Microbiology 16 - Trematodes.pdf

Microbiology Parasitology Trematodes Microbiology| Trematodes Contents : Life cycle 5 Pathology and Pathogenesis 10 Signs and Symptoms 14 Diagnosis 19 Treatment 20 Control of infection 21 Microbiology| Trematodes Trematodes or flukes are leaf-like unsegmented flat worms. The most characteristic stru...

Microbiology Parasitology Trematodes Microbiology| Trematodes Contents : Life cycle 5 Pathology and Pathogenesis 10 Signs and Symptoms 14 Diagnosis 19 Treatment 20 Control of infection 21 Microbiology| Trematodes Trematodes or flukes are leaf-like unsegmented flat worms. The most characteristic structures are two suckers (oral and ventral). The body is consist of a mouth surrounded by oral suckers, a pharynx and the esophagus. The anus is absent. Microbiology| Trematodes Trematodes can be classified according to their habitat into: 1. Blood fluke. 2. Intestinal fluke. 3. hepatic fluke. 4. lung fluke. Blood flukes: Schistosoma japonicum, Schis. mansoni and Schis. Haematobium cause water -borne parasitic disease (Schistosomiasis or Bilharziasis). Microbiology| Trematodes Life cycle : The schistosome life cycle is very similar, with the exception that different species differ in the final location where the adult worms prefer to reside within the human body. Adults of S. mansoni inhabit the mesenteric veins of sigmoido-rectal region. S. japonicum inhabit the mesenteric veins of ileo-cecal region. S. haematobium prefer the veins of vesical and pelvic plexuses (urinary tract). Microbiology| Trematodes The adult dioecious (male and female) sexual stage within the definitive host (human). asexual reproductive stage within an intermediate host (snail). After mating of worms in the portal vein when the conjoined couple uses their suckers to ascend the mesenteric vessels against the flow of blood. The female begin releasing eggs. Microbiology| Trematodes These eggs are discharged in: Urine (S. haematobium) faeces (S. mansoni and S. japonicum) In water egg hatch's releasing miracidia (first larval stage). the miracidia eaten by certain snails (intermediate hosts) snails for S. mansoni (Biomphalaria) S. japonicum (Oncomelania) S. Haematobium (Bulinus) Microbiology| Trematodes miracidia develop to a second larval stage (sporocyst stage) then the infectious stage cercariae. The cercariae leave the snail and swim to penetrate a human skin. The cercariae have transformed into schistosomules, which enter the peripheral circulation, where they eventually become adults in the hepatoportal system or venus plexus surrounding the bladder. Note: The transmission of schistosomiasis is NOT person-to-person. S. japonicum final hosts are the man and domestic animals. Microbiology| Trematodes Microbiology| Trematodes Pathology & Pathogenesis : The most significant pathology is associated with the schistosome eggs, not the adult worms. Female schistosomes can lay hundreds or thousands of eggs per day within the venous system. Microbiology| Trematodes When eggs are released, many are swept back into the circulation and lodge in: liver (S. mansoni and S. japonicum) urinary bladder (S. haematobium) other eggs are able to reach the lumen of the intestine and pass out with the feces (S. mansoni and S. japonicum) or urine (S. haematobium). Microbiology| Trematodes A granulomatous reaction surrounds the eggs and leads to fibrosis in the liver with S. mansoni and S. japonicum. In chronic cases, blood flow to the liver is impeded, which leads to portal hypertension, accumulation of ascites in the abdominal cavity, hepatosplenomegaly, and esophageal varices. With S. haematobium infections, there is urinary tract involvement: urethral pain, increased urinary frequency, dysuria, hematuria, and bladder obstruction leading to secondary bacterial infections. Microbiology| Trematodes In travelers to endemic countries, swimmer's itch occurs within an hour after cercariae penetrate the skin, followed by headache, chills, fever, diarrhea, and eosinophilia (known as snail fever or Katayama fever) 2–12 weeks after exposure. The immunological reaction and granuloma formation in the tissues is responsible for the morbidity and mortality of chronic schistosomiasis. Microbiology| Trematodes Signs and Symptoms : Acute Manifestations occur after cercarial penetration. there can be localized pruritus lasting for few hours (swimmers itch) followed by urticarial rash. Most people will be initially asymptomatic after this first stage of infection. In non-immune individuals symptoms of ‘snail fever’ or Katayama syndrome may develop after an incubation period of 1-2 months. Microbiology| Trematodes This syndrome is associated with abrupt onset of fever, often accompanied by headache, shivering, anorexia, myalgia and right upper quadrant pain and less commonly with nausea, vomiting, diarrhea, cough and mild bronchospasm. Some may also develop hypersensitivity reaction to initial egg deposition, in the form of urticaria, generalized pruritus. Microbiology| Trematodes Signs of chronic systemic inflammatory illness may : Persist and weight loss is the rule. Clinical signs include hepatosplenomegaly, diarrhea alternating with constipation and sometimes dysentery-like illness with bloody bowel movements. Eggs in the gut wall induce inflammation, hyperplasia, ulceration, micro abscess formation and polyposis. Microbiology| Trematodes Bilharzia : Many S. haematobium eggs remain trapped in the host tissues and become surrounded by delayed-type hypersensitivity granulomatous inflammation. This inflammation is formed by host lymphocytes, eosinophils and macrophages and ultimately kills and destroys the parasite eggs. The inflammation is associated with scar formation. Microbiology| Trematodes Gradual accumulation of this scar tissue within bladder and ureters can lead to obstruction, resulting in hydronephrosis, bladder calcification, ascending bacterial infection due to urinary reflux and ultimately squamous cell carcinoma of the bladder. Central nervous system disorders can result from eggs passing into the brain, spinal cord and meninges. The resulting inflammation can lead to seizures, spinal cord compression, or hydrocephalus. Microbiology| Trematodes Diagnosis : The detection of ova in fecal or urine smear preparations. Invasive procedures—biopsy material are effective in visualizing eggs when the stool or urine sample testing is negative. serology. S. mansoni S haematobium S japonicum Microbiology| Trematodes Treatment : Praziquantel is active against all Schistosoma species. Praziquantel’s mechanism of action is complex. It is thought to damage the worm’s outer tegument membrane and expose the worm to the body’s immune response, which ultimately results in worm death. No specific therapy is available for the treatment of Katayama syndrome. Antihistamines and corticosteroids may be helpful. Microbiology| Trematodes Control of infection : Eradication of the intermediate snail hosts. Prevention of water pollution with human excreta. Avoidance of swimming in contaminated water. Effective treatment of infected persons.