Cylindrospermopsis raciborskii (Woloszynska) is a photosynthetic cyanobacterium that can produce cytotoxic (cylindrospermopsin) and neurotoxic cyanotoxins (saxitoxins). In Brazil the strains of C. raciborskii are reported to produce only saxitoxins (STX) and their effect on fish parasites has not been tested to date. The fish Poecilia vivipara Bloch and Schneider is a common host for the trematode Pygidiopsis macrostomum Travassos off the coast of Rio de Janeiro, and this fish–parasite interaction is a model for behavioural and ecotoxicological studies. The aim of this work was to evaluate the motility of metacercariae of P. macrostomum from P. vivipara exposed to 40 mg l−1 and 400 mg l−1 of crude lyophilized extract of the cyanobacterium C. raciborskii (CYRF-01) for 48 h. The fish were separated into groups of ten individuals and, after exposure, five fish from each group were dissected for counting and checking the motility of metacercariae. The other five fish were dissected after 48 h in clean water. The detection and quantification of STX in the solutions of cyanobacteria, and the gills and guts of fish, were performed by an enzyme-linked immunosorbent assay. The crude extract of C. raciborskii caused temporary paralysis in metacercariae of P. macrostomum after exposure of fish to both concentrations, and the motility recovered after the fish were kept for 48 h in clean water. STX was detected in the guts and gills of all fish analysed, suggesting that this toxin is involved in the paralysis of metacercariae. This is the first report on the action of neurotoxins in metacercariae of fish.

Since dirofilariosis caused by Dirofilaria immitis is a vector-borne disease, its distribution depends on environmental conditions as well as demographic factors and the management of pets by humans. In the province of Salamanca (west-central Spain) the disease has been known for many years, appearing in an area with extensive irrigated crops along the Tormes river. Because recent demographic changes have occurred in this area, the present study has been carried out with the aim of monitoring the distribution and prevalence of the disease in the canine population of this area. For that purpose, 191 dogs were analysed through antigen and microfilaria tests and geo-referenced in a map. The overall prevalence was 5.8%, although the disease was only present in dogs from municipalities with irrigated crops in which the prevalence was 16.7%. These results indicate that D. immitis continues to be present in the province of Salamanca, and that it is associated with the presence of irrigation, but with a clear decrease in the prevalence. Causes of the decrease in prevalence, as well as the potential zoonotic risk, are discussed.

We describe Monorchis lewisi n. sp. (Monorchiidae) from the surf bream, Acanthopagrus australis (Günther, 1859) (Sparidae), in Moreton Bay, eastern Australia. The new species differs from most existing species of Monorchis Monticelli, 1893 in its possession of an elongate I-shaped excretory vesicle, and from other congeners in the relative configuration of the gut and suckers. Ovipusillus mayu Dove & Cribb, 1998 is re-reported from Gnathanodon speciosus (Forsskål, 1775) (Carangidae) from Moreton Bay. We report new second internal transcribed spacer (ITS2) and 28S rDNA sequence data for both species. Bayesian inference and Maximum Likelihood analyses of the 28S rDNA dataset suggest that existing subfamily and genus concepts within the family require substantial revision.

Cystidicoloides vaucheri collected in the stomach of the redtail catfish Phractocephalus hemioliopterus from River Acre, State of Acre, Brazil is redescribed, including the first description of males and the first genetic characterization based upon 18S and 28S genes of the rRNA. Newly collected females were biometrically smaller than those reported in the original description, but similar morphology shared by the two samples revealed that they belong to the same species. Scanning electron micrographs showed the accurate structure of the cephalic region, described here in detail. Furthermore, the morphology of males completed the specific diagnosis, strengthening the validity of the species. The three other congeners differ from C. vaucheri mainly as follows: in C. dlouhyi the area rugosa is absent, the cephalic structures in C. fischeri are completely distinct, and in both species the spicules have membranous outgrowths, absent in C. vaucheri. Despite the dubious generic assignment of C. izecksohni, it differs from C. vaucheri in several biometrical and morphological features. Because of data availability, only sequences of the 18S were used for phylogenetic reconstructions. Results showed that the genus Ascarophis and the families Cystidicolidae and Physalopteridae are not monophyletic. Cystidicoloides vaucheri formed an independent branch clustering with representatives of Cystidicolidae, confirming its validity. The inclusion of Salmonema and Spinitectus within Cystidicolidae should be reviewed, since they formed an assemblage with species from Rhabdochonidae. In fact, current classification of some taxa belonging to Habronematoidea, Physalopteroidea and Thelazioidea need to be re-evaluated, mainly based on molecular data from different genes.

A new nematode species, Philometroides acreanensis n. sp. (Philometridae), is described from female specimens recovered from the stomach wall of the freshwater catfish Pimelodus blochii Valenciennes (Pimelodidae) collected in the Acre River (Amazon River basin), Acre State, Brazil. Based on examination by light and scanning electron microscopy, the new species differs from the two other South American congeneric species mainly in the body length of the gravid female (240–280 mm), the length of the oesophagus (1.25 mm in holotype) representing 0.5% of the entire body length, the range of cuticular embossment, as well as the location in the host (stomach), order of the fish host (Siluriformes) and the geographical distribution (Amazon River drainage system). This is the third known species of Philometroides Yamaguti, 1935 reported from South America. A key to species of Philometroides occurring in the fish of America is provided.

Angiostrongylus mackerrasae is a parasitic nematode of rats found in Australia. When first reported, it was referred to as A. cantonensis. Recent molecular studies, including the mitochondrial genome, indicate that it is highly similar to A. cantonensis. These studies did not include A. malaysiensis, another member of the A. cantonensis species complex, for comparison. The present study examined the genetic distance and phylogenetic relationship between the component taxa (A. cantonensis, A. mackerrasae and A. malaysiensis) of the A. cantonensis species complex, based on the 12 protein-coding genes (PCGs) of their mitochondrial genome. Both the nucleotide and amino acid sequences were analysed. Angiostrongylus mackerrasae and A. cantonensis are members of the same genetic lineage and both are genetically distinct from A. malaysiensis. The genetic distance based on concatenated nucleotide sequences of 12 mt-PCGs between A. mackerrasae and A. cantonensis from Thailand is p = 1.73%, while that between the Thai and Chinese taxa of A. cantonensis is p = 3.52%; the genetic distance between A. mackerrasae and A. cantonensis from China is p = 3.70%. The results indicate that A. mackerrasae and A. cantonensis belong to the same genetic lineage, and that A. mackerrasae may be conspecific with A. cantonensis. It remains to be resolved whether A. mackerrasae is conspecific with A. cantonensis or undergoing incipient speciation.

Gnathostoma turgidum is a nematode parasite that exploits the stomach of Virginian opossums, Didelphis virginiana, in Latin America. The opossum is the definitive host of G. turgidum in the wild. Intrahepatic growth and maturation of the parasite, subsequent migration to the stomach and spontaneous expulsion are common. However, the histopathological lesions caused by G. turgidum are poorly described. A better understanding of the life cycle of this parasite and the pathological changes in natural host–parasite interactions could help to clarify the progression of human infections caused by Gnathostoma binucleatum. The aim of this work was to study morphological changes in the liver and stomach of D. virginiana during natural infection and adult worm expulsion. Three opossums naturally infected with G. turgidum were captured from an endemic area of gnathostomosis. Three uninfected opossums captured from a non-endemic area were used as controls. The opossums were sacrificed at different stages of infection (March, May and December), and a histopathological study of their livers and stomachs was conducted. Injuries in livers were observed by histopathology – areas of necrosis and collagen septa were identified. Parasites caused nodules with necrosis on the periphery of lesions, and collagen fibres were also observed in stomachs. Collagen septa may be caused by antigenic remains of the parasite. Further immunological studies are necessary to verify that stimulation is caused by these factors.

We analysed the association between a monogenean (Udonella cf. caligorum Johnston 1835) and its copepod host (Caligus sp.) living on a wild population of Arius herzbergii Bloch, 1794 in a north-eastern coastal lagoon from Venezuela. This study characterized infestation levels and analysed the effects of monogeneans on the fecundity and hatching success of the copepod host, as well as damage to its egg capsules and genital complex. A total of 218 Caligus specimens were analysed (94 males, 110 females and 14 immature stages) in which a total of 1017 monogeneans were found. These included 311 mature stages and 706 egg capsules. Monogenean stages were found attached to the cephalothorax, abdomen, genital complex and egg capsules of the copepods. No significant differences were found in fecundity and egg hatching when infested and non-infested ovigerous females were compared. No damage was observed on egg capsules or genital areas of infested ovigerous females. Our results suggest that this association, at the level of prevalence and intensity observed, is closer to commensalism than parasitism. The importance of considering that the nature of interaction is dynamic and changing with environmental conditions and time scale is highlighted.

Hysterothylacium species are perhaps the most abundant and diverse group of marine ascaridoids; however, their life cycle and specific identification in larval stages in many parts of the world, particularly in Iraqi marine waters, have not been completely understood. In this study three members of the genus Hysterothylacium collected from Khor Abdulla in Iraq are morphologically described, genetically characterized and their relationship with other closely related taxa are compared and discussed. A new Hysterothylacium larval type in the fourth stage of development is described, and morphological and molecular evidence (based on the sequences of internal transcribed spacers) are provided for its distinction from previously known fourth-stage Hysterothylacium larval types. Based on the sequence data it is suggested that the new larval type, which herein was assigned as Hysterothylacium larval type XVI, is H. persicum which was previously reported from the close proximity in Bandar Abbas, Iran. In addition, two other taxa, including Hysterothylacium larval type XV and H. reliquens, have been found in the present study, for which new hosts are reported. This study provides some insights into the taxonomy and systematics of these parasites, not only in this region but also for similar studies elsewhere.

The rat lungworm Angiostrongylus malaysiensis is a metastrongyloid nematode parasite. It has been reported in Malaysia, Thailand, Laos, Myanmar, Indonesia and Japan. In this study, A. malaysiensis adult worms recovered from the lungs of wild rats in different geographical regions/provinces in Thailand were used to determine their haplotype by means of the mitochondrial partial cytochrome c oxidase subunit I (COI) gene sequence. The results revealed high COI haplotype diversity of A. malaysiensis from Thailand. The geographical isolates of A. malaysiensis from Thailand and other countries formed a monophyletic clade distinct from the closely related A. cantonensis. In the present study, five new haplotypes were identified in addition to the four haplotypes reported in the literature. Phylogenetic analysis revealed that four of these five new haplotypes – one from Mae Hong Song (northern region), two from Tak (western region) and one from Phang Nga (southern region) – formed a distinct clade with those from Phatthalung (southern region) and Malaysia. The haplotype from Malaysia was identical to that of Phatthalung (haplotype AM1). In general, the COI sequences did not differentiate unambiguously the various geographical isolates of A. malaysiensis. This study has confirmed the presence of high COI genetic diversity in various geographical isolates of A. malaysiensis. The COI gene sequence will be suitable for studying genetic diversity, population structure and phylogeography.

Filariasis is very common in tropical countries. It is endemic in the coastal areas of India. We report four cases of haematological malignancy where peripheral blood and bone marrow smears did not show any microfilariae but conventional cytogenetic preparations from all the four cases showed the presence of parasites. Their morphology confirmed the diagnosis of all cases as bancroftian filariasis. Therefore all types of cytogenetic preparations should be screened carefully in the endemic areas along the coastal zones of India for the presence of this parasite.