USE OF A NONRADIOACTIVE DNA-PROBE FOR DETECTION OF ANAPLASMA-MARGINALE INFECTION IN-FIELD CATTLE - COMPARISON WITH COMPLEMENT-FIXATION SEROLOGY AND MICROSCOPIC EXAMINATION
Nl. Ge et al., USE OF A NONRADIOACTIVE DNA-PROBE FOR DETECTION OF ANAPLASMA-MARGINALE INFECTION IN-FIELD CATTLE - COMPARISON WITH COMPLEMENT-FIXATION SEROLOGY AND MICROSCOPIC EXAMINATION, Journal of veterinary diagnostic investigation, 9(1), 1997, pp. 39-43
A sensitive Anaplasma marginale-specific 409-base pair DNA probe was d
eveloped in a previous study for detection of A. marginale infection i
n experimentally infected cattle with a test that employed slot-blot a
nd in situ hybridization. To test the suitability of the probe to dete
ct A. marginale in the blood of naturally infected carrier cattle, slo
t-blot hybridization was used to determine the infection rate of A. ma
rginale in cattle from 3 geographic areas in Oklahoma. For comparison,
blood samples from the same cattle were also examined by light micros
copy and were tested by the complement fixation test. For the DNA hybr
idization assay, the probe was labeled with digoxigenin 11-dUTP by pol
ymerase chain reaction (PCR). DNA was extracted from blood using the Q
IAamp blood kit and then applied to a nylon membrane and hybridized wi
th the probe. The study herds consisted of 31 beef cows in Harper Coun
ty, OK, and 42 and 70 dairy cows from Payne and Pittsburg counties, OK
, respectively, In the 3 herds, 80.6%, 92.8%, and 57.1% of the cows we
re positive for A. marginale as assessed with the DNA hybridization as
say. In contrast, only 25.8% and 2.86% were complement fixation positi
ve in 2 herds, and no complement fixation positives were found in 1 he
rd. Uncountable parasitemia that was too low to accurately determine (
<0.01%) from 29.0%, 4.8%, and 11.4% of the samples, respectively, was
demonstrated by microscopic examination. All samples positive by compl
ement fixation and microscopic examination had positive probe reaction
s in the DNA hybridization assay. Therefore, the PCR-mediated nonradio
active DNA probe described here may be useful in epidemiologic investi
gations and in identification of carrier cattle. This assay could be a
dapted for use in diagnostic laboratories because it is sensitive, spe
cific, nontoxic, quickly executed, and inexpensive.