Blastocystis in captivated and free-ranging wild animals worldwide: a review

Abstract

Blastocystis is the most prevalent eukaryotic gastrointestinal symbiont found in humans and animals worldwide. Increased human infection rates are associated with raising concerns about the involvement of the parasite in public health. Over the last decade, the number of linked epidemiology studies has been prudently grown. Microscopy has been used to detect the presence of protozoan and the advent of molecular techniques has made detection easier. However, due to its limited host specificity and zoonotic potential, animals, either livestock or wildlife animals, may serve as a potential reservoir for Blastocystis infection transmission. The approach utilised in this study aided in understanding the distribution and prevalence of Blastocystis in animals, particularly captivated and free-ranging wild animals worldwide due to increased interest. This review will help comprehend the epidemiological aspects, demographic, subtypes, and the zoonotic potential of Blastocystis in wildlife and captive animals.

Systematic Review and Meta-Analysis: Epidemiology of Human Blastocystis spp. Infection in Malaysia

“…In the past, ST6 was seen among chicken slaughterhouse workers in Lebanon [ 88 ], and ST5 was seen among pig handlers in Thailand [ 89 ]. Other subtypes, such as ST7–ST14, were also frequently found in domestic animals and wild animals in prior studies conducted in Malaysia and elsewhere [ 90 , 91 ] but were not observed in humans in our systematic review. The presence of ST5 and ST6 among various cohorts in Malaysia indicates zoonotic transmission, as these subtypes have been reported among the domestic animals [ 92 ].…”

First Epidemiological Survey on the Prevalence and Subtypes Distribution of the Enteric Parasite Blastocystis sp. in Vietnam

“…By grouping the bovine ST10 and ST14 isolates, persons living in the Quang Nam area had a 3.4 higher risk of infection by these isolates, compared to persons from Da Nang (OR: 3.400, CI: 1.302–10.583, p = 0.019). This difference in ST distribution could be explained by the rurality of the province of Quang Nam in comparison to the more urbanized Da Nang area and the increased presence in the vicinity of dwellings of poultry and livestock, which are known to be carriers of ST7 and ST10/ST14 [ 8 , 9 , 10 ], respectively, and thus potential reservoirs of parasite transmission to inhabitants. Moreover, individuals who drank well water (OR: 10.875, CI: 1.770–68.146, p = 0.008) or presented constipation (OR: 11.375, CI: 1.311–81.393, p = 0.016) were significantly predictive of the risk of ST1 infection.…”

“…Strikingly, the distribution of STs in Vietnam presented a major particularity, with a large proportion of isolates considered as zoonotic. Indeed, the avian ST6 and ST7, the ST8 known to colonize primates as other hosts, and the bovine-adapted ST10 and ST14 [ 2 , 8 , 9 , 10 , 35 ] accounted for more than 50% of the subtyped isolates, highlighting a wide zoonotic transmission of Blastocystis sp. in this Vietnamese cohort.…”

“…is currently the most common intestinal protozoan identified in the human population worldwide [ 1 , 2 , 3 , 4 ] since its prevalence has often been reported to exceed 50% in developing countries from diverse geographical areas and, in particular, in the African continent [ 5 , 6 , 7 ]. This enteric microorganism has also been frequently detected in the gastrointestinal tract of a wide range of animals, including numerous groups of mammals, birds, fish, reptiles and insects [ 8 , 9 , 10 , 11 ]. Like other intestinal protozoa, the main mode of transmission of Blastocystis sp.…”

“…Conversely, other STs found less frequently or rarely in humans are considered to be of animal origin because of their predominance in particular groups of mammals or birds. For example, ST5 mainly occurs in pigs, ST6 and ST7 in poultry and ST10 and ST14 in livestock [ 8 , 9 , 10 ]. The presence of these STs in the human population can, therefore, be explained by zoonotic transmission, as evidenced in recent studies through the identification of isolates exhibiting the same SSU rRNA gene sequence in both individuals and in-contact animals [ 15 , 34 , 35 ].…”