Zoonotic Potential of the Microsporidia

Abstract

Microsporidia are long-known parasitic organisms of almost every animal group, including invertebrates and vertebrates. Microsporidia emerged as important opportunistic pathogens in humans when AIDS became pandemic and, more recently, have also increasingly been detected in otherwise immunocompromised patients, including organ transplant recipients, and in immunocompetent persons with corneal infection or diarrhea. Two species causing rare infections in humans, Encephalitozoon cuniculi and Brachiola vesicularum, had previously been described from animal hosts (vertebrates and insects, respectively). However, several new microsporidial species, including Enterocytozoon bieneusi, the most prevalent human microsporidian causing human immunodeficiency virus-associated diarrhea, have been discovered in humans, raising the question of their natural origin. Vertebrate hosts are now identified for all four major microsporidial species infecting humans (E. bieneusi and the three Encephalitozoon spp.), implying a zoonotic nature of these parasites. Molecular studies have identified phenotypic and/or genetic variability within these species, indicating that they are not uniform, and have allowed the question of their zoonotic potential to be addressed. The focus of this review is the zoonotic potential of the various microsporidia and a brief update on other microsporidia which have no known host or an invertebrate host and which cause rare infections in humans

High Seroprevalence of Encephalitozoon cuniculi in Pet Rabbits in Japan

“…Regarding the result that anti-E. cuniculi IgG antibodies were detected at 75.2% in group II, a finding similar to this was also found in a survey of 100 New Zealand White rabbits maintained in a research colony, in which 72% of the animals showed renal lesions and in which parasites were identified in 9% [14], supporting our decision for having grouped our 337 healthy rabbits into two groups, i.e., groups I and II. The suggestion that E. cuniculi can be transmitted by ingestion of spores excreted in urine [10] seemed plausible in positive rabbits in group II.…”

“…For example, in the United Kingdom, Harcourt-Brown and Holloway [6] reported a rate of detection of anti-E. cuniculi IgG antibodies among 38 asymptomatic rabbits of 36.8%. In Switzerland, Mathis et al [10] reported that anti-E. cuniculi IgG antibodies were detectable in 7.5% of 292 asymptomatic rabbits. Nevertheless, in this study of the 74 rabbits in group I, regarded as examples of healthy and isolated rabbits, a detection rate of anti-E. cuniculi IgG antibodies of 29.7% was found.…”

Enterocytozoon bieneusiin human and animals, focus on laboratory identification and molecular epidemiology

“…Historically, these obligate intracellular parasites have long been recognized as pathogens in animal industries, first in silkworms in 1857, then in honeybees more than a century ago. They were later found in fish and more recently in mammals (reviewed in Mathis et al, 2005). Prior to the middle of the 1980's only sporadic cases of microsporidia infections were well documented in humans (reviewed in Weber et al, 1994).…”

Evaluation of pulmonary microsporidiosis in iatrogenically immunosuppressed patients

“…It is thought that many possible infections might be overlooked due to not only insufficient focus on microsporidiosis in the differential diagnosis of infections but also difficulties in detection of Microsporidia spp. in laboratory investigations (1)(2)(3)(4).…”

“…(1,2). In recent studies using genetic analyses, the zoonotic potential has clearly been documented about these parasites (3).…”