Occurrence and subtype distribution of Blastocystis sp. in humans, dogs and cats sharing household in northern Spain and assessment of zoonotic transmission risk

Abstract

Blastocystis sp. is probably the most common enteric parasite in humans globally. Although the role of Blastocystis in human disease is still controversial, epidemiological and experimental evidence suggests that pathogenicity may be associated with certain subtypes of the protist. Since the life cycle of Blastocystis is maintained through still elusive pathways, companion animals have attracted the attention of researchers as potential reservoirs of human infections. In order to evaluate the risk of zoonotic transmission of Blastocystis, we investigated the occurrence and molecular diversity of this microorganism in human, canine and feline populations sharing temporal and spatial settings in the province of Álava, northern Spain. A total of 268 (including 179 human, 55 canine and 34 feline) faecal specimens were obtained from 63 family households during February-December 2014. Detection of Blastocystis was achieved by PCR amplification and sequencing of small subunit rRNA genes. Blastocystis was found in 35.2% (95% CI: 0.29%-0.42%) of the human stool samples analysed, but not in any of the canine or feline faecal specimens investigated. Out of the 63 PCR-positive human samples, 84.1% (53/63) were successfully subtyped, allowing the identification of the subtypes ST2 (62.3%), ST3 (17.0%), ST1 (13.2%) and ST4 (7.5%). No mixed subtype infections were identified. Blastocystis carriage was independent of the gender and region of origin of the affected individuals, but children in the age groups of >5-10 years and >10-15 years were significantly more affected by the protist. None of the risk factors considered (water-use practices, contact with livestock, contact with individual undergoing diarrhoeal episodes) were associated with increased prevalence of Blastocystis. Our data demonstrate that pet dogs and cats play a negligible role as natural reservoirs of human Blastocystis infection in this geographic region, although the applicability of these results should be corroborated in future molecular epidemiological studies.

Blastocystis sp. Subtype Diversity in Wild Carnivore Species from Spain

“…Regarding the diversity and frequency of Blastocystis in Spain, ST1, ST2, ST3, and ST4 have been identified in a general, asymptomatic population in the North of the country (Paulos et al. ), whereas those same subtypes and to much lower extent ST6 and ST7 have been described in clinical samples (Carmena, unpublished data). Interestingly, ST4 has been previously documented as the most prevalent (94.1%) Blastocystis ST in mono‐infected patients with acute or chronic diarrhoea (Domínguez‐Márquez et al.…”

“…; Paulos et al. ) in different geographical areas of the world. In contrast, the occurrence of the parasite has been identified at comparatively higher rates (6.0–54.1%) in domestic ruminants, particularly cattle and sheep (Lee et al.…”

“…), but the least frequent ST circulating in asymptomatic subjects in Spain (Paulos et al. ), raising the question of whether ST4 is more pathogenic than other Blastocystis STs. Our results demonstrate that STs with zoonotic potential are present in carnivores, corroborating their potential role as a source of Blastocystis human infection and environmental contamination.…”

“…Blastocystis is frequently reported in a wide range of vertebrates including human and nonhuman primates, other mammals and birds. Animal-to-human (or vice versa) transmission has been suggested in several molecular epidemiological surveys (Eroglu and Koltas 2010;Ram ırez et al 2014;Stensvold et al 2009) but not in others (Paulos et al 2018). Taken together, these data seem to indicate that zoonotic/anthroponotic transmission of Blastocystis sp.…”

“…) but not in others (Paulos et al. ). Taken together, these data seem to indicate that zoonotic/anthroponotic transmission of Blastocystis sp.…”