Emergent Management of Acute Schistosomiasis
- Author: Grant Wei, MD, FAAEM, FACEP; Chief Editor: Robert E O'Connor, MD, MPH more...
Owing to increased population flow from areas where schistosomiasis is endemic, emergent management of acute schistosomiasis is likely to become a matter of increased concern. Schistosomiasis (also known as bilharzia, bilharziasis, bilharziosis, or snail fever) is a human disease syndrome caused by infection from one of several species of parasitic trematodes of the genus Schistosoma. Schistosomiasis is a major source of morbidity and mortality for developing countries in Africa, South America, the Caribbean, the Middle East, and Asia.
Tourism to and immigration from endemic areas can result in schistosomiasis cases presenting anywhere in the developed world. Acute schistosomiasis among travelers may be increasing, and rates of emigration from endemic areas are rising. In the complete absence of routine presymptomatic screening of these groups in developed countries, it is increasingly likely that patients with acute or chronic schistosomiasis will present to emergency departments (EDs) with a variety of complaints in nonendemic areas.[2, 3]
Pediatric and adolescent patients who have traveled or lived in endemic areas are at the highest risk for exposure to schistosomes and are at risk for serious long-term complications. These patients usually respond well to drug therapy and should receive aggressive treatment and follow-up care.
Most human schistosomiasis is caused by S haematobium, S mansoni, or S japonicum, with the former causing urinary symptoms and the latter two causing intestinal symptoms. Less prevalent species, such as S mekongi and S intercalatum, may also cause systemic human disease. Less importantly, other schistosomes with avian or mammalian primary hosts can cause severe dermatitis in humans (eg, swimmer's itch secondary to Trichobilharzia ocellata).[4, 5, 6, 7, 8, 9, 10]
Schistosomiasis is transmitted via eggs excreted in feces or urine of infected individuals. The larvae are then maintained in a freshwater snail intermediate host, where they mature and are eventually released. Infection occurs when humans come into contact with infested freshwater, allowing the larvae to penetrate the skin.
Prehospital and Emergency Department Care
Prior to the patient’s arrival at the hospital, support and stabilization are provided for acute complications of infection, if present. These might include volume depletion, heart failure, and gastrointestinal (GI) bleeding.
Emergency department care
In the emergency department (ED), the physician confirms the diagnosis, begins antibiotic therapy, and stabilizes patients with acute complications of schistosomiasis.
The criterion standard in diagnosing schistosomiasis is microscopic egg detection in urine or feces. However, it takes 1-3 months for larvae to fully mature and lay eggs, so early diagnosis is not always possible. There are also tests to detect schistosomal antigens or antischistosomal antibodies in blood, urine, or sputum. Other methods that are currently being studied include polymerase chain reaction (PCR) testing and assays for certain schistosomal cytokines or biomarkers. As these diagnostic tools may not be readily available in the emergency department, it is important to obtain a thorough history (especially travel history) and physical examination.
Acutely, patients with schistosomiasis may present with the following:
Pruritic rash due to cercarial penetration into the skin
Nonspecific symptoms such as fever, myalgias, and malaise
Right upper quadrant abdominal pain
Dysuria or hematuria
Important laboratory findings include (1) eosinophilia and (2) hematuria and proteinuria, which is associated with urinary schistosomiasis.
Manifestations of chronic schistosomiasis can also months or years after acute infection. Symptoms are nonspecific, as multiple systems can be affected depending on the primary location of egg production and on the species of schistosome involved. Manifestations may include the following:
CNS: Headache, seizure, increased intracranial pressure (ICP), myeloradiculopathy, transverse myelitis
Cardiopulmonary: Cough, wheezing, dyspnea on exertion, hemoptysis
Gastrointestinal: Diarrhea, hematemesis, portal hypertension
Genitourinary: Dysuria, hematuria, irregular menstruation, pelvic pain, genital lesions
Management of hepatosplenic,[13, 14] GI, urinary, cardiopulmonary, and central nervous system (CNS) complications are summarized as follows:
Volume depletion secondary to diarrhea - Rarely severe, and is treated with intravenous or oral volume replacement; minor lower GI bleeding and chronic anemia may be present but rarely require transfusion
Portal hypertension with hematemesis - Treatment with fluid resuscitation, transfusion, endoscopic therapy, or surgery may be required
Urinary obstruction - May require stenting or other drainage procedures
Salmonella (or other gut source) sepsis - May require antibiotics and fluids
Pulmonary hypertension and cor pulmonale - May require oxygen, diuresis, antiarrhythmics, or other interventions
Cerebral infection - May require seizure control or management of intracranial pressure
Transverse myelitis - May require steroids and supportive care as well as antihelminthic therapy
Definitive therapy can be initiated and often completed in the ED if the diagnosis is clear. During acute infections, antihelminthic treatment may at first exacerbate symptoms as a result of increased antigen release, usually requiring corticosteroid support. Treatment may produce a Loefflerlike syndrome in cases of heavy infestation, which may require pulmonary support.
In the case of pregnant patients, physicians may prefer to defer treatment of schistosomiasis until after the first trimester.
Clearly communicating with the hospital's diagnostic laboratory personnel is crucial for optimal egg detection in stool and urine specimens.[16, 17] Consult specialists as indicated by the complications present or the need for diagnostic procedures, such as colonoscopy.
Treatment of schistosomiasis is unusual in that only one drug, praziquantel, is in wide use. It is given as a one-time dose of 40 mg/kg and can be given to pregnant women after the first trimester. For children younger than 5 years, dose is determined by height. The drug works by increasing permeability of schistosomal cells to calcium, inducing contraction and thus paralysis of the parasites. Drug resistance has been reported and can be produced in laboratory settings but appears still to be uncommon in human infections. Myrrh derivatives have not demonstrated success in testing, but artemisinins are showing efficacy, and trioxolanes also show promise as future drugs.
Drug regimens result in curing the infection in 60-98% of cases and reduce egg burden in the remainder. Dead eggs may continue to shed for months, but treatment should arrest egg-laying, granuloma formation, and future complications. Although frank fibrosis may not reverse, evidence indicates that portal and pulmonary hypertension from granulomatous changes may improve significantly after treatment, particularly in younger patients.
Inpatient and Outpatient Care
Initiate inpatient care for unstable patients with complications, such as GI bleeding, decompensated heart failure, and toxicity, according to the usual indications. Inpatient care is indicated for CNS infections, and therapy should include corticosteroids to reduce inflammation around schistosomal eggs. Surgery may be indicated to remove large masses or granulomas.
Reevaluate patients for symptom resolution and determination of cure. For uncomplicated cases, 4-6 weeks is the optimal follow-up time, corresponding with the maturation of eggs and immature worms that may have survived initial treatment. Retreatment is indicated after reexposure and reinfection. Patients with likely ongoing exposure may benefit from annual treatment in addition to education to reduce exposure risk.
Response may be evaluated by quantitatively decreased egg counts from urine or stool specimens or by antigen testing. Some patients require retreatment. Patients with evidence of portal hypertension, pulmonary hypertension, CNS infection, or urinary obstruction require long-term follow-up care.
Prophylaxis with annual praziquantel treatment may be recommended for those living in endemic regions. Several vaccines are also in clinical development, particularly ones that target S haematobium and S mansoni.
There is controversy as to whether schistosomiasis infection increases susceptibility to hepatitis B or C infection. Although this is not proven, studies have shown that previous schistosomiasis infection can lead to increased rate of liver cirrhosis and overall mortality if the individual also contracts hepatitis B or C.
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