Cyst detection and viability assessment of Balantioides coli in environmental samples: Current status and future needs

Abstract

The ciliate Balantioides coli is a human enteric parasite that can cause life-threatening infections. It is a food- and waterborne parasite, with cysts being the infective stage. Despite its importance as a potential pathogen, few reports have investigated its presence in environmental samples, and some issues need attention including i) The accuracy of B. coli identification. In most cases, the protozoa is identified only by its morphological traits, which can be identical to those from other parasitic ciliates of animals. Genetic analysis of cysts recovered from environmental samples is necessary for species confirmation. In addition, genetic methods used with faecal samples need to be adequately validated with environmental matrices. ii) The methodology for searching this parasite in environmental samples. The protocols include an initial phase to isolate the cysts from the matrix followed by a second phase in which concentration procedures are usually applied. The methods may be valid but are not standardised and differences between studies could affect the results obtained. iii) The areas that needs further research. The development of genetic identification methods and standardised analytical protocols in environmental samples are required, as well as the assessment of viability and infectivity of B. coli cysts. The development of axenic culture systems will boost research on this parasite.

Investigating the Occurrence of Soil-Transmitted Parasites Contaminating Soil, Vegetables, and Green Fodder in the East of Nile Delta, Egypt

“…B. coli and Blastocysts species were the least common parasites detected in this investigation, accounting for 18.2% and 11.2% of positive samples, respectively. Food-borne transmission of B. coli is of no significant importance in the developed countries, as this parasite has rarely been implicated in food-borne outbreaks; however, it has been frequently reported in surveys of parasites in fresh vegetables eaten raw in developing countries [ 61 ].…”

Balantioides coli Fecal Excretion in Hunted Wild Cervids (Cervus elaphus and Dama dama) from Portugal

“…However, caution should be taken as a very limited number of samples were tested at the zoological gardens. Another relevant aspect to note is that in all the studies mentioned above, identification of B. coli was completed by microscopic examination of fecal samples and molecular data were completely lacking [18][19][20], known to be prone to errors due to morphological characteristics being shared by cysts of other ciliate species, with sequencing as the preferred method for identification [9].…”

“…Although rare until today [2], B. coli is regarded as a pathogen capable of being involved in waterborne and foodborne outbreaks [9], having been detected in raw vegetables and fruits [10], animals (such as pigs) raised for meat production [11] and in water matrices (drinking water, rivers, ponds, canals and wastewater) [12]. In addition, deaths associated with B. coli infections have been recorded in humans [13] and animals, such as farm horses and non-human primates in captivity [14,15].…”

“…In addition, deaths associated with B. coli infections have been recorded in humans [13] and animals, such as farm horses and non-human primates in captivity [14,15]. Transmission occurs via the fecal-oral route, either indirectly by ingestion of contaminated food or water or through direct contact with infected hosts or their fecal material [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. In humans, infection by B. coli is characterized by abdominal pain and diarrhea.…”

Waterborne parasites in Uganda: A survey in Queen Elizabeth Protected Area

“…All the water samples were centrifuged at 1000 × g for 10 min to concentrate the oocysts, cysts and eggs [26]. A pellet was left at the bottom of the falcon tube after the supernatant was poured off.…”