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This article provides an overview of helminthic infections, including their classification, clinical features, and laboratory diagnosis. It focuses on specific types of infections, such as ascariasis, hookworms, and strongyloidiasis.
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به نام خدا Helminthic infections دکتر اقازاده
General aspect: • Worldwide more than 2 billion people are infected with helminthes. • Classification helminthes of : • 1. Nematodes (roundworm) • Tissue nematodes • Intestinal nematodes • 2. Platy helminthes: • Trematodes • Cstodes
Intestinal Nematodes • Ascariasis (1) • Causal Agents: • Ascaris lumbricoidesis the most common and the largest nematode ( giant roundworm ) parasitizing the human intestine. (Adult females: 20 to 35 cm; adult male: 15 to 30 cm.)
Geographic Distribution: • Worldwide distribution. • Highest prevalence in tropical and subtropical regions, and areas with inadequate sanitation.
Clinical Features: • adult worms usually cause no acute symptoms. • High worm burdens may cause abdominal pain and intestinal obstruction. • Migrating adult worms may cause symptomatic occlusion of the biliary tract or oral expulsion. • During the lung phase of larval migration, pulmonary symptoms can occur (cough, dyspnea, hemoptysis, eosinophilic pneumonitis - Loeffler’s syndrome).
Laboratory Diagnosis: • Microscopic identification of eggs in the stool is the most common method for diagnosing intestinal ascariasis. Where concentration procedures are not available, a direct wet mount examination of the specimen is adequate fore detecting moderate to heavy infections. • Larvae can be identified in sputum or gastric aspirate during the pulmonary migration phase. • Adult worms are occasionally passed in the stool or through the mouth or nose and are recognizable by their macroscopic characteristics.
Below are several Ascaris eggs seen in wet mounts. Diagnostic characteristics: • Fertilized eggs are rounded, thick shell, external mammillated layer Size: 60 µm in diameter when spherical, and up to 75 µm when ovoid. • Unfertilized eggs are elongated and larger (up to • 90 µm in length); their shell is thinner; and their • mammillated layer is more variable Unfertilized and fertilized eggs (left and right, respectively). Fertilized Ascaris egg, still at the unicellular stage.Eggs are normally at this stage when passed in the stool.Complete development of the larva requires 18 days under favorabl Egg containing a larva, which will be infective if ingested. Diagnostic characteristics: tapered ends; length 15 to 35 cm. This worm is a female(size and genital girdle ) Larva hatching from an egg
Treatment: • The drugs of choice for treatment of ascariasis are: • - Albendazole(400mg once), • - Mebendazole(500 mg once or 100mg BID for 3 days), • - pyrantel pamoate(11mg/kg once; maximum 1g – safe in pregnancy).
Hookworms • Causal Agent: • - The human hookworms include two nematodes : • Ancylostoma duodenale • Necator americanus • - A smaller group of hookworms infecting animals can invade and parasitize humans (A. ceylanicum) or can penetrate the human skin (causing cutaneous larva migrans), but do not develop any further (A. braziliense, Uncinaria stenocephala).
Geographic Distribution: • - The second most common human helminthic infection • - Worldwide distribution, mostly in areas with moist, warm climate. Both N. americanus and A. duodenale are found in Africa, Asia and the Americas. Necator americanus predominates in the Americas and Australia, while only A. duodenale is found in the Middle East, North Africa and southern Europe.
Clinical Features: • - Iron deficiency anemia (caused by blood loss at the site of intestinal attachment of the adult worms) is the most common symptom of hookworm infection, and can be accompanied by cardiac complications. • - Gastrointestinal and nutritional/metabolic symptoms can also occur. • - In addition, local skin manifestations ("ground itch") can occur during penetration by the filariform (L3) larvae, • - and respiratory symptoms can be observed during pulmonary migration of the larvae.
Laboratory Diagnosis: • - Microscopic identification of eggs in the stool is the most common method for diagnosing hookworm infection.
Treatment: • - In countries where hookworm is common and reinfection is likely, light infections are often not treated. • Albendazole (400mg once). Mebendazole (500mg once). or pyrantel pamoate(11mg/kg for 3 days)
Strongyloidiasis • Causal Agent: • Strongyloid Stercolaris • Other Strongyloides include S. fülleborni, which infects chimpanzees and baboons and may produce limited infections in humans.
Geographic Distribution: • Tropical and subtropical areas, but cases also occur in temperate areas • More frequently found in rural areas, institutional settings, and lower socio-economic groups.
Clinical Features: • Frequently asymptomatic. • Pulmonary symptoms (including Loeffler’s syndrome) can occur during pulmonary migration of the filariform larvae. • Dermatologic manifestations include urticarial rashes in the buttocks and wrist areas. • Disseminated strongyloidiasis occurs in immunosuppressed patients, can present with abdominal pain, distension, shock, pulmonary and neurologic complications and septicemia, and is potentially fatal. • Blood eosinophilia is generally present during the acute and chronic stages, but may be absent with dissemination.
Laboratory Diagnosis: • Microscopic identification of larvae ( rhabditiform and occasionally filariform) in the stool or duodenal fluid. • Examination of serial samples may be necessary, and not always sufficient, because stool examination is relatively insensitive. • The duodenal fluid can be examined using techniques such as the Enterotest string or duodenal aspiration. • Larvae may be detected in sputum from patients with disseminated strongyloidiasis.
Treatment: The drug of choice for the treatment of uncomplicated strongyloidiasis is : Ivermectin(200μg/kg daily for 1 or 2 days), Thiabendazole (25 mg/Kg bid 2days) Albendazole(400mg daily for 3 days repeated at 2 weeks), All patients are at risk of disseminated strongyloidiasis and should be treated.
Enterobiasis • Causal Agent: • Enterobiusvermicularis (previously Oxyuris vermicularis) also called human pinworm. (Adult females: 8 to 13 mm, adult male: 2 to 5 mm.) Humans are considered to be the only hosts of E. vermicularis. A second species • , Enterobius gregorii, has been described and reported from Europe, Africa, and Asia. For all practical purposes, the morphology, life cycle, clinical presentation, and treatment of E. gregorii is identical to E. vermicularis.
Geographic Distribution : • Worldwide, with infections more frequent in school- or preschool- children and in crowded conditions. Enterobiasis appears to be more common in temperate than tropical countries. • Clinical Features: • Enterobiasis is frequently asymptomatic. • The most typical symptom is perianal pruritus, especially at night, which may lead to excoriations and bacterial superinfection. • Occasionally, invasion of the female genital tract with vulvovaginitis and pelvic or peritoneal granulomas can occur. • Other symptoms include anorexia, irritability, and abdominal pain.
Laboratory Diagnosis: • Scotch test", cellulose-tape slide test) on the perianal skin and then examining the tape placed on a slide. • Anal swabs or "Swube tubes" can also be used. Eggs can also be found, but less frequently, in the stool, and occasionally are encountered in the urine or vaginal smears. • Adult worms are also diagnostic, when found in the perianal area, or during ano-rectal or vaginal examinations.
Laboratory Diagnosis: Enterobius eggs on cellulose tape prep. Eggs measure 50 to 60 µm by 20 to 3 µm. Anterior end of Enterobius vermicularis adult worm.
Treatment: • - Mebendazole 100 mg once daily(single dose) • Albendazole(400mg once) • pyrantel pamoate(11mg/kg once; maximum 1g -Susp . 250 mg/ 5 ml,Tab. 125 mg– safe in pregnancy) • PYRVINIUM PAMOATE (Coated Tab. 50 mg, Susp. 50 mg / 5 ml) • Measures to prevent reinfection, such as personal hygiene and laundering of bedding, should be discussed and implemented in cases where infection affects other household members.
Tissue Nematodes • Angiostrongylus Cantonensis • Dracunculiasis • Trichinella Spiralis
Angiostrongyliasis • Causal Agent: • The nematode (roundworm) Angiostrongylus cantonensis, the rat lungworm, is the most common cause of human eosinophilic meningitis,
Angiostrongyliasis • Geographic Distribution: • Most cases of eosinophilic meningitis have been reported from Southeast Asia and the Pacific Basin, although the infection is spreading to many other areas of the world, including Africa and the Caribbean. Abdominal angiostrongyliasis has been reported from Costa Rica, and occurs most commonly in young children. • Clinical Manifestations • -eosinophilic meningitis Symptoms include severe headaches, nausea, vomiting, neck stiffness, seizures, and neurologic abnormalities. Occasionally, ocular invasion occurs. Eosinophilia is present in most of cases. Most patients recover fully. • Abdominal angiostrongyliasis mimics appendicitis, with eosinophilia.
Laboratory Diagnosis: • In eosinophilic meningitis the cerebrospinal fluid (CSF) is abnormal (elevated pressure, proteins, and leukocytes; eosinophilia). On rare occasions, larvae have been found in the CSF. • In abdominal angiostrongyliasis, eggs and larvae can be identified in the tissues removed at surgery. • Treatment: • No drug has proven to be effective for the treatment of A. cantonensis or A. costaricensis infections. Relief of symptoms for A. cantonensis infections can be achieved by the use of analgesics, corticosteroids, and careful removal of the cerebral spinal fluid at frequent intervals.
Trichinellosis • Etiology • Epidemiology • Life cycle • Clinical Manifestation • Laboratory Finding • Treatment
Dracunculiasis Causal Agent: • guinea worm disease is caused by the nematode (roundworm) Dracunculus medinensis • Geographic Distribution: An ongoing eradication campaign has dramatically reduced the incidence of dracunculiasis, which is now restricted to rural, isolated areas in a narrow belt of African countries and Yemen.
Dracunculiasis • Clinical Features: • The clinical manifestations are localized but incapacitating. The worm emerges as a whitish filament (duration of emergence: 1 to 3 weeks) in the center of a painful ulcer, accompanied by inflammation and frequently by secondary bacterial infection.
Dracunculiasis • Laboratory Diagnosis: The clinical presentation of dracunculiasis is so typical, and well known to the local population, that it does not need laboratory confirmation. In addition, the disease occurs in areas where such confirmation is unlikely to be available. Examination of the fluid discharged by the worm can show rhabditiform larvae. No serologic test is available. • Treatment:Local cleansing of the lesion and local application of antibiotics, if indicated because of bacterial superinfection. Mechanical, progressive extraction of the worm over a period of several days. No curative antihelminthic treatment is available.
Trematodes • Blood Flukes • Liver Flukes • Intestinal Flukes • Lung Flukes
Blood Flukes (Schistosomiasis) • S .Mansomi • S .Intercalatum • S .Hematubium • S .Japonicum • S .Mekongi
Epidemiology • S .Mansoni • Africa .SousAmerica .Middle East • S .Japonicum • China .Philippines .Indonesia • S .Intercalatum • West Africa • S .Mekongi • Southeast Asia • S .Haematobium • Africa .Middle East
Clinical Manifestation • Cercarial Dermatitis • Acute Schistosomiasis- Katayama Fever • Chronic Schistosomiasis
Cercarial Dermatitis • Dependent to species .Intensity of Infection and host factors • Most often by S .mansoni &S .japonicum • 2-3 days after invasion (swimmer itch) • Self- limiting entity
Acute Schistosomiasis(Katayama Fever) • 4-8 wks after skin invasion • Fever .lymphadenopathy . Hepato- splenomegaly . Eosinophilia . • Generally benign • Death occasionally reported in heavy exposure
Chronic Schistosomiasis • Intestinal & Hepatosplenic Diseases : • S . japonicum .S.mansoni .S.intecalatum . S .mekonky • Intestinal diseases : • Colicky abdominal pain .Bloody diarrhea .Colonicpolyposis • Hepatosplenic Diseases : • 15-20 % of infected patients • Portal hypertension • Cirrhosis • Urinary tract Diseases • S.haematobium • Hemturia .Dysuria .Bladder granoloma .Hydronephrosis Bladder CA • CNS Schistosomiasis • Pulmonary Schistosomiasis
Liver Flukes • Fasciola Hepatica • Clonorchis Sinensis
Fascioliasis • Causal Agent: • The trematodes Fasciola hepatica (the sheep liver fluke) and Fasciola gigantica, parasites of herbivores that can infect humans accidentally. • Geographic Distribution: • Fascioliasis occurs worldwide. Human infections with F. hepatica are found in areas where sheep and cattle are raised, and where humans consume raw watercress, including Europe, the Middle East, and Asia. Infections with F. gigantica have been reported, more rarely, in Asia, Africa, and Hawaii.
