Prospective Studies of Bartonella of Rodents. Part I. Demographic and Temporal Patterns in Population Dynamics

The temporal dynamics of Bartonella infections in a rodent community were described by repeatedly capturing and sampling individual animals. Among six rodent species, from which bartonellae were isolated, cotton rats(Sigmodon hispidus) accounted for >98% of the bacteremic animals. All cotton rats captured four or more times were Bartonella-culture positive at least once. The lowest monthly prevalence of Bartonella in cotton rats was in June (49%) and the highest was in October (95%). Prevalence of Bartonella infection increased to >90% among juvenile and subadult rats before declining to <40% among the largest-oldest individuals. Bacteremia levels ranged between 40 and 4.0 × 10⁶ colony forming units (CFU) per 1 mL of blood. Male cotton rats had significantly higher CFUs than females (p = 0.006). The median of Bartonella bacteremia decreased monotonically by age group among cotton rats. Although Bartonella infections were highly prevalent among cotton rats, only 8.5% of rats had reactive antibodies at titers of ≥1:32 and none had antibodies titers of >1:256. Vector-Borne Zoonotic Dis. 4, 285–295.