RESUMO
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.
Assuntos
Muscidae , Animais , Ovinos , Bovinos , Trypanosoma vivax , Parasitemia , Carneiro Doméstico , AnticorposRESUMO
This study aimed to investigate seven outbreaks of A. marginale infection in two regions of Brazil, affecting taurine, zebu, and crossbred cattle. We assessed the possible causes, treatment measures, and genetic diversity of A. marginale. These outbreaks occurred in two states (Goiás: outbreaks 1-7; Mato Grosso do Sul: outbreak 3), breeds (Holstein, Nellore, and crossbreed), age groups (beef cattle: 18-25 days old and 7-8 months; dairy cattle: 18-25 days old, 13-14 months, and cow after the first birth) and rearing systems (feedlot, pasture, pen in a wood shaving bedding system and compost bedded-pack barns). Metaphylactic or prophylactic treatments varied according to outbreak (imidocarb dipropionate: outbreaks 1-4 and 6; enrofloxacin: outbreaks 5 and 7; diminazene diaceturate: outbreak 5). In outbreaks 6 and 7, the packed cell volume was monitored. In all outbreaks, the practice of needle/syringe sharing was discontinued. For outbreaks 1-3, clinical signs and mortality (range, 4.8-13.3%) occurred 36-45 days after entry into the feedlot. In outbreak 4, A. marginale was diagnosed in 66.2% of the calves (bacteremia, 0-4.5%), with a mortality of 8.6%. Among nursing calves aged 60 days during outbreak 5, 53.8% were infected with A. marginale, with average bacteremia of 2.7% (range, 0-21.3%), and a mortality of 13.8%. In dairy heifers aged 14 months, raised in paddocks lacking vegetation cover and infested with R. microplus, then transitioned to a rotational grazing system also infested with R. microplus, the A. marginale bacteremia ranged from 3.2 to 6.7%, with a mortality of 20%. Before monitoring during outbreak 7, the mortality was 17.9%, but no further deaths were observed after monitoring initiation. In conclusion, possible causes triggering the outbreaks included primary tick infestation, needle/syringe sharing, and stress factors which may have affected the immunological statues of animals in the feedlots. Control measures performed in all outbreaks were effective. The partial msp4 gene sequences of A. marginale generated herein belonged to two haplotypes, but further research would be needed to investigate if this finding has any clinical significance.
Assuntos
Anaplasma marginale , Anaplasmose , Doenças dos Bovinos , Surtos de Doenças , Variação Genética , Animais , Brasil/epidemiologia , Bovinos , Surtos de Doenças/veterinária , Anaplasmose/epidemiologia , Anaplasmose/microbiologia , Anaplasma marginale/genética , Doenças dos Bovinos/epidemiologia , Doenças dos Bovinos/microbiologia , Feminino , Criação de Animais Domésticos/métodos , MasculinoRESUMO
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.
Assuntos
Acaricidas , Rhipicephalus , Controle de Ácaros e Carrapatos , Animais , Bovinos , Concentração de Íons de Hidrogênio , Acaricidas/química , Acaricidas/farmacologia , Emulsões , Controle de Ácaros e Carrapatos/métodos , Piretrinas/química , Piretrinas/farmacologia , Organofosfatos/química , Organofosfatos/farmacologia , Rhipicephalus/efeitos dos fármacosRESUMO
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.
Assuntos
Anaplasmose , Babesiose , Doenças dos Bovinos , Animais , Bovinos , Feminino , Imidocarbo , Diminazena , Doenças dos Bovinos/tratamento farmacológico , Doenças dos Bovinos/prevenção & controleRESUMO
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.
Assuntos
Doenças dos Bovinos , Tripanossomíase Africana , Tripanossomíase Bovina , Animais , Bovinos , Doenças dos Bovinos/prevenção & controle , Seringas , Trypanosoma vivax , Tripanossomíase Africana/veterináriaRESUMO
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.
Assuntos
Doenças dos Bovinos , Coccidiose , Coccidiostáticos , Eimeria , Animais , Bovinos , Doenças dos Bovinos/tratamento farmacológico , Doenças dos Bovinos/parasitologia , Doenças dos Bovinos/prevenção & controle , Coccidiose/tratamento farmacológico , Coccidiose/prevenção & controle , Coccidiose/veterinária , Coccidiostáticos/uso terapêutico , Fezes/parasitologia , Oocistos , TriazinasRESUMO
Amitraz is an acaricide that is widely used in veterinary medicine to control the cattle tick Rhipicephalus microplus. However, controversy exists in the literature regarding the resistance of R. microplus to this product. The present work provides an update on the acaricidal efficacy of amitraz (Triatox®, 12.5 % amitraz) after 15 years without its use on a property. Two in vivo (bovines treated with amitraz and submitted to tick counts, n = 20 animals) and one in vitro (adult immersion test, n = 40 ticks) assays were performed to determine product efficacy. The efficacy of the commercial formulation tested in the first in vivo trial ranged from 14.1 to 47.0%, and in the second from 3.6 to 35.1%, for the 28 days of the experiments. Efficacy for the in vitro trial was 47.38%. The dose recommended by the manufacturer of the product did not cause mortality to most of the ticks of this strain, and efficacy/resistance was not reverted or modified after 15 years (estimated 60 tick generations).
Assuntos
Acaricidas/farmacologia , Doenças dos Bovinos/tratamento farmacológico , Rhipicephalus/efeitos dos fármacos , Infestações por Carrapato/veterinária , Toluidinas/farmacologia , Acaricidas/uso terapêutico , Animais , Bovinos , Doenças dos Bovinos/parasitologia , Feminino , Larva/efeitos dos fármacos , Masculino , Rhipicephalus/crescimento & desenvolvimento , Infestações por Carrapato/tratamento farmacológico , Infestações por Carrapato/parasitologia , Toluidinas/uso terapêuticoRESUMO
Although co-infections of Trypanosoma vivax, Anaplasma spp., and Babesia spp. have been reported, knowledge gaps remain that need to be addressed. The present study evaluated the efficacy of enrofloxacin (7.5 mg/kg) against A. marginale in naturally infected cattle and cattle experimentally co-infected with T. vivax by observation of the variation in A. marginale parasitemia and packed cell volume (PCV) for 39 days. Bovines were distributed into two groups, each with six calves: T01 = animals immunosuppressed with dexamethasone and with latent anaplasmosis; T02 = animals immunosuppressed with dexamethasone, with latent anaplasmosis and experimentally co-infected with T. vivax on day 0 (D0). Animals of both groups were immunosuppressed with dexamethasone and received enrofloxacin (7.5 mg/kg) whenever mean values of parasitemia for A. marginale were ≥ 5% per group. Cattle of group T02 were also treated with isometamidium chloride (0.5 mg/kg) on D25. On D17 and D22 to D28 of the study, there was a higher (P ≤ 0.05) A. marginale parasitemia in animals of T02 than in those of T01. Animals of T01 required one enrofloxacin treatment to decrease A. marginale parasitemia, while those from T02 needed five treatments. From D5 to D37 of study, the mean values of PCV for calves from T02 were lower (P ≤ 0.05) than that for calves from T01. In conclusion, bovines co-infected T. vivax needed four more treatments with enrofloxacin to reduce A. marginale parasitemia and keep PCV values within reference standards.
Assuntos
Anaplasmose , Doenças dos Bovinos , Enrofloxacina/uso terapêutico , Parasitemia , Tripanossomíase Africana/veterinária , Anaplasma marginale , Anaplasmose/tratamento farmacológico , Animais , Bovinos , Doenças dos Bovinos/tratamento farmacológico , Doenças dos Bovinos/parasitologia , Tamanho Celular , Coinfecção/parasitologia , Coinfecção/veterinária , Parasitemia/tratamento farmacológico , Parasitemia/veterinária , Trypanosoma vivax , Tripanossomíase Africana/tratamento farmacológicoRESUMO
Bovine trypanosomosis has been spreading in Brazil. In the present study, we evaluated the spatial distribution, prevalence and risk factors of this disease in the state of Goiás, Brazil, and performed both molecular and phylogenetical analyses of Trypanosoma vivax. A total of 4049 blood samples were collected from cattle for a period of 2 years. The parasitological diagnosis was performed using the Woo method and a questionnaire was administered to the farmers to document risk factors associated with the disease in the herd. Positive samples were DNA sequenced and compared to GenBank codes. The prevalence of T. vivax was 8.84%, occurring on 24 ranches only in dairy cattle and mainly in the central and southern portions of the state. The acquisition of new animals infected with T. vivax and the administration of exogenous oxytocin to cows using the same syringe and needle were the main associated factors (P ≤ 0.05). After an outbreak, milk production decreased by 39.62%. The presence of biting flies (tabanids, Haematobia irritans and Stomoxys calcitrans) was not a risk factor (P > 0.05) for the occurrence of T. vivax. The epidemiological data demonstrate the importance of restricting the practice of auctions as well as eliminating the use of exogenous oxytocin in animals during milking. The samples tested by polymerase chain reaction were positive for T. vivax and were genetically homologous with T. vivax found in different states of Brazil and west Africa based on the 18S rRNA gene.
Assuntos
Trypanosoma vivax , Tripanossomíase Bovina/epidemiologia , Animais , Bovinos , Doenças dos Bovinos/epidemiologia , DNA de Protozoário , Surtos de Doenças/veterinária , Patologia Molecular , Prevalência , RNA Ribossômico 18S/genética , Fatores de Risco , Trypanosoma vivax/genética , Trypanosoma vivax/isolamento & purificaçãoRESUMO
The aim of the present study was to compare the infection capacity of Trypanosoma vivax experimentally inoculated through different routes in calves naturally infected with latent Anaplasma marginale. On Day 0 of the study, 25 calves (breed: Girolando) were divided into five groups. The first four groups of five calves each received approximately 1 × 106 trypomastigotes of T. vivax through the intradermal, subcutaneous, intramuscular and intravenous routes. Another five animals remained unaffected to serve as A. marginale naturally infected controls. The study of T. vivax was performed on all calves from D+1 to D+30 using the Woo, Brener and blood smear techniques. PCR was performed on Days +1, +3, +4, +5, +28, +29 and + 30. The results indicated that T. vivax was capable of infecting and developing the disease in the calves independent of the inoculation route. A positive correlation was found between T. vivax and rectal temperature (P ≤ 0.05) and a negative correlation was seen between the protozoan and globular volume (P ≤ 0.05). Latent A. marginale in the calves acted as co-infection for T. vivax. Jaundice was seen only in calves with a high parasitemia by A. marginale. Therefore, in areas with the confirmed presence of T. vivax in bovines, this protozoan should be included in the complex denominated "Bovine Parasitic Sadness", which currently encompasses only Anaplasma and Babesia.
RESUMO
The present study attempted to verify the prevalence of and risk factors for diarrhea-causing agents in dairy calves from Brazil. Additionally, ages with a higher risk of occurrence for each agent were verified by means of the receiver operating characteristic (ROC) curve. The collections were performed on 39 farms, belonging to 29 municipalities located in eight states of Brazil. It was possible to conclude that the prevalence of Coronavirus, Rotavirus, Cryptosporidium spp., Eimeria spp., and nematodes was 7.20% (95% CI 4.54-9.78), 6.37% (95% CI 3.85-8.89), 51.52% (95% CI 45.26-55.57), 3.46% (95% CI 2.24-4.67), and 3.46% (95% CI 2.24-4.67), respectively. Ages with higher probabilities of occurrence of these diseases in calves were < 10, > 8, > 6, > 37, and > 36 days, respectively. Diarrhea occurred more significantly (P < 0.0001) in animals less than 21 days old and mainly on those receiving milk through automatic feeders (P < 0.001). Cryptosporidium spp. were a risk factor for the occurrence of Rotavirus, and vice versa (P = 0.0039) and presented a positive correlation with Coronavirus (P = 0.0089). Calves that drink water from rivers, streams, and ponds had a higher chance of being infected by Eimeria spp. (P < 0.0001), as well as developing infection by nematodes (P < 0.0001). The results found in this study highlight the importance of studying the agents of diarrhea together, once they act as coinfection where the losses triggered for the owners will involve some of these agents simultaneously.
Assuntos
Doenças dos Bovinos/epidemiologia , Infecções por Coronavirus/veterinária , Criptosporidiose/complicações , Diarreia/veterinária , Infecções por Nematoides/veterinária , Infecções por Rotavirus/veterinária , Animais , Brasil/epidemiologia , Bovinos , Doenças dos Bovinos/parasitologia , Doenças dos Bovinos/virologia , Coronavirus/isolamento & purificação , Criptosporidiose/epidemiologia , Cryptosporidium/isolamento & purificação , Diarreia/parasitologia , Diarreia/virologia , Eimeria/isolamento & purificação , Fazendas , Fezes/parasitologia , Fezes/virologia , Feminino , Infecções por Nematoides/complicações , Prevalência , Curva ROC , Fatores de Risco , Rotavirus/isolamento & purificaçãoRESUMO
The present study aimed to evaluate under dairy farm conditions the predisposing factors, impact on milk production and productivity, and the role of Rhipicephalus microplus in the epidemiology of tick fever agents in Holstein calves grazing in a tropical region. A total of 4292 pure female Holsteins were evaluated at a commercial farm. Until April 2020, calves had contact with R. microplus for between 3 and 24 months, while after April 2020, no animal had further contact with ticks. Three times a week the rectal temperature (RT) of all animals was determined, and blood samples were collected for evaluation of tick fever (TF) agents from those that showed RT >39.3 °C. Specific treatment was performed against Anaplasma marginale, Babesia bigemina and Babesia bovis when these TF agents were diagnosed in the blood smears. The number of relapses and treatments for TF agents were sub-classified into scales (1, 2, 3, 4, 5, 6 or 7-10â¯treatments or relapses, and animals that received blood transfusions). Within each sub-class, the health data of calves during lactation along with productivity data were analyzed. Based in the results, whether an animal received colostrum enriched with powdered colostrum substitute, whether the animal was an embryo transfer calf, and the weight at which each calf was weaned were ascertained as factors leading to more recurrences or treatments against TF agents in post-weaned calves. On average, each recurrence of TF agents that a heifer presented between three and seven months decreased milk production by 213.5 liters in the first lactation. Calves that received a blood transfusion had lower milk production at first lactation; lower weight at first fixed-time artificial insemination (FTAI); older age at first FTAI; older age at first, second, and third calving; and delayed age at third calving by 140 days compared to the farm average. R. microplus was the main agent causing clinical cases of TF on the farm, and 10,770 treatments against TF agents were carried out when calves aged between three and seven months had contact with this tick species (2018 and 2019). When the animals no longer had contact with ticks (2022 and 2023), there were no recurrences or treatments against TF agents despite the presence on the farm of S. calcitrans, which can maintain the transmission of A. marginale to the herd.
RESUMO
The water can be a significant risk factor for the occurrence of cattle eimeriosis on farms located in tropical climate regions. This study aimed to assess the viability period of sporulated oocysts of bovine Eimeria spp. in water containing organic matter and to evaluate the efficacy of disinfectants against sporulated oocysts of this protozoa. Two experiments were conducted, each comprising in vitro and in vivo evaluations. In Experiment 1, the viability period of oocysts sporulated in buckets containing a solution composed of a mixture of feces with oocysts, water, and potassium dichromate was assessed. Quantifications and identification of Eimeria spp. oocysts were performed on days + 30, + 60, + 90, and every 30 days thereafter until no more oocysts were detected. Naïve calves were inoculated with this solution kept in the bucket for 6 and 12 months. In Experiment 2, the efficacy of various disinfectants (acetic acid, sodium hypochlorite, ethanol + acetic acid, and ammonia quaternary) against a new solution of sporulated oocysts and pH changes over time (10', 30', and 24 h) were evaluated in the laboratory. The most effective disinfectant was used to treat the water solution and inoculate the calves, and its efficacy was calculated. In Experiment 1, Eimeria spp. oocysts remained viable in the solution for up to 12 months. E. zuernii persisted until the end of the study period. Calves inoculated with the solution kept in the buckets for 6 and 12 months excreted at least four Eimeria species (E. zuernii, E. bovis, E. ellipsoidalis, and E. cylindrica). In Experiment 2, among the tested disinfectants, 3% acetic acid demonstrated the highest efficacy (10' = 80.9%; 30' = 87.9%; 24 h = 91.7%). The pH values of the solutions containing acetic acid ranged from 2.4 to 3.5. Calves that received the inoculum treated with 3% acetic acid did not excrete Eimeria spp. oocysts in feces during the study period (efficacy = 100%). In contrast, all animals in the control group excreted Eimeria spp. oocysts in feces. Future studies should be carried out to better understand the possible effects of cattle drinking water with 3% acetic acid.
RESUMO
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.
Assuntos
Acaricidas , Rhipicephalus , Feminino , Animais , Bovinos , Isoxazóis/uso terapêutico , LarvaRESUMO
This study evaluated the effect of different supportive treatments on PCV replacement of dairy calves naturally infected with tick fever (TF) agents, and treated with diminazene and enrofloxacin. Five products were tested as supportive treatments in four experiments. In these experiments, we used Girolando female calves (Gyr × Holstein, genetic ratio of 15/16 and 31/32 Holstein) four to six months old, raised in pasture, naturally infected with TF agents, and infested with R. microplus. Supportive treatment was administered once on day 0 of the study concurrently with specific treatment targeting TF agents. The animals were observed on days 0, 3, and 7. Oral or intravenous administration of a vitamin complex and mineral salts enhanced the increase in PCV and biochemical analytes present in the serum of calves naturally infected with TF agents. No positive effect on PCV values was observed with the administration of (1) invigorating tonic: calcium, casein-peptides and vitamin B12, (2) iron-based stimulant tonic and (3) metabolic tonic: vitamin A, vitamin D, and a fraction of polyunsaturated fatty acids. Supplementation by injection with Type III iron resulted in increased hemoglobin and PCV in treated animals. However, these results did not occur with iron citrate. Therefore, more studies with Type III iron need to be performed. Supportive treatment conferred no advantage in animals with no history of reduced PCV.
Assuntos
Doenças dos Bovinos , Animais , Bovinos , Feminino , Doenças dos Bovinos/tratamento farmacológico , Doenças dos Bovinos/terapia , Hematócrito/veterinária , Diminazena/análogos & derivados , Diminazena/uso terapêutico , Diminazena/farmacologia , Enrofloxacina/uso terapêutico , Enrofloxacina/administração & dosagem , Infestações por Carrapato/veterinária , Infestações por Carrapato/tratamento farmacológico , RhipicephalusRESUMO
This study aimed to verify the number of R. microplus annual generations in irrigated and non-irrigated pastures compared to the constant ideal environment. It also sought to evaluate the biology of the non-parasitic phase of this tick for each generation in these different areas of pasture; assess the larvae population dynamics in the pasture of each tick generation, and evaluate the R. microplus population dynamics parasitizing cattle in non-irrigated pasture. In the field experiment, two sub-areas were subjected to artificial irrigation (IRRI-A and IRRI-B) with artesian water, while the other two remained non-irrigated (NIRRI-A and NIRRIG-B). When more than 75â¯% of the total surviving engorged females from all 90 repetitions of each area (irrigated or non-irrigated) produced mature larvae within one tick generation, two cattle were infested with approximately 10,000â¯R. microplus larvae from the tick colony used in this study. On the 22nd day post-infestation, a new tick generation was started by releasing these females in different areas (IRRI-B and NIRRIG-B). This procedure was repeated successively, and each year was analyzed independently. In both the non-irrigated and irrigated areas, there were five generations of R. microplus per year. It can be observed that there the number of annual generations of ticks in this region has increased when compared to 30 years ago. Under the constant ideal temperature and humidity conditions (B.O.D. chamber), R. microplus completed an average of 6.59 generations. In the environment, the longest generation was the first (July to October), while the 2nd, 3rd and 4th (December to March) were the most similar to B.O.D. conditions. Although the number of generations was the same in the different areas, the population density of R. microplus larvae was higher in the irrigated area, probably because the irrigation provided milder temperatures, higher relative humidity and lower saturation deficit values during about eight hours per day. Between the 3rd and 5th generation of ticks, there was an overlap of larvae in the pastures, belonging to different generations, and at each peak of infestation observed in cattle between these generations, there were up to 30â¯% of larvae from the previous generation, and consequently up to 70â¯% of larvae from the new generation.
RESUMO
This study reports assessment of the sensitivity of diagnostic techniques to detect T. vivax in experimentally infected cattle. Additionally, it describes T. vivax extravascular parasitism during the acute and chronic phases of trypanosomosis and congenital transmission. The T. vivax diagnosis was compared using blood samples collected from the jugular, coccygeal and ear tip veins. For this study, 13 males and two females were infected with ≈ 1 × 106 viable T. vivax trypomastigotes (D0). One animal was kept as a negative control during the entire study. The 13 infected males were euthanized between 14 and 749 days post-infection (DPI). After confirming the cyclicity of both females (9 months of age), they were naturally mated with a bull. One female was euthanized at 840 DPI, and the other at 924 DPI. The two calves, one from each female, were euthanized at six months of age (924 DPI), and the negative control at 924 DPI. During this period, T. vivax in blood was assessed using direct methods (Woo test, cPCR, microscopic examination of fresh wet blood films and parasite quantification - Brener method), and serological methods (IFAT, ELISA, and IA). Tissue samples were collected from the liver, spleen, brain, cerebellum, heart, testicles, epididymis, kidneys, eyeballs, pre-scapular lymph nodes, ear tips, mammary glands, uterus, and ovaries. The protozoan DNA was examined using LAMP. There was no difference in the detection of T. vivax using the Woo test and Brener method among the jugular, coccygeal, and ear tip veins. The sensitivity of the detection methods varied depending on the disease phase. Direct methods (Woo test, Brener method, and cPCR) demonstrated higher sensitivity during the acute phase, while serological methods (IFAT, ELISA, and IA) were more sensitive during the chronic phase. Anti-T. vivax antibodies were detected up to 924 DPI. Tissue evaluation using LAMP demonstrated the presence of T. vivax DNA and associated histopathological changes up to 840 or 924 DPI. Only in mammary glands and ovaries was no DNA detected. The most frequently observed histopathological alteration was lymphohistioplasmocytic inflammatory infiltrate. No transplacental transmission of T. vivax was observed.
Assuntos
Doenças dos Bovinos , Trypanosoma vivax , Animais , Bovinos , Feminino , Masculino , Doenças dos Bovinos/transmissão , Doenças dos Bovinos/parasitologia , Doenças dos Bovinos/sangue , Doenças dos Bovinos/diagnóstico , Transmissão Vertical de Doenças Infecciosas/veterinária , Tripanossomíase Africana/veterinária , Tripanossomíase Africana/transmissão , Tripanossomíase Africana/diagnóstico , Tripanossomíase Africana/sangueRESUMO
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.
Assuntos
Eimeria , Haemonchus , Animais , Bovinos , Fenbendazol/uso terapêutico , Triazinas/uso terapêuticoRESUMO
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.