Prevalence and Subtype Identification of Blastocystis sp. in Healthy Individuals in the Tunis Area, Tunisia

Abstract

Abstract. Blastocystis sp. is currently the most common eukaryotic parasite found in humans. Despite its potential public health impact, epidemiological data regarding its prevalence and molecular subtype (ST) distribution in Maghreb are rarely reported. Therefore, the aim of this study was to determine the prevalence of the parasite in a cohort of healthy food handler Tunisian individuals and to acquire the first molecular data regarding the distribution of Blastocystis sp. STs in this country. Therefore, 524 fecal samples were collected, and 68 of them (13%) were identified as positive for the parasite by direct-light microscopy of smears. Seventeen samples of 100 negative by microscopy were also shown to be positive by real-time quantitative polymerase chain reaction. Among all the positive samples, 61 Blastocystis isolates were subtyped using partial small subunit ribosomal RNA gene analysis. ST3 was the most abundant (51%) followed by ST1 (30%), ST2 (16%), and ST4 and ST7 (both 1.6%).Blastocystis sp. is a parasite inhabiting the gastrointestinal tract of humans and a wide range of animals. This singlecelled eukaryote is currently the most prevalent protozoa found in human fecal samples with a worldwide distribution.

Prevalence and Subtype Distribution of Blastocystis sp. in Senegalese School Children

“…In other West African countries like Nigeria [ 31 , 37 ] and Côte d’Ivoire [ 38 ], ST1 was the predominant variant followed by either ST2 or ST3. Variation in ST distribution was also observed between other African regions as ST3 was predominant in Central [ 13 , 42 ] and North [ 36 , 47 , 49 , 50 , 51 ] Africa, with the exception of Libya, where ST1 was the most frequent ST [ 31 , 48 ] as in Southern Africa [ 44 ]. Although all these data were often based on a limited number of individuals, a geographical variation in the frequency of the three major STs was reported between African regions or within the same country that might simply reflect different exposure to environmental and/or animal infection sources.…”

“…In this aim, only data obtained by molecular methods were recorded as non-molecular methods such as microscopic observation of fresh feces are known to greatly underestimate the prevalence of the parasite [ 39 , 41 ]. The prevalence of the parasite ranges between 25.6% and 100% depending on the geographical area [ 12 , 13 , 31 , 36 , 37 , 38 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 ]. By focusing on the neighboring countries of Senegal (West Africa), the prevalence of Blastocystis sp.…”

Prevalence and molecular characterization of Strongyloides stercoralis, Giardia duodenalis, Cryptosporidium spp., and Blastocystis spp. isolates in school children in Cubal, Western Angola

“…Very similar subtype frequencies have been documented in hospital outpatients in Tanzania [ 64 ]. In contrast, ST1 was the most prevalent Blastocystis subtype circulating among Nigerian school children [ 62 ] and Libyan outpatients [ 87 ], and ST3 in both asymptomatic and clinical populations in Egypt [ 88 , 89 ], Senegal [ 63 ] and Tunisia [ 90 ]. Noticeably, ST4 was not detected in the investigated paediatric population.…”

“…Noticeably, ST4 was not detected in the investigated paediatric population. This Blastocystis subtype is commonly seen in European countries such as Denmark [ 91 ], France [ 92 ], Sweden [ 93 ] and the UK [ 94 ], but rare or absent in African countries [ 63 , 64 , 90 , 94 ], evidencing marked differences in subtype distribution by geographical region and (very likely) between groups of individuals. Although not yet conclusively proven, there is mounting evidence suggesting that Blastocystis pathogenicity could be subtype-related.…”

Restriction fragment length polymorphism (RFLP) analysis of Blastocystis spp. in symptomatic and asymptomatic individuals from Alexandria, Egypt

“…Worldwide, most Blastocystis infections in humans are attributed to STs 1-4. ST3 followed by ST1 were the most prevalent STs in in many countries as in Brazil [22] , France [20] , United Arab Emirates [44] , Tunisia [45] , Saudi Arabia [18] , Indonesia [46] and Iran [15] . Few studies showed slightly higher prevalence of ST1 compared to ST3 as in Philippines [47] and Tanzania [48] .…”