The natural history of ticks☆

Blood feeding is a secondary adaptation in hematophagous bugs. Many proteins are secreted in the saliva that are devoted to coping with the host's defense and to process the blood meal. Digestive enzymes that are no longer required for a blood meal would be expected to be eventually lost. Yet, in many strictly hematophagous arthropods, α-amylase genes, which encode the enzymes that digest starch from plants, are still present and transcribed, including in the kissing bug Rhodnius prolixus (Hemiptera, Reduviidae) and its related species, which transmit the Chagas disease. We hypothesized that retaining α-amylase could be advantageous if the bugs occasionally consume plant tissues. We first checked that the α-amylase protein of Rhodnius robustus retains normal amylolytic activity. Then we surveyed hundreds of gut DNA extracts from the sylvatic R. robustus to detect traces of plants. We found plant DNA in 8% of the samples, mainly identified as Attalea palm trees, where R. robustus are usually found. We suggest that although of secondary importance in the blood-sucking bugs, α-amylase may be needed during occasional plant feeding and thus has been retained.

Tick saliva is a reservoir of bioactive proteins. Saliva protein compositions change dynamically during blood-feeding. Decipherment of protein profiles in different blood-feeding stages may bring deeper insight into tick feeding physiology and provide targets for immunologic control alternatives. However, having the infancy of tick genome sequencing, assembly, annotation, and limited knowledge of tick salivary proteins restrain the data interpretation. Here, we aimed to depict the saliva protein profile in partially- (PE) and fully-engorged (FE) Haemaphysalis flava ticks, with a special focus on the analysis of those uncharacterized proteins. Saliva was collected from PE and FE adult female H. flava ticks. Saliva proteins were analyzed by high-performance liquid chromatography-tandem mass spectrometry (HPLC/MS-MS). MS data were searched against an in-house salivary gland transcriptome library for identification of tick-derived proteins. Abundances of proteins were compared between PE and FE ticks. The uncharacterized proteins detected in saliva were further bioinformatically analyzed. In total, 614 proteins were identified including 94 host proteins and 520 tick-derived proteins. The 226 tick-derived high-confidence proteins were classified into 10 categories: transporters, enzymes, protease inhibitors, immunity-related proteins, lipocalins, glycine-rich proteins, muscle proteins, secreted proteins, uncharacterized proteins and others. A total of 98 proteins were shared in both PE and FE with 74 only in PE and 54 only in FE. Abundances of 24 shared proteins were significantly higher in PE. The profile of top 15 most abundant proteins was also different between PE and FE ticks. The 65 uncharacterized proteins detected in tick saliva were branched into subclusters 1 A, 1B, 2, 3 A, 3B and 3 C based on particular motifs like RGD, LRR, indicating their diverse predicted functions like anti-coagulation, regulation of innate immune, or other functions. This study provides and compares saliva proteomes of H. flava ticks in two feeding stages with special cluster analysis on the uncharacterized proteins. Further investigations are needed to confirm the roles of these uncharacterized proteins in ticks.

Ticks represent a major source of growing economic and public health concern, especially in the tropics and sub-tropics. Towards evidencing ticks’ invasion in the North and North–Western parts of Egypt, the present study aimed to investigate the morpho-molecular aspects of those ectoparasites using stereomicroscopy, scanning electron microscopy (SEM) and sequencing of the mitochondrial 16S ribosomal DNA gene (rDNA) and nuclear second internal transcribed spacer (ITS2). Our analysis confirmed the presence and well–distribution of Rhipicephalus sanguineus s.l. infesting dogs and sheep (Alexandria governorate), Rhipicephalus annulatus infesting cattle (Beheira governorate), and Hyalomma dromedarii infesting camels (Marsa Matruh governorate) from North/North–Western Egypt. 16S rDNA and ITS2 sequences of the ticks were amplified using universal and gene–specific sets of primers, sequenced and analyzed. Lengths of amplified 16S rDNA sequences in all examined tick species were found to be similar in size (approximately 460 bp); however, they differed in base pair constitutions, whereas ITS2 lengths were 1,500 bp, 1,550 bp, and 1,800 bp for Rh. annulatus, Rh. sanguineus s.l., and Hy. dromedarii, respectively. Phylogenetically, based on the 16S rDNA results, Rh. sanguineus s.l. ticks clustered with the southeastern Europe lineage from Romania and Greece, Rh. annulatus ticks were similar to Turkish populations, and Hy. dromedarii were close to the isolates from Tunisia. Similarly, based on ITS2 sequences, Rh. sanguineus s.l. from dogs were showing 99% similarity to Nigerian populations; however, those collected from sheep were closer to Iranian populations with 4.1% nucleotide divergence between the two populations of different hosts. Rh. annulatus ticks were identical to a population from Romania, whereas Hy. dromedarii was close by 99.7% similarity to a population from Kenya. This is the first study reporting nucleotide sequences of 16S rDNA and ITS2 in integration with morphological identification of ticks from this part of Egypt.

This study aimed to provide novel information for some poorly known/rare tick species collected from wild goats (Capra aegagrus) in the mountains of Eastern Anatolia, Turkey and to expand upon the available genetic data. The collected ticks were morphologically identified as Haemaphysalis kopetdaghica (all active stages, n = 140), Dermacentor raskemensis (adults, n = 7), Ixodes gibbosus (adults, n = 15), Rhipicephalus kohlsi (female, n = 1), and R. bursa (nymphs, n = 2). A total of 32 engorged ticks (6 larvae, 6 nymphs, and 20 females) collected were allowed to molt to the next stage or for egg laying and larval hatching, respectively. In addition, one R. kohlsi female (previously confirmed by SEM microscopy) collected from a wild goat in the neighboring province of Erzurum was included in this study for further genetic comparison. The partial mitochondrial 16S rDNA and cytochrome c oxidase subunit 1 (barcoding regions) genes of each tick species were sequenced. All DNA samples obtained from the ticks were checked by PCR for the presence of Anaplasma spp., Babesia spp., Borrelia burgdorferi sensu lato, spotted fever group rickettsiae, and Theileria spp., but were found to be negative. Phylogenetic analyses of the 16S rDNA and cox1 genes were performed using the ML method to determine their genetic relationship with related ticks. As a result, this study has: i) rediscovered and provided two new tick records (H. kopetdaghica and D. raskemensis) for Turkey, ii) provided the first genetic data for H. kopetdaghica and D. raskemensis and revealed their phylogenetic relationships, iii) characterized the cox1 region of I. gibbosus for the first time, and iv) revealed significant genetic diversity between R. kohlsi from Anatolia and R. kohlsi from Oman, suggesting that R. kohlsi could include a cryptic species.

Due to habitat destruction and illegal hunting and trade, the number of pangolins has been sharply reduced. To protect pangolins from extinction, relevant departments are combined and active action have been taken. A total of 21 confiscated Malayan pangolins were rescued in 2019, but died continuously for unknown reasons. This study aimed to investigate the reasons for the death of these pangolin and rescue them. 19 of the 21 confiscated pangolins had ticks on their body integument. A total of 303 ticks were collected and identified as Amblyomma javanense (A. javanense) according to their morphology and the sequences of 16S rRNA and internal transcribed spacer 2 (ITS2). There were multi-organ damages in the dead pangolins, especially congestion and hemorrhage in lung, heart and kidney and inflammation of which were observed using HE staining. Pathogens' nucleic acid detection showed ticks were only positive for Ehrlichia spp, with 56.7% positive rate of collected ticks (127/224), which was further confirmed in tissues from dead pangolins. Our findings confirm that ehrlichiosis caused by Ehrlichia spp. from A. javanense might accelerate the confiscated pangolin's death. More attention should be payed to tick-elimination work and the diagnoses and treatment of tick-borne diseases in the follow-up rescue operation.

In eastern North America, the blacklegged tick, Ixodes scapularis, is the vector for Borrelia burgdorferi sensu stricto and Anaplasma phagocytophilum, the causal agents for human and canine Lyme disease and anaplasmosis, respectively. The extensive range expansion of I. scapularis in Ontario is a growing veterinary and public health concern. However, there is limited information on the risk factors associated with I. scapularis carriage on dogs. Within an emerging area for Lyme disease risk in southeastern Ontario, we identified the tick species carried by dogs; determined the prevalence of B. burgdorferi and A. phagocytophilum in I. scapularis; and examined associations between pet demographics, travel history, and geographical location and the odds of: a dog carrying I. scapularis relative to other tick species (i.e., case-case design), and a removed I. scapularis being infected with B. burgdorferi. Seven species of ticks were collected from 543 companion dogs at 20 participating veterinary hospitals from April to December 2015. Ixodes scapularis were detected on 85.6% of parasitized dogs, and 7.5% of these dogs were carrying at least one B. burgdorferi-positive tick. Based on a multivariable logistic regression model, the odds of I. scapularis infestation relative to other tick species was significantly higher in fall and spring compared to summer, with closer proximity to Lake Ontario, in female compared to male dogs, in dogs weighing over 30 kg compared to lighter dogs, and in dogs that had not visited a farm in the 7 days prior to tick removal. Based on univariable exact logistic regression models, the odds of B. burgdorferi-positive I. scapularis carriage relative to B. burgdorferi-negative I. scapularis were significantly higher for dogs that traveled in the 14 days prior to tick removal, for those dogs under 1 year of age, and for those weighing less than 10 kg. This case-case study provides information for veterinarians and public health practitioners to help protect dogs and their owners from Lyme disease in southeastern Ontario.