Pathological and immunological analyses of Thelohanellus kitauei (Myxozoa:Myxosporea) infection in the scattered mirror carp, Cyprinus carpio

Abstract

Thelohanellus kitauei is a spore-forming myxosporean parasite prevalent in scattered mirror carp (Cyprinus carpio) that generates numerous cysts in the intestine and causes mass mortality in fish. To investigate the infection and mortality induced by T. kitauei in pond-reared farms in Luo-Jiang (104°51’N, 31°31’E), southwest China, morphological and molecular analyses of infected fish were conducted. Natural and specific immune indicators were further evaluated to determine the immunological effects of response to parasitic infection. The infectious parasite was identified as Thelohanellus kitauei based on morphological, 18S rDNA and infectious characteristics. Scattered mirror carp was determined as the specific intermediate host of the parasite. However, T. kitauei still caused considerable damage to the fish, in particular, injury and blockage of the intestines, resulting in malnutrition and even death. The mature spores of T. kitauei colonize the intestinal submucosa of carp and form cysts of various sizes that block the intestinal tract and release spores into the enteric cavity upon rupture, leading to the next phase of T. kitauei growth. Moreover, T. kitauei-infected carp showed weaker innate immunity. IgM is involved in the fight against parasitic infection while cytokines, such as IL-6, IL-1β and TNF-α, had an impact on infection processes. To our knowledge, this is the first report to show that T. kitauei infects and causes death in scattered mirror carp. Our collective findings from systematic pathology, morphology and immunology experiments provide a foundation for further research on infections by this type of parasite and development of effective treatment strategies.

Use of accelerometer technology for individual tracking of activity patterns, metabolic rates and welfare in farmed gilthead sea bream (Sparus aurata) facing a wide range of stressors

“…Meanwhile, AEFishBIT measurements of respiratory frequency are of diagnostic value and a highly valuable complement to other diagnostic techniques, as the apparent reduction of metabolic rates (respiratory frequency) reflected the different states of the progression of this model of parasitic enteritis. These results are in agreement with the lethargy observed in our parasitized fish and in other myxozoan infections in which unresponsiveness, swimming weakness, and lethargy has been reported (Liu et al, 2019). This can be viewed as a characteristic feature of the metabolic rearrangements occurring during the progression of chronic disease, which would be indicative of a hypometabolic state as part of the host defence mechanisms that also occur in other models of mucosal parasitic infections in fish (Piazzon et al, 2019a).…”

Morphological and molecular studies on two myxosporean infections of cyprinid fishes: Thelohanellus pyriformis from tench and Thelohanellus cf. fuhrmanni from nase

“…fuhrmanni found together in a cyst caused well observable tumors in the nostrils of the nase. Similar nodules with pathogenic characters were found in the skin of Cyprinus carpio infected by T. kitauei ( Egusa and Nakajima, 1981 ; Zhai et al, 2016 ; Liu et al, 2019 ) and in Cyprinella venusta infected by T. magnacysta ( Ksepka et al, 2020 ).…”

“…Tench as a single member of Tincinae, and nase as a member of Leuciscinae are relatively distinct inside the family Cyprinidae, therefore it is unlikely that T. pyriformis could infect other cyprinids than tench. Recent publications ( Shin et al, 2014 ; Lewisch et al, 2015 ; Liu et al, 2014 , 2019 ) using molecular data suggest the relatively strict host specificity on Thelohanellus spp. of the common carp and goldfish ( Carassius auratus L.).…”

Genetic Diversity of Serine Protease Inhibitors in Myxozoan (Cnidaria, Myxozoa) Fish Parasites

“…The numerous parasite plasmodia cause swellings and often block the intestinal lumen of affected fish, thus the infection may result in high mortality. Infection triggers heavy cellular immune reactions in fish, with elevated level of TNF-alpha, IL-1beta, IL-6, and IgM [ 49 ]. To overcome the host reaction, the parasite may need an extensive immunomodulatory strategy for successful invasion, dissemination, and development.…”