The temperature and humidity preferences of Haemaphysalis longicornis, Ixodes Holocyclus and Rhipicephalus sanguineus (Ixodidae): studies on eggs

The eggs of Haemaphysalis longicornis, Ixodes holocydus and Rhipicephalus sanguineus were exposed to a range of temperatures and humidities to compare the temperature and humidity requirements of ticks from climatically dissimilar habitats. The response to changes in humidity was also studied with H. longicornis. Hatching in I. holocydus eggs occurred from 18 to 28°C and at a saturation deficit of 2 mm Hg or less. The eggs of R. sanguineus hatched between 18 and 38°C and tolerated saturation deficits up to 20 mm Hg. The eggs of H. longicornis hatched between 18 and 35°C and at saturation deficits up to 8 mm Hg. When eggs of H. longicornis were exposed to moderately dry conditions for different periods of time and then transferred to moist conditions, incubation periods and mortality were reduced in comparison with eggs kept continuously under dry conditions. On the other hand, mortality of H. longicornis eggs was reduced in moderately dry conditions, provided that they had been exposed to a moist environment for about 10 days previously. Weight loss of eggs in dry air and the rate of development of eggs were examined and are discussed. The eggs of I. holocylus lost weight very rapidly in dry air, whereas weight loss from R. sanguineus eggs was much slower. Weight loss from H. longicornis eggs fell between these two rates. The rate of development was fastest in R. sanguineus and slowest in I. holocydus.     

Transovarial passage of Leishmania infantum kDNA in artificially infected Rhipicephalus sanguineus

Phlebotomine sand flies are the only proven biological vectors of Leishmania parasites. However, Rhipicephalus sanguineus ticks have long been suspected to transmit Leishmania infantum in studies carried out in laboratory and natural conditions. In the present study, 5 μl of L. infantum promastigotes (1 × 10⁶ cells per ml) was injected into the hemocel through the coxa I of four engorged females (F1, F2, F3 and F4). Control ticks (F5 and F6) were injected with sterile phosphate-buffered saline (PBS) using the same procedure. Then, these females, their eggs, and the originated larvae were tested by real time polymerase chain reaction (real-time PCR) for the presence of L. infantum kinetoplast DNA (kDNA). Females and eggs were tested after the end of the oviposition period (about 5 weeks post-inoculation) whereas larvae were tested about 4 months after the inoculation of females. All artificially infected females were positive for L. infantum kDNA. In addition, two pools of eggs (one from F2 and other from F4) and four pools of larvae (one from each F1 and F4 and two from F2) were positive for L. infantum kDNA. These results showed, for the first time, the transovarial passage of L. infantum kDNA in R. sanguineus ticks, thus suggesting that the transovarial transmission of L. infantum protozoa in ticks is worth to be investigated.     

Azadirachta indica A. Juss (neem) induced morphological changes on oocytes of Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) tick females

Many studies have been conducted with plants whose extracts have the potential to be used for pest control. One of these plants is Azadirachta indica (neem), whose main active ingredient is azadirachtin, a compound shown to have acaricide and insecticide activity. Rhipicephalus sanguineus (brown dog tick) is currently considered to be an “urban pest,” because of its high levels of infestation and its ability to attack humans. In the present study partially and fully engorged R. sanguineus females were exposed to aqueous extracts of neem at concentrations of 10% and 20%, and to a control treatment. The results showed that differently from what was observed in the control, the pedicel cells of females exposed to neem at both concentrations lost their original shape. In the latter cases, the cytoplasm of the cells became fully vacuolated, especially near the germinal vesicle (oocyte nuclei) and in the oocyte pole, which is in contact with the cells of the pedicel. Oocytes in early stages of development (I and II) of ticks treated with both concentrations had irregular germinal vesicle, including the presence of two nucleoli as well as fragments of these. Oocytes in stages IV and V of exposed individuals showed full granular cytoplasm with bigger yolk granules when compared to the early stages. Chorion of mature oocytes was also altered, showing folds and deformations along their entire extension. The observed changes in cells of the reproductive system of R. sanguineus, especially in the oocytes, indicated the potential of neem as a new alternative method to control these ectoparasites.     

Experimental evaluation of birds as disseminators of the cosmopolitan tick Rhipicephalus sanguineus (Acari: Ixodidae)

Rhipicephalus sanguineus is believed to be the most widespread tick species of the world and its dissemination seems to rely on the diffusion of its main host, the dog. Empirical observations indicate that several bird species in urban areas regularly steal dog food. Such circumstances create a chance for R. sanguineus ticks to climb on birds and carry ticks to another site. In this work we evaluated experimentally the likelihood of birds (chicks) to either feed and/or carry R. sanguineus ticks from an infested site to another and to infest a host (rabbit) in the new location. Chicks were not suitable hosts for R. sanguineus ticks. Not a single adult tick engorged on chicks, yield as well as weight of engorged larvae and nymphs were very low and feeding period of these ticks was very long. However, a few larvae and, chiefly, nymphs were delivered to a new location either mechanically or after attachment and engorging total or partially on chicks. A few of these ticks fed successfully on rabbits. Further evidence on the capacity of birds to introduce R. sanguineus into non-infested dog settings should be provided by systematic examination of birds from urban areas, close to tick infested households.     

Transcriptome and toxin family analysis of the paralysis tick, Ixodes holocyclus

The Australian paralysis tick (Ixodes holocyclus) secretes neuropathic toxins into saliva that induce host paralysis. Salivary glands and viscera were dissected from fully engorged female I. holocyclus ticks collected from dogs and cats with paralysis symptoms. cDNA from both tissue samples were sequenced using Illumina HiSeq 100?bp pair end read technologies. Unique and non-redundant holocyclotoxin sequences were designated as HT2–HT19, as none were identical to the previously described HT1. Specific binding to rat synaptosomes was determined for synthetic HTs, and their neurotoxic capacity was determined by neonatal mouse assay. They induced a powerful paralysis in neonatal mice, particularly HT4 which produced rapid and strong respiratory distress in all animals tested. This is the first known genomic database developed for the Australian paralysis tick. The database contributed to the identification and subsequent characterization of the holocyclotoxin family that will inform the development of novel anti-paralysis control methods.     

The life history of Sulcascaris sulcata (Nematoda: Ascaridoidea), a parasite of marine molluscs and turtles

Berry G. N. and Cannon L. R. G. 1981. The life history of Sulcascaris sulcata (Nematoda: Ascaridoidea), a parasite of marine molluscs and turtles. International Journal for Parasitoiogy11: 43–54. The morphology, development and hatching of Sulcascaris sulcata eggs are described. Two moults occurred in the egg. Third stage larvae spontaneously hatched and were found to develop in marine bivalves and gastropods. Larvae grew steadily and after three to four months, when about 5 mm long, they moulted to fourth stage larvae characteristic of natural infections in bivalves from commercial catches. Experimentally, when fed to laboratory-reared Caretta caretta, the fourth stage larvae first attached at the oesophago-gastric junction where they moulted to adults in 7–21 days. Subsequent growth to mature adults was obtained by at least 5 months after infection. It is suggested that under natural conditions the life history may take up to 2 years to complete. These findings are discussed in relation to the predatory mode of feeding and the breeding habits of C. caretta and the significance of a possible health hazard to man.     

Behavior of larval Hemigrapsus sanguineus (de Haan) in response to gravity and pressure

Hemigrapsus sanguineus is an invasive species of crab (family: Grapsidae) in the north Atlantic basin. The species has spread rapidly since it was first discovered in North America in the late 1980s; however, the mechanisms of this range expansion remain unclear. This study attempts to predict the vertical distribution and, thus, ultimate transport of H. sanguineus larvae by examining larval responses to gravity and pressure. Geotaxis was determined by measuring the response of individual larvae to gravity in the absence of other tactic stimuli. Barokinesis was determined by measuring changes in swimming speed of larvae upon step-wise changes in pressure. Geotactic response of the larvae changes ontogenetically; early stage larvae are negatively geotactic (orienting towards the surface), while late stage larvae are positively geotactic (orienting towards the bottom). Larvae show a response to pressure that would aid in depth regulation. Early-stage larvae increase activity upon a change in pressure and orient their movement to gravity. However, the larvae show a relatively low sensitivity to pressure change. The evidence predicts an export-and-return model of larval transport, similar to that of Uca spp. in the Middle Atlantic Bight. This model supports the hypothesis that H. sanguineus larvae have the potential for high dispersal and will continue to invade new regions through larval transport.     

Detachment of hard ticks (Acari: Ixodidae) from hunted sika deer (Cervus nippon)

Ixodid ticks were collected from 13 sika deer, Cervus n. nippon, shot in the Boso Peninsula in central Japan from late February to early March 1999. Haemaphysalis megaspinosa was the most abundant species of the adults collected, although Haemaphysalis longicornis, H. flava, H. kitaokai, H. cornigera, Ixodes ovatus, and Amblyomma testudinarium were also collected. Males were more abundant than females for H. longicornis, H. megaspinosa, H. flava, and H. kitaokai. Ticks that had inserted their hypostome into its host skin (designated attached) were distinguished from those that were detached and on the host’s surface. A greater fraction of males than females of all four species were detached. Females were classified in three feeding stages (engorged, partially engorged, and unfed). More H. longicornis and H. megaspinosa unfed female ticks than engorged and partially-engorged female ticks were collected detached. Our results indicated that H. megaspinosa, H. longicornis, H. flava, and H. kitaokai male ticks detached sooner than female ticks after their host died.     

Some effects of time,temperature and feeding on infection rates with Babesia bovis and Babesia bigemina in Boophilus microplus larvae

Dalgliesh R. J. and Stewart N. P. 1982. Some effects of time, temperature and feeding on infection rates with Babesia bovis and Babesia bigemina in Boophilus microplus larvae. International Journal for Parasitology12: 323–326. Percentages of larval ticks in which Babesia bovis and B. bigemina parasites could be detected (infection rates) were determined after the larvae had been exposed to temperatures between 9°C and 27°C for periods of 1–35 days and then either fed on calves or heated at 37°C to stimulate babesial development. Infection rates with both species increased during 2–4 weeks after the larvae hatched, regardless of the temperature of exposure. Infection rates with B. bovis were higher after exposure of larvae to 14°C than to 27°C. This effect was less pronounced with B. bigemina. Infection rates were higher in fed larvae than in unfed, ‘heat stimulated’ larvae. The findings indicate that infected larval ticks become more efficient vectors of Babesia during the first 2–4 weeks after hatching and that repeated sampling of a tick population is necessary to determine valid infection rates.     

Association of the invasive Haemaphysalis longicornis tick with vertebrate hosts,other native tick vectors,and tick-borne pathogens in New York City,USA

Haemaphysalis longicornis, the Asian longhorned tick, is an invasive ixodid tick that has rapidly spread across the northeastern and southeastern regions of the United States since first reported in 2017. The emergence of H. longicornis presents a potential threat for livestock, wildlife, and human health as the host associations and vector potential of this invasive pest in the United States are poorly understood. Previous field data from the United States has shown that H. longicornis was not associated with natural populations of small mammals or birds, but they show a preference for medium sized mammals in laboratory experiments. Therefore, medium and large sized mammals were sampled on Staten Island, New York, United States, to determine H. longicornis host associations and vector potential for a range of human and veterinary pathogens. A total of 97 hosts were sampled and five species of tick (Amblyomma americanum, Dermacentor variabilis, H. longicornis, Ixodes scapularis, Ixodes cookei) were found feeding concurrently on these hosts. Haemaphysalis longicornis was found in the highest proportions compared with other native tick species on raccoons (55.4%), Virginia opossums (28.9%), and white-tailed deer (11.5%). Tissue, blood, and engorged larvae were tested for 17 different pathogens using a nanoscale PCR platform. Infection with five pathogens (Borrelia burgdorferi, Anaplasma phagocytophilum, Rickettsia spp., Mycoplasma haemocanis, and Bartonella spp.) was detected in host samples, but no pathogens were found in any larval samples. These results suggest that although large and medium sized mammals feed large numbers of H. longicornis ticks in the environment, there is presently a low potential for H. longicornis to acquire pathogens from these wildlife hosts.     

Acaricidal effect of <Emphasis Type="Italic">Schinus molle</Emphasis> (Anacardiaceae) essential oil on unengorged larvae and engorged adult females of <Emphasis Type="Italic">Rhipicephalus sanguineus</Emphasis> (Acari: Ixodidae)

The current concern about resistance to acaricides and the impact of toxic waste on the environment has led to the search of vegetal alternatives in the control of the brown tick of the dog Rhipicephalus sanguineus. Schinus molle L. (Anacardiaceae) derivatives have been associated with insecticidal, antimicrobial and antiprotozoal activities and essential oil showed to be lethal to R. microplus larvae. This study aimed at evaluating the acaricidal effect of essential oil of S. molle (EO_Sm) on engorged adult females and larval stages of R. sanguineus. One-hundred engorged females were obtained from the ears, interdigital spaces, neck, groin and base of the tail of two cross-bred dogs. The larvae package test was accomplished with 21-day-old larvae and five concentrations (v/v) of EO_Sm (0.125, 0.25, 0.50, 1 and 2%) in an anionic detergent, a synthetic acaricide (cypermethrin) and detergent and deionized water as controls. The immersion adult test was carried out with nine concentrations (0.125, 0.25, 0.50, 1, 2, 4, 8, 16, 20%) of the EO_Sm. At the concentration of 2%, EO_Sm caused 99.3% of larval mortality. In adults, inhibition of oviposition, egg hatching (EH) and reproductive efficiency (RE) values were dose-dependent from 4 to 20% EO_Sm; the lowest values of EH (29.62) and RE (22.61) were achieved with 20% EO_Sm. Strong and negative correlations were found between concentration of EO_Sm and EH (r?=???0.948) and between concentration of EO_Sm and RE (r = ??0.985). This study demonstrated for the first time the acaricidal effect of EO_Sm on larvae and reproductive parameters of engorged adult females of R. sanguineus.     

Development and biological characteristics of <Emphasis Type="Italic">Haemaphysalis longicornis</Emphasis> (Acari: Ixodidae) under field conditions

The development and biological characteristics of Haemaphysalis longicornis were investigated under field conditions in Xiaowutai National Natural Reserve Area, North China. Unfed larvae, nymphs and adults were fed on rabbits and exposed to daylight. Three free-living stages were allowed to develop in field plot selected in a tick natural habitat. The host seeking behavior and seasonal occurrence were observed. Haemaphysalis longicornis were active from mid March to mid October. The premoult period of nymphs and preoviposition of females were regulating phases of their life cycle. The developmental durations of eggs, larvae and adults were constant under field conditions regardless when the development started. The oviposition periods in May and June were statistically shorter than those in July and August. The daily oviposition patterns of females engorged in May and June demonstrated unobvious peak, which differed from those engorged in July and August. The daily oviposition peak of the latter occurred on the 4th day of oviposition. Moreover, a positive correlation was found between the mass of the laid egg and the body weight of engorged females (r = 0.62, P < 0.001). The female reproductive efficiency indices were 2.9, 6.1, 10.5 and 9.0 in May, June, July and August, respectively. The mean weight (3.33 mg) of engorged nymphs molting to females was significantly higher than that (2.35 mg) of those molting to males (P < 0.001), but the body weights of both sexes were overlapping.     

Activity of disconnected corpora allata in Locusta migratoria: Juvenile hormone biosynthesis in vitro and physiological effects in vivo

Severance of nervi corporis allati I (NCA I) in day-1 adult female Locusta migratoria resulted in a significant decrease and a loss of the characteristic pattern of juvenile hormone biosynthesis by the corpora allata as determined by radiochemical assay. This decrease in the rate of juvenile hormone biosynthesis was not reflected in basal oöcyte growth. The lengths of the oöcytes were the same in NCA-transectioned and in the sham-operated females. The effect of severance of both NCA I and NCA II on juvenile hormone biosynthesis and ovarian maturation was similar to the effect of NCA I severance only.Rate of juvenile hormone biosynthesis by corpora allata of fourth-instar larvae exhibited a maximum of activity in the middle of the stadium. The severance of NCA I early in the stadium resulted in a very low rate of juvenile hormone biosynthesis and a disappearance of this peak. In NCA I-transectioned larvae, the duration of the stadium was significantly increased although larvae moulted into normal fifth instar.     

Resistance in cattle to Haemaphysalis (Kaiseriana) longicornis

Samples of each instar of the 3-host tick, Haemaphysalis (Kaiseriana) longicornis were collected from grazing Bos taurus cattle to investigate their survival on hosts with previous exposure to the tick and on previously unexposed ‘naive’ hosts. The ticks were allocated to categories based on their size to observe at what stage of development mortality occurred. Analysis of the age structure of the ticks showed that small but variable proportions of larvae, nymphs and females matured on previously exposed hosts and larger proportions on the naive hosts. This suggests that cattle acquire and express different levels of resistance against each instar of the tick. The technique used has potential for estimating levels of resistance of hosts to 3-host ticks under field conditions.     

Variability in response of four populations of Amblyseius largoensis (Acari: Phytoseiidae) to Raoiella indica (Acari: Tenuipalpidae) and Tetranychus gloveri (Acari: Tetranychidae) eggs and larvae

Raoiella indica (Acari: Tenuipalpidae) is a phytophagous mite that recently invaded the Neotropical region. A predatory mite Amblyseius largoensis (Acari: Phytoseiidae) has been found associated with R. indica in Florida. This study evaluated A. largoensis by determining its likelihood of consuming eggs and larvae of R. indica and Tetranychus gloveri (Acari: Tetranychidae) under no-choice and choice conditions. To detect variations in the response of A. largoensis to R. indica, four populations of predators were examined: (1) predators reared exclusively on R. indica in the laboratory for 2 years, (2) predators reared on T. gloveri in the laboratory for 2 months but reared on R. indica for 2 years previously, (3) predators collected from a field infested with R. indica, and (4) predators collected from a field that had never been infested with R. indica. Results of this study suggest that A. largoensis is likely to accept and consume high numbers of R. indica eggs regardless of their previous feeding experience. In contrast, all populations consumed relatively fewer R. indica larvae than the other prey tested. Predators previously exposed to R. indica were more likely to consume R. indica larvae. By contrast, predators not previously exposed to R. indica showed the lowest likelihood of choosing to feed on this prey item. Plasticity in the response of A. largoensis to R. indica larvae could be associated to selection, learning, or a combination of both. The possible implications of the observed differences in terms of biological control of R. indica are discussed.     

Biological aspects of the interaction between Coelomomyces psorophorae zygotes and the larvae of Culiseta inornata: Environmental factors

Zygotes of the obligately parasitic watermold Coelomomyces psorophorae encyst on the cuticular surface of susceptible mosquito larvae as the initial step in the infection process. Zygotes can successfully encyst on Culiseta inornata larvae at temperatures from 12°–30°C, with an optimum of 25°C. Optimum encystment on larvae occurs from pH 6.5–8.5, with activity documented from pH 5.0–9.5. Zygotes are active in water with total salinity of 5.4 ppt down to double glass-distilled water.     

Cold-stress response of engorged females of <Emphasis Type="Italic">Rhipicephalus sanguineus</Emphasis>

We investigated the effect of prolonged exposure to low temperature on engorged females of Rhipicephalus sanguineus. Five groups of two females (F1–F5) were maintained at 8 ± 2°C, 70 ± 10% RH, and 24 h scotophase, for 15, 30, 45, 60 and 75 days. One group was maintained in the incubator (26 ± 1°C, 70 ± 10% RH, and 24 h scotophase) as control. The results show that egg hatch rate, longevity and reproductive fitness of engorged females of R. sanguineus are negatively correlated with the duration of exposure to low temperature, whereas preoviposition period was positively correlated with exposure to the cold. This shows that the engorged female ticks are sensitive to prolonged exposure to low temperature, and it may explain why females of this tick species are not reproductively active during winter. Our results confirm that temperature is a major limiting factor for the establishment of stable R. sanguineus populations in cold temperate regions of Europe.     

Characterization of the conspecific metamorphic cue for Hemigrapsus sanguineus (De Haan)

The Asian shore crab, Hemigrapsus sanguineus, is one of the most abundant invasive crabs along the east coast of the United States. Larval stages are generally planktonic, but the megalopa stage settles to the substratum near the time of metamorphosis. Reducing the time to metamorphosis may result in higher recruitment and survival. Previous work has shown that a water-soluble cue produced by adult H. sanguineus can induce metamorphosis of conspecific megalopae. Here we report the results of experiments in which megalopae were exposed to cues produced by different life stages of H. sanguineus. We also provide data from experiments that investigated the temporal stability, detection threshold, and chemical classification of the cue. Our results indicate that an active cue is produced by juveniles as well as adults. The cue is proteinaceous and begins to degrade within 2 days of production. The threshold for detection of the cue by megalopae lies between 0.1 and 0.01 µg of protein per ml.     

Factors influencing the toxicity of salivary gland extracts of Ixodes holocyclus Neumann

A bioassay using mice was developed to compare the toxin content of extracts of salivary glands of I. holocyclus at various stages of feeding. The quantity of toxin increased rapidly from the third day of feeding. Toxin production continued and increased in ticks removed after 3–5 days on mice and held at 30°C at 92% RH for 24 h, whereas no toxin was detected in the salivary glands of ticks fed for 3 days and treated similarly. It is suggested that major physiological changes occur in the salivary glands of I. holocyclus on the third day, which once stimulated continue independently of feeding. Toxin production in ticks was not suppressed by passively immunizing mice with anti-tick toxin but was in ticks fed upon hosts with a previous experience of tick feeding.Thus, to obtain salivary glands containing high concentrations of toxin for chemical analysis, it is necessary for salivary glands to develop 5 days from the initial attachment of the tick to a host with no previous experience of tick feeding. This can be achieved by passively immunizing mice against toxin, thus enabling the tick to feed 5 days without killing the mouse or by keeping the tick for 24 h at 30°C at 92% RH following the death of the mouse on the fourth day.