Emergent Management of Acute Schistosomiasis 

Updated: Jan 06, 2022
Author: Ross A Wanner, MD; Chief Editor: Jeter (Jay) Pritchard Taylor, III, MD 

Overview

Background

Schistosomiasis, also known as bilharziasis, bilharziosis, or snail fever, is a waterborne disease caused by infection from parasitic trematodes (flukes) of the genus Schistosoma. The Centers for Disease Control and Prevention (CDC) considers schistosomiasis one of several Neglected Tropical Diseases, a group of preventable and treatable infectious diseases affecting more than one billion people globally. Although preventable and treatable, it is estimated that the morbidity and mortality of schistosomiasis worldwide is second only to malaria. Schistosoma are not endemic to the United States; however, due to increased travel to and from areas where the parasites are endemic, knowledge surrounding the acute management of complications of schistosomiasis is growing increasingly relevant.[1]

According to the World Health Organization (WHO), schistosomiasis is most prevalent in Africa, Southeast Asia, Middle East, and South America and is most commonly found in less developed regions with contaminated fresh water sources without means of sanitation.[2]  The most common disease presentations manifest in either intestinal or urogenital complications. School-age children are at a particularly increased risk of infection due to more common involvement in recreational activities in infected waters, such as swimming and fishing.[3]

Infection by schistosomes occurs via transdermal penetration of the cercariae larvae upon contact with infested waters. The larvae then develop into adults once inside the bloodstream and produce eggs, which are deposited in the stool or urine. The clinical syndrome of schistosomiasis is primarily due to the body’s response to the eggs in the bloodstream.[4]  The life cycle repeats when the eggs return to freshwater sources via human or animal excrement, during which they mature into larvae, using a snail as its intermediate host.[5]

The three species seen most often in patients with systemic schistosomiasis are S. haematobium, (primarily urogenital pathology), S. mansoni (primarily liver pathology), and S. japonicum (primarily liver and CNS pathology). Other species, including S. mekongi, S. intercalatum, and S. guinessnsis, may also cause systemic human disease, although this is much less common, and the treatment remains the same.[6]  Finally, other species of schistosomes may cause severe dermatitis, but the larvae do not mature into adults and cause systemic disease, so this syndrome is distinct from other forms of schistosomiasis.[7]

 

Prehospital and Emergency Department Care

Prehospital care

Prehospital care is largely supportive. Fluid supplementation, inotropes, empiric antibiotics, vasopressors, and other interventions may be implemented in attempt to stabilize patients prior to known underlying etiology.

Emergency department care

In the emergency department (ED), the physician should initially focus on standard resuscitative measures. The diagnosis of schistosomiasis is strongly dependent upon history and physical exam. Identification of risk factors, including travel to endemic areas, freshwater exposures, onset and constellation of symptoms, close contacts with similar clinical syndromes are important clues to identifying these diseases. Most acute infections, within 8 weeks, are asymptomatic and the clinical syndrome of acute schistosomiasis (also called Katayama fever) is non-specific. These non-specific sequelae are associated with the life cycle and the production of eggs released in the bloodstream.[8]  Katayama fever should be on the differential for patients from endemic areas with persistent fevers. Typically, infections manifest months to years later with more severe symptoms. 

Findings suggestive of acute schistosomiasis include[6, 8, 9] :

  • Systemic symptoms such as fever, general malaise, myalgias, pruritic rash (due to larval penetration into the skin)
  • Central nervous system (CNS): headache, rarely encephalitis
  • Cardiopulmonary: cough, especially nocturnal, and pulmonary infiltrates
  • Gastrointestinal (GI): abdominal pain, nausea
  • Genitourinary (GU): dysuria, hematuria, genital sores

Findings suggestive of chronic schistosomiasis include those above, in addition to[3, 9, 10, 11, 12, 13, 14, 15] :

  • Systemic: fever, general malaise, myalgias, pruritic rash
  • CNS: granulomatous disease with seizure, confusion, cognitive delay, myelopathy, transverse myelitis, cauda equina, or other neurologic syndromes associated with lesion-specific location
  • Cardiopulmonary: dyspnea, granulomatous pulmonary endarteritis, pulmonary hypertension 
  • GI: hepatosplenomegaly with right or left upper quadrant abdominal pain, portal hypertension with or without ascites, ulceration and hematochezia
    • Specifically, periportal fibrosis (also called Symmers’ fibrosis) is found in portal hypertension secondary to schistosomiasis [16]
  • GU: dysuria, hematuria, infertility, increased risk for HIV coinfection, urinary tract obstruction, bladder cancer, genital lesions, nephrotic syndrome
  • Hematologic: iron deficiency anemia, thrombocytopenia

On laboratory evaluation, a high eosinophilia count is common. Diagnosis of schistosomiasis is done through stool ova and parasite (O&P) or urine studies, which will identify eggs, or through serologic testing. The results of stool and urine studies will also be dependent upon the species of schistosome infecting the patient; for example, S. haematobium will likely have eggs passed in the urine, along with blood, whereas eggs of other species will primarily present in stool. Serology is the best diagnostic test and expatriates may present asymptomatic but seropositive from light infections. Infections almost universally present with eosinophilia, whether acute or chronic in nature, and, depending on disease chronicity and severity, may have associated thrombocytopenia due to portal hypertension and splenic sequestration. In addition, ultrasound may show evidence of periportal fibrosis.[3, 17]

 

Pharmacologic Therapy

Management of infectious schistosomiasis has the same initial approach; however, management of associated complications can frequently require consultation to other medical specialties. Therapy is universally medical, with praziquantel, an oral anthelminthic +/- corticosteroid pretreatment. It is dosed depending on the infectious species (either 40 mg/kg/day divided into two doses, or 60 mg/kg/day divided into three doses) and both courses are complete after 1 day. Praziquantel only is effective against the adult parasite and, given most systemic symptoms are secondary to the body’s response to parasitic eggs, patients may continue to have symptoms for up to 4 weeks after treatment. According to the WHO, if infected during pregnancy, praziquantel is a category B drug and its benefits outweigh the risk of untreated infection or drug effects on the fetus. A pediatric formulation of the drug is also being studied.[3, 18]  As mentioned, steroids can be given to reduce symptomatic burden, as well as inflammatory reaction after praziquantel administration. Recommendations are not well-defined and include prednisone 1.5-2 mg/kg/d for up to 3 weeks, or prednisolone 1 mg/kg/d for up to 10 days.[19, 20]  Medical treatment is effective in eradicating anywhere from 57-88% of infections with just one round of praziquantel, and is even more effective with repeat doses. There also have been repeat efficacy studies demonstrating no evidence of resistance of schistosomiasis to praziquantel.[21, 22]

 

Inpatient and Outpatient Care

Inpatient care

Although most chronic management is out of the scope of this article, emergent intervention and consultation may be necessary and is directed at the underlying pathophysiology, as mentioned. In many cases of severe infection, inpatient admission and management may be indicated. For example, portal hypertension leading to variceal bleeding will require airway management, hemodynamic stabilization with transfusion, fluids, and vasopressors, proton pump inhibitors, octreotide, and GI consultation for endoscopic therapy with banding among other well-defined emergent interventions. Urinary obstruction can be treated with anti-inflammatory drugs, catheter placement, and urology consultation for stenting or other interventions. Neuroschistosomiasis presenting with seizure can be treated with abortives, antiepileptics, steroids (for edema and inflammation), and inpatient admission for infection treatment, cerebral granuloma debridement, among other interventions. 

Outpatient care

Patients with schistosomiasis should be followed up 4-6 weeks after medical treatment, based upon the pathophysiology of the disease taking up to 4 weeks to eradicate the body of eggs. Retreatment is indicated after re-exposure and reinfection. Patients with likely ongoing exposure may benefit from annual treatment in addition to education to reduce exposure risk. Patients can be monitored via repeat stool or urine studies, as serologic testing will remain positive. As previously mentioned, patients with evidence of portal hypertension, pulmonary hypertension, CNS infection, urinary obstruction, or other irreversible complications will require long-term follow-up care with the appropriate specialists.

Prophylaxis

Prophylaxis with annual or biannual praziquantel is recommended for those living in endemic regions. Patients traveling to endemic regions may also receive prophylaxis before or after travel. Several vaccines are also in clinical development.[23]