Interacting effects of wildlife loss and climate on ticks and tick-borne disease

Abstract

Both large-wildlife loss and climatic changes can independently influence the prevalence and distribution of zoonotic disease. Given growing evidence that wildlife loss often has stronger community-level effects in low-productivity areas, we hypothesized that these perturbations would have interactive effects on disease risk. We experimentally tested this hypothesis by measuring tick abundance and the prevalence of tick-borne pathogens ( and spp) within long-term, size-selective, large-herbivore exclosures replicated across a precipitation gradient in East Africa. Total wildlife exclusion increased total tick abundance by 130% (mesic sites) to 225% (dry, low-productivity sites), demonstrating a significant interaction of defaunation and aridity on tick abundance. When differing degrees of exclusion were tested for a subset of months, total tick abundance increased from 170% (only mega-herbivores excluded) to 360% (all large wildlife excluded). Wildlife exclusion differentially affected the abundance of the three dominant tick species, and this effect varied strongly over time, likely due to differences among species in their host associations, seasonality, and other ecological characteristics. Pathogen prevalence did not differ across wildlife exclusion treatments, rainfall levels, or tick species, suggesting that exposure risk will respond to defaunation and climate change in proportion to total tick abundance. These findings demonstrate interacting effects of defaunation and aridity that increase disease risk, and they highlight the need to incorporate ecological context when predicting effects of wildlife loss on zoonotic disease dynamics.

Comment on Titcomb et al. 's ‘Interacting effects of wildlife loss and climate on ticks and tick-borne disease'

“…This is exactly in line with previous studies on the effect of exclosure size on tick population dynamics: tick abundance tends to increase in small exclosures as they are no longer picked up by their wildlife hosts, but decreases in larger exclosures [7][8][9]. The apparent increase in adult tick abundance reported by Titcomb et al [1] is therefore likely to be an effect of the small size (1 ha) of their exclosures.…”

“…Understanding the impact of anthropogenic disturbances such as defaunation and climate change on vector-borne disease risk is critically important. Titcomb et al [1] experimentally tested the interactive effects of these perturbations on tick-borne disease risk within long-term, size-selective, large-herbivore exclosures, replicated across a precipitation gradient in East Africa. They found that the abundance of adult ticks increased with increasing degrees of wildlife exclusion (from exclusion of only mega-herbivores to exclusion of all herbivores greater than or equal to 5 kg) and that this effect was stronger in more arid sites.…”

Conservation lessons from large‐mammal manipulations in East African savannas: the KLEE, UHURU, and GLADE experiments

“…The increase in small-mammal density inside exclosures propagates even further throughout the food web (in addition to increases in snakes, see above), leading to increased ectoparasite abundance and the risk of tick-and flea-borne diseases [66][67][68] (Fig. 4B), as well as of rodent-borne macroparasitic helminths.…”

Repeatable differences in exploratory behaviour predict tick infestation probability in wild great tits

“…The likelihood and number of ticks carried by an individual bird vary as a function of multiple interacting ecological factors affecting tick survival in the breeding habitat, such as temperature or humidity (Lindgren et al 2000; Oorebeek and Kleindorfer 2008; Kiffner et al 2011; Titcomb et al 2017), host breeding density (Oorebeek and Kleindorfer 2008; Takumi et al 2019), and vegetation type/coverage (Kiffner et al 2011; К. Tack et al 2012; W.…”