Trematodes

Leaf-like, unsegmented flatworms with two suckers (oral and ventral). They have a mouth surrounded by oral suckers, a pharynx, and an esophagus; they lack an anus.

Trematodes are classified by their location in the host. Common types include blood flukes, intestinal flukes, hepatic (liver) flukes, and lung flukes.

A parasitic disease caused by blood flukes (Schistosoma japonicum, S. mansoni, and S. haematobium). It is spread through contact with contaminated water.

Schistosomes have a complex life cycle involving two hosts: a definitive host (human) and an intermediate host (snail). Adults reproduce sexually in humans, laying eggs that are released into water. Eggs hatch into miracidia, which infect snails. Miracidia develop into cercariae, which leave the snail and infect humans through skin penetration.

Schistosome eggs, not adult worms, are the major cause of illness. They induce a granulomatous reaction leading to fibrosis in the liver (S. mansoni and S. japonicum) or the urinary tract (S. haematobium).

Chronic infections can cause portal hypertension, ascites, hepatosplenomegaly, esophageal varices, urinary tract complications like bladder obstruction, and even bladder cancer.

Early symptoms include skin itching, rash, fever, headache, chills, diarrhea, and increased eosinophils (white blood cells). This is called 'snail fever' or 'Katayama fever'.

Long-term symptoms include weight loss, enlarged liver and spleen, diarrhea, constipation, dysentery-like illness with bloody stools, and urinary problems.

Diagnosis is primarily done by identifying eggs in stool or urine samples. Biopsies and serological tests can also be used.

Praziquantel is the main drug used, effective against all Schistosoma species. It damages the worm's outer membrane, leading to worm death.

The acute phase of Schistosomiasis with symptoms like skin irritation, fever, and increased white blood cells (eosinophilia).

There is no specific treatment for Katayama syndrome. However, antihistamines and corticosteroids can relieve the symptoms.

Prevention involves: eliminating the intermediate host (snails), reducing water pollution with human waste, avoiding swimming in contaminated water, and treating infected individuals.

Schistosome eggs trigger an exaggerated immune response (granulomatous inflammation), leading to tissue fibrosis and scarring in the liver, bladder, or other organs.

The inflammation caused by the eggs leads to long-term complications like portal hypertension, ascites, and even bladder cancer.

S. mansoni and S. japonicum infections lead to egg-induced inflammation in the liver, causing fibrosis, portal hypertension, ascites, and enlarged liver (hepatomegaly).

S. haematobium eggs trapped in the bladder wall cause inflammation, scarring, and obstruction, leading to urinary problems, bladder calcification, and even cancer.

A condition caused by obstruction of the urinary tract, leading to dilation of the kidneys and accumulation of urine. It is a complication of S. haematobium infection.

Prevention involves: 1. Eradicating snails 2. Reducing water pollution 3. Avoiding contaminated water 4. Treating infected individuals.

The host in which a parasite reaches its adult stage and reproduces sexually. For Schistosoma, the definitive host is a human.

A host in which a parasite lives during a stage in its development. For Schistosoma, the intermediate host is a snail.

The first larval stage of Schistosoma, released from the egg in water. It infects snails.

The infective stage of Schistosoma larvae that leaves the snail and can infect humans through skin penetration.

The stage of Schistosoma that develops from a cercaria after penetrating human skin. It enters the bloodstream and migrates to its final destination.

S. japonicum is a particularly dangerous species because it can infect a wide variety of snails and cause more severe liver damage compared to other Schistosoma species.

S. haematobium infection leads to egg-induced inflammation and fibrosis in the bladder wall. This causes urinary problems, bladder calcification, and potentially bladder cancer.