Molecular identification and plant-extract antifungal susceptibility of skin and gill mycoses in common carp (Cyprinus carpio) from Wasit Ponds, Iraq
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Fungal and fungus-like infections are important external diseases of freshwater fish, especially when skin and gill integrity are compromised and water quality is poor. This study investigated fungal and fungus-like pathogens associated with skin and gill lesions in common carp (Cyprinus carpio) and evaluated the in vitro antifungal activity of the ethanolic extracts of thyme (Thymus vulgaris), clove (Syzygium aromaticum), pomegranate peels (Punica granatum), and garlic (Allium sativum). During spring (March-April), 200 common carp from eight ponds in Wasit Governorate, Iraq, were clinically inspected. From 120 infected fish, 60 skin and 60 gill samples were collected. Isolates were examined using culture, morphology, molecular, and histopathological methods. Ethanolic extracts of thyme, clove, pomegranate peel, and garlic were tested by agar-well diffusion and MIC assays. Fungal or fungus-like growth was recovered from 55/120 specimens (45.8%). Skin samples showed a significantly higher positivity rate than gill samples (63.3% vs. 28.3%). Six taxa were identified: Saprolegnia parasitica, Aspergillus flavus, A. niger, Fusarium solani species complex, Penicillium chrysogenum, and Candida albicans. Histopathological examinations revealed epithelial erosion, inflammatory infiltrates, lamellar changes, and PAS-positive fungal- or oomycete-like elements, with more frequent tissue involvement in skin lesions. Thyme and clove extracts produced the largest inhibition zones and the lowest MIC values, followed by pomegranate peel extract, whereas garlic extract showed moderate activity. Integrating conventional mycology, ITS-based identification, histopathology, and antifungal testing improved diagnostic confidence. Thyme and clove extracts showed strong in vitro activity, but their aquaculture applications require standardized in vivo safety and efficacy evaluations.
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Abarenkov K., Zirk A., Piirmann T., Pohonen R., Ivanov F., Nilsson R.H., Koljalg U. (2024). The UNITE database for molecular identification and taxonomic communication of fungi. Nucleic Acids Research, 52(D1): D791-D797.
Ali F.F., Al-Taee S.K., Al-Jumaa Z.M. (2020). Isolation, molecular identification, and pathological lesions of Saprolegnia spp. isolated from common carp, Cyprinus carpio, in floating cages in Mosul, Iraq. Veterinary World, 13(12): 2759-2764.
Barac A., Kosmidis C., Alastruey-Izquierdo A., Lagrou K. (2024). Rethinking aspergillosis in the era of microbiota and mycobiota. Mycopathologia, 189: 37.
Centers for Disease Control and Prevention. (2024). Target genes, primer sets, and thermocycler settings for fungal DNA amplification. https://www.cdc.gov /fungal/hcp/laboratories/settings-for-dna-amplifica tion.html
Costa S., Lopes I., Proenca D.N. (2022). Saprolegniosis in amphibians: An integrated overview of a fungal-like disease. Journal of Fungi, 8(5): 537.
de la Bastide P.Y., Leung W.L., Hintz W.E., Robinson R.C. (2018). Assessment of intra-specific variability in Saprolegnia parasitica populations of aquaculture facilities in British Columbia, Canada. Diseases of Aquatic Organisms, 128: 235-245.
Erdei N., Szekeres A., Varga M., Szekeres M. (2023). New insights into the morphological diversity of Saprolegnia parasitica. Journal of Fungi, 9(10): 982.
Escobar A., Perez M., Romanelli G., Blustein G. (2020). Thymol bioactivity: A review focusing on practical applications. Arabian Journal of Chemistry, 13(12): 9243-9269.
Geremia N., Raiola A.M., Ghelardi E. (2024). What do we know about cryptic aspergillosis? Microorganisms, 12(5): 886.
Korkea-Aho T., Wiklund T., Engblom C., Vainikka A., Viljamaa-Dirks S. (2022). Detection and quantification of the oomycete Saprolegnia parasitica in aquaculture environments. Microorganisms, 10(11): 2186.
Kowalczyk A., Przychodna M., Sopata S., Bodalska A., Fecka I. (2020). Thymol and thyme essential oil: New insights into selected therapeutic applications. Molecules, 25(18): 4125.
Leontiev R., Hohaus N., Jacob C., Gruhlke M.C.H., Slusarenko A.J. (2018). A comparison of the antibacterial and antifungal activities of thiosulfinate analogues of allicin. Scientific Reports, 8: 6763.
Lindholm-Lehto P.C. (2024). Saprolegniosis in aquaculture and how to control it? Aquaculture, Fish and Fisheries, 4: e200.
Mostafa A.A.F., Al-Askar A.A., Yassin M.T., Almaary K.S., Sholkamy E.N., Bakri M.M. (2020). Anti-Saprolegnia potency of some plant extracts against Saprolegnia diclina, the causative agent of saprolegniasis. Saudi Journal of Biological Sciences, 27(6): 1482-1487.
Nakamoto M., Kunimura K., Suzuki J.I., Kodera Y. (2020). Antimicrobial properties of hydrophobic compounds in garlic: Allicin, vinyldithiin, ajoene and diallyl polysulfides. Experimental and Therapeutic Medicine, 19(2): 1550-1553.
Nilsson R.H., Larsson K.H., Taylor A.F.S., Bengtsson-Palme J., Jeppesen T.S., Schigel D., Kennedy P., Picard K., Glockner F.O., Tedersoo L., Saar I., Koljalg U., Abarenkov K. (2019). The UNITE database for molecular identification of fungi: Handling dark taxa and parallel taxonomic classifications. Nucleic Acids Research, 47(D1): D259-D264.
Pavic D., Levican A., Crnic A.P., Dieguez-Uribeondo J. (2022a). Tracing the oomycete pathogen Saprolegnia parasitica in freshwater systems by a highly specific and sensitive droplet digital PCR assay. Scientific Reports, 12: 11933.
Pavic D., Levican A., Crnic A.P., Dieguez-Uribeondo J. (2022b). Variations in the sporulation efficiency of pathogenic freshwater oomycetes. Microorganisms, 10(3): 520.
Pavic D., Mougin J., Joyce A., Dieguez-Uribeondo J. (2024). Characterization of bacterial communities on trout skin and eggs in relation to Saprolegnia parasitica infection status. Microorganisms, 12(8): 1733.
Shreves K.V., Saraiva M., Ruba T., Miller C., Scott M., McLaggan D., van West P. (2024). Specific phylotypes of Saprolegnia parasitica associated with Atlantic salmon farms. Journal of Fungi, 10(1): 57.
Singh J., Kaur K., Kumar P., Kumar S. (2023). Pomegranate peel phytochemistry, pharmacological properties, methods of extraction, and potential applications: A comprehensive review. Food Chemistry Advances, 3: 100413.
Thakuria D., Kataki S., Dutta H., Baruah A. (2022). Anti-oomycete activity of chlorhexidine gluconate against Saprolegnia infection in fish. Aquaculture, 557: 738315.
Torbati M., Arzanlou M., Sandoval-Denis M., Crous P.W. (2021). Fungicolous Fusarium species: Ecology, diversity, isolation and identification. Fungal Systematics and Evolution, 7: 1-24.
Torres-Martinez A., Somoza G.M., Miranda L.A. (2025). Pejerrey (Odontesthes bonariensis) under siege: Main infectious diseases affecting a freshwater fish resource. Animals, 15(1): 74.
Ulanowska M., Olas B. (2021). Biological properties and prospects for the application of eugenol: A review. International Journal of Molecular Sciences, 22(7): 3671.
Vu D., Groenewald M., de Vries M., Gehrmann T., Stielow B., Eberhardt U., Al-Hatmi A., Groenewald J.Z., Cardinali G., Houbraken J., Boekhout T., Crous P.W., Robert V., Verkley G.J.M. (2019). Large-scale generation and analysis of filamentous fungal DNA barcodes boosts coverage for kingdom Fungi. Studies in Mycology, 92: 135-154.
Wang Y., Wu H., Zhang X., Zhang J., Li W. (2022). Characterizing the mechanisms of metalaxyl, bronopol and fluconazole against Saprolegnia parasitica. Genes, 13(9): 1524.
White T.J., Bruns T., Lee S., Taylor J. (1990). Amplification and direct sequencing of fungal ribosomal RNA genes for phylogenetics. In: M.A. Innis, D.H. Gelfand, J.J. Sninsky, T.J. White (Eds.), PCR Protocols: A Guide to Methods and Applications. Academic Press. pp: 315-322.
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