Nilzane Beltrão

Natural infection of turkeys by infectious laryngotracheitis virus

The infectious laryngotracheitis virus (ILTV) is an important respiratory pathogen of chickens that also infects pheasants and peafowl. Epidemiologically non-related commercial turkey flocks with clinical signs such as tracheitis, swollen sinuses, conjunctivitis and expectoration of bloody mucus were examined for the presence of the virus. Laboratory ILTV detection was performed by virus isolation in embryonated eggs and cell cultures, PCR and sequencing of amplification products, histopathology, indirect immunofluorescence and electron microscopy. One ILTV turkey isolate was also experimentally inoculated into susceptible chickens and turkeys, reproducing a mild respiratory disease. This is the first description of natural infections with ILTV in turkeys.

Detecção de Ornithobacterium rhinotracheale (ORT) por meio da reação em cadeia da polimerase (PCR)

Ornithobacterium rhinotracheale (ORT) is a recently discovered Gram negative bacterium that has been associated with respiratory diseases in commercial poultry and wild birds from many countries. In Brazil, antibodies were detected in some broiler and breeder flocks from the States of Sao Paulo and Minas Gerais. Because the bacteria is difficult to grow, the Polymerase Chain Reaction (PCR) has been found to be suitable for identification and diagnostic purposes. The aim of the present work was to verify the occurrence of ORT in Rio Grande do Sul through the detection of the bacteria DNA. Tracheal swabs (84) were collected from 14 broiler flocks of distinct companies. DNA was purified and PCR performed with species specific primers from the ORT 16S ribosomal RNA gene. Amplification products with 784 base pairs were obtained from 10 out of the 84 samples. The positive samples were from four flocks of tree companies established in different regions of the state. The results indicate that this respiratory pathogen occurs in major broiler producing areas from the State of Rio Grande do Sul. Further studies are under way to determine the prevalence of this pathogen and to characterize the strains isolated.

Laryngotracheitis: reproducibility of the disease and comparison of diagnostic methods

Infectious laryngotracheitis virus (ILTV) cause mild to severe respiratory disease in chickens, the purpose of our study being to use Brazilian isolate of ILTV to reproduce ILTV disease in chickens by experimental infection and to compare three diagnostic methods (nested polymerase chain reaction (PCR), virus isolation, histopathology) for detection of ILTV. Forty-eight chickens intratracheally inoculated with ILTV and a further 48 with PBS, showing mild respiratory signs 48 hours post infection (PI) but no signs of infection after day 10 PI. Every 2 days PI, six birds were arbitrarily selected from the control and infected groups, sacrificed and the trachea collected. Both the nested PCR and virus isolation detected the virus from day 2 until day 12 PI. However, at day 12 PI, PCR detected ILTV DNA in 100% of the samples while the virus isolation method detected ILTV in only 33% of the samples. Tracheal histopathology showed intranuclear inclusion bodies on days 8 and 10 PI. The results indicate that the field-isolate of ILTV studied by us is of low pathogenicity and that our nested PCR protocol was able to detect positive samples over a longer infection period than many ILTV diagnostic test already described.

Detecção do vírus da laringotraqueíte das galinhas no Brasil

A study was carried out in search for evidences of infectious laryngotracheitis virus (ILTV) infections in some Brazilian chicken flocks. Tracheal tissues and swabs were collected from 10 different flocks of layers and broilers displaying respiratory signs of disease. Samples were processes for virus isolation in embryonated eggs and the membranes examined by histopathology. In addition, specimens were examined by polymerase chain reaction (PCR). Three flocks had ILTV positive chickens by virus isolation and PCR. These results confirm the occurrence of ILTV in chickens in Brazil.