How Long Can Schistosomiasis Survive Untreated?

If left untreated, adult schistosomiasis worms typically live for 3 to 5 years inside the human body ^[1]. However, in some cases, these parasites can survive for several decades ^[1][2]. Because the infection does not typically go away on its own, medical testing and treatment are essential even if your last exposure to contaminated freshwater was many years ago.

The Life of the Parasite in Your Body

Once the schistosomiasis parasites enter your body through your skin, they mature into adult worms and travel to your blood vessels ^[3]. Depending on the specific type of Schistosoma parasite, they will settle either in the blood vessels surrounding your intestines or your bladder ^[4].

Once settled, the adult worms begin a continuous cycle of reproducing and laying eggs ^[4]. It is important to know that the adult worms themselves do not multiply inside your body—the number of adult worms you have depends entirely on how many parasites entered your skin during your freshwater exposures ^[3]. However, a single female worm can lay hundreds to thousands of eggs every day for as long as she lives ^[5].

Why Time Doesn’t Heal This Infection

Many patients wonder if they can simply wait out the infection. While it is true that the adult worms will eventually die of old age, waiting for this to happen is not a safe option for two main reasons:

• Long Lifespan: While the average lifespan of an adult worm is 3 to 5 years ^[1], medical literature has documented active, ongoing infections lasting for 30 to 40 years after a person leaves an area where the parasite is found ^[2][6].
• Continuous Egg Production: The adult worms themselves are surprisingly well-tolerated by the human immune system ^[4]. The actual damage from schistosomiasis is caused by the thousands of eggs the worms lay ^[7]. While some eggs leave your body through urine or feces, many become trapped in your internal organs, such as your liver, bladder, or intestines ^[5]. Your immune system attacks these trapped eggs, leading to inflammation and fibrosis (permanent scarring of the tissue) ^[5][8].

Every year that the adult worms remain alive in your blood vessels, they continue to lay eggs ^[4]. This continuous buildup of trapped eggs leads to cumulative organ damage over time, which can eventually cause severe complications like bloody diarrhea, liver damage, or kidney issues ^[4][7]. In the case of bladder-dwelling parasites (S. haematobium), decades of trapped eggs also significantly increase the risk of developing bladder cancer ^[9][10].

The Importance of Testing and Treatment

Because these parasites can quietly survive and lay eggs for decades, you cannot assume an infection has resolved just because you no longer live near the freshwater source where you were exposed ^[6][4]. Furthermore, chronic schistosomiasis can remain completely silent—meaning you might not feel any symptoms for years while the organ damage is slowly occurring ^[4][11].

If you have ever been exposed to untreated freshwater in an area where schistosomiasis is common, it is crucial to get tested, regardless of how much time has passed ^[12]. For exposures that happened years ago, standard stool or urine tests might incorrectly come back negative; a specific blood test (an antibody test) is usually required to detect an old infection ^[13][14].

Safe and effective oral medications, such as praziquantel, are available that can kill the adult worms and stop the egg production ^[8]. While existing scarring (fibrosis) may be permanent, killing the worms immediately halts further damage to your body ^[8]. Keep in mind that treatment does not make you immune—if you return to contaminated water, you can be infected again ^[8].