The concept of ‘ecology of fear’ recognises the importance of non-consumptive effects of predators inspiring fear in their prey, but has subsequently been broadened to include the non-consumptive effects of parasites on their hosts. Here, we experimentally tested whether blue mussels (Mytilus edulis) exhibit species-specific avoidance behaviour in response to infective transmission stages (cercariae) of three trematode species: Himasthla elongata and Renicola roscovita, both of which use blue mussels as hosts, and Cryptocotyle lingua, which parasitises fish. Furthermore, we investigated whether avoidance behaviour could be triggered solely by chemical cues. The results show that mussels reduced clearance rates by 34% in the presence of H. elongata alone and of 51% in the presence of H. elongata and R. roscovita in sympatry, which was comparable to previously reported direct consumptive effects of infection on filtration activity. The presence of C. lingua and R. roscovita alone had no significant effect on clearance rate. The observed reduction in filtration activity resulted in lower infection rates of experimental mussels. Moreover, mussels reduced clearance rates by 42% in the mere presence of chemical cues from the first intermediate host Littorina littorea, while exudates of H. elongata had no additional negative effect. It is evident that a non-consumptive parasite effect can significantly reduce the filtration activity of experimental blue mussels. Considering the magnitude of this reduction and the widespread occurrence of parasitic trematodes, it is reasonable to expect that fear of parasitism has ecological consequences for the functioning role of mussels.

Entomopathogenic nematodes (EPNs) from the genera Steinernema and Heterorhabditis are potent biocontrol agents. They kill insects through a unique symbiosis with pathogenic bacteria (Xenorhabdus or Photorhabdus), making them ideal for integrated pest management due to their broad host range and environmental safety. Despite high species diversity, genomic resources for these nematodes remain limited. The aim of this study was to characterise the nuclear and mitochondrial genomes of a newly described species, S. tarimense, and a putative novel Heterorhabditis species (strain XJ-55), both obtained from Xinjiang, China. A comprehensive genomic annotation and analysis were conducted to investigate the evolutionary origins of insect parasitism and the molecular adaptation mechanisms involved in host–parasite interactions. Through Illumina sequencing and de novo assembly, we obtained fragmented yet biologically informative genomes for both species. The assembly of S. tarimense reached a BUSCO completeness of 84.06% with an estimated genome size of 84.27 Mb, while that of Heterorhabditis sp. XJ-55 achieved 92.28% completeness with an estimated size of 75.11 Mb. Functional annotation revealed conserved metabolic profiles between the two species, with the Metabolism category being the most abundant. Mitochondrial genomes were successfully reconstructed using MitoZ and NOVOPlasty, resulting in a complete mitogenome of S. tarimense (13,836 bp) and a partial mitogenome of Heterorhabditis sp. XJ-55 (16,865 bp). Comparative mitogenomic analysis highlighted characteristic features such as pronounced A+T bias and distinct codon usage patterns, providing new evolutionary insights into these genera. These genomic resources establish a foundation for future comparative studies and functional investigations, with promising implications for enhancing the biological control efficacy of EPNs in sustainable agricultural systems.

Hysterothylacium thalassini third-stage larvae (L3), commonly found in marine fish, are known to induce liver injury, oxidative stress, and immune disturbances when transmitted to mammalian hosts. This study investigated the pathological effects of purified crude extracts derived from fresh, heat-treated, and frozen L3 larvae on liver function, oxidative status, and immune responses in a murine model. Thirty Saurida tumbil fish were examined for L3 larvae, which were processed under three conditions: fresh (24 ± 2 °C for 60 min), heat-treated (100 °C for 60 min), and frozen (−20 °C for 24 h). Twenty male C57BL/6 mice were randomly allocated into four groups and inoculated with larval extracts at a 14-day interval. Mice exposed to fresh larval extracts exhibited significant weight loss, elevated liver enzymes (ALT, AST, ALP), hyperglycemia, and reduced total protein levels, alongside severe hepatic damage characterized by necrosis and inflammatory infiltration. Antioxidant enzyme activities (CAT and SOD) were markedly decreased, whereas oxidative stress markers (NO and H₂O₂) were increased. Additionally, there was significant upregulation of iNOS, TNF-α, and IL-10 gene expression, accompanied by elevated iNOS, IL-10, and IgE protein levels, indicating strong inflammatory and Th2-type immune responses. In contrast, extracts from heat-treated and frozen larvae resulted in attenuated pathological effects, including improved liver function, reduced oxidative stress, and moderated immune responses. These findings demonstrate that untreated L3 larval extracts exert pronounced hepatotoxic and immunomodulatory effects, while thermal and freezing treatments significantly reduce their pathogenicity and support immune homeostasis, highlighting potential strategies to mitigate parasite-induced host damage.

Pooling of gastropod samples is frequently used in surveys of the neurotropic nematode Angiostrongylus cantonensis to reduce cost and processing time. Here we highlight a potential limitation of this technique using the snail Theba pisana as an example. Pooled samples tested negative using a high-sensitivity qPCR assay, whereas subsequent individual testing revealed positive cases. This pattern is consistent with a dilution effect, where low parasite DNA concentrations could lead to false-negative results. These findings suggest that pooling may reduce diagnostic sensitivity in regions where infection intensities are low and should be applied with caution.

In vivo anthelmintic assay models are essential for evaluating candidate compounds in target species. Several rodent-helminth systems have been developed, with the Cobb-Wistar rat-T. colubriformis model emerging as promising for early-stage screening. Although this model has demonstrated utility, the development of an alternative model using a more widely accessible rat strain represents a valuable opportunity for advancing in vivo screening of anthelmintics. This study evaluated different immunosuppressants and regimens to identify treatments yielding the highest and most consistent worm burdens in experimentally infected Sprague-Dawley rats. Thirty rats were assigned to five groups (n = 6). Group 1 received unmedicated feed (negative control), while Groups 2, 3, and 4 received hydrocortisone acetate (HCA) in their diet at 60 ppm, 80 ppm, and a two-phase regimen of 200 ppm followed by 60 ppm, respectively. Group 5 received intramuscular methylprednisolone acetate (MPA) on three occasions. All animals were orally infected with T. colubriformis third-stage larvae, and necropsies were performed on Day 13 post-infection to recover worm burdens. Treatment had no effect on worm counts. The 80-ppm HCA group produced the highest mean burden with high variance; the 200:60 ppm group showed lower counts but less variance, and the 60-ppm HCA and MPA groups were comparable to controls. There was insufficient evidence to support the Sprague-Dawley rat-T. colubriformis model but, given the results of this study, further investigation and development are warranted.

Trichuris muris infections in laboratory mice underpin current understanding of host-parasite interactions, yet the extent to which these insights apply to natural systems remains largely untested. In this study, we experimentally infected wild-caught Mastomys natalensis with Trichuris mastomysi under controlled conditions. Mice were assigned to either a single high-dose infection or repeated low-dose exposure. Larval infection success and intensity were assessed 21 days post-infection. Infection success was high in both exposure groups, and infection dose strongly influenced parasite burden, with high-dose animals carrying significantly more larvae than low-dose animals. These results demonstrate that T. mastomysi readily establishes in wild-caught M. natalensis and that exposure dose primarily affects early larval burden rather than infection success. By experimentally infecting a natural rodent host under controlled conditions, this study links mechanistic laboratory approaches with ecologically relevant host-parasite dynamics in the wild.

Antiparasitic agents are routinely used in companion animal medicine. However, longitudinal evidence describing real-world usage patterns in dogs remains limited. This study aimed to characterise patterns, routes of administration, temporal trends, and seasonal variation in antiparasitic drug use among Golden Retrievers enrolled in a large prospective cohort study in the United States. A descriptive analysis was conducted to summarise antiparasitic usage data from the Morris Animal Foundation’s Golden Retriever Lifetime Study over nine study years (corresponding to years 0 to 8). Percentages with respective 95% CI were used to summarise drug types, therapy combinations, routes of administration, and temporal and seasonal patterns of use. A total of 17,715 antiparasitic use records were analysed. Drug usage pattern was highly concentrated within a limited number of products, with the ivermectin–pyrantel pamoate combination accounting for 23.0% of all recorded use. Other commonly used agents included afoxolaner (9.73%), metronidazole (9.16%), and lufenuron–milbemycin oxime (8.95%). Oral formulations were predominant, representing 65.28% of all administrations. Single-agent therapy accounted for 47.27% of use, while two-drug combination therapy represented 46.65%. The antiparasitic medications spanned multiple pharmacological classes targeting both endo- and ectoparasites, including anthelmintics, ectoparasiticides, and antiprotozoals. Antiparasitic use declined by 1.8% over the study period. We observed a seasonal variation in antiparasitic drug usage, with higher usage during cooler months (winter) and lower use in summer. These findings provide baseline evidence of the burden of endoparasites and ectoparasites in Golden Retriever dogs and highlight the need for stewardship-oriented parasite control strategies in companion animal practice.

Canine angiostrongylosis is a life-threatening disease caused by infection with the metastrongyloid nematode Angiostrongylus vasorum. As animal travel and translocation have increased in recent times, many infectious agents, including A. vasorum, have expanded to new geographic areas. Here we report the first molecularly confirmed case of angiostrongylosis in a translocated dog in Estonia. We also analyse the phylogenetic relationship of the isolate with previously described European isolates and describe the challenges encountered in diagnosing this disease. Given the expanding geographic distribution of A. vasorum across Europe, our findings underscore the need for improved diagnostic awareness to control the parasite’s transmission.

This study assessed the predatory activity (PA) of Dactylellina candida (Dc) and Arthrobotrys musiformis (Am) against Haemonchus contortus infective larvae (HcIL). It also examined the effect of crude extracts from HcIL, Panagrellus redivivus (Pr), and Turbatryx aceti (Ta) on liquid cultures of these fungi as potential enhancers of their nematocidal activity against HcIL. The fungi were cultured in sweet potato dextrose broth (SPDB), and the corresponding nematode crude extract (NCE) was added to flasks containing the fungus. Control groups included fungi without extracts and media alone. Liquid culture filtrates were assessed at three concentrations (100, 50, and 25 mg/mL) against HcIL during 72 hours at 18–25°C. The highest mortality (86.61%) was observed with Dc stimulated by HcIL crude extract (HcCE) at 100 mg/mL (p < 0.05). Arthrobotrys musiformis showed 47.49% mortality when stimulated with HcCE. Both fungi increased their nematocidal activity when exposed to HcCE, demonstrating their potential nematocidal activity against H. contortus.

Anoplocephalidae (Cestoda: Cyclophyllidea) is a diverse family, with the subfamily Anoplocephalinae comprising 59 genera that primarily parasitize the digestive tract of rodents and birds. Monoecocestus threlkeldi was originally described from the northern vizcacha, Lagidium peruanum, in Junin, Peru, and subsequently reported in cricetids (Holochilus spp.) in Argentina and Bolivia. In the present study, we describe a new species of the genus Monoecocestus parasitizing the southern vizcacha, Lagidium viscacia, based on specimens collected in Puno, Peru, at an elevation of 3932 m a. s. l. A total of 45 specimens of the new species were obtained and processed for morphological and molecular analysis. For molecular analysis, DNA sequences of three markers were generated: the nuclear 18S, 28S, ITS, and mitochondrial cox1. The molecular data were compared with sequences available in GenBank, confirming its inclusion in the genus Monoecocestus. Morphologically, the new species is similar to M. threlkeldi, but it can be distinguished by its smaller body size, scolex, cirrus pouch, and number of proglottides. The description of the new species Monoecocestus viscaciae improves our understanding of the diversity of cestodes in high-altitude Andean ecosystems and provides new insights into host specificity within the genus Lagidium.

Anthelmintic resistance (AR) in gastrointestinal nematodes is insufficiently studied in cattle in many European regions, including France, where only three studies have been conducted in the north-west. This study evaluated the efficacy of benzimidazoles and avermectins in cattle from a mid-mountain region in central France. Faecal egg count reduction tests (FECRT) were performed in 22 groups of 10–25 calves from 16 dairy or beef farms. Each group received either oral oxfendazole (OFZ, 11 groups) or injectable ivermectin (IVM, 11 groups). Faecal samples were collected in a paired study design before (D0) and after treatment (D10-14 for OFZ, D14-17 for IVM). Individual faecal egg counts (FECs) were determined using the Mini-FLOTAC method, and pooled faecal samples were cultured per group to determine the proportions of Ostertagia and Cooperia larvae using droplet digital PCR. Efficacy classification (resistant, susceptible or inconclusive) was determined for each group according to the WAAVP guidelines, using the fecrt.com web application and the clinical protocol scenario with a grey zone of 90–99%. IVM resistance was detected on 10 of 11 farms, with 33–49% and 51–67% of larvae being Ostertagia and Cooperia after treatment, respectively. The remaining farm had inconclusive results. OFZ resistance was detected on 2 of 11 farms, with 100% and 97% of larvae being Ostertagia after treatment. The remaining 9 farms were classified as susceptible. This study provides valuable local insights into AR, which could help raise awareness among farmers and veterinarians and encourage changes in treatment practices.

This study evaluated the in vitro activity and mode of action of ethanolic extracts (Et) and respective different polarity fractions (hexane, ethyl acetate (EA), butanol, aqueous) from basidiomes and mycelium of Pleurotus djamor against Haemonchus contortus eggs, using the egg hatching test. After incubation (concentration gradient from 20 to 3600 μg/mL), emerged larvae and eggs were observed and counted, differentiating between morulated eggs (ME) and larvated eggs (LE). Effective concentrations required to inhibit 50% or 90% (EC50; EC90) of hatching, and their respective 95% confidence intervals (95% CIs) were determined. Extracts and fractions obtained from basidiomes exhibited lower EC50 (P < 0.05) than those obtained from the mycelium, except for the hexane basidiome fraction, which showed less activity compared to the mycelium fraction. Both butanol fractions presented similar EC50 (~140 μg/mL). Polar mycelium materials exhibited a higher proportion of LE, while the hexane fraction demonstrated an ovicidal effect (abundant ME), and the EA fraction was inactive. The low EC50 of extracts and fractions of basidiomes and mycelium confirmed that P. djamor is a promising non-conventional anthelmintic that should be evaluated under in vivo conditions with small ruminants. The EC50 values were better than most tropical plant materials reported to date.

This study was conducted to determine the prevalence of the gastric nematode Ollulanus tricuspis in domestic cats in Samsun province, Türkiye, and to perform molecular phylogenetic analysis of the obtained isolates. Following the initial diagnosis of O. tricuspis in a domestic cat presenting with chronic vomiting, stomach contents from 50 necropsied cats were microscopically examined for a broader survey. The ITS-1, 5.8S, and ITS-2 gene regions of the parasites obtained from positive samples were amplified and sequenced using PCR. Phylogenetic analyses were performed using the maximum likelihood (ML) and Bayesian inference (BI) analyses. The prevalence of O. tricuspis in the examined samples was determined to be 6%. Literature data show a wide variation in global prevalence, ranging from 0.2% (USA) to 42% (Australia). This study is the first report to reveal the presence of O. tricuspis at the molecular level in Türkiye.

In the Amazon region, Arapaima gigas holds significant gastronomic and cultural value compared to other fish species due to its large size. This fish is home to various helminth species that parasitise primarily its gastrointestinal organs. During the 2023 dry season, a total of 60 gastrointestinal organs from A. gigas specimens were collected from a fisheries management program conducted by local residents within the Mamirauá Reserve. For gastric parasitological analysis, each organ was separated in containers, and the parasites were recovered, washed, and fixed in 70% alcohol for analysis by light and scanning electron microscopy. Additionally, stomach samples of the hosts infected with parasites were fixed in 10% formalin for histopathological examination. 16% of the parasitised fish presented ulcerative areas in the gastric mucosa of varying degrees. Microscopically, a severe inflammatory reaction with infiltration of eosinophils, lymphocytes, and macrophages was observed, associated with co-infection by Goezia spinulosa and Neoterranova serrata. Additionally, morphological and morphometric data aided by scanning electron microscopy for N. serrata were added.

The study of hyperinfection in animal models is important to control strongyloidiasis as a public health concern. While human strongyloidiasis is often chronic, experimental models allow the assessment of the acute phase of hyperinfection. This study evaluated excretory/secretory (E/S) antigens of Strongyloides venezuelensis L3 larvae to detect IgG antibodies in serum samples from rats immunosuppressed or not and experimentally infected or not with S. venezuelensis. Infection parameters and IgG detection by the antigenic extracts – total saline extract (TS), E/S in RPMI 1640 (RPMI E/S), and E/S in phosphate buffered saline (PBS E/S) – were evaluated. RPMI E/S achieved the best diagnostic parameters, showing no reactivity with non-infected controls. These data demonstrate that E/S antigens are effective for detecting strongyloidiasis during the acute hyperinfection window, offering a reliable tool for experimental research and potential translational applications for screening high-risk patients.

Understanding the dynamics of host-parasite interactions is essential for uncovering the ecological and evolutionary processes shaping natural populations. In this study, we investigated the spatial and temporal patterns of prevalence of the cestode Schistocephalus solidus in 4 Alaskan populations of threespine stickleback (Gasterosteus aculeatus) over 11 years (1996 to 2006). Additionally, we assessed host tolerance through key indicators such as the Parasite Index and the presence of fibrotic scar tissue, a specialized form of resistance in this system. We observed fibrosis formation in both infected and uninfected fish across all populations, with notable year-to-year variability in Cornelius Lake. Here, fibrosis prevalence ranged from 9% in 1997 to 63% in 1998, coinciding with the highest cestode prevalence recorded in this population. Willow Lake stickleback displayed persistently high Parasite Indices, with parasite weights occasionally exceeding host eviscerated weights, and experienced a potential epizootic from 2000 to 2005. Cestode prevalence remained stable in Rocky and Cornelius Lakes and was consistently low in Lazy Lake. Our findings demonstrate significant variation in cestode prevalence, parasite burden, and resistance mechanisms among populations and between years. Importantly, the decoupling of fibrosis formation from infection status highlights the multifaceted nature of host-parasite interactions. Our study emphasizes the value of long-term datasets in revealing spatial and temporal patterns in host-parasite dynamics. Future research integrating ecological and genetic frameworks will be critical for elucidating the drivers of resistance and tolerance and their evolutionary implications.

In this work, the life cycle of Gnathostoma turgidum was studied both in natural temporary water bodies and under experimental conditions, with materials collected from the municipality of San Francisco Ixhuatán, Oaxaca. Adult nematodes inhabit the interstitial layers of the stomach in the definitive host (Didelphis virginiana) and release their eggs into the environment via faeces, typically in a dry environment. Under these conditions, the eggs remain quiescent until the onset of the rainy season. Development of early third-stage larvae occurs in cyclopoid copepods. Fry acts as transport and/or intermediate hosts, while frogs (Lithobates forreri) serve as obligatory intermediate hosts for advanced third-stage larvae, ultimately transmitting the parasites to the definitive host. Notably, the precocity phenomenon, typical of larval development in intermediate hosts, occurs in this species within the definitive host. Precocity is likely a response to host behaviour or other ecological factors that restrict transmission to narrow spatial and temporal windows. Adults die at the end of the rainy season. The marked seasonality of this species is mainly attributed to the combination of two factors: (i) the seasonal predation of frogs by the definitive host, and (ii) expulsion of adult stages as immune-mediated ‘self-cure’. This study represents the first documentation of birds acting as paratenic hosts for this nematode.

The trematode Maritrema gratiosum Nicoll, 1907 has a heteroxenous life cycle comprising a marine gastropod as its first intermediate host, a barnacle as its second intermediate host, and a bird as its definitive host. Globally, the species is widely distributed from subtropical waters of the South China Sea to arctic waters of the Barents Sea. In European waters (namely, western Europe and the Barents Sea), the complete life cycle of M. gratiosum is known. Elsewhere in its range, however, its life cycle remains incompletely understood. Clarifying its distribution and resolving unknown host associations are essential for advancing a more holistic view of host–parasite dynamics and their ecological role in intertidal ecosystems. In this study, M. gratiosum was detected using DNA-based assays in individuals of the barnacle Balanus glandula Darwin, 1854 that were collected from the rocky intertidal zone along the southern coast of British Columbia, Canada. This finding provides the first molecular evidence of this trematode species in the Pacific, complementing earlier records. The same molecular approach can be extended to identify region-specific hosts, such as the first intermediate (molluscan) host in the Pacific region, which remains unidentified.

Haemonchus contortus is a highly pathogenic gastrointestinal nematode of domestic and wild ruminants whose epidemiological success is closely linked to high reproductive capacity. For female daily egg output, however, direct observations remain limited, and published estimates vary widely, ranging from fewer than 20 to 10,000–15,000 eggs per female per day. This study assessed in utero egg counts in female H. contortus recovered from experimentally infected lambs in order to evaluate their implications for fertility relative to values commonly cited in the literature. Archived female nematodes from a previously published experiment were used to conduct the study. In total, 147 female worms recovered from 14 sheep were examined. It was found that the average in utero egg count was 345 (SD = 145) eggs per H. contortus female. Regression analysis provided no clear evidence that the experimental design substantially influenced this parameter. In addition, female body length was positively associated with egg counts, though the relationship was not strictly linear. Overall, the present study supports moderate rather than high estimates of female daily egg output for H. contortus.