A retrospective and descriptive analysis was carried out from January 2016 to December 2020 in the Laboratory of Parasitology-Mycology of Fann University Hospital, which is a public referral hospital, located in the capital city of Dakar. All patients attending to the laboratory for a parasitological examination of stool samples, were included in this study.

Sociodemographic, clinical, and biological data from patients were collected using the laboratory records. The following variables were collected: age, sex, year of sample collection, season, clinical indication, macroscopic aspect of sample and parasitological results. Age was defined in 4 categories: less than 15 years, 15 - 30 years, 30 - 45 years, and more than 45 years. The season was defined in both the dry season (October to June) and rainy season (July to September).

Fresh stool sample was collected into wide mouth for intestinal parasite detection. Stool samples were examined macroscopically for color, consistency, presence of blood, mucus, pus, and large worms. A portion each of the stool samples was processed with a direct examination by light microscopy to detect cysts, trophozoite, eggs and larva. The remaining part of stool samples were examined using a modified Ritchie technique and modified Zielh Neelsen technique.

After data collection, data were entered in Excel software and the analysis was performed using Stata software version MP 16 software. Quantitative variables were described in terms of means, standard deviation. Inter group comparisons were performed using ANNOVA test or Student t test after checking the conditions of application of these tests. When these tests were not applicable, the non-parametric tests (Man Withney, Kruskall Wallis) were used. For descriptive data, percentage with confidence interval (CI) was used to assess the prevalence of each outcome. Proportions were compared using chi-square test or the Fisher exact test (univariate analysis). The significance level of the different tests was 0.05 two-sided.

This study was conducted according to the Declaration of Helsinki and existing national legal and regulatory requirements. To respect the confidentiality, an identification code was given to each participant. Data are routinely collected from patients who attended to hospital for biomedical testing. Just a permission to used data for publication was requested from the administration of Fann University Hospital which a National Reference Hospital.

Overall, 3285 patients with completed data were enrolled in the analysis. The age of the patients ranged from 5 to 93 years with an average of 26.2±20.6 years. Study population was mainly represented by subject under 15 years old (41.5%) followed by subjects in the age category 15-30 years with 22.3%. The study population was predominantly male (50.8%). The sex ratio was 1.03. Stratifying on the season, 76.3% of the sample of our study was collected during the dry season against 23.7% during the wet season (Table 1).

Among 3825 participants, 2017 (52.7%) were symptomatic. The main clinical symptoms were (i) acute febrile diarrhea 2.33%, (ii) acute non-febrile diarrhea 8.3%, (iii) chronic diarrhea on HIV1 terrain 4.6% and (iv) chronic diarrhea without notion of HIV1 10.6%. Abdominal pain was found in 11.1% of cases. Dyspeptic disorders, fever and dysenteric syndrome were observed with respectively 4.8%, 4.7% and 1.6% (Table 2)

Overall, 1009 samples were positive, which represents a prevalence of intestinal protozoan infection of 26.4%. Mono-parasitic infection defined as presence of one parasite was noted in 81.6%. Bi-parasitism (presence of two parasites) and poly-parasitism (more than two parasites) were found in 18.2% and 2.6% respectively. Association between protozoan and helminth was observed in 8.7% (Table 3). The most prevalent parasites were Blastocystis sp. (40.8%), Entamoeba Coli (38.2%), Endolimax nana (8.2%) and Giardia intestinalis (8.1%). Entamoeba histolytica was observed with 2.3%. Oocyst Isospora belli was observed with a frequency of 0.8% (Table 4). The main co-infections detected in di-parasitism were Blastocystis sp. + E. Coli (20.1%), E. Coli + E. nana (18.5%), Trophozoite E. Coli + Cyst E. Coli (15.2%), E. nana + Blastocystis sp. (8.7%), Blastocystis sp. + G. intestinalis (8.2%).

In poly-parasitism, the most prevalent association were: Blastocystis sp. + E. Coli + E. histolytica (7.7%), Blastocystis sp. + E. Coli + Pseudolimaxbutschili (7.7%).

Stratifying by year of sample collection, the results showed that the frequency of intestinal protozoa was higher in 2017 and 2020 with 29.7% and 31.9%, respectively. The lowest positivity rate was noted in 2018 (20.9%). The difference was statistically significative between the year of sample collection (p<10^-3) (Figure 1).

According to age category, intestinal protozoa carriage was more important in patients aged 15 - 30 years with 28.3%. The prevalence in subject under 15 years old was 25.9%. The difference between the age group was not significative (p=0.52). Intestinal protozoa prevalence was higher among male participants (29.9%) compared to female participants (25.7%) (p=0.57). During the rainy season, patients were more infected (26.9%) compared to dry season where the frequency of intestinal protozoan infection lower with no significant difference (p=0.65). According to symptoms, the prevalence was more important in asymptomatic subjects (29.5%) compared to symptomatic ones (23.5%) (Table 5).

In symptomatic subjects, patients with acute febrile diarrhea were more infected 29.2%. The prevalence in patients with acute non-febrile diarrhea was 25.5%. In patients with chronic diarrhea (HIV positive), the prevalence of intestinal protozoan infection was 21.2%. Among patients with dysenteric syndrome and dyspeptic disorders, intestinal protozoa carriage was 23.8% and 21.8% respectively (Figure 2).

According to the aspect stool samples, intestinal protozoa parasites were more frequent when the stool appearance was consistent (26.9%). The prevalence of intestinal protozoa parasites in patients with watery and watery+mucus stools was 20.8% and 19.8% respectively. Patients with watery stools with blood and mucus had a positivity rate of 21.5%. The prevalence of intestinal protozoan parasite in patients with yeast on microscopic examination was 12.5%. Parasites carriage in patients with filaments on microscopy was 10% and 7.1% in those with red blood cells in the stool. No parasites were observed in patients with leukocytes in the stool (Table 6).

Intestinal parasitic infections are major cause of morbidity and mortality worldwide especially in developing countries. With the implementation of mass deworming campaign with Mebendazole/Albendazole, there is a rarefaction of helminths and a persistence of intestinal protozoa.

The results of our study showed an overall prevalence of 26.4% of intestinal protozoan infection. Sylla et al when studying the epidemiological aspects of intestinal parasitic infection in the same hospital between, have found a prevalence of 26.8% with a predominance of protozoa (83%) 19. Similar trends were previously described by Tine et al and Faye et al who reported 29.6% and 23.7% prevalence of intestinal protozoa parasites respectively1419 . Other studies conducted in worldwide have showed the endemic characters of intestinal protozoa parasites. In Cote d Ivoire, Ouatara et al when assessing the prevalence and polyparasitism of intestinal protozoa in school aged children have noted a high intestinal protozoa prevalence 98.5% (4398/4466) 20. Afshar et al in Iran reported high prevalence of protozoan parasites 32.3% (95% CI 28.4 to 36.5) compared helminthic parasites 3.2% (95% CI 2.1 to 4.7) 21.

The species most frequently found in our series were Blastocystis sp. (40.8%), E. coli (38.2%), E. nana (8.2%), G. intestinalis (8.1%), E. histolytica (2.3%).These species are therefore mostly non-pathogenic except G. intestinalis. Diongue et al in 2017 have found́ in their series Entamoeba coli (51.5%), E histolytica (17%), G. intestinalis (10.5%) and Blastocystissp (5.6%) 22. The high frequency of intestinal protozoa parasites was described in other countries. In Benin by Nicolas et al have showed 76.03% intestinal parasite prevalence with high proportion of protozoa parasites (87.5%). The main protozoa species were Giardia lamblia (39.42%), E. histolytica (25.96%), E. coli (11.54%), Trichomonas intestinalis (10.58%)23. Dorkenoo et al in Togo when studying the prevalence of Soil-Transmitted Helminths and Intestinal Protozoa among School Children in Lome have observed high prevalence of intestinal protozoa (52.2%) with the following main species: E. coli (16.5%), E. histolytica (2.3%), G. lamblia (11.5%), Blastocystis sp. (10.9%) 24. Similar species were noted in Marocco by Hafida et al with Blastocystis sp. (30.2%), E. coli (25.6%), G. intestinalis (17.4%) and E. histolytica (10.5%)25. Au Tchad, Emmanuel et al have showed 39.5% prevalence of intestinal parasites. The parasitism was mainly due to protozoa with 97%. The main parasites identified are G. intestinalis (27%), E. histolytica (21%), E. coli (18%) T. intestinalis (15%) 26.

The results from this study showed that intestinal protozoa carriage was more important in patients aged 15 - 30 years with a percentage of 28.3%. The prevalence in subject under 15 years old was 25.9%. The lower frequency observed in the 0-15 years category (25.9%) is probably the result of the action of the Ministry of Health which since 2006 has implemented regular systematic deworming campaigns with Mebendazole/Albendazole in children in all health districts of Senegal.

Our results showed that the frequency of protozoa parasite was higher in males (26.9%) than in females (25.7%). Similar results showing predominance of intestinal protozoan infection in male patients were observed in Yemen and Malaysia 2728. Other studies conducted in Senegal have demonstrated that the prevalence of intestinal protozoa parasites was more important among female participants1423. This is in line with previous study conducted in Kenya where the prevalence of intestinal parasitic infection was higher in female participant (42.5%) compared to male participants (41.6%) 29.

Regarding the season, the results from our study showed that intestinal protozoa carriage was is more frequent during the rainy season (26.9%). This situation could be explained by a degradation of hygiene conditions observed during the period. Similar results were obtained by Sylla et al with a higher frequency in rainy season (27.27%) than in the dry season 26.5% 12.

According to the aspect of stool samples, the results of this study showed that intestinal protozoa parasite carriage was observed in patients with watery stool and watery+mucus stools was 20.8% and 19.8% respectively.Patients with watery stools with blood and mucus had a positivity rate of 21.5% This was previously described in Rwanda by Emilie et al who noted that intestinal parasites were found in patients having watery stool (78.9%), watery+mucus (42.2%). Low parasite carriage (8.3%) was noted in patients with watery+mucus+blood in their stool samples 30. In patients with consistent stool sample, similar results were noted in Rwanda.

Therefore, our results point out that in developing countries intestinal parasitic infection is still endemic despite the implementation of mass deworming campaign in children and other age groups. Intestinal protozoa parasites are frequent with a predominance of non or low pathogenic forms.