Background: Toxocara canis, a source of visceral larva migrans, causes toxocariasis and induces respiratory symptoms. The reasons by which the pulmonary pathological alteration in the lungs infected with T. canis remain unclear. Methods: The involvement of the pulmonary pathological alteration by histology, enzyme activity, and Western blot analysis in the lungs of BALB/c mice after the infection of 2000 embryonated eggs. Results: The pathological effects gradually increased after the infection culminated in severe leukocyte infiltration and hemorrhage from days 4-14 post-inoculation. Gelatin zymography using substrate showed that the relative activity of matrix metalloproteinase (MMP) -9 and MMP-2 significantly increased in T. canis-infected mice. Western blot analysis indicated that the MMPs protein level of fibronectin monomer significantly increased in T. canis-infected mice compared with that in uninfected control. T. canis larvae mainly initiated leukocyte infiltration and hemorrhage in the lungs. Conclusion: These phenomena subsequently induced the activities of MMPs in parallel with the pathological changes in early stage pulmonary inflammation. In conclusion, T. canis larval migration activated the MMPs and caused pulmonary pathogenesis.
