Abiotic and biotic determinants of tick burdens in the eastern rock sengi (Elephantulus myurus)

Abstract

Ticks are important vectors of pathogens of medical and veterinary importance worldwide.Despite their economic importance our current knowledge about the factors affecting tick prevalence and abundance in tropical and subtropical regions is rather limited. Both abiotic (e.g. temperature) as well as biotic variables (e.g. host sex) have been identified as key determinants of distributions. Eastern rock sengis or elephant shrews (Elephantulus myurus, Thomas & Schwann) are widely distributed throughout Africa and can harbour a large number of tick species and substantial tick burdens. In the current study we evaluated the contribution of climate and host factors on tick burdens of sengis. Throughout the year sengis carried high abundances of immature stages of a single tick species, Rhipicephalus sp. near warburtoni. There was no evidence that host parameters affected tick burdens. However, larval abundance decreased with increasing ambient temperatures and both larvae and nymphs were negatively affected by rainfall two months prior to the sampling month. In addition, nymphal burdens decreased with increasing minimum temperatures. Our results suggest that climate factors are the largest constraint for the immature stages of R. sp. near warburtoni and that eastern rock sengis could play a crucial role in the dynamics of tick-borne diseases due to the large tick burdens they can sustain.

Evidence for interspecific interactions in the ectoparasite infracommunity of a wild mammal

“…Our analyses revealed seasonal fluctuations for ticks and chiggers that quest from the environment. This is in accordance with the notion that ectoparasites that spend a large proportion of their life-cycle off-host are generally assumed to be predominately affected by environmental rather than host factors [ 30 , 40 , 48 , 49 ]. In contrast, the lack of seasonal effects observed for N. elephantuli are probably a result of the fact that lice spend their entire life-cycle on the host and are thus more dependent on ‘host microclimate’ than environmental factors [ 30 , 47 ].…”

“…However, seasonal differences in recruitment rates were only apparent for Rhipicephalus spp. suggesting that apart from environmental and host factors [ 40 , 41 ] interspecific interactions within the infracommunity may play a role in generating the seasonal patterns observed in this and other studies. This hypothesis deserves further attention in future studies.…”

“…Also, the study site of the current study and the locality studied in [ 43 ], which is located ca. 300 km south in South Africa’s Gauteng province, differ vastly with regards to climate, vegetation cover and small mammal community composition with Goro Game Reserve having a much hotter and drier climate with a continuous rocky landscape and scarce vegetation cover and a less diverse small mammal community comprised of four species (three rodents: Micaelamys namaquensis , Aethomys chrysopilus and Acomys spinossissimus ; and the study species) [ 40 , 45 ]. In contrast, at the Gauteng study site rocky outcrops are interspersed in grassland or savannah habitat and the small mammal community is much more diverse (nine rodents and two insectivores including the study species [ 32 ].…”

“…For the analyses we pooled the counts for ticks across stages since the abundance of nymphs was generally too low to permit a meaningful analysis according to life-history stage. Although this was not the case for Rhipicephalus warburtoni the abundance of larvae and nymphs was highly correlated (R S = 0.737, p < 0.0001) and both stages are present throughout the year [ 40 ]. In addition, the qualitative results for the separate stages corresponded to those for the pooled data.…”

Host species and environment drivers of ectoparasite community of rodents in a Mojave Desert wetlands

“…Abiotic drivers can be important factors in ectoparasite community structure, for example, rainfall and water sources which can affect abundance, developmental rates, and survival of ectoparasites and their hosts [ 30 , 31 ], particularly since most of the ectoparasites we found spend considerable time off the host. Even though in our study water depth was not significantly associated with variation in ectoparasite community composition, individual hosts had a higher number of chiggers in marshes with higher mean water depth.…”