Abstract This study establishes the serological frequency against Neospora caninum on day zero and the presence of N. caninum DNA surveyed throughout the gestation of Bubalus bubalis females in a bovine buffalo system in the central zone of the state of Veracruz, Mexico. Blood samples were taken from 11 females in 6 different sampling periods and analyzed for N. caninum antibodies detection on day zero. DNA detection by PCR was performed on all sampling periods. The gestation months of the females were recorded for five trimesters by ultrasonography, as well as births and pregnancy losses. Recorded seropositivity and positivity for agent DNA were 90.9% (95% CI 58.7-9.7) and 36.3% (95% CI 10.9-69.2), respectively, on day zero. N. caninum DNA was detected between 18.1% (95% CI 2.3-51.7) and 45.4% (95% CI 16.7-76.6) over the five trimesters of observation, with three births and three abortions recorded. The studied water buffalo population had a high presence of N. caninum antibodies; however, the detection of N. caninum DNA remained below 47% in the females. The association was only observed in the detection of DNA with pregnant females (P 0.007). Our results support the hypothesis of the resistance of water buffaloes to infection and the onset of clinical signs against infection by N. caninum even upon a high possibility of infection and reinfection described in this production system in Mexico.

Abstract: Seropositivity to Neospora caninum was evaluated by Enzyme-Linked ImmunoSorbent Assay (ELISA) and the DNA was detected by PCR nested with external initiators Np 21-4 and internal Np 9-10 in cow leukocytes from the small-scale milk production system in Amecameca, State of México. A herd with 34 adult females was studied, performing follow-up with blood sampling for five months. Also, two brain samples from aborted fetuses were analyzed and the sequence of the amplicons in the Genbank was verified. Consistency between techniques was compared using the Kappa test. ELISA seroprevalence was 85.3 %; and DNA of the parasite was detected in 89.4 % of the cows. A brain sample was positive. The similarity of the amplicons ranged from 91 to 96 %, the Kappa Índex was 0.41. The use of leukocytes increases the likelihood of amplifying N. caninum DNA.

Resumen: Se evaluó la seropositividad a Neospora caninum mediante ensayo inmunoenzimático (ELISA) y se detectó el ADN por PCR anidada con iniciadores externos Np 21-4 e internos Np 9-10 en leucocitos de vacas del sistema de producción de leche en pequeña escala en Amecameca, Estado de México. Se estudió un hato con 34 hembras adultas realizando el seguimiento con muéstreos sanguíneos durante cinco meses; también, se analizaron dos muestras de encéfalo de fetos abortados y se constató la secuencia de los amplicones en el Genbank. La concordancia entre técnicas fue comparada mediante la prueba Kappa. La seroprevalencia por ELISA fue de 85.3 %; y se detectó ADN del parásito en 89.4 % de las vacas. Una muestra de encéfalo fue positiva. La similitud de los amplicones osciló entre 91 y 96 %, el índice Kappa fue de 0.41. El empleo de leucocitos aumenta la probabilidad de amplificar ADN de N. caninum.