Contracaecum Species Research Articles

A survey of ecto and endoparasites of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) fingerlings in Midmar reservoir, Adwa, northern Ethiopia

ABSTRACT Fishes are hosts to a range of taxonomically diverse parasites. This survey was intended to provide insight into the occurrence, distribution, prevalence, and intensity of parasites infesting the fingerlings of the tilapia, in Tigray. A total of 384 Oreochromis niloticus specimens were collected from Midmar consisting of 227 males and 157 females. External and internal organs were examined for parasite infection. Squash preparation of fish eyes was also examined to reveal the organisms through microscopic examination. The major groups of parasites were trematode, nematodes, protozoa and hirudinea. A total of 3762 genus Diplostomum were recorded affecting the health of 93% of fishes. Contracaecum species was the second most prevalent distributed majorly in the intestine (77.8%), pericardial cavity (19.1%), swim bladder (2.4%), gill (0.2%) and mouth (0.8%). The prevalence and mean intensity of Diplostomum spp., Contracaecum, Myxosporea, Clinostomum spp., Eustrongylides and Leeches was 93%(10.5), 62.2%(5.3), 39.3%(8.3), 2.1%(8.8),1.8%(5.7) and 1.6% (2.5), respectively. The mean temperature, dissolved oxygen, conductivity, and pH of the dam were 24.4°C, 7.55 mg/l, 849.5µs/cm, and 7.5, respectively. Therefore, responsible bodies in fisheries should perform a pre-stock assessment and provide fish farming extension services for optimum production and marketing of fish products with management and production enhancement methods.

Phylogenetic relationship between Contracaecum spp. (Nematoda, Anisakidae) parasitizing cormorants (Aves, Phalacrocoracidae) in Argentina.

Species of the genus Contracaecum (Family Anisakidae) exhibit a broad host and geographical distribution, parasitizing aquatic organisms such as piscivorous birds and mammals as their definitive hosts. Several Contracaecum species have been reported parasitizing cormorants (Family: Phalacrocoracidae) in South America. The objective of this study was to highlight phylogenetic relationships between Contracaecum species parasitizing cormorants based on both molecular analyses and the papillae arrangement on the male tail. Some Contracaecum species parasitizing Red-legged cormorants from the Ría Deseado (RD), and other nematodes parasitizing eight Neotropic cormorants from San Miguel del Monte lagoon (SMML), Argentina, were collected and analyzed. Both morphological and phylogenetic analyses allowed us to recognize two species: Contracaecum chubutensis parasitizing Phalacrocorax gaimardi, and Contracaecum australe parasitic in Phalacrocorax brasilianus. According to the obtained sequences (mtDNA cox2, ITS1, ITS2, and SSrRNA), Contracaecum sp. parasitizing P. gaimardi exhibited concordance with the previously reported C. chubutensis parasitizing P. atriceps from Bahía Bustamante, Chubut province. Likewise, Contracaecum sp. isolates parasitizing P. brasilianus showed concordance with C. australe from Chile. Besides, the papillae arrangement on the male tail allowed us to understand the interspecific and genetic relationships between the Contracaecum species. The analyses confirm that C. chubutensis specimens parasitizing P. gaimardi from RD present a new host record for the species, whereas, those C. australe specimens parasitizing P. brasilianus from SMML provide a new geographical record for the species and the extension of its distribution range. Present results also confirm the inland and marine distribution of C. australe and C. chubutensis, respectively.

Metazoan parasites of the Ocellated killifish, Floridichthys polyommus (Cyprinodontidae) in La Carbonera coastal lagoon, Yucatán, Mexico

The Ocellated killifish or “bolín yucateco”, Floridichthys polyommus, is an endemic resident of the Yucatan Peninsula, Mexico; it tolerates hypersaline and oligohaline conditions and is considered the dominant species in these ecosystems. In this study, we analyzed 108 individuals of F. polyommus between 2019 and 2013 from La Carbonera coastal lagoon, northern Yucatán Peninsula. We report the taxonomic composition of their metazoan parasite fauna at the infracommunity (individual hosts) and component community (whole sample) levels, estimating parasite community attributes such as species richness, abundance, and diversity. Fish individuals were measured, dissected, and examined for ecto and endoparasites. Metazoan parasites were identified using morphological and molecular data. Sixteen parasite taxa were found, including six digeneans, three nematodes, and one of the following: cestode, acanthocephalan, copepod, isopod, argulid, hirudinean, and pentastomid. Ten of them were found as larval stages. The prevalence and mean intensity of infection were calculated for each parasite taxon. The cestode Glossocercus caribaensis was the most prevalent taxon, whereas the digenean Ascocotyle sp.1 was the most abundant. For ecological analyses, three species of Contracaecum were lumped together. The species richness and diversity of the component community were 14 and 0.049, respectively, whereas at the infracommunity level, both parameters were 1.9 ± 1.27 and 0.147 ± 0.225. The parasite species richness values in F. polyommus at both levels were higher than those previously reported in other species of Cyprinodontidae. We discuss that the parasite community of F. polyommus reflect its importance in energy transport in coastal lagoons of the Yucatán Peninsula.

The genus Contracaecum Raillet & Henry (Nematoda: Anisakidae): host and geographical distribution on Neotropical and Antarctic species

Nematodes of the genus Contracaecum Raillet & Henry, 1912 (Anisakidae, Contracaecinae) have a worldwide distribution. The taxonomy of the genus Contracaecum is well-known nowadays due to several morphometric studies, scanning electron microscopy, and molecular biology. The aim of this work was to review, clarify, and summarize the valid species of the genus Contracaecum parasitizing piscivorous sea birds and mammals from both the Neotropical and Antarctic regions reviewing all scientific available papers and electronic searching data up to date. A checklist on Neotropical and Antarctic Contracaecum spp. was organized through a revision of scientific papers and original descriptions. The systematic online search and the most updated papers were obtained through SCOPUS, Google Scholar, PubMed, Medline, World Register of Marine Species, etc. We provide information about hosts, Neotropical and Antarctic localities where worms were collected, references, molecular markers, and Genbank accession numbers. Twenty-five Neotropical and Antarctic Contracaecum species have been recorded up to date and checked out as valid ones according to the most updated data. Twenty-one species parasitize exclusively fish-eating birds, two species were reported only on marine mammals, and the other two parasitize both sea birds and mammals. A total of 20 Contracaecum species are exclusively reported for the Neotropical region, three only for Antarctic hosts, and two species were reported parasitizing both Neotropical and Antarctic hosts. Several Contracaecum species (10) have been corroborated by molecular analysis of different genetic markers. After reviewing all morphological descriptions of the Contracaecum species, and despite most of them have been characterized only by morphometric methods, we are convinced that all species listed in this work correspond to good and valid Contracaecum Neotropical and Antarctic species. Present results indicate that more taxonomic and molecular studies are needed to advance the understanding of the distribution and host specificity of the Contracaecum species.

Advancing understanding of the taxonomy and diversity of the genus Contracaecum in the great white pelican (Pelecanus onocrotalus).

Despite the wide distribution and health importance of anisakids of the genus Contracaecum, epidemiological data on their occurrence in definitive bird hosts are scarce, particularly from certain parts of the world that represent important wintering sites or migration stopovers for different bird species. In the present study, Contracaecum spp. infecting six great white pelicans (Pelecanus onocrotalus) in Israel were identified using light and scanning electron microscopy and phylogenetic analyses of nuclear internal transcribed spacer (ITS) and mitochondrial cytochrome c oxidase II (cox2). A PCR-RFLP method was also developed and applied to screen large numbers of Contracaecum parasites. Most (415/455) worms recovered were C. micropapillatum, followed by C. gibsoni (31/455), C. quadripapillatum (8/455), and C. multipapillatum E (1/455). Contracaecum micropapillatum from Israel and C. bancrofti from Australia are distinguishable by cox2 but less well resolved with ITS sequences, and could not be distinguished morphologically. Worms with cox2 matching C. gibsoni had ITS matching specimens identified as C. multipapillatum A. To the authors' knowledge, this represents the first of such studies in Israel and provides useful data on the ecology and distribution of different Contracaecum species of health and economic interest.

Complete Mitochondrial Genome of Contracaecum sp. (Nematoda: Ascarididae) from night herons in China

Contracaecum species are zooparasitic anisakid nematodes and occur in gastrointestinal tracts of vertebrate/invertebrate animals, including humans, causing gastrointestinal pain, diarrhea, and increasingly severe vomiting. Although the complete mitochondrial (mt) genome (mitogenome) of Contracaecum sp. isolated from night herons in Beijing has been reported, the detailed information about this mt sequence is still puzzling. In the present study, we described the detailed characteristics across the complete mt DNA of Contracaecum sp., which includes 36 genes consisting of 12 protein genes, 22 transfer RNAs (tRNAs), 2 ribosomal RNAs (rRNAs), and 2 noncoding regions (NCRs), and all genes have the same orientation of transcription. The AT content in the complete mitogenome of Contracaecum sp. was 72.2%, and it was the least value (66.7%) in the cox1 gene but was the highest rate (84.1%) in NCRs. The highest nucleotide diversity (Pi) among the genus Contracaecum was nad4 (0.190) and the least was cox1 (0.125), which indicates that nad4 might have the potential ability as useful markers to detect cryptic species in the genus Contracaecum or subspecies. Based on the maximum likelihood (ML) and Bayesian inference (BI) computational algorithms within subfamilies Ascaridoidea and Heterakoidea, the results supported that Contracaecum sp. was a new species and the family Ascaridiidae was paraphyletic. The complete mitogenome sequence of Contracaecum sp. supported a clear recognition of Contracaecum species and provided the potential existence of cryptic species in the genus Contracaecum. Our findings would better contribute to the surveillance, molecular epidemiology, and control of Contracaecum.

Morphological description and molecular characterization of Contracaecum larvae (Nematoda: Anisakidae) parasitizing market-size hybrid tilapia (Oreochromis aureus x Oreochromis niloticus) and red drum (Sciaenops ocellatus) farmed in Israel

Nematodes belonging to the genus Contracaecum (family: Anisakidae) are heteroxenous parasites with a complex life cycle. Contracaecum larvae infecting farmed fish and fishery products are economically important causing market rejection in massive infection and may have zoonotic potential. In Israel, Contracaecum larvae have been described morphologically in several fish species; however, none of these descriptions were supported by molecular tools. In 2019–2020, hybrid tilapia (Oreochromis aureus x Oreochromis niloticus) and red drum (Sciaenops ocellatus), farmed in polyculture were found to be heavily infected with nematodes referable to Contracaecum larvae. Prevalence of infection in hybrid tilapia and red drum was 53.8% and 40.9%, respectively. A combined (morphological and molecular) approach revealed that both infected fish species were parasitized by the same species of Contracaecum, although larvae in hybrid tilapia were localized in the pericardial cavity whereas in red drum, they were observed in the abdominal cavity. Genetic analysis of internal transcribed spacer rDNA and cox2 mtDNA showed high similarity to unidentified Contracaecum larvae detected in several fish species in Ethiopia, Egypt and Kenya. In this study, molecular and morphological analyses place the possible new species in the C. multipapillatum complex and was provisionally named C. multipapillatum E. Further analyses combining morphological and molecular approaches are required on adult specimens collected from piscivorous birds living in the same area to support the identification of a potentially new species.

Checklist of Fish Hosts of Species of Contracaecum Railliet & Henry, 1912 (Nematoda: Ascaridida: Anisakidae) in Iraq

Surveying literature concerning the occurrence of the nematode larval forms of the genus Contracaecum in fishes of Iraq, showed the infection of 44 freshwater and marine fish species in Iraq with such larvae. The infection included larvae of unidentified Contracaecum species, Contracaecum rudolphii type-B and Contracaecum septentrionale Kreis, 1955. The infections were distributed in Tigris, Euphrates and Shatt Al-Arab rivers as well as some of their tributaries, lakes, marshes, drainage networks in addition to many fish ponds and floating cages in different parts of Iraq. This checklist also provided references on some histopathological and biochemical changes, some ecological aspects of the infection, life cycle and scanning electron microscopy. In addition, this checklist includes literature on six species of adult Contracaecum species as well some unidentified species of this genus from 17 bird species from different parts of Iraq, of which both Eurasian bittern Botaurus stellaris and pygmy cormorant Microcarbo pygmaeus were infected with a maximum number of three Contracaecum species as well as unidentified species of this genus.

Identification and genetic characterization of Contracaecum sp. (Nematoda: Anisakidae) from China.

Contracaecum species are economically important fish-borne larval nematodes with zoonotic significance. In June 2019, more than 100 piscivorous birds died in their habitats close to the Wild Duck Lake, located in Yanqing, northwest of Beijing, China. Post-mortem examination of Black Night Herons (Nycticorax) revealed the presence of numerous anisakid nematodes in the proventriculus. Recovered nematodes were identified as Contracaecum sp. based on morphological description. Phylogenetic analysis of the mitochondrial (mt) genome and the ITS gene showed that sequences of Contracaecum sp. Beijing isolates were grouped into a new individual cluster. Furthermore, the parasite was successfully isolated from fresh dead birds, feces of piscivorous birds, and fish and prevalence ranged from 8.0% to 81.8%. Consequently, our study demonstrated Contracaecum sp. infections in different sources from China, which might constitute a threat to wildlife, aquaculture, and public health.

New insights into the coexistence of Contracaecum rudolphii A and Contracaecum rudolphii B (Nematoda: Anisakidae) in Phalacrocorax carbo sinensis from Sardinia: genetic variability and phylogenetic analysis.

Contracaecum sp. nematodes are important parasites of fish eating birds that can cause animal health problems. In the present study, specimens of Contracaecum rudolphii sensu lato, from the great cormorant Phalacrocorax carbo sinensis from Sardinia, were characterized based on morphological and molecular data. The morphological analysis allowed to identify all the fourth stage larvae (n = 1918) as Contracaecum sp., and adults, male (n = 5845) and female (n = 8312), as C. rudolphii sensu lato. Population genetics and phylogenetic relationships were inferred based on mitochondrial and nuclear markers. Multiple sequence alignment of the ribosomal internal transcribed spacer showed the coexistence of C. rudolphii A (n = 157), C. rudolphii B (n = 22) and a rare heterozygote of these species. Moreover, mitochondrial markers, namely NADH dehydrogenase subunits I (nad1), cytochrome c oxidase subunit (cox1 and cox2) and small subunit of rRNA (rrnS), showed that the studied C. rudolphii A populations had undergone bottleneck, or founder effect event, subsequent to a rapid population growth and expansion. The observed heterozygote is with a mitochondrial pattern of C. rudolphii B. Although, both Contracaecum species showed high genetic diversity, no genetic structure between localities was detected. Phylogenetic reconstructions supported the paraphyly of the avian Contracaecum species including C. ogmorhini (parasite of otariids).

Species of Contracaecum Parasitizing the Magellanic Penguin Spheniscus Magellanicus (Spheniscidae) from the Argentinean Coast

Anisakid nematodes have a worldwide distribution and are associated with fishes, birds, and marine mammals from freshwater, brackish, and marine systems. The aims of this work are to report for the first time Contracaecum mirounga parasitizing the Magellanic penguin Spheniscus magellanicus, to report another Contracaecum species in the same host species, and to discuss the validity of Contracaeceum spheniscus. Several dead chicks, juveniles, and adults of S. magellanicus were collected along the Argentinean coast from 2002 to 2009. Nematodes were removed from digestive tracts and studied using both light and scanning electron microscopy. Nematode prevalences were 2.38% for C. mirounga and 12.5% for Contracaecum sp. Contracaecum mirounga was found in 1 penguin from Península Valdés, Chubut. This species is known as a specific parasite of marine mammals such as Pinnipedia, thereby suggesting that this nematode is not as specific as believed. Another species of Contracaecum sp. was found parasitizing 1 penguin from the Río de la Plata coast. It possessed an unusual interlabial morphology and arrangement of male caudal papillae. Despite the low prevalence, the distinct morphological features are convincing and support the presence of a new Contracaecum species. However, a formal description is not presented because sufficient male specimens are lacking. Finally, C. spheniscus is considered a junior synonym of Contracaecum pelagicum. Future molecular studies might be helpful to determine the real diversity of Contracaecum species parasitizing S. magellanicus considering the number of sibling species recognized among the anisakids.

On the occurrence and molecular identification of Contracaecum larvae (Nematoda: Anisakidae) in Mugil cephalus from Turkish waters.

Anisakis and Contracaecum species are fish borne zoonotic nematodes. In our previous studies, other larval anisakid and raphidascarid nematodes, Anisakis and Hysterothylacium species, were genetically identified in marine fish from Turkish waters. However, there is no information on molecular identification of larval Contracaecum species in marine fish from Turkey. Therefore, the aim of this study was only to investigate the presence and molecular identification of Contracaecum species in commonly commercialized marine fish from Turkish waters. A total of 475 marine fish, which belong to 21 different species, were sampled from the Aegean (FAO 37.3.1), Mediterranean (FAO 37.3.2), and Black Sea (FAO 37.4.2). The prevalence of Contracaecum L3 larvae in the Aegean Sea was identified as 10% in Mugil cephalus. All Contracaecum L3 larvae were molecularly characterized with RFLP targeting the ITS region and rrnS gene. Moreover, all larvae were analyzed by sequencing of ITS region, rrnS and cox2 gene. All Contracaecum larvae were identified as C. overstreeti based on the cox2 sequence analysis. This is the first report of C. overstreeti larvae in M. cephalus as paratenic and intermediate hosts. Furthermore, the analysis reveals novel information on ITS region. Additionally, the rrnS gene of C. overstreeti was also achieved and deposited in Genbank for the first time. The PCR-RFLP patterns of the ITS region and rrnS gene from C. overstreeti were presented in the present study. Consequently, the presence of C. overstreeti larvae in M. cephalus from the Aegean Sea may alsopotentially capable of inducing allergic sensitization in humans.

Observations on the health of Tandanus tropicanus (Teleostei: Plotosidae) from an Australian river system

Wild Wet Tropics tandan Tandanus tropicanus were collected from the Bloomfield River, Queensland, for examination by histopathology and bacteriology. This provided an opportunity to establish baseline information on the general health and parasite fauna of native freshwater catfish in a pristine river. Histology of gill tissue revealed epitheliocystis in one fish. This is the first report of epitheliocystis in T. tropicanus. Bacterial culture showed light growth of bacteria from the kidney of only two fish, and these were identified as Aeromonas veronii, A. jandaei and Bacillus/Lactobacillus spp. An unidentified monogenean infection was observed in the gills of four fish, and trematode metacercariae were observed in the extra-ocular tissue of four fish. Nematodes were observed in the tissues of nine fish, and sequence and preliminary phylogenetic analysis of PCR products using an ITS primer suggest that these parasites may be a previously unreported Contracaecum species.

A Study of Clinostomum (Trematode) and Contracaecum (Nematode) Parasites Affecting Oreochromis Niloticus in Small Abaya Lake, Silite Zone, Ethiopia

This study was conducted at Lake Small Abaya Ethiopia, to identify Clinostomum and Contracaecum parasites from a total of 384 O. niloticus species sampled during November 2013- April 2014. Of the 384 samples collected, 138 (35.9%) were infested with nematode of Contracaecum species and 72 (18.8%) were infected with trematode of Clinostomum species. The intensity of infestation by Contracaecum and Clinostomum was 1-19 worms per fish (mean intensity=4.47) and 1-12 worms per fish (mean intensity=3.56) respectively. There was no significant difference (p>0.05) in the prevalence of infestation among host sex, host size and host weight. There was no any statistically significant (p>0.05) correlation between the number of Clinostomum, Contracaecum and the mixed number of parasites and the fish’s condition. In conclusion, the study show that fish parasite are prevalent in Small Abaya lake .Hence, further studies and appropriate control measure are recommended to reduce their effect on the fishery industry and public health.

Coevolution between Contracaecum (Nematoda, Anisakidae) and Austrolebias (Cyprinodontiformes, Rivulidae) host-parasite complex from SW Atlantic coastal basins.

In recent years, molecular studies in host-parasite interactions in terms of coevolution have become important. Larvae (L3) of two species of Contracaecum were found parasitizing species of Rivulidae in the Atlantic coastal basins from Uruguay. The aim of this study is to determine the patterns of differentiation of this host-parasite complex in order to clarify possible coevolutionary events in such interaction throughout phylogeographic approach using both nuclear and mitochondrial molecular markers (internal transcribed spacers (ITS) and cytochrome oxidase subunit 1 (cox-1)). Based on both markers, intraspecific variation in Contracaecum species was lower than 2 %, while interspecific variation was greater than 10 %. Both species of Contracaecum constitute monophyletic groups. Contracaecum resulted in a paraphyletic genus when incorporating other Contracaecum species and closely related nematode sequences from GenBank. ITS regions showed that Contracaecum sp. 1 is more closely related to other species of the same genus than with their counterparts from Atlantic coastal basins in Uruguay. Haplotype network for both markers corroborate the existence of two distinct taxa. While ITS pairwise FST comparisons and the indirect estimate of gene flow confirm the existence of two distinct Contracaecum species, mitochondrial gene detected low levels of migrants between some of the populations from both species. Our results suggest that coevolution in this host-parasite complex species is plausible. Parasite cladogenetic events occur almost simultaneously with the separation of the hypothetical ancestors of each species complex of Austrolebias during Pliocene. Additionally, the two lineages of Contracaecum colonize differently the species within each of the Austrolebias complexes.

Helminth parasites of Synodontis nigrita at lower Niger (IDAH), Nigeria

The isolation and identification of helminth parasites of Synodontis nigrita and length–weight relationship of the fish in the lower Niger (Idah), Kogi State, Nigeria were carried out in order to describe the pattern of occurrence of the helminth and to establish the well-being of the host fish. A total of 102 randomly sampled fish were studied and three genera of helminths were recovered; 39.1, 48.7 and 12.2% respectively, and were harboured in the fish’ intestine. The three genera of helminths isolates identified include two nematodes ( Capillaria and Contracaecum species), Acanthocephala ( Acanthocephalus species) and Trematode ( Posthodiplostomum spp.). Of the 102 fish studied, 16 were infected with 80 helminth parasite giving a prevalence rate of 15.7%. The overall mean intensity and mean abundance of helminth parasite occurrence for the sampled fish were 13.6 and 1.5, respectively. The mean standard length of the fish was 7.45 ± 2.59 cm. The need for fish seeds from the wild to be examined for the helminth parasites during culture practice and the socio-economic and human health implications of eating infected fish is also recommended. Key words : Acanthocephala, nematode, isolation, trematode, intestine.

Anisakid Nematodes of Greenland HalibutReinhardtius hippoglossoidesfrom the Barents Sea

Parasitic nematodes from the body cavity of 94 Greenland halibut (Reinhardtius hippoglossoides) caught in the Barents Sea were examined. Nematode species were identified using both morphological and molecular methods. Four morphospecies were found: Anisakis simplex s.l., Contracaecum osculatum s.l., Pseudoterranova decipiens s.l., and Hysterothylacium aduncum. The most prevalent were C. osculatum s.l. (89.4%) and A. simplex s.l. (86.2%). Mean intensities for these 2 species were 7.8 and 45.2, respectively. The number of parasites was directly proportional to the fish length. The following 6 parasite species, including 3 cryptic species of Contracaecum sp., were identified using molecular methods: A. simplex sensu stricto, C. osculatum A, C. osculatum B and C (the last 2 as host records for halibut), Pseudoterranova bulbosa, and H. aduncum. Mixed infections of C. osculatum A, B, and C were observed.

Sequence variation in four mitochondrial genes among sibling species within Contracaecum rudolphii sensu lato

The present study investigated sequence variability in four mitochondrial DNA (mtDNA) regions, namely cytochrome c oxidase subunit (cox1), NADH dehydrogenase subunits 1 and 4 (nad1 and nad4), and small subunit of rRNA (rrnS), among Contracaecum rudolphii A, C. rudolphii B, C. rudolphii C and Contracaecum septentrionale from different hosts and geographical origins in China, Italy, Spain and the USA. Regions in the cox1, nad1, nad4 and rrnS genes (designated pcox1, pnad1, pnad4 and prrnS, respectively) were amplified separately from individual nematodes by PCR, sequenced and compared to estimate sequence variability. While sequence variation within each of the Contracaecum species was 0–2.6% for pcox1, 0.3–2.5% for pnad1, 0–1.9% for pnad4 and 0–2.9% for prrnS, differences between species was significantly higher, being 3.3–12%, 9.8–15.2%, 9.6–18.3% and 3.5–11.12% for these regions, respectively. Phylogenetic analyses of pcox1, pnad1, pnad4 and prrnS sequence data using maximum likelihood (ML), maximum parsimony (MP) and neighbour joining (NJ) showed that the specimens of each Contracaecum species clustered together. These results provide additional genetic evidence for the existence of sibling species within C. rudolphii sensu lato.

Anisakid larvae in the liver of cod (Gadus morhua) L. from the southern Baltic Sea

In the present investigation a sample of 490 cod (Gadus morhua) was examined from three regions in the southern Baltic Sea (the Polish Exclusive Economic Zone, EEZ). Three species of anisakid nematodes with zoonotic potential, namely species of Contracaecum, Anisakis and Pseudoterranova, were found in the liver of cod, with Contracaecum being the most dominant species. The prevalence of infection was highest in the Western Baltic (22.5%) compared to the Central Baltic (10.4%) and the Gulf of Gdansk (3.4%). Generalized linear models (GLMs) were applied to analyse the prevalence of infection with Anisakis sp. and Contracaecum sp. relative to biological and spatial parameters. The effect of the sampling region, age and body length of the fish were significant in both GLMs. The effect of region was higher in the Western Baltic than in other regions. The prevalence of infection was correlated with the length of the fish and was higher in adult compared with sub-adult fish. These results suggest that the prevalence of infection with anisakid nematodes (especially Contracaecum sp.) in cod sampled in Polish waters of the Baltic Sea has significantly increased compared with previous studies undertaken over the past few decades.

First report of human anisakidosis in Australia

We present the first human case of anisakidosis acquired from eating locally caught fish in Australia. A 41-year-old woman experienced gastrointestinal pain, vomiting and diarrhoea of increasing severity over 3 weeks. All symptoms resolved spontaneously after a worm was passed in her faeces. Microscopic examination showed that it was a Contracaecum species larva of the family Anisakidae. Anisakidosis should be considered in patients with gastrointestinal symptoms who have recently eaten seafood.