Coinfections of hosts by multiple parasite species and strains are widespread in nature. Theory suggests that these infections have a key influence on the virulence, or harm caused, to hosts. However, it is still unclear whether multiple parasites, which may compete for resources and space, are indeed worse for hosts across the tree of life. To test this hypothesis, we conducted separate meta-analyses based on different expectations derived from virulence in single infections. We included 68 effect sizes from 19 experiments on non-human animal host species and 38 parasite species combinations. We found that coinfections are overall more virulent than the mean degree of harm caused by both parasites in retrospective single infections. That said, the coinfection virulence level is similar to that of the most virulent parasite, and less than the additive virulence of both single infections. These results suggest that the most virulent parasite is the primary driver of virulence in coinfection. This finding has implications for parasite spread in nature and suggests we focus on controlling the more harmful parasites in the first instance, when trying to limit the damage caused by coinfection.

The taxonomy of wide distributed parasites across continents has rarely been evaluated using molecular data, and it remains unclear whether their apparent broad distributions reflect true cosmopolitan and monophyletic lineages. There is also the expectation that long-term parasite–host associations shape the evolution of parasitic lineages and should therefore be reflected in parasite taxonomy. Laelaps Koch, 1836 (Mesostigmata: Laelapidae) is an example of a widespread genus, reported from multiple continents, parasitizing Cricetidae and Muridae rodents. The aim of this study is to evaluate whether Laelaps is monophyletic and truly broadly distributed across continents. To this end, we generated new nuclear (18S-ITS1-5.8S-ITS2-28S) and mitochondrial (cytochrome oxidase I) sequences from 8 species of Laelaps, and 4 related laelapid mite species of the genera Androlaelaps Berlese, 1903, Gigantolaelaps Fonseca, 1939 and Mysolaelaps Fonseca, 1936 associated with cricetid rodents from Argentina. Those sequences were analysed together with sequences from laelapids parasitizing native South American cricetids and from South Africa available in GenBank. Phylogenetic analyses revealed that Laelaps is polyphyletic. Within Cricetidae, tribal host association appears to drive phylogenetic structure, with cricetid-associated Laelaps lineages recovered as more closely related to Gigantolaelaps and Mysolaelaps than to each other. Murid-associated Laelaps from South Africa were recovered as lineages separated from cricetid-associated Laelaps, suggesting that the deep divergence between Cricetidae and Muridae may also shape laelapid phylogeny, a pattern that requires broader sampling to be conclusively evaluated. These results challenge the monophyly and broad distributional status of Laelaps and highlight the need for integrative taxonomic revision of this genus.

The heligmosomid nematodes Heligmosomum mixtum and Heligmosomoides glareoli are dominant helminths infecting bank voles (Clethrionomys glareolus) in the temperate forests of NE Poland. Both are relatively long-lived species that accumulate in hosts with increasing host age. Based on studies showing that the closely related species, Heligmosomoides bakeri is immunomodulatory in murine hosts, we hypothesized that heligmosomid-infected bank voles should show higher prevalence and abundance with other helminths. To test this hypothesis, we analysed a database containing quantitative data on helminth parasites of bank voles (n = 922), comprising worm burdens recorded during 4 surveys, conducted at 3- to 4-year intervals, in 3 forest sites, during late summer of each year. After controlling for both intrinsic and extrinsic factors, the presence of heligmosomid nematodes was significantly associated with higher species richness of other helminth species, with the greater likelihood of voles carrying other helminth species, with higher worm burdens of other helminths and with significant positive covariance of heligmosomid burdens with those of other concurrently residing helminths. These patterns might be explained by a number of biological processes, including correlated host exposure or correlated host susceptibility not driven by the parasitic infections themselves. However, we consider it most likely that these results are consistent with the idea that like H. bakeri, the heligmosomid nematodes of bank voles employ non-specific immunomodulation to facilitate their own long-term survival, with the consequence that other concurrently infecting intestinal helminths benefit.

Parasitic diseases, including scabies and pediculosis, pose significant public health concerns, particularly in developing countries. Despite their non-lethal nature, these diseases can cause considerable morbidity. This study aimed to assess the national and subnational burden of scabies and pediculosis in Ecuador during 2021 and explore the spatial correlations between these diseases and environmental factors. An observational, cross-sectional study was conducted using 2021 outpatient data from Ecuador’s Ministry of Public Health. Municipal incidence rates were calculated for scabies (ICD-10 B86) and pediculosis (ICD-10 B85). Local Indicators of Spatial Association analysis was performed to identify epidemiological hot and cold spots. Associations with climatic variables (rainfall, temperature and altitude) were examined using Wilcoxon tests and ordinary least squares regression. A total of 20 722 scabies cases and 3558 pediculosis cases were identified, with national incidences of 118.45 and 20.33 per 100 000 population, respectively. Both diseases were more frequent in women. Scabies hot spots were located in the Coast and Amazon regions and associated with higher rainfall, higher temperature and lower altitude. Pediculosis hot spots were located exclusively in the Amazon region and associated with higher rainfall and higher altitude. Climatic factors explained 24.3% of scabies variance but only 6.3% for pediculosis. This study underscores the importance of climatic and socio-environmental factors in the transmission of scabies and pediculosis and provides valuable epidemiological data for future control efforts in Ecuador.

Although venomous snakes from the family Viperidae, such as Bothrops atrox, are recognized for their medical importance due to snakebite accidents, few studies on parasitological aspects have been carried out with them, especially in the Amazonia region. Using morphological and molecular tools, we described a novel haemogregarine species infecting the common lancehead snake B. atrox from Eastern Amazonia, Brazil. Hepatozoon atrocis sp. nov. has mature gamonts that are morphologically distinct from those reported in the literature, which are often compact, with dispersed or encapsulated cytoplasm and chromatin. In the phylogeny recovered from the 18S rRNA gene, the Hepatozoon atrocis sp. nov. sequences formed a new clade, comprising a sister group to Hepatozoon spp. detected in other snakes, anurans, lizards and marsupials. This study reports the first Hepatozoon species described in the common lancehead snake. In addition, it provides a robust review of haemogregarine species infecting viperids from all over the world.

Bat flies (Diptera: Nycteribiidae and Streblidae) are obligate blood-feeding ectoparasites of bats and are increasingly recognised for their potential role in host-specific co-evolution and disease transmission. Despite their ecological importance, the diversity, host associations and evolutionary relationships of bat flies in Australia remain poorly characterised. This study provides the first integrative assessment of nycteribiid bat flies parasitising Pteropus species in North Queensland, combining morphological taxonomy with cytochrome c oxidase subunit 1 (COX1) sequencing and phylogenetic analysis. A total of 304 bat flies were collected from 79 rescued pteropodids, representing three host species: the little red flying fox (Pteropus scapulatus), the black flying fox (Pteropus alecto) and the spectacled flying fox (Pteropus conspicillatus). Morphological examination of the bat flies identified two taxa, Cyclopodia australis and Cyclopodia albertisii, which were further confirmed by maximum likelihood phylogenetic analysis of COX1 sequences with distinct clade formations delineating species. C. australis was found almost exclusively on little red flying foxes. C. albertisii was mainly associated with both black flying foxes and spectacled flying foxes, with very limited association with the little red flying foxes. These findings underscore the utility of integrative taxonomic approaches in researching bat fly diversity and host specificity. They also highlight the potential for co-evolutionary divergence and emphasise the need for expanded geographic sampling and genomic analysis. This research provides critical baseline data for understanding ectoparasite biodiversity in Australia and contributes to future studies of host–parasite interaction, vector ecology and wildlife disease surveillance.

Phlebotomine sand flies are found across multiple regions of Thailand, with growing recognition of their role in transmitting zoonotic pathogens. Environmental factors, including climate variability and vector ecology, may influence their distribution and activity, contributing to the potential spread of zoonotic pathogens in Southeast Asia. However, comprehensive data on sand fly distribution in Thailand remain limited. To address this gap, a systematic review was conducted following PRISMA guidelines. Out of 112 records retrieved, 33 met the inclusion criteria and quality assessment for further analysis. As per results, sand flies are widespread in Thailand, with a high level of species diversity comprising 42 species of 6 different genera. However, several provinces lack data on the presence and distribution of sand flies. Eleven species were identified as the overall abundant species throughout the studies from January 2007 to June 2025 and grouped by abundance: low-abundance species (Sergentomyia barguesae, Sergentomyia phadangensis, Sergentomyia barraudi and Sergentomyia indica), abundant but understudied species (Sergentomyia sylvatica, Sergentomyia anodontis and Neopulpus vietnamensis) and most abundant species (Sergentomyia hodgsoni, Sergentomyia gemmea, Sergentomyia iyengari and Sergentomyia khawi). From the most abundant species, S. khawi tested positive for several pathogens, such as Leishmania spp., Trypanosoma spp., Bartonella spp. and orbivirus. Besides, S. khawi has been shown to exhibit human-biting behaviour through the analysis of blood meal. These findings raise concerns about its potential role in pathogen transmission, especially concerning zoonotic pathogens. However, vector competence remains unproven for some of these pathogens, suggesting the need for further research.

Nematodes constitute one of the most diverse and ecologically significant parasite groups in fishes, yet their diversity and host associations remain poorly documented in tropical freshwater systems. In this study, a community-wide survey of 10 fish species from La Mojana wetland was conducted to assess nematode diversity and host associations. The highest infection indices were recorded in Pseudoplatystoma magdaleniatum (Pimelodidae), Sorubim cuspicaudus (Sciaenidae) and Sternopygus macrurus (Sternopygidae). Morphological examination revealed 2 distinct nematode morphotypes corresponding to larval Contracaecum (Anisakidae) and adult camallanids. Molecular analyses based on ITS2, 18S rRNA, 28S rRNA and mitochondrial rrnS markers resolved well-supported lineages corresponding to Contracaecum jorgei Sardella, Mancini, Salinas, Simões & Luque, 2020 and Spirocamallanus sp. The multilocus approach demonstrated the coexistence of phylogenetically distinct nematode groups within the same fish community. Patterns of parasite association revealed a broader host distribution for Contracaecum, whereas Spirocamallanus showed more restricted occurrence. Coinfections reflected the structural complexity of parasite communities in this tropical system. Because fish represent a primary protein source for local communities in La Mojana, the detection of anisakids raises considerations for food safety and public health. This study provides the first multilocus characterization of nematode diversity and host associations in the region, contributing to the understanding of parasite ecology in tropical freshwater ecosystems.

This study describes Vairimorpha rumexii sp. nov., a newly identified microsporidian parasite infecting Gastrophysa viridula, the green dock leaf beetle, in northeastern Türkiye. Microscopic examination revealed 2 distinct spore types, with light microscopy and Giemsa staining confirming both disporoblastic and octosporoblastic sporulation cycles characteristic of the genus Vairimorpha. Transmission electron microscopy provided detailed insights into spore ultrastructure, including polar tube configuration, spore wall stratification and nuclear arrangement. Molecular characterization using partial small subunit ribosomal RNA (SSU rRNA) and RNA polymerase II gene sequences, combined with phylogenetic analyses (maximum likelihood and Bayesian inference), placed V. rumexii sp. nov. in a distinct clade, closely related to but genetically separate from Vairimorpha gastrophysae. Notably, pairwise comparison of SSU rRNA sequences revealed a genetic distance of 0.0608 between the 2 species, supported by 72 nucleotide substitutions and 32 deletions, clearly indicating molecular divergence. The integration of morphological, ultrastructural and multilocus molecular data robustly supports its taxonomic distinctiveness as a novel species. This discovery expands the known diversity of microsporidia associated with Chrysomelidae, highlights the value of integrative taxonomy in resolving cryptic species and contributes to the understanding of Türkiye’s microsporidian fauna, potentially informing future biological control strategies.

Antimalarial drug resistance has evolved repeatedly and independently in both Southeast Asia and South America, but functional studies of parasite resistance have almost all concentrated on Asian isolates. Colombia contributes nearly one-third of all Plasmodium falciparum cases in South America, primarily focused on the Pacific Coast. We assessed the presence of resistance associated genotypes and phenotypes in this region using a panel of P. falciparum isolates collected across 23 years, with a specific focus on sensitivity to historically used antimalarials chloroquine, mefloquine, pyrimethamine and sulfadoxine. The sensitivity profiles were predicted genetically using a combination of quantitative PCR assays and sequencing of known resistance-associated loci, including the artemisinin resistance-associated gene PfKelch13. The isolates were then assessed phenotypically by introduction to in vitro culture allowing both antimalarial sensitivity testing and the establishment of a biobank of Colombian isolates for further work. We established that multiple antimalarial resistance associated genotypes and phenotypes, particularly for chloroquine and mefloquine, persist across the Colombian Pacific Coast but found no evidence for the presence of artemisinin resistance-associated polymorphisms. The continued presence of resistance against historically used antimalarials argues against the use of these drugs as partner therapy for artemisinin and highlights the unique epidemiological environment of the Pacific Coast which allows for long-term maintenance of resistance.

The genus Kalicephalus Molin, 1861 comprises hookworms parasitizing the gastrointestinal tract of reptiles, particularly snakes, and currently includes 34 recognized species worldwide. Despite their diversity, the taxonomy of the genus remains poorly resolved because most species have been described primarily from morphology and molecular data remain limited. During a helminthological survey of monocled cobras (Naja kaouthia) from central Thailand, large hookworms were recovered from the oesophagus that corresponded morphologically to the group traditionally assigned to Occipitodontus but differed from previously described species. Using an integrative taxonomic approach combining light microscopy, scanning electron microscopy, morphometric analyses and molecular phylogenetic analyses based on nuclear 18S ribosomal RNA (18S rRNA) and mitochondrial cytochrome c oxidase subunit I (COI) sequences, Kalicephalus colossus sp. nov. is described herein. The new species is distinguished by its exceptionally large body size, posteriorly projecting buccal capsule, equal alate spicules, lobate copulatory bursa and oesophageal localization. Multivariate analyses revealed clear sexual dimorphism without evidence of discrete morphotypes. Phylogenetic analyses recovered K. colossus sp. nov. as a distinct lineage within Kalicephalus, with genetic divergences of 1.1–1.4% for 18S rRNA and 12–13% for COI relative to congeners. The parasite was detected in 18% of examined hosts, with infection intensities ranging from 1 to 48 individuals per cobra, and was recorded only from suburban localities surrounding Bangkok. No obvious gross pathological lesions were observed during necropsy. The discovery of K. colossus sp. nov. expands current knowledge of reptile hookworm diversity in Southeast Asia and highlights the importance of integrative taxonomy for resolving parasite biodiversity.

This study aimed to investigate the diversity, prevalence and host specificity of Dictyocaulus lungworms in free-ranging wild ungulates in Lithuania using morphological and molecular approaches. A total of 129 individuals representing 4 host species (red deer, roe deer, moose and European bison) were examined. Four Dictyocaulus species were identified: D. cervi, D. skrjabini, D. capreolus and D. viviparus bisontis. Infection parameters varied markedly among host species. Red deer showed the highest prevalence and parasite diversity, whereas European bison exhibited low prevalence but relatively high infection intensity. Moose displayed intermediate infection levels with a high proportion of co-infections, while roe deer were infected exclusively with the host-specific species D. capreolus. Co-infections involving multiple Dictyocaulus species were common in cervids, indicating complex transmission dynamics. Molecular analyses based on mitochondrial (cox1) and nuclear (SSU rDNA) markers confirmed species identification and revealed clear genetic differentiation among taxa. Phylogenetic incongruences between markers suggest potentially complex evolutionary relationships, possibly influenced by co-infections and host overlap. These findings provide the first comprehensive insight into Dictyocaulus infections in wild ungulates in Lithuania and highlight the importance of combining morphological and molecular methods for accurate parasite identification. The results contribute to a better understanding of lungworm epidemiology and host–parasite interactions in wildlife and emphasize the need for improved surveillance strategies.

Monoplectanum monogeneans are gill parasites specific to fish in the family Sillaginidae. The sillaginid fish were collected from the middle and upper Gulf of Thailand and the Andaman Sea, Thailand, from May 2024 to January 2025. A total of 2096 fish belonging to 5 species- Sillago aeolus, S. asiatica S. indica, S. ingenuua and S. sihama were identified. Three species of Monoplectanum monogeneans were detected in 3 fish species, including 1 newly described species, M. sillaginis sp. nov. Monoplectanum sillaginis sp. nov. was found to infect 3 fish species, S. aeolus, S. indica and S. sihama, collected from the upper Gulf of Thailand. Monoplectanum youngi infected S. indica, representing a new host record, and S. sihama from both the middle and upper Gulf of Thailand. Monoplectanum australe was found to infect only S. aeolus, which was collected from the upper Gulf of Thailand. Overall prevalence and mean intensity of infections were 11.21% and 1.72, respectively. Regarding morphological features, no significant differences in key characters of both M. australe and M. youngi were observed when comparing the current and original descriptions. Monoplectanum sillaginis sp. nov., can be distinguished from these 2 species by the characteristics of its sclerotized male copulatory organ, particularly in the terminal part of the posterior prostatic reservoir, which is shuttle-shaped, as well as the number of rodlet rows in the squamodisc.

We applied 2 methods of phylogenetic regionalization (evoregions and phyloregions) for the distributions of fleas and their rodent hosts across Mongolia. We investigated the congruence between these 2 regionalization schemes and their alignment with physiographic and ecological subdivisions of Mongolia. We identified evoregions and phyloregions for both fleas and hosts. Ancestral regional distributions were reconstructed, and a phylogenetic correspondence analysis identified key contributing lineages. Using the V-measure, we tested for the congruence between (a) evoregions or phyloregions identified for fleas and evoregions or phyloregions, respectively, identified for their hosts and (b) evoregions and phyloregions identified for either fleas or hosts and each of the physiographic/ecological regionalization schemes of Mongolia. Four evoregions and 8 phyloregions were identified for both fleas and hosts, exhibiting distinct spatial patterns. Host-parasite regionalizations demonstrated moderate spatial similarity (V-measure 0.49–0.50), a significantly higher congruence than previously reported at the larger Palearctic scale (0.33). Flea regionalizations exhibited stronger congruence with environmental schemes than did host regionalizations. We concluded that evoregionalization and phyloregionalization capture distinct evolutionary signals, reflecting the role of in situ diversification vs. phylogenetic turnover resulting from dispersal. Host-parasite co-regionalization is scale-dependent, with increased congruence at regional scales. Despite adult fleas’ obligate host dependence, their regionalization is not merely a passive reflection of host biogeography but is also profoundly shaped by environmental conditions. These findings emphasize the importance of method choice, scale and eco-evolutionary interactions in shaping complex biogeographic patterns.

Chagas disease (CD) is a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi affecting more than 6 million people worldwide. Its treatment is based in old and toxic nitroderivative drugs necessitating for new alternatives. Imatinib (IMB) is a tyrosine kinase inhibitor used in cancer therapy, and previous reports demonstrate that some derivatives are active against T. cruzi justifying further synthesis screening of novel compounds derived from IMB. Our results demonstrate that all test derivatives are highly active against the intracellular forms of T. cruzi being similar or even more potent than the reference drug for CD – benznidazole (BZ). Besides, they were much more active than the parent molecule, displaying low EC90 values (<10 µm) and good selectivity indexes (>10), which are relevant characteristics of a novel hit compound for CD therapy. However, when screened against bloodstream trypomastigotes, only 1 derivative, named PLDC 23/19, was as active (EC50 = 18.8 µm) as BZ (EC50 = 18.8 µm), while the others did not show activity up to 20 µm.

Heartworm disease is a serious acquired parasitic infection caused by Dirofilaria immitis that can cause severe lung manifestation, heart failure, and other organ damage in dogs. We hereby present a case of a seven-year-old, intact male which was submitted to treatment of heartworm disease with doxycycline and a single dose of injectable moxidectin. Three weeks later the dog presented an acute coughing, hemoptysis and marked dyspnea and was admitted to the Hospital Veterinário Popular de Mossoró, a private veterinary hospital located in Mossoró, Rio Grande do Norte, Brazil. Some hours after the admission, the dog showed a severe coughing episodes with progressive expectoration and subsequently profuse bloody discharge. At this time, two live worms were coughed out. The nematodes specimens (1 male and 1 female) were collected from bronchial mucus, and morphologically and molecularly identified as D. immitis. A fragment of 635 bp of the cytochrome oxidase C subunit 1 gene was sequenced and deposited at the GenBank database (Accession number: PV729978). The treatment of heartworm disease can be complex, and the veterinarian must evaluate each case individually to determine the best treatment protocol. Veterinarian practitioners must be aware about the risk of this presentation and intervene properly to keep dogs’ welfare.

Entamoeba bovis is a common intestinal amoeba of ruminants, yet molecularly confirmed data from Europe remain limited. We investigated the occurrence, morphology and genetic variability of E. bovis in Italian domestic and wild ruminants and developed a rapid species-specific polymerase chain reaction (PCR) assay. Faecal samples from calves (n = 45), goats (n = 26), sheep (n = 11) and Italian red deer Cervus elaphus italicus (n = 25) were examined by sediment microscopy and iodine staining. Amoebic stages were detected in 57% of bovine, 61.5% of caprine, 100% of ovine and 56% of red deer samples. Across hosts, cysts were consistently uninucleate and displayed typical E. bovis morphology, including frequent chromatoid bodies and an iodophilic glycogen mass. Representative positives were sequenced at the 18S rRNA locus (∼800 bp), confirming E. bovis (98.6–99.8% identity; 100% query coverage). Maximum-likelihood phylogenetic analysis placed all Italian isolates within the E. bovis clade and indicated a shared lineage across domestic ruminants and red deer, with no segregation by host or ecological setting. A newly designed E. bovis-specific PCR (375 bp) consistently yielded a single amplicon in all sequenced positives, supporting its use for rapid screening without sequencing.

Rattus rattus is a known reservoir of zoonotic pathogens, including Bartonella and Rickettsia, transmitted by ectoparasites such as fleas, mites, lice and ticks. The circulation of Bartonella and Rickettsia in these vectors in Chile remains poorly characterized. To evaluate the association between ectoparasite abundance, prevalence and diversity (including lice, fleas, mites and ticks) and the presence of Bartonella and Rickettsia within ectoparasites collected from R. rattus across different anthropogenic gradients in Chile, a total of 1,339 ectoparasites were collected from 411 R. rattus individuals across 27 localities. Ectoparasites were identified morphologically, and molecular detection of bacteria was performed using conventional and qPCR, targeting multiple genetic markers. Haplotype diversity and phylogenetic relationships were assessed. Bartonella and Rickettsia DNA were detected in fleas, ticks, mites and lice of R. rattus, with prevalence values reported separately for pooled and individually analysed ectoparasites. Bartonella tribocorum, B. rochalimae and B. mastomydis were identified. Rickettsia felis was confirmed in multiple ectoparasite groups. High haplotype diversity was observed in Bartonella but not in Rickettsia. Urbanization and tick prevalence were negatively associated with Bartonella occurrence; flea and tick prevalences were negatively associated with Rickettsia. Rattus rattus and their ectoparasites harbour a diverse range of potentially zoonotic Bartonella and Rickettsia species. These findings highlight the need for integrated surveillance and vector control strategies, especially in areas with variable human-wildlife interaction.

The genus Contracaecum comprises anisakid nematodes with complex life cycles involving aquatic intermediate hosts and piscivorous birds as definitive hosts. The black-crowned night heron (Nycticorax nycticorax) is a widespread ardeid species known to host diverse helminth communities, including Contracaecum spp., although species-level identification is often lacking. In this study, we describe a new species, Contracaecum fioravantii n. sp., based on an integrative morphological and molecular approach. Adult nematodes were collected from 3 N. nycticorax individuals in Israel and examined using light and scanning electron microscopy. The new species is characterized by a distinct combination of morphological features, including robust, subequal spicules, a sagittate tail tip in males, and a specific arrangement of caudal papillae and phasmids, distinguishing it from closely related taxa such as C. microcephalum and members of the C. rudolphii complex. Multivariate morphometric analyses supported its separation from congeners. Molecular characterization based on ITS (Internal Transcribed Spacers) rDNA and cox2 mtDNA sequences revealed high similarity with previously unidentified Contracaecum spp. from ardeid hosts in China, and phylogenetic analyses placed the new species in a well-supported, distinct clade. These findings highlight the hidden diversity within Contracaecum and underscore the importance of combining morphological and molecular data for accurate species delimitation. The identification of C. fioravantii n. sp. contributes to a better understanding of host–parasite relationships in piscivorous birds and suggests a wider geographic distribution linked to migratory pathways of N. nycticorax.