Molecular detection and characterization of infectious laryngotracheitis virus in apparently healthy commercialand backyard chickens in Ibadan, Nigeria

Abstract

Infectious laryngotracheitis (ILT) is an acute respiratory disease of chickens which often results in severe losses in the commercial poultry industry as well as backyard chicken flocks. It is also a latent viral infection of chickens worldwide and the causative virus can be shed through poultry droppings. To check if apparently healthy Nigerian commercial and backyard chickens shed the ILT virus, Polymerase Chain Reaction (PCR) was used to test for the presence of the virus Infected Cell Protein 4 (ICP4) gene in cloacal swabs from 45 commercial and 40 backyard chickens in Ibadan. Nested-PCR was used to probe the samples further for presence of the ICP4 gene. Moreover, two positive nested-PCR products from the backyard chicken samples were sequenced to characterize the virus. One (2.2%) of the 45 samples from commercial chickens and four (10%) of the 40 samples from backyard chickens were positive for the virus with the first round PCR. Six (13%) out of the 45 samples from commercial chickens and 12 (30%) out of the 40 from backyard chickens were positive with nested-PCR. Sequence analysis of the two nested-PCR products from the backyard chicken samples revealed that the Nigerian ILTV sequences had nonsynonymous mutations W1130K and S1135T. This study revealed that commercial and backyard chickens in Ibadan shed the virus with the possibility of spread of infection to other birds. The mutations and phylogenetic clustering of the Nigerian ILTV ICP4 partial sequences revealed that they are different from vaccine and reference field sequences from other countries.