Rakhshanda Baqai  ( Pakistan Medical Research Council, Research Centre, Jinnah Postgraduate Medical Centre and Immunology and Infectious Disease Research Lab, Karachi. )
Shahana U. Kazmi  ( Department of Microbiology, University of Karachi, Karachi. )
Sarwar J. Zuberi  ( Pakistan Medical Research Council, Research Centre, Jinnah Postgraduate Medical Centre and Immunology and Infectious Disease Research Lab, Karachi. )

Giardiasis is a common disease of the small intestine of man caused by the flagellated protozoan parasite. The influence of host immunity on infection and on modulating its clinical course remains uncertain. Infection in some hosts may be short lived and spontaneously self-limited¹, while in others it may result in prolonged debilitating illness². Though specific antibody msponse occurs in the host following G. lamblia infection, the immune alteration especially at the gut level which allows the parasite to colonize, multiply and damage the brush border membrane are ill understood. Local immune factors responsible for elimination of parasite are not clear³. Susceptibility to giardiasis has been closely miated to the immunological status of the host⁴. Increased incidence of giardiasis has been reported in adults having low levels of immunoglobulins^5-7. This study was done to determine serum immunoglobulin levels in giardiasis.

Sixty-six adults (males 38, females 28) reporting with abdominal pain and persistent diarrhoea and diagnosed on stool examination positive for 0. lamblia were included in the study.
The control group consisted of 34 apparently healthy subjects (Males 23, Females 11) with stool negative for parasite. Blood samples were collected and serum samples stored at -20°C. Total serum immunoglobulins IgM, IgG and IgA were determined by Radial Immunodiffusion method (Binding Site Ltd., U.K.) and total serum IgE by ELISA method (Melotec IgE kit). Results indicate that IgM and IgG were higher and IgA lower inpatients as compared to controls (Table I).

Total Serum IgE levels were not significantly different in patients and controls (Table II).

Decreased levels of all immunoglobulins were found in chronic carriers (Table III).

Inthe present study, serum IgM and IgG were high while low levels of IgA were observed in patients as compared to controls. Total serum IgE was found to be similar in both groups. Other reports indicate normal levels of total serum IgO and IgM^8,9. Although IgA deficiency does occur but reduced levels of IgA alone are not associated with increased suscepti­bility to giardiasis or severity of symptoms¹⁰. Serum IgE was found to be significantly higher in patients withgiardiasis than in controls and recovery from giardiasis was correlated by a decrease in serum IgE levels¹¹ while other reports indicate that G. lamblia infection was not related to difference in serum IgE levels^12-14.
0. lamblia is being reported as a frequent cause of chronic diarrhoea¹⁵. In the present study, decreased levels of all immunoglobulins were found in chronic cases while other reports indicate increased total serum immuno6globulins in patients with persistent diarrhoea and giardiasis¹⁶.  Hypogam­maglobulinemia and giardiasis may occur togetherbut differ­ence from normal levels of any immunoglobulin did not seem to explain either the presence of giardiasis or the variability of its clinical features. Individuals with lower immunoglobulin levels are not at greater risk of acquiring gianliasis than those with higher inimunoglobulin concentrations¹⁰, but the immu­nodeficient individuals once infected are much more likely to have an infection that results in symptoms¹⁷. It appears that serum immunoglobulins (1gM, IgG, IgA) have some relation­ship with giardiasis especially in chronic cases and a decrease in immunoglobulins may contrib,ute to 0. lamblia infection.

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