Evaluación del diagnóstico de Ehrlichia canis mediante frotis sanguíneo y técnica molecular en perros de Costa Rica
Fecha
2013-11-20
Autores
Romero Pérez, Luis Ernesto
Meneses Guevara, Ana
Jiménez Soto, Mauricio
Salazar Sánchez, Lizbeth
Dolz, Gaby
ROMERO-ZUÑIGA, JUAN JOSÉ
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Universidad Nacional, Costa Rica
Resumen
El objetivo de este trabajo fue comparar los resultados del diagnóstico de Ehrlichia
canis, mediante frotis sanguíneo y técnica de reacción en cadena de la polimerasa, (PCR,
Polymerase Chain Reaction, por sus siglas en inglés) en sangre de perros del Valle Central de
Costa Rica. Para este fin, se utilizaron 300 muestras sanguíneas de caninos sospechosos de sufrir
ehrliquiosis; estas muestras habían sido remitidas de diferentes clínicas veterinarias; también,
habían sido analizadas, previamente, mediante frotis sanguíneo, PCR anidado, y en algunos casos,
mediante técnica serológica. De cada muestra de sangre se obtuvo, además, información sobre:
localización geográfica de la clínica veterinaria, datos del perro al que pertenecía la muestra
sanguínea como: raza, edad, sexo y signos clínicos que presentó el perro.
Del total de 300 muestras analizadas, en 147 (49,0%) hubo resultados positivos a E. canis,
utilizando un PCR anidado; mientras que, en 178 (59,3%) fueron reportadas con inclusiones mediante la técnica de frotis sanguíneo. Solamente, en 103 (57,9%) de los casos positivos,
en frotis sanguíneo, fue posible el diagnóstico molecular de E. canis; mientras que de las 122
muestras reportadas negativas (sin inclusiones) un 36,0% (44) de los casos resultaron positivas
en la técnica de PCR. Para la prueba de frotis sanguíneo se determinó una sensibilidad del
70,1% y una especificidad del 51,0%, valor predictivo positivo de 57,9% y valor predictivo
negativo de 63,9%, comparado con la técnica de PCR. El análisis de regresión logística reveló
asociación positiva (p<0,05) con la presencia de inclusiones, pero no con la edad o el sexo
del animal; mientras que, la aplicación de la prueba t-student detectó diferencias altamente
significativas en los promedios de las variables de hematocrito y hemoglobina entre perros PCR
positivos y perros PCR negativos a E. canis. De las 30 muestras evaluadas, previamente, mediante
serología, un 25,0% de los casos seropositivos y un 36,4% de los casos seronegativos resultaron
positivos en el diagnóstico molecular de E. canis. El hallazgo de valores bajos de hematocrito
y hemoglobina, en combinación con signos clínicos y la detección de inclusiones en muestras
sanguíneas, representan un fuerte indicio de infección con ehrliquiosis; sin embargo, es necesaria
la aplicación de una técnica molecular como método diagnóstico confirmativo.
The objective of this study was to compare the results of the diagnosis of Ehrlichia canis in blood of dogs from the Central Valley of Costa Rica, using blood smears and the polymerase chain reaction (PCR). For this purpose, 300 blood samples of dogs suspected of suffering ehrlichiosis were used. Samples were obtained from different veterinary clinics and had been previously analyzed using blood smears, nested PCR, and, in some cases, the serological technique. In addition, the following information was obtained from each blood sample: geographical location of the veterinary clinic and data from the dog such as race, age, sex, and clinical signs. Of the total 300 samples analyzed, 147 (49.0%) were positive for E. canis, using a nested PCR, while 178 (59.3%) were reported with inclusions using blood smears. However, only 103 (57.9%) of the positive cases using blood smear resulted in the molecular diagnosis of E. canis; while of the 122 negative samples (no inclusions) 44 (36.0%) were positive using the PCR technique. Blood smear testing showed a sensitivity of 70.1% and a specificity of 51.0%; positive and negative predictive values were 57.9% of 63.9%, respectively, compared with the PCR technique. The logistic regression analysis showed a positive association (p<0.05) with the presence of inclusions, but not for age or sex, while highly significant differences were detected using the Student’s T-Test in the average hematocrit and hemoglobin variables between PCR positive and PCR negative dogs. Of the 30 samples previously evaluated by serological tests, 25.0% of seropositive cases and 36.4% of seronegative cases were positive in the molecular diagnosis of E. canis. Low levels of hematocrit and hemoglobin, together with clinical signs and inclusions detected in blood samples, represent a strong indication of ehrlichiosis infection. However, a molecular technique is required to confirm the diagnosis.
The objective of this study was to compare the results of the diagnosis of Ehrlichia canis in blood of dogs from the Central Valley of Costa Rica, using blood smears and the polymerase chain reaction (PCR). For this purpose, 300 blood samples of dogs suspected of suffering ehrlichiosis were used. Samples were obtained from different veterinary clinics and had been previously analyzed using blood smears, nested PCR, and, in some cases, the serological technique. In addition, the following information was obtained from each blood sample: geographical location of the veterinary clinic and data from the dog such as race, age, sex, and clinical signs. Of the total 300 samples analyzed, 147 (49.0%) were positive for E. canis, using a nested PCR, while 178 (59.3%) were reported with inclusions using blood smears. However, only 103 (57.9%) of the positive cases using blood smear resulted in the molecular diagnosis of E. canis; while of the 122 negative samples (no inclusions) 44 (36.0%) were positive using the PCR technique. Blood smear testing showed a sensitivity of 70.1% and a specificity of 51.0%; positive and negative predictive values were 57.9% of 63.9%, respectively, compared with the PCR technique. The logistic regression analysis showed a positive association (p<0.05) with the presence of inclusions, but not for age or sex, while highly significant differences were detected using the Student’s T-Test in the average hematocrit and hemoglobin variables between PCR positive and PCR negative dogs. Of the 30 samples previously evaluated by serological tests, 25.0% of seropositive cases and 36.4% of seronegative cases were positive in the molecular diagnosis of E. canis. Low levels of hematocrit and hemoglobin, together with clinical signs and inclusions detected in blood samples, represent a strong indication of ehrlichiosis infection. However, a molecular technique is required to confirm the diagnosis.
Descripción
Palabras clave
EHRLICHIA CANIS, PERRO, BACTERIAS, COSTA RICA, PRUEBAS DE LABORATORIO, ENFERMEDADES INFECCIOSAS, DOG, INFECTIOUS DISEASES, LABORATORY DIAGNOSIS