Ectoparasite load of small mammals in the Serengeti Ecosystem: effects of land use, season, host species, age, sex and breeding status

Ectoparasite load in small mammals can be influenced by both environmental conditions and host species characteristics. However, the nature of these influences is poorly understood in many ecosystems. We used zero-inflated negative binomial (ZINB) regression models with a log link function to assess variation in ectoparasite load among 19 small mammal host species across different land uses (protection in a park, pastoralism and agriculture), habitat types, seasons, age classes, sexes and breeding statuses. We collected 4258 ectoparasites from 612 individual belonging to 19 different species of small mammals. The average ectoparasite load per individual was higher in the pastoral and agricultural lands than in the National Park. Ectoparasite load varied among species and was the highest for the four common and generalist small mammal species (Aethomys sp., Arvicanthis niloticus, Mastomys natalensis, and Gerbilliscus vicinus), most notably in the disturbed pastoral and agricultural lands. It was also higher in the dry than the wet season and for adult males than adult females. These patterns partly reflect the greater mobility of small mammals in the drier conditions; in addition the large body size and home range of males increase the likelihood of encountering parasites. Human disturbance was associated with elevated ectoparasitic load among the small mammals and hence elevated risk of transmission of ectoparasites to humans. As a result, understanding the effect of habitat disturbance on ectoparasite load and its link to zoonotic disease risk should be an important conservation goal and public health priority. Moreover, effective pest control strategies should consider variation in ectoparasite load with land use, habitat type, season and species characteristics.