Background: Apoptosis is fundamental in maintaining cell balance in multicellular organisms, and caspases play a crucial role in apoptosis pathways. It is reported that apoptosis plays an important role in tick salivary gland degeneration. Several different caspases have been found in ticks, but the interactions between them are currently unknown. Here, we report three new caspases, isolated from the salivary glands of the tick Rhipicephalus haemaphysaloides. Methods: The full-length cDNA of the RhCaspases 7, 8 and 9 genes were obtained by transcriptome, and RhCaspases 7, 8 and 9 were expressed in E. coli; after protein purification and immunization in mice, specific polyclonal antibodies (PcAb) were created in response to the recombinant protein. Reverse-transcription quantitative PCR (RT-qPCR) and western blot were used to detect the existence of RhCaspases 7, 8 and 9 in ticks. TUNEL assays were used to determine the apoptosis level in salivary glands at different feeding times after gene silencing. The interaction between RhCaspases 7, 8 and 9 were identified by co-transfection assays. Results: The transcription of apoptosis-related genes in R. haemaphysaloides salivary glands increased significantly after tick engorgement. Three caspase-like molecules containing conserved caspase domains were identified and named RhCaspases 7, 8 and 9. RhCaspase8 and RhCaspase9 contain a long pro-domain at their N-terminals. An RT-qPCR assay demonstrated that the transcription of these three caspase genes increased significantly during the engorged periods of the tick developmental stages (engorged larval, nymph, and adult female ticks). Transcriptional levels of RhCaspases 7, 8 and 9 in salivary glands increased more significantly than other tissues post-engorgement. RhCaspase9-RNAi treatment significantly inhibited tick feeding. In contrast, knockdown of RhCaspase7 and RhCaspase8 had no influence on tick feeding. Compared to the control group, apoptosis levels were significantly reduced after interfering with RhCaspase 7, 8 and 9 expressions. Co-transfection assays showed RhCaspase7 was cleaved by RhCaspases 8 and 9, demonstrating that RhCaspases 8 and 9 are initiator caspases and RhCaspase7 is an executioner caspase. Conclusions: To the best of our knowledge, this is the first study to identify initiator and executioner caspases in ticks, confirm the interaction among them, and associate caspase activation with tick salivary gland degeneration.

Parasites use excretory-secretory pathways to communicate with the host. Characterization of exosomes within the excretory-secretory products reveal by which parasites manipulate their hosts. Parasite derived exosomes provide a mechanistic framework for protein and miRNAs transfer. Transcriptomics and proteomics of parasite exosomes identified a large number of miRNAs and proteins being utilized by parasites in their survival, reproduction and development. Characterization of proteins and miRNAs in parasite secreted exosomes provide important information on host-parasite communication and forms the basis for future studies. In this review, we summarize recent advances in isolation and molecular characterization (protein and miRNAs) of parasite derived exosomes.

Babesiosis caused by Babesia microti parasite is an emerging tick borne zoonotic disease that was confirmed recently in China. To understand the epidemiology characteristics of this emerging disease, infectivity of B. microti to domestic animals and ticks outside the genus Ixodes was evaluated in this study. Different domestic animals, chick, pig, goat, dog and the reference host rat were experimentally inoculated with B. microti-infected erythrocytes and the parasite infection was monitored daily by blood smear observation, real-time PCR detection, nested-PCR and special antibody responses during 55 days period. The results showed that rats infected with B. microti showed a typical sustained infection with strongly antibody responses; however, both goats and dogs infected with B. microti only showed transient antibody responses and the parasite was not found by blood smear observation or PCR; neither the parasite nor the special antibodies were detected in experimental chicks and pigs. On the other hand, the present study also experimentally investigated the infectivity of B. microti to Rhipicephalus haemaphysaloides, Haemaphysalis longicornis and Hyalomma asiaticum three species of ticks outside the genus Ixodes and the transmission experiment of B. microti between H. longicornis ticks and mice. Results showed that B. microti can be detected in the nymph and adult of these species after molting from engorged tick fed on infected mice, but the parasite was not detected in larvae hatching from eggs of engorged female tick fed on the infected mice. Transmission of B. microti to mice by infected H. longicornis nymphs was confirmed. These results indicated that these domestic animals do not have reservoir competence for B. microti, however, three species of ticks out of the genus Ixodes, common in China were successfully infected by B. microti, with H. longicornis showing the potential of transmitting the parasite to the vertebrate host.

To understand the epidemiology of tick infestation and tick-borne diseases in pet dogs in south-eastern China and to develop a reference for their prevention and treatment, we collected 1550 ticks parasitizing 562 dogs in 122 veterinary clinics from 20 cities of south-eastern China. Dogs were tested for common tick-borne pathogens; collected ticks were identified and processed for the detection of tick-borne pathogens. The use of an in vitro ELISA diagnostic kit for antibody detection (SNAP®4Dx® Plus) on dog sera found the infection rates with Borrelia burgdorferi sensu lato, Ehrlichia canis, and Anaplasma spp. to be 0.4%, 1.3% and 2.7%, respectively. By using a specific ELISA method, the infection rate with Babesia gibsoni was 3.9%. Rhipicephalus sanguineus sensu lato, Haemaphysalis longicornis and Rhipicephalus haemaphysaloides were the major tick species identified on pet dogs. PCR tests were conducted to detect five tick-borne pathogens in 617 ticks. The infection rate was 10.2% for E. canis, 3.4% for Anaplasma platys, 2.3% for B. gibsoni, 0.3% for B. burgdorferi s.l. and 0% for Babesia canis. Some ticks were co-infected with two (1.46%) or three pathogens (0.16%). These results indicate the infestation of pet dogs by ticks infected with tick-borne pathogens in south-eastern China, and the need for effective treatment and routine prevention of tick infestations in dogs. Pour comprendre l'épidémiologie de l'infestation par les tiques et les maladies transmises par les tiques chez les chiens domestiques dans le Sud-Est de la Chine et afin de fournir une référence pour leur prévention et leur traitement, nous avons collecté 1550 tiques parasitant 562 chiens dans 122 cliniques vétérinaires de 20 villes du Sud-Est de la Chine. Les chiens ont été testés pour des agents pathogènes courants de tiques. Les tiques collectées ont été identifiées et traitées pour la détection de pathogènes transmissibles par tiques. L'utilisation d'un kit de diagnostic in vitro ELISA pour la détection d'anticorps (SNAP®4Dx® Plus) sur les sérums de chiens, a mesuré le taux d'infection de Borrelia burgdorferi sensu lato, Ehrlichia canis et Anaplasma spp. à 0,4 %, 1,3 % et 2,7 % respectivement. En utilisant une méthode ELISA spécifique, le taux d'infection de Babesia gibsoni était de 3,9 %. Rhipicephalus sanguineus sensu lato, Haemaphysalis longicornis et Rhipicephalus haemaphysaloides étaient les principales espèces de tiques identifiées sur les chiens de compagnie. Des tests par PCR ont été effectués pour détecter cinq agents pathogènes transmissibles par les tiques dans 617 tiques. Le taux d'infection était de 10,2 % pour E. canis, 3,4 % pour Anaplasma platys, 2,3 % pour B. gibsoni, 0,3 % pour B. burgdorferi s.l. et 0 % pour Babesia canis. Certaines tiques étaient co-infectées avec deux (1,46 %) ou trois agents pathogènes (0,16 %). Ces résultats indiquent l'infestation des chiens de compagnie par des tiques infectées par des agents pathogènes transmissibles par les tiques dans le Sud-Est de la Chine et la nécessité d'un traitement efficace et de la prévention systématique des infestations de tiques chez les chiens.

Control of ticks has been achieved primarily by the application of acaricides, which has drawbacks such as environmental contamination leading to the selection of pesticide-resistant ticks. The potential of dsRNA to suppress genes critical for tick survival due to its sequence specificity suggests that dsRNAs could be developed as tailor-made pesticides. In this study, the dsRNA of P0 gene from the tick, Rhipicephalus haemaphysaloides, was evaluated as a potential anti-tick agent. Effects of using different dsRNA delivery methods were tested by quantitative RT-PCR and tick bioassays to determine survival, feeding and reproduction. The results showed that P0 dsRNAs could be effectively delivered into ticks and silenced by incubating with liposomes. Incubation time was found to be the most important factor in dsRNA delivery and gene silencing compared with liposome types and dsRNA concentration. The effects of P0 dsRNA treatment on ticks were found to be significant on blood feeding, molting or reproduction. These data show that anti-tick agents based on dsRNAs could have potential use in tick control.