Interactions between ticks and dogs in the greater Bloemfontein
Jocobs, Phillip Andrew Herman
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The present study was conducted in the greater Bloemfontein area and focussed on the interaction between ticks and dogs. The sampling localities included Bloemfontein, Botshabelo and Thaba Nchu, and various sub-divisions thereof Rhipicephalus sanguineus and Haemaphysalis leachi, being dog ticks and the expected dominant species, were subject to close scrutiny. The present study was a comparative one which consisted of both field and laboratory work and which was designed to address several objectives. The first objective was to study tick diversity, prevalence and relative density. The second objective was to study the effect of various abiotic factors (temperature, relative humidity and photoperiod) on the development rate and survival of eggs, larvae and nymphs of the two dominant species. The third objective was to examine the influence that social factors (e.g. attitudes of dog owners, socio-economic levels, education and awareness, development levels in terms of infrastructure) have on the relationship between ticks and dogs. The results of the present study indicated that the dogs in the greater Bloemfontien were parasitised by at least nine different species. The species with the highest prevalence (and relative density) were R. sanguineus (73.5% and 27.4) and H. leach; (22.4% and 5.8). Other species constituted less than 1.2% of the total sample and were regarded as being incidental. These species included Boophilus decoloratus, Hyalomma truncatum, Rhipicephalus evertsi evertsi, Ixodes rubicundus, Rhipicephalus sp., Rhipicephalus gertrudae and Rhipicephalus follis. There was a clear distinction between the different attachment sites of the two dominant species and both species displayed seasonal patterns. Greater numbers of the two dominant species were found during the warm summer months and very few during the cold winter months. Daily egg production of the two dominant species was similar to that of other ixodid ticks while the pre-oviposition and incubation periods decreased with an increase in temperature. Pre-oviposition periods for R. sanguineus ranged from 4.8 (25°C, 90%RH) to 21.0 (15°C, 40%RH) days and for H. leachi from 4.3 (30°C, 90%RH) to 12.1 (15°C, 40%RH) days. Incubation periods for R. sanguineus ranged from 19.0 (30°C, 90%RH) to 72.0 (15°C, 90%RH) days and for H. leachi, from 15.5 (30°C, 90%RH) to 66.7 (15°C, 40%RH) days. The fecundity ofR. sanguineus ranged from 10.3 (15°C, 40%RH) to 17.2 (25°C, 90%RH), while for H. leachi it ranged from 7.7 (15°C, 40%RH) to 16.3 (15°C, 90%RH) eggs per mg body mass. The fecundity for both species, at a specific temperature, increased with an increase in relative humidity. Generally, unfed larvae and nymphs of both species survived for longer periods at lower temperatures. The pre-moult period of larvae and nymphs of both species decreased with an increase in temperature. Both engorged larvae and nymphs of both species displayed a circadian drop-off rhythm. The general condition of the dogs in the affluent localities were better than those found in other localities. Dogs tested positive for Ehrlichia canis and Ehrlichia chaffeensis in all localities but was the highest in Thaba Nchu. The mean number of dogs in the different localities did not differ significantly. Generally speaking most respondents did indicate concern for their dogs and many saw ticks as being a problem. However, the level of education was a determining factor when it came to the understanding of the relevant diseases and the vectors thereof Ignorance and a lack of necessary resources were important factors contributing to poor animal health in the greater Bloemfontein. The attitudes displayed by dog owners also contributed towards the general condition of the dogs sampled. There is little information available on R. sanguineus and H. leachi generally and particularly in the greater Bloemfontein. The present study has provided some basic information regarding (i) the diversity, prevalence and relative density, (ii) the effects of abiotic factors on eggs, larvae and nymphs, and (iii) the influence that social factors (particularly the attitudes of dog owners) have on the relationship between these two dominant tick species and dogs This type of information can contribute substantially towards endeavours to effectively control the tick species that parasitise our dogs.