By Fernandez, Nella C.; Mortensen, Joel
Journal of Continuing Education Topics & Issues , Vol. 14, No. 2
The popularity of "adventure vacations," along with the mobilization of the population of Asian and African countries due to armed conflict, has brought exotic infectious organisms into the United States. The clinical manifestations of these can sometimes be easily associated with the history of travel, but in some cases, the latency of these infectious diseases spans weeks, months or even years.
Schistosomiasis is one such disease, and is second to malaria in the world's parasitic diseases in terms of endemicity and the number of infected people. (1)
Following is the case of a patient diagnosed with urinary schistosomiasis and a brief review of the pathophysiology, diagnosis and current recommendations for treatment and prevention.
Our patient is a 17-year-old male, born in the United States, who, at the age of 8 years old, moved with his parents to the African nation of Mali, where he stayed until one month before consulting our hospital.
For the previous 18 months, he observed persistent painless hematuria, with scant bright red blood at the end of each urination. The patient denied swimming in lakes or rivers in Mali. No family history of hematuria was elicited.
His blood count was within normal limits; however, the differential showed eosinophilia (23%, normal range 0-3%). Two tests for ova and parasites in the urine were negative for schistosomiasis; however, due to the strong suspicion, immunoglobulin G for schistosomas was ordered. The result was positive and treatment with praziquantel was prescribed.
[FIGURES 1 OMITTED]
The patient was referred to nephrology. An ultrasound showed echogenic polypoid lesions arising from the posterior and left lateral wall of the bladder with possible underlying bladder thickening, suggestive of chronic infection/inflammation with schistosomas.
A third sample of urine for ova and parasite was received and after concentration procedures, numerous ova consistent with Schistosoma haematobium were identified. (Figure 1A & 1B)
Schistosomiasis or bilharzia is highly endemic in tropical and subtropical areas of the world, including most African countries and regions of Asia, South America, the Caribbean, and the Middle East. An estimated 200 million people are infected annually. (2)
The three main species causing infections in humans are S haematobium (urinary schistosomiasis), S japonicum and S mansoni (intestinal schistosomiasis). Two other species more localized geographically are S mekongi and S intercalatum (rectal schistosomiasis). (3,4)
Life cycle of the parasite
Schistosomes are 1-2 cm long white parasitic flatworms, belonging to the Trematoda class of parasites; they are referred to as trematodes or flukes. During adult life, the female is embedded in the gynecophoric canal of the male and the paired adult flukes live in the venules of the mesenteric or vesical plexus. (4) The infection is usually acquired via contact with freshwater that contains infectious, free-living, cercarial larvae. The cercariae penetrate the intact skin, shedding their forked tail to become schistosomulae. The schistosomulae then migrate into the blood and lymph vessels and are carried to the heart and lungs. After entering the arterial circulation via the left side of the heart, the schistosomulae settle in the liver where they mature into adults over a period of one to four weeks before reaching the vesical venous plexus. (Figure 2A, B and C)
[FIGURE 2 OMITTED]
The parasite remains in these blood vessels for the life of the patient, adhering to the wall of the blood vessels by a ventral and an oral sucker. After one to three months, the female worm produces eggs, which can travel hematogenously to other sites or can traverse from the vascular space through host tissues to the urinary bladder where they are excreted in the urine. …