Control of Rhipicephalus microplus on taurine cattle with fluralaner in a subtropical region.

BACKGROUND: In Rio Grande do Sul, Brazil, a region with a subtropical climate, Rhipicephalus microplus is present in taurine cattle raised for beef and milk. In addition, ticks resistant to multiple acaricides are present in this region. Recently, fluralaner (isoxazoline) was launched on the market. Thus, there is a need to evaluate the effects of fluralaner for the control of R. microplus on taurine cattle. In addition, occurrence of myiasis by Cochliomyia hominivorax larvae after tick parasitism and weight gain of cattle during the experimental period were evaluated. METHODS: Thirty naturally infested cattle were divided into two experimental groups: T01, treated with fluralaner (2.5 mg/kg) pour-on; T02, control. T01 received fluralaner on Days 0 (early summer in January), 42 and 84 (early autumn), whereas T02, a control group, received palliative treatment with a spray formulation when the group mean was ≥ 30 ticks. Counts of R. microplus females and calculation of the efficacy of fluralaner were performed on Days 3, 7, 14, 28, 35, 42, 56, 70, 84, 98, 112 and 126. The occurrence of myiasis was assessed throughout the study period. In addition, the weight, weight gain and daily weight gain of the animals were evaluated. RESULTS: In the 12 evaluations performed, the parasitic load of T01 was near zero. Fluralaner showed 99.5% efficacy on the 3rd day after the first treatment and 100% efficacy from Day 7 to Day 126. Cochliomyia hominivorax larvae (n = 6; p = 0.0251) were found only in the control group (T02). At the end of the study, the animals subjected to treatments with fluralaner gained 32.8 kg more than the animals in the control group. CONCLUSIONS: Application of fluralaner in summer and autumn, with 42-day intervals between treatments, was effective to control R. microplus on taurine cattle, which also gained more weight than control cattle. Additionally, no cases of myasis were documented in animals treated with fluralaner.

Enzootic stability of tick fever in Holstein calves grazing in a tropical region, subjected to strategic cattle tick control with fluralaner.

BACKGROUND: In 2022, fluralaner was launched on the market for use in the control of the cattle tick Rhipicephalus microplus after showing 100% efficacy in registration trials against the causative agents of cattle tick fever (TFAs). The aim of the present study was to determine whether a strategic control regimen against R. microplus using fluralaner (FLU) in Holstein calves grazing in a tropical region would alter the enzootic stability status of cattle tick fever, triggering outbreaks in these animals up to 22 months age. METHODS: In this study, a group of calves treated with FLU was compared with a control group treated with the regimen currently being used on the farm, which consisted of the fipronil + fluazuron formulation (FIFLUA). In the first experiment, the efficacy of the FIFLUA pour-on formulation was evaluated in a field study. In the second experiment, which lasted 550 days, two experimental groups (n = 30/group) of Holstein calves naturally infested with R. microplus were analyzed. Calves aged 4 to 10 months received either a specific treatment regimen with FLU (experimental group) or FIFLUA (control group). During this period, tick counts, animal weight measurement, feces collection (to determine eggs and oocysts per gram of feces), tick fever monitoring, blood smears (to ascertain enzootic stability of the herd), PCR testing for TFAs and serology (indirect enzyme-linked immunosorbent assay [iELISA]) were performed. All calves were evaluated for signs of tick fever between ages 11 and 22 months. RESULTS: FIFLUA showed an acaricidal efficacy of > 90% from post-treatment days 14 to 35. Regarding treatments against the TFAs, the average number of treatments was similar between groups, but animals treated with FLU had a smaller reduction in packed cell volume on some of the evaluation dates of the second and third treatment against TFAs. In calves aged 10 months in the FLU group, B. bovis was not detected by PCR (0/15 samples), 40% of the samples had antibody titers and 33% (10/30) of the samples had positive blood smears. Regarding B. bigemina, > 86% of the samples in both groups tested positive for B. bigemina DNA and antibodies; there was no difference in the antibody titers between the groups. There were no clinical cases of cattle tick fever in calves aged 11 to 22 months. CONCLUSIONS: In comparison with the control treatment, the strategic control regimen against R. microplus with FLU that was implemented in the present study did not negatively affect the enzootic stability status of A. marginale and B. bigemina in the herd up to 22 months of age. The enzootic stability status of B. bovis was not reached by either group. These results likely represent a characteristic of the local tick population, so further studies should be performed.

What is the optimal timing to initiate strategic control of Rhipicephalus microplus in taurine cattle in a tropical region?

Cattle tick control poses a significant challenge for livestock in tropical and subtropical regions. The objective of this study was to determine the most suitable timing to initiate a strategic tick control program and to identify the ideal number of acaricide treatments for adult taurine cattle (Bos taurus taurus) in a tropical region throughout the year. Three groups with 10 bovines each were performed: T01 (strategic treatment in late autumn/winter/late spring, every 28 days), T02 (strategic treatment to act in the "first tick generation" - early spring/summer/early autumn, every 28 days) and T03 (control). Tick counts (females 4-8 mm) were conducted every 14 days. If the tick burden in any group reached 30 or more during these counts, we applied an additional treatment. Over the course of a year, T02 required significantly fewer (p < 0.05) acaricide treatments than T01, with nine treatments for T02 and eleven for T01. Furthermore, during the tick counts, animals in T02 showed a lower tick burden compared to those in T01. Initiating the strategic tick control program in early spring, corresponding to the first tick generation, proved more effective than starting in autumn. This approach not only required fewer acaricide treatments but also resulted in a reduced tick burden. These benefits are particularly valuable in terms of animal welfare and managing acaricide resistance issues.

Toltrazuril + fenbendazole for cattle: Pharmacokinetics and efficacy against Eimeria spp. and gastrointestinal nematodes.

The present work evaluated the pharmacokinetics and efficacy of the association of 15cmg/kg toltrazuril +5cmg/kg fenbendazole against Eimeria spp. and gastrointestinal nematodes (GINs) in calves of different regions of Brazil (Center-West, Southeast, and South). A total of seven experiments were carried out, five of which determined formulation efficacy against Eimeria spp., considering the following aspects: therapeutic, preventive, metaphylactic, and residual efficacy. Therapeutic efficacy experiments for GINs were carried out by parasitological necropsy. The toltrazuril + fenbendazole association demonstrated ≥95% efficacy against Eimeria spp. for 21 days post-treatment (DPT). When used preventively and metaphylatically, the same association demonstrated ≥97% efficacy against E. zuernii, E. ellipsoidalis, E. cylindrica, E. bovis, E. wyomingensis and E. auburnensis. Toltrazuril + fenbendazole administered seven days before challenge was 100% effective against all these Eimeria species. Results of therapeutic, preventive, metaphylactic and residual efficacies can be related to the pharmacokinetic results, especially considering toltrazuril sulfone, which was detected in animal plasma for a longer period than the parent compound. Toltrazuril + fenbendazole achieved 100% anthelminthic efficacy against the GINs Haemonchus placei (L4), Cooperia pectinata and Oesophagostomum radiatum; 99.94% against adult H. placei; and 99.98% against C. puntacta. The association of toltrazuril + fenbendazole, associated with other measures, is an important and suitable tool for the control and treatment of Eimeria spp. and GINs in young cattle.

Two protocols using fluralaner for Rhipicephalus microplus strategic control on taurine cattle in a tropical region.

BACKGROUND: The present study aimed to evaluate the effects of different treatment strategies using a new commercial formulation containing pour-on fluralaner on Rhipicephalus microplus infestation in cattle and in pastures in a tropical climate region where up to five generations of this tick species can occur per year. METHODS: Forty-five naturally infested cattle were divided into three experimental groups: T01, treated with fluralaner (2.5 mg/kg) pour-on every 42 days; T02, the cattle received the first treatment with fluralaner on Day 0 but the next treatment involved a weekly visual evaluation; T03, control, received palliative treatment with a spray formulation when the group mean was ≥ 30 ticks. Counts of female R. microplus were performed weekly until day 343, and larval counts on pasture were performed on Days 0, 30, and 60 and every 30 days until Day 330. RESULTS: Using fluralaner, six applications were performed in Group T01, and four were performed in Group T02. In the control group (T03), it was necessary to perform eight palliative acaricide treatments with the spray formulation. The animals in T01 and T02 showed lower mean tick counts (p ≤ 0.05) than the control group (T03) on 28 and 27 of the 49 evaluated dates, respectively. In the paddock where the animals were kept as controls, the R. microplus larvae counts increased to 1458. In the paddocks where the animals were treated with fluralaner, the number was ≤ 19 per paddock during the study. CONCLUSIONS: The different strategic treatment protocols performed with pour-on fluralaner (2.5 mg/kg) over a year in taurine cattle in a tropical region with a history of up to five annual generations of cattle ticks were effective, maintaining levels of R. microplus infestations in animals and in pastures close to zero in most of the study. Depending on the retreatment criterion adopted, the number of applications per year may be lower, resulting in a reduction in the mean cost of acaricide treatment per year and lower exposure of R. microplus populations to the active ingredient, resulting in lower resistance and selection pressure.

Evaluation of mechanical transmission of Trypanosoma vivax by Stomoxys calcitrans in a region without a cyclic vector.

This work investigated the mechanical transmission of Trypanosoma vivax by Stomoxys calcitrans to cattle in a region without a cyclic vector. The study involved two experiments, one with calves experimentally infected with T. vivax, in the acute phase of trypanosomosis (Experiment 1) and the other in the chronic phase (Experiment 2). In both experiments, two transmission methods were used with flies that had not fed for 24 h or had never fed: (i) Method 1: flies released freely in cattle pens (≈3,300 flies/pen for 10 days); and (ii) Method 2: flies placed in a feeding chamber (12 flies/animal). To develop Method 1 in the two experiments (acute and chronic phases), T. vivax-positive animals were kept with T. vivax-negative animals. Periodically, the Brener method, Woo method, blood smears, cPCR, ELISA, IFAT, and Imunoteste® were performed to detect T. vivax in the animals. We also recorded the animals' head tossing and hoof stomping and the number of flies near the pens' inner walls. Subsequently, biological testing was performed using lambs. For Method 2 in both experiments, flies inside the feeding chamber first fed on T. vivax-positive animals and later on negative animals. In both experiments and methods, we examined the flies for the presence of T. vivax through blood smears and cPCR of the proboscis and abdomen. In Experiment 2 (chronic phase), a test was conducted to determine how long trypomastigotes forms could survive on the blood of animals with different levels of parasitemia. None of the animals (calves and lambs) became infected with T. vivax or showed antibodies against it. During the evaluation period, the animals in the presence of the flies exhibited more hoof stomping and head tossing compared to those without flies (control). Additionally, there was an increase in the number of flies in the pens during the experiment. Only in Experiment 1 (acute phase) were T. vivax trypomastigotes and DNA found in the abdomen of the flies but not in the proboscis. In Experiment 2 (chronic phase), higher concentrations of trypomastigotes per milliliter of blood were associated with a shorter the lifespan of this stage of the parasite. In conclusion, under the variable conditions of the experiments (hosts, number of flies, and level of parasitemia), S. calcitrans was unable to mechanically transmit T. vivax to cattle.

Essential oils and isolated compounds for tick control: advances beyond the laboratory.

BACKGROUND: Tick control is a worldwide challenge due to its resistance to acaricides. Essential oils (EOs) and isolated compounds (EOCs) are potential alternatives for tick control technologies. METHODS: A review with EOs and EOCs, under field and semi-field conditions, was performed based on Scopus, Web of Science and PubMed databases. Thirty-one studies published between 1991 and 2022 were selected. The search was performed using the following keywords: "essential oil" combined with "tick," "Ixodes," "Argas," "Rhipicephalus," "Amblyomma," "Hyalomma," "Dermacentor," "Haemaphysalis" and "Ornithodoros." The words "essential oil" and "tick" were searched in the singular and plural. RESULTS: The number of studies increased over the years. Brazil stands out with the largest number (51.6%) of publications. The most studied tick species were Rhipicephalus microplus (48.4%), Ixodes scapularis (19.4%), Amblyomma americanum and R. sanguineus sensu lato (9.7% each). Cattle (70%) and dogs (13%) were the main target animal species. Regarding the application of EOs/EOCs formulations, 74% of the studies were conducted with topical application (spray, pour-on, foam, drop) and 26% with environmental treatment (spray). Efficacy results are difficult to evaluate because of the lack of information on the methodology and standardization. The nanotechnology and combination with synthetic acaricides were reported as an alternative to enhance the efficacy of EOs/EOCs. No adverse reactions were observed in 86.6% of the studies evaluating EOs/EOCs clinical safety. Studies regarding toxicity in non-target species and residues are scarce. CONCLUSIONS: This article provides a comprehensive review on the use of EOs and EOCs to reduce tick infestations, in both the hosts and the environment. As future directions, we recommend the chemical characterization of EOs, methodology standardization, combination of EOs/EOCs with potential synergists, nanotechnology for new formulations and safety studies for target and non-target organisms, also considering the environmental friendliness.

Advances in Non-Chemical Tools to Control Poultry Hematophagous Mites.

The blood-sucking mites Dermanyssus gallinae ("red mite"), Ornithonyssus sylviarum ("northern fowl mite"), and Ornithonyssus bursa ("tropical fowl mite") stand out for causing infestations in commercial poultry farms worldwide, resulting in significant economic damage for producers. In addition to changes in production systems that include new concerns for animal welfare, global climate change in recent years has become a major challenge in the spread of ectoparasites around the world. This review includes information regarding the main form of controlling poultry mites through the use of commercially available chemicals. In addition, non-chemical measures against blood-sucking mites were discussed such as extracts and oils from plants and seeds, entomopathogenic fungi, semiochemicals, powder such as diatomaceous earth and silica-based products, and vaccine candidates. The control of poultry mites using chemical methods that are currently used to control or eliminate them are proving to be less effective as mites develop resistance. In contrast, the products based on plant oils and extracts, powders of plant origin, fungi, and new antigens aimed at developing transmission-blocking vaccines against poultry mites provide some encouraging options for the rational control of these ectoparasites.

Effect of a preventive strategic control program, with imidocarb dipropionate, against tick fever agents in dairy calves.

Chemoprophylaxis with dipropionate imidocarb (IMD) is a method adopted to prevent cattle tick fever (TF). Sixty weaned dairy heifers (±60 days old), without previous exposure to Rhipicephalus microplus ticks, were housed in Tifton paddocks and were subsequently exposed to R. microplus ticks and monitored up to 315 days old. Thirty animals were kept as controls (T01) and 30 received five preventive strategic treatments with IMD at 21-day intervals (T02). The heifers were monitored weekly by means of packed cell volume (PCV) and blood smears to evaluate the presence of TF agents. Salvage treatments (ST) with diminazene and enrofloxacin were administered when animals showed PCV ≤ 24%. The A. marginale prevalence was 39.3% and 37.7%, B. bovis 6.0%, and 7.3%, and B. bigemina 16.3% and 13.7% for T01 and T02, respectively. Regarding PCV values, group T01 showed lower PCV than group T02, between 119 and 161 days of life, but when animals were 196, 210, 217, and between 252 to 301 days old, an inversion occurred. The IMD treatment protocol was effective in group T02 from day 91 to 175 while treatment was being administered, but from day 182 to 315 after the IMD treatment protocol was completed, the number of salvage treatments against TF agents performed in T02 group increased significantly. The sequential application of IMD treatments with intervals less than 21 days is not recommended.

Selective versus strategic control against Rhipicephalus microplus in cattle: A comparative analysis of efficacy, animal health, productivity, cost, and resistance management.

This study compared selective control versus strategic control against Rhipicephalus (Boophilus) microplus, under conditions of a real dairy farm. Strategic control requires that all animals be treated with acaricide at regular pre-determined intervals. Selective control only requires treatment of infested animals and only when they are at or above a pre-determined threshold. Tick counts on animals and in pasture were performed and the susceptibility of tick populations to the different treatment methods was evaluated at the beginning and end of the study using the Larval Packet Test, Larval Immersion Test, and Adult Immersion Test. Over the four years of the study strategic control was more advantageous than the selective control as the group experienced lower tick burden on animals and in pasture, absence of skin lesions and myiases, lower operating costs, treatments concentrated in fewer months of the year and lower resistance pressure.

Influence of the acaricide emulsion pH on the effectiveness of spray products to control the cattle tick: laboratory and field investigations.

The current work evaluated the efficacy of 10 commercial acaricides in different pHs (4.5, 5.5, and 6.5) in laboratory (adult immersion tests (AIT), pH evaluation over time) and field assays (tick counts and efficacy). In the AIT (n=70), higher efficacies were obtained when the acaricide emulsion had a more acidic pH (4.5), mainly for two combinations of pyrethroids + organophosphate (acaricide 3 and acaricide 9). For amidine, a higher pH (6.5) showed a higher efficacy. Over time, there was a trend in the pH of these emulsions increasing. When the efficacy of chlorpyrifos + cypermethrin + piperonyl butoxide (acaricide 3) at different pHs was evaluated over time (0, 6, 12, and 24h) by AIT, the less acidic pH (6.5) showed a strongly variation in the acaricide efficacy range. The mean pH of the water samples from different regions of Brazil was 6.5. In the field, the association of pyrethroid + organophosphates (acaricide 9) with pH of 4.5 and 5.5 were more effective in tick control than the emulsion prepared with this same spray formulation at pH 6.5. The pH of the acaricide emulsions is an important point of attention and is recommended that the veterinary industry start to develop/share information regarding how the pH can affect the acaricide efficacy.

Thymol and eugenol against Rhipicephalus sanguineus sensu lato engorged females: Biological, histopathological and bioinformatic analysis.

The aim of this study was to evaluate the reproductive biology and histopathology of the ovaries of engorged females of Rhipicephalus sanguineus sensu lato exposed to combinations of thymol and eugenol, as well as to evaluate in silico the possible interactions of thymol and eugenol in tick cell membranes. To evaluate the tick reproductive biology, the adult immersion test (AIT) was performed, in which the engorged females were immersed in solutions of thymol and eugenol, combined or alone, at concentrations of 2.5 and 5.0 mg/mL. Two control groups (water and 3% DMSO) were also performed. The ticks were kept in a controlled chamber (B.O.D - 27 ± 1 °C and 80% ± 5% RH) to evaluate egg production and viability. To perform the ovaries histopathological evaluation, females were immersed in combination of thymol and eugenol (each at 2.5 and 5.0 mg/mL) and control (water and 3% DMSO) solutions. After immersion, the females were kept in B.O.D (27 ± 1 °C and RH of 80% ± 5%) for four days, they were dissected and the ovaries processed for histological analysis. In addition, an in silico analysis was performed using PASS online® software to predict probability activity (PA) of thymol and eugenol in cell membranes. The treatment with the combination of thymol and eugenol (each at 5.0 mg/mL) caused a reduction (p < 0.01) in oviposition, while the treatments with thymol (5.0 mg/mL) and combination of thymol and eugenol (5.0 mg/mL) reduced (p < 0.05) the egg viability. The treatment with combination of thymol and eugenol (5.0 mg/mL) resulted in a control percentage of 99.9%, while in the other treatments, control percentages below 56% were observed. Oocytes from the females exposed to the combinations of thymol and eugenol (each compound at 2.5 mg/mL) showed histopathological changes, except on oocyte V, while those treated with these compounds alone at 2.5 mg/mL, did not reveal any change. Changes in the shape of the oocyte, presence of vacuoles in the cytoplasm and germinal vesicle, reduction and fusion of yolk granules and rupture of some oocytes were observed. In silico analysis, showed that these compounds can act as membrane permeability inhibitors, membrane permeability agonists, membrane integrity antagonists and apoptosis agonists. We conclude that the combination of thymol and eugenol causes changes in the reproductive biology and morphophysiology of engorged females oocytes. The in silico analysis using thymol and eugenol revealed the possibility of disorganization in the cell membranes, a fact that may explain the histopathological alterations observed.

Population dynamics of Rhipicephalus microplus in dairy cattle: influence of the animal categories and correlation with milk production.

Is well known the taurine and zebuine susceptibility to Rhipicephalus microplus. Few are the reports regarding tick population dynamics between the same herd/breed, and because of this, two experiments were performed. In the 1st, the cattle tick population dynamics in dairy nursing calves (reared collective and individually), weaning calves (4-16 months), heifers (17-29 months), cows in lactation and dry cows (≥ 30 months) from the same herd, tick burden and milk production correlation were performed, for two years. R. microplus females (4.5-8.0 mm) counts and the milk production were performed every 28 and 14 days, respectively. In the 2nd experiment, bovines belonging to different categories/age (newborn without previous contact with tick; 12-13 months with tick contact since birth; and 23-24 months with tick contact since birth) were experimentally infested with 30,000 R. microplus larvae, to quantify the number of fully engorged females detached from these animals. In the 1st experiment, when the mean counts of tick were ≥ 30 all animals of the group were treated. Nursing calves showed 3-4 peaks of ticks, animals reared individually showed smaller (p ≤ 0.05) tick burden than those reared collectively. Weaning calves (4-8 months) showed 5 tick peaks/year and higher mean tick burden was found than other categories. On the other hand, animals with 17-29 months of age showed smallest (p ≤ 0.05) tick burden, with 3 tick peaks/year. When the animal become lactating the tick burden increase, and 5 peaks/year occurred, and decrease again in dry cows (p ≤ 0.05) showing 4-5 tick peaks/year. Weaning calves and lactating cows received more acaricide treatments (p ≤ 0.05), 18 and 15, respectively. Nursing calves reared individually, and heifers (21-29 months) were the categories that received two acaricide treatments. The more milk the cow produce, more ticks it has (p ≤ 0.05). In the 2nd experiment, more (p ≤ 0.05) fully engorged females were recovered from younger animals than older ones. So, different tick control strategies need to be adopted in different dairy cattle categories, and the tick burden should be considered, once the effect may be more inherent to the animal rather than the strategy adopted.

First description of conspecific hyperparasitism in Amblyomma sculptum.

The present study reports a case of conspecific hyperparasitism for Amblyomma sculptum. Two partially engorged females were collected from two naturally infested dairy cows and placed in a single petri dish to be transported to the laboratory, where they were held in a biological oxygen demand (BOD) incubator chamber under controlled conditions of 27 ± 1 °C and 85 ± 5% RH. After one day, it was observed that the smaller female (female 1) was attached to the dorsal surface of the larger female (female 2). The hypostome and chelicerae of the female 1 were entirely inserted into the cuticle of the female 2, characterizing tick attachment. Pictures were taken to illustrate the finding. After a few hours, the female 1 detached spontaneously and showed no visible signs of additional enlargement (engorgement). The females did not lay eggs and the survival period was not recorded. To our knowledge this is the first report of hyperparasitism for A. sculptum and the fourth for the genus Amblyomma.

Number of rainy days in a week influencing screwworm navel myiasis in beef calves and efficacies of injectable and topical antiparasitics.

Rainfall incidence as a risk factor for umbilical myiasis by Cochliomyia hominivorax in newborn beef cattle and the preventive and curative efficacies of injectable and topical products against its larvae were evaluated. The prevalence of navel myiasis did not differ between sex, however, it did differ between seasons of the year, independent of animal sex, with it being higher in the rainy season than in the dry season for both sexes (males 64.6%, females 62.1%). During the rainy season, rains occurred intermittently and the number of rainy days in a week had a direct influence on prevalence, with an increase (≥87%) in the number of calves with navel myiasis caused by C. hominivorax. When it rained intermittently for four, five and six days in a week during the rainy season, calves had ≈12, 24 and 11 times greater chances, respectively, of having navel myiasis compared to a week without rain during the rainy season. The injectable products did not reach preventive efficacies higher than 35%, while all treatments of topic products reached 100% preventive efficacy at 10 days post-treatment. Only the formulations with 30% dichlorfenthion and 0.32% fipronil achieved 100% curative efficacy. The results reinforce the need for intensified inspection and healing of the umbilicus during the rainy season, mainly during rainier weeks. Furthermore, topical formulations may be a better alternative as a preventive treatment than avermectin formulations. However, the curative efficacy of the topical product containing dichlorvos did not demonstrate a relationship with preventive efficacy for newborn calves.

Acaricidal activity of carvacrol and thymol on acaricide-resistant Rhipicephalus microplus (Acari: Ixodidae) populations and combination with cypermethrin: Is there cross-resistance and synergism?

This study evaluated the acaricidal activity of thymol and carvacrol on Rhipicephalus microplus populations with different resistance profiles and investigated the synergistic effect of combinations of these monoterpenes with cypermethrin. The adult immersion test (AIT) was used to characterize the susceptibility of tick populations (45 field populations) to synthetic acaricides: deltamethrin, amitraz and chlorfenvinphos. The larval packet test (LPT) was used to determine the LC50 values for thymol (25 tick populations) and carvacrol (20 tick populations). The susceptible strain Porto Alegre (POA) was used as a reference for calculating the resistance ratio (RR). Subsequently, larval immersion tests (LIT) were performed with combinations of cypermethrin with thymol or carvacrol to assess a synergistic effect. In the AIT, deltamethrin showed efficacy > 90% in one (2.2%) population tested (mean: 12.1 and 11.1 for populations 1-25 and 26-40, respectively), whereas amitraz and chlorfenvinphos showed efficacy > 90% for two (4.4%) populations (mean: 61.3 and 47.3 for populations 1-25 and 26-40, respectively) and eight (17.7%) populations (mean: 69.7 and 59.7 for populations 1-25 and 26-40, respectively). In the LPT, the LC50 values for thymol and carvacrol varied from 0.67 to 2.12 mg/mL and 0.55-3.21 mg/mL, with an average LC50 for populations of 1.49 and 1.75 mg/mL, respectively. For thymol, no resistance was observed in any of the populations, values of RR50 > 1.5. There was no correlation between the LC50 values for thymol and the efficacy of the chemical acaricides tested. Regarding carvacrol, for only one tick population had the value of RR50 > 1.5, indicating an incipient resistance. No correlation was observed between the LC50 values for carvacrol and the efficacy of tested acaricides. The combination of thymol and carvacrol with cypermethrin showed a synergistic effect in the resistant population (Jaguar - thymol 4.19 and carvacrol 3.67), and no synergistic interaction were showed in the susceptible population. Answering the questions we conclude that: 1 - The comparison between the LC50 values for thymol and carvacrol in field populations and the susceptible strain POA suggests the absence of cross-resistance (ticks and terpenes), and the differences between the LC50 values for thymol and carvacrol in the different R. microplus populations are inherent to the characteristics of each population tested; 2 - the combination of thymol or carvacrol with cypermethrin showed a synergistic effect with different activity according to the population of ticks.

Long-term efficacy of toltrazuril in naïve calves prophylactically treated and experimentally infected with Eimeria spp.

Eimeria are ubiquitous parasites and eimeriosis treatment is based on coccidiostats or coccidicides used prophylactically, metaphylactically, or therapeutically. The long-term efficacy of toltrazuril (TZR, 15 mg/kg) against experimentally infected naïve calves was investigated. Seven groups (six treated and one control) of six animals each were formed. Animals of each group received a single TZR prophylactic oral treatment on days - 42, - 35, - 28, - 21, - 14, and - 7 before the challenge with infectious sporulated oocysts of Eimeria spp. (100,000 oocysts: 59.5% E. zuernii, 38.1% E. bovis, 1.2%, E. alabamensis, and 1.2% E. ellipsoidalis). The long-term efficacy was assessed based on Eimeria spp. oocyst excretion by fecal oocyst counts. Three calves from the control group presented diarrhea with blood, which was not observed in animals belonging to the treatment groups. The TZR achieved efficacy greater than 95.0% up to 14 and 7 days. This formulation showed efficacy above 95% for 7 to 14 days, between 82 and 84% for 21 to 28 days and between 50 and 64% for 35 to 42 days.

Presence of Trypanosoma vivax DNA in cattle semen and reproductive tissues and related changes in sperm parameters.

The present work investigated the presence of Trypanosoma vivax in semen and reproductive tissues of experimentally infected cattle and evaluated changes in seminal parameters. Two groups of cattle were established: T01 - experimentally infected with T. vivax (n = 8) and T02 - not experimentally infected with T. vivax (n = 8). After infection, blood (every seven days until 182 days post-infection - DPI), semen (7, 14, 35, 56, 70, 120 and 182 DPI) and reproductive tissue (after euthanasia, 182 DPI) were collected to search for T. vivax using different techniques, including PCR, Woo and Brener. Seminal parameters, including turbulence, motility, concentration, and vigor, were also analyzed. Packed cell volume (PCV) of the animals was determined weekly and weight gain was calculated. The PCR revealed T. vivax DNA in 7/56 semen samples of post-infection T01 cattle. Trypanosoma vivax DNA was detected in the semen of 5/8 animals at 7, 14, 56, 70 and 120 DPI, in the testis of four, and in the epididymis and fat located around the testis of two others. Trypomastigote forms of T. vivax were not found in any semen sample. Sperm of T01 cattle had lower turbulence (p ≤ 0.05) at 7, 14, 35, 56, 120 and 182 DPI, lower vigor (p ≤ 0.05) at 120 DPI and more sperm abnormalities (p ≤ 0.05) than T02. Digital dermatitis was observed among T01 cattle. Animals of T01 had lower PCV values than did those of T02 for most of the evaluations performed and T02 animals gained more weight during the experiment. The results highlight the presence of T. vivax DNA in semen of infected cattle and the importance of this disease for male breeding cattle. Further research is needed to determine whether T. vivax can be sexually transmitted in cattle.

Techniques for monitoring dairy calves against the tick fever agents: a comparative analysis.

Data regarding parasitemia (blood smears), rectal temperature (RT), packed cell volume (PCV) and vaginal mucosa coloration (VMC) of Gyr x Holstein female calves between 3-7mo were accessed to evaluate different techniques for monitoring the bovine tick fever agents (TFA). The 1st experiment determined the correlation between the TFA parasitemia with RT and PCV. The 2nd, evaluated the associated risk of A. marginale parasitemia with RT and PCV in relation to the Gyr/Holstein genetic proportion (5/8,3/4,7/8 and 15/16) using Receiver Operating Characteristic Curve (ROC). The 3rd, two groups were performed: cattle monitored by RT (T01) and by PCV (T02), during their 80-210 days of age, data regarding TFA parasitemia, RT, PCV, VMC and weight were registered. In 1st experiment, RT showed weak correlation with TFA parasitemia, while PCV showed a strong correlation with A. marginale and B. bigemina, but not with B. bovis parasitemia. In experiment 2, the ROC curve analysis showed that when the genetic proportion of B. t. taurus increased, least reliable RT was to monitor calves infected with A. marginale. The PCV for monitoring A. marginale was the best technique, showing sensitivity of 74.2% and specificity of 97.0% than other techniques that used RT and VCM as a monitoring tool. In general, calves monitored by PCV (T02) showed higher PCV values, lower A. marginale parasitemia, less pneumonia as co-infection and less salvation treatment were performed than in animals monitored by RT (T01). Furthermore, animals from T02 gained 23.5 kg more than those from T01. The low frequency of B. bovis and B. bigemina found in this study made impossible to compare the monitoring techniques for these pathogenic agents.

How many cattle can be infected by Trypanosoma vivax by reusing the same needle and syringe, and what is the viability time of this protozoan in injectable veterinary products?

It was investigated how many cattle become infected with Trypanosoma vivax by subcutaneous (SC), intramuscular (IM) and intravenous (IV) routes, using the same syringe and needle from an animal with acute T. vivax infection. Besides, the T. vivax viability in 109 injectable veterinary drugs (antibiotics, antiparasitics, reproductive hormones, vitamin complex and derivatives, vaccines, anaesthetics, anti-inflammatory/antipyretics, antitoxics). In the field assay, four groups were performed: T01, T02 and T03 animals that received saline solution with the same syringe and needle contaminated with T. vivax via SC, IM and IV routes, respectively, and T04 control animals that received only saline solution with the same syringe and needle IV. In the laboratory, drugs had their pH measured and T. vivax viability verified. The number of cattle infected with T. vivax via SC (3/20) was lower (P ≤ 0.05) compared to via IM (9/20), which was lower (P ≤ 0.05) compared to IV (15/20). The solution pH did not influence T. vivax viability. In 44% (48/109) of the products, T. vivax remained viable regardless of time, stooding out that in 100% of oxytocins the protozoan was verified, at some evaluation times. The mean of T. vivax quantified in foot-and-mouth and brucellosis vaccines and in doramectin-based products were higher (P ≤ 0.05) than found in blood + saline solution.