Seroprevalence and Attempted Transmission of Anaplasma phagocytophilum and Borrelia burgdorferi from Naturally Infected Ticks to Cats

Abstract

A. phagocytophilum and B. burgdorferi are among the leading tick-borne disease agents in the United States. Both agents are of veterinary and public health significance as dogs, cats, and human beings are known to be susceptible. B. burgdorferi and A. phagocytophilum are transmitted trans-stadially by either nymphs or adults of either the black-legged tick (Ixodes scapularis) or the western black-legged tick (Ixodes pacificus). Little information is available regarding either the prevalences of these agents in cats or the dynamics of vector transmission. Four hundred and sixty feline blood samples from sites throughout the United States were assayed for antibodies to A. phagocytophilum using an indirect immunofluorescence assay (IFA). Samples that were positive by IFA were subjected to polymerase chain reaction (PCR) analysis to measure presence of bacterial DNA. In an attempt to determine the minimum transmission times of A. phagocytophilum and B burgdorferi, wild caught adult I. scapularis ticks were applied to cats and removed at 8, 16, 24, and 36 hours after attachment. Blood was collected on days 42, 56, 72, 84 and 98 after tick removal and examined using both IFA and PCR. Biopsies were collected from sites of tick attachment and examined for A. phagocytophilum and B. burgdorferi-specific DNA by PCR procedures.

Two samples from Providence, Rhode Island were positive using an indirect immunofluorescence assay at a titer of 1:200; however, whole blood samples were not provided and positivity could not be corroborated by PCR. Eighteen other samples (12/90 from Florida, 3/45 from Michigan, and 3/23 from California) appeared positive at a titer of 1:50, however bacterial DNA was not detected using PCR procedures. The remaining samples were seronegative as determined by IFA. All ticks were negative by PCR for A. phagocytophilum, however, B. burgdorferi was detected in two of eight ticks attached to the 8 hour cat and five of seven attached to the 16 hour cat. Fourteen of 31 pooled unattached ticks were positive for B. burgdorferi and one was positive for B. miyamotoi. Cats remained antibody negative for both A. phagocytophilum and B. burgdorferi throughout the transmission study. Biopsy sites from all cats were negative for both A. phagocytophilum and B. burgdorferi. These results demonstrate that natural infection of A. phagocytophilum in cats is uncommon. Methodologies used in the study to determine transmission times could be of value in determining times necessary for vector-mediated transmission of agents. However, several features of the model could be improved. These potential modifications are discussed below.