Phenotypic plasticity allows parasites to modify their morphology in response to the ecological and physiological conditions induced by their hosts. In digeneans with complex life cycles and multiple definitive hosts, host-induced variation may complicate species delimitation and taxonomic diagnoses. In this study, we characterised intraspecific morphological variation in Mesorchis uruguayensis (Digenea: Echinochasmidae), a trematode that parasitises fish-eating birds, using an integrative morphological approach. Thirty-eight adult specimens previously collected from five definitive host species in Mexico and molecularly identified as M. uruguayensis were examined. Scanning electron microscopy (SEM) was used to assess qualitative diagnostic traits, and principal component analysis (PCA) based on 19 linear measurements was used to explore morphometric variation among host-associated groups. All specimens retained the characteristic head collar with 22 spines, 10 small spines along the anterior margin of the oral sucker, and a consistent general pattern of tegumental spines. The first two principal components explained 80.9% of the total morphometric variation. However, the host-associated group overlapped substantially, with some differences. Body size, the dimensions of reproductive organs, and the ventral sucker contributed most strongly to this variation. Because all specimens were molecularly conspecific, these differences represent intraspecific morphological variation rather than species-level divergence. Host identity constitutes a biologically plausible source of this variation through differences in intestinal physiology, resource availability, and other host-associated conditions; however, geographic origin, parasite maturity, infection intensity, and individual host condition may also contribute. Our findings emphasise the value of combining stable qualitative characters, morphometric analyses, and molecular evidence to interpret morphological variability and avoid taxonomic misidentification in digeneans.
Translocations of rhinoceros in the 1990s provided an opportunity to investigate the vectors of filaria in Nairobi National Park and Solio Ranch in Kenya. These are high-altitude sanctuaries where rhinos have ulcerative sores attributed to the filarial nematode Stephanofilaira dinniki. Rhinomusca dutoiti, the biting fly closely associated with rhino, did not harbour S. dinniki, but often harboured a small and/or a large form of Habronema. Rhinomusca dutoiti from Kenya was nearly identical to R. dutoiti from South Africa based on gross morphology and a 798 base pair sequence from the 3' end of the Cytochrome Oxidase I gene. Habronema parasites occurred alone or in combination and were smaller than larval forms of H. muscae, the well-known parasite of equines. At Nairobi, prevalence of infections in the proboscis was high at 55%, with mature infections already present in young flies. This finding implied infection during larval development rather than acquisition as an adult fly. Infection patterns were similar in flies trapped or captured by hand from rhinos at Solio Ranch. Habronema was also found in a few Haematobosca spp., at much lower prevalence. Parasites were measured for several body landmarks and were photographed through light microscopy and scanning electron microscopy. These data now provide a foundation for further studies of the biology of Rhinomusca and its relationship with filarial nematodes in wildlife.
In the current study, we used an immunotherapeutic approach in female Swiss albino mice inoculated intraperitoneally with viable protoscoleces. We investigated the potential immunomodulatory effect and protective properties of IL-17A at 125 pg/mL on the development of secondary experimental echinococcosis. Swiss mice were inoculated intraperitoneally (i.p.) with 200 μL of a suspension containing 2000 viable protoscoleces to establish the infection model. IL-17A was administered intravenously two weeks after cystic echinococcosis (CE) induction. Cyst development and hepatic damage were macroscopically and histologically analysed. The hepatic expression of iNOS, TNF-α, NF-κB, CD68, and vimentin was examined. We observed that in vivo IL-17A treatment at 125 pg/mL reduced metacestode growth by 93.8%. Interestingly, treatment at this dose also led to decreased splenomegaly and improved liver tissue architecture. This was associated with a marked reduction in the fibrotic response, as evidenced by decreased collagen and reticulin fibre deposition. Moreover, IL-17A treatment resulted in reduced expression of key inflammatory and fibrotic markers, including iNOS, TNF-α, NF-κB, CD68, and vimentin, in the liver parenchyma. Our findings highlight the antihydatid and immunoprotective effects of IL-17A and support its potential therapeutic role in managing CE.
This study was conducted to determine the in vivo anthelmintic efficacy and clinical safety of crude ethanolic extract (CEE) obtained from Artemisia absinthium in naturally infected Awassi breed sheep with gastrointestinal nematodes (GIN). A total of 18 non-pregnant sheep were divided into 3 groups of 6 animals each: CEE (1.0 g/kg), albendazole (5 mg/kg), and negative control (untreated). Changes in egg counts (EPG) were quantitatively monitored in faecal samples collected before treatment (day 0) and after treatment (days 7 and 15). The research findings showed that A. absinthium CEE significantly reduced the parasite load over time, with the highest efficacy achieved on day 15 (p < 0.001), demonstrating statistically significant efficacy in suppressing the fecundity of GIN agents. According to the faecal egg count reduction test (FECRT), therapeutic success was observed in 76.77% of the CEE group and 100% of the albendazole group. The performance demonstrated by CEE confirmed the potential of plant secondary metabolites to reduce dependence on synthetic drugs, and the absence of any adverse effects during the trial period demonstrated the plant's high biosafety profile. Consequently, A. absinthium offers a powerful, economical, and residue-free biotherapeutic alternative to synthetic anthelmintics in sustainable and organic livestock models, countering global anthelmintic resistance. To the best of our knowledge, this study represents the first investigation in Türkiye evaluating the anthelmintic efficacy of A. absinthium CEE in Awassi breed sheep naturally infected with GIN, providing the first regional efficacy data from Şanlıurfa.
We surveyed trematode parasites infecting 227 gulls from southern New Zealand, comprising 113 red-billed gulls (Chroicocephalus scopulinus) and 114 black-backed gulls (Larus dominicanus), using morphological and molecular approaches. Fifteen trematode species were recovered, including six species new to science: Mesorchis carsonae n. sp., Acanthoparyphium argillamartelliarum n. sp., Himasthla davisi n. sp., Gymnophalloides hutsonae n. sp., Levinseniella trisepsilon n. sp., and Microphallus lagruei n. sp. Nine species occurred in both gull hosts; the remaining six were recorded from only black-backed gulls. New genetic data were generated for 12 species, including all new species, enabling confirmation of species identities and links to larval stages in intermediate hosts, thereby resolving or advancing knowledge of several life cycles. Several parasites represent new host or geographic records, including the first named species of Diplostomum, Gigantobilharzia, Levinseniella, Gymnophalloides, Microphallus and Mesorchis reported from New Zealand. Parasite burdens were generally low, but species richness was high, underscoring gulls as important definitive hosts supporting substantial hidden biodiversity. This study provides the first comprehensive baseline survey of trematode communities in New Zealand gulls and highlights that parasite diversity remains underestimated even in comparatively well-studied hosts. These findings reinforce the importance of incorporating parasites into biodiversity inventories and conservation frameworks.
Short-term thermal stress during heatwaves can potentially affect the transmission of parasites by increasing mortality of infective stages. Using the critical thermal maximum approach (CTmax), commonly used in free-living species, we exposed trematode cercariae of three marine species (Cryptocotyle lingua, Himasthla elongata, Renicola parvicaudatus) to a temperature ramping rate similar to realistic heatwave scenarios in the field and determined their acute temperature limits. The median CTmax values of all cercariae were much higher than the typical temperature extremes observed during heatwaves in the field. CTmax values slightly differed among the three trematode species and were higher than the thermal limit of their first intermediate host, the periwinkle Littorina littorea. This suggests that heatwave effects on trematode cercariae are likely not direct but more indirect, resulting from effects on the survival of their first intermediate host. Given its straightforward methodology and the potential for standardized comparisons of thermal limits among species and ecosystems, the CTmax approach holds promise for ecological research on the thermal biology of parasites.
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.
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.
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.
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.
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.
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.
In this study, 41 individuals of long-tailed cercariae of the genus Echinochasmus parasitizing the freshwater snails Koreoleptoxis spp. were collected in different localities of the southern part of the Russian Far East. Partial nucleotide sequences of the mitochondrial cox1 gene were generated and analysed for all the specimens obtained. Phylogenetic relationships within the family Echinochasmidae were assessed using all available published data. Bayesian inference and maximum likelihood analyses revealed six morphologically similar species or species-level genetic lineages of Echinochasmus circulating in the Russian Far East and on the islands of Japan. Of these, two represent previously described valid species, E. milvi and E. suifunensis.
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.
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.
A new species of thrips-parasitic nematode, Thripinema usitatum n. sp. (Tylenchomorpha: Allantonematinae), is described from thrips collected from flowers in Hainan Province, China. The species is identified using an integrative approach combining detailed morphology, molecular phylogenetic analyses, and biological observations. Thripinema usitatum n. sp. exhibits pronounced sexual dimorphism and a complex life cycle, including obese parasitic females, vermiform infective females, and free-living males with degenerate feeding structures within the body of thrips. The new species is distinguished from its congeners by the absence of a stylet in free-living males, a distinctive two-part bursa extending nearly to the tail terminus, and characteristic shapes of parasitic females and male tails. Molecular characterization was performed using three markers (18S rRNA, 28S D2-D3 rRNA, and mitochondrial cytochrome c oxidase subunit I, mtCOI). Phylogenetic analyses based on 28S D2-D3 rRNA and mtCOI partial sequences consistently recovered T. usitatum n. sp. as a well-supported, monophyletic lineage clearly separated from other entomophilic nematodes. Among the markers examined, mtCOI provided the highest discriminatory power. Biological observations revealed that T. usitatum n. sp. infects thrips at all developmental stages, with a strong prevalence in adult females. Multiple nematode life stages frequently co-occurred within individual hosts, and infection intensities ranged from 1 to 433 nematodes per thrips. These results expand the known diversity of Thripinema and provide a robust framework for future systematic and ecological studies of thrips-parasitic nematodes.
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.
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.
