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.
Rhipicephalus microplus is the most significant tick of livestock and its control is particularly challenging due to its resistance to commercial acaricides. Pasture rotation is considered a ...management strategy that could help control R. microplus, however, the literature only contemplates mathematical models and little is known about the effects of this practice in the field. The objective of this work was to determine whether pasture rotation is an efficient method for controlling R. microplus. Two different experiments were performed that involved groups of continuous and rotational grazing bovines. Female ticks measuring 4.5–8.0 mm were counted on animals while larvae in pasture were counted using the flannel drag technique. Treatment for infested bovines was applied when the average group tick count was ≥30 females. The results showed that rotational grazing (with 20-day periods of rest) had a higher tick count on-host than continuous grazing (P < 0.05) and additional bovine treatment was needed. Sixty and 105 days were needed to re-infest and disinfest pasture of R. microplus larvae, respectively. The first treatment of bovines occurred 91 days after the animals were placed in a closed area. The results indicate that rotational grazing is not an efficient way to control R. microplus.
•Pasture rotation did not decrease R. microplus parasitism on-host and need further treatment•Took 105 days to disinfest the pasture with tick larvae after bovines leaved the area•Took 60 days re-infested a closed area with tick larvae after bovine entrance there
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.
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.
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.
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).
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.
Avermectin toxicity in bovines less than thirty days old de Castro Rodrigues, Daniel; Buzullini, Carolina; Pereira, Tiago Arantes ...
Research in veterinary science,
June 2018, 2018-Jun, 2018-06-00, 20180601, Letnik:
118
Journal Article
Recenzirano
Odprti dostop
The present study was designed to evaluate possible adverse effects of different dosages of avermectins (abamectin and a combination of ivermectin + abamectin) administered subcutaneously in calves ...less than one month of age. Clinical as well as biochemical parameters of blood and cerebrospinal fluid (CSF) were evaluated for animals subjected to various treatments. Thirty-five calves were divided into seven groups of five animals each: T01 (control), T02 (abamectin 200 μg/kg), T03 (abamectin 400 μg/kg), T04 (abamectin 600 μg/kg), T05 (ivermectin 450 μg/kg + abamectin 250 μg/kg), T06 (ivermectin 900 μg/kg + abamectin 500 μg/kg) and T07 (ivermectin 1350 μg/kg + abamectin 750 μg/kg). Cerebrospinal fluid and blood samples were collected on day zero (treatment day) and on days 1, 7 and 14 following treatment. The biochemical parameters measured in blood samples were total protein and the AST, GGT and alkaline phosphatase enzymes. In CSF samples, color, aspects, pH, density, cellularity, total proteins, glucose and the CK, ALT and LDH enzymes were evaluated. No neurological toxicity or biochemical changes in the CSF or blood that could be correlated to administration of tested products were observed in this study. Though it is well known that abamectin may lead to intoxication in bovines less than four months of age, based on data from the present study, no adverse clinical effects to the CSF or blood were observed in calves <30 days old that had received up to 600 μg/kg abamectin formulations and up to 1350 μg/kg ivermectin +750 μg/kg abamectin associations. It is possible that the level and activity of the multiple drug resistance gene (MDR1 - ABCB1) present in the calves may have influenced the results obtained in this study. Future studies should be carried out.
•The present evaluate adverse effects of different dosages of avermectins in calves•Up to 600 μg/kg abamectin and 1350 μg/kg iver +750 μg/kg aba were used.•Clinical, biochemical parameters and cerebrospinal fluid (CSF) were evaluated.•No clinical or changes in CSF could be correlated to administration of testes products.•It was not possible to observe clinical, CSF and blood-related adverse effects in calves.
•Five peaks of Rhipicephalus microplus females on host were observed.•Five peaks of Rhipicephalus microplus larvae infestations on pastures.•Insolation, rainfall, and temperature influenced R. ...microplus seasonal dynamics.•Saturation deficit of the atmosphere influenced R. microplus seasonal dynamics.•Temperature possibly increase the number of tick annual peaks.
The present study evaluated over two years the seasonal dynamics of Rhipicephalus microplus in a Cerrado biome of midwestern Brazil (Goiânia, Goiás) and correlated the current climatic conditions (environmental temperature, insolation, rainfall, relative humitidy and saturation deficit of the atmosphere) of this site with 30 years ago. In addition, the data collected in the present research were compared with climatic conditions data and R. microplus population dynamics conducted by our group in other regions (Formiga, Minas Gerais and Jaboticabal, São Paulo) within the same biome. For the parasitic phase dynamics, R. microplus females (4.5–8.0 mm) counts were performed on tick natural infested cows kept in Panicum maximum paddocks. To verify the larvae dynamics on pasture the flannel dragg technique on natural infested pasture was performed, and the height of the grass was measured. Five peaks of engorged R. microplus females on animals and larvae infestations on pastures were observed. Being three and two peaks during the rainy and dry season of the year, respectively. Insolation (r = 0.8758; P = 0.00009; R² = 0.7670), rainfall (r = -0.8572; P = 0.0002; R² = 0.7348), maximum environmental temperature in summer (r = 0.9999; P < 0.0087; R² = 0.9988) and the saturation deficit of the atmosphere in autumn (r = -0.9789; P = 0.0211; R² = 0.9582) influenced the seasonal dynamics of R. microplus larvae on pastures. While the forage height did not influence the number of larvae found on pasture (r = 0.1545; P = 0.7682; R² = 0.0239). The comparison between the climatic data of the last 30 years with the current climatological data (2012 to 2019) in the state of Goiás, and the comparison with R. microplus population dynamics from other two locations in the same biome indicated that the increase of the environmental temperature due to the global warming possibly is a determining factor which increase the number of one or up two tick annual peaks. In addition, this climatic variable was responsible for increase the population density of ticks on pastures and animals observed in July/winter of the present study, in comparison to other regions with the same biome, as discussed in this work.
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