Transmission and life cycle
Infected individuals release Schistosoma eggs into water via their fecal material or urine. After larvae hatch from these eggs, the larvae infect a very specific type of freshwater snail. For example, in S. haematobium and S. intercalatum it is snails of the genus Bulinus, in S. mansoni it is Biomphalaria, and in S. japonicum it is Oncomelania. The Schistosoma larvae undergo the next phase of their lifecycles in these snails, spending their time reproducing and developing. Once this step has been completed, the parasite leaves the snail and enters the water column. The parasite can live in the water for only 48 hours without a mammalian host. Once a host has been found, the worm enters its blood vessels. For several weeks, the worm remains in the vessels, continuing its development into its adult phase. When maturity is reached, mating occurs and eggs are produced. Eggs enter the bladder/intestine and are excreted through urine and feces and the process repeats. If the eggs do not get excreted, they can become engrained in the body tissues and cause a variety of problems such as immune reactions and organ damage. While transmission typically occurs only in countries where the freshwater snails are endemic, a case in Germany was reported where a man got Schistosoma by an infected snail in his aquarium.Humans encounter larvae of the Schistosoma parasite when they enter contaminated water while bathing, playing, swimming, washing, fishing, or walking through the water.
See Hs and Ts

Hypovolemia
Hypoxia
Hydrogen ions (Acidosis)
Hyperkalemia or Hypokalemia
Hypoglycemia
Hypothermia
Tablets or Toxins
Cardiac Tamponade
Tension pneumothorax
Thrombosis (e.g., myocardial infarction, pulmonary embolism)
Tachycardia
Trauma (e.g., hypovolemia from blood loss)The possible mechanisms by which the above conditions can cause pulseless in PEA are the same as those recognized as producing circulatory shock states. These are (1) impairment of cardiac filling, (2) impaired pumping effectiveness of the heart, (3) circulatory obstruction and (4) pathological vasodilation causing loss of vascular resistance and excess capacitance. More than one mechanism may be involved in any given case. Diagnosis
The absence of a pulse confirms a clinical diagnosis of cardiac arrest, but PEA can only be distinguished from other causes of cardiac arrest with a device capable of electrocardiography (ECG/EKG). In PEA, there is organised or semi-organised electrical activity in the heart as opposed to asystole (flatline) or to the disorganised  electrical activity of either ventricular fibrillation or ventricular tachycardia. Treatment
Cardiac resuscitation guidelines (ACLS/BCLS) advise that cardiopulmonary resuscitation should be initiated promptly to maintain cardiac output until the PEA can be corrected. The approach in treatment of PEA is to treat the underlying cause, if known (e.g. relieving a tension pneumothorax). Where an underlying cause for PEA cannot be determined and/or reversed, the treatment of pulseless electrical activity is similar to that for asystole.