Giardiasis etiology and management
Giardiasis etiology and management
Giardiasis etiology and management
Aetiology The parasite is a flagellate, pear-shaped protozoan which is found in the lumen of the upper small intestine.Some trophozoites encyst, to be passed in the faeces.The cyst is infective and can survive for 2 months at 8C inwater. It is resistant to normal levels of chlorination, andsand filtration is used to clear municipal water supplies of this and other parasites. The parasite can now be grown inculture.
Distribution and incidenceThe distribution is worldwide, although it is more commonin the tropics. It is endemic in the countries of easternEurope. Epidemics have occurred at daycare nurseries,on cruise ships and in towns in the USA. Giardiasis hasoccurred in children in inner-city populations in Britain,and can cause diarrhoea in the elderly.
Transmission and epidemiologySpread is by the faecal-oral route. As few as 10 cysts willcause infection, and 1000 cysts consistently cause infection.Contaminated food and water are vehicles of infection.Person-to-person spread is common in childhood, particularlywhen children are not toilet trained. Mothers areoften infected by changing the nappies of an infected child.Any circumstances in which standards of personal andpublic hygiene (such as water treatment) are low lead totransmission.In the tropics children are most often infected, althoughboth indigenous and visiting adults can develop symptomaticdisease. Male homosexuals and retarded childrenare other risk groups. Hypogammaglobulinaemia and reduced gastric acid secretion are host factors that increase susceptibility.
Pathology and pathogenesis The main abnormalities relate to the function and morphologyof the upper small intestine. Markedly symptomaticpatients have impaired absorption of fat, o-xyloseand vitamin B12, and lactose maldigestion. The jejunalmucosa is abnormal, with a ridged or convoluted mucosa,reduced villous height with increased crypt depth, and anincreased infiltrate of plasma cells in the lamina propria.Subtotal villous atrophy may occur with giardiasis but isuncommon. Patients with mild or no symptoms havenormal jejunal morphology and function. Lactose maldigestionmay be present.The pathogenesis is not well understood. The parasiteitself may damage the enterocyte surface membrane toimpair function and fat digestion intraluminally. Jejunalcolonization with bacteria may also contribute to some ofthe mucosal dysfunction. Antigiardia IgA from the mucosaand in bile may control parasite numbers.
Clinical features The incubation period is usually about 10-14 days, althoughit can be much longer. Many patients with giardiasis areasymptomatic or have minimal bowel upset. Acute giardiasisis characterized by the sudden onset of anorexia, nausea,abdominal distension, discomfort and diarrhoea withfrequent yellow, offensive, frothy stools by day and night.Lethargy is often severe and weight loss is usual. Afterabout 3 weeks there may be the beginnings of spontaneousimprovement. This may progress to complete resolutionover a month, but some patients remain mildly symptomatic,often because of continuing lactose intolerance.Some patients remain markedly symptomatic and fail toregain lost weight or continue to lose weight. The abdomenis distended and bowel sounds are prominent. The stoolsare yellow and offensive. Testing confirms malabsorption.Children are occasionally brought to medical attentionbecause of failure to thrive. Giardiasis has been reportedas a cause of chronic diarrhoea in elderly persons in theUK. It is not a major cause of diarrhoea in AIDS.
Diagnosis Diagnosis depends on finding the parasites. Stool microscopyshows cysts in most patients, although examinationof several samples may be necessary. Trophozoites may befound in diarrhoeal stools. When the parasite is not foundand symptoms are marked, investigation of intestinal morphologyand function is indicated. Jejunal juice and jejunalmucus obtained at the time of biopsy can be examined fortrophozoites. Giardia may be seen in the intervillous spaceof the sections of the biopsy. Giardia antigens can bedetected in stools by immunological techniques.
Management Tinidazole is effective and can be given in a single dose of2g (50mg/kg) which can be repeated after 1 week. Acheaper alternative is metronidazole, 2g as a single doseon 3 successive days. A second course after 10 days mayincrease the cure rate. Both drugs cause nausea and ametallic taste in the mouth, and have a disulfiram-likeinteraction with alcohol.Asymptomatic giardiasis in pregnancy need not betreated. When there is symptomatic disease in pregnancyassociated with weight loss or failure to gain weight, thenmetronidazole (200 mg three times a day for 10 days) maybe given.Symptoms due to giardiasis improve rapidly after treatment.Dietary measures are sometimes helpful for continuinggut symptoms. Avoidance of alcohol, spicy foods andlactose is often helpful. Repeat stool microscopy 6-8 weeksafter treatment provides a test of cure. Abnormalities inintestinal structure and function disappear over 6-12weeks after treatment.
Prevention and control Travellers in areas where the tap water is not safe to drinkshould avoid salads, uncooked foods, unpeeled fruits andice cubes in drinks. Sterilization of drinking water with 2%tincture of iodine (0.5 mL/L of water and allow to stand for30 minutes) may be necessary. Treatment of asymptomaticcyst excreters is worthwhile, particularly in a non-endemicarea, as it reduces the risk of transmission to others.
Cryptosporidiosis clinical features and management Why absence management is important African trypanosomiasis clinical features pathology and management Knowledge and Data Management Services An Asbestos Management Plan Can Save Lives How to Choose a Content Management System? Find Solution of your debt crisis with debt management Organizing Your Employees through Workforce Management Why do Project Management Training Meet the Challenges of the Future Through Change Management Training Get a Reliable Softswitch and VoIP Billing Management Service Provider for More Savings and Efficiency American trypanosomiasis aetiology and management Ascariasis aetiology and management