Corticosteroids, often called “steroids,” are powerful medications known for their anti-inflammatory properties. They are synthetic versions of hormones naturally produced by the adrenal glands. Parasites are organisms that live on or in a host, obtaining nutrients at the host’s expense. The interaction between corticosteroids and parasitic infections is intricate, and this article clarifies their relationship.
Steroids and the Immune System
Corticosteroids primarily modulate the body’s immune system. They reduce inflammation, a natural immune response to injury or infection, by suppressing immune cell activity and reducing inflammatory chemical production. These drugs decrease the number and activity of immune cells such as lymphocytes, eosinophils, and macrophages, which normally fight off pathogens. By dampening these immune responses, corticosteroids weaken the body’s natural defenses against foreign invaders, including parasites, creating a more permissive environment for these organisms.
Direct Effects on Parasites
Corticosteroids do not possess direct antiparasitic properties. Unlike specific antiparasitic medications designed to directly target and kill parasitic organisms, steroids do not act in this manner. Their chemical structure and mechanisms of action are not geared towards disrupting the biological processes unique to parasites, such as their metabolism or reproduction. While host hormonal environments, including corticosteroids, can influence parasite growth and development, this is not a direct killing effect. Some research indicates they may play a role in parasite survival within the host.
Exacerbation of Parasitic Infections
By suppressing the host’s immune system, corticosteroids can significantly worsen existing parasitic infections, reactivate latent ones, or increase susceptibility to new infections. This is a major concern, particularly in individuals with undiagnosed or pre-existing parasitic infestations.
A prominent example is Strongyloides stercoralis hyperinfection syndrome. Strongyloides stercoralis is a nematode capable of autoinfection, completing its life cycle entirely within the human host. When corticosteroids are administered, the suppressed immune system allows the parasite to multiply rapidly and disseminate widely throughout the body, leading to a potentially fatal hyperinfection syndrome. This syndrome can manifest with severe gastrointestinal, pulmonary, and neurological symptoms, and the mortality rate can be as high as 70% to 100% if not promptly diagnosed and treated.
Beyond Strongyloides, corticosteroids can also exacerbate other parasitic diseases in immunocompromised individuals. For example, toxoplasmosis, caused by the protozoan parasite Toxoplasma gondii, can reactivate and cause severe illness, including encephalitis, chorioretinitis, pneumonitis, and myocarditis, in patients receiving immunosuppressive treatments like corticosteroids. Similarly, cryptosporidiosis, a diarrheal disease caused by Cryptosporidium parasites, can become life-threatening in immunocompromised individuals, as the body’s ability to clear the infection is compromised by steroid use.
Steroids in Parasitic Disease Management
Despite the risks, corticosteroids are sometimes used in the management of parasitic diseases, but not to eliminate the parasites themselves. Their role is to mitigate severe inflammatory or allergic reactions caused by the parasites or the host’s immune response to them. This is a nuanced application, always performed in conjunction with specific antiparasitic drugs and under strict medical supervision.
For instance, in neurocysticercosis, an infection of the brain by the larval stage of the pork tapeworm Taenia solium, corticosteroids are used to manage the inflammation and cerebral edema (swelling in the brain) that can occur around the cysts, especially when antiparasitic medications are initiated. The death of the parasites induced by antiparasitic drugs can trigger an intense inflammatory response, and corticosteroids help to control this potentially damaging reaction.
Similarly, in severe cases of schistosomiasis, where the body’s immune reaction to parasite eggs can cause significant inflammation in organs like the liver or spleen, corticosteroids may be used to reduce this inflammatory damage.
In cases of eosinophilic meningitis caused by parasites like Angiostrongylus cantonensis, corticosteroids are administered to reduce the inflammation of the membranes covering the brain, which is primarily caused by the immune response to dead larvae. This helps alleviate symptoms such as severe headaches. Medical professionals should be aware of a patient’s travel history and potential exposure to parasitic infections before prescribing corticosteroids, especially for long-term use.