SPATIAL AND TEMPORAL PATTERNS OF BOVINE ANAPLASMOSIS AS REPORTED BY ILLINOIS VETERINARIANS

Spatial analysis was used in combination with more traditional epidemi ologic methods to study patterns of anaplasmosis in a transitional are a between anaplasmosis endemic and non-endemic regions, Data were coll ected using a mail survey from 179 veterinarians with practice areas i ncluding 100/102 Illinois counties. The pattern of anaplasmosis report ed by practitioners did not follow the general distribution of cattle and was clustered, with two major endemic foci. Endemic counties (22/1 00 counties) were bordered by areas of intermediate endemicity (36/100 counties) with only sporadic cases occurring in the remainder of the state (42/100 counties). Clinical disease occurred mainly in late summ er and early fall with a small number of new herds diagnosed during th e winter. Illinois practitioners most commonly identified horseflies a nd other biting flies as the vectors of anaplasmosis but also believed mosquitos, ticks and iatrogenic means could account for transmission in their practice areas. Flies were most often reported in summer whil e iatrogenic transmission was more commonly reported with winter outbr eaks. Vaccination and low level antibiotics were used in endemic areas but only by a small proportion of respondents (12%). Veterinarians in endemic and marginal areas also used antibiotics to clear infection f rom herds more often than did those experiencing sporadic cases in non -endemic areas. Many practitioners expressed uncertainty about the act ual extent of the problem in their areas. Wooded land area was used as a proxy to test for co-distribution of general vector habitat with an aplasmosis. Significantly more anaplasmosis was found in the more wood ed parts of the state (based on the Kappa statistic), Respondents from western Illinois reported carrier cattle to be the source of infectio n for most new outbreaks while white-tailed deer were considered to be as important a reservoir as cattle in southern Illinois. Spatial anal ysis did not support an important role for white-tailed deer.