Peachy sputum is a common clinical manifestation of pulmonary schistosomiasis. Lung schistosomiasis, also known as pulmonary schistosomiasis, is an acute or chronic endemic parasitic disease caused by Schistosoma haematobium. The parasites are mainly found in the lungs, with cough and peachy sputum as the main manifestations, but also in various tissues and organs, such as the brain, spinal cord, gastrointestinal tract, abdominal cavity and subcutaneous tissue, producing corresponding symptoms. The clinical manifestations are also diverse. The incubation period is a few days to 20 years, mostly within 1 year. What are the causes of rotten peach-like blood sputum? (A) Causes of pathogenesis There are nearly 40 species of pulmonary schistosomes known in the world, among which 8 species are pathogenic to human, mainly Schistosoma wei and Schistosoma sichuanum. The first intermediate host of S. pulmonarius is more than 20 kinds of freshwater snails, and the second intermediate host is crabs, mayflies and crustaceans. The final host is human or dogs, cats, pigs and other mammals, in addition to humans, these animals are also known as worm hosts, is the main source of infection constituting the natural source of the epidemic. (B) Pathogenesis The cysts enter the body through the mouth, decapsulate into child worms in the intestine, which pass through the intestinal wall into the thoracic cavity, penetrate the diaphragm to reach the thoracic cavity, and develop into adult worms in the lungs. The worms migrate and lay eggs to stimulate tissues, causing tissue damage and immunopathological reactions in humans, resulting in tissue necrosis and abscess formation. The granulation tissue around the lesion proliferates to form a cyst wall, resulting in a cyst. The cyst fluid is brownish-red and jam-like, containing worm bodies, Charcot-Redden crystals and eosinophils. The worms die, the contents are expelled or absorbed, and the cyst is replaced by fibrous tissue to form a scar. Since the eggs do not develop into capillaries in the body and do not secrete soluble antigens, they only cause mechanical or foreign body irritation and are surrounded by inflammatory cell infiltration and form corn-sized pseudonodules. It is a foreign body type granulomatous reaction and gradually fibrosis later. The worm is wandering and can cause lesions in a variety of tissues and sites.