Comorbidity associated with Ascaris suum infection during pulmonary fibrosis exacerbates chronic lung and liver inflammation and dysfunction but does not affect the parasite cycle in mice

Ascariasis is considered the most neglected tropical disease, and is a major problem for the public health system. However, idiopathic pulmonary fibrosis (IPF) is a result of chronic extracellular deposition of matrix in the pulmonary parenchyma, and thickening of the alveolar septa, which reduces alveolar gas exchange. Considering the high rates of ascariasis and pulmonary fibrosis, we believe that these two diseases may co-exist and possibly lead to comorbidities. We therefore investigated the mechanisms involved in comorbidity of <i>Ascaris suum </i>(<i>A. suum</i>) infection, which could interfere with the progression of pulmonary fibrosis. In addition, we evaluated whether a previous lung fibrosis could interfere with the pulmonary cycle of <i>A. suum</i> in mice. The most important findings related to comorbidity in which <i>A. suum</i> infection exacerbated pulmonary and liver injury, inflammation and dysfunction, but did not promote excessive fibrosis in mice during the investigated comorbidity period. Interestingly, we found that pulmonary fibrosis did not alter the parasite cycle that transmigrated preferentially through preserved but not fibrotic areas of the lungs. Collectively, our results demonstrate that <i>A. suum</i> infection leads to comorbidity, and contributes to the aggravation of pulmonary dysfunction during pulmonary fibrosis, which also leads to significant liver injury and inflammation, without changing the <i>A. suum</i> cycle in the lungs.<br>