Acari community in association with delayed pig carrion decomposition.

Acari community structure and function associated with delayed pig carrion decomposition has not been examined. In this study, 18 swine carcasses were studied in central Texas, USA, during two consecutive summers (2013 and 2014). Samples of ca. 400 g soil were collected from beneath, aside, and 5 m away from each pig carcass over 180 days. Mites from soil samples were extracted using Berlese funnels and identified to order and family levels and classified according to ecological function. In total 1565 and 1740 mites were identified from the 2013 and 2014 soil samples, respectively. Significant differences were determined for mite community structure at order and family levels temporally on carrion (e.g., day 0 × day 14) regardless of treatments and between soil regions where mites were collected (e.g., soil beneath vs. soil 5 m away from carrion). However, no significant differences were found in mite community structure at the order level between pig carrion with and without delayed Diptera colonization (i.e., treatments). Analysis at the family level determined a significant difference across treatments for both summers. Ecological function of mites did not change significantly following the delayed decomposition of pig carcasses. However, detritivores and fungivores were significant indicator groups during the pig carrion decomposition process. Furthermore, 13 phoretic mite species associated with eight forensically important beetle species were documented. Data from this study indicated that the rate of nutrient flow into the soil impacted associated arthropod communities; however, detecting such shifts depends on the taxonomic resolution being applied.

Blood feeding of Ornithodoros turicata larvae using an artificial membrane system.

An artificial membrane system was adapted to feed Ornithodoros turicata (Ixodida: Argasidae) larvae from a laboratory colony using defibrinated swine blood. Aspects related to larval feeding and moulting to the first nymphal instar were evaluated. A total of 55.6% of all larvae exposed to the artificial membrane in two experimental groups fed to repletion and 98.0% of all fed larvae moulted. Mortality rates of first instar nymphs differed significantly depending on the sorting tools used to handle engorged larvae (χ2 = 35.578, P < 0.0001): engorged larvae handled with featherweight forceps showed significantly higher mortality (odds ratio = 4.441) than those handled with a camel-hair brush. Differences in the physical properties of the forceps and camel-hair brush may affect the viability of fragile soft tick larvae even when care and the same technique are used to sort them during experimental manipulations. The current results represent those of the first study to quantify successful feeding to repletion, moulting and post-moulting mortality rates in O. turicata larvae using an artificial membrane feeding system. Applications of the artificial membrane feeding system to fill gaps in current knowledge of soft tick biology and the study of soft tick-pathogen interactions are discussed.

Association of Myianoetus muscarum (Acari: Histiostomatidae) With Synthesiomyia nudiseta (Wulp) (Diptera: Muscidae) on Human Remains.

Synthesiomyia nudiseta (Wulp) (Diptera: Muscidae) was identified during the course of three indoor medicolegal forensic entomology investigations in the state of Texas, one in 2011 from Hayes County, TX, and two in 2015 from Harris County, TX. In all cases, mites were found in association with the sample and subsequently identified as Myianoetus muscarum (L., 1758) (Acariformes: Histiostomatidae). This report represents the first records of a mite associated with S. nudiseta in the continental United States. In particular, this association is believed to be of potential future value in forensic investigations, as it lends new insight into the community structure of colonizers on human remains in indoor environments.

The Gulf Coast tick: a review of the life history, ecology, distribution, and emergence as an arthropod of medical and veterinary importance.

The Gulf Coast tick, Amblyomma maculatum Koch (Acari: Ixodidae), is a unique univoltine ectoparasite of seven vertebrate host classes in the Western Hemisphere that is increasingly recognized as a pest of livestock and wildlife, a vector of pathogens to humans and canines, and a putative vector of Ehrlichia ruminantium, the causal agent of heartwater, a fatal foreign animal disease of ruminants resident in the Caribbean. This review assembles current and historical literature encompassing the biology, ecology, and zoogeography of this tick and provides new assessments of changes in cyclical population distribution, habitat associations, host utilization, seasonal phenology, and life history. These assessments are pertinent to the emergence of A. maculatum as a vector of veterinary and medical importance, and its pest management on livestock and other animals.

Genetic variation in 12S and 16S mitochondrial rDNA genes of four geographically isolated populations of Gulf Coast ticks (Acari: Ixodidae).

Single-strand conformation polymorphism (SSCP) analysis was examined in a 303-bp region of the 16S and 12S mitochondrial rDNA genes to study haplotype frequencies among populations of Gulf Coast ticks collected from Refugio Co., TX, Payne Co., OK, and two sites in Osage Co., KS. Seven haplotypes were identified from the 16S rDNA gene fragment, whereas only two haplotypes were detected from the 12S fragment. Only the results from the 16S rDNA fragment are discussed. Haplotype diversity was greatest in Kansas (site 1), where three of the four haplotypes detected were unique to this site. All Gulf Coast tick populations shared the fourth haplotype. Two haplotypes were determined for Texas and Oklahoma populations, one of which appeared only in Texas, whereas the other was shared. Nei's haplotype diversity (h) indicated that the Texas population was relatively homogeneous (15%), whereas the remaining populations were heterogeneous (42-59%), although the Bonferroni confidence interval found no significant differences (P < 0.05). Nucleotide sequencing of the seven haplotypes and subsequent phylogenetic analysis using neighbor joining showed a monophyletic relationship among these haplotypes. One haplotype, shared by both Oklahoma and Kansas (site 2), was basal to the remaining haplotypes and formed a distinct clade. Two haplotypes, both from Kansas (site 1), formed a unique clade, whereas the remaining four haplotypes were unresolved polytomies.

Fecal NIRS: detection of tick infestations in cattle and horses.

Anti-tick treatments are often applied concurrent to routine livestock management practices with little regard to actual infestation levels. Prescription treatments against ticks on grazing cattle would be facilitated by non-invasive detection methods. One such method is fecal near infrared spectroscopy (NIRS). Four studies utilizing cattle (Bos spp.) and one with horses (Equus caballus) fed varying diets and infested with either Amblyomma americanum, A. maculatum, A. cajennense or Dermacentor albipictus were conducted to determine the ability of fecal NIRS to identify samples from animals with (High stress) and without (Low stress) a tick burden. Discriminant analysis of each individual trial resulted in R(2)>0.80. Similar analyses utilizing all combinations of four studies, predicting group membership in the remaining study, yielded R(2)>0.80, but correct determinations for Low and High tick stress samples of only 53.4 and 60.1%, respectively. All five trials were combined and a random 10 or 25% of the samples were removed from the calibration. As in the previous calibrations, a high degree of discrimination was achieved (R(2)>0.89). The validation samples were correctly identified at 91.7% for Low stress and 96.3% for High stress, respectively. Difficulties in detecting differences in fecal samples due to confounding effects of trial were overcome by combining calibration sets. Overall, differences in fecal NIR spectra apparently due to tick stress were accurately detected across diet, host species, and tick species.

Mating success of two geographically distinct populations of Gulf Coast ticks, Amblyomma maculatum Koch.

Gulf Coast ticks collected from Refugio Co., TX and Osage Co., KS are reproductively compatible despite differences in genetic haplotypes, geographic separation and seasonal phenologies. Two heifers per mating combination (TX males x TX females, KS males x KS females, TX males x KS females, KS males x TX females) were each infested with 360 pairs of Gulf Coast ticks. Only mean pre-oviposition and mean egg conversion efficiency index for the Texas male-Kansas female mating were significantly different (p<0.05) from other mating treatments. These females began oviposition 1-day later and used 4% less body mass toward egg production when compared to site-specific matings. However, the overall trend in reproductive performance of reciprocal tick matings was slightly lower than that of site-specific matings. There appear to be no pre-zygotic barriers to mating among Gulf Coast ticks from these Texas and Kansas populations.

Feeding predilection of Gulf Coast tick, Amblyomma maculatum Koch, nymphs on cattle.

Gulf Coast tick nymphs successfully attached and fed on cattle after being freely released. Six Hereford heifers were each infested with approximately 2000 Gulf Coast tick nymphs, three with a strain originating from Refugio Co., TX, and three with ticks from Osage Co., KS by free release on the head and legs to simulate field acquisition of questing nymphs. Two re-infestations were conducted, the first at 7 days and the second at 28 days. Nymph dispersal was estimated by daily inspection of 22 body areas and removal of engorging ticks from the third to the fifth days post-infestation. Total recovery of engorging Texas nymphs was 3.0, 10.2, and 0% and Kansas nymphs was 21.5, 3.3, and 0% for infestations one, two and three, respectively. Immunological resistance to tick infestation expressed as cellular hypersensitivity was evident against Kansas nymphs in the second infestation and against both tick strains in the third infestation. Ticks removed from the withers, midline, and tail-head areas accounted for 68% of the total nymphs recovered in the first two infestations. Within these areas, nymphs were observed to aggregate in small spots where the hair was less dense or naturally parted and the remainder were found scattered in dense hair.

Simulation of climate-tick-host-landscape interactions: Effects of shifts in the seasonality of host population fluctuations on tick densities.

Tick vector systems are comprised of complex climate-tick-host-landscape interactions that are difficult to identify and estimate from empirical observations alone. We developed a spatially-explicit, individual-based model, parameterized to represent ecological conditions typical of the south-central United States, to examine effects of shifts in the seasonal occurrence of fluctuations of host densities on tick densities. Simulated shifts in the seasonal occurrence of periods of high and low host densities affected both the magnitude of unfed tick densities and the seasonality of tick development. When shifting the seasonal densities of all size classes of hosts (small, medium, and large) synchronously, densities of nymphs were affected more by smaller shifts away from the baseline host seasonality than were densities of larval and adult life stages. When shifting the seasonal densities of only a single size-class of hosts while holding other size classes at their baseline levels, densities of larval, nymph, and adult life stages responded differently. Shifting seasonal densities of any single host-class earlier resulted in a greater increase in adult tick density than when seasonal densities of all host classes were shifted earlier simultaneously. The mean densities of tick life stages associated with shifts in host densities resulted from system-level interactions of host availability with tick phenology. For example, shifting the seasonality of all hosts ten weeks earlier resulted in an approximately 30% increase in the relative degree of temporal co-occurrence of actively host-seeking ticks and hosts compared to baseline, whereas shifting the seasonality of all hosts ten weeks later resulted in an approximately 70% decrease compared to baseline. Differences among scenarios in the overall presence of active host-seeking ticks in the system were due primarily to the degree of co-occurrence of periods of high densities of unfed ticks and periods of high densities of hosts.

Effects of pyriproxyfen on off-host water-balance and survival of adult lone star ticks (Acari: Ixodidae).

Newly engorged nymphs of the lone star tick, Amblyoma americanum (L.), were continuously exposed to 4 microg/cm2 of pyriproxyfen residues in glass vials. Treatment of engorged nymphs (n = 285) resulted in significant molting inhibition, with more than one-fourth (26.7%, n = 76) of nymphs dying before or during ecdysis. Treatment effects were evident among ticks that molted to the adult stage, with 26.7% (n = 76) of females, and 17.9% (n = 51) of males exhibiting moribund physical characteristics (i.e., lethargy; dull, discolored and desiccated cuticles; lacking full locomotor competency). A few molted adult ticks (10 males, four females) were dead upon inspection. Only 11.2% of pyriproxyfen treated, emergent females (n = 32), and 11.5% of treated emergent males (n = 25) from 285 ticks treated as engorged nymphs, exhibited normal physical appearance and possessed a full range of locomotor activity. Treated adult ticks maintained within a desiccating environmental chamber at 0% RH and 23 degrees C, had significantly accelerated whole-body water loss rates in comparison to untreated males and females maintained under the same environmental conditions. Additionally, treated adult ticks maintained under optimal environmental conditions (23 degrees C and >95% RH) sustained 100% mortality within 32 d following assignment to these conditions (or 79 d posttreatment as engorged nymphs), whereas untreated ticks had 0% mortality for the same duration of time. Results demonstrate that continuous exposure of nymphs to pyriproxyfen disrupted molting, and accelerated both whole-body water loss and subsequent mortality among emergent adult ticks.

Effects of sequential infestations of Dermacentor albipictus and Amblyomma americanum (Acari: Ixodidae) on overwintering beef cows in west-central Texas.

Infestations of winter ticks, Dermacentor albipictus (Packard), observed on mature black Angus cows, reached peak levels in January and diminished through March. Infestations of adult lone star ticks, Amblyomma americanum (L.), began in mid-January and increased through May. Cows receiving Ectrin, Taktic, or Deltox treatments on 13 December and 21 February experienced significantly less weight loss and entered the subsequent breeding season with higher average body weight than untreated cows. In a separate study, lactating Brangus and Brangus-cross cows, equally infested by natural populations of these ticks, were provided five supplement treatment regimens, fed individually with quantities adjusted for body weight and condition score. Groups receiving supplementation highest in crude protein and digestible energy lost significantly less weight and experienced the least amount of deterioration in body condition. Performance among these groups was influenced by the amount of digestible energy and the period in which increased levels of digestible energy were fed. Cows receiving the supplement highest in protein coupled with an increase in digestible energy from 10 to 60 Mcal/kg W0.75 on 16 January experienced the smallest average change in condition score and weight parameters.

Artificial feeding of Ornithodoros concanensis (Acari: Argasidae) nymphs on bovine blood and morphological changes in erythrocytes undergoing hemolysis in the tick midgut.

The morphology of bovine erythrocytes undergoing hemolysis in the midgut of the argasid tick Ornithodoros concanensis Cooley & Kohls was examined after feeding nymphal ticks artificially on parafilm and latex membranes. Percentage of successful feeding was significantly higher on parafilm (63%) than on latex (43%) membrane. However, there was no difference in the amount of blood taken per tick. Scanning electron microscopy was used to follow the morphological changes of red blood cells in the tick gut during an 80-h postfeeding period. Erythrocytes converted from normal discocytes to spiculated cells (echinocyte stage III) within 20 h. During the development of spicules (echinocytosis), erythrocytes lost membrane surface area by the release of microvesicles. At 30 h after feeding, the first spherocytes appeared and after 80 h, only smooth spheres of different sizes were present. Reasons for the observed modifications in red blood cell morphology are discussed.

Modeling embryo development and emergence of Boophilus annulatus (Acari: Ixodidae).

Guanine accumulation in Boophilus annulatus (Say) at 15 temperatures (3-42 degrees C) showed embryonic development from 9 to 42 degrees C. Guanine concentrations steadily increased over the period of development. Eggs at 17-36 degrees C achieved hatch (requiring 54-12 d, respectively), and eclosion dates were estimated for larvae developing at 12 degrees C (day 172) and 14 degrees C (day 154) using linear regression. Development rates from 12 to 36 degrees C are described by a six-parameter biophysical model for poikilothermic organisms which defines three temperature development phases characterized by low-temperature (TL, 284.7 degrees K or 11.7 degrees C) and high-temperature (TH, 307.7 degrees K or 34.7 degrees C) enzyme inactivation and a linear region (RHO25, 0.049 day-1) of no temperature inhibition. A model of emergence distribution was derived by fitting a Weibull function to a single distribution representative of the normalized emergence distribution at each temperature.

Pyriproxyfen effects on newly engorged larvae and nymphs of the lone star tick (Acari:Ixodidae).

Newly engorged larvae and nymphs of the lone star tick, Amblyomma americanum (L.), were exposed to 9 treatments of pyriproxyfen in glass vials consisting of dosages of 4, 8, and 16 micrograms/cm2 for 7 d, 14 d, and continuous exposure periods at each concentration. Treatment of newly engorged larvae resulted in decreased molting, altered postmolt defecation, and nymphal survival with results being dose and exposure dependent. Molting inhibition ranged from 35.9 to 68.4%. Successfully molted nymphs were lethargic, exhibited altered defecation patterns, and were short-lived compared with untreated adults. By 65 d after treatment, cumulative inhibition of molting and hastened mortality of molted adults resulted in 82.6-100% control, depending on dosage and exposure. Treatment of newly engorged nymphs showed minimal to no effect on molting; however, adults were lethargic and displayed altered postmolt defecation patterns. Subsequent adult longevity was most dramatically affected with 87.9-100% control achieved by 82-84 d after treatment. Fecal patterns and survivorship were dose and exposure dependent. Estimates of subsequent feeding success of adults treated as engorged nymphs, show reduced capacities of attachment, engorgement and reproduction.

Effects of pyriproxyfen on engorged females and newly oviposited eggs of the lone star tick (Acari:Ixodidae).

Engorged females and 1- to 3-d-old eggs of the lone star tick, Amblyomma americanum (L), were exposed to 9 treatments of pyriproxyfen (4, 8, and 16 micrograms/cm2) in glass vials at exposure periods of 7 d, 14 d, and continuous at each dosage level. Treatment of newly engorged females did not affect the number of females ovipositing, but the number of eggs oviposited decreased as dosage and exposure time increased. Complete inhibition of egg hatch occurred at all treatment levels except that of the lowest dosage and exposure time where 99.9% inhibition was observed. Egg masses from treated females contained eggs that turned a dark amber color and imploded, retained normal shape and color without visible evidence of embryogenesis, or had developed embryos that were unable to emerge. Treatments of 1-to 3-d-old eggs were effective in reducing hatch and larval survivorship to 25 d after emergence only at the continuous exposures of dosages of 4, 8, and 16 micrograms/cm2. Larvae emerging from eggs treated at the lower dosage rates of 0.2 and 0.02 microgram/cm2 were as successful in feeding on chickens and subsequently molting as acetone treated control ticks.

Survival and water-balance characteristics of unfed adult Amblyomma cajennense (Acari: Ixodidae).

Off-host survival, water balance, and cold tolerance of unfed adult, Cayenne ticks, Amblyomma cajennense (F.), were examined to evaluate species characteristics important to zoogeography and off-host ecology. Survivorship decreased when males and females were subjected to progressively drier constant environmental conditions. Average maximum survival was 641.2 and 682.5 d at 85% RH and 23 degrees C (2.98 mm Hg) for males and females, respectively. Mean survival in both sexes was progressively less variable in drier conditions. Slopes of log-linear models of survival days based on saturation deficit (mm Hg) were significantly different between males and females at 50%, but not at 25 or 0%. Whole-body water loss rates for 4-wk-old adults were measured at 0% RH and 23 degrees C until ticks became nonambulatory. The mean whole-body water loss rate of females, 0.06128% h-1, was 11.3% less than for males, 0.06914% h-1. Although nonambulatory ticks appeared dead, >1/2 of the individuals from each sex regained ambulatory status after they were removed from 0% RH and exposed to 96% RH for 24 h. Among these, male ticks averaged 0.44 more recuperative (ambulatory) cycles than females, although, the duration encompassing all recuperative cycles was generally longer for females and on average, females gained 8.16% more weight than males upon each rehydration. Estimates of the mean critical equilibrium activity for males and females were 0.74 av and 0.79 av, respectively. A. cajennense adults were found to be less tolerant to -12.5 degrees C than adult lone star ticks, Amblyomma americanum (L.), whose distribution encompasses more temperate regions. Although A. cajennense exhibit little host preference and are capable of extended off-host survival, the establishment of populations beyond this species zoogeographic distribution may be constrained by an intolerance to cold.

Detection of a spotted fever group rickettsia in Amblyomma cajennense (Acari: Ixodidae) in south Texas.

Thai tick typhus rickettsia (strain TT-118), a spotted fever group rickettsia of indeterminant pathogenicity, was isolated from a mixed pool of larval Ixodes and Rhipicephalus ticks collected from Thailand in 1962. Here we report the surprising finding of a spotted fever group rickettsia with closest sequence homology to the Thai tick typhus rickettsia in Amblyomma cajennense (F.) ticks from south Texas. Sequence analysis was performed on segments of 3 genes that differentiate rickettsial species; all 3 genes sequenced, the 17-kDa, glta, and rompA, when compared with those of other rickettsiae, showed the highest degree of similarity to the Thai tick typhus rickettsia with 99.5, 99.5, and 100% homology, respectively. This is the 1st finding of a rickettsial species in A. cajennense ticks in Texas and the United States. If this rickettsia is pathogenic, exposure to infected A. cajennense ticks may pose a previously unrecognized health risk to people who have been fed upon by these ticks.

Population dynamics of immature Amblyomma maculatum (Acari: Ixodidae) and other ectoparasites on meadowlarks and northern bobwhite quail resident to the coastal prairie of Texas.

A survey of ectoparasites from 219 meadowlarks conducted during 2 consecutive fall-winter periods in a coastal prairie found immature Amblyomma maculatum Koch to be the most abundant parasite. Peak larval infestations occurred in December with 80-100% of collected birds infested and with a monthly mean of up to 34 larvae per bird. Peak nymphal infestations occurred in February or March with 95-100% of birds infested and with a monthly mean of up to 11 nymphs per bird. Seasonal dynamics of these stages offered possible insight into the persistence of A. maculatum in an area long infested with the red imported fire ant, Solenopsis invicta Buren. Four other species of ticks also were collected but in substantially lower numbers; Amblyomma cajennense (F.), Amblyomma inornatum (Banks), Haemaphysalis chordeilus (Packard), and Haemaphysalis leporispalustris (Packard). This appears to be the 1st host record of A. cajennense from meadowlarks. A collection of 17 northern bobwhite quail indicated that most of these birds were infested with A. maculatum but at a lower level than meadowlarks. The collections of 2 species of Mallophaga from meadowlarks and 4 species from the northern bobwhite quail are discussed.

Simulation of rotational grazing to evaluate integrated pest management strategies for Boophilus microplus (Acari: ixodidae) in Venezuela.

Ranchers in Venezuela historically have controlled the cattle-fever tick, Boophilus microplus (Canestrini), with acaricide treatments of cattle but no technical planning. We developed a simulation model to evaluate cattle-tick population dynamics in systematic pasture rotation systems and Integrated Pest Management (IPM) approaches to managing ticks in the tropical dry-forest ecological zone of Venezuela. Model output showed five generations of cattle-ticks produced each year throughout the dry and rainy seasons that occur in this zone. Sensitivity analyses showed disproportionately large changes in on-host B. microplus populations in response to small changes in larval mortality rates, such as those resulting from differences in the innate resistance of cattle to tick parasitism. Simulation results with 1-6 pasture systems suggest that adjusting the graze:rest sequence with systematic rotation among 4-6 pastures could suppress, but not eradicate, tick populations.

Perceptions of veterinary clinics and pest control companies regarding tick-related problems in dogs residing in Texas cities.

OBJECTIVE: To determine the extent and source of tick-related problems encountered by veterinary clinics and pest control company (PCC) clientele experiencing residential tick infestations in urban/suburban environments and to determine which tick-related diseases in dogs were diagnosed and treated at veterinary clinics. DESIGN: Cross-sectional survey. SAMPLE POPULATION: Veterinary clinics and PCC in Dallas/Fort Worth and Austin/San Antonio, Tex. PROCEDURE: Surveys were made into professionally printed booklets and mailed to participants. RESULTS: Dallas/Fort Worth and Austin/San Antonio clinics indicated that tick-related problems comprised 21 and 15%, respectively, of their canine-based business. The most frequently observed species was the brown dog tick. Tick infestations were most common during May through August. Immature tick populations were seen by the greatest number of clinics in May and June, and engorged female ticks were encountered most often in June and July. Ticks were most commonly found around homes and adjacent yards or lots. Greenbelts were perceived by all 4 study groups to be the principal place in the community where ticks were acquired by clients' dogs. Canine ehrlichiosis was the most common tick-related disease diagnosed and treated at clinics, followed by anemia caused by tick infestation. CLINICAL IMPLICATIONS: Identification of ticks is important, because different tick species transmit different disease agents and different ecologic factors may be associated with exposure and subsequent treatment. Knowledge of temporal activity patterns of ticks, where they are acquired and where populations become established, combined with improved cooperative efforts between veterinary clinics and PCC, would aid in more effective control and management of ticks.