Background/Objectives: Bovine babesiosis is a vector-borne disease transmitted by ticks that causes important losses in livestock worldwide. Recent research performed on the drugs currently used to control bovine babesiosis reported several issues including drug resistance, toxicity impact, and residues in edible tissue, suggesting the need for developing novel effective therapies. The endochin-like quinolones ELQ-316 and buparvaquone (BPQ) act as cytochrome bc1 inhibitors and have been proven to be safe and efficacious against related apicomplexans, such as Plasmodium spp. and Babesia microti, without showing toxicity in mammals. The objectives of this study are investigating whether ELQ-316, BPQ and their combination treatment could be effective against Babesia bovis in an in vitro culture model, and comparing with imidocarb (ID), the routinely used drug. Methods: In vitro cultured parasites at starting 2% percentage of parasitemia (PPE) were treated with BPQ, ELQ-316, ID, and the combinations of BPQ+ ELQ-316 and ID+ ELQ-316 at drug concentrations that ranged from 25 to 1200 nM, during four consecutive days. Parasitemia levels were evaluated daily using microscopic examination. Data was compared using the independent Student's t-test and ANOVA test. Results: All drugs tested, whether used alone or in combination, significantly decreased the survival (p<0.05) of B. bovis in in vitro cultures. The combination of BPQ+ ELQ-316 had the lowest calculated inhibitory concentration 50 (IC50) 31.21 nM (IC95%: 15.06 - 68.48) values, followed by BPQ, 77.06 nM (IC95%: 70.16- 86.01), ID+ELQ316 197 nM (IC95%:129.0 - 311.2), ID 635.1 nM (IC95%: 280.9 – 2119) and ELQ316 654.9 nM (IC95%: 362.3 – 1411). Conclusion: The results reinforce the higher efficacy of BPQ at affecting B. bovis survival, and the potential synergistic effects of its combination with ELQ-316, providing a promising treatment option against B. bovis.

Toxoplasma gondii is a protozoan and the etiologic agent of toxoplasmosis causes high mortality in immunocompromised individuals and newborns. Despite the medical importance of toxoplasmosis, few drugs are available for its treatment, which are associated with side events and parasite resistance. Here, we show a screening of molecules present in Covid-Box as a way of discovering new hits with anti-T. gondii activity. Covid-Box contains 160 molecules with known or predicted activity against SARS-CoV-2. Our analysis selected 23 Covid-Box molecules that can inhibit the tachyzoite forms of the RH strain of T. gondii in vitro by more than 70% at 1 µM after seven days of treatment. The inhibitory curves showed that most of these molecules inhibited the proliferation of tachyzoites with IC50 values below 0.80 µM; Cycloheximide and (-)-Anisomycin were the most active drugs, with IC50 values of 0.02 μM. Cell viability assays showed that the compounds are not toxic at active concentrations, and most are highly selective for parasites. Overall, all 23 compounds were selective, and for three of them (Apilimod, Midostaurin, and Salinomycin), this is the first report of activity against T. gondii. To better understand the effect of the drugs, we analyzed the effect of six of them on the ultrastructure of T. gondii using transmission electron microscopy. The main changes observed in parasite morphology after treatment with the selected drugs were changes in cell division and parasite organelles.

French Guiana, located in the Guiana Shield, is a natural reservoir for many zoonotic pathogens that are of considerable medical or veterinary importance. Until now, there are few data available on the description of parasites circulating in this area, especially on protozoan belonging to the phy-lum Apicomplexa; conversely, the neighbouring countries describe a high parasitic prevalence in animals and humans. Epidemiological surveillance is necessary, as new potentially virulent strains may emerge from these forest ecosystems, such as Amazonian toxoplasmosis. However, there is no standard tool for detecting protozoa in wildlife. In this study, we developed Meat-Borne-Parasite, a high-throughput meta-barcoding workflow for detecting Apicomplexa based on Oxford Nanopore Technologies sequencing platform using the 18S gene of fourteen Apicomplexa-positive samples collected in French Guiana. Sequencing reads were then analysed with MetONTIIME pipeline. Thanks to a scoring rule, we were able to classify as Apicom-plexa-positive 10 samples out of 14 and reveal the presence of co-carriages. The same samples were also sequenced with Illumina platform, for validation purposes. On samples identified as Apicomplexa-positive by both platforms, a strong positive correlation at up to genus level was reported. Overall, the presented workflow represents a reliable method for Apicomplexa detec-tion, which may pave the way for more comprehensive biomonitoring of zoonotic pathogens.

Calcium signaling and lipid metabolism are crucial in the infection processes of Apicomplexans parasites. Thus, enzymes involved in these processes can be drug targets against Apicomplexans. For example, in malaria infection, in-depth research into lipid metabolic pathways is crucial in understanding the parasite's infection cycle, particularly during its erythrocytic infection cycle, which has been demonstrated to be a critical stage during the disease progression. Most enzymes that play critical roles in lipid synthesis and calcium signaling have been extensively studied; nonetheless, a vast knowledge gap still exists, especially on specific enzymes and their roles in the transmission and progression of the Apicomplexan parasites. Many types of infections caused by Apicomplexans are life-threatening and hard to treat. These intracellular parasites proliferate within parasitophorous vacuoles in their host cells. As the parasites multiply, they need to meet their high demand for nutrients such as amino acids and lipids. They can acquire nutrients through scavenging and biosynthesis. This review summarizes a few interesting, unique pathways in selected Apicomplexa and how such unique pathways can be targets for drugs.

Colpodella species are free-living opportunistic pathogens that cause human and animal infections and use ticks and flies as vectors. Trophozoite and cyst stages of Colpodella species can be distinguished from stages of the prey Parabodo caudatus using Sam-Yellowe’s trichrome staining. Colpodella species obtain nutrients by attaching to their prey, aspirating the prey’s cytoplasmic contents into a posterior food vacuole and encysting. It is unclear whether both trophozoite and cyst stages are present during infection. Molecular techniques identified Colpodella species in all reported infections. However, no morphological information was reported to aid life cycle stage identification in hosts. This review discusses the increased incidence of Colpodella infection in animals and in vectors and the need to identify stages used for transmission and pathogenesis. The potential for zoonotic infections through tick and fly bites is a public health concern. We previously used Sam-Yellowe’s trichrome staining to identify life cycle stages of Colpodella sp. In order to gain a better understanding of transmission and pathogenesis, identifying Colpodella life cycle stages in infected tissue and in vectors will provide important insights regarding nutrient uptake in hosts by determining whether attachment of trophozoites to host cells occurs, and identifying trophozoites and cysts in infected hosts.

The colpodellids consist of free-living predatory protists phylogenetically related to pathogenic Apicomplexan parasites such as Plasmodium species, Cryptosporidium sp. and Toxoplasma gondii. Among the colpodellids, Colpodella species prey on bodonids, algae, and ciliates. Voromonas pontica preys on Percolomonas species. In the past decade, Colpodella species have been reported to cause opportunistic infections in humans and animals, and having the potential for zoonotic infections in humans due to the presence of Colpodella species in ticks. In the reported cases, transmission and pathogenic stages of Col-podella were not identified by light microscopy. In the colpodellid V. pontica, cyst stages of both the pred-ator and its prey Percolomonas cosmopolitus have not been identified by light microscopy. In this study we evaluated the dye components used for Sam-Yellowe’s trichrome staining, from different major vendors to determine the consistency and reproducibility of the staining protocol to aid the use of the staining proto-col for diagnosis. We show that although slight variations in the color of the stained cells are obtained, life cycle stages of Colpodella ATCC 50594 could be clearly identified, regardless of the vendor used. For the first time, Sam-Yellowe’s trichrome staining series, could identify cysts of V. pontica and its prey, demonstrating that the staining protocol can identify life cycle stages of other colpodellids. Sam-Yellowe's trichrome staining will aid molecular diagnosis of infections caused by colpodellids in human and ani-mals, identify colpodellids in ticks and flies and from environmental samples, when used for staining.