EFFECT OF HETEROPHIL DEPLETION BY 5-FLUOROURACIL ON INFECTIOUS-BRONCHITIS VIRUS-INFECTION IN CHICKENS

An anti-tumour drug, 5-fluorouracil (5 FU) was used to deplete heterop hils in 11-day-old white leghorn chickens. The reduction in heterophil numbers was monitored by total and differential white cell counts in the peripheral blood. Three days after injection of 5 FU, when the het erophil numbers were significantly reduced, chickens were infected wit h the Massachusetts strain of infectious bronchitis virus (IBV). Follo wing infection, although the numbers of birds exhibiting clinical sign s (nasal exudate) were significantly higher in the 5 FU treated group, the consistency of the nasal exudate was characteristically thin and watery. No significant differences were seen in the virus titres in tr achea, lung and kidney between normal and heteropaenic chickens infect ed with IBV. However, the epithelial cell damage in the tracheal secti ons was less in the heterophil-depleted chickens.