Larval feeding performance of two Neotropical Ornithodoros ticks (Acari: Argasidae) on reptiles

First record of Alectorobius coniceps (Ixodoidea: Argasidae) and Dermacentor sp. (Ixodoidea: Ixodidae) in Pakistan

Alectorobius species are soft ticks primarily infesting birds, such as swallows, while Dermacentor species are hard ticks mainly infesting mammals, such as small ruminants. This study for the first time reported on the morphological and molecular bases of two tick species, namely A. coniceps and a Dermacentor sp. in Pakistan. The former species was examined in swallows' nests in Khyber Pakhtunkhwa province, while the latter species was examined in small ruminants in Balochistan province. In total, 25 ticks were collected, with 14 ticks morphologically identified as A. coniceps (males = 9 and females = 5) and 11 ticks identified as Dermacentor sp. (males = 7 and females = 4). Following morphological identification, molecular identification was gained by obtaining 16S rDNA and cox1 sequences for these ticks. The BLAST results for the 16S rDNA and cox1 sequences from A. coniceps shared a maximum identity of 97.46% and 96.49% with the same species from Malta. The BLAST analysis of the 16S rDNA and cox1 sequences from Dermacentor sp. showed maximum identities of 98.42% and 97.45% with Dermacentor pavlovskyi from China. The phylogenetic analysis based on 16S rDNA and cox1 of A. coniceps showed a close evolutionary relationship with the same species. The case of Dermacentor sp., based on 16S DNA and cox1, indicated a close evolutionary relationship with Dermacentor pavlovskyi from China.

Noteworthy records of the ticks Ornithodoros rostratus and Amblyomma sculptum parasitizing Pteronura brasiliensis in the central-western region of Brazil, with pathogen investigation notes

A male of Pteronura brasiliensis (Carnivora: Mustelidae) was found dead on the banks of the Rio Negro, in the Pantanal wetlands of Mato Grosso do Sul state, Aquidauana municipality. Two ticks found attached to its skin were morphologically identified as a second-instar nymph of Ornithodoros rostratus (Argasidae) and a male of Amblyomma sculptum (Ixodidae). In order to complement the morphological identification, these tick specimens were subjected to DNA extraction, and tested using PCR assays to confirm the molecular identity the specimens. Also, the tick DNA samples were tested and were negative in the PCR assays for all the pathogens tested. We also examined 30 batches, consisting of 174 individuals of O. rostratus deposited in the Acari Collection of the Butantan Institute, and we found material from four Brazilian states, including one batch containing 2 males and 2 females from Aquidauana, of Mato Grosso do Sul state, collected from the soil. This was therefore the first record of O. rostratus parasitizing P. brasiliensis and the first locality record (Aquidauana). Likewise, A. sculptum is commonly found in the Pantanal and is reported here for the second time parasitizing the giant otter, which is a host little studied regarding the ectoparasites.

Reliability of molecular host-identification methods for ticks: an experimental in vitro study with Ixodes ricinus

BACKGROUND

Reliable information on host use by arthropod vectors is required to study pathogen transmission ecology and to predict disease risk. Direct observation of host use is often difficult or impossible and indirect methods are therefore necessary. However, the reliability of currently available methods to identify the last host of blood-feeding arthropods has not been evaluated, and may be particularly problematic for ticks because host blood has been digested at capture. Biases in host detection may lead to erroneous conclusions on both vector ecology and pathogen circulation.

METHODS

Here, we experimentally tested for biases in host detection using the generalist three-host tick Ixodes ricinus as a model system. We fed ticks using an artificial feeding system and amplified blood meal traces post-moult (i.e., in the succeeding unfed life stage) via both a quantitative real-time polymerase chain reaction assay and a reverse line blotting method. We then experimentally tested for three types of biases in host detection: 1) time post-moult, 2) tick life stage and 3) host type (non-nucleated mammal blood versus nucleated avian blood), and compared these biases between the two molecular methods.

RESULTS

Our results show that all three factors can influence host detection in ticks but not necessarily in the expected way. Although host detection rates decreased with time post-moult, mammal blood tended to be more readily detected than bird blood. Tick life stage was also an important factor; detection was higher in nymphs than in adults and, in some cases, remnants from both larval and nymphal blood meals could be detected in the adult stage. These biases were similar for the two detection techniques.

CONCLUSIONS

We show that different factors associated with questing ticks may influence our ability to correctly infer previous host use and that these factors may bias inferences from field-based studies. As these biases may be common to other vector-borne disease systems, their implications for our understanding of vector ecology and disease transmission require more explicit consideration.

Life cycle of Ornithodoros rostratus (Acari: Argasidae) ticks feeding on mice under laboratory conditions

Ornithodoros rostratus Aragão is an argasid tick found in Bolivia, Paraguay, Argentina and Brazil. Only limited studies about O. rostratus have been conducted and several aspects of their life cycle differ among studies or remain unexplored. In order to better elucidate the biology of O. rostratus, the present work describes its life cycle when feeding on mice under laboratory conditions. To complete their life cycle on mice, O. rostratus goes through a larval stage, 3-6 nymphal instars (nymph 1-6) and adult male and female. Adults can be originated from nymph 3-6. Nymphs 4 with higher weight after feeding tend to originate adults. Adults originated from early instars tended to be lighter. Females tended to be heavier than males. Larvae needed on average 2.7 days to complete their blood meal whereas other instars ranged from 17.3 to 78.3 min. The capacity to ingest blood was higher in larvae and females in comparison to males. The preecdysis period ranged from 5 to 12.5 days. After one blood meal, females remain on average 15.2 ± 5.8 days laying 276.8 ± 137.2.9 eggs. Females originated from nymph 4 had similar oviposition time, egg incubation and conversion ingested blood/number of eggs produced, but presented lower initial weigh and weigh gain, generating fewer eggs. Our results added novel information on O. rostratus biology and was discussed considering the variability of argasid populations and in context with the differences about their life cycle described in previous works.

Life cycle of Ornithodoros rostratus (Acari: Argasidae) under experimental conditions and comments on the host-parasite relationship in the Pantanal wetland region, Brazil

The genus Ornithodoros is represented by 15 species in Brazil, on which no detailed life cycle studies have been published, except for O. talaje and O. mimon. The aim of the present study was to evaluate life cycle parameters of O. rostratus based on ticks collected in the Pantanal wetland region of the state of Mato Grosso do Sul, Brazil, using domestic rabbits as experimental hosts. The periods of pre-attachment and feeding of the larvae lasted an average of 39 min (range 15-76 min). Five or six nymphal instars were found. The emergence of adults started with N3 in the following sequence: N3-two males; N4-13 males; N5-three males and 16 females; and N6-two females. Mean weight of N4 that molted to males was 31.7 ± 13.6 mg, whereas mean weight of N5 that molted to females was 100.1 ± 36.2 mg. The overall sex ratio was 1:1. Oviposition lasted 14 days, with a sharp decline beginning with the 7th day. The overall duration of the life cycle of O. rostratus ranged from approximately 66 to 136 days. Comments on the tick-host relationship in the Pantanal region are offered.

Effects produced by the feeding of larvae of Ornithodoros aff. puertoricensis (Acari: Argasidae) on laboratory mice

The clinical picture produced by the feeding of larvae of Ornithodoros aff. puertoricensis on laboratory mice, was studied using different larval infestation protocols that included 30, 40 or 50 larvae per mouse and control uninfested groups. Clinical effects appeared around 72 h of larval feeding, having a first stage characterized by hyperaemia in both nasal and ocular mucosa, followed by respiratory symptoms (96-120 h) and nervous incoordination (120-144 h). No one mouse evidenced paralysis, and nervous symptoms were never observed in animals infested with only 30 larvae. High mortality (commonly up to 70%) was observed in mice with respiratory symptoms, while 100% of animals in the nervous phase died between 168 and 192 h after the beginning of larval feeding. When some infested mice were treated with a solution of Amitraz the larvae were killed and reversion of symptoms was observed. These effects are ascribed to the presence of a toxin in the saliva of the feeding larvae.