Immunohistochemical Detection of Encephalitozoon cuniculi in Ocular Structures of Immunocompetent Rabbits

Abstract

Simple SummaryEncephalitozoonosis is a common infectious disease widely spread among rabbits. Its causative agent, Encephalitozoon cuniculi, is considered to be transmissible to humans. In rabbits, clinical signs include discoordination, head tilt, excessive water intake, excessive urination and cataracts. This study investigates, for the first time, whether the E. cuniculi organism can be detected in ocular structures in healthy adult rabbits after experimental oral infection using immunohistochemistry—detection of the organism in the tissue using a specific staining method. In infected animals, E. cuniculi spores were detected in many ophthalmic structures (periocular connective tissue, sclera, cornea, choroidea, iris, retina and lens) as early as 2 weeks after infection. There were no signs of inflammatory lesions in any of the ocular tissues examined at 2, 4, 6 and 8 weeks after infection. E. cuniculi was also detected in the lens of adult rabbits, which indicates that ways of lens infection other than intrauterine and haematogenic are possible. This information can help to understand E. cuniculi dissemination to various ocular tissues structures after oral infection.AbstractEncephalitozoonosis is a common infectious disease widely spread among rabbits. Its causative agent, Encephalitozoon cuniculi, is considered as a zoonotic and emerging pathogen capable of infecting both immunocompetent and immunocompromised hosts, including humans. In rabbits, clinical signs include neurological, kidney and ocular disease. The aim of this study was to detect E. cuniculi in ocular structures in immunocompetent rabbits after experimental oral infection using immunohistochemistry. In infected animals, E. cuniculi spores were present in periocular connective tissue, sclera, cornea, choroidea, iris, retina and lens, as a round to ovoid organism reacting with a specific anti-E. cuniculi monoclonal antibody as early as 2 weeks after infection. There were no signs of inflammatory lesions in any of the ocular tissues examined at 2, 4, 6 and 8 weeks after infection. In the present study, E. cuniculi was also detected in the lenses of adult rabbits, which indicates that ways of lens infection other than intrauterine and haematogenic are possible.

Renal pathology in wild European rabbits

“…Furthermore, we have focused on the assessment of renal pathology in wild rabbits, and with respect to potential E. cuniculi infection; we did not perform PCR, immunohistochemistry, corresponding serology or histology of other potentially affected organs, such as the brain or ocular tissues. 16,17 In spite of these limitations, our findings add weight to the assertion that E. cuniculi may not currently be highly prevalent in wild rabbits in the UK, and our data raise interesting questions regarding the apparent discrepancy between the prevalence of E. cuniculi in wild and domestic UK rabbits. 4,5,8,18 It is possible that other wild animals, such as wild rodents and foxes, may constitute more notable reservoirs of infection and may have the potential to infect domestic pet rabbits.…”

“…Seasonality of sampling was also unequal. Furthermore, we have focused on the assessment of renal pathology in wild rabbits, and with respect to potential E. cuniculi infection; we did not perform PCR, immunohistochemistry, corresponding serology or histology of other potentially affected organs, such as the brain or ocular tissues 16,17 …”

Encephalitozoon cuniculi Infection of Domestic Rabbits (Oryctolagus cuniculus) in Slovenia between 2017 and 2021

“…The disease is widespread among laboratory, farm, and pet rabbits. According to some studies, serological testing shows high seroprevalence rates (35-68%) across several countries [3,7,8]. These results suggest that E. cuniculi infection is ubiquitous in rabbits [9,10].…”

Feline intralenticular Encephalitozoon cuniculi: three cases from California

“…5 In veterinary ophthalmology, E cuniculi is predominantly known as a cause of cataracts and phacoclastic uveitis in rabbits; 6,7 after transplacental transmission, spores are speculated to enter the lens via the lenticular blood supply while it is still present. 8 However, a recent study with immunohistochemical evidence of intralenticular E cuniculi after oral infection in 4-month-old, immunocompetent, specific pathogen-free rabbits 9 suggested that alternative mechanisms for lens infections are possible. Reports of ocular involvement in other species are limited and include cataract and uveitis in a snow leopard in France, 10 cataract, uveitis and chorioretinal lesions in dogs in Europe, 11 keratitis and uveitis in an American cat, 12 polyarteritis nodosa and cataract in a blue fox, 13 cataract and neurologic lesions in mink in Norway 14 and keratoconjunctivitis in an American cockatoo.…”