Yellow grub disease, caused by Clinostomum metacercaria, is an endemic zoonotic infection in freshwater fish, responsible for Halzoun syndrome transmitted through the consumption of raw infected fish. This study aimed to conduct a multidisciplinary investigation integrating detailed morphology, oxidative stress, immunology, and histopathology alteration to advance our understanding of Clinostomum infection. In this annual study, 400 Nile tilapia (Oreochromis niloticus) were collected from the Nile River at Al Bahr Al Aazam, Giza Governorate to assess Clinostomum infection prevalence. Of the examined fish, 160 individuals (40.0%) harboured larval Clinostomum infections. Clinostomum metacercariae were observed in various anatomical locations, with 135 fish (33.8%) in buccal cavities, 21 fish (5.25%) in gill chambers, and 4 fish (1.0%) on the skin. Infection intensity ranged from 2 to 12 cysts per fish, averaging 5 cysts, notably with skin infections characterized by a single cyst in each fish. Macroscopic encysted metacercariae were collected from buccal cavities, gills, and skin. Micro-morphology revealed distinct features in C. complanatum, including an elliptical oral sucker with collar-like rings and large sensory papilla-like structures, contrasting with the absence of these features in C. phalacrocoracis. Oxidative stress, assessed through malondialdehyde (MDA) and nitric oxide levels, revealed an elevation in MDA to 35.13 ± 6 nmol/g and nitric oxide to 25.80 ± 3.12 µmol/g in infected fish. In infected fish, MHC-I gene expression increased approximately 13-fold, MHC-II peaked at 19-fold, and IL-1β significantly upregulated by 17-fold, compared to control levels. Histopathology detailed associated lesions, such as cyst encapsulation and eosinophilic infiltration. Clinstomiasis and its impacts on fish hosts offer crucial insights to control this emerging fish-borne zoonotic disease, threatening wildlife, aquaculture, and human health.

Equine Piroplasmosis (EP) is an infectious disease caused by the hemoprotozoan parasites Theileria equi, Babesia caballi, and the recently identified species T. haneyi. Hereby, we used a multiplex PCR (mPCR) targeting the 18S rRNA gene of T. equi and B. caballi for the simultaneous detection of EP in Egyptian equids and examined the presence of T. haneyi infections in Egypt. Blood samples from 155 equids (79 horses and 76 donkeys) collected from different governorates of Egypt were examined by mPCR and PCR targeting T. hayeni. The mPCR method revealed a prevalence of T. equi of 20.3% in horses and of 13.1% in donkeys and a prevalence of B. caballi of 1.2% in horses. B. caballi was not detected in donkeys in the current study. The mPCR method also detected coinfections with both species (2.5% and 1.3% in horses and donkeys, respectively). Additionally, we report the presence of T. haneyi in Egypt for the first time in 53.1% of the horse and 38.1% of the donkey tested samples. Coinfection with T. haneyi and T. equi was found in 13.5% of the samples, while infection with the three EP species was found in 1.9% of the samples.

The Atlantic little tunny, Euthynnus alletteratus, is widely distributed in temperate and tropical waters of the Atlantic Ocean, Black and Mediterranean Seas. In this study, wild-caught little tunny from Egypt, were found to be naturally infected with trypanorhyncha metacestodes, and the overall prevalence rate of infection was 38.7%. The blastocysts were either loosely attached to the mesentery of infected fish, or firmly attached and deeply embedded within the hepatic parenchyma. These encysted plerocerci are identified as Callitetrarhynchus gracilis (Trypanorhyncha, Lacistorhynchidae) based on its morphological and molecular characterization. The morphological characteristics of C. gracilis including scolex shape; the bothridia groove; the presence of frontal glands; the length of post-larval (appendix); metabasal armature; the existence of 'Chainette' and satellite hooks of different size were studied and described by Light and Scanning electron microscope. The phylogenetic analysis of lsrDNA gene of plerocerci confirmed the identification of the species to be deeply embedded in genus Callitetrarhynchus. The histopathological examination revealed severe pathological changes in the affected organs, including necrosis, inflammatory reactions, fibrosis and migratory tracts of the parasitic larvae together with marked visceral organs adhesions. To the best of our knowledge, this is the first report describing the detection of C. gracilis in little tunny collected from the Abu Qir landing site in Alexandria, Egypt.

Yellow grub disease is caused by clinostomid metacercariae (CM) infecting freshwater fish and has a potential impact on human health by causing Halzoun disease. This study aimed to combine both molecular and immunological approaches to characterize CM naturally infecting Nile tilapia. Two hundred and fifty Nile tilapia, Oreochromis niloticus, were collected from Giza Governorate and screened for the presence of CM. Samples were collected from buccal cavities and blood of 20 highly infected fish (≥10 cysts/fish) under aseptic conditions. Partial sequencing of the ITS rRNA region was performed to identify and distinguish the causative agents from closely related species. The cellular immune response between infected and noninfected O. niloticus was investigated by quantitative real-time-PCR targeting tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). Results showed significant increases in the levels of both TNF-α and IL-1β ( ) in fish infected with Clinostomum phalacrocoracis when compared to those infected with Clinstomum complanatum and negative controls (3.6 ± 0.2). Furthermore, the assessment of the levels of lysozyme activity in infected fish sera showed high levels versus noninfected ones.