Gastric gross and microscopic lesions caused by the UNAM-97 variant strain of infectious bronchitis virus after the eighth passage in specific pathogen-free chicken embryos.

Herein we report a description of gross and microscopic lesions found in specific pathogen-free chicken embryos caused by UNAM-97 infectious bronchitis virus (IBV) variant strain after the eighth passage. Embryos were divided into three groups and were inoculated in the chorioallantoic sac with 0.2 mL of UNAM-97, Mass 41 IBV (positive control), or sterile PBS (negative control). Forty-eight hours later the allatoic fluid was taken and used to start a cycle of eight passages through 9-d-old embryos. Seven days after the last passage, embryos were harvested and macroscopic lesions in all organs were recorded. Proventriculus and gizzard samples were obtained from all embryos and routinely processed for microscopic and ultrastructural examinations. The UNAM-97 IBV variant strain caused two macroscopic lesions uncommon for Mexican strains: thin-walled proventriculus and gizzard, as well as urate accumulation within an extra-embryonic peritoneal sac, leaving the body through the umbilical duct and accompanied by the yolk sac. At microscopic level, two relevant findings were observed to be produced by this variant. In the proventriculus, there was a decrease in the gland papillary branching, while the gizzard showed a significant reduction in mucosa thickness and tubular-to-proliferative-cell ratio, as well as an absence of hyaline secretion in the lumen. Electrodense material scattered in proventricular and gizzard cells was observed, with a structure consistent with that of coronaviruses. These pathological chicken embryo findings have not been reported as being caused by other IBV strains in Mexico.

Identification and quantification of granulocytes in caecal mucosa and submucosa of chickens experimentally infected with Eimeria tenella and Salmonella enteritidis.

1. Poultry granulocytes are not clearly distinguished from each other with haematoxylin-eosin (HE) stain; thus, histochemical techniques must be used. Three experiments were carried out using 4-week-old Leghorn chickens. 2. Three, 80-chicken groups were orally infected with (1) 10(8) colony forming units (CFUs) Salmonella enteritidis, or (2) 10(4) Eimeria tenella oocysts, or (3) 10(8) CFUs S. enteritidis + 10(4) E. tenella oocysts. Ten chickens from each group were euthanased and caecum samples obtained. Caecum samples were fixed in 10% formalin (buffered, pH 7.4) at 4, 8, 12 h, 1, 3, 5, 7, and 14 d post-inoculation (PI). 3. Samples were stained using three different staining techniques: HE for the identification of heterophils and eosinophils, Ziehl-Neelsen for mast cells, and p-phenilenediamine dihydrochloride plus pyrocatechol (PPD + PC) for eosinophils. 4. Birds from Experiment 1 showed no changes in the numbers of granulocytes. Birds from Experiments 2 and 3 showed higher numbers of heterophils in caecal mucosa and submucosa separately, on d 5 and 7. In Experiment 3, a decrease was observed in submucosal mast cells on d 3. Chickens from Experiments 2 and 3 showed increased numbers of mucosal mast cells between d 7 and 14. 5. PPD + PC positively stained eosinophils, but not heterophils. 6. Numbers of heterophils and mast cells were increased during the acute inflammatory process caused by E. tenella. Therefore, mast cells could play a role as primary inflammatory cells. Eosinophils seem not to be part of the inflammatory process caused by E. tenella.

Characterization of Mexican strains of avian infectious bronchitis isolated during 1997.

Ten infectious bronchitis virus (IBV) isolates were recovered from broiler chickens in the states of Queretaro and Guanajuato in Mexico. The viruses were isolated from trachea, lung, kidney, and cecal tonsils of birds that showed respiratory signs in spite of vaccination with Massachusetts (Mass) and Connecticut strains of IBV. Each isolate was identified by an accession number from 1 to 10. Six of the isolates were neutralized by Mass monoclonal antibodies, whereas the other four were not. In addition, these four isolates did not produce lesions in embryos in the first five to seven passes. These four isolates were further characterized by the reverse transcriptase-polymerase chain reaction and restriction fragment length polymorphism techniques. The electrophoretic patterns for the four isolates were identical but were different from other known IBV isolates.