Identification of Larval Eustrongylides (Nematoda: Dioctophymatoidea) sp. from Channa punctata Bloch, 1793 by Morphological and Molecular Techniques

Objective: This study aimed to identify the larval form of Eustrongylides sp. isolated from the visceral organs of Channa punctata (Bloch, 1793) using morphological and molecular methods. Methods: Fishes were collected from fish farms in Nadia and North 24 Paraganas for the collection of nematodes. The visceral organs were dissected and kept in 0.67% normal saline. Nematodes collected from the abdominal regions and visceral organs for light microscopy study were fixed in 70% ethanol. Morphological features were studied by placing the nematodes in lactophenol. The specimens were later preserved in 70% ethanol containing 5% glycerine. Specimens processed for scanning electron microscopy were fixed in 2.5% glutaraldehyde and postfixed in 1% osmium tetraoxide. Proper identification was done by using standard methology. Molecular studies were performed for the 18S rRNA, ITS1, 5.8S rRNA, ITS2 and 28S rRNA gene fragments using polymerase chain reaction amplification, sequencing and phylogenetic analysis. Results: The morphological characteristics of nematodes were described with the help of light and scanning electron microscopy. Additional features not described earlier like dimensions and shape of the cephalic papillae, absence of somatic papillae, presence of caudal papillae, were identified for the first time. Moreover, molecular studies with ITS regions further confirmed the identification of the nematode. Conclusion: Thus the use of morphotaxonomy along with molecular techniques would help in proper identification of Eustrongylides sp infecting edible fish. Studies on the nematode would help toexplore the intermediate as well as paratenic hosts of the parasite. Data in this regard would contribute significantly to the fish database in regard to parasites infesting edible fishes.

Occurrence of Eustrongylides sp. (Nematoda: Dioctophymatidae) in Fish Species Collected in the Peruvian Amazonia and Its Implications for Public Health.

PURPOSE: The present study aims to report the occurrence of Eustrongylides sp. in some neotropical fish species commercialized in the Peruvian Amazonia. METHODS: Samples of young farmed Arapaima gigas were collected from a fish farmer; young Brachyplatystoma tigrinum were acquired from a fish exporter and samples of adult specimens of Acestrorhynchus falcirostris, Pseudoplatystoma punctifer, Cichla monoculus, Hoplias malabaricus, Hydrolycus scomberoides, Raphiodon vulpinus, and Serrasalmus rhombeus were acquired from a fish market of Iquitos, Loreto-Peru. Samples were transported to the "Laboratorio de Parasiología y Sanidad Acuícola" from "Instituto de Investigaciones de la Amazonía Peruana" located in Iquitos, Peru. RESULTS: Larvae L4 of Eustrongylides sp. were found in the host body, in the muscle, and in the visceral cavity of studied fish species. Notorious damages were reported in young A. gigas (lumps in the muscle, inflammation and severe redness of the skin) and in young B. tigrinum (perforation of the abdominal cavity), while in adult specimens of the remaining species, no external damage was reported. CONCLUSION: The presence of Eustrongylides sp. in various fish species collected in the city of Iquitos-Peru contributes to the distribution of this parasite in the Peruvian Amazon, reporting it, for the first time in this country. Its presence in the muscle of various fish species commercialized in fish markets, warm a possible public health concern and implications for their marketability in the city of Iquitos, Peru.

Eustrongylides sp. (Nematoda, Dioctophymatoidea) parasitizing Hoplias malabaricus (Actinopterygii: Erythrinidae) collected from the state of Rio de Janeiro, Brazil / Eustrongylides sp. (Nematoda, Dioctophymatoidea) parasitando Hoplias malabaricus (Actinopterygii: Erythrinidae) coletados do Estado do Rio de Janeiro, Brasil

Abstract Hoplias malabaricus (Characiformes, Erythrinidae), trahira, is a neotropical freshwater fish of economic and public health significance. A total of 45 specimens of H. malabaricus commercialized in the municipality of Magé, state of Rio de Janeiro, Brazil, were acquired between April 2016 and April 2018 to investigate the presence of nematode larvae. Twenty of the fish were found parasitized by 347 fourth-stage nematode larvae identified taxonomically as Eustrongylides sp. using morphological, morphometric and molecular data. The parasitic indices were: prevalence 44.44%, mean intensity 17.35, mean abundance 7.71, and range of infection 2-40. Infection sites were musculature, mesentery, abdominal cavity, and serosa of intestine, stomach and liver. This is the first report of Eustrongylides sp. larvae parasitizing H. malabaricus in the state of Rio de Janeiro.

Resumo Hoplias malabaricus (Characiformes, Erythrinidae), traíra, é um peixe neotropical de água doce que tem significante impacto na economia e saúde pública. De abril de 2016 a abril de 2018, foram adquiridos 45 espécimes de H. malabaricus comercializados no município de Magé, Estado do Rio de Janeiro, Brasil. Os peixes foram necropsiados e filetados para investigação da presença de larvas de nematoides. Vinte dos peixes coletados estavam parasitados por 347 larvas de nematoides, identificadas taxonomicamente como larvas de quarto estágio de Eustrongylides sp. usando-se dados morfológicos, morfométricos e moleculares, apresentando os seguintes valores: prevalência de 44,44%, intensidade média de 17,35, abundância média de 7,71, e amplitude de variação da infecção de 2-40. Os sítios de infecção foram musculatura, mesentério, cavidade abdominal e serosas do intestino, estômago e fígado. Este é o primeiro registro de larvas de Eustrongylides sp. parasitando H. malabaricus no Estado do Rio de Janeiro.

A study of the endohelminths of the European perch Perca fluviatilis L. from the central region of the Danube river basin in Slovakia.

The European perch Perca fluviatilis L. serves as a host of different endohelminths of Trematoda, Cestoda, Nematoda, and Acanthocephala. Its natural range covers freshwater basins throughout much of Europe, including the Danube. Since information about endohelminths of European perch from this international river basin has been rather sporadic, the parasitological examinations of 700 perch from the central region of the Danube river basin in Slovakia were performed in October 2017 and April 2018. The larval stages of Triaenophorus nodulosus (Cestoda) were found in cysts located in the perch liver and adults of Proteocephalus percae (Cestoda) were isolated from the intestine. The larval stages of Eustrongylides sp. (Nematoda) and metacercariae of Clinostomum complanatum (Trematoda), both potential causative agents of fish-borne zoonoses, were found in the musculature. Spatial and seasonal differences in the occurrence of currently detected helminths were discussed with data on biological and environmental conditions of particular sampling site.

Pathology associated with larval eustrongylides sp. (nematoda: Dioctophymatoidea) infection in galaxias maculatus (actinopterygii: Galaxiidae) from patagonia, Argentina.

Helminth infections within tissues tend to be subjected to a host response that can include encapsulation and melanization to isolate the parasite. The effectiveness of this response depends on the host species. During a survey of parasites of the native fish, Galaxias maculatus, we found conspicuous, strongly melanized exterior cysts located in the caudal peduncle of the fish. Dissection of these cysts exposed larval nematodes whose morphometrical features allowed their identification as Eustrongylides sp. Species of this genus are distributed worldwide. Galaxias maculatus was previously reported as second intermediate host to Eustrongylides sp. larvae, and the aquatic bird Podiceps major was cited as definitive host of Eustrongylides tubifex in Andean Patagonian lakes. The site of infection in the fish, and the host's response are unique among infections by larvae of Eustrongylides sp. in fishes, so the objective of this study was to describe the histological injury caused by larvae of the genus Eustrongylides parasitizing G. maculatus. Samples of fish were taken near the shore of Gutiérrez lake, in northwestern Patagonia. Some larval morphometric features were described to confirm the identity of larvae to generic level. Histopathological analysis (tissues sectioned at 5-7 µm, stained with Hematoxylin and Eosin, and Masson's Trichrome) of the caudal peduncle revealed almost complete disappearance of the epaxial musculature due to compressive atrophy and a chronic inflammatory response, associated mainly with a dense fibrotic capsule and an intense melanic deposit. This is the first description of the histopathology of an external cyst caused by Eustrongylides sp. larvae in fishes.

Análise do parasitismo por Contracaecum sp. e Eustrongylides sp. em cacharas, Pseudoplatystoma fasciatum (Linnaeus, 1766) (Pisces: Pimelodidae) provenientes do rio Cuiabá, Mato Grosso, Brasil / Analisys of the parasitism by Contracaecum sp. and Eustrongylides sp. in cacharas, Pseudoplatystoma fasciatum (Linnaeus, 1766) (Pisces: Pimelodidae) from Cuiabá river, Mato Grosso, Brazil

Cento e quarenta e nove espécimes de cacharas (Pseudoplatystoma fasciatum) foram capturados do rio Cuiabá, estado de Mato Grosso, durante o período de outubro de 2004 a abril de 2006, para análise do parasitismo por larvas de nematóides. Encontrou-se prevalência de 100% destes peixes parasitados por larvas de Contracaecum sp. e/ou Eustrongylides sp. A análise do parasitismo foi feita por registro da prevalência e localização das larvas encontradas. Cinco cacharas (3,35%) apresentaram parasitismo por larvas de Contracaecum sp. na musculatura esquelética e 147 (98,65%) no mesentério. Cinquenta cacharas (33,55 %) apresentaram larvas de Eustrongylides sp. na musculatura esquelética e 117 (78,52%) no mesentério. A intensidade média de infecção foi de 15,42 larvas/peixe para Contracaecum sp. e de 6,37 larvas/peixe para Eustrongylides sp. O peso médio dos peixes examinados foi de 5,59 kg (1,9-10,5 kg) e o comprimento total médio de 82,39 cm (63,5-105 cm). Não foi observada correlação entre parâmetros biométricos como comprimento total e peso dos hospedeiros e a intensidade de infecção.

One hundred and forty-nine cacharas (Pseudoplatystoma fasciatum) specimens were captured from Cuiabá river, Mato Grosso State, between october of 2004 to april of 2006, intending to analyse the parasitism by nematode larvae. The prevalence was 100% to parasitism by Contracaecum sp. and/or Eustrongylides sp. larvae. The analysis of the parasitism were done by prevalence record and the localization of the larvae founded. Five cacharas (3,35 %) presented parasitism by Contracaecum larvae in the skeletal muscle and one hundred and forty-seven (98,65 %) on the mesenterium. Fifty cacharas (33,55%) presented Eustrongylides sp. larvae in the skeletal muscle and one hundred seventeen (78,52%) on the mesenterium. The mean intensity of infection was 15,42 larvae/fish for Contracaecum sp. and 6,37 larvae/fish for Eustrongylides sp. The average of weight to the examined fishes was 5,59 kg (1,9-10,5 kg) and the average of the total length was 82,39 cm (63,5-105 cm). Correlation between biomethric parameters as host´s total length and weight and the intensity of infection was not observed.