Cryopreservation and Vitality Assessment of GI Nematode Larvae in Libyan Sheep (Ovis aries) Using Liquid Nitrogen

Background and Objective: Parasitic infections, particularly gastrointestinal (GI) nematodes, significantly impact livestock health and productivity. Cryopreservation offers a practical solution for long-term storage and study of parasitic larvae. This study aimed to evaluate the viability of cryopreserved GI nematode larvae from Libyan sheep (Ovis aries) using different cryoprotective solutions and to assess the effectiveness of vital dye exclusion for post-thaw viability determination. Materials and Methods: The GI nematode larvae were isolated and cryopreserved in liquid nitrogen using three solutions: distilled water, 1% ethylene glycol, and 1% acetic acid. After thawing, larval viability was assessed through survival rate calculations and confirmed via vital dye exclusion tests. Statistical analysis was conducted using ANOVA to determine significance among treatment groups, (p≤0.05). Results: Significant differences in larval survival were observed (p≤0.01). Distilled water yielded the highest post-thaw viability at 81.6%, while ethylene glycol showed 0% survival. Acetic acid preserved 23.3% of larvae. Vital dye exclusion assays supported these findings with statistically significant results (p≤0.05). Conclusion: Distilled water proved to be the most effective cryopreservation medium for GI nematode larvae. This study supports the utility of cryopreservation and rapid viability assessment in parasitology, offering valuable tools for epidemiological surveillance and disease management, particularly in regions with limited laboratory culturing options.