Tick Counts Research Articles

Inferring phenotypic causal networks for tick infestation, Babesia bovis infection, and weight gain in Hereford and Braford cattle using structural equation models

Tick infestation and associated diseases (i.e., babesiosis) constitute major drawbacks for improvement of beef cattle productivity in the tropics, mainly when purebred and crossbred taurine animals are used. Host-parasite-pathogen interactions form complex biological systems that are poorly understood and which significantly affect production and quality traits in ways yet to be dissected and described. This research was carried out to investigate potential causal relationships, through the use of structural equation modeling (SEM), among tick counts (TC), Babesia bovis infection level (IB) and the gains in weight: from birth to adjusted weaning age (WG), and from weaning to yearling (YG). Statistical analyses were conducted in three steps: 1) Partition of (co)variances into genetic and residual components using Bayesian multiple-trait modeling (MTM); of 2) Search for plausible causal structures by applying the inductive causation (IC) algorithm to the residual (co)variances obtained in the first step; and 3) Final analysis using SEM, which was based on the causal network learned from the IC algorithm. The most plausible results comprised three direct links between traits: WG→YG, TC→WG, and WG→IB with structural coefficients posterior means equal to -0.3026, 6.3620, and 0.0004, respectively. The final inferred directed acyclic graph (DAG) suggests that interventions on TC would directly affect WG, which would then affected YG; moreover, WG could also present a small positive effect on IB.

Consistent individual differences in ecto‐parasitism of a long‐lived lizard host

Individual hosts vary substantially in their parasite loads. However, whether individual hosts have consistently different loads remains uncertain. If so, hosts that have consistently high parasite loads may serve as key reservoirs or super‐spreaders. Thus, identifying whether individuals persistently differ in their parasitism and the factors that explain these patterns constitute important issues for disease ecology and management. To investigate these topics, we examined nine years of tick counts in a wild population of sleepy lizardsTiliqua rugosa. Lizards were individually marked, and throughout their activity season, often across several years, we repeatedly assessed lizards’ ticks (to stage – larva, nymph, adult male and adult female – and species, eitherBothriocroton hydrosauriorAmblyomma limbatum). Using these repeated individual measures, we determined whether tick counts were repeatable. Then, we tested predictors of average tick counts, particularly lizard mass, sex, behavioural type (aggression and boldness), and the distance between lizards’ home range centre and a road transecting the study site (an area of greater food and lizard activity). We found that lizards exhibited consistent individual differences in tick loads both within and across years. Within‐lizard yearly average counts of larvae and nymphs were positively correlated. Lizards closer to the road tended to have more larvae and nymphs of both species and more adultB. hydrosauri. Sex did not affect tick counts. Mass differentially affected adult femaleA. limbatumand adult maleB. hydrosauritick counts. Intriguingly, lizards with above average aggression but below average boldness, or vice versa, tended to have higher average adult femaleB. hydrosauritick counts. Ultimately, our results demonstrate that lizards differed consistently in their tick counts, indicating that lizard parasitism may constitute a phenotypic trait of the individual, with implications for both host–parasite dynamics and broader host ecology.

Evaluation of rotational grazing as a control strategy for Rhipicephalus microplus in a tropical region

Rhipicephalus microplus is the most significant tick of livestock and its control is particularly challenging due to its resistance to commercial acaricides. Pasture rotation is considered a management strategy that could help control R. microplus, however, the literature only contemplates mathematical models and little is known about the effects of this practice in the field. The objective of this work was to determine whether pasture rotation is an efficient method for controlling R. microplus. Two different experiments were performed that involved groups of continuous and rotational grazing bovines. Female ticks measuring 4.5–8.0 mm were counted on animals while larvae in pasture were counted using the flannel drag technique. Treatment for infested bovines was applied when the average group tick count was ≥30 females. The results showed that rotational grazing (with 20-day periods of rest) had a higher tick count on-host than continuous grazing (P < 0.05) and additional bovine treatment was needed. Sixty and 105 days were needed to re-infest and disinfest pasture of R. microplus larvae, respectively. The first treatment of bovines occurred 91 days after the animals were placed in a closed area. The results indicate that rotational grazing is not an efficient way to control R. microplus.

Do rainfall and tick burden affect the efficacy of pour-on formulations against Rhipicephalus (Boophilus) microplus?

Rhipicephalus (Boophilus) microplus is the most important livestock tick, causing economical losses especially in tropical and subtropical regions. Pour-on formulations using synthetic chemicals, remain the most farmer friendly conventional form of tick control method. Misuse of acaricides can lead to the emergence of resistance, residual chemicals in animal products, the poisoning of vertebrates and environment contamination. Despite the increase in the use of pour-on formulations, little is known regarding the therapeutic and residual efficacy of these products after the treated animals are exposed to rainfall. Moreover, information is scanty on whether efficacy is modulated by different levels of tick burden. Three studies were conducted. In the two first experiments, we evaluated the therapeutic and residual efficacies of commercial pour-on products (fluazuron 2.5 mg/kg and fipronil 1.0 mg/kg, respectively) on cattle naturally infested with R. (B.) microplus under the condition of simulated rainfall. In the third study, we investigated whether tick burden affects the efficacy of the drugs used a chemical control method involving three different formulations (Day 0: cypermethrin 5.0 mg/kg + chlorpyrifos 7.0 mg/kg + citronellal 0.5 mg/kg; Day 7: fluazuron 3.0 mg/kg + abamectin 0.5 mg/kg and Day 56: fipronil 1.0 mg/kg + fluazuron 3.0 mg/kg). Tick counts were performed on different days to assess efficacy. It was observed that the residual efficacy of the commercial formulations was lower on animals that received simulated rain. In addition, therapeutic and residual efficacies of the products were reduced in the group of animals with a high tick burden of R. (B.) microplus. In conclusion, rainfall decreases the efficacy of acaricides. Also, the tick burden must be considered when selecting a pour-on formulation.

Evaluation of the speed of kill of a novel orally administered combination product containing sarolaner, moxidectin and pyrantel (Simparica Trio\u2122) against induced infestations of Ixodes scapularis on dogs

BackgroundThe black-legged (or deer) tick, Ixodes scapularis, commonly infests dogs in the USA and is the vector of important zoonotic pathogens, including Borrelia burgdorferi, the causative agent of Lyme disease. Rapid onset of activity is important in reducing the feeding activity of ticks, thereby reducing the possibility of transmission of infections. The speed of kill of a novel oral combination product, Simparica Trio™ containing sarolaner, moxidectin and pyrantel was evaluated in a well-controlled laboratory study against an existing infestation and subsequent weekly induced infestations of I. scapularis ticks on dogs.MethodsDogs were allocated randomly based on host suitability tick counts to treatment with a single dose of either placebo or Simparica Trio™ at the minimum label dose of 1.2 mg/kg sarolaner, 24 µg/kg moxidectin and 5 mg/kg pyrantel (as pamoate salt). All dogs were infested with approximately 50 unfed adult I. scapularis ticks at a 1:1 sex ratio on Days −2, 7, 14, 21, 28 and 35. Tick counts were conducted at 8, 12 and 24 h after treatment on Day 0 and after each subsequent infestation.ResultsNo treatment-related adverse events occurred during the study. Dogs in the placebo-treated group maintained adequate tick infestations for the duration of the study. Day 0 tick counts at 8 h after treatment with Simparica Trio™ were reduced relative to placebo against an existing infestation with efficacy of 67.5%, demonstrating that Simparica Trio™ started killing ticks soon after treatment. Efficacy was 98.4 % at 12 h and 99.4% at 24 h. Rapid speed of kill was maintained throughout the month, with efficacy of ≥ 94.2% at 24 h after re-infestation through Day 28.ConclusionsA single dose of Simparica Trio™ administered orally to dogs at the minimum label dose of 1.2 mg/kg sarolaner, 24 µg/kg moxidectin and 5 mg/kg pyrantel (as pamoate salt) was safe and began to kill existing I. scapularis ticks within 8 h after treatment and resulted in ≥ 94.2% efficacy within 24 h against re-infestations for a month.

Efficacy of a novel orally administered combination product containing sarolaner, moxidectin and pyrantel (Simparica Trio\u2122) against induced infestations of five common tick species infesting dogs in the USA

BackgroundThe efficacy of a novel oral combination product, Simparica Trio™, containing sarolaner, moxidectin and pyrantel was evaluated against five tick species that commonly infest dogs in the USA, Amblyomma americanum, Amblyomma maculatum, Dermacentor variabilis, Ixodes scapularis and Rhipicephalus sanguineus.MethodsLaboratory studies were conducted against two different strains of each tick species. In each study, 10 purpose-bred Beagle or mixed-breed dogs were randomly allocated to one of two treatment groups based on pre-treatment host-suitability tick counts. Dogs were infested with approximately 50 (45–55) unfed adult ticks on Days -2, 5, 12, 19, 26 and 33. On Day 0, dogs received either a single oral dose of Simparica Trio™ at the minimum label dose of 1.2 mg/kg sarolaner, 24 µg/kg moxidectin and 5 mg/kg pyrantel (as pamoate salt) or placebo. Tick counts were conducted at 48 h post-treatment and after each subsequent weekly re-infestation for A. maculatum, D. variabilis, I. scapularis and R. sanguineus studies and at 48 hours or at 72 h post-treatment and after weekly re-infestation in the first and second A. americanum studies, respectively.ResultsNo treatment-related adverse reactions occurred in any study. In all studies, placebo-treated dogs maintained infestations throughout the entire study duration, and dogs treated with Simparica Trio™ had significantly lower (P ≤ 0.0010) mean live tick counts than placebo-treated dogs at all time-points. Against A. maculatum, D. variabilis, I. scapularis and R. sanguineus, a single oral dose of Simparica Trio™ evaluated at 48 h post-treatment provided ≥ 98.9% efficacy against existing infestations, and within 48 h of re-infestation efficacy was ≥ 90.4% through at least Day 28 (except for R. sanguineus on Day 14 in a single study with an efficacy of 89.7%). Against A. americanum, Simparica Trio™ provided ≥ 99.4% efficacy at ≤ 72 h after treatment of existing infestations and maintained ≥ 98.4% efficacy at ≤ 72 h after re-infestation through at least Day 35.ConclusionsA single dose of Simparica Trio™ administered orally at the minimum label dosage of 1.2 mg/kg sarolaner, 24 µg/kg moxidectin and 5 mg/kg pyrantel provided treatment and control of the common tick species infesting dogs in the USA for at least one month.

Efficacy of a novel chewable tablet containing sarolaner, moxidectin and pyrantel (Simparica Trio\u2122) against four common tick species infesting dogs in Europe

BackgroundTick infestations can cause direct deleterious effects to dogs as a result of tick blood-feeding, and indirectly ticks can transmit disease agents that can be detrimental to the health of both dogs and humans. Six laboratory studies were conducted to support dosage selection and efficacy confirmation of a novel combination of sarolaner, moxidectin and pyrantel against four tick species that commonly infest dogs in Europe.MethodsTwo studies were conducted against Dermacentor reticulatus (one of which was a dose determination study), two against Ixodes ricinus, and one each against Ixodes hexagonus and Rhipicephalus sanguineus (sensu lato). In each study, eight purpose-bred Beagle or mix-breed dogs were randomly allocated to each treatment group and infested with 50 unfed adult ticks on Days-2, 5, 12, 19, 26 and 33. On Day 0 dogs were treated orally with placebo or the combination product. In the dose determination study, dogs received sarolaner at point dosages of 0.6 mg/kg, 1.2 mg/kg or 2.4 mg/kg in combination with moxidectin and pyrantel, and in all other studies dogs received Simparica Trio™ to provide minimum dosages of 1.2 mg/kg sarolaner, 24 µg/kg moxidectin and 5 mg/kg pyrantel (as pamoate salt). Efficacy was assessed based on live tick counts conducted 48 hours after treatment and each weekly infestation.ResultsThere were no treatment-related adverse events in any study. In the dose determination study, 1.2 mg/kg sarolaner was the lowest dosage evaluated that provided > 90% efficacy for at least 28 days and therefore was selected as the dosage to provide tick control for at least one month following a single oral treatment. In the dose confirmation studies, a single oral dose of Simparica Trio™ provided ≥ 99.2% efficacy against existing infestations of all tick species, and against re-infestations efficacy was ≥ 97.2% against D. reticulatus for 28 days and against all other species for 35 days.ConclusionsThese studies support the sarolaner dose selected and confirm the efficacy of a single oral dose of Simparica Trio™ against existing infestations and re-infestations of the common tick species infesting dogs in Europe for at least one month.

Efficacy of a novel oral chewable tablet containing sarolaner, moxidectin and pyrantel (Simparica Trio\u2122) against natural flea and tick infestations on dogs presented as veterinary patients in Europe

BackgroundA novel chewable oral tablet containing sarolaner, moxidectin and pyrantel (Simparica Trio™) has recently been developed to provide persistent protection against flea and tick infections for a month, treatment of hookworm and roundworm infections and prevention of heartworm and lungworm disease in dogs. Two field studies were conducted to evaluate the safety and efficacy of Simparica Trio™ against natural flea and tick infestations on dogs in Europe.MethodsDogs with natural flea or tick infestations were allocated randomly to treatment on Day 0 with either Simparica Trio™ tablets (flea study: n = 297; tick study: n = 189) to provide 1.2–2.4 mg/kg sarolaner, 24–48 µg/kg moxidectin and 5–10 mg/kg pyrantel (as pamoate salt) or with NexGard® Spectra (afoxolaner + milbemycin oxime) according to the label instructions (flea study: n = 164; tick study: n = 91). Efficacy was calculated based on the mean percent reduction in live parasite counts compared to the respective pre-treatment counts on Days 14 and 30 in the flea study and on Days 7, 14, 21 and 30 in the tick study. To count the fleas, the dog’s entire coat was systematically combed using an extra fine-tooth flea comb until all fleas were removed. For the tick counts, the dog’s entire coat was searched manually. Resolution of the clinical signs of flea allergy dermatitis (FAD) was assessed in flea allergic dogs in the flea study. Palatability was assessed in both studies.ResultsSimparica Trio™ was well tolerated in both studies. Efficacy against fleas was ≥ 97.9% in the Simparica Trio™ group and ≥ 96.1% in the NexGard® Spectra group. Efficacy against ticks was ≥ 94.8% in the Simparica Trio™ group and ≥ 94.4% in the NexGard® Spectra group. Clinical signs of flea allergy dermatitis improved following treatment with Simparica Trio™. Simparica Trio™ tablets were voluntarily and fully consumed on ≥ 78% of the 485 occasions they were offered.ConclusionsA single oral dose of Simparica Trio™ was safe and highly efficacious against naturally occurring flea and tick infestations for 1 month on dogs. Clinical signs of FAD improved following treatment. Simparica Trio™ was voluntarily and readily consumed by most dogs.

Prevalence, distribution on host's body, and chemical control of camel ticks Hyalomma dromedarii in the United Arab Emirates.

Background and Aim:Camel farming remains a part of the culture of the Arabian Peninsula although modern methods have greatly increased camel densities in the entire region. In the United Arab Emirates (UAE), camel production is threatened by tick parasitism. However, no study has considered assessing the magnitude of the problem in the UAE. We conducted a study evaluating tick richness, abundance, and spatial distribution of ticks on camels in farms near Al Ain, UAE. In addition, we conducted a survey of farm owners to determine the control methods used to eliminate camel ticks.Materials and Methods:Tick counts were made on 502 camels (Camelus dromedarius). For each examined animal, visual counts of ticks were made on the entire body segregating the counts by head, neck, forelegs, hump, abdomen, back legs, and tail area. In addition, a total of 70 camel owners from the study area were randomly selected and surveyed about the tick control methods.Results:Hyalomma dromedarii was the only species found during the study. The prevalence of ticks was 98% among the sampled animals. The mean intensity (tick load) was 25.8±2.4 ticks/host and the maximum number of ticks per animal was 102. Ticks were found in five vicinities that are on the border with Oman. The highest number of ticks on the body of the camel occurred on the tail area followed by the abdomen. Cypermethrin was the most commonly used acaricide (46.9%).Conclusion:The high abundance of ticks reported in this study calls for the establishment of a good management strategy. In addition, finding ticks in vicinities in the UAE that are on the border with Oman suggests a cross-border movement between the two countries. Therefore, studying this movement is important to understand its role in the global circulation of some H. dromedarii tick-borne diseases and the movement of acaricide resistance alleles among tick populations.

Comparative Efficacy of Metarhizium anisopliae and Amitraz in Control of Rhipicephalus decoloratus on Cattle under Field Conditions in Kenya

Ticks and tick-borne diseases represent a major constraint to cattle production in Kenya. The use of entomopathogenic fungi is an important and promising component of bio-control agents for controlling devastating tick species which include Rhipicephalus appendiculatus, Amblyomma variegatum and Rhipicephalus (Boophilus) decoloratus. The aim of this study was to evaluate the efficacies of the fungus Metarhizium anisopliae ICIPE 7 and the acaricide, amitraz in controlling R. decoloratus in naturally infested cattle under field conditions. This study was undertaken during the short rains (October to November 2014) in Narok County, Kenya. Twenty animals (steers and heifers) were randomly allocated to four treatment groups; Control (water + 0.05% Triton X–100 + 15% canola oil); M. anisopliae ICIPE 7 isolate alone (1×109 conidia ml-1); Amitraz alone at recommended concentration of 0.2% and combination of M. anisopliae ICIPE 7 isolate (1 x 108 conidia ml-1) and amitraz (0.1%). The overall R. decoloratus load was high at the start of treatment (day 0) in all the four groups and was highest along the dewlap followed by the back region while the head region had no blue ticks. All the three treatments reduced tick counts significantly on days 7, 14, 21 and 28 relative to the control group with percentage efficacy on day 28 post treatment being 69.2% for ICIPE 7, 67.1% for ICIPE 7 plus amitraz and 94.9% for amitraz alone. Treatments with M. anisopliae ICIPE 7 alone and M. anisopliae ICIPE 7 isolate plus amitraz attained mortality of 93.5% compared to 2.3% of the control group and all fungal infected ticks developed mycosis. This study has demonstrated that M. anisopliae ICIPE 7 isolate was as effective as amitraz and when combined as a spray reduced the tick population significantly. This association could be used as a tool for integrated control of R. decoloratus.

Additive Efficiency of Fipronil + Methoprene Compared to Fipronil Alone against &amp;lt;i&amp;gt;Rhipicephalus sanguineus&amp;lt;/i&amp;gt; Ticks in Naturally Infested Dogs

The acaricidal efficiency of fipronil alone and fipronil + methoprene compared to commercial fipronil and commercial fipronil + methoprene, applied by the epicutaneous route (spot-on) in dogs naturally infested with ticks, was assessed. Thirty dogs infested with high loads of ticks were used. On day 0, the dogs were divided into 5 groups of 6 animals each. Each animal was duly identified for individual and group monitoring. Treatments were made based on body weight according to manufacturer’s instructions. Group 1 (G1) received 10.0% fipronil at a single dose of a pipette applied by epicutaneous route in the base of the neck. G2 received 10% fipronil + 10% methoprene in single application similarly to G1. G3 was treated with 9.8% commercial fipronil as before mentioned. G4 received commercial 9.8% fipronil + 9.8% methoprene applied as in previous groups. G5 served as an infected untreated control. Animals were examined by thumb tick counts on days 0 (Treatment day), 3, 7, 14, 21 and 28. Efficacy was measured as a percentage of tick reduction in the treated groups relative to the untreated control. Results indicated an overall efficacy of 88.2%, 93%, 90.4% and 99.3%, respectively. There was no significant statistical difference between the treated groups (P ly and in full development. It is concluded that the combined formulations of fipronil + methoprene compared to fipronil applied alone, showed an additive effect against Rhipicephalus sanguineus ticks in naturally infested dogs kept in captivity.

PSVIII-38 Genomic prediction for tick resistance in Angus cattle

Abstract The main objective of this study was to evaluate the feasibility of single-step genomic BLUP (ssGBLUP) for genetic evaluation of tick resistance in Angus cattle in Brazil. Additionally, we investigated population parameters, namely effect population size (Ne) and inbreeding (F) based on pedigree (PED) and genomic (GEN) information. Half-body tick counts were recorded up to three times in the same animal, totaling 2291 records. To normalize the distribution, records were log-transformed prior to the analysis. From 7073 animals in the pedigree, 1299 were genotyped with 3 different SNP chips of density 50k, 77k, and 150k. After imputation and quality control, 61,066 SNP remained. A repeatability animal model was used to estimate variance components, traditional EBV, and genomic EBV (GEBV). Validation was carried out for young genotyped animals, with no phenotypes in the reduced data but at least one record in the complete data, using two different approaches: 1) predictive ability as the correlation between phenotypes adjusted for fixed effects and (G)EBV; 2) a method based on linear regressions that is called LR, which uses correlations between (G)EBV in the complete and reduced data as a measure of consistency between subsequent evaluations. Heritability for tick counts was 0.18 ± 0.03. Based on PED and GEN, Ne was 254 and 199, whereas F was 0.016 and 0.003, respectively. Predictive ability for tick counts was 0.11 for EBV and 0.14 for GEBV, which is considered low. Conversely, when LR validation was used, the relative increase in accuracy by adding extra phenotypic information was 0.49 for EBV and 0.61 for GEBV. Even though tick counts has low heritability, our study indicates that genomic selection can help to improve prediction accuracy and, therefore, to increase tick resistance in this Angus population.

Prevention of transmission of Borrelia burgdorferi sensu lato and Anaplasma phagocytophilum by Ixodes spp. ticks to dogs treated with the Seresto\xae collar (imidacloprid 10% + flumethrin 4.5%)

The capability of imidacloprid 10% + flumethrin 4.5% (Seresto®) collars to prevent transmission of Borrelia burgdorferi sensu lato (Bbsl) and Anaplasma phagocytophilum (Ap) by naturally infected ticks was evaluated in two studies with 44 dogs. In each study, one group served as non-treated control, whereas the other groups were treated with the Seresto® collar. All dogs were exposed to naturally Bbsl- and Ap-infected hard ticks (Ixodes ricinus, Ixodes scapularis). In study 1, tick infestation was performed on study day (SD) 63 (2 months post-treatment [p.t.]); in study 2, it was performed on SD 32 (one month p.t.) respectively SD 219 (seven months p.t.). In situ tick counts were performed 2 days after infestation. Tick counts and removals followed 6 (study 1) or 5 days (study 2) later. Blood sampling was performed for the detection of specific Bbsl and Ap antibodies and, in study 1, for the documentation of Ap DNA by PCR. Skin biopsies were examined for Bbsl by PCR and culture (only study 1). The efficacy against Ixodes spp. was 100% at all time points. In study 1, two of six non-treated dogs became infected with Bbsl, and four of six tested positive for Ap; none of the treated dogs tested positive for Bbsl or Ap. In study 2, ten of ten non-treated dogs became infected with Bbsl and Ap; none of the treated dogs tested positive for Bbsl or Ap; 100% acaricidal efficacy was shown in both studies. Transmission of Bbsl and Ap was successfully blocked for up to 7 months.

Incorporating tick feeding behaviour into [formula omitted] for tick-borne pathogens

Tick-borne pathogens pose a considerable disease burden in Europe and North America, where increasing numbers of human cases and the emergence of new tick-borne pathogens has renewed interest in resolving the mechanisms underpinning their geographical distribution and abundance. For Borrelia burgdorferi and tick-borne encephalitis (TBE) virus, transmission of infection from one generation of ticks to another occurs when older nymphal ticks infect younger larval ticks feeding on the same host, either indirectly via systemic infection of the vertebrate host or directly when feeding in close proximity. Here, expressions for the basic reproduction number, R0, and the related tick type-reproduction number, T, are derived that account for the observation that larval and nymphal ticks tend to aggregate on the same minority of hosts, a tick feeding behaviour known as co-aggregation. The pattern of tick blood meals is represented as a directed, acyclic, bipartite contact network, with individual vertebrate hosts having in-degree, kin, and out-degree, kout, that respectively represent cumulative counts of nymphal and larval ticks fed over the lifetime of the host. The in- and out-degree are not independent when co-aggregation occurs such that T∝〈kinkout〉〈kin〉,where 〈.〉 indicates expected value. When systemic infection in the vertebrate host is the dominant transmission route R02=T, whereas when direct transmission between ticks co-feeding on the same host is dominant then R0=T and the effect of co-aggregation on R0 is more pronounced. Simulations of B. burgdorferi and TBE virus transmission on theoretical tick-mouse contact networks revealed that aggregation and co-aggregation have a synergistic effect on R0 and T, that co-aggregation always increases R0 and T, and that aggregation only increases R0 and T when larvae and nymphs also co-aggregate. Co-aggregation has the greatest absolute effect on R0 and T when the mean larval burden of hosts is high, and the largest relative effect on R0 for pathogens sustained by co-feeding transmission, e.g. TBE virus in Europe, compared with those predominantly spread by systemic infection, e.g. B. burgdorferi. For both pathogens, though, co-aggregation increases the mean number of ticks infected per infectious tick, T, and so too the likelihood of pathogen persistence.

Comparative efficacy of afoxolaner and ivermectin in dogs naturally infested with Rhipicephalus sanguineus sensu lato: A clinical field study conducted in Thailand.

Afoxolaner is a novel insecticidal and acaricidal of the isoxazoline family, which is used in veterinary practice to control infestation of dogs by fleas, ticks, and mites (NexGard, Boehringer Ingelheim). Ivermectin is an avermectin administered at microdoses to prevent infection of dogs with Dirofilaria immitis and is used off-label to control Rhipicephalus sanguineus infestation of dogs in numerous countries, including Thailand. Here we conducted two trials to assess the efficacy of afoxolaner for treating natural R. sanguineus sensu lato (s.l.) infestations of dogs residing in the Chiang Mai area of Thailand. The first trial compared the efficacies of afoxolaner and ivermectin in dogs infested with <500 ticks. A randomized, investigator-blinded, controlled study was conducted of 16 dogs, allocated into the groups as follows: afoxolaner (2.7-6.9 mg/kg, PO, group 1; n = 8), ivermectin (300 μg/kg, SC, group 2; n = 5), untreated (group 3; n = 3). Tick counts and drug administration were performed on days 0, 28, and 56. Mean numbers of ticks on day 0 in groups 1, 2, and 3 were not significantly different (225, 169, and 123, respectively; p = .36). The mean number of ticks (%efficacy to control) in groups 1, 2 and 3 on day 28 were 7 (97.05%), 230 (2.95%), and 237, respectively; on day 56 were 4 (96.11%), 93 (9.71%), and 103, respectively; and on day 84 were 1 (98.65%), 44 (40.54%), and 74, respectively. The efficacy of afoxolaner was >96%, whereas the efficacy of ivermectin was significantly lower compared with that of afoxolaner (p < .05) and never achieved the 90% efficacy threshold claimed by registration agencies. The second trial assessed the efficacy of afoxolaner for treating dogs with heavy tick infestations (>500 ticks/dog), including four dogs from two households. The dogs were treated monthly with Afoxolaner. The mean values of the numbers of ticks on dogs in the 2 households were not significantly different (913 and 800 on day 0, p = .18). The numbers of ticks significantly decreased thereafter, and the efficacy of afoxolaner was >99% on days 28, 56, and 84. Adverse reactions were not observed in either trial. In conclusion, this study confirms the efficacy of afoxolaner against adult R. sanguineus s.l. that naturally infests dogs that inhabit Thailand.

Interpretation of the larval immersion test with ivermectin in populations of the cattle tick Rhipicephalus (Boophilus) microplus from Colombian farms

Interpreting in vitro bioassays used to determine resistance against acaricides in Rhipicephalus microplus can be challenging without parallel in vivo studies that assess for lost efficacy. The larval immersion test (LIT) is currently the most widely used bioassay to detect ivermectin resistance. The objective of this study was to compare results of the LIT and a field trial using ivermectin in naturally infested cattle. Criteria to consider ticks as resistant with the LIT were based on discriminating doses (DD) and the ratio of lethal concentration (LC) in test populations over the LC of the susceptible Deutch strain, known as the resistance ratio (RR). Ticks were collected from 4 farms, two where ivermectin provided good control of tick infestations and two that claimed lack of efficacy. In two farms where administration of a long-acting ivermectin formulation reduced body tick counts to 45 and 25% of the initial counts at 10-days post-treatment, the RR50 and RR99 were approximately 6 and 20, respectively. The LC50 value approximated the DD for the two farms with claimed resistance, suggesting that about half of the population in each farm was resistant. These LIT values are equal to those reported for the most resistant ticks, which supports the use of the LIT to predict control failure in field situations. The two farms where ivermectin provided good control of tick infestations had LC50s similar to the susceptible strain, although for one farm the LC99 and RR99 suggested incipient resistance.

Efficacy of sarolaner (Simparica\xae) against induced infestations of Haemaphysalis longicornis on dogs

BackgroundHaemaphysalis longicornis is the major tick affecting dogs in most of the East Asia/Pacific region and has recently been detected in a number of areas of the USA. This tick is a vector for a number of pathogens of dogs, other mammals and humans. In this study, the efficacy of a single oral administration of sarolaner (Simparica®, Zoetis) at the minimum label dosage (2 mg/kg) was evaluated against an existing infestation of H. longicornis and subsequent weekly reinfestations for 5 weeks after treatment.MethodsSixteen dogs were ranked on pretreatment tick counts and randomly allocated to treatment on Day 0 with sarolaner at 2 mg/kg or a placebo. The dogs were infested with H. longicornis nymphs on Days − 2, 5, 12, 19, 26 and 33. Efficacy was determined at 48 hours after treatment and subsequent re-infestations based on live tick counts relative to placebo-treated dogs.ResultsThere were no adverse reactions to treatment. A single dose of sarolaner provided 100% efficacy on Days 2, 7, 14 and 21; and ≥ 97.4% efficacy on Days 28 and 35. Considering only attached, live ticks, efficacy was 100% for the entire 35 days of the study. Geometric mean live tick counts for sarolaner were significantly lower than those for placebo on all days (11.62 ≤ t(df) ≤ 59.99, where 13.0 ≤ df ≤ 14.1, P < 0.0001).ConclusionsIn this study, a single oral administration of sarolaner at 2 mg/kg provided 100% efficacy against an existing infestation of H. longicornis nymphs and ≥ 97.4% efficacy (100% against attached ticks) against weekly reinfestation for at least 35 days after treatment.

Rotational grazing approaches reduces external and internal parasite loads in cattle

We tested whether holistic planned grazing (HPG) and four-camp grazing (FCG) rotational grazing approaches influence beef cattle parasites counts compared with continuous, season-long (SLG) grazing. We expected that parasite counts would increase linearly with increasing camp occupancy by cattle from 1 d (70-camp, HPG) to 21–28 d (four-camp, FCG) to 180 d (one-camp per season, SLG). Tick and faecal egg counts were observed across seasons on 30 steers raised on a private farm in Cedarville, South Africa. Tick species identified were Rhipicephalus evertsi evertsi, Rhipicephalus (Boophilus) decoloratus, Hyalomma spp. and Amblyomma hebreaum with respective prevalences of 32%, 29%, 20% and 19%. Unidentified roundworms had the highest faecal worm egg counts (81.2%) followed by Coccidia (16.4%), Nematodirus (1.2%) and strongyles (1.2%). Overall, prevalence and mean counts for ticks and faecal worm eggs were highest in the hot wet season, with the SLG having greater (P ≤ 0.05) values than either of the rotational approaches. However, increasing camp number and animal densities above four camps did not reduce (P > 0.05) parasite loads compared with HPG. Current results suggest that rotational grazing is a potential strategy to reduce livestock losses caused by high tick and worm loads in cattle, especially in the hot wet season.

Novel acaricides by nanotechnology against cattle ticks and their effect on physiological and productive performance

A field trail was conducted to evaluate the efficacy of capsules suspension formulation (CS) by nanotechnology and conventional acaricides against the cattle ticks (Hyalomma marginatum) and its effects on the body weight and blood parameters of Aberdeen angus cattle. Acaricides residues were determined in an animal's blood and milk. Thirty infested cattle were randomly divided into five groups, each one contains (3 bulls and 3 cows) based on the mean tick count. Results showed that, permethrin 25 % CS and lambada-cyhalothrin 10 % CS were significantly the most effective against ticks (2.7 and 3.8 ticks/animal, respectively) compared to fipronil 20 % SC and Acetamiprid 20 % SL (8.3 and 6.3 ticks/animal, respectively) after 70 days of treatment. Permethrin 25 % CS achieved 100 % control against highly ticks' infestation after 3 days of treatment and maintained for 56 days without its residues in blood and milk samples. Conversely, fipronil residue was detected in the cow's blood and milk (1.3 and 2.7 µg/l, respectively) however, it's non detected in bull's blood after 1 week of treatment. They gradually decreased to below detection limits after 3 and 6 weeks respectively. The animal body weight was significantly increased, additionally: the liver and kidney function were decreased to normal level in all treated animals. Finally, permethrin and lambda-cyhalothrin that formulated CS can be used as efficient acaricides and a safe alternative in tick control strategy in tropical areas.

Cattle herd shearing can help to control Rhipicephalus microplus ticks.

Given the difficulties of controlling the tick Rhipicephalus microplus due to acaricide resistance, this study aimed to ascertain whether shearing could reduce infestation in cattle. 17 taurine cattle were sheared on the anterior third of one randomly selected side. Shearing was undertaken using a machine with a blade, leaving coats with a thickness of 1mm. Subsequently, eight evaluations were performed once a week, counting adult females of R. microplus with a diameter > 4.5mm on the anterior third of both sides (shorn and unshorn). The coat length was also monitored by taking five hair samples from each animal fortnightly (1, 15, 29, 43 and 57days post shorn) from a central area of both shoulders (shorn and unshorn). The tick counts and hair length data were transformed for normalisation and were analysed using mixed models. The tick and hair length means were significantly higher for the unshorn side. Tick counts were significantly lower on the sheared side until the fifth evaluation, with the final three presenting no differences between the sides. The hair length was significantly lower for the sheared side during the five evaluations. We conclude that as the hair length increased, there was also an increase in the number of ticks on the sheared side. Although this method is not practical for large herds, it can be deemed an option in extreme conditions of tick infestation. In addition, the study reinforces the suggestion that the selection and/or use of cattle with shorter hairs may contribute to reduced tick infestation.