Exposure to anaplasma phagocytophilum and ticks in gray foxes (Urocyon cinereoargenteus) in northern Humboldt County, California

Title:	Exposure to anaplasma phagocytophilum and ticks in gray foxes (Urocyon cinereoargenteus) in northern Humboldt County, California
Author:	Gabriel, Mourad Wisam
Abstract:	Exposure to Anaplasma phagocytophilum and ticks in gray foxes (Urocyon cinereoargenteus) in northern Humboldt County, California. Granulocytic anaplasmosis is an emerging zoonotic tick-borne disease with over 1300 human cases documented in the US since 2002. Although granulocytic anaplasmosis has been documented in numerous wildlife species, gray foxes (Urocyon cinereoargenteus) have not been evaluated previously for exposure to this agent. During a 16 month period in 2003-2004 within the Hoopa Valley Indian Reservation, Humboldt County, California, 54 individual gray foxes were live-trapped, of which 16 individual foxes later were recaptured. Four tick species were found on the foxes: Ixodes pacificus adults and nymphs, Ixodes texanus adults and nymphs, D. variabilis adults, and a D. occidentalis adult. The number of I. pacificus adults found on captured foxes differed (p < 0.001) among the seasons with winter having the highest number per fox (X¯ 8.4 ± 0.97, n= 9) compared to fall (X¯ 0.27 ± 0.62, n = 22) and summer (X¯ 0.71 ± 0.59, n = 24). The number of I. pacificus removed from foxes in spring (X¯ 6.1 ± 0.77, n = 15) did not differ significantly than those removed in winter. Foxes in the backcountry had significantly more (p < 0.001) I. pacificus (X¯ 4.4 ± 0.54, n=30) than urban caught foxes (X¯ 1.5 ± 0.46, n= 40). The number of I. texanus nymphs found on captured foxes differed (p < 0.05) among the seasons with spring having the highest number per fox (X¯ 6.9 ±1.75, n=15), compared to fall (X¯ 0.59 ± 1.44, n = 22), winter (X¯ 0.67 ± 2.26, n = 9) and summer (X¯ 0.83 ± 1.38, n = 24). Twenty eight of the 54 (52%) gray foxes were Anaplasma phagocytophilum seropositive by indirect immunoflorescent antibody assay (IFA). There was a significant (p < 0.001) decreasing trend in seroprevalence from summer to winter. Also, foxes trapped in areas outside human residential boundaries were more likely (p < 0.05) to be seropositive (16 of 23; 70%) than foxes trapped within the human residential boundaries (12 of 31; 39%). Twenty-eight of 90 (31%) dogs from the reservation were seropositive for antibodies against A. phagocytophilum by IFA. This seroprevalence was significantly lower (p < 0.05) in dogs compared to backcountry foxes. Six of 70 (9%) foxes were infected with A. phagocytophilum at the time of capture as determined by polymerase chain reaction amplification and sequencing of A. phagocytophilum DNA. I propose that gray foxes may serve as competent wildlife sentinels of A. phagocytophilum; I also recommend further studies to determine the abiotic or biotic factors contributing towards the differences in exposure observed between the seasons and areas.
Description:	Disease ecology thesis dealing with mesocarnivores and tick-borne pathogens Thesis (M.S)--Humboldt State University, Natural Resources, Wildlife, 2006
URI:	http://hdl.handle.net/2148/66
Date:	2006-07