Background: Inadequate aeration is one of the most common environmental stressors affecting intensive aquaculture, leading to hypoxia-induced physiological disturbances that compromise fish health, welfare, and productivity. Despite the recognized tolerance of Nile tilapia (Oreochromis niloticus) to low dissolved oxygen, the integrated effects of different aeration regimes on tissue integrity, physiological responses, and oxidative stress remain insufficiently characterized. Aim: This study aimed to evaluate the effects of four aeration regimens on histopathological alterations in the gills and liver, together with behavioral, hematological, biochemical, and oxidative stress responses in Nile tilapia under controlled laboratory conditions. Methods: A total of 180 Nile tilapia were randomly assigned to four aeration treatments with three replicates per treatment for 10 days: continuous normal aeration (control), continuous reduced aeration, daily interrupted aeration, and intermittent periodic aeration. Water quality parameters, dissolved oxygen, growth performance, survival, behavioral responses, histopathological lesions (using a semi-quantitative histopathological alteration index), hematological variables, serum biochemical parameters, and oxidative stress biomarkers were evaluated. Results: The severity of physiological disturbances increased with the intensity of aeration reduction. Fish exposed to daily interrupted aeration exhibited the most pronounced adverse effects, whereas the continuously aerated control group showed the least tissue damage and physiological disturbance. Reduced aeration significantly impaired growth performance , survival and behavioral stress responses, and induced progressive histopathological lesions in the gills and liver. Biochemical analysis revealed marked elevations in liver enzyme activities, oxidative stress biomarkers, and glucose concentrations, whereas basic hematological variables exhibited comparatively minor changes. Total ammonia nitrogen and nitrite also increased significantly with aeration-treatment severity, indicating that the observed biological responses reflect the combined effects of reduced aeration and its associated water-quality consequences rather than oxygen depletion alone. Conclusion: The findings indicate that Nile tilapia responses to inadequate aeration were more closely associated with metabolic and antioxidant biochemical changes than with hematological adaptation, suggesting that compensatory metabolic and antioxidant mechanisms may play a larger role than hematological adjustment in this species\' response to hypoxic stress, although the present design does not establish this mechanistically. Repeated short-term episodes of inadequate aeration were associated with measurable organ damage and physiological dysfunction. These results provide practical guidance for aeration management in aquaculture and support the potential application of biochemical biomarkers as early indicators of stress associated with inadequate aeration. Because reduced aeration was accompanied by a parallel increase in ammonia and nitrite, the findings should be interpreted as reflecting the combined consequences of altered aeration and associated water-quality deterioration rather than dissolved oxygen depletion in isolation.
Background: Brucellosis is a neglected zoonosis endemic to sub-Saharan Africa, with poorly documented molecular epidemiology in Guinea. Aim: This study aimed to evaluate the diagnostic performance of two serological tests (Rose Bengal Plate Test [RBPT] and I-enzyme-linked immunosorbent assay [ELISA]) and identify Brucella species circulating in small ruminants using quantitative polymerase chain reaction (qPCR). Methods: A total of 270 serum samples collected from sheep (n = 132) and goats (n = 138) in the Mamou region were tested using the RBPT and I-ELISA. Genomic DNA was extracted from I-ELISA-positive cells and analyzed by qPCR targeting the IS711 gene. Samples with a cycle threshold value ≤35 were considered positive and further analyzed for species identification. Results: The overall seroprevalence was 14.81% (RBPT) and 10.74% (I-ELISA), with no significant difference between the 2 tests (P = 0.197). The seroprevalence was higher in goats (15.94% and 10.87% by RBPT and ELISA, respectively) than in sheep (13.64% and 10.61%), although the differences were not statistically significant (P > 0.05). Using I-ELISA as the reference test, RBPT showed a sensitivity of 96.55%, specificity of 94.61%, positive predictive value of 68.29%, negative predictive value of 99.56%, and area under the curve of 0.9558, reflecting excellent diagnostic concordance between the two tests. However, a false-positive rate of 5.4% was recorded for RBPT. For molecular confirmation, IS711 screening yielded an overall positivity of 55.17%, with 60.00% in goats and 50.00% in sheep. Species identification confirmed Brucella abortus in 81.25% of small ruminants (88.89 % in goats; 71.43 % in sheep). The 3 IS711-positive samples could not be confirmed as either of the targeted species. Abortion was the most strongly associated clinical sign, with 90% of cases confirmed by IS711 polymerase chain reaction and 88.88% identified as B. abortus. Conclusion: To the best of our knowledge, this study is the first to combine serological and molecular approaches for Brucella surveillance in small ruminants in Guinea. The exclusive circulation of B. abortus in the Mamou region. The combined RBPT and I-ELISA strategy offers a reliable, field-adapted approach for future surveillance of brucellosis in the country.
Background: Genetic studies have revealed several divergent Dirofilaria repens-like lineages in Asia. One of these, provisionally designated Dirofilaria sp. “Thailand II” was characterized from feline blood in southern Thailand, whereas two adult specimens from humans in Vietnam have subsequently been assigned to this lineage. Its vertebrate host range and epidemiological significance remain poorly defined. Aim: This study investigated a microfilaremic dog from northern Vietnam and evaluated the mitochondrial relationship of filarioid DNA detected in whole blood to published Dirofilaria sp. “Thailand II” reference sequences. Methods: Peripheral blood from a one-year-old female Vietnamese native dog was microscopically examined for microfilariae and tested for circulating Dirofilaria immitis antigen using SNAP® 4Dx® Plus. Mitochondrial 12S rRNA and cox1 fragments were amplified from whole-blood DNA, bidirectionally Sanger sequenced, compared with GenBank sequences by BLASTn, and analyzed using maximum-likelihood phylogenies. Results: Motile microfilariae were detected in peripheral blood, whereas D. immitis antigen was not detected. The 394-bp 12S rRNA sequence showed 99.74% BLASTn identity and 100% query coverage with Thailand II references KX265092 and KX265093. The Vietnamese sequence clustered with the Thailand II references, but the relevant lineage-level node was weakly supported (56% bootstrap). The 602-bp cox1 sequence showed 99.83% identity and 100% query coverage with MH823371 and MH823372, forming a strongly supported sister relationship with MH823371 (95% bootstrap); the broader grouping containing both Thailand II references received 76% support. Sequencing was performed from whole-blood DNA rather than individually isolated microfilariae; therefore, a direct morphology–genotype linkage cannot be demonstrated and mixed filarioid infection cannot be excluded. Conclusion: This study documents a microfilaremic dog from northern Vietnam in which whole-blood mitochondrial 12S rRNA and cox1 sequences show close affinity to the provisional Thailand II lineage. This host record broadens the lineage’s known context but does not establish formal species identity, prevalence, reservoir competence, or transmission dynamics. Individual-parasite sequencing, nuclear or genome-scale data, and larger host–vector surveys are required for definitive taxonomic and epidemiological interpretation.
Background: Anisakis spp. are important marine nematodes with ecological, economic, and public health significance due to their zoonotic potential and widespread occurrence in commercially important fish. Information regarding the occurrence and genetic characterization of Anisakis species in fish from the Timor Sea, Indonesia, remains limited. Aim: This study aimed to characterize Anisakis larvae infecting frigate tuna (Auxis thazard) and Indian mackerel (Rastrelliger kanagurta) using an integrated morphological and molecular approach. A total of 1,200 fish specimens (600 A. thazard and 600 R. kanagurta) were collected from 6 fish landing sites in East Nusa Tenggara Province, Indonesia, between May and October 2024. Methods: Recovered larvae were examined using scanning electron microscopy (SEM), and the mitochondrial cytochrome c oxidase subunit II (cox2) gene. Results: SEM observations revealed diagnostic features characteristic of third-stage (L3) Anisakis larvae, including a prominent ventral boring tooth, amphids adjacent to the mouth opening, transverse cuticular striations, and a terminal mucron. PCR amplification yielded a single cox2 fragment of approximately 629 bp from all 12 analyzed larvae. BLAST analysis demonstrated high sequence similarity (97.85%–99.68%) and 100% query coverage with reference sequences of A. typica. Phylogenetic reconstruction based on partial Cox2 sequences placed the 7 sequenced isolates within the A. typica lineage and separated them from reference sequences of A. simplex, with strong bootstrap support. One isolate (T41) occupied a relatively distinct position within the A. typica clade; however, this observation was insufficient to establish intraspecific genetic variation at the population level. Conclusion: The combined morphological and molecular findings supported the identification of A. typica among the 7 sequenced larvae recovered from A. thazard and R. kanagurta. This finding demonstrates the occurrence of A. typica among the analyzed isolates but does not establish it as the predominant Anisakis species in the Timor Sea. The findings provide valuable baseline data for assessing fish parasitology, marine biodiversity, seafood safety, and the assessment of potential zoonotic exposure in Indonesian waters.
Background: Avian pathogenic Escherichia coli (APEC) causes colibacillosis, leading to significant economic losses in poultry flocks due to high mortality rates, decreased feed conversion efficiency, increased treatment costs, and public health risks resulting from multidrug resistance and the potential transmission of resistance to humans. Aim: This study aimed to detect virulence genes in E. coli isolates, assess their antibiotic susceptibility, and identify resistance genes blaTEM and mcr1. Methods: Fifty-six samples were collected from birds suspected of having colibacillosis. Isolation and identification were performed based on morphological, staining, and biochemical characteristics. Antibiotic susceptibility testing was done using the disk diffusion method. Virulence genes (ompT, iroN, hlyF, iss, iutA) and antibiotic resistance genes were detected by molecular methods. Results: Fifty isolates (89.28%) were confirmed as E. coli. All isolates showed multidrug resistance. The prevalence of virulence genes was ompT (94%), hlyF (90%), iss (92%), iroN (86%), and iutA (66%). Resistance genes blaTEM and mcr1 were detected in 32% and 20% of isolates, respectively. Conclusion: This study confirms the prevalence of highly virulent and multidrug-resistant APEC strains in Syrian poultry, necessitating urgent rationalization of antibiotic use and enhanced biosecurity measures.
