The Pediatric Patient with Abdominal Pain in Rural Tanzania
Imagine you are a provider working in a rural clinic in Tanzania near Lake Victoria...
Your next patient is a seven year-old male who presents complaining of intermittent abdominal pain, frequent cough, and dyspnea on exertion. The patient’s mother isn’t sure how long he has had these symptoms, but thinks that they have been going on for more than one year. The patient denies fevers, chills, vomiting, dysuria, and hematuria but does admit to intermittent diarrhea. The mother states that she has not noted any obvious blood or worms in his stool. The mother states that the family gets their drinking water from rain water and the local well and washes their clothes and dishes in Lake Victoria.
The mother does tell you that the patient was evaluated at the local hospital a few months ago and that he required a blood transfusion. Unfortunately, she cannot tell you what his diagnosis was or the reason that he required the blood transfusion but she does recall that the patient tested negative for HIV.
Vital Signs: Temp 36.9 F, HR 100 bpm, BP 99/57 mmHg, RR 21/min
General: Very thin, young, black male with grossly protuberant abdomen who appears younger than stated age. No acute distress.
HEENT: PERRL, EOMI. Very pale conjunctivae. Oropharynx is clear with no exudate. MMM. No appreciable lymphadenopathy.
Cardiac: RRR, no m/r/g
Pulmonary: Lungs CTAB, no focal wheezes, rhonchi or crackles
Abdomen: Soft, markedly distended. Nontender. +Hepatosplenomegaly. +Fluid wave.
Extremities: Very thin. No significant swelling or edema noted.
WHAT IS THE MOST LIKELY DIAGNOSIS?
Although in this small rural clinic there is no stool or urine microscopy available, the patient lives in an endemic area, with known exposure to freshwater, and classic symptoms of chronic schistosomiasis. In this setting, the diagnosis can be made clinically. Schistosomiasis is a parasitic disease caused by a fluke worm. There are five species of schistosome that infect humans, and affect more than 200 million people worldwide, with the highest incidence occurring in Sub-Saharan Africa. The primary species that cause disease in Africa are Schistosoma mansoni and Schistosoma haematobium.
Infection occurs through exposure to contaminated freshwater. Contaminated freshwater contains snails that serve as the intermediate host species (see life cycle image). Once the schistosomes have penetrated the skin, they enter the human host venous system where they mature into adult fluke worms. Adult fluke worms lay eggs, some of which are excreted in the host feces and urine, while others remain in the host venous circulation. Ultimately, it is the host immune response to the migrating eggs that is responsible for clinical symptoms. As eggs migrate they become trapped in small spaces and cause inflammation via an eosinophilic granulomatous reaction which leads to fibrosis.
Presenting symptoms are variable depending on the stage of infection. Within hours to days of skin penetration, patients may present with pruritic papular or urticarial rash at the site of skin penetration known as “swimmer’s itch”. "Swimmer's itch" will only occur with repeated exposures as it is caused by a hypersensitivity reaction. Travelers who acquire schistosomiasis infection while abroad are unlikely to present with these symptoms unless they have had previous exposures. The acute syndrome of infection, known as Katayama fever, manifests 3-8 weeks after initial exposure and is most apparent in non-immune hosts such as travelers. Symptoms commonly include fever, chills, generalized body aches, headache, cough, diarrhea, and abdominal pain. Lab testing can show an elevated eosinophil count and chest x-ray may show interstitial pneumonitis.
Symptoms of chronic infection develop over years and are variable depending on the organ system affected. This patient presented with classic signs and symptoms of liver, intestine, and lung involvement. Intestinal involvement commonly presents with chronic, intermittent, abdominal pain and diarrhea. Colonic ulceration and bleeding may also be present and can result in anemia. In more severe cases strictures and obstruction can occur, although this is rare. In the liver, periportal fibrosis results in portal hypertension and hepatosplenomegaly. Portal hypertension can also cause formation of portosystemic collateral vessels, which create a passage for migration of eggs into the pulmonary circulation. As eggs become entrapped and cause inflammation they can also cause pulmonary endarteritis which leads to pulmonary hypertension and eventually cor pulmonale. Pulmonary disease most commonly manifests as dyspnea. S. haematobium can cause genitourinary schistosomiasis which presents as dysuria, hematuria, and can lead to infertility and increased risk for HIV transmission. Neuroschistosomiasis can affect both the spinal cord and the brain and is a medical emergency. In addition to organ specific disease, children can suffer from malnutrition and growth retardation as was seen in this patient.
Praziquantel, dosed at 40mg/kg, is the primary treatment of both acute and chronic schistosomiasis. Limited data suggests that optimal treatment for acute infection should be initiated after acute symptoms have resolved and administered concomitantly with corticosteroids which may lessen the tendency of Praziquantel to aggravate symptoms. A single dose is often sufficient however, some individuals may require repeat dosing two weeks later. Neuroschistosomiasis is a unique instance in which immediate corticosteroid treatment with prednisone 1-2 mg/kg is imperative to prevent irreversible tissue damage. Because Praziquantel can worsen the host’s inflammatory response it should not be given until a few days after steroid treatment has begun.
Exposure to schistosomiasis occurs when people use contaminated freshwater sources for swimming, bathing, fishing, and cleaning. Tourists commonly become infected by engaging in water sports and other activities without exercising proper precautions. Because contracting schistosomiasis is linked to fresh water exposure, prevention strategies focus on community education, water sanitation, and mass treatment. However, there are limitations to effecting change in population behaviors due to the scarcity of freshwater sources leaving many people with no safe alternatives. Repeated mass treatments do help reduce the prevalence and increase immunity to reinfection, however there is also a growing problem of reduced sensitivity to Praziquantel.
Authored by Alexa Sabedra, MD
Posted by Grace Lagasse, MD
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