Ichthyophthiriasis: emphases on the epizootiology

White spots amidst the gold: ultrastructural and histological aspects of the chronic inflammatory response of goldfish with ichthyophthiriasis

Ichthyophthirius multifiliis, the causative agent of white spot disease, is a ciliated protozoan parasite that infects freshwater fish and induces high mortality. Outbreaks occur both in natural and production sites. The aim of the present study was to describe the lesions caused by chronic infection by I. multifiliis in goldfish (Carassius auratus) from an ornamental fish farm, highlighting important ultrastructural aspects of this protozoan. Damaged skin and gills, collected from fish with white or ulcerative skin lesions, were routinely processed for histological analysis and transmission electron microscopy. The parasitic forms present in the skin were associated with an inflammatory infiltrate consisting of macrophages, lymphocytes and other polymorphonuclear cells. The lesions associated with the presence of the parasite were organized in the form of granulomas, with macrophages in the layers closest to the parasites. A trophont-thickened membrane and induction of granulomatous inflammation were identified in this study as mechanisms for evasion of the immune response. We concluded that the presence of I. multifiliis trophonts resulted in the formation of granulomatous inflammation, whether associated or not with pathogen lysis, suggesting that the parasite can use an inflammatory response to evade the immune response.

An insight into the interaction between Argulus siamensis and Labeo rohita offers future therapeutic strategy to combat argulosis

Aquaculture and fisheries are salient flourishing sectors in the world but their sustainability is often afflicted by several pathogenic diseases. Among all the pathogenic diseases of fish, parasitic diseases are found to be a major cause of concern. Argulosis is one of the dominant parasitic problems encountered in Indian aquaculture practices. Argulus siamensis is the most prevalent argulid species harming the Indian major carp species including Labeo rohita. The major carps respond to parasitic infestation by elevating various immune relevant genes. The therapeutic chemicals, synthetic drugs and other plant extracts have made a progress in the fight against argulosis. However, there is no effective vaccine and drugs are available for this disease. Thus, designing efficient, cost-effective and eco-friendly control and treatment strategies for argulosis is presently needed. Keeping the aforementioned facts in mind, the current review elaborated the immunological interaction between A. siamensis and L. rohita, available combat tactics, highlighted the already identified vaccine candidates to design effective control measures and illustrated the use of omics technology in future to combat argulosis.

Antiprotozoal and anthelmintic activity of zinc oxide nanoparticles

Nanomaterials represent a wide alternative for the treatment of several diseases that affect both human and animal health. The use of these materials mainly involves trying to solve the problem of resistance that pathogenic organisms acquire to conventional drugs. A well-studied example that represents a potential component for biomedical applications is the use of zinc oxide (ZnO) nanoparticles (NPs). Its antimicrobial function is related, especially the ability to generate/induce ROS that affects the homeostasis of the pathogen in question. Protozoa and helminths that harm human health and the economic performance of animals have already been exposed to this type of nanoparticle. Thus, through this review, our goal is to discuss the state-of-the-art effect of ZnO NPs on these parasites.

Synergistic infection of Ichthyophthirius multifiliis and Francisella noatunensis subsp. orientalis in hybrid red tilapia (Oreochromis sp.)

Francisella noatunensis subsp. orientalis (Fno) and Ichthyophthirius multifiliis (Ich) are deadly infectious pathogens in farmed tilapia, particularly during cold season when the water temperature drops to under 25 °C. We hypothesized that infection of the ectoparasite Ich might enhance susceptibility of hybrid red tilapia (Oreochromis sp.) to the facultative intracellular bacterium Fno. To prove the hypothesis, the experiment was designed as follows. Hybrid red tilapia naturally infected by Ich at 9 ± 6 theronts/fish gills and 4 ± 3 theronts/fish skin were distributed into 5 distinct groups exposed to different concentrations of Fno. In parallel, the same number of Ich-free tilapia were challenged to only Fno in the same manner. The results showed that cumulative mortality in the Fno single infection with 2.88 × 10⁶ CFU mL^-1 of water was 25 ± 7%, whereas 100% mortality was found in the coinfection treatment at dose of 1.93 × 10⁵ CFU mL^-1 of water. No mortality was observed in both control groups (Ich-infected and Ich-free fish). The coinfected fish revealed typical clinical signs and histopathological manifestations of francisellosis and ichthyophthiriasis. This study revealed synergistic effect of the Ich and Fno infection in hybrid red tilapia leading to the exacerbated mortality. Thus, farming management of fish to be free from the Ich ectoparasite might reduce risk of francisellosis and probably other bacterial diseases in farmed tilapia.

Essential oils to control ichthyophthiriasis in pacu, Piaractus mesopotamicus (Holmberg): special emphasis on treatment with Melaleuca alternifolia

In vitro effect of the Melaleuca alternifolia, Lavandula angustifolia and Mentha piperita essential oils (EOs) against Ichthyophthirius multifiliis and in vivo effect of M. alternifolia for treating ichthyophthiriasis in one of the most important South American fish, Piaractus mesopotamicus (Holmberg), were evaluated. The in vitro test consisted of three EOs, each at concentrations of 57 μL L(-1) , 114 μL L (-1) , 227 μL L(-1) and 455 μL L (-1) , which were assessed once an hour for 4 h in microtitre plates (96 wells). The in vitro results demonstrated that all tested EOs showed a cytotoxic effect against I. multifiliis compared to control groups (P < 0.05). The in vivo treatment for white spot disease was performed in a bath for 2 h day(-1) for 5 days using the M. alternifolia EO (50 μL L (-1) ). In this study, 53.33% of the fish severely infected by I. multifiliis survived after the treatment with M. alternifolia (50 μL L (-1) ) and the parasitological analysis has shown an efficacy of nearly 100% in the skin and gills, while all the fish in the control group died. Furthermore, the potential positive effect of M. alternifolia EO against two emergent opportunistic bacteria in South America Edwardsiella tarda and Citrobacter freundii was discussed.

Are similar the parasite communities structure ofTrachelyopterus coriaceus and Trachelyopterus galeatus (Siluriformes: Auchenipteridae) in the Amazon basin?

Abstract The aim of this study was to compare the parasite communities in two sympatric host populations, Trachelyopterus coriaceus andTrachelyopterus galeatus, which were caught in tributary of the Amazon River in Brazil. All the specimens of T. galeatusand T. coriaceus were infected by one or more parasites, such as Ichthyophthirius multifiliis, Tripartiella tetramerii, Trichodina nobilis,Cosmetocleithrum striatuli, Contracaecumsp., Cystidicoloides sp., Dadaytremoides parauchenipteri and Gorytocephalus spectabilis. Seven species were common to both host fish, and there were 1-5 parasite species per host. In both hosts, trichodinids were dominant. Aggregate dispersion of ectoparasites and endoparasites was observed, with greater aggregation among endoparasites. Only the ectoparasites species showed differences in intensity and/or abundance. However, the parasite communities of the two hosts were taxonomically similar (99%) and characterized by high prevalence and high abundance of ectoparasites, but with low diversity, prevalence and abundance of endoparasites. Trachelyopterus galeatus, the host with the larger body size, presented greater variation of Brillouin diversity and evenness, while T. coriaceus had higher Berger-Parker dominance values and total numbers of parasites. This first study on these parasites ofT. galeatus and T. coriaceus showed that the life mode, size of the hosts and the availability of infective forms of the parasites were the main factors that influenced the parasite communities structure.

Ectocommensal and ectoparasites in goldfish Carassius auratus (Linnaeus, 1758) in farmed in the State of São Paulo

Concomitant infections by several parasitic genera are rare, very debilitating and often lethal to fish reared under commercial breeding conditions. Were describe a multiple and concurrent parasite infestation in cultured goldfish Carassius auratus with skin damage (nodules and/or ulceration). Fish with skin lesions underwent necropsy, and the skin and gills were scraped and examined. Histopathological examination with Hematoxylin-Eosin and Giemsa stain, and an ultrastructure study using transmission and scanning electron microscopy were conducted. In the skin, we identified multiple-parasite infestations by Gyrodactylidae, Epistylis sp., Trichodina sp., Ichthyophthirius multifiliis, Tetrahymena sp. and Ichthyobodo necator,associated with epithelial cell hyperplasia and epidermal sloughing. Although no gross lesions were observed, were identified a large number of parasites in the gills (Epistylis sp., Piscinoodinium sp., Ichthyophthirius multifiliis, Trichodina sp., Apiosoma sp., Hexamitasp. and cysts of a trematode digenean). The observed trematodes were not identified. The associated microscopic lesions were epithelial hypertrophic and hyperplasic and exhibited fusion of secondary lamellae and epithelial cell detachment. This is the first description of a protozoan Vorticella sp. parasitizing goldfish in Brazil. Multiple ectoparasitism by protozoa and Platyhelminthes, with or without apparent tissue damage, can be fatal for goldfish raised on farms with poor management.

Phytotherapy as an alternative for treating fish disease

Intensification of livestock rearing often promotes an increase in inappropriate practices that disregard care for the environment, animal health, and workers' health. Intensive fish farming systems are often associated with higher stocking density and massive use of artificial feed. Currently, outbreaks of parasitic, bacterial, and fungal diseases act as major limiting factors for fish farming, meaning that producers have to make use of massive amounts of antibiotics, disinfectants, and pesticides in order to control mortality and avoid huge economic losses. Because of adverse effects on the aquatic environment, terrestrial organisms, and human health (both fish handlers and consumers), this therapy has been criticized. Use of herbal medicines within animal production has shown promise, in that it is natural and biodegradable and has antimicrobial activity against various pathogens, including those relating to fish. Recently, researchers have reported promising effects from many herbal medicines for treating parasitic diseases caused by protozoa and metazoa, and broad activity against bacteria and fungi. This review addresses the current issues regarding indiscriminate use of chemicals and antibiotics in aquaculture and discusses the main findings and methodologies of the latest research on herbal medicines to stimulate and accelerate research in this field, especially in developing countries.