Prospective survey of tick paralysis in dogs

OBJECTIVE: To obtain information on tick paralysis in dogs, including the nature of disease, host signalment, tick-host relationship, treatment, disease progression and recovery, and preventive measures. DESIGN: A prospective survey of 577 dogs affected by tick paralysis was conducted during 1998. Forty-two veterinary clinics along the eastern coast of Australia were instructed to complete survey forms for the first 15 dogs that presented with tick paralysis during September to November. RESULTS: Five percent of dogs died from tick paralysis. Younger dogs were more likely to survive. Long coat length was associated with a greater tick burden but not greater tick size, whereas coat thickness had no bearing on either. Dogs with mild disease recovered more quickly from tick paralysis. Respiratory and gait scores reflected disease severity and were good prognostic indicators. The size of the tick did not reflect the severity of the clinical condition it induced in the host. No method of tick removal or in situ treatment improved recovery time or reduced mortality. However, the time spent in hospital was significantly less for dogs from which the live tick was manually removed. Inspiratory stridor, evident in some dogs with tick paralysis, was not related to tick attachment on the neck. The use of acepromazine maleate or dexamethasone did not reduce recovery time or mortality. Increasing the dose of tick antitoxin serum (TAS) above 0.1 mL/kg had no effect on mortality or recovery time. Dogs with severe disease that received an additional dose of TAS were significantly less likely to survive. Subcutaneous use of TAS at the site of tick attachment was of no benefit in reducing mortality or time to initial clinical improvement. A registered preventative product had not been used on the majority of dogs. Clipping the coat to search for ticks did not reduce mortality. CONCLUSIONS: Therapy needs to address cardiopulmonary dysfunction that may be due directly to the effect of tick toxin and not just respiratory compromise caused by progressive respiratory muscle failure.     

A ten-year review of commercial vaccine performance for control of tick infestations on cattle

Ticks are important ectoparasites of domestic and wild animals, and tick infestations economically impact cattle production worldwide. Control of cattle tick infestations has been primarily by application of acaricides which has resulted in selection of resistant ticks and environmental pollution. Herein we discuss data from tick vaccine application in Australia, Cuba, Mexico and other Latin American countries. Commercial tick vaccines for cattle based on the Boophilus microplus Bm86 gut antigen have proven to be a feasible tick control method that offers a cost-effective, environmentally friendly alternative to the use of acaricides. Commercial tick vaccines reduced tick infestations on cattle and the intensity of acaricide usage, as well as increasing animal production and reducing transmission of some tick-borne pathogens. Although commercialization of tick vaccines has been difficult owing to previous constraints of antigen discovery, the expense of testing vaccines in cattle, and company restructuring, the success of these vaccines over the past decade has clearly demonstrated their potential as an improved method of tick control for cattle. Development of improved vaccines in the future will be greatly enhanced by new and efficient molecular technologies for antigen discovery and the urgent need for a tick control method to reduce or replace the use of acaricides, especially in regions where extensive tick resistance has occurred.     

Lifestyle,habitat and farmers' risk of exposure to tick bites in an endemic area of tick‐borne diseases in Hungary

Controlling tick bites on farmers is important to the management of tick‐borne diseases and occupational health risks in agriculture. Based on an extensive household survey conducted between June and August 2015 with 219 farmers from western Hungary where tick‐borne diseases are endemic, we analysed the pattern of farmers' self‐reported contacts with ticks and investigated the potential interactions between farmers, landscape and the risk of exposure to tick bites. We developed a lifestyle typology based on farmers' socioeconomic profiles, farming objectives and time use patterns, and a habitat typology describing different configurations of tick habitats and agricultural areas in place of farming. We found no relationship between tick exposure risk and self‐prevention. The lifestyle typology could be used to classify the risk of tick bites and the adoption of prevention measures into different levels, the difference between which could further be modified by the habitat typology. Our results suggest that (i) farmers who are frequently engaged in outdoor recreations and (ii) part‐time and inexperienced farmers who have lower rate of preventive actions are likely to experience greater exposure to tick bites either in less cultivated, semi‐natural habitats or in agricultural landscape with highly diverse land uses. Future disease prevention practices should take into consideration the interaction of lifestyle and habitat and the need to associate different farmer groups with different landscape configurations.     

Molecular genetic approaches for identifying the basis of variation in resistance to tick infestation in cattle

In recent years there has been renewed interest in the adaptation of cattle to challenging environments, largely driven by advances in genomic methods. The current interest in tick resistance is understandable given the major production and welfare implications of tick infestation in tropical and subtropical zones where around 70% of beef cattle are located. Heritability for tick burden in cattle has been shown to range about 0.30, which is sufficient to result in the success of some programs of selection for tick resistance in cattle. Gene-expression studies strongly indicate that both immune and non-immune mechanisms are associated with tick resistance in cattle. Recent quantitative-trait mapping studies have identified chromosome segments and single nucleotide polymorphisms associated with tick burden, but no causal variant has been identified so far. Most of the genetic markers identified for tick burden explain a relatively small proportion of the variance, which is typical of markers for quantitative traits. This leads to the conclusion that panels of multiple markers for tick resistance rather than a single marker will most likely be developed, possibly involving specific panels for zebu or taurine breeds, which could be used for future selection and breeding programs in cattle.     

High-resolution predictive mapping for Boophilus annulatus and B. microplus (Acari: Ixodidae) in Mexico and Southern Texas

In this study we use high-resolution satellite imagery to map habitat suitability for both Boophilus annulatus and B. microplus over an area covering parts of Texas and northeastern Mexico. The habitat for these tick species covers widely different regions. B. microplus finds satisfactory abiotic conditions in wet coastal habitats, whereas B. annulatus finds suitable habitat in the drier inner parts of southwestern Texas and northern Mexico; the two species have very different habitat requirements. We use habitat topology and data concerning abiotic habitat suitability to understand the effects of habitat configuration on tick abundance. This is achieved using traversability (habitat permeability) and recruitment (tick abundance at the patch level) to produce a model that computes the abundance of ticks at the patch level. Results from the computation are then compared with actual data on tick outbreaks at the Texas-Mexico border, as a test of the agreement between actual tick captures and abundance model predictions.     

Tick control: thoughts on a research agenda

Tick control is critical to the control of tick borne disease, while the direct impact of ticks on livestock productivity is also well known. For livestock, tick control today rests overwhelmingly on the twin approaches of genetics and chemical acaricides, although the disadvantages and limitations of both are recognized. The achievement of the full potential of vaccination, the application of biocontrol agents and the coordinated management of the existing technologies all pose challenging research problems. Progress in many areas has been steady over the last decade, while the acquisition of molecular information has now reached a revolutionary stage. This is likely to have immediate impact on the identification of potential antigens for improved vaccines and novel targets for acaricide action. In many circumstances, the rate limiting step in making scientific progress will remain unchanged, namely the resource constraint on evaluating these appropriately in large animals. For other approaches, such as the use of biocontrol agents, the limitation is likely to be less in the identification of suitable agents than in their delivery in an efficient and cost effective way. Our scientific understanding of the molecular basis for the tick vector-tick borne disease interaction is in its infancy but the area is both challenging and, in the long term, likely to be of great practical importance. What is arguably the most difficult problem of all remains: the translation of laboratory research into the extremely diverse parasite control requirements of farming systems in a way that is practically useful.     

Forecasting habitat suitability for ticks and prevention of tick-borne diseases

Climate and vegetation are the major factors affecting the distribution of ticks. Consequently, spatial distributions can be analysed by statistical methods that look for correlations between abiotic factors and known data about tick presence/absence. Remote sensing features can be obtained from a wide database of sensors with different characteristics, then applied to the problem of mapping prediction of tick distribution. Some studies had demonstrated that the use of these abiotic variables from satellite imagery has biological significance, therefore statistical accuracy of these distribution models can be interpreted under an ecological framework. Furthermore, models can be linked to these predictive maps, enabling the forecast of spatial and temporal dynamics of ticks, looking for seasonal patterns of activity and accurate use of acaricide treatments.     

Rhipicephalus (Boophilus) microplus embryo proteins as target for tick vaccine

Rhipicephalus (Boophilus) microplus is one of the most widely distributed tick in the world. The control of the parasite is based mainly on the use of chemical acaricides, which are produced from a limited set of molecules. These drugs induce selection of acaricide-resistant ticks, and are an important source of environmental pollution. An approach based on anti-tick vaccines may circumvent these obstacles. Characterization of the physiological function of tick molecules may be useful to develop new vaccines. Previously, we reported the ability of some tick proteins as inducers of protective immune response. Vaccination studies using tick proteins like native (nBYC), recombinant (rBYC) egg-yolk aspartic endopeptidase and cysteine endopeptidase (VTDCE) from R. microplus and glutathione S-transferase (Hl-GST) from Haemaphysalis longicornis demonstrated the immunogenicity and antigenicity of these proteins in bovines. Eventually, immunization with these proteins triggered a partial immune response against R. microplus infestation in cattle, manifested mainly as a reduction in egg fertility (7.7% and 13.9% for nBYC, 5.9% for rBYC; 4.7% for VTDCE, 7.9% for Hl-GST), and in the number of fully engorged ticks (18.2% for rBYC, 14.6% for VTDCE, 53% for Hl-GST). The data so far obtained suggest that these proteins have potential to be used as antigens in an anti-tick vaccine. Other proteins involved in tick embryogenesis also have this potential, like THAP and BmCl1, which are enzymes with key roles in vitellin and hemoglobin hydrolysis. Moreover, the identification of analogous proteins present in other tick species may bring information about the way to develop a vaccine against multiple tick species which can help to solve the problem faced by numerous countries where animals are parasitized by more than one tick species. The aim of the present review is to comprehensibly summarize the data obtained in the last few years by our collaborative research, discussing the efforts we have made to find antigens efficient enough for a cattle tick-controlling vaccine. This review discusses tick physiology studies aimed at the selection of possible targets, characterization of the selected proteins with emphasis on their biochemical and immunological aspects and results of vaccine trials on bovines.     

Factors influencing heartworm,flea, and tick preventative use in patients presenting to a veterinary teaching hospital

The introduction of modern heartworm, flea, and tick preventatives has provided a safe and effective means of controlling companion animal endoparasites, but achieving good owner compliance remains an ongoing challenge for the veterinary profession. Based on a sample of patients from the veterinary teaching hospital at the University of Pennsylvania, this study retrospectively examined factors associated with preventative use and areas of potential weakness in client communication. Between 1999 and 2006, records of 5276 canine and 1226 feline patients were searched for signalment, survey results for heartworm, flea, and tick preventative use, date of visit, presenting complaint, vaccination history, and owner zip code. Data were analyzed using bivariate and multivariate techniques. Overall, only 13–23% of patients were questioned about heartworm, flea, or tick preventative use during routine medical history taking. Patients with a prior history of parasites, younger patients, or those presenting with signs of cardiac disease were no more likely to be questioned about preventative use than healthy animals. Patients presenting to a specialty service were also less likely to be questioned. Approximately 74–79% of dogs and 12–38% of cats in the sample were on preventative products at any given time. There was a distinct seasonality to preventative use corresponding to the heartworm transmission season from June through November in the northeastern United States. Only 50% of patients seen for a yearly physical examination in winter were reported to be using preventative products when surveyed later in the year, compared to the roughly 85% on patients in heartworm preventatives when they received their routine physical examination in spring. Month of presentation and neuter status were the only signalment factors significantly (P < 0.05) associated with preventative use in the multivariate analysis. Findings from this study emphasize target areas for increasing owner compliance.     

Accumulation of acaricide resistance mechanisms in Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) populations from New Caledonia Island

Rhipicephalus (Boophilus) microplus has been pesticide-controlled for several decades in the pacific island of New Caledonia. Since 1996, pesticide-control has been based on either deltamethrin (Butox) or amitraz (Taktic) in herds harbouring deltamethrin-resistant ticks. In this island, the first R. microplus deltamethrin- and amitraz-resistances were detected in 1992 and 2003, respectively. Using LPT bioassays, we have undertaken to update data regarding the geographical distribution and the physiological diversity likely to be involved in these resistances. We confirmed that after 17 years of intensive use of deltamethrin, several resistances of moderate levels (<30-fold) have evolved and/or diffused in any part of the island. We also evidenced that amitraz-resistant phenotypes have recently evolved in diverse western tick populations, although none has reached fixation in any tick population yet. According to synergists bioassays, the physiological changes involved in amitraz-resistance in New Caledonia would involve target modification and detoxifying P450 cytochrom oxydase(s). It may also involve detoxifying esterase(s) although this later point will need confirmation on samples bearing higher frequency of resistant phenotypes. Results are discussed with regard to the local evolutionary dynamics of resistance.     

A survey of cattle producers in the Boophilus microplus endemic area of Queensland to determine attitudes to the control of and vaccination against tick fever

SUMMARY: A survey by mail was used to determine the views of beef producers in the Boophilus microplus endemic area of Queensland on the control of and vaccination against tick fever. Data from 448 questionnaires were analysed, representing 2.7% of beef producers in the survey area. Producers considered buffalo fly ( Haematobia irritans exigua ) infestation as the most important problem whereas tick fever ranked sixth overall. Private veterinarians were regarded as the most important source of information on vaccines for cattle followed by a weekly rural newspaper. From the survey we estimate that about 33% of producers used the tick fever vaccine produced by the Tick Fever Research Centre of Queensland Department of Primary Industries but there were significant (P < 0.05) variations between regions and herds. Large herds (≥ 400 head) in south-east Queensland were the most likely to be vaccinated against tick fever. Of the producers who did not use the vaccine, over 70% replied that there was no need to vaccinate because of the low risk of the disease in their herds. In 52% of unvaccinated herds the treatment of animals with acaricide was considered the most important means of tick fever control and 61% of these herds comprised Bos indicus x Bos taurus or Bos indicus cattle.     

The potential use of fractals in epidemiology

For diseases that are transmitted through parasitic vectors (e.g. tick-borne diseases), the potential distribution and impact of such diseases can be anticipated by studying the distribution of their vectors. Vector distribution is a matter of suitable habitat, which is the sum of a wide range of environmental factors. From remotely sensed data, it is possible to distinguish areas that will provide the most beneficial habitat(s) for a given tick species. The key point is that such data come in the form of patches. The stability of these patches, and therefore that of the tick vectors and the diseases that they transmit, can be mathematically measured using fractal dimensions (D). These fractal dimensions can then be directly related to a non-Markovian (i.e. history dependent) rate of asymptotic decay (H) by using the equation (D=2−H). It is this rate of decay (H) that measures the stability of a given patch(es) of tick habitat(s). If a time series of remotely sensed data is available, changes in the stability (H) can be checked over time. Ultimately, fluctuations of these patches of suitable habitats suggest changes in the tick, and therefore disease, populations. Such fluctuations could destabilize enzootically stable disease populations, or introduce the vectors and diseases into previously naive herds.

As an example of this fractal based measurement of habitat stability, this paper presents empirical evidence of the stability of grass patches in a communal land in Zimbabwe, using data from an aerial photograph. Beyond the practical aspects of measuring the patches, and obtaining their H values, the test data demonstrate that there are at least two distinctive, size based, dynamical systems within the whole set of patches. Generally, patches of a larger size are mathematical less stable than those of a smaller size. The next research objective for the use of such a mathematical tool is to take the concept and apply it on an even larger scale, with the first step undoubtedly being to define what environmental factors constitute suitable habitats for the important tick vector species.     

Control of ticks

A number of different acaricides provide highly effective control of tick populations on dogs and cats. These acaricides are formulated as sprays, dips, dusts, or shampoos for use on the animal. Further protection of the animal from reinfestation with ticks can be achieved with the use of acaricide-impregnated flea and tick collars. Some of these acaricides are registered with the EPA for indoor and outdoor use as controls for free-living populations of ticks. Caution should be used when applying these materials. The label directions for the application of the acaricide and disposal of the acaricide containers should always be followed. Removal of underbrush and leaf litter, thinning trees, and frequently mowing grasses help reduce the number of free-living ticks. Any reduction in the amount of wildlife food sources and cover areas potentially decreases populations of ticks and thus reduces the potential of these ticks parasitizing a dog or cat. Application of an acaricide for area-wide control of free-living ticks in the spring, summer, and autumn also reduces the number of ticks. New approaches to area-wide control of ticks by use of acaricides that are focused on controlling the ticks attached to small mammal hosts are discussed. Although research has shown that reductions in tick numbers can be achieved using these methods, acceptance of these methods by regulatory agencies and the public requires further research.     

The brown dog tick, Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae): from taxonomy to control

Rhipicephalus sanguineus, commonly known as the brown dog tick, is a three-host tick that feeds primarily on dogs and occasionally on other hosts, including humans. R. sanguineus ticks are widely distributed around the world and they are known vectors of pathogens, such as Babesia canis, Ehrlichia canis, and Rickettsia conorii. The increasing number of cases of human parasitism by R. sanguineus ticks reported in the literature indicates that the interaction between humans and R. sanguineus ticks may be more common than it is actually recognized. The indiscriminate use of acaricides is an emerging problem worldwide and has led to the selection of acaricide resistant tick strains. In this article, the medical and veterinary importance, taxonomy, biology, and ecology of R. sanguineus ticks around the world are reviewed. It also discusses the current strategies for the control of R. sanguineus, highlighting the potential risks associated to the improper use of acaricides, such as environmental pollution and toxicity to humans and other non-target organisms (e.g., tick predators).     

Pet ownership increases human risk of encountering ticks

We examined whether pet ownership increased the risk for tick encounters and tickborne disease among residents of three Lyme disease‐endemic states as a nested cohort within a randomized controlled trial. Information about pet ownership, use of tick control for pets, property characteristics, tick encounters and human tickborne disease were captured through surveys, and associations were assessed using univariate and multivariable analyses. Pet‐owning households had 1.83 times the risk (95% CI = 1.53, 2.20) of finding ticks crawling on and 1.49 times the risk (95% CI = 1.20, 1.84) of finding ticks attached to household members compared to households without pets. This large evaluation of pet ownership, human tick encounters and tickborne diseases shows that pet owners, whether of cats or dogs, are at increased risk of encountering ticks and suggests that pet owners are at an increased risk of developing tickborne disease. Pet owners should be made aware of this risk and be reminded to conduct daily tick checks of all household members, including the pets, and to consult their veterinarian regarding effective tick control products.     

Seasonal pattern of tick load in Bunaji cattle in the subhumid zone of Nigeria

The seasonal pattern of tick load on Bunaji cattle under traditional management in northern Nigeria was observed over 12 months to investigate the possibilities of strategic use of acaricide. Ticks were removed 2-3 times weekly by hand from 16 animals, counted and the species determined. Tick load was low in the dry season (2-5 ticks per animal per week), increased after the onset of the first scattered rains, reached a peak (40 ticks per animal per week) 1 month after the beginning of the heavy rains, and declined thereafter. The dominant tick species was Amblyomma variegatum; other species found were Boophilus spp., Rhipicephalus spp. and Hyalomma spp. The low level of tick load compared with data from literature and from crossbred (Friesian-Bunaji) cattle kept in the study area suggests high tick resistance in Bunaji cattle. A biologically feasible method of controlling ticks in indigenous cattle would be twice weekly spraying with acaricide during only 2 months of the year in the early wet season to break the pronounced peak in the tick load. However, hand spraying offers no advantage over hand removal of ticks in terms of saving labour. The main advantage of strategic spraying lies in more thorough removal of ticks and possibly prevention of dermatophilosis at a lower cost than year-round use of acaricide. Knowledge of the seasonal pattern of tick load is also valuable for planning the introduction of selected stock with higher genetic potential, but higher susceptibility to tick-borne diseases than exhibited by Bunaji cattle.     

Disease at the wildlife-livestock interface: Acaricide use on domestic cattle does not prevent transmission of a tick-borne pathogen with multiple hosts

Several prominent and economically important diseases of livestock in East Africa are caused by multi-host pathogens that also infect wildlife species, but management strategies are generally livestock focused and models of these diseases tend to ignore the role of wildlife. We investigate the dynamics of a multi-host tick-borne disease in order to assess the efficacy of tick control from an ecological perspective. We examined the efficacy of a widespread measure of tick control and developed a model to explore how changes in the population of ticks due to control measures on cattle impact dynamics of Theileria parva infection in a system with two primary host species, cattle and Cape buffalo (Syncerus caffer). We show that the frequency of acaricide application has a significant impact on the tick population both on the host and in the environment, which can greatly reduce the pathogen load in cattle. We also demonstrate that reducing the tick population through cattle-related control measures is not sufficient to diminish disease transmission in buffalo. Our results suggest that under current control strategies, which target ticks on cattle only, T. parva is likely to remain a significant problem in East Africa, and require the continued use of acaricides, which has significant economic and ecological consequences.     

Tick bite and Lyme disease‐related emergency department encounters in New Hampshire, 2010–2014

Lyme disease (LD) is a common tick‐borne disease in New Hampshire (NH). While LD is a reportable condition and cases are counted for public health surveillance, many more people receive care for tick bites or diagnoses of LD than are reflected in surveillance data. NH's emergency department (ED) data system was queried for tick bite and LD‐related encounters. Chief complaint text was queried for words related to LD or tick bites. International Classification of Diseases 9th Revision (ICD‐9) codes were queried for the LD diagnosis code (088.81). Emergency department patient data were matched to reportable disease data to determine the proportion of ED patients reported to the health department as a suspected LD case. Data were analysed to calculate frequencies for key demographic and reporting characteristics. From 2010 to 2014, 13,615 tick bite or LD‐related ED encounters were identified in NH, with most due to tick bites (76%). Of 3,256 patients with a LD‐related ED encounter, 738 (23%) were reported to the health department as a suspected LD case. The geographic distribution of ED patients was similar to reported LD cases; however, the regions of the state that experienced higher rates of ED encounters were different than the regions that observed higher rates of reported LD cases. Seasonal distribution of ED encounters peaked earlier than reported LD cases with a second peak in the fall. While age and sex distribution was similar among ED patients and reported LD cases, the rates for children 5 years and younger and adults 65 years and older were greater for ED encounters. Patients frequently visit the ED to seek care for tick bites and suspected LD. Results of ED data analyses can be used to target education, in particular for ED providers and the public through timely distribution of evidence‐based educational materials and training programmes.     

Applications of a cell culture system for studying the interaction of Anaplasma marginale with tick cells

A cell culture system for the tick-borne rickettsia Anaplasma marginale offers new opportunities for research on this economically important pathogen of cattle. A. marginale multiplies in membrane-bound inclusions in host cells. Whereas erythrocytes appear to be the only site of infection in cattle, A. marginale undergoes a complex developmental cycle in ticks and transmission occurs via the salivary glands during feeding. We recently developed a cell culture system for A. marginale using a cell line derived from embryos of Ixodes scapularis. Here we review the use of this cell culture system for studying the interaction of A. marginale with tick cells. Several assays were developed using the A. marginale/tick cell system. An adhesion assay was developed for the identification of proteins required by A. marginale for adhesion to tick cells. The effect of antibodies against selected major surface proteins in inhibiting A. marginale infection was tested in an assay that allowed further confirmation of the role of surface proteins in the infection of tick cells. A drug screening assay for A. marginale was developed and provides a method of initial drug selection without the use of cattle. The culture system was used to test for enhancing effects of tick saliva and saliva components on A. marginale infection. The tick cell culture system has proved to be a good model for studying A. marginale-tick interactions. Information gained from these studies may be applicable to other closely related tick-borne pathogens that have been propagated in the same tick cell line.     

Molecular cloning of two Haemaphysalis longicornis cathepsin L-like cysteine proteinase genes.

Immunological protection of mammalian hosts against tick infestation has been proposed as the most sustainable alternative tick control method to the current use of acaricides which has several limitations. The success of this method is dependent on the identification of key molecules for use as tick vaccine antigens. Proteolytic enzymes are involved in a wide range of cellular processes in eukaryotes such as development regulation and nutrition, thus they can be considered as good target antigens for a tick vaccine. In the present study we used primers designed based on the consensus amino acid motifs flanking the conserved active sites C25 and N175 present in all papain-like cysteine proteinases to amplify by polymerase chain reaction, sequence and characterize two Haemaphysalis longicornis tick cysteine proteinase genes. Based on the nucleotide and deduced amino acid sequences, both genes were identified as members of the cysteine proteinase gene family by presence in their sequences of consensus motifs flanking the conserved active sites C25, H150 and N175 that are present in all papain-like cysteine proteinases. Both genes are about 1.2 kb in size and show high sequence homology predominantly to invertebrate cathepsin L-like cysteine proteinases.