Predictive Analytics of Cattle Host and Environmental and Micro-Climate Factors for Tick Distribution and Abundance at the Livestock–Wildlife Interface in the Lower Okavango Delta of Botswana

Tick distribution and abundance is influenced by several factors that include micro-climate and environmental and host factors. Contextual understanding of the role played by these factors is critical to guide control measures. The aim of this study was to determine the predictive value of these factors for changes in tick distribution and abundance at the livestock–wildlife interface of the lower Okavango Delta. A two-stage quota sampling design was adopted to select 30 clusters of seven cattle each for tick investigation. Tick investigation was done by lifting the tail to count the total number of ticks at the anno-vulva region during the four meteorological seasons of the year. Additional data were collected on ear tag number, location of origin, sex, age, body condition score (BCS), season of the year, stocking density, and Normalized Difference Vegetation Index values of source terrain. A random effects model was used to evaluate predictive value of the above for tick abundance. Additional mapping of tick distribution pattern in the abattoir catchment area was conducted using spatial autocorrelation and hot-spot analysis. Tick intensity of infection increased linearly from males to females (Z = 3.84, p < 0.001), decreased linearly from lower to higher BCS (Z = −4.11, p < 0.001), and increased linearly from cold-dry through dry to wet seasons (Z = 10.19, p < 0.001). Significant clustering of neighboring crushes on account of tick count was noted in the late-hot-dry season, with high tick count in crushes located along the seasonal flood plains and low tick counts in those located in the dry grasslands. It was concluded from this study that cattle tick abundance is influenced largely by season of the year and that the micro-climatic conditions brought about by the seasonal flooding of the delta have a decided effect on tick distribution during the driest of the seasons. Our study has, for the first time, profiled drivers of tick distribution and population growth in this unique ecosystem. This has the potential to benefit human and veterinary public health in the area through implementation of sustainable tick control strategies that are not heavily reliant on acaricides.

Efficacy of a novel topical combination of esafoxolaner, eprinomectin and praziquantel against Amblyomma americanum in cats

Esafoxolaner, a purified enantiomer of afoxolaner with insecticidal and acaricidal properties, is combined with eprinomectin and praziquantel in NexGard® Combo, a novel topical endectoparasiticide product for cats. The efficacy of this novel formulation was assessed in two experimental studies against induced infestations with Amblyomma americanum, a tick species of major importance, highly prevalent in a large southeastern quarter of the United States. In each study, 10 cats were randomly allocated to a placebo control group and 10 cats to a novel formulation treated group. Infested cats were treated topically once at the minimum recommended dose. Both studies were designed to test curative efficacy on existing infestation, 72 h after treatment, and to test preventive efficacy, 72 h after subsequent weekly (Study #1) or fortnightly (Study #2) infestations for one month. For each infestation, all cats were infested with 50 unfed adult A. americanum. At each tick count, in both studies, at least 8 in 10 placebo control cats were infested with 13 (26%) or more live ticks, demonstrating adequate infestation throughout the studies. Curative efficacy of the novel formulation was 99% in both studies; preventive efficacy was 92% and 100% for at least one month.

Efficacy of a novel topical combination of esafoxolaner, eprinomectin and praziquantel against Rhipicephalus sanguineus in cats

Esafoxolaner is a purified enantiomer of afoxolaner with insecticidal and acaricidal properties. It is combined with eprinomectin and praziquantel in a novel topical endectoparasiticide formulation for cats. The efficacy of this novel formulation was assessed in an experimental study against induced infestation of Rhipicephalus sanguineus ticks. Twenty cats were randomly allocated to either a placebo control group or a treated group in a 1:1 ratio. Infested cats were treated topically once at the minimum recommended dose. The study was designed to assess curative efficacy 48 h after treatment and to test preventive efficacy 48 h after weekly infestations for 2 months. At each weekly infestation, all cats were infested with 25 male and 25 unfed female R. sanguineus ticks. At each tick count, at least 6 in 10 control cats had a retention of 13 (26%) or more live ticks, demonstrating adequate infestation throughout the study. Curative efficacy on existing tick infestation was 90%; preventive efficacy over the following 6 weeks was at least 96%.

Genetic and environmental factors that affect tick infestation in Nelore x Angus crossbreed cattle

ABSTRACT: This study evaluated the effects of seasons and latitude on tick counting and determined the best model to estimate genetic parameters for tick count and hair coat. Records of animals naturally exposed to ticks on farms in several Brazilian states and in Paraguay were used. The ANOVA was used to verify the effects of seasons and latitude on the tick count trait. Spring was the season with the highest average, followed by summer and autumn, which showed no differences between them. The winter presented the lowest average values. Latitude -11° had the highest mean value followed by latitude -18°. The Bayesian approach was used to evaluate tick count and hair coat and to identify a suitable model for estimating genetic parameters for use in genetic evaluations. The data were analyzed using an animal model with four different specifications for “fixed” purposes. The inference was based on a Markov chain Monte Carlo (MCMC). The criteria for selection of the Bayesian model indicated that the M1 model, which considered the breed composition in the contemporary group, was superior to the other models, both for tick count and hair coat. Heritability estimates for tick count and hair coat obtained using the M1 model were 0.14 and 0.22, respectively. The rank correlations between the models for tick count and hair coat were estimated and reordering was verified for tick count. The estimated genetic correlation between tick count and hair coat traits was negative (-0.12). These findings suggest that different genes regulate tick count and hair coat.

Effects of extended-release eprinomectin on fescue toxicosis, performance, and reproduction on fall-calving beef cows

The objective of this experiment was to evaluate effects of extended-release eprinomectin on fescue toxicosis and impacts on performance and reproduction in fall-calving beef cows. Fall-calving Angus × Simmental multiparous cows [n = 335; age = 5.8 ± 2.1 yr; 586.5 ± 6.0 kg body weight (BW); 5.48 ± 0.05 body condition score (BCS)] were stratified by BW, age, and BCS and randomly assigned to one of three treatments. Treatments included a spring injection of extended-release eprinomectin (SERE) on day 0, a fall injection of extended-release eprinomectin injection (FERE) on day 84, and a saline control (CON). All treatments were administered at a rate of 1 mL/50 kg BW. Prior to the experiment, all cows were treated with oral fenbendazole to minimize parasite load. Cows grazed endophyte-infected tall fescue. Hair coat score (HCS), BW, and BCS were recorded on all cattle. Fecal egg count (FEC), respiration rate (RR), horn fly and tick count, hematocrit (% packed cell volume, PCV), and serum prolactin were analyzed on a subset of cows (35/treatment). On day 194, cows were artificially inseminated (AI) and 11 d following AI were exposed to bulls for 51 d. Milk production was estimated on day 210 on a subset of 85 cow–calf pairs (28–29/treatment). There was a tendency for a treatment × time interaction (P = 0.07) for FEC likely driven by an increase in FEC of the CON cattle at day 126 compared to SERE and FERE. There was a tendency for a treatment × time interaction (P = 0.06) for cow BW, largely driven by time differences; however, there was no effect of treatment (P = 0.84) on BW. There was no difference (P ≥ 0.13) in cow PCV, fly and tick count, BCS, HCS, RR, and serum prolactin throughout the experiment. Additionally, there was no difference (P ≥ 0.46) in Julian calving date, calf birth BW, or milk production between treatments. Interestingly, heifer calves born to FERE dams tended to have greater (P = 0.06) weaning BW compared to heifer calves born to CON dams. In addition, there was no difference (P ≥ 0.17) in heat patch scores, AI conception rates, or overall pregnancy rates between treatments. Extended-release eprinomectin did not impact cow growth performance, reproductive performance or fescue toxicity symptoms when grazing endophyte-infected tall fescue; however, calf weaning BW tended to be improved.

COMPARATIVE STUDY OF CATTLE TICK RESISTANCE USING GENERALIZED LINEAR MIXED MODELS

Comparison of tick resistance in Bos taurus indicus (Nelore) and Bos taurus taurus (Simmental and Caracu) subspecies was investigated utilizing generalized linear mixed models (GLMMs) with Poisson and Negative binomial distributions. Nelore animals (NE) are known to present greater resistance than t. taurus. Difference between tick resistance in Simmental (SI) and Caracu (CA) breeds has never been reported previously. Three artificial tick infestations were conducted to evaluate tick resistance in these breeds. The statistic point of the present study was to show alternative models for the evaluation of tick count data, the GLMMs. Analysis for tick resistance by GLMM with Negative binomial distribution has never been assessed previously. The analyses were performed by the use of the PROC GLIMMIX procedure of the SAS program. The results showed that GLMM with Negative binomial distribution is appropriated to evaluate tick count data with excess of zero observations avoiding overdispersion problems. Finally, considering multiple comparisons with the Bonferroni test, different pattern of tick infestation was observed for the studied breeds, suggesting that NE is the most resistant breed followed by CA.