A variety of parasites can affect the lungs, including Toxoplasma gondii , Strongyloides stercoralis , Ascaris lumbricoides , and Plasmodium malariae .  These organisms typically enter the body through direct contact with the skin, ingestion, or via an insect vector.  Except for Paragonimus westermani , most parasites do not affect specifically the lungs but involve the lungs secondarily to other sites.  Some parasites, in particular those belonging to the Ascaris and Strongyloides genera, stimulate a strong eosinophilic reaction, which may result in eosinophilic pneumonia .  In other infections, such as malaria, lung involvement is due primarily to cytokine-induced systemic inflammation.  In the developed world these infections are most common in people returning from travel or in immigrants.  Around the world, these infections are most common in the immunodeficient.