Rudi Hayden
Urologist
Blood-tests Explained
Disclaimer:
This website is intended to assist with patient education and should not be used as a diagnostic, treatment or prescription service, forum or platform. Always consult your own healthcare practitioner for a more personalised and detailed opinion
Bilharzia
Schistosomiasis, or bilharzia, is a common intravascular infection caused by the Schistosoma trematode worm. Bilharzia is endemic in sub-Saharan Africa where the majority of infections are caused by S. haematobium and S. mansoni. Important transmission sites in Africa are Lake Malawi and Lake Victoria and travellers are commonly infected when swimming there. In South Africa, schistosomiasis is endemic in the northeastern parts, including the North West, Limpopo, Mpumalanga, KwaZulu-Natal and the Eastern Cape. Infection is usually acquired through activities like swimming, bathing, fishing and washing clothes.
Schistosomiasis progresses through three phases:
an acute phase, a chronic phase and an advanced phase, each with different clinical features. The phase of infection also impacts on the diagnostic tests used and their interpretation. Acute schistosomiasis (Katayama Syndrome) occurs in patients experiencing their fi rst infection and presents with fever and eosinophilia, often with skin, abdominal and pulmonary symptoms. This is typically seen in travellers returning from schistosoma endemic countries. Chronic and advanced disease occurs due to chronic local infl ammation to schistosoma eggs trapped in host tissues, which may lead to infl ammation and obstructive disease of the urinary tract (S. haematobium); or intestinal disease, hepatosplenic infl ammation and liver fi brosis (S. mansoni).
A diagnosis of schistosomiasis is based on an appropriate history, a physical examination, and appropriate laboratory and radiological investigations. A diagnosis requires prompt treatment, even if the patient is asymptomatic, as adult worms live for many years. Oral praziquantel is used to treat infections caused by all schistosome species.
Full blood count: A routine full blood count (FBC) may show an eosinophilia, which is frequently marked during the acute stage of the infection. Anaemia may also be seen due to chronic blood loss from the urinary or intestinal tract. Patients with hepatosplenic schistosomiasis may have a thrombocytopaenia secondary to splenic sequestration.
Urine dipstick: S. haematobium infections are usually associated with haematuria on dipstick testing.
Microscopy: Demonstration of parasite eggs in stool or urine is the gold standard test for diagnosing schistosomiasis and is required for species identifi cation and determining the intensity of infection. However, the sensitivity may be low, especially with light infections, and it takes approximately six weeks for eggs to be detected after the initial infection. S. haematobium eggs are usually found in urine, but may also be present in stool. Urine should be collected between 10:00 and 14:00 when maximal egg excretion occurs.