Abstract
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.
Highlights
Ticks are among the most important global vectors of infectious pathogens of humans and animals [1]
We conducted an abattoir-based serial cross-sectional investigation of ticks at the anno-vulva region of cattle presented for slaughter and used a random effects model to correlate tick counts with a priori host, environmental and micro-climate factors as a means of evaluating their predictive value for measured tick abundance, with additional spatial analysis to determine the distribution of such an abundance
We have shown in our study that cattle tick abundance is influenced largely by season of the year and that the microclimatic conditions brought about by the seasonal flooding of the delta have a decisive effect on tick distribution during the dry seasons
Summary
Ticks are among the most important global vectors of infectious pathogens of humans and animals [1]. The rising global incidence of tick-borne diseases (TBDs) is indicative enough of the significant threats to human and veterinary public health posed by ticks and the diverse infectious pathogens they transmit [2]. The direct and indirect negative impact of tick infestation to domestic animal hosts is well-documented and ranges from significant production losses that includes meat, milk, eggs and hides, to deaths of the affected animals through blood loss and tissue invasion by secondary microbes as well as pathogens they themselves transmit during feeding. An understanding of the role played by these factors helps guide adoption of evidence-based husbandry management practices to sustainably control against ticks in domestic animals and is critical in the implementation of sound public safety guidelines aimed at guarding against human infestation and potential debilitating tick-borne pathogens (TBPs) they transmit
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