A new parasitic metacercaria from the land snail Monacha obstructa pfeiffer1842 with critical review on relevant metacercariae belonging to the genus Brachylaima Dujardin 1843.

Out of 328 specimens of the land snail Monacha obstructa, 105 (32%) were infected with a new metacercaria belonging to the genus Brachylaima Dujardin 1843. The present snail is considered as a new host for this parasite in Egypt. Morphological and morphometric patterns were elucidated. Number of recovered infective metacercariae ranged between 4-35 per kidney of snail host. Metacercariae inhabited only the kidney of infected snails. Total length of mature metacercariae ranged from 1800mu-2050mu (1940mu). The anterior extremity is dome shaped and ceca were highly expanded, undulating, and filled with masses of brown cells and renal tissues. Metacercariae were fully mature, unencyted and highly active. They were either roaming in pathways inside the kidney or firmly anchored to renal tissues via oral sucker. Oral sucker length/total body length is 1:8.5. The histopathological effects involved disintegration of renal lamellae and formation of numerous necrotic masses. Invading metacercariae faced no host resistance and they were surrounded by a parasitovorus vacuole as a mean of immune-evasion. SEM studies revealed that dorsal surface of ventral sucker area is covered with rows of minute spines, Oral suker also is provided with a median tongue-like shaped septum. The rest of integument is aspinose. A critical review for relevant metacercariae of genus Brachylaima is provided.