Detection of infectious laryngotracheitis virus from darkling beetles and their immature stage (lesser mealworms) by quantitative polymerase chain reaction and virus isolation

Abstract

Infectious laryngotracheitis virus (ILTV) causes a respiratory disease of chickens that is important worldwide. Control of ILTV requires biosecurity management and vaccination. However, some live vaccines are not always efficacious and continual infection of susceptible chickens (back passage) can occur, causing the vaccine virus to increase in virulence. In previous studies using PCR and restriction fragment length polymorphism to check the genomic types of field strains, some outbreaks were derived from chicken-embryo-origin vaccines. Improved biosecurity and management practices may reduce the incidence of ILTV. The lesser mealworm and its adult stage, the darkling beetle, are cosmopolitan insects and are prevalent in poultry facilities. They consume feed, water, poultry carcasses, and feces. They are nocturnal, live in compacted earth and litter, and can damage poultry house structures. They are almost impossible to eliminate, require pest control expenses, and harbor pathogens, and birds may consume beetles rather than feed, resulting in poor feed conversion. This study showed that a field ILTV isolate of vaccine origin could survive on the external surfaces and internal organs of adult beetles and their larvae and could be reisolated in chicken embryos. Additionally, the ILTV from beetles and their larvae were subjected to PCR-restriction fragment length polymorphism tests to classify their genomic types. Beetles may be a vector by which ILTV is spread on chicken farms. Therefore, beetle control should be an important part of decontamination of ILTV in chicken houses.