This review article summarizes the history of amoebic dysentery (entamoebiasis) caused by Entamoeba histolytica. Initially, Entamoeba species were thought to be the most primitive extant eukaryotes, but more recent research revealed that they emerged relatively late in evolutionary history. Paleoparasitological data suggest that E. histolytica has been a parasite of humans since ancient times and was probably spread throughout the world by man during early human migration. By the end of the 19th century, it was established that E. histolytica was the etiological agent of amoebic dysentery and liver abscess. The issue over pathogenic and non-pathogenic strains of E. histolytica was resolved in the 1980s by the discovery of the morphologically indistinguishable harmless sister species Entamoeba dispar. Being mainly a disease of tropical and subtropical low-income countries, entamoebiasis cases have increased among travellers and immigrants arriving from endemic regions in recent years.

Sulfadoxine-pyrimethamine (SP) is the standard of care for Plasmodium falciparum malaria chemoprevention among pregnant women, infants and children. Developing alternative chemoprevention products and other prevention products, such as vaccines and monoclonal antibodies, requires significant investment. However, knowledge gaps surrounding the activity of SP and resistance put these investments at risk. Therefore, we reviewed SP’s combined antimalarial action, including the individual antiplasmodial components, other antimicrobial effects, impact on malaria immunity development and continued effectiveness in settings with high SP resistance. We created a roadmap of non-clinical and clinical evidence to better understand the effectiveness of SP for chemoprevention and inform the development of new prevention tools.

Spirometra is a genus of zoonotic cestodes with an ambiguous species-level taxonomic history. Previously, Spirometra mansonoides was considered the only species present in North America. However, recent molecular data revealed the presence of at least three distinct species in the USA: Spirometra sp. 2 and 3, and Spirometra mansoni. This study aimed to elucidate the diversity and potential host associations of Spirometra species among companion animals in the USA. Samples (N = 302) were examined from at least 13 host species, including mammals, amphibians and reptiles. Sample types included eggs isolated from faeces (n = 222), adult specimens (n = 71) and plerocercoids (n = 9) from 18 different states and 2 territories across the USA. Extracted genomic DNA was subjected to PCR targeting a fragment of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene. Generated sequences (n = 136) were included in a phylogenetic analysis. Spirometra mansoni was detected in domestic cats (n = 76), dogs (n = 12), a White’s tree frog (n = 1), a Cuban knight anole (n = 1), a green iguana (n = 1) and a serval (n = 1) across 15 states and Puerto Rico. Spirometra sp. 2 was found only in dogs (n = 3) from Florida and Spirometra sp. 3 was found only in cats (n = 41) from 17 states. All plerocercoid samples were consistent with S. mansoni. The results confirm that at least three distinct Spirometra species are present and established in companion animals, such as dogs and cats, and likely are using various native and exotic species as paratenic hosts within the USA.

There is growing interest in using avermectins in livestock as a vector control tool for mosquitoes involved in the transmission of human malaria in sub-Saharan Africa (SSA). If implemented, the potential health and productivity impacts across the livestock sector would need to be considered, as avermectins are already commonly used in veterinary medicine to treat gastrointestinal helminths and parasitic insects. Here we present the results of a restricted systematic review that summarizes what is known about the effects of avermectins on cattle and swine productivity in SSA and the presence of avermectin resistance in endo- and ectoparasites of importance in these species. A total of 583 unique journal articles were identified using key search terms in 3 databases: Agriculture, Life, and Natural Sciences Databases from ProQuest, CAB Abstracts and Scopus. Ten articles met the criteria for inclusion on impacts on productivity and 4 met the inclusion criteria related to avermectin resistance. All studies documenting impacts of avermectins on productivity were performed using ivermectin in cattle. Generally, these showed a positive significant effect on growth rates. Resistance to avermectins was documented in 2 of the 4 included articles. Considering the extensive literature documenting resistance to avermectins in other areas of the world, our findings may reflect a paucity of studies on the subject in SSA. The authors conclude that additional research is needed to quantify the potential benefits and challenges to the livestock sector of using avermectins for malaria control across different production systems, and in a variety of ecological settings.

Scabies is a neglected tropical disease caused by the ectoparasitic mite, Sarcoptes scabiei var. hominis (S. scabiei). Common scabies, the most prevalent clinical subtype of scabies, is characterized by pruritus, multiple skin lesions and low mite burden. In contrast, crusted scabies, an extremely contagious variant, is characterized by hyperkeratosis and high mite burden, with or without pruritus. Scabies can be diagnosed based on clinical manifestations, with confirmation obtained through microscopic identification of diagnostic features of S. scabiei. However, owing to the diversity and non-specific nature of its clinical manifestations and insufficient knowledge regarding early-stage clinical manifestations, the diagnosis of crusted scabies continues to be delayed. Herein, we present three cases of scabies with varying degrees of crusting and mite burden. Three patients with physical and microscopic results suggesting scabies were selected for this study. Case 1 had mild crusting and low mite burden, case 2 had severe crusting and high mite burden and case 3 had mild crusting and high mite burden. In this case report, ‘the initial stage of crusted scabies’ refers to the progression from common to crusted scabies. The discussion regarding the diagnostic characteristics of the initial stage of crusted scabies is expected to aid the early diagnosis of crusted scabies.

Avian trypanosomes (Trypanosoma, Kinetoplastea) are successful blood parasites occurring worldwide. These parasites are usually non-pathogenic to their avian hosts, thus neglected in studies regarding their life cycles and vectors. Several families of blood-sucking dipteran insects, including mosquitoes, have been identified as vectors of avian trypanosomes. Mosquitoes have been experimentally confirmed as vectors of Trypanosoma culicavium and Trypanosoma thomasbancrofti. In this study, we describe a third species of avian trypanosomes occurring in mosquitoes, designated as Trypanosoma tertium n. sp. This species can be distinguished from related trypanosome species based on morphology and small subunit rRNA gene sequence. Two isolates of T. tertium n. sp. obtained from a mosquito and a bird host were able to infect two subspecies of laboratory Culex pipiens mosquitoes, with infection rates reaching 60% and heavy infections in 90% of positive females. In infected mosquitoes, trypanosomes occurred as long epimastigotes in the midgut and short epimastigotes and rosettes in the hindgut. Putative infectious stages were detected in the diuretic liquid of infected mosquitoes, suggesting, besides transmission through ingestion of the infected vector, a possible transconjunctival infection. Among wild mosquitoes, avian trypanosomes were detected exclusively in Cx. pipiens with 3.3% total prevalence, while T. tertium n. sp. prevalence was only 0.08% among 1128 dissected Cx. pipiens individuals. In birds, T. tertium n. sp. was detected in 8 species within which the prevalence was 1.3% (686 birds), while it was 0.3% in total (3084 birds). We discuss the relationship of the newly described T. tertium n. sp. with other mosquito-transmitted trypanosomes.

Helminth infection is highly prevalent in indigenous chickens reared in semi-scavenging/ scavenging systems in Bangladesh. Here, we estimated the prevalence of gizzard worm infection in indigenous chickens, the detection of the worm-induced pathologies, the development of ex vivo cultural protocol, and anthelmintic efficacy. We randomly collected and examined 390 chickens and isolated worms from the gizzard and proventriculus. The isolated worms were identified as Cheilospirura hamulosa Diesing, 1861. The overall prevalence of C. hamulosa was 33.1% (129 out of 390). Prevalence of the worm was almost similar in both sexes but significantly (p <0.05) higher in adult chickens (44.3%) and in the summer season (47.1%). In heavy infections, C. hamulosa destroyed the muscular layer of the gizzard. The presence of brown necrotic tissues and curd-like caseous materials was detected in the affected gizzards. In severe cases, the horny lining of the gizzard was inflamed, necrotized and marked by multiple holes and brick-red colored spots. Liquefied, fetid materials oozed out from the muscular layer in extensive cases. Histopathological examination showed marked infiltrations of eosinophils. In serum-supplemented M199 and DMEM, adult C. hamulosa survived well and reproduced. Levamisole (LEV) and ivermectin (IVM) efficiently killed the worm. However, albendazole (ABZ), mebendazole (MBZ) and piperazine (PPZ) did not kill the worms. Our results suggest that C. hamulosa is highly prevalent in semi-scavenging chickens in Bangladesh. LEV and IVM can be used to treat and control the infection in chickens.

Brazil has the richest biodiversity of Ergasilidae on Earth, with 76 species in 19 genera. However, several authors suggested that there is still great potential for discoveries, especially regarding genetic data that are still scarce for ergasilids from this region. To expand our knowledge of this taxon, we conducted an integrative study involving morphological (light and scanning electron microscopy) and molecular analyses of ergasilids from fishes sampled in the Pardo River, São Paulo State, Brazil. Two ergasilid species were found, Gamispatulus schizodontis and Rhinergasilus piranhus parasitizing the nostrils of 5 fish species (native and exotic): (i) R. piranhus from Astyanax lacustris; Cyphocharax modestus; Coptodon rendalli; Psalidodon bockmanni; and (ii) G. schizodontis from Serrasalmus maculatus. Additionally, we redescribed R. piranhus herein based on novelties and discrepancies found in the antennules, antennae, body segments and ornamentation of the swimming legs. Novel molecular data of ribosomal (18S and 28S rDNA) and/or mitochondrial (cox 1) genes were provided for both species and the phylogenetic relationships among the ergasilids were tested. Relationships between species/genera are still uncertain in Ergasilidae, but it was possible to verify the formation of 5 well-supported terminal clades – i.e. including a clade formed only by Neotropical species. More molecular data are needed to test this hypothesis, but the clades observed here represent good targets for future taxonomic revisions. The occurrence of R. piranhus specimens in the introduced fish, Co. rendalli can indicate (for the first time) host switching in this parasite species and spillback from native to introduced hosts.

Marine parasites remain understudied in South Africa with little information available on their diversity and the effects these parasites may have on their hosts. This is especially true for parasitic copepods within the family Ergasilidae. Among the 4 genera known in Africa, Ergasilus Nordmann, 1832 is the most speciose with 19 reported species. However, this represents only 12% (19/163) of the global diversity. Furthermore, only 5 known African species are reported from marine environments, and only 1 is reported from the South African coastline. Given the rich biodiversity along this coastline, a high marine parasite diversity could be expected from these shores. As a case study, the Evileye blaasop, Amblyrhynchote honckenii (Bloch), a marine and brackish fish species, was screened for parasites along the South African coastline. This resulted in the discovery of 2 species of Ergasilus new to science (Ergasilus arenalbus n. sp. and Ergasilus chintensis n. sp.), which makes them the second and third ergasilid species reported for tetraodontid pufferfishes worldwide. Although genetically distinct, the 2 newly described species clustered in the same subclade within the Ergasilidae based on 18S rDNA, 28S rDNA and COI mtDNA phylogenies. The newly described species differ morphologically from each other, and their respective congeners based on the size and armature of the antenna; body segmentation; and general ornamentation throughout the entire body. The addition of these 2 new species from a single host species indicates that South Africa's marine fishes contain most probably a hidden parasitic copepod diversity that is worth exploring.

Aplectana membranosa is a cosmocercid nematode that shows affinity with various amphibian and reptile hosts, being considered a generalist species. To date, no studies have investigated the influence of host and locality in the morphological variation of this species. Thus, we analysed morphological and morphometric characters of 260 specimens of A. membranosa collected from 9 host species and 7 different localities. To complement the metric studies, we conducted phylogenetic analyses using the ribosomal genes 28S and internal transcript spacer 1 (ITS1) to determine the phylogenetic position of the species and its divergence. In the present study, it was possible to observe the cloacal papillae pattern of the species through scanning electron microscopy, and we found no morphological variation in the specimens of A. membranosa from various hosts in different localities in Brazil. The study showed low variation in all data. However, despite the low variation, we found that external environmental conditions, such as climate and latitude, influence its variation. Molecular analyses highlighted that the separation of Cosmocercidae members may be related to geographic distribution and population genetic divergence. Thus, the results illustrated in this study reiterate the importance of using integrative data to better elucidate the family’s taxonomic and evolutionary history.

Toxoplasma gondii non-archetypal strains have distinct virulence profiles and immunological activation in the host when compared with archetypal strains. The present work aims to perform an analysis of the inflammatory profile during acute and early chronic infection by T. gondii atypical strain in an experimental murine model. After euthanasia, blood was collected for the quantification of specific IgG antibodies and their subtypes (IgG1/IgG3) by ELISA; bronchoalveolar lavage (BAL) was realized and immunophenotyping of lymphocytes population was performed at 12- and 30-days post infection (dpi); the levels of IFN-γ, IL-12, IL-10, TNF-α, IL-6, IL-17, nitric oxide and total proteins were determined in the BAL supernatant. Tissue cyst burden was determined in the brain homogenate, and the parasite load in the lungs was assessed by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Infection with the CK4 strain induced a lower brain cyst load similar parasite burden in the lungs, and higher levels of IgG1 and IgG3, when compared to ME49. The group infected with the CK4 strain presented higher levels of systemic IFN-γ, and both infected groups displayed similarly elevated levels of systemic TNF-α, IL-6 and IL-17 at 30 dpi, as well as higher numbers of CD4+ and CD8+ T lymphocytes in the acute stage of infection, followed by higher numbers of central and effector CD4+ T cells. IFN-γ levels in the BAL fluid were significantly higher in animals infected with the CK4 strain in both the acute and early chronic stage of infection, highlighting the involvement of the lung environment.

Haemosporidians constitute a monophyletic group of vector-borne parasites that infect a wide range of vertebrate hosts, including Neotropical lizards. The remarkable diversity of these host-parasite associations and inadequate research on certain parasite groups have resulted in controversial haemosporidian taxonomy. Herein, we rediscover erythrocytic and non-erythrocytic haemosporidians infecting golden tegus (Tupinambis teguixin) from Brazil and Colombia. The erythrocyte-inhabiting parasite belongs to Plasmodium sp., and the non-erythrocytic form was identified as Saurocytozoon tupinambi, previously attributed to the Family Leucocytozoidae. These non-pigmented haemosporidian parasites do not multiply in the blood. The relationships between the Saurocytozoon and Leucocytozoidae species were discussed for many years, especially during the 1970s. However, cytochrome b (cytb) sequences and the mitochondrial genomes recovered for this species strongly support classifying this parasite as a Plasmodium taxon. Therefore, we proposed a new combination for this parasite, Plasmodium (Saurocytozoon) tupinambi comb. nov., where Saurocytozoon is retained as a subgenus due to its distinct morphology. These results reinforce that a broader definition of Plasmodiidae must include saurian parasites that develop non-pigmented leucocytozoid-like gametocytes.

This study investigated the prevalence and genetic diversity of Hydatigera parva in 341 native rodents in a riparian habitat in the Mediterranean part of Spain. Polycephalic larvae were found in 32% of wood mice (Apodemus sylvaticus; n = 84) and 0.4% of Algerian mice (Mus spretus; n = 257) examined, with a significantly higher prevalence in the former. No significant differences in infection prevalence in wood mouse were found between sex and age groups, habitats (agricultural vs natural) or seasons. Genetic analysis of 25 cysts using cox1 sequences revealed low nucleotide (0.00110) and haplotype diversity (0.380), suggesting limited genetic variation. Phylogenetic analysis showed that the studied H. parva isolates were genetically distinct from other species within the genus Hydatigera. The results indicate a lower genetic diversity in European than in African populations, supporting the hypothesis that H. parva was introduced to Europe from Africa, possibly with its final host, the common genet (Genetta genetta), an abundant predator in the study area. This study is the first population genetic study of H. parva in the Iberian Peninsula. It provides insights into the population structure of the parasite and its interaction with rodent hosts, and thereby constitutes an example of the potential identification of an introduction route of a parasite with its definitive host. It also confirms the importance of the wood mouse as an intermediate host for the maintenance of the parasite’s life cycle in Europe and forms the basis for further studies on the distribution and genetic diversity of H. parva.

It is often postulated that natural systems are expected to suffer an increasing risk of infectious disease outbreaks as climate change accelerates. In the northern Argentine Sea, the rise of ocean temperature has produced a tropicalization of demersal megafauna since 2013. This rapidly warming hotspot provides an excellent model to test whether fish parasites have increased, declined, or remained stable in the region. Cardiocephaloides physalis a parasite of penguins Spheniscus magellanicus as adult and suspected to parasitize anchovies Engraulis anchoita as larvae is here used to compare their occurrence and abundance between samples composed by 1752 fish of variable age caught at different latitudes during 1993–1995 and 2022 and between 20 juvenile birds and literature data. In the present work, the identity of metacercariae as C. physalis is confirmed genetically, as well as a net decline of population parameters of the parasite to its effective disappearance in anchovies from northern areas and to extremely low levels in fish from southern regions and penguins. After analysing possible causes for such changes in a scenario of rapid regional tropicalization, a direct effect of increasing temperature on parasites arose as the main causal candidate for the observed decline in their populations over the last decades. Beyond the biological and ecological consequences of global change on them, parasites offer excellent systems for measuring and monitoring such effects. The almost local extinction of C. physalis in a marine hotspot of global warming seems to be one of the first examples of such processes.

Transposable elements (TEs) have the ability to move and amplify inside the host genome, making them a pivotal source of genome plasticity. Presently, only 4 TE clades (all classified as Class I retrotransposons) have been identified in trypanosomatids. We predicted repeat content and manually curated TEs across the genomes of 57 trypanosomatids, shedding light on their proportions, diversity and dynamics. Our analysis yielded 214 TE consensus sequence models across the dataset, with abundance ranging from 0.1% to 7.2%. We found evidence of recent transposon activity in most species, with notable bursts in the Vickermania, Lafontella, Porcisia and Angomonas spp., along with Leishmania (Mundinia) chancei, L. (M.) orientalis and L. (M.) procaviensis. We confirmed that the 4 TE clades have colonized virtually all lineages of trypanosomatids, potentially playing a role in shaping their genome architecture. The effort of this work culminated in the establishment of the Trypanosomatid TE Database 1.0, a resource designed to standardize the TE annotation process that can serve as a foundation for future studies on trypanosomatid TEs.