|Keywords (Extracted from title, table of contents and abstract of thesis)
giardia lambia, diarrhoeal disease, diarrhoea, ehistolytica, b.hominis, aeromonas spp., salmonella spp.. vibrio spp., plesiomonas spp., immunofluorescence test, e.coli, pseudomonas spp., a.faecalis, enterobacter spp., klebsiella spp., acetinobacter spp., giardia
INDICENCE, PATHOGENESIS AND SERODIAGNOSIS OF GIARDIA LAMBIA INFECTION IN KARACHI, PAKISTAN.
Diarrhoeal disease is a main cause of morbidity and mortality in our population. The causative agents of diarrhoea are mainly bacteria consisting of a variety of bacterial species. As no comprehensive study regarding the role of parasites mainly Giardia lamblia was present, this study was done to determine the incidence. pathogenesis. serodiagnosis and response to drug therapy in patients with G.lamblia infection. Out of 1000 adult patients who reported at Pakistan Medical Research Council, Research Centre Karachi, G.lamblia was detected in 12 % of cases. Incidence of G.lamblia among males and females was 57 % and 43 % respectively. Infection was found to be more in 60-69 years age group. G.lamblia as a single pathogen was present in 87.5 % of cases, two pathogens were found in 11.6 % ( E his/olvtica and Bhominis ) and 0.8 % cases had infection with three pathogens ( G.lamblia, E. histolytica and B.hominis). G.lamblia was also found in combination with pathogenic bacteria (21%) consisting of Aeromonas spp., Salmonella spp.. Vibrio spp. and Plesiomonas spp. Among the controls G.lamblia was present in 3.3% and E. histolyticain 13.3% of healthy subjects. Prevalence of G.lamblia infection was found to be more in malnourished patients from lower socioeconomic status No significant seasonal variation was present except more cases reported during July to September. G.lamblia infection is transmitted through water, food, person to person or animals. As contaminated water is the most common source of G.lamblia infection, bacteriological and protozoal study of domestic water supply was done. Faecal pollution of water was detected in lower socioeconomic group and most patients included in our study came from those areas. The bacterial pathogens isolated in domestic water supply were E.eoli, Pseudomonas spp., A.faeealis, Enterobaeter spp., Klebsiella spp. And Aeetinobacter spp. Relationship of blood groups with G.lamblia infection is controversial. Blood groups of 120 patients with G.lamb/ia infection were determined by ABO blood group system. Blood group B was found in 39.1 % and group A in 29.1% while group 0 in 21.6 % and group AB in 10.%. Among 48 controls blood group A was present in 33.3%, group B in 31.2%, group 0 in 31.2 % and AB in 4.1% No significant relationship of any particular blood group or hematological changes were observed in giardiasis.
Diagnosis of G.lamblia infection was determined by different methods. Apart from direct microscopy and concentration method' for the detection of G.lamblia, Immunofluorescence test was also used for the detection of G.lamblia antigen in faecal samples. Immunofluorescence test appears to be more sensitive than other methods of diagnosis as 16 % more cases negative by direct microscopy were positive by this method. Cross reactivity of G./amblia with other pathogens was tested and found to be negative. Detection of G.lamblia trophozoites in duodenal fluid is another method used for diagnosis of G.lamblia infection. 16 % of patients diagnosed positive by direct microscopy of stool were positive for G.lamblia in duodenal aspirates.
Mechanism of pathogenesis of G.lamblia infection is not clear. Role of isoenzymes in G./amb/ia infection is controversial. Differences in isoenzyme pattern of G.lamblia strains may be present in symptomatic and asymptomatic subjects. To establish the role of isoenzymes in G.lamb/ia infection, we determined Lactate dehydrogenase (LDH) 5isoenzyme by Polyacrylamide Gel Electrophoresis (PAGE). One patient having large number of trophozoites in duodenal fluid was LOH positive which might be due to some metabolites produced by the parasites Or the patient might be suffering from some other disease.
Role of immune response was also studied in patients with G.lamb/ia infection. Giardia specific serum immunoglobulins were determined by dot ELISA. Dot ELISA was developed in our laboratory and this is the first time that it was used for the detection of Giardia antibodies. Immunofluorescence test for the detection of Giardia antibody was also developed in our laboratory and can be used as a diagnostic test. IgM was present in . 25 % patients with serum level of 1 :200 but absent in controls. IgG was present in 16 % patients and 7 % controls and IgA in 8 % patients and 17 % controls Decreased level of IgA in our patients is important as it indicates that mucosal surface IgA plays a role in G.lamb/ia infection and due to its suppression, G./amb/ia are able to colonize and multiply in the intestine. Difference in immunoglobulin levels between patients and controls was significant. Presence of Giardia specific IgG and IgA in controls indicate that as giardiasis is common in our population these subjects might be having subclinical infection due to exposure to contaminated environmental conditions which resulted in antibody production, however their stools were negative.
Non specific immune response is important in controlling infection. Total serum immunoglobulin (lgM, IgG and IgA) were determined by Radial Immunodiffusion method. IgM and IgG were elevated in patients and IgA in controls. Difference in immunoglobulin between patients and controls was significant. IgE determined by ELISA method was found to be similar in both the groups indicating that giardiasis does not produce any 6allergic reaction. Decreased levels of Giardia specific and total immunoglobulin were found in chronic carriers. Role of Cytokines in the pathogenesis of giardiasis were determined. Cytokines or Interleukins are a group of hormone like substances through which cells of the immune system communicate and they act on other cells of the immune system to regulate their function Interleukins were estimated to determine whether it has any role in giardiasis. This is the first time that Cytokine levels were determined in giardiasis. Cytokines have been found to be elevated in patients with Ehistolytica infection. Serum Interieukin level IL-4, IL-2, IL-10 were determined by ELISA. IL-4 was found in patients and controls with a mean value of 222 pglml and 115 pmlml respectively. IL -2 and IL-10 were present in few of the patients. Serum Tumor Necrosis factor (TNF) alpha was absent in 13 patients suffering from giardiasis but present in 2/14 controls with a mean value of 75 pg 1m!. Results indicate that as IL-4 regulates inflfunmation it appears to have some relationship with giardiasis. TNF being an inflammatory mediator was not detected in our patients as Glamblia being a non invasive parasite, did not produce any inflammatory reaction Various drugs have been used for the treatment of G.lamblia infection. Response of our patients to treatment with Secnidazole, Metronidazole and Albendazole was determined. Among 78 patients suffering from giardiasis, 69 % had faecal samples negative for parasites by direct microscopy and improvement in clinical symptoms. Secnidazole, a long acting nitroimidazole was used for the first time in our study. It was given as a single dose of 2000 mg and was found to be effective in 90 % of cases. Metronidazole 400 mg for 5 days cured 80 % of cases while Albendazole given as a single dose of 1200 mg 7gave a response of 50 %, Albendazolp. 800 mg given for 3 days gave a slightly better response of 56 %.
Incidence of G./amblia infection Is high in our adult population. For accurate diagnosis, apart from direct microscopy of stools, Immunofluorescence test for the detection of G./amb/ia antigen should be used. For serological diagnosis, dot ELISA and Immunofluorescence test for Giardia antibody detection can be used as diagnostic tests. As mechanism of pathogenesis is not clear, the role of IgA should be emphasized as decreased IgA levels reduces its protective effect against mucosal damage. Cytokines appear to have some relationship and should be further investigated. Drug response indicates Secnidazole as the most effective drug, but resistance to drugs does occur which might be due to resistant G.lamblia strains having different isoenzyme pattern or some other factors which should be investigated.