Molecular Detection and Characterization of Infectious Laryngotracheitis Virus (ILTV) Genotype VII-IX in Backyard Chickens in Lusaka and Chongwe Districts, Zambia

Infectious Laryngotracheitis (ILT) is a respiratory disease of chickens caused by Infectious Laryngotracheitis Virus (ILTV) characterized by mild to severe respiratory disease, poor growth rates, and variable mortality. Although the disease has been suspected and several commercial vaccines are being used for its prevention in commercial enterprises, evidence of the presence of the virus has remained speculative. We set out to investigate the presence of the disease in backyard chickens. Throat and cloacal swabs were collected from 50 free-range unvaccinated backyard chickens purchased from local markets in Lusaka and Chongwe districts. Nucleic acid extraction was followed by PCR using ILTV ICP4 gene-specific primers. The ILTV gene was detected in a single apparently healthy chicken, representing 2% (1/50). Additional primers targeting the entire ICP4 gene including the flanking UTRs were designed. Sequence comparisons and phylogenetic analysis of the complete ICP4 coding region revealed the presence of ILTV genotype VII/IX CEO cluster. This work represents the first molecular detection and characterization of ILTV in non-vaccinated free-range backyard chickens in Zambia. In conclusion, this study confirms the presence of ILTV in Zambia. Determination of the ILT burden in chickens would facilitate informed decision-making regarding vaccination of chicken strategies and ILT disease prevention.