The appetence behaviour of two South African paralysis-inducing ixodid ticks

Microhabitat determines uneven distribution of Amblyomma parvum but not of Amblyomma sculptum ticks within forest patches in the Brazilian Pantanal

Environmental distribution of the two most abundant ticks in forest areas in the Brazilian Pantanal was evaluated by CO₂ traps methodology in the wet season (peak of adult ticks) of 2012 and 2013. Adults of Amblyomma parvum were concentrated inside agglomerates of Bromelia balansae, in the border of forest patches. Adults of Amblyomma sculptum occurred in similar numbers both in bromeliad clumps and in bromeliad-free areas. Differential distribution of ticks in this habitat could be associated to the frequent use of bromeliad clumps by wild animals (potential hosts) and to the microclimate conditions inside this vegetation in the Pantanal. It is important to verify whether larvae and nymphs of A. parvum have a similar pattern of distribution in the same areas, during the dry season. These stages are more susceptible to desiccation and their principal hosts, non-volant small mammals, also use these bromeliad areas.

Factors affecting abundance of different stages of the endophilic tick Ixodes anatis in brown kiwi (Apteryx mantelli) shelters

Ixodes anatis is a species of endophilic (nidicolous) tick species parasitizing brown kiwi (Apteryx mantelli). Even though they are endemic to New Zealand like their host, very little is known about these ticks or their population dynamics and relationships with their hosts. We conducted a study from May 2013 to June 2014 to evaluate the effect of shelter location (one of three gullies), habitat (forest, scrub and pasture) and type (tree, soil and surface) on the abundance of the different life stages of I. anatis. In total, 12,172 ticks were collected from 63 shelters, which were sampled monthly for 11 months over the 14 month period. Un-engorged larvae predominated over other stages accounting for 87.2% of the samples collected. We found that location, habitat in which the shelters were located, and the type of shelter were significant predictors of I. anatis abundance. Tree shelters in forests had significantly higher tick abundance than those in scrub and pasture. Tree and soil shelters in general had significantly more ticks than surface shelters. Shelters located in Kauri Bush a drier site, had higher abundances than those in wetter sites. While some of these changes can be explained with the movement of the host, we believe more research needs to be done on the effect of shelters' microclimate on I. anatis' life cycle.

Ambush behavior of the tick Amblyomma sculptum (Amblyomma cajennense complex) (Acari: Ixodidae) in the Brazilian Pantanal

We herein describe the ambush behavior of Amblyomma sculptum (Berlese 1888), a widespread and epidemiologically important tick in Brazil. Along two years of sampling by visual search in the Brazilian Pantanal, A. sculptum ticks were observed on the vegetation and in the leaf litter. Most of the ticks were observed between 10 and 50cm above ground level and less than five percent of the total were positioned below 10cm, indicating that they are seeking for middle or large-sized hosts. In both seasons, vapor saturation deficit was low during the morning. No significant relationship was found between questing ticks and daytime interval of observation or saturation deficit. However, questing tick numbers seem be higher in the end of the morning, when saturation deficit reaches its peak. Behavioral patterns of A. sculptum ticks observed in Pantanal underscore the occurrence of this tick and human contact at green anthropogenic sites. Considering A. sculptum questing behavior, inferences on human behavioral patterns that enhance or avoid contact with ticks are discussed.

CO2 flagging - an improved method for the collection of questing ticks

BACKGROUND

Most epidemiological studies on tick-borne pathogens involve collection of ticks from the environment. An efficient collection method is essential for large sample pools. Our main aim was to evaluate the efficacy of a new method, where traditional flagging was enhanced by the use of CO2 dispersed into the white flannel. The CO2 was spread through a rubber hose network inserted into the flag blanket. The research was conducted in spring, in March-April 2011 in two locations from Cluj County, Romania.

METHODS

The research was conducted in March-April 2011 in two locations from Cluj County, Romania. The flag to be tested contained a fine silicone rubber hose network which dispersed the CO2 in the shaft. On each collection site n=30 samplings were performed. Each sampling consisted in the simultaneous use of both flags (with and without CO2) by two persons. The CO2 concentration level on the flag canvas surface was measured. The efficacy of the method was determined by counting comparatively the total number of ticks and separate developmental stage count.

RESULTS

Using the CO2 improved flag, 2411 (59%) Ixodes ricinus and 100 (53.8%) Dermacentor marginatus ticks were captured, while the CO2-free flag accounted for the collection of 1670 I. ricinus (41%) and 86 (46.2%) D. marginatus ticks. The addition of CO2 prompted a concentration difference on the surface of the flag ranging between 756.5 and 1135.0 ppm with a mean value of 848.9 ppm.

CONCLUSION

The study showed that the CO2 enhanced sweep flag increased the ability of I. ricinus (p<0001) but not of D. marginatus to be attracted to the flag blanket.

Activity periods and questing behavior of the seabird tick Ixodes uriae (Acari: Ixodidae) on Gull Island, Newfoundland: the role of puffin chicks

Questing behavior of Ixodes uriae and their associated seasonal, host-feeding patterns are crucial to our understanding of tick life history strategies and the ecology of diseases that they transmit. Consequently, we quantified questing behavior of nymphs and adult female I. uriae ticks at Gull Island, a seabird colony in Newfoundland, Canada, to examine seasonal variation of off-host and on-host tick activity. We sampled a total of 133 adult Atlantic puffins (Fratercula arctica), 152 puffin chicks, and 145 herring gull (Larus argentatus) chicks for ticks during the breeding seasons of 2004 and 2005. Questing ticks were sampled by dragging a white flannel cloth across the grassy breeding areas during the mo of May, June, July, and August. Nymph questing activity reached a peak during mid-July (79 and 110 individuals/hr in 2004 and 2005, respectively). The prevalence of nymphs and adult female ticks on different seabird hosts varied between years and during the seasons. Puffin chicks had the highest prevalence (above 70% in July) of nymphs in both years and this was correlated with questing activity. Female ticks rarely fed on puffin chicks, but were prevalent on adult puffins and gulls, although prevalence and questing of ticks were not correlated in these hosts. These patterns of off-host and on-host tick activity suggests that I. uriae ticks likely use a combination of questing and passive waiting, e.g., in puffin burrows, to detect hosts, depending on the tick stage and the host species.

Effect of food deprivation on response of the mite, Dermanyssus gallinae, to heat

Freshly blood-fed adult females of the chicken mite Dermanyssus gallinae DeGeer (Acari: Dermanysidae) were food-deprived during 1, 2-3, 8-10, 14-16 and 22-23 days. These mites were tested in groups of 10 to determine their sensitivity to a heat cue delivered for a 60 s period under controlled laboratory conditions (24 degrees C, simulated dark conditions of 2 lx). Immobile mites were videotaped and start of activation (for individual mites) and percentage of mites activated in the 60 s period were related to temperature changes. Mites were activated with temperature gradients as low as 0.003-0.005 degrees C/s. Mites that had fed the previous day had a significantly lower activation (20%) than other groups. Activation was highest at 2-3 days (60%) and 8-10 days (75%) post-feeding. Activation declined significantly to 45% at 14-16 days and to 30% at 22-23 days post-feeding. Activation patterns probably reflect mite physiological condition and declining responsiveness to heat cues concomitant with starvation and higher risks associated with activation in the prolonged absence of a host.

Influence of heat and vibration on the movement of the northern fowl mite (Acari: Macronyssidae)

Heat and vibration are common host-generated cues that ectoparasites use to orient to hosts. Three experiments evaluated effects of heat and vibration on the movement of northern fowl mite, Ornithonyssus sylviarum (Canestrini & Fanzago). Individual arrested mites in an isolation chamber always initiated movement (walking) after substrate vibration (7.8-min walking duration), but only initiated movement 50% of the time (2.8-min walking duration) upon exposure to a 3 degrees C heat fluctuation. Heat fluctuation in combination with vibration extended the period of activity by approximately 50% (11.6-min walking duration) compared with activity initiated by vibration alone. Mites with longer time off-host moved for shorter durations. In a choice test, individual mites consistently moved closer to a 35 degrees C heat source 1 or 6 mm away, but not to a heat source 11 mm away. In a circular arena, mites were able to orient accurately to a 35 degrees C heat source and reached the arena edge almost 4 times faster (11.2 s) than mites without a heat source (41.2 s). These results suggest that northern fowl mite is capable of directed thermo-orientation, as well as modulation of activity depending on the type of sensory information perceived. The adaptive significance of this orientation for a "permanent" ectoparasite is discussed.

Control of Karoo paralysis ticks through vegetation management

Karoo paralysis, caused by feeding Ixodes rubicundus females, is a major disease of small stock in South Africa. Control methods currently practised are almost exclusively chemical based. To limit overdependance on chemicals, vegetation management was investigated as a possible method for control, to be incorporated in an integrated tick management system. Laboratory and field experiments were conducted to determine, firstly, the extent of vertical migration and survival of ticks on long and short copper rods which simulated grasses as questing substrates; secondly, the infestation burdens of sheep exposed to similar tick challenges in pens with long and short grass; and thirdly, the effect of trimming the lower crown line of wild olive trees, simulating the browsing effect of goats, on tick density in the immediate environment of the trees. When ticks were exposed to optimal ( > 45 cm) and sub-optimal ( < 10 cm) length rods on which to quest, the extent of vertical migration over extended periods of time (up to 87 days) was significantly higher (P < 0.001) for the ticks exposed to long rods. Also, almost 3 times as many ticks exposed to long rods survived compared to those exposed to short rods. Sheep exposed to long grass were infested by twice as many ticks compared to those exposed to short grass. Tick density at modified wild olive trees (Olea europaea africana) (0.027 ticks/m2) differed significantly (P < 0.05) from that at control trees (0.088 ticks/m2). It is recommended that coarse grazers such as cattle and horses should be used to graze down long grasses before sheep are introduced into camps known to be infested with I. rubicundus. Similarly, domestic goats can, through their browsing effect on shrubs and trees, modify the vegetation and as such play an important role in an integrated tick management system.

Improvement of field sampling methods for adult Karoo paralysis ticks, Ixodes rubicundus (Acari: Ixodidae), through addition of host odour

The responsiveness of Ixodes rubicundus ticks on questing substrates and the success of their attachment to non-living substrates were investigated. The purpose of this study was to relate responsiveness to conditions of temperature and humidity, to compare the efficacy of flagging and dragging methods to estimate the size of populations of adult I. rubicundus in the field, and to determine the possible influence of host odour on the efficacy of these methods. Responsiveness was tested under varying conditions of temperature and humidity under field conditions, and the same ticks were used to determine the duration of attachment to a flannel cloth, either impregnated with host odour from sheep wool or without it. Flagging and dragging methods were compared under laboratory conditions with cloths either treated with host odour or not. Within the range of ambient temperatures recorded during this study (7-25 degrees C) most of the ticks (86%) were responsive. No obvious relationship between temperature, relative humidity and responsiveness of ticks was evident. Ticks remained on average 32.9 seconds (n = 64) on cloth treated with host odour compared to 9.1 seconds (n = 54) on untreated cloth. Flagging was 1.5-1.7 times as effective as dragging and treatment of the cloths with host odour increased the efficacy 2.4 (dragging) to 2.8 (flagging) times. The reactions of ticks to external stimuli should, therefore, be taken into account to maximize field sampling success.