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Improperly cooked fish, carrying active metacercariae (MCs), can pose a significant risk for transmitting fish-borne zoonotic trematodes (FBZTs) to human consumers. This study aimed to enhance our understanding of FBZTs by conducting a comprehensive cross-sectional analysis involving various fish species, such as Nile tilapia (Oreochromis niloticus), African catfish (Clarias gariepinus), and red-belly tilapia (Tilapia zillii). These fish specimens were collected from distinct Egyptian governorates, specifically Giza, Kafr al-Shaykh, and Fayoum. The recovered flukes from experimentally infected domestic pigeons were identified as Prohemistomum vivax, Haplorchis pumilio, and Pygidiopsis genata based on morphological features. Furthermore, the identity of the retrieved adult flukes was confirmed using three species-specific primers for PCR amplification and sequencing analysis of the ITS rDNA region and have been deposited in GenBank with the following accession numbers: P. vivax (OR291421.1 and OR291422.1), P. genata (OP099561.1), and H. pumilio (OM439581.1-OP090510.1). Quantitative real-time PCR targeting the immunological genes Tumor Necrosis Factor-alpha (TNF-alpha) and Interleukin-1 (IL-1Β) was employed to compare the cellular immune response between infected with EMCs and uninfected O. niloticus. The results indicated a significant increase in TNF- and IL-1Β levels in FBZTs-infected vs un-infected fishes. Importantly, the presence of adult flukes and EMCs led to substantial histological alterations in both experimentally infected pigeons and naturally infected fish tissues. These changes included the necrosis of fish muscle bundles and a pronounced inflammatory reaction with muscular necrosis in the digestive tracts of experimentally infected pigeons., Competing Interests: Declaration of competing interest No competing interest in authors., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The study re-evaluated the status of encysted metacercariae (EMC) of Family Heterophyidae in fresh and brackish water fish in an endemic focus in Egypt, as well as to study their morphological pattern. Seasonal variation of EMC was matched with their prevalence and intensity in infected fish. The study covered a period of one year from first of April 2011 to end of March 2012. The total percent of infection in the examined fish was 71.9% and 42.6% for brackish and fresh water respectively. The highest prevalence of the recovered EMC in both sources of water was for Heterophyes heterophyes (57.9%), followed by Pygidiopsis genata (39.7%), other Heterophyes spp. (21.09%), Haplorchis pumilio (19.5%), Phagicola spp (19.5%) and Stictodora tridactyla (6.2%). The highest mean intensity of the recovered EMC in both sources of water was for Pygidiopsis genata (10.27±2.83), followed H. heterophyes (9.45±7.13), Haplorchis pumilio (1.76±2.03), Phagicola spp. (1.59±1.71), other Heterophyes spp. (0.82±0.99) and Stictodora tridactyla (0.48±0.92). By using ANOVA test, there was significant difference in sizes of EMC of Pyigidiopsis genata (P=0.04) and Phagicola spp. EMC (P=0.03) in comparison to corresponding ones in all fish species. By using Student T-test, there was significant higher size of Haplorchis pumilio EMC in Tilapia species in comparison to the corresponding one in Mugil species. Monthly variation showed that summer was the season with the highest prevalence and highest mean intensity of EMC in both brackish and fresh water fish. Also, undifferentiated EMC most properly of genus Centrocestus was demonstrated.

A total of 100 Tilapia fish samples were collected from brackish water (n = 50) and fresh water (n = 50) resources, Northern Egypt, and examined for heterophyid encysted metacercariae (EMC) during the period from August 2007 to July 2008. The overall prevalence of infection was 32%; 22% for brackish water fish and 42% for fresh water fish. Significant differences in parasite occurrence among body regions were found, with muscles of the tail and caudal third being highly affected (93.4%) followed by middle third (84.3%) and anterior third (75%), while the head region had the lowest infection (21.9%). The prevalence was highest in summer season (46.4%) followed by spring (37.5%) and autumn (27.3%), and was lowest in winter (15.4%). The prevalence of infection decreased as fish size increased. Adult heterophyids, Heterophyes heterophyes, Heterophyes aequalis, Pygidiopsis genata, Haplorchis yokogawai, and Ascocotyle (Phagicola) ascolonga were recovered from EMC-feed puppies. Eggs of heterophyid type were detected in 10 (13.3%) out of 75 human stool specimens from local residents. An association exists between being a female (odd ratio [OR] 1.59 and 95% confidence interval [CI] 0.42-6.04), a fisherman (OR 1.39 [95% CI 0.26-7.48]), a housewife (OR 1.24 [95% CI 0.29-6.28]), 15-45 years old (OR 2.22 [95% CI 0.58-8.53]), or aged 5-14 years (OR 1.29 [95% CI 0.30-5.58]) and heterophyid infection. Measures should be implemented to reduce the risk of transmission of heterophyids to human and fish-eating animals.

Factors affecting prevalence and site preferences of heterophyid metacercariae (MC) were investigated in this study. A total of 173 specimens of a freshwater fish, Tilapia zilli were collected during autumn 2008, winter 2009 and summer 2009, from Ismailia fresh water canal, Egypt. Results showed that the total prevalence of heterophyid MC was 95.37%. The heterophyid MC consisted of Haplorchis yokogawi (47.4%), Pygidiopsis genata (21.4%), and Phagicola ascolonga (93.64%). H. yokogawi MC was detected in striated muscles, P. ascolonga in liver and kidney while, P. genata was detected in muscles, liver and kidney. The aggregation indices showed that all MC were aggregated and the P. genata was the most highly aggregated followed by H. yokogawi and then P. ascolonga. Responses of the heterophyid MC to host sex, weight and season greatly varied according to species of MC. Different responses of interaction for heterophyid MC intensity were found by GLIM analysis and this variation dependant on the type of infection (single or mixed infections). Factors affecting site preference of heterophid MC infection were discussed and further studies in other locations are required to examine the factors affecting site preference.

Encysted metacercariae (EMC) from seven trematod-zoonotic parasites were exposed to different temperature mechanisms. Boiling of the infected fishes was sufficient to kill the EMC, frying of fishes for five minutes was quite sufficient to inhibit the viability of EMC, but frying for 10 minutes killed all EMC. Grilling of infected Tilapia zillii was sufficient to kill EMC after 10 minutes; however five minutes were sufficient only to kill EMC in Clarias gariepinus. Regarding chilling at 5 degrees C, T. zillii EMC showed variation in response. Complete loss of viability of Prohemistomatidae EMC was achieved after 14 days, for Haplorchidae after 11 days, for Diplostomatidae after 12 days, while Clinostomatidae EMC required 15 days. For Cl. gariepinus, Bagrus bajad and Chrysichthys auratus achieved results were similar to those for T. zillii but with fewer days of withstanding chilling. The EMC infecting Tilapia lost their viability by freezing at -5 degrees C & -10 degrees k for Prohemistomatidae after 48 & 40 hours, for Diplostomatidae after 24 & 16 hours and for Clinostomatidae cysts after 48 &32 hours respectively. In infected Clarias gariepinus, Bagrus bajad and Chrysichthys auratus the EMC lost their viability by fireezing at -5 degrees C & -10 degrees C for periods shorter than those of Tilapia sp.

A total of 410 Tilapia zillii, 70 Clarias gariepinus, 30 Bagrus bajad and 15 Chlrysichthys auratus fishes were collected from different water bodies in Qualyobia Governorate. Microscopic examination of samples showed infection in muscles and head region (gills & branchial cavity) with encysted metacercariae in 91.7% of T. zillii, 82.85% of Cl. gariepinus, 70% of B. bajad and 86.66% of Ch. auratus. The highest distribution of metacercarial infection among the T. zillii was in the muscles of posterior third and tail followed by the middle third, anterior third and head region (gills & branchial cavity) while the highest distribution of metacercarial infection among Cl. gariepinus was in the middle third muscles followed by the posterior third, anterior third and lastly in the head region. The highest metacercarial infection among B. bajad and Ch. auratus fish was in the posterior third muscles and branchial cavity respectively. The taxonomic morphology of the encysted metacercariae and the excysted ones was given

The infection status with heterophyids in the second intermediate host fish obtained from brackish and fresh water resources in Dakahlia governorate, northern Egypt was investigated. Encysted metacercariae (EMC) in the fish species Mugil cephalus, Mugil capito, Mugil auratus, Tilapia nilotica, and Tilapia zilli from brackish water and T. nilotica and T. zilli from fresh water were isolated by artificial digestion method and identified by microscopic examination. Morphometric analysis of EMC isolated from these fishes identified seven phenotypically distinct groups. No significant morphologic differences were detected between EMC of the same group obtained from different fish species. The adult flukes recovered from seven groups of puppies separately infected with distinct EMC groups were compatible with seven species belong to six genera of Heterophyidae namely Heterophyes heterophyes, Heterophyes aequalis, Pygidiopsis genata, Haplorchis yokogawi, Prohemostomum vivax, Phagicola ascolonga, and Stictodora tridactyla. EMC of these seven heterophyid species were detected in all examined brackish water fishes. On the other hand, only EMC of P. genata, H. yokogawi, and P. ascolonga were detected in fresh water fishes, T. nilotica and T. zilli. These results indicate that heterophyid infections occur in brackish and fresh water fishes in northern Egypt, where the parasites are indigenous.

Obviously, the present study reports the coccidian parasite so-called Goussia cichlidarum for the first time in Egypt. Altogether, 25 exogenous stages were clearly distinguished from specimens of naturally infected fishes of Oreochromis niloticus, O. auraeus, and Tilapia zillii from different locations. The total prevalence of infection was about 41%. Mostly, infected fish grossly seemed with a healthy body, although severe lesions have been detected microscopically in massive infection. Portions of thick wall swim bladder have been placed in vitro. The released parasitic stages have been photographed, sketched, measured, described, and compared with previously described species. Oocysts, sporocysts, and sporozoites have also been differentiated morphologically and morphometrically. Maturity stages of sporozoites containing sporocysts within either an oocyst or those released and sporulated outside the oocyst were considerably discernible. In addition, endogenous stages have also been investigated in histological sections included gamonts, merozoites, oocysts, and different stages of sporozoites.

The encysted metacercariae (EMC) of heterophyids in the fish species; Mugil caphalus, M. capito, M. auratus, Oreochromis n. niloticus (=Tilapia nilotica), and Tilapia zillii trapped brackish and fresh water fishes were isolated by the artificial digestion method and identified. The EMC by morphometric analysis proved to be seven phenotypical distinct types. Cross-matched seven groups of clean laboratory bred puppies each was experimentally infected with a distinct EMC type. The recovered adult flukes were compatible to seven species of six genera of family Heterophyidae. These were Heterophyes heterophyes, H. aequalis, Pygidiopsis genata, Haplorchis yokogawai, Prohemostomumn vivax, Phagicola sp. and Stictodora sp. The EMC of the seven heterophyids were recovered from all the brackish water fishes, M. caphalus, M. capito, M. auratus, O. niloticus and T. zillii. On the other hand, the EMC of P. genata, Haplorchis yokogawai and Phagicola sp. were recovered only from the fresh water fish, O. niloticus and T. zillii. All the EMC was re-described and photographed.

Seven new cases of intestinal capillariasis were detected in Kasr El-Aini University Hospitals, Cairo, during the period from July 1997 to June 1998. A parasitological study concerning the morphological features of Capillaria philippinensis recovered from the stool of Egyptian cases was carried out. Eggs were separated, cultured and used to infect Oreochromis nilotica niloticus, a famous popularly consumed type of fresh water fish in Egypt in a trial for identification of the fish intermediate host for this parasite, but infection had not developed in the intestine of this species of fish.