A meta-analysis of Giardia lamblia in Iran

Giardia lamblia is the frequent cause of diarrhea in humans and other mammals across the world. The present systematic review and meta-analysis aimed to estimate the epidemiology of Giardia lamblia in the republic Islamic of Iran. The main international sources of ISI and Pubmed as well as the major national data banks in Iran including Magiran, IranMedex, SID and IranDoc were systematically searched for the words" Giardia lamblia" since 1990 onward. Overall, 43 reliable and similar studies in terms of methodology were selected for a systematic review. A meta-analysis was also conducted using the random-effects model. Heterogeneity was investigated by the Cochran's Q test. STATA was used for all analysis. Given the randomeffects model, the prevalence of Giardia lamblia in Iran was estimated to be 14.7% (95% reliability distance, 12.0%-16.6%). By age classification, the prevalence was 15.1% amongst fewer than 10 years children, 19.2% amongst adolescents and youngest of fewer than 20 years, and 6.7% amongst adults of between 20-30 years old (p<0.001). Annual classification showed that the maximum and minimum prevalence rates occurred in 1994 and 2005 (37.21 and 4.91% respectively). Geographical distribution of Giardia lamblia also showed that the eastern parts of the country nearby Pakistan and Afghanistan borders were extremely affected (35.5%). It was 16.9% in central provinces, 14.9% in the southern provinces, 13.2% in the north of country and 12.3% in the western provinces nearby Iraq and Turkey borders. Increased prevalence of Giardia lamblia in Iran, in spite of preventing strategies and valuable primary health care activities has been remained as a public health concern amongst children and in the eastern parts of the country nearby Pakistan and Afghanistan borders in particular.


INTRODUCTION
Traditionally, doctors and ordinary people have been focusing on parasitic infections and it has still remained among the important public health concerns leading to mass mortalities worldwide and in developing communities in particular.Infection with Giardia may be associated with significant ill-health issues and while the reported incidence of infection is of concern in Iran, the true prevalence of infection and extent of morbidity due to this organism is unknown.
Giardia Lamblia is an important human pathogen with a global distribution.This flagellate mono cellular is the pathogenic parasite of the upper part of the small intestine affecting many vertebrata including human (Disney et al., 1998;Baruch e al., 1996).The importance of potable water supplies as a source of infection is not obvious, nor is the role of zoonotic spread.Even though, water sources where polluted with the mature cysts of parasite are the main source of infection (Adam, 1991).
Parasites are even survived for some times due to the relatively resistance of Giardia cysts to chlorine that is existed in the water (Sayyari and Imanzadeh, 2005).
Although, Giardia lamblia affects all age groups but children are more vulnerable, sensitive and susceptible (Baruch et al., 1996), probably due to lack of immunesystem and personal health (Amar, 2000;Jahni et al., 2009).Prevention strategies include treatment of patients and disinfection of polluted drinking waters (Sayyari and Imanzadeh, 2005;Amar, 2000).
Iran is an appropriate environment for activation of various parasites due to the geographical features, the climatic conditions and the bio-cultural characteristics.Given that the recognition and controlling of risk factors of the parasitic infections, requires epidemiological investigations across the country.The present study aimed to investigate almost all studies conducted in Iran during the last decade regarding the Giardia lamblia infection.

MATERIALS AND METHODS
This was a systematic review and meta-analysis study on current investigations and research publications about epidemiology of Giardia lamblia in Iran during the last decade.The main international sources of ISI and Pubmed as well as the major national data banks in Iran including Magiran, Iran Medex, SID and Irandoc were systematically searched for the words" Giardia lamblia" since 1990 onward.
All measurements for the meta-analysis were done using STATA software and random effects model.The heterogeneity was investigated by Cochran's Q test.Figures were plotted using SPSS statistical software.

RESULTS
Meta-analysis model with random effects showed a prevalence rate of 14.7% (reliability distance of 95 -16.6-12.8%)for Giardia lamblia in Iran.The following age-specific prevalence rates were observed (p< 001) as demonstrated in Table 2: 1. 19.2% in the age group of 10-20 years old (95% reliability distance of 12.7-17.8)2. 6.4% in the age group of 20-30 years old (95% reliability distance of 9.1-3.7) 3. 2.6 % In the age group of 30-40 years old (95% reliability distance of 2.4-4.9) The time trend of Giardia lamblia infection showed a maximum prevalence of 37.22% in 1994 and the least prevalence of 4.91% in 2005 (Figures 1 and 2; Table 1).
Geographical distribution of Giardia lamblia also showed that the eastern parts of the country nearby Pakistan and Afghanistan borders were extremely affected (35.5%).It was 16.9% in central provinces, 14.9% in the southern provinces, 13.2% in the north of country and 12.3% in the western provinces nearby Iraq and Turkey borders (Table 3).

DISCUSSION
This is the first meta-analysis study in Iran as far as we have searched in the published literature, focusing on epidemiology of Giardia lamblia and its age-specific prevalence in particular.The descriptive cross sectional studies are the current ways for diseases assessments in the community.The present study found an overall prevalence rate of 14.7% for Giardia lamblia in Iran during the last decade starting from 1990 onward.Despite of this finding which put the Giardia lamblia as the most frequent intestinal parasite in Iran, but fortunately its annually trends in the whole country is decreasing.
In the current study, the maximum prevalence rate of 37.21% occurred in 1994 and amongst children and adolescents in particular by age-specific distribution analysis.The age-specific distribution analysis in the present study showed that Giardia lamblia was more frequent in the age lower than 20 years, while in the persons higher than 20 years, this age difference was not considerable.This could be in part related to unhealthy life style, consumption of low standard drinking water, resistance of Giardia cysts to chlorination and inappropriate health system due to rottenness of plumbs and flowing of sewages in some regions.Meanwhile, migrations, global warming, wars, natural disasters such as earthquake, floods, lack of health drinking water and resistance of the intestinal parasites to the treatment might be involved.
Even though, decreasing annual trends of Giardia lamblia in Iran could be related to the community health      (Celiksoz et al., 2005).In a similar study, the prevalence of Giardia was estimated to be 26.2%amongst children in Damghan (Heidari, 2003).
In the current study, the rate of Giardia infection was 35.5% in the eastern regions of the country and 16.9 % in the central areas.In tropical regions and in rural areas in particular, the prevalence of Giardia is expected to be high because of the climatic and health conditions as well as the socioeconomic situation.Despite valuable primary care activities in Iran, the reason behind this finding is due to poor cultural and socio-economic status of people in these regions.People might have not changed the health beliefs and life styles.
In conclusion, increased prevalence of Giardia lamblia in Iran, in spite of preventing strategies and valuable primary health care activities has remained a public health concern amongst children and in the eastern parts of the country nearby Pakistan and Afghanistan borders in particular.

Figure 1 .
Figure 1.Annual trends of Giardia lamblia in Iran from 1990 onward.

Figure 2 .
Figure 2. Regression plots of Giardia lamblia in Iran from 1990 onward.

Table 1 .
Epidemiological characteristics of included studies on Giardia lamblia in Iran.
N: Northern W: Western C: Central E: Eastern S: Sauterne*

Table 2 .
Age-specific distribution of Giardia lamblia in Iran.Weight in meta-analysis studies is based on the sample sizes and will be accounted from 100. *

Table 3 .
Geographical distribution of Giardia lamblia in Iran.