The natural hosts for larvae and nymphs of Amblyomma neumanni and Amblyomma parvum (Acari: Ixodidae)

Based on the hypothesis that birds and rodents are important hosts for subadults of the Neotropical Amblyomma neumanni and Amblyomma parvum ticks, a survey of these type of hosts was carried out from July 2004 to March 2006, in Quilino (A. parvum) and Dean Funes (A. neumanni), Córdoba province, Argentina. Additionally, monthly tick counts were performed on cattle and goats with occasional tick search in other domestic hosts. Records of questing height of subadult ticks on vegetation were also carried out monthly. Rodents (n = 123) and birds (n = 122) captured in Dean Funes showed no infestation with A. neumanni. Apart of few nymphs found on horses, all larvae and nymphs of A. neumanni were on cattle with a larval prevalence and mean number of 22.2%, and 7.7 ± 22.52, respectively, and a prevalence of nymphs of 47.8% with a mean of 7.9 ± 18.49. The average questing height of larvae and nymphs of A. neumanni was 23.5 ± 17.1 cm and 30.7 ± 26.7 cm, respectively. A total of 138 rodents and 130 birds were captured in Quilino but the Caviidae rodent Galea musteloides carried 99.3% of larvae and 99.8% of nymphs of A. parvum, and no immature stages were detected on cattle, goat or vegetation. Tick counts on G. musteloides (n = 74) showed a prevalence of 42% and a mean number of 9.9 ± 24.83 for larvae, while nymphal infestation had a prevalence of 56.5% and a mean of 8.7 ± 11.31. Cattle appear to be suitable hosts to sustain the complete cycle of A. neumanni in nature (adult ticks infest cattle too) and questing height of subadults indicates that they are expecting to feed on medium and large-sized mammals, such as cattle and other ungulates. At least in the study site, G. musteloides is the principal host for the survival strategy of A. parvum subadults; adult ticks are common on cattle and goats. These hosts are introduced in the Neotropics but A. neumanni was able to develop a surrogate cycle independent of native hosts while A. parvum still depends on probably primeval hosts to sustain their larvae and nymphs.     

Host location by larvae of the reptile tick Amblyomma vikirri (Acari: Ixodidae)

The newly described tick Amblyomma vikirri has a narrow host range, being found mainly on the Australian lizard, Egernia stokesii and rarely on another lizard, Tiliqua rugosa. Both hosts are in the family Scincidae. Larvae of A. vikirri were as successful in locating E. stokesii as T. rugosa from a range of release distances between 20 and 120 mm from the host. Over this range the proportion of ticks which successfully located hosts declined and the time taken by successful ticks to locate hosts increased with increasing release distance. From 60 mm, larvae of A. vikirri located four other lizard species from the families Scincidae and Agamidae and two non-living targets as successfully as they did E. stokesii. The only evidence that there was any host specificity in the searching behaviour of larvae of A. vikirri was that A. vikirri larvae spent less time paused and questing when they were searching for E. stokesii than when they were searching for T. rugosa. Aponomma hydrosauri, a tick which commonly infests T. rugosa but not E. stokesii, spent less time paused and questing when it was searching for T. rugosa than when it was searching for E. stokesii. However, the results overall suggest that the narrow host range of A. vikirri cannot be explained by any ability of the larvae of that species to discriminate between their natural host and other reptile species.     

Influence of temperature and relative humidity on the development ofAmblyseius alstoniae (Acari: Phytoseiidae)

Reproduction and development ofAmblyseius alstoniae Gupta is significantly affected by temperature and relative humidity (rh), optimum being a temperature of 25°C andrh of 70%. At this combination, the viability of eggs, fecundity and daily egg production were higher, oviposition period and longevity were of longer duration, and mortality was minimal. Increase or decrease in these temperature andrh levels leads to a drop in fecundity, longevity and oviposition period and an increase in mortality. Longevity of females is always greater than that of males, irrespective of temperature andrh. Female: male ratio decreases with increase in temperature, irrespective ofrh.     

Hyperparasitism in Amblyomma rotundatum (Acari: Ixodidae)

In the present study, we report a case of hyperparasitism in Amblyomma rotundatum. During examination of live ticks immediately after collecting them from Boa constrictor snakes held in a reptile facility in Mossoró, RN, northeastern Brazil, 1 unengorged tick female was seen attached to the venter of a partially engorged female. The hypostome and chelicerae of the unengorged female had penetrated the integument of the partially engorged female to the level of the basis capitulli and the palps were splayed outward. To our knowledge, we present the second report of hyperparasitism for the genus Amblyomma.     

Indirect evidence of density‐dependent population regulation in Aponomma hydrosauri (Acari: Ixodidae), an ectoparasite of reptiles

Abstract The extent to which density‐dependent processes regulate natural populations is the subject of an ongoing debate. We contribute evidence to this debate showing that density‐dependent processes influence the population dynamics of the ectoparasite Aponomma hydrosauri (Acari: Ixodidae), a tick species that infests reptiles in Australia. The first piece of evidence comes from an unusually long‐term dataset on the distribution of ticks among individual hosts. If density‐dependent processes are influencing either host mortality or vital rates of the parasite population, and those distributions can be approximated with negative binomial distributions, then general host–parasite models predict that the aggregation coefficient of the parasite distribution will increase with the average intensity of infections. We fit negative binomial distributions to the frequency distributions of ticks on hosts, and find that the estimated aggregation coefficient k increases with increasing average tick density. This pattern indirectly implies that one or more vital rates of the tick population must be changing with increasing tick density, because mortality rates of the tick's main host, the sleepy lizard, Tiliqua rugosa, are unaffected by changes in tick burdens. Our second piece of evidence is a re‐analysis of experimental data on the attachment success of individual ticks to lizard hosts using generalized linear modelling. The probability of successful engorgement decreases with increasing numbers of ticks attached to a host. This is direct evidence of a density‐dependent process that could lead to an increase in the aggregation coefficient of tick distributions described earlier. The population‐scale increase in the aggregation coefficient is indirect evidence of a density‐dependent process or processes sufficiently strong to produce a population‐wide pattern, and thus also likely to influence population regulation. The direct observation of a density‐dependent process is evidence of at least part of the responsible mechanism.     

Effect of delayed mating and prolonged engorgement on the reproductive fitness of female Amblyomma limbatum (Acari: Ixodidae) in marginal population areas

Reptile ticks mate while females are attached to their host. Following mating, females engorge, detach and then lay their eggs. This study examines whether the time that females of the reptile tick Amblyomma limbatum spend on hosts prior to mating and the time they take to engorge on hosts after mating influence their reproductive fitness, as measured by the number of viable eggs they produce. When compared with females that experienced no temperature-induced delay in mating, females attached for an initial period to hosts with body temperatures too low to induce mating had no decline in their reproductive fitness, once provided with suitable temperatures for mating. However, on hosts with suitable body temperatures for mating, female ticks that took longer to mate, took longer to engorge and had reduced reproductive fitness. In addition, females that spent more than 20 days feeding on hosts after mating had reduced reproductive fitness, irrespective of the time they spent on hosts prior to mating compared with females with shorter feeding periods. Thus, the time that A. limbatum females spent on hosts prior to mating and/or after mating has a significant bearing on the number viable progeny produced. The ecological implications of these results are discussed in relation to females colonizing marginal population areas at the edge of their distributional range.     

Morphogenetic diapause in Amblyomma variegatum (Acari: Ixodidae)

In southern Africa, Amblyomma variegatum Fabricius is characterized by a strict seasonal activity. Experiments were carried out to determine whether a diapause mechanism regulates this seasonality. Engorged A.variegatum females were exposed to controlled laboratory conditions or natural field conditions at different times of the year. Females exposed in a natural environment in September-October (short day) had significantly longer pre-oviposition periods than females exposed from November to March. The season in which the previous instar fed had no apparent effect on the engorgement or pre-oviposition periods of the females. Furthermore, artificial changes in photoperiod during and after female engorgement had no significant effects on pre-oviposition periods. It is tentatively concluded that the unfed female is the responsive stage to photoperiodic changes which induce diapause. Diapause could be terminated and oviposition induced by exposing females to a short period of chilling (18 degrees C for 48 h). It is concluded that a morphogenetic diapause mechanism exists in A.variegatum, which is probably induced by short day responses and terminated following rainfall and a concomitant decrease in soil temperature. The diapause, which occurs in females which fed early in the season, causes a delay in oviposition and therefore effectively synchronizes the life-cycle to ensure that eggs and larvae occur at a climatically favourable period.     

Toxicity of solvents and surfactants to Amblyomma cajennense (Fabricius, 1787) (Acari: Ixodidae) and Dermacentor nitens (Neumann, 1897) (Acari: Ixodidae) larvae

The objective of this work was to verify the sensitivity of Amblyomma cajennense and Dermacentor nitens larvae to the solvents ethanol, methanol, acetone, xylol and dimethyl sulfoxide (DMSO) and the surfactant Tween 80. The first four solvents were tested at analytical purity while the DMSO and surfactant Tween 80 were tested at a concentration of 1%. The substances tested at analytical purity that caused high mortality were also tested at concentrations of 50%, 25% and 1%. The larval packet test was used, with 10 repetitions for each treatment. A control group was also formed with the same number of repetitions, in which the larvae were only exposed to distilled water. In the first experiment, only xylol was highly toxic at the concentrations tested, causing mortality above 90% for larvae of both species. In the second experiment, xylol at 1% and at 25% showed low toxicity to the A. cajennense and D. nitens larvae, respectively, since the percentage mortality was statistically similar to that of the control group (p>0.05).     

Lack of parthenogenesis by Amblyomma cajennense (Acari: Ixodidae)

Some reproductive parameters of adult stages of Amblyomma cajennense ticks were studied. The capacity of virgin females to reproduce by parthenogenesis was evaluated, during an experimental infestation, in absence of males, on a horse (Equus cabalus). Ticks were spread either completely free or in limited sites on the body of the animal. The engorged virgin females showed longer feeding periods and lighter body weights than those that had been fertilized. Some of these unmated females produced smaller egg masses, which had no embryonary development. On the other hand, females that had been inseminated produced larger egg masses, with normal embryonary development that led to viable larvae. Under the studied conditions, A. cajennense females did not reproduce by parthenogenesis.     

Influence of aggregation and relative humidity on longevity of unfed bush tick, Haemaphysalis longicornis Neumann (Acari: Ixodidae)

The survival of all stages of Haemaphysalis longicornis was investigated at different densities and at 3 levels of relative humidity. Larvae survived longer when the density was higher, or the size of a cluster was larger, or both. However, in nymphs and adults, there was no significant relationship between the density and the survival period. Moreover, in nymphs and adults, there was no positive relationship between the size of the aggregation and tick longevity, except for 2 nymphs/vial in high humidity. These results suggest that the advantage gained from a higher density, or from taking part in a cluster, or both, differed between stages. Furthermore, the fact that the survival period of larvae and nymphs was influenced by cohort suggests that a maternal effect, as well as aggregation, influences the survival of immature ticks.     

Gynandromorphism in Amblyomma cajennense and Rhipicephalus sanguineus (Acari: Ixodidae)

During a survey of ticks on horses in November 2000, at the University of S?o Paulo farm in Pirassununga county, S?o Paulo, Brazil, 1 gynandromorph of Amblyomma cajennense was collected from a naturally infested horse. In another survey on dogs in March 2001, in the urban area of Monte Negro, Rond?nia, Brazil, a gynandromorph of Rhipicephalus sanguineus was collected from a naturally infested dog. Both specimens are described and classified as perfect bipartite protogynanders.     

Sigmodontinae rodents as hosts for larvae and nymphs of Ixodes loricatus Neumann, 1899 (Acari: Ixodidae)

Larvae and nymphs of Ixodes loricatus Neumann, 1899 ticks (confirmed by morphological characters and by comparison of 16S mitochondrial rDNA sequences) were collected from Sigmodontinae Wagner, rodents in central and northern Argentina and Uruguay. A total of 100 larvae and 38 nymphs of I. loricatus were collected on the genera Akodon Meyen (n = 36 individuals), Calomys Waterhouse (n = 2), Oligoryzomys Bang in = 12), Oxymycterus Waterhouse (n = 9), and Scapteromys Waterhouse (n = 13). 72 larvae and 18 nymphs were collected on Akodon. Adults of I. loricatus were found in central Argentina and Uruguay on Didelphimorphia of the genera Didelphis Linnaeus and Lutreolina Thomas. Ixodes loricatus has been considered a species with strict total specificity to Didelphimorphia. Our results show that this statement may not be justified. Sigmodontinae rodents are sympatric and share habitats with the phylogenetically distant Didelphimorphia; infestation with I. loricatus seems to be its consequence. We tentatively consider I. loricatus moderately specific to Didelphimorphia.     

The life cycle of Amblyomma pseudoparvum (Acari: Ixodidae) in the laboratory

A colony of Amblyomma pseudoparvum was started with male and female ticks collected from the cavy-like rodent Dolichotis salinicola, in the Province of Salta, Argentina. These ticks and their progenies were fed on rabbits and the non-parasitic stages maintained in darkness at 27±1°C, 83–86% RH. The life cycle (pre-feeding and oviposition periods not tested) of A. pseudoparvum had a mean duration of 90.9 days. The mean time (days) for the different periods of the cycle were as follows: Feeding of females, 12.3; pre-oviposition, 5.1; minimum egg incubation, 33.4; feeding of larvae, 5.6; pre-moult to nymphs, 11.5; feeding of nymphs, 6.9; pre-moult to adults, 16.1. The mean recovery rates of larvae, nymphs and females were 16.0%, 18.7% and 53.0%, respectively.     

Suppression of host-seeking Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae) nymphs after dual applications of plant-derived acaricides in New Jersey

We evaluated the ability of dual applications of natural, plant-derived acaricides to suppress nymphal Ixodes scapularis Say and Amblyomma americanum (L.) (Acari: Ixodidae) in a Lyme disease endemic area of New Jersey. An aqueous formulation of 2% nootkatone provided >90% control of I. scapularis through 7 d. Control declined to 80.9% at 14 d, and a second application was made that provided >95% control through the remaining 4 wk of the nymphal season. Nootkatone provided >90% control of A. americanum through 35 d postapplication. Applications of 2% carvacrol and EcoTrol T&O resulted in rapid knockdown of both tick species, but control declined significantly to 76.7 and 73.7%, respectively, after 14 d when a second application was made that extended control of both tick species to between 86.2 and 94.8% at 21 d. Subsequently, control declined steadily in all plots by 42 d postapplication except for I. scapularis in carvacrol-treated plots, where levels of control >90% were observed through 35 d. Of the three compounds tested, 2% nootkatone provided the most consistent results, with 96.5 and 91.9% control of I. scapularis and A. americanum through 42 and 35 d, respectively. The ability of plant-derived natural products to quickly suppress and maintain significant control of populations of these medically important ticks may represent a future alternative to the use of conventional synthetic acaricides. In addition, the demonstrated efficacy of properly-timed backpack sprayer application may enable homeowner access to these minimal-risk acaricides.     

Antiviral effect of the egg wax of Amblyomma cajennense (Acari: Ixodidae)

The control of viral infections, especially those caused by influenza viruses, is of great interest in Public Health. Bio prospection has shown the presence of active principles in the hemolymph of arthropods, and in the salivary gland of ticks, and some of these are of interest for the development of new pharmacological drugs. Ticks lay their eggs in the environment, and to protect them from desiccation and microbial attack they involve the eggs in a waxy layer produced by an organ known as Gené’s Organ. In this study, the eggs wax from tick Amblyomma cajennense (Fabricius) was extracted using ice cold phosphate buffer. The antiviral activity was evaluated with picornavirus and influenza virus. In both cases egg wax was able to inhibit virus replication. For influenza virus, an amount as small as 12 μg/mL of crude egg wax suspension neutralized 128 UHA (hemaglutinant unit) of H₁N₁ influenza virus. With picornavirus, egg wax led to a 256-fold reduction in virus production by L929 cells. Egg wax was not cytotoxic to VERO, MDCK and L929 cell, being observed that the cell morphology was preserved with concentration as high as 2 mg/mL. In addition no genotoxic effect was observed for Vero cells, suggesting a very interesting potential antiviral activity.     

Host association and seasonal activity of Amblyomma americanum (Acari: Ixodidae) in Missouri

From June 1993 through June 1996, 2,260 adult, 4,426 nymphal, and 2,178 larval lone star ticks Amblyomma americanum (L.) were collected in Missouri from vertebrate hosts and by dragging a cloth over vegetation. Prevalence, mean intensity, and relative abundance of each stage varied among hosts. The relative abundance of adult lone star ticks was highest on white-tailed deer, but this stage was also collected from raccoons, opossum, red fox, coyotes, and wild turkey. Nymphs were collected from gray squirrels, eastern cottontail rabbits, opossums, red fox, Carolina wren, and bobwhite quail, but the highest relative abundance occurred on wild turkey, white-tailed deer, and raccoons. Eastern cottontail rabbits, white-tailed deer, raccoons, and squirrels had the highest relative abundance of larval lone star ticks, but they were also found on opossums and wild turkey. The activity of adult lone star ticks was greatest from May through July. The activity for nymphs was highest from May through August, and for larvae, July through September.