Encephalitozoon cuniculi (E. cuniculi) is a mammalian microsporidial pathogen with world-wide distribution. An important cause of neurologic and renal disease in rabbits, E. cuniculi can also cause disease in immunocompromised people.
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The Romans used the cuniculi of Veii to mine into the citadel. Cuniculi have multiple purpose. One of them was to keep villages and cities safe from erosion. North-west of Rome 42 km of cuniculi have been discovered; more than 22 km in and around Veii.
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Cuterebra cuniculi is a species of new world skin bot fly in the family Oestridae.
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The Italian community of Formello to the north of Veii was named after the numerous cuniculi there.Everitt, A (2012), The Rise of Rome, page 122. Cuniculi could take any form from trenches to a complex system of tunnels. The uses were multiple: irrigation, drainage, diversion, supply, and so on.
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Compared to E. cuniculi which encodes about 2000 massive genes at 2.9 Mbp, E. intestinalis had a reduced gene complement and genome size (2.3 Mbp) because of a high degree of host dependency. E. intestinalis lack large gene blocks of sequence in its subtelomeric regions unlike E. cuniculi. However, E. intestinalis and E. cuniculi share a conserved gene content, order and density over most of their genomes which have similar GC content. They also contain the same complement of transfer RNAs and ribosomal RNAs.
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Fosso dei Costaroni, remains of an Etruscan cuniculus at Formello. A cuniculus, plural cuniculi, is a diversionary water channel, used by ancient civilizations on the Italian Peninsula. As the general ancient Italian use derives from the Etruscan use, the term has a special significance of Etruscan cuniculi. The city of Veii was noted for them.
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E. cuniculi infections in the eye cause cataract formation, white intraocular masses, and uveitis. Symptoms usually occur in young rabbits, and only one eye is generally affected. Rabbits with ocular lesions related to encephalitozoonosis are usually otherwise healthy, and tolerate vision loss well. E. cuniculi has a predilection for the kidneys and can cause chronic or acute kidney failure.
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Psoroptes cuniculi The rabbit ear mite, Psoroptes cuniculi, is larger than Otodectes cynotis. It causes thick firm debris to form in the ear canal, and can eventually migrate to the skin of the outer ear and face. Symptoms include scratching and shaking of the head. Treatment includes topical selamectin, or injections of ivermectin and frequent cleanings of the rabbit's environment.
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Because the E. cuniculi genome contains genes related to some mitochondrial functions (for example, Fe-S cluster assembly), it is possible that microsporidia have retained a mitochondrion-derived organelle.
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Rabbit with uveitis caused by Encephalitozoon cuniculi Up to 80% of rabbits in the United States and Europe are serologically positive for E. cuniculi, which indicates that they have been exposed to the organism. Most of these animals will remain asymptomatic and never show signs of disease. Only a small minority of infected rabbits develop the disease encephalitozoonosis. The most common clinical signs associated with this disease involve the central nervous system, eyes, and kidneys.
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E. cuniculi is an important opportunistic pathogen in people, particularly those immunocompromised by HIV/AIDS, organ transplantation, or CD4+ T-lymphocyte deficiency. As this organism is more common in animals than people it is likely a zoonotic disease. Three different strains of E. cuniculi have been identified, and are classified as I (rabbit), II (mouse), and III (dog). Human-to-human transmission is possible via transplantation of solid organs from an infected donor.
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Encephalitozoon cuniculi is a microsporidial parasite carried by many mammals, including rabbits, and is an important opportunistic pathogen in people immunocompromised by HIV/AIDS, organ transplantation, or CD4+ T-lymphocyte deficiency.
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Wry neck (or head tilt) is a condition in rabbits that can be fatal, due to the resulting disorientation that causes the animal to stop eating and drinking. Inner ear infections or ear mites, as well as diseases or injuries affecting the brain (including stroke) can lead to wry neck. The most common cause, however, is a parasitic microscopic fungus called Encephalitozoon cuniculi (E. cuniculi). Note that: "despite approximately half of all pet rabbits carrying the infection, only a small proportion of these cases ever show any illness".
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Microsporidian spore with an extruded polar tubule inserted into a eukaryotic cell. The infective form of microsporidia (E. cuniculi) is a resistant spore which can survive for a long time in the environment. The spore extrudes its polar tubule and infects the host cell.
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Spilopsyllus cuniculi, the rabbit flea, is a species of flea in the family Pulicidae. It is an external parasite of rabbits and hares and is occasionally found on cats and dogs and also certain seabirds that nest in burrows. It can act as a vector for the virus that causes the rabbit disease myxomatosis.
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The assay is adaptable to the clinical laboratory and represents the first real‐time PCR assay designed to detect Encephalitozoon species. Melting temperature analysis of the amplicons allows for the differentiation of three Encephalitozoon species (E. intestinalis, E. cuniculi, and E.hellem).D. M. Wolk, S. K. Schneider, N. L. Wengenack, L. M. Sloan, and J. E. Rosenblatt.
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E. cuniculi also infects rodents, and the organism has been detected in the feces of 13% of pet birds. A small percentage of healthy people have antibodies to the organism, indicating previous exposure. Seroprevalence rates are higher in immunocompromised people, and in those who live in or have visited tropical countries. Most infections do not result in clinical disease.
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First identified in rabbits, E. cuniculi infections have been reported worldwide in over 20 mammalian species, including humans. Prevalence in pet rabbits is high, with 23-75% having antibodies to the disease. Studies of healthy dogs have found a 0-38% prevalence. Cats appear to be relatively resistant to the organism, although experimental infections in kittens with feline leukemia virus have been described.
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E. cuniculi spores are usually shed in urine, but can also be found in the feces and respiratory secretions of infected animals. Spores can be detected in urine 38-63 days after infection, with intermittent shedding thereafter. Ingestion of spores is the main route of transmission, although inhalation of spores can also occur. Transplacental and intrauterine infections have been documented in rabbits.
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Psoroptes ovis infests sheep worldwide and can be a serious welfare and animal production problem, mainly for sheep, but also cattle. Psoroptes cuniculi infests rabbits, mainly on their outer ear. Chorioptes bovis infestations are found on cattle, sheep and horses but do not cause the severe reactions associated with Psoroptes mites. Other common psoroptic mites are in the genera Chorioptes and Otodectes.
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It is currently difficult to definitively diagnose E. cuniculi infections in live rabbits. A presumptive diagnosis is often made based on consistent clinical signs and high antibody levels. Serology tests that look for IgG antibodies are commonly run, and can be used to rule out the disease if negative. However, a positive IgG titer cannot differentiate an active infection from a previous infection or an asymptomatic carrier state.
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In 2009 a first draft of H. tvaerminnensis genome was sequenced (under the name of Octosporea bayeri). The whole genome has approximately the size of 24.2 Mega-bases (Mb). This stands in contrast to other sequenced microsporidia genomes (for example the compact 2.9 Mb genome of the obligate parasite Encephalitozoon cuniculi) which are reduced in size. It is suggested that H. tvaerminnensis genome is the largest known microsporidian genome.
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E. cuniculi is a spore-forming unicellular parasite belonging to the phylum Microsporidia. Microsporidia are obligate intracellular parasitic fungi infecting many animal groups. Lacking mitochondria and peroxysomes, these unicellular eukaryotes were first considered a deeply branching protist lineage that diverged before the endosymbiotic event that led to mitochondria. The discovery of a gene for a mitochondrial-type chaperone combined with molecular phylogenetic data later implied that microsporidia are atypical fungi that lost mitochondria during evolution.
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Pictorial representation of diplococcus formation in M. catarrhalis. Phylum: Proteobacteria Class: Gammaproteobacteria Order: Pseudomonadales Family: Moraxellaceae Genus: Moraxella The genus Moraxella belongs to the family Moraxellaceae. This genus, Moraxellaceae, comprises gram-negative coccobacilli bacteria: Moraxella lacunata, Moraxella atlantae, Moraxella boevrei, Moraxella bovis, Moraxella canis, Moraxella caprae, Moraxella caviae, Moraxella cuniculi, Moraxella equi, Moraxella lincolnii, Moraxella nonliquefaciens, Moraxella osloensis, Moraxella ovis and Moraxella saccharolytica, Moraxella pluranimalium. However, only one has a morphology of diplococcus, Moraxella catarrhalis.
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Red foxes are not readily prone to infestation with fleas. Species like Spilopsyllus cuniculi are probably only caught from the fox's prey species, while others like Archaeopsylla erinacei are caught whilst traveling. Fleas that feed on red foxes include Pulex irritans, Ctenocephalides canis and Paraceras melis. Ticks such as Ixodes ricinus and I. hexagonus are not uncommon in red foxes, and are typically found on nursing vixens and kits still in their earths.
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Some vets now recommend treating rabbits against E. cuniculi. The usual drugs for treatment and prevention are the benzimidazole anthelmintics, particularly fenbendazole (also used as a deworming agent in other animal species). In the UK, fenbendazole (under the brand name Panacur Rabbit), is sold over-the-counter in oral paste form as a nine-day treatment. Fenbendazole is particularly recommended for rabbits kept in colonies and as a preventive before mixing new rabbits with each other.
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Tests for IgM antibodies are also available, but again positive results cannot distinguish between active and latent infections. Polymerase chain reaction (PCR) has long been established as the standard technique for detection of microsporidia in humans, and attempts to apply this to rabbits are ongoing. Studies have found that PCR of liquified lens material is a reliable means of diagnosing E. cuniculi uveitis in rabbits, but PCR testing of rabbit urine and cerebrospinal fluid is not reliable.
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A few studies have shown that fenbendazole, a benzimidazole drug, can prevent and treat naturally acquired and experimentally induced E. cuniculi infections. Unfortunately the elimination of spores from the central nervous system does not always result in resolution of clinical signs. Adverse reactions to benzimidazole drugs, including injury to the small intestine and bone marrow, have been reported in rabbits. Practitioners should strictly adhere to recommended dosages and treatment intervals, and consider monitoring complete blood counts during treatment.
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In Britain, the primary carrier of myxomatosis is the flea Spilopsyllus cuniculi, while in Australia it is mosquitoes. Rabbit haemorrhagic disease (RHD), also known as viral haemorragic disease (VHD) or rabbit calicivirus disease in Australia, is specific to the European rabbit, and causes lesions of acute necrotising hepatitis, disseminated intravascular coagulation, and haemorraging, mainly in the lungs. Susceptible specimens may die within 30 hours of infection. Most rabbits in the UK are immune to RHD, due to exposure to a weaker strain.
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Under ideal conditions of temperature, food supply, and humidity, adult fleas can live for up to a year and a half. Completely developed adult fleas can live for several months without eating, so long as they do not emerge from their puparia. Optimum temperatures for the flea's life cycle are 21 °C to 30 °C (70 °F to 85 °F) and optimum humidity is 70%. Adult female rabbit fleas, Spilopsyllus cuniculi, can detect the changing levels of cortisol and corticosterone hormones in the rabbit's blood that indicate it is getting close to giving birth.
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Where it nests on the tundra in the far north, the Arctic skua (Stercorarius parasiticus) is a terrestrial predator, but at lower latitudes, it is a specialised kleptoparasite, concentrating on auks and other seabirds. It harasses puffins while they are airborne, forcing them to drop their catch, which it then snatches up. Both the guillemot tick Ixodes uriae and the flea Ornithopsylla laetitiae (probably originally a rabbit flea) have been recorded from the nests of puffins. Other fleas found on the birds include Ceratophyllus borealis, Ceratophyllus gallinae, Ceratophyllus garei, Ceratophyllus vagabunda, and the common rabbit flea Spilopsyllus cuniculi.
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The popular consensus at the moment is that introns arose within the eukaryote lineage as selfish elements. Early studies of genomic DNA sequences from a wide range of organisms show that the intron-exon structure of homologous genes in different organisms can vary widely. More recent studies of entire eukaryotic genomes have now shown that the lengths and density (introns/gene) of introns varies considerably between related species. For example, while the human genome contains an average of 8.4 introns/gene (139,418 in the genome), the unicellular fungus Encephalitozoon cuniculi contains only 0.0075 introns/gene (15 introns in the genome).
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They were also found to host rabbit fleas (Spilopsyllus cuniculi), stickfast fleas (Echidnophaga myrmecobii), lice (Haemodipsus setoni and H. lyriocephalus), and mites (Leporacarus gibbus). European brown hare syndrome (EBHS) is a disease caused by a calicivirus similar to that causing rabbit haemorrhagic disease (RHD) and can similarly be fatal, but cross infection between the two mammal species does not occur. Other threats to the hare are pasteurellosis, yersiniosis (pseudo- tuberculosis), coccidiosis and tularaemia, which are the principal sources of mortality. In October 2018, it was reported that a mutated form of the rabbit haemorrhagic disease virus (RHDV2) may have jumped to hares in the UK. Normally rare in hares, a significant die-off from the virus has also occurred in Spain.
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