Effects of precipitation on parasite burden along a natural climatic gradient in southern Africa - implications for possible shifts in infestation patterns due to global changes

Abstract

As a consequence of environmental change, it is expected that shifts in temperature and precipitation patterns will infl uence parasite communities and their hosts with unpredictable impact. Parasites play a vital role in ecosystems but there is only limited quantitative data which describe the eff ects of environmental parameters under natural conditions. We investigated the infl uence of rainfall, relative humidity and temperature on the prevalence, abundance and infection intensity of nematodes in southern Africa by studying the gastro-intestinal helminth community of the striped mouse Rhabdomys pumilio. Along a precipitation gradient from the Cape of South Africa to northern Namibia we trapped 470 mice over a geographical distance of about 1400 km. Faecal egg counts of 439 sampled individuals and dissections of 161 gastro-intestinal tracts revealed 15 diff erent helminth species. Th e most abundant nematode species harboured in 62.6% of all infected mice were the oxyurid Syphacia obvelata followed jointly by two species (Heligmonina spira and Neoheligmonella capensis) of the subfamily Nippostrongylinae (43.7%). We found a signifi cant positive correlation between mean annual precipitation (rainfall and relative humidity) and nematode infestation rates of animals and a negative correlation with temperature. In addition, we found associations between precipitation and diff erent qualitative measurements of parasite burden (mean nematode species richness, mean number of nematode worms and infection intensity per individual host). Th e similarity in nematode species composition decreased with distance between all study sites. Our study indicates for the fi rst time an association between climatic variables and parasite prevalence and abundance along a continuous natural climatic gradient in a small mammal. Th ese results might be incorporated in the development of models which can predict possible threats for the balance of ecosystems and shifts in infestation patterns due to global changes.

Insights into the Complex Associations Between MHC Class II DRB Polymorphism and Multiple Gastrointestinal Parasite Infestations in the Striped Mouse

“…Further pleiotropic effects were revealed in the principal component analysis as well as the co-inertia analysis. Both showed oppositions between S. obvelata and A. tetraptera which co-occur in the same habitats and thus host specimen [38]. Often different helminth species in the same host specimen cause competition for nutrients and space [62], [63].…”

“…A more detailed description about the site-specific meteorological variables can be found in Froeschke et al [38]. Samples were taken twice, between November 2004–March 2005 and then again June–August 2006.…”

Helminth communities in murid rodents from southern and northern localities in Lao PDR: the role of habitat and season

“…More rarely, the roles of habitat and the level of human influence have been specifically investigated (Udonsi 1989;Kataranovski et al, 2008;Chaisiri et al, 2010;Froeschke et al, 2010;Milazzo et al, 2010;Lutermann & Bennett, 2012).…”

Determinants of Helminth Infection in a Subterranean Rodent, the Cape Dune Mole-Rat (Bathyergus suillus)

“…Extrinsic factors such as rainfall and temperature, on the other hand, often act on the parasite directly, resulting in variation in the spatial and temporal distribution of parasites (Poulin, 2007). Such extrinsic factors and, as a consequence, the distribution of parasites often differ between habitats, and, accordingly, habitat use can determine the exposure of hosts to parasites (Froeschke et al, 2010).It has repeatedly been noted that the subterranean niche of fossorial rodents may limit their exposure to parasites, and this has been linked to the low parasite species richness encountered in a number of subterranean rodents (Gardner, 1985;Hafner et al, 2000;Rossin and Malizia, 2002;Rossin et al, 2010). Rodents from a range of families have adapted to a subterranean lifestyle, and, despite their diverse origin, they show remarkable similarities with respect to morphology, physiology, and basic life history traits.…”

“…Extrinsic factors such as rainfall and temperature, on the other hand, often act on the parasite directly, resulting in variation in the spatial and temporal distribution of parasites (Poulin, 2007). Such extrinsic factors and, as a consequence, the distribution of parasites often differ between habitats, and, accordingly, habitat use can determine the exposure of hosts to parasites (Froeschke et al, 2010).…”