Lk. Page et al., Changes in transmission of Baylisascaris procyonis to intermediate hosts as a function of spatial scale, OIKOS, 93(2), 2001, pp. 213-220
Physical changes in landscapes alter the abundance and distribution of spec
ies. Higher-order effects can occur when changes in ecological processes re
sult in altered interspecific interactions and subsequent changes in a spec
ies' abundance or persistence. Baylisascaris procyonis, a roundworm parasit
e of raccoons (Procyon lotor), is pathogenic to numerous small vertebrates
that serve as intermediate hosts, including white-footed mice (Peromyscus l
eucopus). Raccoons have responded positively to agriculturally induced chan
ges in landscapes, with potential consequences for intermediate hosts of B.
procyonis. We examined white-footed mice from a homogeneous, predominantly
forested landscape in south-central Indiana and a heterogeneous, predomina
ntly agricultural landscape in northwestern Indiana for presence of larval
B. procyonis. We compared prevalence of infection, intensity of infection,
and average number of larvae per mouse between the landscapes, and among fo
rest patches within the highly fragmented agricultural landscape. Prevalenc
e, intensify of infection, and average number of larvae were significantly
higher in the highly fragmented landscape. Within the agricultural landscap
e, regression models predicted probability of infection, intensity of infec
tion, and average number of larvae per mouse per patch as functions of fore
st patch area and isolation. We conclude that positive responses of raccoon
s to agriculturally induced fragmentation of forests have resulted in incre
ased encounter rates between white-footed mice and infective stages of B. p
rocyonis between and within landscapes, resulting in increased transmission
of the parasite to intermediate hosts.