Objective—To determine the reference interval for WBC counts in Holstein dairy cows from herds with high seroprevalence for anti–bovine leukemia virus (BLV) antibodies, analyze the correlation of total WBC counts and blood proviral load (bPVL) in BLV-infected animals, and determine whether total WBC count can be used a hematologic marker for in vivo infection. Animals—307 lactating cows from 16 dairy herds with high BLV seroprevalence. Procedures—Blood samples were collected for assessment of plasma anti–BLV p24 antibody concentration (all cows), manual determination of WBC count (161 BLV-seronegative cows from 15 herds), and evaluation of bPVL (146 cows from another herd). Results—The WBC count reference interval (ie, mean ± 2 SD) for BLV-seronegative dairy cows was 2,153 to 11,493 cells/μL. Of the 146 cows used to analyze the correlation between WBC count and bPVL, 107 (73%) had WBC counts within the reference interval; of those cows, only 21 (19.6%) had high bPVL. Most cows with high WBC counts (35/39) had high bPVL. Mean WBC count for cows with high bPVL was significantly higher than values for cows with low or undetectable bPVL. White blood cell counts and bPVL were significantly (ρ = 0.71) correlated. Conclusions and Clinical Relevance—These data have provided an updated reference interval for WBC counts in Holstein cows from herds with high BLV seroprevalence. In dairy cattle under natural conditions, WBC count was correlated with bPVL; thus, WBC count determination could be a potential tool for monitoring BLV infection levels in attempts to control transmission. | Instituto de Virología | Fil: Alvarez, Irene. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Virología; Argentina | Fil: Gutierrez, Gerónimo. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Virología; Argentina | Fil: Gammella, Mariela. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Virología; Argentina | Fil: Martinez, Cecilia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Virología; Argentina | Fil: Politzki, Romina Paula. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Virología; Argentina | Fil: Gonzalez, Cintia. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Virología; Argentina | Fil: Caviglia, Luciana. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Virología; Argentina | Fil: Carignano, Hugo Adrian. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética "Ewald A. Favret"; Argentina | Fil: Fondevila, Norberto. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Virología; Argentina | Fil: Poli, Mario Andres. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Genética "Ewald A. Favret"; Argentina | Fil: Trono, Karina Gabriela. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Virología; Argentina

Test vaccines comprised of inactivated water-in-oil emulsions containing various antigen levels were prepared using a non-pathogenic H5N1 avian influenza (AI) virus, A/duck/Hokkaido/Vac-1/04 (H5N1). The potencies of these test vaccines were evaluated by two experiments. In the first experiment, the triangular relationship among the antigen levels of test vaccines, the hemagglutination inhibition (HI) antibody response, and the protective effect against challenge with a highly pathogenic avian influenza (HPAI) virus, A/chicken/Yamaguchi/7/04 (H5N1), was confirmed. Then lasting immunity of chickens after a single-shot vaccination was confirmed in the second experiment. As a result, complete protection after the challenge was observed in chickens immunized by test vaccines with an antigen level of 160 HA units/dose or higher. Thus, it was ascertained that the minimum antigen level in the AI vaccine was 160 HA units/dose, and the minimum HI antibody titer that could protect chickens from HPAI virus infection-related death was considered to be 1:16. Dose-dependent HI antibody responses were observed in chickens after the vaccination. Thus, 640 HA units/dose were thought to be similar to the optimal antigen level. Alternatively, the HI antibody titers of chickens, injected with the vaccine containing 640 HA units/dose, were maintained at 1:181 or higher for 100 weeks after the single-shot vaccination.

In this study ELISA was standardized for detecting antibodies against Hydropericardium Syndrome Virus. Factors like Antigen, Conjugate and incubation time were studied. Standardization was carried out by checker board titration method. Optimum incubation time for colour development was found to be 15 minutes while 50 mug/ml of antigen gave better results than 100 mug/ml. The conjugate dilution of 1:500 was observed to give satisfactory results as determined by regression analysis. Cut off value was determined by adding 2SDs and 3SDs in the mean optical density (OD) values of negative serum samples. It was found that mean OD+2SD (0.0684) resulted in better diagnostic sensitivity) and diagnostic specificity than mean OD+3SDs (0.0741).

The quick diagnosis of Newcastle disease requires known serum against the disease. In this study, an attempt was made to raise anti- Newcastle disease virus hyperimmune serum in rabbits. Three different inoculum were prepared to inoculate in the rabbits; (i) Fresh harvested allantoic fluid containing Newcastle disease virus (NDV) Mukteswar vaccine strain; (ii) Freshly harvested ND virus pelletted through centrifuging at 40,000 rpm for two hours and resuspended in normal saline and (iii) Pelletted virus (centrifuged and suspended as in ii) with addition of incomplete Freund's adjuvant. It was observed during the monitoring of haemagglutination inhibition (HI) titre that the serum collected after series of inoculation of 1st and 2nd inoculum provided maximum titre upto 1:256. However, the serum collected after series of injection of 3rd inoculum gave maximum HI titre 1:1024. This study suggested that antigen containing incomplete Freund's adjuvant provided better immune response against Newcastle disease virus in rabbits.