Occurrence and abundance of zoonotic nematodes in snapper Chrysophrys auratus, a popular table fish from Australian and New Zealand waters

In Australia and New Zealand (NZ), snapper Chrysophrys auratus is known for delicate mild flavoured flesh and is a favoured species to serve raw as sashimi or in sushi. The diet of snapper includes a variety of intermediate hosts of larval nematodes, and as a result, snapper has potential to become highly infected with zoonotic/non-zoonotic nematodes. The aims of this study were to survey nematodes in snapper from Australia and New Zealand waters and to identify nematode species using combined morphological and molecular methods. The zoonotic potential of nematodes identified in this study are discussed. A total of 112 snapper were purchased from the Sydney fish market, New South Wales, Australia. Fish were dissected and only the visceral content and digestive tract were examined for nematode infection. Parasites were initially identified by the microscopic method as four different types belonging to the families Anisakidae (Anisakis types I & III, and Terranova type II) and Cucullanidae (Dichelyne spp.). All Anisakidae nematodes were at infective stages. Species-level identification was actualised through sequencing of the internal transcribed spacer (ITS-1, 5.8S, ITS-2) regions. The Anisakis types I & III were confirmed as Anisakis pegreffii and A. brevispiculata, respectively of which A. pegreffii is considered globally as a zoonotic nematode. The specific identification of Terranova type II and Dichelyne spp. was not possible as no comparable sequence data were available in GenBank. The phylogenetic tree clustered Anisakis types I & III with A. pegreffii and A. brevispiculata, respectively; Terranova type II sequences as a separate clade with previously identified larval and adult Terranova and Pseudoterranova species. Based on phylogenetic analyses the present Cucullanid specimens were assigned herein as Dichelyne cf. pleuronectidis, and an unknown species Dichelyne sp. 1. This study represents the first host record globally for zoonotic Anisakid nematodes in this popularly consumed table fish and a new region record for D. cf. pleuronectidis and Dichelyne sp. 1. Further investigation is required, using more comprehensive parasite detection and recovery methods, to assess the health risk these nematodes may pose to human and fish health in Australia/NZ.

Cucullanus bulbosus (Lane, 1916) Barreto, 1918 (Nematoda, Cucullanidae) from the common ponyfish Leiognathus equulus (Leiognathidae): Morphology and molecular study

The common ponyfish Leiognathus equulus is a marine fish species with very high commercial value. Little information is available about its parasitic infections. Based on light and scanning electron microscopy, as well as sequencing and analysis of the partial regions of the ITS-1, 18S rRNA, COX1 genes, were employed for the systematic evaluation of a nematode parasite, which it first isolated from L. equulus in Jeddah Province, Red Sea, Saudi Arabia. Results revealed that this nematode parasite closely resembles the previously described Cucullanus bulbosus. Microscopic examination showed that it distinguished from congeners by the unique structure of hemispherical elevation at pseudobuccal capsule level, the ratio of esophagus/body length, spicules size, presence of pre-cloacal sucker, rod-shaped gubernaculum, and the arrangement of caudal papillae in males. Phylogenetic analyses based on ITS-1, 18S rRNA, and COX1 gene regions were constructed to investigate phylogenetic relationships between this parasite species and other related taxa. Results supported that Cucullanus bulbosus resembles a sister of Cucullanus genypteri, Cucullanus pulcherrimus, Cucullanus bourdini, Cucullanus extraneus, and Cucullanus hainanensis by using different genetic markers. This study provides more information about combining morphological and molecular data to identify Cucullanus species with the first natural occurrence in the common ponyfish inhabited in Saudi Arabia.

Cucullanus carettae Baylis, 1923, in a loggerhead sea turtle (Caretta caretta) from the Adriatic sea: first detection and molecular characterization

Cucullanus carettae Baylis, 1923 (Nematoda: Cucullanidae) is found worldwide in loggerhead turtles (Caretta caretta). Regarding the Mediterranean, C. carettae has been identified in the Tyrrhenian and the Ionian Sea and a unique description of a Cucullanus sp. specimen in loggerheads from the Adriatic Sea has been reported in the literature so far. In the framework of a bio-monitoring project of the Abruzzo and Molise coasts, a parasitological survey was performed on stranded and by-caught sea turtles, at the Istituto Zooprofilattico of Abruzzo and Molise “G. Caporale.” During necropsy, the gastrointestinal system of 72 stranded loggerhead turtles was analyzed for the presence of endoparasites and fecal samples were collected for coprological examination. Adult C. carettae (n = 123) was found in the upper intestine of one loggerhead turtle, associated with chronic lymphoplasmocytic enteritis. Additionally, five stool samples (6.9%) were positive for Cucullanus sp. eggs. Molecular characterization of adult nematodes was carried out to study phylogenetic relationships among the Cucullanus species. To our knowledge, this is the first morphological and molecular identification of C. carettae in loggerhead turtles from the Adriatic Sea. Additional studies on the distribution of this parasite in the Mediterranean are encouraged.

Life Cycle of the Trout Cecal Nematode, Truttaedacnitis truttae (Nematoda: Cucullanidae): Experimental and Field Observations

Truttaedacnitis truttae is a cucullanid nematode of primarily salmonine fishes. Brown trout (Salmo trutta) in Europe reportedly become parasitized by ingesting lampreys (Lampetra planeri) carrying infective larvae. However, our field and laboratory observations suggested that North American specimens of T. truttae have an alternative life cycle. High abundances and potential impact of T. truttae in rainbow trout, Oncorhynchus mykiss, in the Colorado River drainage in Grand Canyon, where there are no lampreys, prompted a study on the transmission dynamics of this nematode. Eggs of T. truttae, collected from live gravid females, were incubated in the laboratory. Snails, Physa gyrina and Lymnaea sp., were exposed to T. truttae larvae 3-4 wk later. Active larvae of T. truttae were observed penetrating the intestinal wall of exposed snails, and worm larvae were found in the visceral tissues when examined 1 wk after exposure. Larvae in snails showed little growth and development 2 wk later and corresponded to L3 larvae. Infected snails were fed to hatchery-reared juvenile rainbow trout. Developing stages were subsequently found in the mucosal lining and lumen of trout intestines. Adult male and female (gravid) worms were found in the ceca of trout examined 5-6 mo after consuming infected snails. Larvae found in pepsin/trypsin digests and mucosal scrapings from wild, naturally infected, trout corroborate laboratory findings. Screening of Physa sp. and gammarids collected from Colorado River, Grand Canyon, for natural infections with T. truttae using the ITS1 rDNA marker gave positive results. Truttaedacnitis truttae is the second species, after Truttaedacnitis clitellarius of lake sturgeon, capable of using a snail first intermediate/paratenic host and is similar to several other cucullanids in having a histotropic phase of development in the definitive fish host.

Life Cycle of the Trout Cecal Nematode, Truttaedacnitis truttae (Nematoda: Cucullanidae): Experimental and Field Observations

Truttaedacnitis truttae is a cucullanid nematode of primarily salmonine fishes. Brown trout (Salmo trutta) in Europe reportedly become parasitized by ingesting lampreys (Lampetra planeri) carrying infective larvae. However, our field and laboratory observations suggested that North American specimens of T. truttae have an alternative life cycle. High abundances and potential impact of T. truttae in rainbow trout, Oncorhynchus mykiss, in the Colorado River drainage in Grand Canyon, where there are no lampreys, prompted a study on the transmission dynamics of this nematode. Eggs of T. truttae, collected from live gravid females, were incubated in the laboratory. Snails, Physa gyrina and Lymnaea sp., were exposed to T. truttae larvae 3-4 wk later. Active larvae of T. truttae were observed penetrating the intestinal wall of exposed snails, and worm larvae were found in the visceral tissues when examined 1 wk after exposure. Larvae in snails showed little growth and development 2 wk later and corresponded to L3 larvae. Infected snails were fed to hatchery-reared juvenile rainbow trout. Developing stages were subsequently found in the mucosal lining and lumen of trout intestines. Adult male and female (gravid) worms were found in the ceca of trout examined 5-6 mo after consuming infected snails. Larvae found in pepsin/trypsin digests and mucosal scrapings from wild, naturally infected, trout corroborate laboratory findings. Screening of Physa sp. and gammarids collected from Colorado River, Grand Canyon, for natural infections with T. truttae using the ITS1 rDNA marker gave positive results. Truttaedacnitis truttae is the second species, after Truttaedacnitis clitellarius of lake sturgeon, capable of using a snail first intermediate/paratenic host and is similar to several other cucullanids in having a histotropic phase of development in the definitive fish host.

Redescription of Dichelyne ( Cucullanellus) Dichelyneformis (Nematoda: Cucullanidae) and Description of a New Congeneric Species in Eleginops maclovinus (Pisces: Eleginopsidae) Collected in the Bay of Corral, Chile

Dichelyne ( Cucullanellus) dichelyneformis ( Szidat, 1950 ) Petter, 1974 , was collected in the intestine of the rock cod, Eleginops maclovinus, in the Bay of Corral, Chile, and redescribed based on light and scanning electron microscopy. The correct arrangement of caudal papillae and post deirids, the shape of gubernaculum, and the morphology and number of denticles surrounding the oral opening are described for the first time. These characteristics along with the excretory pore position, size of spicules, and presence of a nodular thickening near the distal end of the spicules differentiate D. ( C.) dichelyneformis from the other congeners reported in South America and in the Antarctic. The new congeneric species found in E. maclovinus differs from D. ( C.) dichelyneformis based on the larger males, larger and more numerous denticles with a smooth surface, weakly developed sclerotized plates in esophastome, excretory pore and deirids posterior to nerve ring, shorter gubernaculum and spicules with no thickening on their distal region, lower spicules/body length ratio (10.4-15.1%), and a papilla-like phasmids closer to pairs 8 and 10.

Nematode parasites of commercially important fish from the southeast coast of Brazil: Morphological and genetic insight

Studies of nematofauna of teleost fish from the Brazilian coast are relatively scarce and limited to identification based on morphology. The objective of the present study was to determine the diversity and prevalence of nematode parasites in teleost fish from the southeast Atlantic coast of Rio de Janeiro, through morphological, molecular, and ecological approaches. Parasites were collected from sixty specimens each of Genypterus brasiliensis, Micropogonias furnieri, and Mullus argentinae obtained in winters and summers of 2012–2014. Morphological and genetic characterization was conducted using light microscopy and the molecular targets 18S rDNA, ITS1, and mtDNA cox2. Nematodes identified in M. furnieri were Cucculanus genypteri (n = 1575, P = 98.3%) and Hysterothylacium deardorffoverstreetorum (s.l.) (n = 2, P = 3.3%); in G. brasiliensis were Dichelyne (Cucullanellus) sciaenidicola (n = 99, P = 33.3%), Cucculanus pulcherrimus (n = 45, P = 18.3%), Hysterothylacium deardorffoverstreetorum (s.l.) (n = 3, P = 5%), and Anisakis typica (n = 1, P = 1.7%); and, in M. argentinae, were H. deardorffoverstreetorum (s.l.) (n = 146, P = 48.3%), and Procamallanus (Spirocamallanus) halitrophus (n = 4, P = 6.7%). DNA sequence data of C. genypteri, C. pulcherrimus, D. (C.) sciaenidicola, and P. (S.) halitrophus were reported for the first time. New host records are M. argentinae for P. (S.) halitrophus, M. furnieri for A. typica, while H. deardorffoverstreetorum (s.l.) was found in all three fish species. Intestine showed significantly higher intensity than other sites, and no significant seasonal variation in parasitological indices was observed. Hysterothylacium specimens (n = 6) were found in fish muscle, potentially a public health concern.