Chicken anemia virus (CAV) is a small, non-enveloped, single-stranded DNA virus, first isolated by Yuasa et al. (1979), a Gyrovirus, within the family Circoviridae 1. The virus causes aplastic anaemia, generalized lymphoid atrophy and increased mortality after infection of day-old susceptible chickens 2. The virus causes severe depletion of cortical thymocytes and erythroblastoid cells in the bone marrow, leading to immunodeficiency and anemia 3, because the VAIA lacks the necessary enzymes to reproduce its DNA in an independent way, it requires the cells to be divided very quickly 4. The Positive Pixel Count is a multipurpose algorithm that measures area and intensity of staining for two-colored slides. This technique is useful as support to improve the histopathology evaluation making it objective by means of quantitative analytical techniques and this way, to improve the quality and efficiency of the pathology services. The purpose of this study was to apply quantitative analytical technique to histopathology of birds infected experimentally by the virus of chicken anemia virus.

Histopathology showed bone marrow with abundant cells of the erythrocytic and granulocytic series from chickens healthy controls (Figure 1) and severe bone marrow hypoplasia and/or complete aplasia, fully depletion of the erythrocytic and granulocytic series, both accompanied by space occupying adipocytic replacement (Figure 2) in the birds of 10, 14, 17 and 21 days after inoculation. A quantitative analytical technique by Positive Pixel Count Algorithm was applied. The data are shown below in Table 1.

The results demonstrated that the number of Strong Positive and Positivity (%) of control slides were higher than CAV slides (Average: 61% vs. 25%, respectively). The control slides showed strong positivity, due to the presence of bigger quantity of erythroblastoid cells. The CAV slides of 7 days PI had high positivity (average: 94%), because the CAV produces the lesions but severe starting from the 10 days PI up 21 days PI, after the cellular regeneration is observed, being able to be evidenced by means of focuses of erythroblastoid cells hyperplasia.

This technique demonstrated in a quantitative way the severe decrease of the cellular components of the bone marrow in presence of the infection for CAV, supporting with numeric data the histology image evaluated by the pathologist. Therefore, it can be used as support to the histopathology of field samples to evaluate the presence of lesions taken place by CAV in the farms and this way to improve the quality and efficiency of the veterinary pathology services.