Pete D. Teel

The Gulf Coast Tick: A Review of the Life History, Ecology, Distribution, and Emergence as an Arthropod of Medical and Veterinary Importance

ABSTRACT 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.

Evaluation of Transovarial Transmission and Transmissibility of Ehrlichia chaffeensis (Rickettsiales: Anaplasmataceae) in Amblyomma americanum (Acari: Ixodidae)

Abstract It has long been assumed that Ehrlichia chaffeensis (Anderson, Dawson & Wilson), is not transmitted transovarially in the lone star tick vector Amblyomma americanum (L.). To test this hypothesis, three beagle dogs, Canis familiaris (L.) (Carnivora: Canidae), were subcutaneously infected with E. chaffeensis (Arkansas strain). Uninfected nymphal lone star ticks were placed on the infected dogs and allowed to feed to repletion. These nymphal ticks were allowed to molt, and five of five adult female ticks sampled were confirmed to be infected by polymerase chain reaction (PCR). Forty infected adult ticks, the majority of which were female with several males included to stimulate feeding, were then placed on two uninfected dogs. Fourteen females were removed early and the rest were allowed to feed to repletion. After feeding to repletion, the six remaining females detached and two of these females were tested preoviposition, whereas the remaining four were allowed to lay eggs. All six of these fully engorged females tested negative by PCR. The egg clutches laid by four engorged adult females, and the larvae that hatched from these eggs along with larvae from a previously untested egg clutch, were shown to be uninfected by PCR. This seems to support the long-held assumption of lack of transovarial transmission. Also of interest, we found that these PCR-confirmed infected adult ticks reared in the laboratory did not transmit E. chaffeensis to uninfected dogs.

One Health approach to identify research needs in bovine and human babesioses: workshop report

BackgroundBabesia are emerging health threats to humans and animals in the United States. A collaborative effort of multiple disciplines to attain optimal health for people, animals and our environment, otherwise known as the One Health concept, was taken during a research workshop held in April 2009 to identify gaps in scientific knowledge regarding babesioses. The impetus for this analysis was the increased risk for outbreaks of bovine babesiosis, also known as Texas cattle fever, associated with the re-infestation of the U.S. by cattle fever ticks.ResultsThe involvement of wildlife in the ecology of cattle fever ticks jeopardizes the ability of state and federal agencies to keep the national herd free of Texas cattle fever. Similarly, there has been a progressive increase in the number of cases of human babesiosis over the past 25 years due to an increase in the white-tailed deer population. Human babesiosis due to cattle-associated Babesia divergens and Babesia divergens-like organisms have begun to appear in residents of the United States. Research needs for human and bovine babesioses were identified and are presented herein.ConclusionsThe translation of this research is expected to provide veterinary and public health systems with the tools to mitigate the impact of bovine and human babesioses. However, economic, political, and social commitments are urgently required, including increased national funding for animal and human Babesia research, to prevent the re-establishment of cattle fever ticks and the increasing problem of human babesiosis in the United States.

Integrated strategy for sustainable cattle fever tick eradication in USA is required to mitigate the impact of global change

The ticks Rhipicephalus (Boophilus) annulatus and R. (B.) microplus, commonly known as cattle and southern cattle tick, respectively, impede the development and sustainability of livestock industries throughout tropical and other world regions. They affect animal productivity and wellbeing directly through their obligate blood-feeding habit and indirectly by serving as vectors of the infectious agents causing bovine babesiosis and anaplasmosis. The monumental scientific discovery of certain arthropod species as vectors of infectious agents is associated with the history of research on bovine babesiosis and R. annulatus. Together, R. microplus and R. annulatus are referred to as cattle fever ticks (CFT). Bovine babesiosis became a regulated foreign animal disease in the United States of America (U.S.) through efforts of the Cattle Fever Tick Eradication Program (CFTEP) established in 1906. The U.S. was declared free of CFT in 1943, with the exception of a permanent quarantine zone in south Texas along the border with Mexico. This achievement contributed greatly to the development and productivity of animal agriculture in the U.S. The permanent quarantine zone buffers CFT incursions from Mexico where both ticks and babesiosis are endemic. Until recently, the elimination of CFT outbreaks relied solely on the use of coumaphos, an organophosphate acaricide, in dipping vats or as a spray to treat livestock, or the vacation of pastures. However, ecological, societal, and economical changes are shifting the paradigm of systematically treating livestock to eradicate CFT. Keeping the U.S. CFT-free is a critical animal health issue affecting the economic stability of livestock and wildlife enterprises. Here, we describe vulnerabilities associated with global change forces challenging the CFTEP. The concept of integrated CFT eradication is discussed in reference to global change.

The neuropeptidomics of Ixodes scapularis synganglion

Ticks (Ixodoidea) likely transmit the greatest variety of human and animal pathogens of any arthropod vector. Despite their medical significance little data is available about the messenger molecules in the central nervous system that coordinate all physiological processes in these animals, including behaviour. In our study, we performed the first comprehensive neuropeptidomic analysis of a tick species by using MALDI-TOF mass spectrometry. Specifically we analyzed the neuropeptides in the synganglion of Ixodes scapularis. The forthcoming sequence of the genome of this species will represent the first genomic analysis of a member of the large subphylum Chelicerata. For our approach we used information from predicted neuropeptide precursor sequences found in EST databases [Christie, AE. Neuropeptide discovery in Ixodoidea: an in silico investigation using publicly accessible expressed sequence tags. Gen Comp Endocrinol 2008;157:174-185] as well as data obtained by complete de novo sequencing. The direct tissue profiling yielded 20 neuropeptides from 12 neuropeptide precursors. The sequences of these neuropeptides are not as unique as predicted; a comparison with the peptidome of other invertebrates shows a close relationship with insect neuropeptides. This work will provide a resource for studying tick neurobiology and will hopefully also help to identify novel targets for tick and tick-borne disease control.

Simulation of host-parasite-landscape interactions: influence of season and habitat on cattle fever tick (Boophilus sp.) population dynamics

Integration of temporal and spatial factors controlling host-landscape interactions is essential to development of systems perspectives important to the management of animal parasites. A simulation model based upon factors regulating distribution and population dynamics of cattle fever ticks, Boophilus annulatus and B. microplus, on rangelands of the Northeastern Mexico-United States border region was found to reasonably represent interactions of season and habitat type. Three submodels represent tick development on cattle, tick development in the environment, and cow movement among three different habitat types. Simulated populations in grass tended to be smaller but with more abrupt peaks than those in mesquite and mixed-brush canopied habitats. Three generations were produced in grass from infestations beginning in January. Generations were less well marked in mesquite and mixed-brush due to the comparatively extended survivorship of larvae in these habitats. Sensitivity analysis of host-larvae encounter rate showed the model to be highly sensitive to this variable when all other factors are constant and demonstrated that utilization of a landscape by host animals is a powerful determinant in Boophilus population dynamics.

Simulation of host-parasite-landscape interactions: influence of season and habitat on cattle fever tick (Boophilus sp.) population dynamics in rotational grazing systems

Abstract Explicit consideration of spatial and temporal factors regulating host-parasite-landscape interactions is basic to understanding systems perspectives for the management of animal parasites. A simulation model of cattle fever tick, Boophilus annulatus and B. microplus, population dynamics on rangelands of the northeastern Mexico-United States border region was modified to examine spatial and temporal dynamics of ticks in rotational grazing systems. Five short-duration grazing rotations in an eight-pasture system were evaluated on rangeland landscapes dominated by uncanopied grass, mesquite canopied grass and mixed-brush canopied grass. Infestations of the grazing system were initiated by introducing infested cattle in either fall or spring. Grazing system infestations in mesquite and mixed brush canopied grass persisted longer than those in uncanopied grass and were characterized by more frequent reinfestations of both pastures and cattle over the two-year simulations. Infestations initiated in fall were generally of longer duration than those initiated in spring due in part to longer incubation periods for tick eggs. Temporal dynamics of infestations by pasture were evaluated numerically and graphically. These analyses show that gaps and discontinuities of infestations within individual pastures over the course of the fall- and spring-initiated simulations reflect host-parasite-landscape interactions affecting tick distribution and survival.

Amblyomma imitator ticks as vectors of Rickettsia rickettsii, Mexico.

Real-time PCR of Amblyomma imitator tick egg masses obtained in Nuevo Leon State, Mexico, identified a Rickettsia species. Sequence analyses of 17-kD common antigen and outer membrane protein A and B gene fragments showed to it to be R. rickettsii, which suggested a potential new vector for this bacterium.

Molecular and biological characterization of the Amblyomma americanum organic anion transporter polypeptide.

SUMMARY The organic anion transporting polypeptides (Oatps in rodents and other organism; OATPs in human) are Na+-independent transporters that shuttle a wide range of endogenous and xenobotic amphipathic compounds across plasma membranes. We previously discovered an Amblyomma americanum tick (Aam) Oatp cDNA among genes that were upregulated or induced in ticks that were stimulated to start feeding. In this study, we have characterized a 2860 bp full-length cDNA that encode a 724 amino acid putative protein. Bioinformatics and hydropathy analyses revealed that, in addition to the kazal-type serine proteinase inhibitor motif, AamOatp possess typical features that characterize the Oatp/OATP protein family, including 12 transmembrane (TM) domains, the consensus amino acid motif D-X-RW-(I,V)-GAWW-X-G-(F,L)-L and 11 consensus cysteine residues in the large extracellular domain between TM9 and TM10. AamOatp is constitutively and ubiquitously expressed, as determined by RT-PCR amplification of the transcript, in all organs of ticks that fed for 1–7 days. Analysis of the normalized transcript abundance revealed that from days 1 to 5 of feeding, AamOatp mRNA expression in the midgut (MG) was 60–80-fold higher than levels found in the salivary gland (SG), ovary (OV) and carcass (CA). By contrast, by day 7 of feeding, the AamOatp mRNA was 60–80-fold more strongly expressed in the OV than in the SG, MG and CA. These data strongly indicate that changing physiological needs during the tick feeding process influences transcriptional regulation of AamOatp. Our data also show that RNAi-mediated suppression of the AamOatp caused ticks to obtain smaller blood meals, which consequently resulted in ticks laying fewer eggs. The results are discussed in the context of AamOatp as a potential pharmacological or anti-tick vaccine target.

Assessment of the Geographic Distribution of Ornithodoros turicata (Argasidae): Climate Variation and Host Diversity

Background Ornithodoros turicata is a veterinary and medically important argasid tick that is recognized as a vector of the relapsing fever spirochete Borrelia turicatae and African swine fever virus. Historic collections of O. turicata have been recorded from Latin America to the southern United States. However, the geographic distribution of this vector is poorly understood in relation to environmental variables, their hosts, and consequently the pathogens they transmit. Methodology Localities of O. turicata were generated by performing literature searches, evaluating records from the United States National Tick Collection and the Symbiota Collections of Arthropods Network, and by conducting field studies. Maximum entropy species distribution modeling (Maxent) was used to predict the current distribution of O. turicata. Vertebrate host diversity and GIS analyses of their distributions were used to ascertain the area of shared occupancy of both the hosts and vector. Conclusions and Significance Our results predicted previously unrecognized regions of the United States with habitat that may maintain O. turicata and could guide future surveillance efforts for a tick capable of transmitting high–consequence pathogens to human and animal populations.