasma lemma invaginated deeply forming sarcotubular system. Feeding resulted in marked increase in cytoplasmic organelles and secretions of both epidermal cells and dermal glands. It also led to stretching of myofilaments, proliferation of cytoplasmic organelles, and appearance of glycogen particles in muscle cells. Subcutaneous inoculation of ivermectin (IVM) at a dose of 400 μg/kg pigeon resulted in extensive alterations in the integument and muscle cells. Both exhibited intense vacuolation of the cytoplasm, damage of cytoplasmic organelles, and swelling of the nucleus. It also caused aggregation of pore canals in the procuticle, depletion of secretory vesicles in dermal gland cells, and destruction of myofilaments, dense bodies, and sarcotubular system in muscle cells. The results suggest that IVM probably binds to the neurotransmitters or the hormones involved in secretion processes of epidermal cells and dermal glands in the integument or those involved in contraction of dorsoventral muscles.