Low pH, dissolved oxygen and high temperature induces Thelohanellus rohita (myxozoan) infestation in tropical fish, Labeo rohita (Hamilton)

Blood glucose profile as a rapid method for observing Koi carp (Cyprinus carpio) health status - case study of ectoparasites in Blitar, Indonesia

Assessment of fish health is one of the efforts of farmers in minimizing losses due to disease. Rapid tests on fish health can be done through blood observations. This study aimed to determine the blood glucose profile of koi carp due to ectoparasite infestation from the level of blood glucose. The results showed that reported parasites from Blitar's koi carp were Trichodina, Dactylogyrus, Gyrodactylus, Myxobolus, Thelohanellus, Ichthyophthirius, and Argulus. Trichodina showed the highest prevalence (100%) in this case while Thelohanellus was the highest intensity level (93.8±16.3). The results of blood glucose level measurement based on parasite infestation levels showed no significant difference (p>0.05) though the health problems caused by parasites in light, medium or heavy infestation. This research also indicated that the blood glucose profile could be used as a rapid method to detect fish health caused by parasites. We suggest that other variables such as nutritional status, life stage or feeding must be conducted to ensure the glucose role in parasite identification as a rapid method for the future work.

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

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.

Prevalence, site and tissue preference of myxozoan parasites infecting gills of cultured fingerlings of Indian major carps in District Fatehgarh Sahib, Punjab (India)

A study was undertaken to investigate the prevalence rate, site preference and extent of damage caused by myxosporidian parasites in Punjab, India. During the 6 months study, 600 carp fingerlings belonging to 4 genera i.e. Labeo rohita Hamilton, Cirrhinus mrigala Hamilton, Catla catla Thail and Carassius carassius were randomly collected from the polyculture nursery ponds located in different villages District Fatehgarh Sahib, Punjab. Organs such as fins, scales, gills, intestine, kidney, and eye-ball were examined for the presence of myxozoan parasites. In this study, gills of 321 (53.50%) were found to be infected with as many as 10 species of myxosporean parasites belonging to the genus Myxobolus. Gills were examined for the presence of plasmodia and infected organs were processed for histology. The gill plasmodial index (GPI) was counted for all the 10 species and this revealed a mild to severe infection was recorded. M. knobii, M. majraiensis, M. markiwi, M. naini, M. rocatlae, M. vascularis and M. venkateshi formed intralamellar vascular type of plasmodia (LV₁), M. nanokiensis formed (LV₃) and M. potularis and M. slendrii formed intrafilamental type of plasmodium (FV₂). Out of 231 infected fishes, mixed infection was recorded in 44 fishes (13.70%), which exhibited biparasitism and polyparasitism. No infection was recorded in exotic carp i.e. C. carassius. Physicochemical parameters of water were also recorded for the period of 6 months comprising 4 months of winter and 2 months of spring. The present study indicated that the prevalence of myxozoan parasite was 43% in November (24.0 °C) and increased to 54% with the decrease in temperature (22.65 °C).