Pulmonary filariasis is a kind of nematode parasitic in cattle lungs. It is a viviparous nettail nematode, which causes pulmonary filariasis in cattle. Because adults lay more eggs in the bronchus, the eggs are spit into the mouth with coughing, moved into the digestive tract after swallowing, and finally excreted with feces. They form larvae in eggs, contain larvae eggs or excrete in feces as first-stage larvae, and then spread.