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.

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.

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.

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.

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.

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.

Tick infestation level interferes with spray formulation (organophosphate + pyrethroid) efficacy against Rhipicephalus microplus.

Due to the scarcity of information regarding the control of Rhipicephalus microplus on bovines with different tick burdens, tick counts and the efficacy of a commercial spray formulation (aspersion bath with organophosphate + pyrethroid) were evaluated for animals with a low and high tick burdens for 35 days in a stall test. Thirty-two crossbreed Bos taurus indicus x Bos t. taurus experimentally infested with R. microplus larvae were divided into four groups: T01 high infestation control, T02 high infestation treated, T03 low infestation control, and T04 low infestation treated. The bovines were kept individually in pens and R. microplus females were collected daily. All data were statistically analyzed with a significance level of 5% (P ≤ 0.05). For linear regressions, variables with P≤0.05 and the highest coefficients of determination (R2 ≥ 0.70) were considered the best descriptors. The reliability level was 95%. Tick counts differed (P<0.0001) between T01 and T02 (high infestation control vs. treated), except at day 2 (P >0.05) post-treatment, and efficacy ranged from 85.2 to 50.6%. The number of collected engorged females was lower (P<0.0001) for T04 than for T03 (low infestation treated vs. control) animals from day 3 to 29, and efficacy ranged from 95.2 to 69.8%. In addition, tick burden and efficacy were negatively correlated for both the group of animals with a high tick burden (r = -0.5256; p = 0.0012; R² = 0.2762) and the group of animals with a low tick burden (r = -0.9817; p < 0.0001; R² = 0.9638). In conclusion, a high tick burden on bovines decreases the efficacy of the tested spray acaricide.

Strategic control of cattle co-parasitized by tick, fly and gastrointestinal nematodes: Is it better to use ecto + endoparasiticide or just endectocide formulations?

Ticks, flies, and gastrointestinal helminths (GINs) significantly affect cattle productivity; thus, ectoparasiticide, endoparasiticide, and endectocide drugs have commonly been used for their control. The study aimed to compare the technical (parasites counts), productive, and financial effects of a treatment protocol comprising ecto- + endoparasiticides formulations (T01: fluazuron 2.5 mg/kg + fipronil 1.25 mg/kg and fenbendazole 5 mg/kg; n = 15) to a treatment with one formulation of endectocide (T02: ivermectin 450 µg/kg + abamectin 250 µg/kg; n = 15) over 308 days under field conditions in crossbred cattle co-parasitized by Rhipicephalus microplus, Haematobia irritans, and GINs. Bovine weight gain and return on investment (ROI) were also evaluated. Bovines from T01 received four treatments against the cattle tick and two against two GINs. For T02, four treatments were performed. Animals from T01 gained 15.4 kg more than T02 and provided a comparative ROI of 15.8. In cattle co-parasitized with R. microplus, H. irritans, and GINs, the treatment protocol used in this study with ecto- + endoparasiticidal action formulations showed better technical results regarding parasite counts and productive and financial data than the strategic treatment protocol using only an endectocide formulation.

Spatial distribution and risk factors for sheep toxoplasmosis in Goiás, Brazilian Cerrado Region.

The present study aimed to evaluate the spatial distribution and risk factors for infection by Toxoplasma gondii in sheep in the state of Goiás, located in the central-western region of Brazil. Through the immunofluorescence antibody test (IFAT), the seroprevalence of anti-T. gondii antibodies was analyzed in 1000 blood serum samples obtained from sheep in all macro and micro regions of the state of Goiás. Data related to sex, age of the animals, size of the farm, type of farm, water source, veterinary assistance, replacement of the herd, presence of domestic cats, presence of wild cats and presence of other wild animals were obtained at the sampling time. The differences between the seroprevalences obtained in relation to the variables analyzed were estimated using Pearson's chi-square test (χ2). The odds ratio (OR) values for each risk factor evaluated were statistically analyzed with a confidence interval of 95%. Positivity for IgG anti-T. gondii was observed (titer ≥64) in 34.3% (343/1000) of the samples, which ranged from 26.9% (31/115) to 44.2% (53/120) and from 21.8 (12/55) to 55.2% (16 / 29), respectively in the analyzed mesoregions and microregions. In all investigated regions of the State of Goiás, serum-reactive animals were detected with the age of the animals, the source of water, the form of replacement of the herd and the presence of domestic cats and wild animals risk factors statistically associated with the occurrence of T. gondii in animals.

Investigation of fecal egg counts versus worm burden and helminth fauna in cattle treated or not with macrocyclic lactones in a tropical region.

Gastrointestinal nematodes negatively impact the health and productivity of livestock. Macrocyclic lactones (MLs) are the most common class of chemicals used in helminth control programs, however, their intense use is accelerating the development of parasite resistance. For cattle, little is known regarding the relationship between fecal egg counts (FECs) and the helminth population inside the animal's gastrointestinal tract and so this study evaluated the correlation between FEC and worm burden in cattle treated or not with MLs (ivermectin 200 µg/kg, ivermectin 630 µg/kg, abamectin 200 µg/kg, doramectin 700 µg/kg and moxidectin 200 µg/kg). Animals were necropsied to determine if there were any modifications to the proportions of worm species due to chemical treatment. FECs of ML-treated and untreated animals showed significant (p ≤ 0.05 and R2 ≥0.70) positive linear correlations and substantial or perfect strength-of-agreement (LCCC ≥ 0.61) with total worms present, all of which were Haemonchus placei and Cooperia punctata. However, this correlation and strength-of-agreement did not occur when the efficacy of MLs was ≥80 % against these helminths. Among the active MLs tested, moxidectin had the weakest relationship between FEC and worm burden, except for H. placei. Analysis of the helminthological fauna found an increase of H. placei (35.6 % = 95 % CI 35.4-35.6) and a consequent decrease of C. punctata (52.5 % = 95 % CI 52.3-52.6) in untreated animals, when compared to studies carried out over 20-40 years ago, but this proportion was reversed for ML-treated animals (C. punctata 64.5 % = 95 % CI 64.4-64.8; H. placei 30.8 % = 95 % CI 30.6-30.8). It is possible that MLs mitigate this effect in the field and that C. punctata remained prevalent in cattle in different regions of Brazil.

In vitro and in vivo effectiveness of disinfectants against Trypanosoma vivax.

Trypanosoma vivax causes bovine trypanosomosis in cattle and resulting in economic losses to farmers. In Brazil, shared contaminated materials is the main transmission pathway. To evaluate the effectiveness of different disinfectants for T. vivax, in vitro and in vivo analyses were performed. At the laboratory, 21 disinfectants were tested. The disinfectants were placed in microtubes containing blood with approximately 1.0 × 106 trypomastigotes of T. vivax. The viability and motile of trypomastigotes after 30 s, one, 10, 15 and 30 min was evaluated by the thick drop method and the efficacy calculated. Disinfectants that showed 100% effectiveness were used in in vivo tests. Thirty calves negative for T. vivax were divided into six groups and were inoculated with disinfectant solutions (46% alcohol, 70% alcohol, or 0.5% iodine) + 1 × 106 trypomastigotes of the protozoa. Blood from each animal was collected at seven, 14 and 21 days after inoculation to verify the viability and presence of the protozoan by Woo, Brener, PCR, and LAMP methods. In the in vitro step, 13 of the 21 disinfected solutions exhibited 100% effectiveness against T. vivax at all evaluation times. In contrast, 70% alcohol and 0.5% iodine solutions exhibited 100% effectiveness in the in vivo tests and can be used to disinfect needles and syringes. The use of disinfectants is a rapid and efficient procedure to disinfect materials utilized in the field and concomitantly could help to reduce the dissemination of T. vivax in the cattle herd in cases of iatrogenic transmission.

Eimeria spp. in naturally infected beef cattle: Dynamics of oocysts excretion, prevalence, and comparison between parasitological diagnostics.

Eimeria spp. infections cause mortality, reduced well-being, and substantial economic losses implications for cattle production worldwide. The present work followed up the excretion of Eimeria spp. oocysts in two naturally infected beef herds, from two different properties, to investigate the dynamics of oocyst excretion and the prevalence of Eimeria spp. in different animal categories and seasons of the year (rainy season - October to April; dry season - May to September). Even that, the species of Eimeria were identified and the parasitological techniques of Gordon and Whitlock modified and Mini-FLOTAC were used. In both herds, animals up to 14 months had a mean total OPG counts higher than older animals (after 15-16 months of age), and the species E. zuernii and E. bovis were more frequently identified, the first species being more frequent in animals from 1 to 2 months of age, while E. bovis prevailed from three months old. On property 1, the highest mean OPG counts (P ≤ 0.05) were obtained between October 2017 and September 2018, with the highest mean OPG counts in October 2017, when the animals were aged between 4-5 months. The prevalence of the pathogen on property 1 was 59.16 % and 43.62 % in the rainy and dry season, respectively, a higher parasitic load (P ≤ 0.05) was verified in the rainy season. On property 2, the mean OPG counts of Eimeria spp. was higher (P ≤ 0.05) in animals between 8-16 months, with the highest peak in November 2019, when they were one year old. The on-site prevalence during the rainy season on property 2 was 53.09 % and 49.79 % on dry season, and no difference (P = 0.92) in the mean OPG counts of Eimeria spp. during the seasons. There was a difference (P ≤ 0.05) in the count of oocysts in females after 18 months of age than males, which was probably due to the increase in animal density. Both tested techniques can be used for quantification of the excretion of oocysts of Eimeria spp. in cattle feces showing the same OPG mean count (r = 0.9287; p = 0.0025; R² = 0.8625). Mini-FLOTAC showed higher prevalence for Eimeria spp., however, can be an obstacle depending on the number of fecal samples that need to be processed.