Giardia lamblia (Giardiasis) a parasite .pptx

This is a presentation on Giardia lamblia

1. GIARDIA Presenter Olympia G odbless Machange Moderator Dr. Lwidiko April 2022 Presenter Olympia godbless Machange Moderator Prof. ngassala April 2022

2. Introduction There are six recognized species of Giardia, only one is known to infect humans the Giardia lamblia . Members have an adhesive disc on the ventral durface Don’t possess mitochondria or Golgi apparatus or any organelles for energy metabolism They are differentiated by the overall shape , dimensions of trophozoite body and distinctive shapes of the median bodies . Morphological subtype of Giardia, G. agilis from amphibians, G. muris from mice and G. intestinalis from human and some other vertebrates,

3. Other subtype, G. psittaci isolated from a budgerigar and G. ardeae from the great blue heron. These can be distinguished from the other subtypes by an absence of the ventrolateral flange in the former and a single (rather than a double) caudal flagellum in the latter.

4. Classification Kingdom: Protista Phylum: Metamonada Is a large group pf anaerobic flagellate protozoa of uncertain composition (derived from variety of ancestors i.e. polyphyletic) Lack mitochondria and Golgi apparatus have remnants called mitosomes Have four pair of flagella and Basal bodies arranged in association with their nucleus forming a structure called karyomatigont . Subphylum: Mastigophora Order: Diplomonadida Genus: Giardia Species: G. lamblia , G . muris , G.agilis , G. microti , G. psittaci , G. ardeae

5. Giardia lamblia Giardia lamblia is also known as G. duodenalis or G. intestinalis or Lamblia intestinalis S ingle-celled flagellate protozoan parasite (most common of all intestinal flagellates) It causes both epidemic and sporadic diarrhea disease A well etiology of waterborne, foodborne diarrhea, daycare center outbreak and international travelers The infections does not cause invasive damage to the gastrointestinal tract.

6. Introduction cont … Found in human duodenum and upper small intestine(jejunum) sometimes stomach, ileum and colon become infected Many are asymptomatic carriers but some develop acute form of enteritis (giardiasis) manifested as profuse watery diarrhea Occurs worldwide and may infect up to a third of the population in developing countries. They are also found in other mammals which serve to make the disease difficult to eradicate. 2.5 million people annually are infected in USA alone

7. History Giardia lamblia was first protozoan to be discovered 1681 by Van Leeuwenhock in his own diarrhea sample The first known description of G. lamblia occurred in the stool of pediatric patient in 1859. It is named Giardia after Professor Giard of Paris and lamblia after Professor Lambl of Prague who gave a detailed description of the parasite

8. Morphology Have two morphological stages Trophozoites and Cysts

9. Trophozoites Pear or teardrop shaped , with a broad anterior and much attenuated posterior  Range between 9 - 21 μm in length and 5 - 15 μm in width It is also relatively flattened, with a large sucking disk on the anterior ventral side, for attachment to the mucosa of the host. 

10. Trophozoites Has two nuclei and four pairs of flagella (anterior, caudal, posterior and ventral ) It is bilaterally symmetrical with an axostyle evenly dividing it in the middle Two curved structures, called median bodies, lie parallel to each other, it cross the axoneme at slight angles, giving the appearance of a smiling mouth. The ventral flagella work as a ‘pump’ that removes fluid from underneath the adhesive discs and facilitate the removal of nutrients from the underlying host mucosa

11. It lives in the duodenum and upper part of the jejunum attached by means of the sucking disc to the epithelial cells of the villi and crypts feeding by pinocytosis . Attach to the surface of epithelium and overlaying mucus (not invade tissue ) The trophozoite retracts its flagella into the axonemes which remain as curved bristles in the cyst . The trophozoites as they pass down the colon develop into cysts

12. Cysts Oval shape 8-12 µm long and 7-10 µm wide surrounded by a tough hyaline cyst wall Matured cysts have 4 nuclei (concentrated at one end) Have several prominent anoxemes which provide internal support Flagella shortened and retracted within cyst (microtubules that constitutes the core of flagella) Cysts are passed in stools and remain viable in soil and water for several weeks. Within half an hour of ingestion, the cyst hatches out into two trophozoites multiply by binary fission and colonize the duodenum.

13. Life cycle

14. Life cycle Is direct in one host Infection occurs by the ingestion of cysts in contaminated water, food, or hands or fomites and by person to person In the small intestine, excystation releases trophozoites Each cyst produces 2 trophozoites Trophozoites multiply by binary fission remaining in the lumen where they can be free or attached to the mucosa by  a ventral sucking disk . Encystation occurs as the parasites transit toward the colon .

15. Life cycle Both cysts and trophozoites can be found in the feces The cyst is the stage found most commonly in formed feces and can survive several months in cold water. Trophozoites are found in the diarrheal stools and are destroyed outside the body

16. Pathogenesis G. lamblia inhabits in the duodenum and jejunum Many species of mammals as well as humans act as reservoirs. Trophozoites are attached to the mucosa surface by sucker, reproduce by binary fission Mechanical blockage of the intestinal mucosa, competition for nutrients Histology shortening of the microvilli, elongation of crypts, and damaging the brush border of the absorptive cells The trophozoite causes inflammation of the duodenal mucosa, leading to malabsorption of protein and fat.

17. Pathogenesis cont … Diarrhea, abdominal pain, bloating, nausea and vomiting Mild  steatorrhea  (passage of yellowish greasy stools in which there is an excess of fat) Risk groups: Hikers who drink untreated stream water Male homosexuals/ oral-anal sex Children in daycare centers IgA deficiency greatly predisposes to symptomatic infection Approximately half of those who are infected are asymptomatic carriers who continue to excrete the cyst for years.

18. Clinical symptoms Incubation period ranges between 1 to 3 weeks after infection Individual may suffer either an acute or chronic diarrhea accompanied by: Severe abdominal discomfort and cramps Water and smell diarrhea (excessive may lead to dehydration) Bloating and flatulence Anorexia sometimes accompanied by nausea Vitamin deficiency particularly the fat-soluble vitamin A, D, E, K along with folic acid

19. Clinical symptoms cont … Weight loss and malabsorption syndrome as well as steatorrhea (fatty stool) may occur. In children, severe giardiasis might delay physical and mental growth, slow development, and cause malnutrition and sometimes death

20. Laboratory Diagnosis Macroscopic : yellowish greasy stools Microscopic examination of stool Enzyme immunoassays for antigen or molecular test for parasite DNA in stool String test ( Entero -test): Sampling of upper intestinal contents can also yield trophozoites but seldom not necessary Polymerase Chain Reaction (PCR )  can be used to identify the subtypes of  Giardia lamblia.

21. Laboratory Diagnosis Microscopic examination of stool Fresh diarrheic specimen:  The cysts and trophozoites can be found in diarrhoeal stools. Generally trophozoites are difficult to detect as they attach themselves to the wall of the intestine. Concentration by formalin ethyl acetate or zinc sulphate centrifugal floatation is useful when the cysts are sparse . Formed fecal specimen: Look for the  Giardia lamblia  cyst .

22. Laboratory Diagnosis Parasite excretion is intermittent and at low levels during chronic infections thus microscopic diagnosis may require repeated stool examination (at least 3 exams (one every other day) before judge negative) ELISA and immunochromatographic strip tests have been developed for detection, of giardia antigens in faeces , but are not in routine use. Enzyme immunoassay to detect parasite antigen in stool is more sensitive than microscopic examination. Antibody demonstration is not useful in diagnosis

23. Laboratory Diagnosis String test ( Entero -test): Duodenal aspiration may sometimes be necessary to demonstrate the parasite in cases in which biliary symptoms predominate. Swallowing a weighted piece of string (gelatin capsule) until it reaches a duodenum. Trophozoites adhere to the string and can be visualized after the withdrawal of the string After 2 hours, the thread is withdrawn, placed in saline and mechanically shaken. The centrifuged deposit of the saline is examined for giardia

24. Treatment Only symptomatic cases need treatment. Drug of choice: Tinidazole , Metronidazole or Nitazoxanide Treatment failure and resistance can occur in any of them. Metronidazole side effect include nausea and headaches Metronidazole and tinidazole should not be given to pregnant women( paromomycin ) In terms of GIT adverse effects tinidazole is generally better tolerated than metronidazole.

25. Treatment cont … Furazolidone , quinacrine or albendazole are rarely used because of potential toxicity, lower efficacy Furazolidone is slower in action, but is preferred in children as it has fewer adverse effects Fluid replacement and rehydration

26. Epidemiology Giardiasis is one of the most common parasitic diseases of humans in the world especially in children Overall prevalence may be 1-30% but can reach 70% in unsanitary environment At least 500,000 new cases each year and is considered to be re-emerging infection. Many of those infected are asymptomatic carriers of the parasite which affects 200 mil people in Africa, Asia, Central and South America. Epidemics of giardiasis have been reported in number of occasions

27. Epidemiology Global travel contributes to the transmission due to exposure to endemic areas. Ingestion of food and water contaminated with cyst is most common mode of infection But direct person to person transmission may occur in children, male homosexuals and mentally ill Is attributed more frequently as a cause of outbreaks of diarrhea among young children in daycares or following contamination of domestic water supplies

28. Epidemiology Enhanced susceptibility to giardiasis is associated with blood group A, achlorhydria , use of cannabis, chronic pancreatitis, malnutrition and immune defects such as IgA deficiency and hypogammaglobulinaemia . HIV infection has not been associated with increased risk of giardiasis. Cats , dogs, cattle, sheep and many wild animals have been found naturally infected due to water sources contaminated by such animals but are not considered to be responsible for human infection

29. Prevention and control Preventive measures through WASH Proper disposal of human feces and avoid open defecation Proper use of latrine and hand washing with soap and running water after using the latrine Wash hand individually with soap and running water before meals Enforce hygienic measures in handling food, vegetables, fruits and drinking water Health education and awareness campaign on proper sanitation and hygienic habits

30. Construction of proper fecal disposal facilities and installation of public safe water supply to prevent and control transmission Environmental hygiene by protection of food from cockroaches and flies will prevent the spread of eggs and cysts of parasites Investigation and treatment of patients

31. References Manson’s Tropical Diseases, 22 nd edition, Edited by Gordon & C.Cook , W.B Saunders London Textbook of medical parasitology, sixth edition CK Jayaram Paniker . 2007. Modern parasitology: A textbook of parasitology, 2 nd edition F. E. G. Cox (editor) Parasitology : an integrated approach Alan Gunn and Sarah J. Pitt . 2012. Parasitology for medical and clinical laboratory professionals. John W. Ridley , 2012

32. Thank you!