Article History: Microtetrameres spiralis is one of the common spirurid parasites recovered from the cattle egret "Ardeola ibis ibis". No data was available on its ultrastructural characteristics with scanning electron microscopy. Therefore, the present study aimed to investigate, in details, the characteristic features of M. spiralis in cattle egret using both the light and scanning electron microscopies. The results revealed that nine out of seventeen Ardeola ibis ibis (53%) were infected

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... M. spiralis. Female worms were deeply embedded in proventriculus wall; their bodies were twisted in longitudinal tight spiral forming 2-3 turns. Males move in lumen; sometimes they were lodged on lining. They have filiform cylindrical shape. Male possesses two unequal and dissimilar spicules. The buccal capsule is well-chitinized, thick-walled, flask-shaped in females, but tubular in males. The vulva lies at the posterior third of the body. Cuticle was sharp transverse annulated along whole length of the body without alae or spines. Each pseudolabium has inner and outer edges; the outer edge has wavy-shaped, triple swollen processes. The depressed part that located between the two edges of each pseudolabium contained three corrugated, flower-shaped processes. The anterior annulations are ridged and have numerous pointed triangular processes. A single raised corrugated papilla appeared. Buttonlike structures are distributed on longitudinal striations. An oval striated, papilla-shaped structure is elevated with coiled, rodshaped projection. The transverse annulations over the midportion of the female's body have wavy margins.