Simple Summary: Fresh water Nile tilapia can be infected by numerous parasites, which can
result in high mortality and significant economic losses. The early detection of parasites and the
improved control of the major risk factors related to infection are among the main approaches
for controlling infection. Limited information is available on fish parasites in Upper Egypt. The
present study examined the prevalence of parasitic infection among 300 fish samples collected
from different markets in Assiut Governorate, Upper Egypt, using a series of detection techniques,
including microscopic, parasitological, histopathological and morphometric methods. Moreover, the
associations of the demographic factors with the distribution of parasitic infection in Nile tilapia were
also investigated.
Abstract: Fish are a source of high-quality protein with low cholesterol, but they are susceptible to
parasitic infections, which have a significant impact on aquaculture, in addition to their zoonotic
potential. The present study estimated parasitic infections and evaluated the diversity of zoonotic
parasites in freshwater Nile tilapia (Oreochromis niloticus) in Assiut Governorate, Upper Egypt. A total
of 300 samples were randomly collected from the Assiut Governorate. These fish were examined for
both ectoparasites and endoparasites, followed by the experimental infection of mice with encysted
metacercariae (EMC) for the retrieval of the adult worms. The overall prevalence of the variable
parasites was 82% (246 of 300). Both ecto- and endoparasites were detected in 41% (123 of 300) of the
examined fish. The identified ectoparasites were Gyrodactylus, Dactylogrus, Cichlidogyrus, Trichodina
and Icthyophthirius multifiliis, in 5%, 4%, 22%, 6% and 4% of the fish, respectively. The endoparasites
were trematodes (Orientocreadium batrachoides 3%), nematodes (Contracaecum. 2%), acanthocephala
(Acanthosentis tilapiae 25%) and protozoa that included Isospora and Eimeria spp., in 1% and 8% of
fish, respectively. Myxobolus was detected in 2% of the examined fish. The overall prevalence of
encysted metacercariae (EMC) was 95% (285 of 300), while infection with macroscopic EMC had a
prevalence of 37% and microscopic EMC had a prevalence of 58%. The adult worms recovered fromthe experimental infections were Prohemistomum vivax and Mesostephanus spp., which belong to the
family Cyathocotylidae. Collectively, these findings reflect the relatively high occurrence of parasites
among the studied fish, confirming the necessity of strict measures to control infection

Keywords: Nile tilapia fish; ectoparasites; endoparasites; experimental infections; Upper Egyp