Morphological characterization and histopathological alterations of homologs Heterophyid metacercarial coinfection in farmed mullets and experimental infected pigeons

Abstract

In this study, samples of farmed thin-lipped mullets, Mugil capito from Lake Manzala and wild-caught grey mullet Mugil cephalus from Alexandria were found to be infected with heterophyid encysted metacercariae (EMC), and the overall prevalence rates were 80 and 100%, respectively. The number of metacercarial infection in tail tissue was significantly higher than that recovered from trunk and head among M. capito and M. cephalus. M. capito were simultaneously infected with two morphologically different EMC that ascribed to Heterophyes and Pygidiopsis species, while M. cephalus were infected with EMC of Heterophyes species. The experimental infection of domestic pigeons (Columba livia domestica) with the recovered encysted metacercariae confirmed the successful development of two types of Heterophyid flukes: identified as Heterophyes heterophyes and Pygidiopsis genata in the small intestine of pigeons. The histopathological examination revealed that Heterophyes cyst was small, elliptical with thick wall and predominating between cardiac muscle fibres and in the lumen of atrioventricular region of the heart. Pygidiopsis species cyst appeared larger in size, rounded with thin cyst wall and prominent internal structure. Pygidiopsis species were few in the abdominal fat and prominently encysted in the internal visceral organs including wall of the stomach, kidneys and muscular tissue away. They were also deeply encysted in testes and ovaries. Interestingly, the adult flukes were demonstrated in the intestinal lumen of the experimentally infected pigeons but with minor histopathological alterations. Our findings suggest that the heterophyids EMCs in mullets have genera-specific morphological characters and may induce histopathological changes in surrounding host-associated tissues.