Acanthocephalans belonging to the species Neoechinorhynchus agilis were collected from two mullets, Mugil cephalus and Chelon ramada from Ichkeul Lagoon in northern Tunisia. Collected parasites, as well as tissues of their hosts (muscle, liver and intestine), were analysed for trace elements (silver, arsenic, cadmium, cobalt, copper, iron, manganese, nickel (Ni), lead (Pb), selenium, vanadium (V), zinc) using inductively coupled plasma mass spectrometry. Our results showed different accumulation patterns of trace elements in fish tissues and parasites. Among the host tissues, liver accumulated the highest metal amounts. Acanthocephalans showed Ni, Pb and V in significantly higher concentrations compared to their host's tissues. Further, the calculated bioconcentration factors demonstrated a 390-fold higher Pb accumulation in the parasite compared to fish muscle. This study is the first field survey in Tunisia dealing with elements’ uptake in parasites and their hosts. Our results corroborate the usefulness of the acanthocephalans for biomonitoring of metal pollution in aquatic ecosystems and promote more research in order to understand host–parasite systems in brackish waters of the Mediterranean area.

The use of native entomopathogenic nematodes as biocontrol agents is a strategy to decrease the environmental impact of insecticides and achieve sustainable agriculture crops. In this study, the effect of the surface culture of Steinernema sp. JAP1 over two solid media at 23–27°C on infective juvenile (IJ) production and pathogenicity against Galleria mellonella larvae were investigated. First, the bacterial lawn on the surface of the media with egg yolk (P2) or chicken liver (Cl) were incubated in darkness at 30°C for 48 and 72 h, and 100 surface-sterilized IJs were added. Four harvests were conducted within the next 35 days and the mean accumulated production was superior on Cl (210 × 103 IJs) than on P2 (135 × 103 IJs), but the productivity decreased up to 10% when the incubation time of the bacterial lawn was of 72 h. The mean pathogenicity of in vitro- and in vivo-produced IJs were of 47–64% and 31%, respectively. It is worth noting that none of the two solid media had a statistically significant difference in IJ pathogenicity. Considering that the maximum multiplication factor of IJs on solid media was 2108 and that the pathogenicity against G. mellonella was outstanding, Steinernema sp. has a good potential for in vitro mass production.

The round goby (Neogobius melanostomus) is a successful invader of the Great Lakes–St Lawrence River basin that harbours a number of local parasites. The most common are metacercariae of the genus Diplostomum. Species of Diplostomum are morphologically difficult to distinguish but can be separated using molecular techniques. While a few species have been sequenced from invasive round gobies in this study system, their relative abundance has not been documented. The purpose of this study was to determine the species composition of Diplostomum spp. and their relative abundance in round gobies in the St Lawrence River by sequencing the barcode region of cytochrome c oxidase I. In 2007–2011, Diplostomum huronense (=Diplostomum sp. 1) was the most common, followed in order by Diplostomum indistinctum (=Diplostomum sp. 4) and Diplostomum indistinctum sensu Galazzo, Dayanandan, Marcogliese & McLaughlin (2002). In 2012, the most common species infecting the round goby in the St Lawrence River was D. huronense, followed by D. indistinctum and Diplostomum gavium (=Diplostomum sp. 3). The invasion of the round goby in the St Lawrence River was followed by a decline of Diplostomum spp. in native fishes to low levels, leading to the previously published hypothesis that the presence of the round goby has led to a dilution effect. Herein, it is suggested that despite the low infection levels in the round goby, infections still may lead to spillback, helping to maintain Diplostomum spp. in native fishes, albeit at low levels.

The present report describes two cases of infection by Molossinema wimsatti in the brain of Pallas's mastiff bats (Molossus molossus). The first bat was captured and killed by a domestic cat in a suburban area of the municipality of Patos, Paraiba, northeastern Brazil. The second bat was found crawling on the ground in the same area before dying. No gross lesions were found at necropsy. Histology of the central nervous system revealed filarioid nematodes in the brain ventricles and cerebellum. There were adults, subadults and eggs, the latter sometimes containing microfilariae. No inflammatory response was observed in bat 1, while bat 2 presented a mild lymphoplasmacytic meningoencephalitis. Three nematodes were recovered and submitted for parasitological examination. The diagnosis of M. wimsatti infection was based on the histomorphological and parasitological characteristics of the agent and its location in the brain ventricular system of insectivorous bats. The infection likely occurs in other insectivorous bats from South American and Caribbean countries but may be overlooked.

Host–parasite coevolution may result in life-history changes in hosts that can limit the detrimental effects of parasitism. Fecundity compensation is one such life-history response, occurring when hosts increase their current reproductive output to make up for expected losses in future reproduction due to parasitic infection. However, the potential trade-offs between this increase in quantity and the quality of offspring have been relatively unexplored. This study uses the trematode, Schistosoma mansoni, and its snail intermediate host, Biomphalaria glabrata, to better understand how this host life-history response, fecundity compensation, impacts host reproduction. Measures of host reproductive output as well as offspring hatching success and survival were collected to assess the reproductive consequences of infection. Infected snails exhibited fecundity compensation by increasing the number of eggs laid and the overall probability of laying eggs compared to uninfected snails. Parental infection status did not play a significant role in hatching or offspring survival to maturity. Offspring from a later reproductive bout demonstrated a higher hatching success rate. Overall, the lack of an apparent trade-off between quantity and quality of offspring suggests that infected parental snails invest more resources towards reproduction not only to increase reproductive output, but also to maintain the fitness of their offspring, possibly at the expense of their own longevity.

We present a taxonomic, spatial, and thematic overview of the current state of knowledge on helminth parasites of Mexican amphibians. Sixty-six host species have been studied so far, representing 17.5% of the amphibian species distributed in Mexico. A total of 139 nominal species of helminths – 68 platyhelminths, 62 nematodes, three acanthocephalans, three annelids (hirudineans), and three arthropods (pentastomids) – have been recorded parasitizing these hosts. Most taxa found in larval stages have not been identified at the species level. The gastrointestinal nematode Aplectana itzocanensis exhibits the broadest host range, while the bladder fluke Gorgoderina attenuata and A. itzocanensis show the widest geographic distribution. Our analysis of helminthological studies evidenced gaps and biases on research efforts that have been devoted to relatively few host species, regions, and approaches. Most helminthological records come from two species, the cane toad Rhinella marina and the Montezuma's frog Lithobates montezumae, and most studies have focused on describing the helminth fauna of a host species in a particular location or on the description of new helminth species. The highest proportion of records corresponds to the Veracruzan biogeographic province, and helminth richness is significantly correlated with host richness and with total amphibian richness by biogeographic province. Only three provinces (Yucatan Peninsula, Pacific Lowlands, and Baja Californian) have positive, yet still low helminth species discovery effort. Based on our findings, we recommend pursuing research approaches unexplored in Mexico and we provide guidelines to improve research on helminths parasitizing amphibians.

Nematode spicules vary in shape and size even between closely related species and, therefore, constitute key characters in nematode taxonomy for distinguishing between species. Spicules are seldom measured on fresh specimens, but rather at some time after extraction from culled hosts and after a period of preservation of the worms in chemical fixatives or by freezing. We carried out two experiments to assess the effects of freezing in Hanks’ balanced salt solution, 70% or 80% ethanol and 10% formalin (both of the latter at room temperature and after storage at −80°C) on spicule length of Heligmosomoides bakeri at two time intervals after extraction from mice (Experiment 1, one and four weeks; Experiment 2, one and four months). In Experiment 1, no significant differences were detected, although there was some variation between treatments and over time. In Experiment 2, spicule length varied significantly between treatments and over time, the greatest shrinkage being in 80% ethanol and the least in 10% formalin. However, overall variation in spicule length was very limited, accounting for no more than 5.03% change in length over time and 4.95% between treatments at any of the periods of assessment. Therefore, while whole nematodes can shrivel and shrink in preservatives, making many measurements unreliable, our data indicated that spicule lengths are very little changed by preservation techniques over time, and so spicule length remains as a reliable taxonomic character.

This study investigated the in vitro anthelmintic activity of copper oxide (CuO) and zinc oxide (ZnO) nanoparticles (NPs) against Marshallagia marshalli. The in vitro study was based on an egg hatch assay, adult and larvae motility inhibition assays, DNA damage, intensity protein profile along with several oxidative/nitrosative stress biomarkers including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), protein carbonylation (PCO), malondialdehyde (MDA), total antioxidant status (TAS) and nitric oxide (NO) content. Different concentrations of CuO-NPs and ZnO-NPs (1, 4, 8, 12 and 16 ppm) were used to assess anthelmintic effects on three stages of M. marshalli life cycle – that is, eggs, larvae and adult parasites for 24 h. The results indicated that CuO-NPs and ZnO-NPs played a significant role as anthelminthics, and the effect was dependent on time and concentration. The concentrations of 12 and 16 ppm of CuO-NPs and 16 ppm of ZnO-NPs resulted in the induction of oxidative/nitrosative stress (decreased SOD, GSH-Px and CAT, and increased MDA, PCO and NO), increased DNA damage, inhibition of adult and larval motility, egg hatch and low intensity of protein bands following sodium dodecyl sulphate–polyacrylamide gel electrophoresis, compared to control. It was concluded that CuO-NPs and ZnO-NPs could be utilized as novel and potential agents for the control and treatment of M. marshalli infection, and they have the pharmacological potential to be studied in vivo for further utilization in treating parasitic infections.

Urban rodents are associated with parasites and pathogens, which present health risks for humans, but information on factors related to parasite and pathogen infection in rodents in cities of Latin America is scarce. This study analyzes the hosts, host community structure and environmental characteristics of parasite and pathogen fauna present in the three species of urban rodents in an urban area of South America. Rodents were captured seasonally in seven different neighborhoods. Digestive tracts were dissected under stereoscopic microscopy and feces were processed using a sedimentation technique. Protozoa and bacteria were detected through polymerase chain reaction and indirect immunofluorescence techniques. In Rattus norvegicus, Rattus rattus and Mus musculus, ten helminths, three protozoa and two bacteria were found. Six were zoonotic: Toxoplasma gondii; Hymenolepis diminuta; Rodentolepis nana; Strobilocercus fasciolaris; Leptospira borgpetersenii; and Leptospira interrogans. The parasite and pathogen infections were influenced by the host species, the host community structure, the season, and the presence of streams in the neighborhood. Urban rodents may be the infection source of many zoonotic diseases and it is important to generate public policies for this problem. This study is one example of the situation of many cities of Latin America, where peripheral neighborhoods are growing dramatically.

Since the exogenous compound tris(hydroxymethyl)aminomethane (Tris) showed a potent chemoattractant activity for Brugia pahangi infective third-stage larvae (L3), it was assumed that, in natural infection to a host, filarial L3 can be expected to recognize an endogenous Tris-related compound. In addition, a few amino acids have been identified as water-soluble attractants for second-stage juveniles of Meloidogyne incognita, a plant parasitic nematode. Therefore, the present study assesses the in vitro chemotactic responses of B. pahangi L3 to Tris-related compounds and amino acids using an agar-plate assay. Among Tris-related compounds, 2-amino-1,3-propanediol (APD) and 2-amino-2-methyl-1,3-propanediol (AMPD) exhibited a potent chemoattractant activity for filarial L3 at a level similar to Tris. Furthermore, arginine (Arg) was identified as a potent attractant for filarial L3 among amino acids. In addition, filarial L3 were attracted to Arg, APD and AMPD in mild alkaline conditions rather than acidic conditions. The chemoattractant activity of the three compounds for filarial L3 was observed in concentrations between 6.3 and 200 mm. This is the first report to demonstrate that Arg, APD and AMPD are potent chemoattractants for B. pahangi L3. Endogenous Arg and APD, in particular, may be involved in the regulation of the chemotactic behaviour of filarial L3 in the infection to a host. The present results will help to elucidate the mechanism of filarial skin-penetrating invasion of a host.

We make new morphological observations not previously reported for the old acanthocephalan Macracanthorhynchus hirudinaceus (Pallas, 1781) Travassos, 1917, described for the first time about 240 years ago. Our specimens were collected from the wild boar, Sus scrofa Linn., in Ukraine in 2005. We provide comparative morphometrics with other populations from Ukraine, Union of Soviet Socialist Republics, Europe, Brazil and the United States of America. Our specimens from the Ukraine had the smallest trunk (110–120 mm long), longest and thickest hooks, with the third hook being the largest, largest eggs, and a proboscis wider than long. We document the morphology of the proboscis, apical organ, hooks, hook roots, sensory pores, micropores, and eggs with scanning electron microscopy for the first time. We also provide chemical analysis of hooks and eggs using energy-dispersive X-ray analysis, discuss its micropores, and provide a new molecular profile based on 18S rDNA from a European population for the first time. Edge of hook tips feature high levels of calcium and phosphorous but the high level of sulphur is mostly found in the cortical layer of eggs. One new partial 18S rDNA sequence (482 nt length) was generated from an adult specimen of M. hirudinaceus. We present the first 18S rDNA published sequence for this cosmopolitan acanthocephalan obtained from Europe. The amplified region corresponded to the approximate middle region of the small subunit ribosomal ribonucleic acid gene, which is ~1800 nt in length. This molecular contribution is especially valuable in light of the extreme scarcity of genetic information about species of Macracanthorhynchus and of the family Oligacanthorhynchidae as a whole.

Three tapeworm species belonging to the genus Atractolytocestus Anthony, 1958 (Cestoda: Caryophyllidea) were reported from the common carp, Cyprinus carpio L., 1758 in the People's Republic of China so far: Atractolytocestus sagittatus; Atractolytocestus tenuicollis; and Atractolytocestus huronensis. In this study, we identified a putatively new tapeworm species in common carp from the Danjiangkou Reservoir in Central China (Hubei Province). The species is morphologically similar to A. sagittatus, but it differed conspicuously in sequences of three molecular markers. Ribosomal internal transcribed spacers 2 sequence identity of the new species was 94.7–95.5%, 91.8–92.7% and 80.0–83.9% with A. huronensis, A. tenuicollis and A. sagittatus, respectively. cytochrome c oxidase and NADH dehydrogenase subunit 3 sequence identity with these three species was lower than 92%. We conclude that this is a new tapeworm species, and we named it after the locality: Atractolytocestus danjiangkouensis n. sp.

This study presents a list of parasitic fish nematodes from the Brazilian Amazon based on the previous Brazilian list including scientific assessments carried out between 2010 and 2021. A total of 16 families, 48 species and 28 undetermined species of nematodes associated with fish are included in the checklist, in addition to 93 host species and 15 geographical records.