Abstract
Objective To determine the prevalence of intestinal parasites and rates of stool testing compliance, as well as associated patient characteristics, among newly arrived refugees at the Mosaic Refugee Health Clinic in Calgary, Alta.
Design Retrospective chart review.
Setting Primary care clinic for refugee patients.
Participants A total of 1390 new refugee patients at the clinic from May 1, 2011, to June 30, 2013.
Main outcome measures Stool ova and parasite test completion and proportion of positive test results.
Results Of 1390 patients, 74.1% (95% CI 71.7% to 76.4%) completed at least 1 stool ova and parasite test. Among those completing tests, 29.7% (95% CI 26.9% to 32.6%) had at least 1 positive result. Patients aged 6 to 18 years were more likely to have positive test results (38.5%, 95% CI 32.2% to 45.0%) than patients aged 19 to 39 were, as were those last residing in Asia (36.4%, 95% CI 30.4% to 42.8%) or sub-Saharan Africa (30.9%, 95% CI 26.8% to 35.1%), compared with those arriving from the Middle East. Giardia lamblia, Blastocystis hominis, Dientamoeba fragilis, and Entamoeba histolytica or Entamoeba dispar were the most prevalent parasites. If B hominis and D fragilis are excluded because of their lower potential to cause harm, the overall prevalence was 16.3%.
Conclusion Given the high compliance of patients submitting stool ova and parasite tests and a high prevalence of positive test results in some refugee groups, targeted screening should be considered in newly arrived refugees at greater risk of intestinal parasites.
Canada welcomes more than 20 000 refugees per year.1 Refugees often come from regions with higher infectious disease burdens that are often associated with overcrowded living conditions and poor sanitation. Further, many refugees have limited or inequitable access to health care. The World Health Organization (WHO) estimates approximately 1.5 billion people worldwide are infected with soil-transmitted helminths, which can lead to considerable morbidity and nutritional deficiencies.2 The WHO is currently rolling out a strategy to periodically treat soil-transmitted helminths.2 Previous studies have demonstrated prevalences of stool tests positive for ova and parasites of 13% to 57% in newly arrived refugee populations in Western countries, as well as a higher burden of disease in children.3–7
The Canadian guidelines for the delivery of refugee preventive and primary health care recommend screening serology for both strongyloidiasis and schistosomiasis but do not suggest screening stool for other intestinal parasites.8 This differs from the most recent American and Australian guidelines that suggest presumptive pretreatment of intestinal parasites and an arrival screening algorithm.9,10
The purpose of this study was to determine the prevalence of intestinal parasites and rates of stool testing compliance, as well as associated patient characteristics, in newly arrived refugees at the Mosaic Refugee Health Clinic (MRHC) in Calgary, Alta.
METHODS
Study design and setting
We conducted an exploratory retrospective review leveraging data from the MRHC electronic medical record (EMR). The institutional review board of the University of Calgary granted ethics approval for the project.
The MRHC formed in response to the growing need for streamlined medical care for refugees arriving in Calgary.11 Government-assisted refugees are automatically referred to the clinic through a local resettlement agency. Other refugees self-refer to the clinic for care. Refugees are encouraged to attend a medical intake visit to complete various screening tests similar to those recommended in the recent Canadian clinical guidelines.8
Patient population
The study population included all refugee patients with an intake visit between May 1, 2011, and June 30, 2013, at the MRHC. Among the 1400 patients who had intake appointments at the MRHC during the study period, we excluded 8 who were born in Canada or the United States and 2 owing to a lack of information in the EMR.
Stool ova and parasite tests
The MRHC previously screened all newcomers with 2 stool ova and parasite tests. Stool specimens were collected both fresh and in sodium acetate–acetic acid–formalin preservative and sent to Calgary Laboratory Services for microbiologic analysis. All specimens were first screened for Giardia lamblia and Cryptosporidium using an enzyme immunoassay12; positive results were confirmed by direct fluorescent antibody testing. Microscopic examination of all specimens was performed on a wet mount, after concentration with ethyl acetate, and a permanent slide, using a modified iron hematoxylin stain with a carbol fuchsin and acid decolourization step.13
Patient characteristics
We identified patients’ sex, date of birth, country of birth, country of last residence, refugee camp history, number of stool ova and parasite tests completed, and test results. Two reviewers (G.D., M.D.) recorded the outcomes of the first 2 stool ova and parasite tests, including types of parasites identified. Only tests completed within 1 month of each other were included, as we considered tests beyond this time period not to be screening tests.
Statistical analysis
Two stages of analyses were performed. The first comparison was between the patients who completed stool tests and those who did not complete the tests. The second comparison was between those patients who had test results positive for parasites and those whose results were negative.
We first conducted descriptive analyses using
2 tests to compare categorical variables with the outcomes of interest. We used univariate modified Poisson regression models with robust standard errors to analyze the relationship between selected variables and the likelihood of completing the tests.14 The variables of interest were age at intake, sex, region of last residence, and a personal history of residing in a refugee camp. We used region of last residence rather than region of birth, as we thought it more relevant; some refugees spend many years in another country before coming to Canada. Subsequently, a multivariate Poisson model was fit using the variables with P values less than .2 from the univariate analyses and using backward elimination, retaining covariates with P values less than .05. A similar approach was used for positive stool test results. All statistical analyses were performed with Stata, version 12.1.
RESULTS
Characteristics of the study population (N = 1390) are shown in Table 1.15 The population was evenly divided between male and female patients; almost half (46.5%) were between the ages of 19 and 39 years, and almost half (46.4%) had most recently resided in sub-Saharan Africa. Figure 1 shows countries of last residence and countries of birth.
Baseline characteristics of clinic patients: N = 1390.
Patients’ origins (N = 1390): A) Country of birth and B) country of last residence.
Of the 1390 patients, 1030 (74.1%, 95% CI 71.7% to 76.4%) completed at least 1 stool and ova parasite test (343 completed 1 test and 687 completed 2). The median time from intake to completion of the first test was 9 days (interquartile range 6 to 27). Table 2 describes the characteristics associated with the completion of a stool test.15 Both the univariate and multivariate regression models showed that patients arriving from sub-Saharan Africa, North Africa, and Asia were more likely to complete their tests, and patients from Europe or North America were less likely to complete their tests, compared with patients arriving from the Middle East. Further, patients were also more likely to complete stool testing if they did not reside in refugee camps before arriving in Canada when compared with those who did reside in refugee camps.
Characteristics associated with the completion of at least 1 ova and parasite stool test
Among patients who completed at least 1 test, 306 (29.7%, 95% CI 26.9% to 32.6%) had at least 1 positive stool ova and parasite result. Significantly more patients who completed 2 tests had positive results compared with those who completed only 1 test (32.3% vs 24.5%; P = .01). Table 3 describes the association of other characteristics with having a positive test result.15 Univariate and multivariate regression models both showed that those aged 6 to 18 years were more likely to have a positive stool test result compared with those aged 19 to 39 years; those who had most recently lived in an Asian region were more likely to have a positive stool test result compared with those who had most recently lived in the Middle East.
Characteristics associated with having at least 1 positive ova and parasite stool test result
Of the 306 patients with positive stool test results, 219 (71.6%) had 1 parasite present, while 64 (20.9%) had 2 parasites, 17 (5.6%) had 3 parasites, and 6 (2.0%) had 4 parasites.
Fourteen parasites were identified, the most prevalent of which were G lamblia, Blastocystis hominis, Dientamoeba fragilis, and Entamoeba histolytica or Entamoeba dispar (Table 4).
Prevalence of stool ova and parasites by region of last residence: N = 1030 refugees who completed at least 1 stool test.
If B hominis and D fragilis are excluded because of their lower potential to cause harm, the overall intestinal parasite prevalence was 16.3%. With this exclusion, the prevalence was 24.7% for refugees arriving from Asia and 25.2% for children aged 6 to 18 years.
DISCUSSION
The MRHC is the predominant primary health care provider for refugees in Calgary, making it a unique care model seeing patients of all ages and refugee statuses. This allows a concentrated and optimal research population with consistent screening methods.
Our study results reinforce that the refugee population arriving in Calgary has a high prevalence of intestinal parasitic infection. This study demonstrated high compliance for patients completing at least 1 stool test (74.1%). Among those completing tests, the prevalence of intestinal parasites was 29.7%. The highest prevalence of positive tests was found in school-aged children and in those whose last region of residence was in Asia or sub-Saharan Africa.
Other Canadian studies have reported the prevalence of intestinal parasites via stool ova and parasite testing in refugee populations.6,16–19 A recent study of primarily refugee claimants (N = 1063) in Toronto, Ont, found a 16% prevalence of parasites from the 391 stool tests completed.19 This lower prevalence might be related to refugees coming from countries with lower intestinal parasite burden. A large study from almost 30 years ago found a prevalence of 29.3% (N = 1967),18 while 2 more recent, smaller studies found prevalence rates of 10.5% (N = 289)17 and 13.6% (N = 112).6
Our study demonstrated a significantly higher prevalence of parasites in school-aged children when compared with adults and children younger than 6 years old. This finding is similar to data on refugees arriving in other Western countries.3,4 The American Academy of Pediatrics recommends screening all refugee children with 3 stool ova and parasite tests if the children did not receive presumptive treatment of soil-transmitted helminths.20 The WHO states that children with intestinal parasites, including those who are asymptomatic, can develop nutritional, developmental, and physical complications and suggests that treatment is safe, effective, and inexpensive.2 If untreated, there is concern for ongoing local disease exchange. A Canadian study specifically demonstrated a lack of self-clearance and ongoing local transmission when refugees were tested at 6 months after arrival in Canada without screening or treatment of intestinal parasites.16
In our study, patients whose last region of residence was Asia had the highest prevalence of intestinal parasites (36.4%). The second highest prevalence was among patients from sub-Saharan Africa (30.9%). Other studies have also noted a difference in intestinal parasite prevalence by region of origin in refugee populations. A Swedish study indicated that originating from India or Southeast Asia was the greatest predictor of intestinal parasites in refugees.21 American studies report both Asia and Africa as regions of note for intestinal parasite infections in refugees.7,22 The United States has a predeparture treatment program for intestinal parasites, unlike Canada, which might have affected the prevalence rates found.
The parasites with the greatest prevalence in our study were G lamblia, B hominis, D fragilis, and E histolytica or E dispar. Other studies have found high prevalence rates of these parasites as well.3,5,7,21,23,24 Giardia lamblia infections have several clinical presentations ranging from asymptomatic presentations to growth and development concerns in children.25–28 In children and their families, treatment of G lamblia is important to ensure the health and development of the children and to reduce ongoing transmission. Blastocystis hominis and D fragilis tend to be benign and are commonly not treated.29,30 At the time of the study, E histolytica and E dispar were not differentiated by Calgary Laboratory Services. Entamoeba histolytica commonly causes adverse health effects and needs treatment whereas E dispar does not.31 Therefore, patients with results positive for E histolytica or E dispar were treated.
Our findings suggest that refugees are likely to complete stool testing (74.1%) and that testing identifies a high prevalence of intestinal parasites (29.7%). When the relatively benign parasites B hominis and D fragilis are excluded, the overall prevalence remains high (16.3%) and is even higher in school-aged children (25.2%) and refugees from Asia (24.7%).
Limitations
Study limitations were related to its retrospective nature and to EMR data extraction from a database with multiple users. For example, refugee camp history and refugee classes were not routinely recorded. However, the clinic data from 2012 (the only complete calendar year in our study) demonstrated that most refugees were government (47%) or privately sponsored (41%) and only 12% were refugee claimants.
Conclusion
This study demonstrates that refugees arriving in Calgary have a high prevalence of intestinal parasitic infections; this finding can likely be generalized to other large Canadian urban centres receiving high volumes of new refugees. Unlike the United States, Canada does not provide predeparture empiric treatment of refugees. Therefore, although treatment is not warranted in all clinical scenarios, targeted screening of stool for ova and parasites should be considered in newly arrived refugees at greater risk of intestinal parasites. Specifically, screening should be considered for refugee children, especially those arriving from Asia or sub-Saharan Africa. Further consideration should be given to those exhibiting gastrointestinal symptoms. As this is the largest Canadian study of its kind in the past 30 years, it will add to the limited data available to clinicians working in this area to help them make informed clinical decisions.
Acknowledgments
We thank Syed Mehdi from the Mosaic Primary Care Network in Calgary, Alta, who helped us with data extraction from the electronic medical record. We also thank Dr Wilson Chan, a microbiologist from Calgary Laboratory Services, who provided us with insight as well as the text regarding the stool ova and parasite testing protocols. Finally, we thank the Department of Family Medicine research group at the University of Calgary for their support, specifically Catherine Leipciger, Grace Perez, and Nathan Turley.
Notes
EDITOR’S KEY POINTS
This study aimed to determine the prevalence of intestinal parasites and rates of stool testing compliance among newly arrived refugees in a refugee health clinic in Calgary, Alta.
More than 70% of patients completed their requested stool tests. There was an overall intestinal parasite prevalence rate of 29.7%.
The highest parasite burden was found in school-aged children. This population has more to gain from both screening and treatment, as untreated intestinal parasites are associated with growth and development concerns.
POINTS DE REPÈRE DU RÉDACTEUR
Cette étude voulait vérifier la fréquence de parasitose intestinale chez des réfugiés nouvellement arrivés dans une clinique pour réfugiés à Calgary, en Alberta, ainsi que le taux d’acceptation par les patients du dépistage qu’on leur suggérait.
Plus de 70 % des patients se sont soumis à l’examen des selles qu’on leur suggérait. Globalement, la fréquence de parasitose intestinale était de 29,7 %.
C’est chez les enfants d’âge scolaire que les cas positifs étaient les plus nombreux. C’est aussi ce groupe qui bénéficierait le plus d’un dépistage et d’un traitement, puisque qu’une parasitose intestinale non traitée peut compromettre la croissance et le développement.
Footnotes
This article has been peer reviewed.
Cet article a fait l’objet d’une révision par des pairs.
Contributors
Drs DeVetten and Dirksen were responsible for planning and carrying out the research including designing the research approach, completing a literature review, acquiring the data, and writing most of the article. Mr Weaver analyzed the data and was substantially involved in revising the manuscript. Dr Chowdhury provided important direction for the data analysis and presentation of the manuscript. As the principal investigator, Dr Aucoin was responsible for the study concept and contributed to manuscript revisions.
Competing interests
None declared
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