Blood Flukes 07

Theodor Maximilian Bilharz - a German pathologist working in Egypt in 1851 who found the eggs of Schistosoma haematobium during the course of a post mortem •

•Bilateral

symmetry

•Oral

and ventral suckers •Body covering of a syncytial tegument •Blind-ending

digestive system consisting of mouth, esophagus and bifurcated caeca •Adult

worms tend to be 10-20 mm (0.40.8 in) long and use globins from their hosts' hemoglobin for their

•Penetration

of cercariae causes transient dermatitis (swimmers' itch) •In the bladder, they produce granulomatous lesions, hematuria and sometimes urethral occlusion •In the intestine, they cause polyp formation which, in severe cases, may result in life threatening dysentery.

•In

the liver, the eggs cause periportal fibrosis and portal hypertension resulting in hepatomegaly, splenomegaly and ascites. •Central nervous system and cause headache, disorientation, amnesia and coma •Eggs carried to the heart produce arteriolitis and fibrosis resulting in enlargement and failure of the right ventricle

The swimmer’s itch is due to physical damage to the skin by proteases and other toxic substances secreted by the cercaria. The host develops: -hypersensitivity reactions -collagenase-mediated damage to the vascular endothelium.

S. hematobium eggs in urine (55 to 65 by 110 to 170 micrometers) have an apical spine or knob. S. mansoni eggs in feces (45 to 70 by 115-175 micrometers)  have a spine on the side. S. japonicum eggs (55 to 65 by 70 to 100 micrometers) are more round with a vague spine on the side.

Praziquantel is effective against all species. Contaminated water should be avoided. Control measures include sanitary disposal of sewage and destruction of snails. No vaccine is available.

Site in Host: -primarily in urinary bladder -eggs deposited in the vesical(bladder) plexes and produce lesions in urinary bladder and genitalia Portal of Entry: Skin Source of Infection: Snail Size of Parasite: Ova: huge, up to 180 m Adult: 0.6-2.5 cm in length

Most Common Clinical Symptoms: -inflammatory condition of the bladder leads to progressive changes in bladder. -urethra may be occluded, uretus obstructed, occasionally pelvis of kidney affected. -mechanical and toxic irritation of the eggs and chemical deposits evidently predispose to malignancy.

The ova are initially deposited in the skin which leads to ulceration of the overlaying tissue. Infections are characterized by pronounced acute inflammation, squamous metaplasia, blood and reactive epithelial changes. Granulomas and multinucleated giant cells may be seen.

Laboratory Diagnosis: identification of eggs in the urine Characteristics of Diagnostic Form: -shape: oval-elongate-prominent terminal spine -large size-non-operculate -yellowish-usually a mature miracidium within the egg

S. japonicum worms are yellow or yellow-brown The males of this species are slightly larger than the other Schistosomes and they measure ~ 1.2cm by 0.5 mm The females measure 2cm by 0.4mm By electron microscopy there are no bosses or spines on the dorsal surface of the male, which is ridged and presents a spongy appearance

The oral sucker shows a rim with spines of variable size and sharpness inward and outward from the rim. The ventral sucker possesses many spines which are smaller than in the oral sucker. The ova are about 55 - 85 mm by 40 - 60 mm, oval with a minute lateral spine or knob.

Manifestations include: Abdominal pain Cough Diarrhea Eosinophilia — extremely high eosinophil granulocyte (white blood cell) count. Fever

Hepatosplenomegaly — the enlargement of both the liver and spleen.

the

Genital sores — lesions that increase vulnerability to HIV infection. Lesions caused by Schistosomiasis may continue to be a problem after control of the Schistosomiasis infection itself. Early treatment, especially of children, which is relatively inexpensive, prevents formation of the sores.

Microscopic identification of eggs in stool or urine is the most practical method for diagnosis Eggs can be present in the stool in infections with all Schistosoma species. Detection will be enhanced by centrifugation and examination of the sediment

The therapy of choice is praziquantel, a quinolone derivative.

Prevention is best accomplished by eliminating the water-dwelling snails that are the natural reservoir of the disease. Acrolein, copper sulfate, and niclosamide can be used for this purpose. Recent studies have suggested that snail populations can be controlled by crayfish populations.

The male S. mansoni is approximately 1 cm long (0.6 to 1.4 cm) and is 0.11 cm wide. It is white, and it has a funnelshaped oral sucker at its anterior end followed by a second pediculated sucker. The external part of the worm is composed of a double bilayer

The female has a cylindrical body, longer and thinner than the male (1.2 to 1.6 cm long by 0.016 cm wide). The female parasite is darker, and it looks gray. The darker color is due to the presence of a pigment (hemozoin) in its digestive tube. This pigment is derived from the digestion of blood.

It usually takes four to six weeks from the time of infection for the symptoms to appear The first symptom of the disease may be a general ill feeling. Within twelve hours of infection, an individual may complain of a tingling sensation or light rash, commonly referred to as "swimmer's itch“. The rash that may develop can mimic scabies and other types of rashes. Other symptoms can occur two to ten weeks later and can include fever, aching, cough, diarrhea, or gland

Schistosome eggs, which may become lodged within the hosts tissues, are the major cause of pathology in schistosomiasis. Some of the deposited eggs reach the outside environment by passing through the wall of the intestine; the rest are swept into the circulation and are filtered out in the periportal tracts of the liver resulting in periportal f ibrosis. Onset of egg laying in humans is sometimes associated with an onset of fever (Katayama fever).

Diagnosis of infection is confirmed by the identification of eggs in stools. The diagnosis is improved by the utilization of the Kato-Katz technique (a semi- quantitative stool examination technique).

Currently there are two drugs available, Praziquantel and Oxamniquine, for the treatment