Several bee parasites are transmitted through flowers, and some of them can infect multiple host species. Given the shared use of flowers by bee species, parasites can potentially encounter multiple host species, which could affect the evolution of parasite virulence. We used the trypanosomatid parasite Crithidia bombi and its host, the common eastern bumble bee (Bombus impatiens), to explore the effect of infecting an alternative host, the alfalfa leaf-cutter bee (Megachile rotundata), on parasite infectivity and ability to replicate. We conducted a serial passage experiment on primary and alternative hosts, assessing infectivity and intensity of infection during five passes. Parasite cells from each pass through the alternative host were also used to infect a group of primary hosts. We found that serial passes through the alternative host increased infectivity, but there was no effect on intensity of infection. Interestingly, both the probability and intensity of infection on the primary host increased after serial passage through the alternative host. This increase in intensity of infection could be due to maladaptation after selection of new C. bombi strains has occurred in the alternative host. This study suggests that host switching has the potential to affect the adaptation of bee parasites to their hosts.

Lyme disease, a tick-borne illness caused by Borrelia spirochetes, poses a significant threat to public health. While acaricides effectively control ticks on pets and livestock, their impact on pathogen transmission is often unclear. This study investigated the acaricidal efficacy of fipronil against Ixodes ricinus ticks and its potential to block Borrelia afzelii transmission. Initially, we employed the ex vivo membrane blood-feeding system to assess the dose–response acaricidal activity of ivermectin, fipronil and its metabolite fipronil sulfone, when supplemented in the blood meal throughout tick feeding. To obtain the temporal resolution of their acaricidal activity, ticks were allowed to initiate blood feeding on an artificial membrane before being exposed to a 1-time topical application of these acaricides. Fipronil demonstrated superior speed of acaricidal activity, with onset of tick moribundity within a few hours, prompting its selection for further in vivo testing with Borrelia-infected ticks. The I. ricinus nymphs infected with B. afzelii were topically treated with fipronil shortly after attachment to mice. Four weeks post-feeding, the skin and internal organs were examined for the presence of Borrelia. No spirochetes were detected in any organ of mice exposed to fipronil-treated ticks, while 9 out of 10 control mice, exposed to non-treated infectious ticks, displayed Borrelia infection. The in vitro co-culture experiments confirmed that fipronil had no direct effect on Borrelia viability, indicating a tick-directed effect. Overall, these results underline the potential of fipronil as a valuable tool for tick control strategies and suggest a concept for acaricide-mediated Borrelia-transmission blockers.

Bovines are important reservoir hosts of schistosomiasis, placing humans and animals in rice fields areas at risk of infection. This study reported the prevailing infection of zoonotic parasites from bovine feces in the rice fields adjacent to Lake Mainit, Philippines. Formalin Ethyl Acetate Sedimentation was performed on 124 bovine fecal samples from rice fields and documented eggs and cysts from seven parasites: Schistosoma japonicum, Fasciola gigantica, Ascaris sp., Strongyloides sp., Balantidium coli, coccidian oocyst and a hookworm species. Among these parasites, F. gigantica harboured the highest infection with a 100% prevalence rate, followed by hookworms (51.61%), B. coli (30.64%) and S. japonicum (12.09%), respectively. The intensity of infection of S. japonicum eggs per gram (MPEG = 4.19) among bovines is categorized as ‘light.’ Bovine contamination index (BCI) calculations revealed that, on average, infected bovines in rice fields excrete 104 750 S. japonicum eggs daily. However, across all ricefield stations, bovines were heavily infected with fascioliasis with BCI at 162 700 F. gigantica eggs per day. The study reports that apart from the persistent cases of schistosomiasis in the area, bovines in these rice fields are also heavily infected with fascioliasis. The study confirms the critical role of bovines as a reservoir host for continued infection of schistosomiasis, fascioliasis and other diseases in the rice fields of Lake Mainit. Immediate intervention to manage the spread of these diseases in bovines is recommended.

Leishmaniases affect 12 million people worldwide. They are caused by Leishmania spp., protozoan parasites transmitted to mammals by female phlebotomine flies. During the life cycle, promastigote forms of the parasite live in the gut of infected sandflies and convert into amastigotes inside the vertebrate macrophages. The parasite evades macrophage's microbicidal responses due to virulence factors that affect parasite phagocytosis, survival and/or proliferation. The interaction between Leishmania and macrophage molecules is essential to phagocytosis and parasite survival. Proteins containing leucine-rich repeats (LRRs) are common in several organisms, and these motifs are usually involved in protein–protein interactions. We have identified the LRR17 gene, which encodes a protein with 6 LRR domains, in the genomes of several Leishmania species. We show here that promastigotes of Leishmania (L.) amazonensis overexpressing LaLRR17 are more infective in vitro. We produced recombinant LaLRR17 protein and identified macrophage 78 kDa glucose-regulated protein (GRP78) as a ligand for LaLRR17 employing affinity chromatography followed by mass spectrometry. We showed that GRP78 binds to LaLRR17 and that its blocking precludes the increase of infection conferred by LaLRR17. Our results are the first to report LRR17 gene and protein, and we hope they stimulate further studies on how this protein increases phagocytosis of Leishmania.

As a member of the Scathophagidae family, Scathophaga stercoraria (S. stercoraria) is widely distributed globally and is closely associated with animal feces. It is also a species of great interest to many scientific studies. However, its phylogenetic relationships are poorly understood. In this study, S. stercoraria was found in plateau pikas for the first time. The potential cause of its presence in the plateau pikas was discussed and it was speculated that the presence of S. stercoraria was related to the yak feces. In addition, 2 nuclear genes (18SrDNA and 28SrDNA), 1 mitochondrial gene (COI), and the complete mitochondrial genome of S. stercoraria were sequenced. Phylogenetic trees constructed based on 13 Protein coding genes (13PCGs), 18S and 28S rDNA showed that S. stercoraria is closely related to the Calliphoridae family; phylogenetic results based on COI suggest that within the family Scathophagidae, S. stercoraria is more closely related to the genus Leptopa, Micropselapha, Parallelomma and Americina. Divergence times estimated using the COI gene suggest that the divergence formation of the genus Scathophaga is closely related to changes in biogeographic scenarios and potentially driven by a combination of uplift of the Qinghai-Tibetan Plateau (QTP) and dramatic climate changes. These results provide valuable information for further studies on the phylogeny and differentiation of the Scathophaga genus in the future.

Within the family Adeleidae, Adelina spp. belong to a group of arthropod pathogens. These parasites have been reported to have a wide geographic distribution, however, there are no reports of these protists in the Canary Islands, Spain. One of the peculiarities of the life cycle of Adelina spp. is the participation of a predator, because fecundation and sporulation occur inside the body cavity, and so necessitate destruction of the definitive host. The involvement therefore of a ‘dispersion host’, which eats the definitive host and spreads the oocysts through its faeces, is critical for the maintenance of certain Adelina spp. On the island of Gran Canaria, adeleid oocysts have been found in stool samples from four animals, three California kingsnakes (Lampropeltis californiae), and one feral cat. These animals were part of a larger coprological study of vertebrate parasites (117 snakes, 298 cats), where pseudoparasitic elements were also recorded. L. californiae and feral cats are invasive species which are widespread across the island and this novel finding of Adelina spp. oocysts in their faeces suggests that they could also serve as potential sentinel species for arthropod parasites.

Taenia solium is the aetiological agent of cysticercosis, a zoonosis that causes severe health and economic losses across Latin America, Africa and Asia. The most serious manifestation of the disease is neurocysticercosis, which occurs when the larval stage (cysticercus) establishes in the central nervous system. Using Taenia crassiceps as an experimental model organism for the study of cysticercosis, we aimed to identify the in vitro conditions necessary to allow parasite development at the short- and long terms. First, cysticerci were incubated for 15 days in different media and parasite densities. The number of buddings and cysticerci diameter were measured to evaluate asexual multiplication and parasite growth, respectively. Vitality was determined by trypan blue staining and morphology analysis. As a result, high cysticerci density and medium containing FBS and the excretion/secretion (E/S) products of feeder cells induced parasite survival, growth and multiplication. Then, the long-term (5 weeks) incubation of the parasites in co-culture with feeder cells was evaluated. Consequently, the mammalian cell lines induced a significant increase in total parasite volume while axenic cultures did not show any statistically significant change over time. In this study, the proper conditions to maintain T. crassiceps in vitro are described for the first time in a simpler and more controlled setting other than experimental infections. In addition, it was shown that cysticerci growth, survival and asexual multiplication depend on a complex network of secreted factors from both parasite and host.