Current research in parasitology & vector-borne diseases最新文献

Rats, being synanthropic, are hosts to agents of zoonotic diseases that pose a threat to human and domestic animal health. The nematode parasite Angiostrongylus cantonensis, commonly known as the rat lungworm, is no exception; it can cause potentially fatal neural disease in humans, dogs and other species. The distribution of A. cantonensis (haplotypes SYD.1 and Ac13) and its close relative, Angiostrongylus mackerrasae is not well understood in Australia. We investigated the prevalence of Angiostrongylus in rats in Sydney, Australia, primarily via faecal qPCR, and identified the species and haplotypes using partial cox1 sequencing. We found a moderate prevalence of infection (29%; 95% CI: 16.1–46.6%) in black (Rattus rattus) and brown (Rattus norvegicus) rats around public parks and residential areas. This study demonstrates that Sydney’s urban rat population is a reservoir for A. cantonensis. Modelling infection status as a function of rat species, sex, tibia length (as a proxy for age), and health index (a measure of weight by size) revealed that older rats are statistically more likely to be infected (χ²₁ = 5.331, P = 0.021). We observed a dominant presence of the A. cantonensis SYD.1 haplotype, for which the implications are not yet known. No A. mackerassae was detected, leading us to suspect it may have a more restricted host- and geographical range. Overall, this study illustrates the presence and potential risk of A. cantonensis infection in Sydney. Public education regarding transmission routes and preventative measures is crucial to safeguard human and animal health.

The brown dog tick, Rhipicephalus linnaei (Audouin, 1826), is distributed across the American continent and is formerly known as the “tropical lineage”. It belongs to the Rhipicephalus sanguineus (Latreille, 1806) species complex, referred to as R. sanguineus (sensu lato). Mitochondrial genome sequences are frequently used for the identification and represent reference material for field studies. In the present study, the entire mitochondrial genomes of R. linnaei (∼15 kb) collected from dogs in Mexico were sequenced and compared with available mitogenomes of R. sanguineus (s.l.). The mitochondrial genome is ∼90% identical to the reference genome of R. sanguineus (sensu stricto, former “temperate lineage”) and > 99% identical to R. linnaei mitogenome derived from the neotype. Two additional mitogenomes were obtained and described as R. linnaei and R. turanicus from dogs in Saudi Arabia. The present study delivers a molecular reference for R. linnaei from America and complements R. linnaei mitogenomes from Africa, Asia and Australia. We propose to consider the complete mitogenome, as the reference for American R. linnaei, even when partial mitochondrial cox1, 12S rRNA or 16S rRNA genes are characterised.

Although bats (Mammalia: Chiroptera) act as natural reservoirs for many zoonotic pathogens around the world, few studies have investigated the occurrence of Anaplasmataceae agents in bats, especially vampire bats. The family Anaplasmataceae (order Rickettsiales) encompasses obligate intracellular bacteria of the genera Anaplasma, Ehrlichia, Neorickettsia, Neoehrlichia, Wolbachia, and Allocryptoplasma. The present study aimed to investigate, using molecular techniques, the presence of species of Anaplasma, Ehrlichia, and Neorickettsia in vampire bats sampled in northern Brazil. Between 2017 and 2019, spleen samples were collected from vampire bats belonging to two species, Desmodus rotundus (n = 228) from the states of Pará (n = 207), Amazonas (n = 1), Roraima (n = 18) and Amapá (n = 3), and Diaemus youngii (n = 1) from Pará. Positivity rates of 5.2% (12/229), 3% (7/229), and 10.9% (25/229) were found in PCR assays for Anaplasma spp. (16S rRNA gene), Ehrlichia spp. (dsb gene) and Neorickettsia spp. (16S rRNA gene), respectively. The present study revealed, for the first time, the occurrence of Anaplasma spp. and different genotypes of Ehrlichia spp. in vampire bats from Brazil. While phylogenetic analyses based on the dsb and ftsZ genes of Ehrlichia and 16S rRNA of Anaplasma spp. revealed phylogenetic proximity of the genotypes detected in vampire bats with Anaplasmataceae agents associated with domestic ruminants, phylogenetic inferences based on the gltA and groEL genes evidenced the occurrence of genotypes apparently exclusive to bats. Neorickettsia sp. phylogenetically associated with N. risticii was also detected in vampire bats sampled in northern Brazil.

The ornate dog tick Dermacentor reticulatus, vector of Babesia canis, has shown a considerable range expansion in several European countries. Previously, only few areas in Germany were recognised as endemic for B. canis, but a marked increase in autochthonous canine babesiosis cases and spread to new areas has been noted recently. To better assess the current risk for dogs, the present study screened 5913 specimens of D. reticulatus from all over Germany, collected in the frame of a Citizen Science study during 2019–2023. Moreover, 343 Dermacentor marginatus ticks were also included. Babesia detection was achieved by quantitative real-time PCR (qPCR). Positive samples were confirmed by sequencing. Moreover, a MGB-probe-based triplex qPCR was established to detect and distinguish between the canine Babesia spp. relevant in Europe, i.e. B. canis, Babesia vogeli and Babesia gibsoni. Overall, B. canis DNA was detected in five D. reticulatus specimens (0.08%). Two of the B. canis-positive ticks originated from areas previously known as endemic for canine babesiosis, namely from the area of Freiburg im Breisgau, federal state of Baden-Wuerttemberg, and from the district St. Wendel, federal state of Saarland. Three further B. canis-positive ticks were detected in districts not yet recognised as endemic, one each in the district of Mansfeld-Suedharz, federal state of Saxony-Anhalt, the district of Ravensburg, federal state of Baden-Wuerttemberg and in the city of Fürth, federal state of Bavaria. However, the tick in Fürth was found on a dog who had returned from a trip to the Breisgau region on the previous day, indicating translocation of the specimen out of this well-known endemic focus. The geographical distribution of the positive samples shows that B. canis is currently spreading in Germany, particularly via dogs travelling within the country, increasing the infection risk throughout the country. Important measures to contain a further spread of the pathogen include comprehensive year-round tick prophylaxis with licensed acaricides, not only to protect the individual pet, but also the entire dog population. Moreover, screening of dogs entering Germany from B. canis-endemic countries is required and any treatment should aim at pathogen elimination by use of appropriate imidocarb dosages.

Black gobies (Gobius niger) from the Finnish Archipelago, Baltic Sea, were screened for helminth infections in summer 2020. Helminths were identified morphologically and/or molecularly. Altogether 26 novel sequences were generated and analysed using maximum likelihood estimation. Morphological and phylogenetic analyses based on mitochondrial genes revealed the presence of 8 species belonging to the Digenea (Diplostomum mergi Lineage 3), Cestoda (Bothriocephalus scorpii), Nematoda (Contracaecum rudolphii A, Cucullanus sp. and Hysterothylacium aduncum), and Acanthocephala (a putative new species of Corynosoma, Corynosoma semerme and Neoechinorhynchus sp.). Phylogenetic and comparative sequence analyses revealed that the putative new acanthocephalan species is closely related to C. neostrumosum described from the Caspian seal, Pusa caspica, in the Caspian Sea. The black goby represents a new host record for four parasite species (Diplostomum mergi Lineage 3, Contracaecum rudolphii A, Corynosoma semerme and Corynosoma sp.). The Finnish Archipelago is a novel locality record for three species (Corynosoma sp., Diplostomum mergi Lineage 3 and Bothriocephalus scorpii).

The saddled seabream, Oblada melanura (L.), is a common seawater species present in the Mediterranean. Between July and August 2023, during diving activities along the Sicilian coast of Italy, we recorded with a digital camera several specimens of O. melanura showing an abnormal pattern of swimming in the water column. The unusual swimming behaviour was characterized by fast, uncoordinated directional changes and isolation from the remaining fishes in the shoal. Four dead fish were found and collected for necropsy and parasitological evaluation/examination. Upon gross examination, all fish showed an evident coelomic distension; the coelomic cavity of two fish was filled with nematodes that dislocated the coelomic organs, and the other two had degraded nematodes and a conspicuous quantity of fluid in the coelomic cavity. All collected parasites were identified as Philometra obladae (Nematoda: Philometridae) according to morphological criteria. Here, we describe the unusual swimming behaviour of O. melanura naturally infected with Ph. obladae and the results of the examination of dead fish infected with this parasite. Future studies are needed to better evaluate and describe the dynamics and the epidemiology of Ph. obladae infection in wild O. melanura.

Most organisms have developed circadian clocks to adapt to 24-hour cycles in the environment. These clocks have become crucial for modulating and synchronizing complex behavioral and biological processes. A number of parasites seem to have evolved to take advantage of their hosts’ circadian rhythms to favor their own infection and survival. Some species, such as Microphallus sp. and Trypanosoma cruzi, can alter the patterns of locomotor behavior of infected intermediate hosts, which can promote transmission to a subsequent primary host. Some fungi of the genera Ophiocordyceps and Entomophthora, as well as hairworms (Nematomorpha), elicit complex behaviors that promote their host’s death at a time and place that optimizes continuation of the parasite’s life-cycle. At least in some cases, a proposed mechanism might involve a change in the expression of clock-controlled genes. Lastly, some disease-causing protozoan parasites of the genera Trypanosoma, Plasmodium, and Leishmania induce changes in the circadian rhythms of their primary hosts upon infection. Some of these changes may be attributed to circadian alterations resulting from the host’s inflammatory response to the infection or other unexplored responses or adaptations to the illness. Thus, a distinction must be made between manipulation of the parasite and response of the host when studying these alterations in the future. Parasitic manipulation of circadian rhythms, which vastly modulates behavior and physiology, is an essential issue that has been relatively understudied. A deeper understanding of this phenomenon could lead to the development of novel therapeutic approaches for the diseases that these parasites convey.