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Braz J Microbiol. 2016 Jan-Mar;47(1):231-42. doi: 10.1016/j.bjm.2015.07.001. Epub 2016 Jan 27.

Experimental infection with Brazilian Newcastle disease virus strain in pigeons and chickens.

Carrasco Ade O1Seki MC2Benevenute JL2Ikeda P2Pinto AA3.

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Abstract

This study was designed with the goal of adding as much information as possible about the role of pigeons (Columba livia) and chickens (Gallus gallus) in Newcastle disease virus epidemiology. These species were submitted to direct experimental infection with Newcastle disease virus to evaluate interspecies transmission and virus-host relationships. The results obtained in four experimental models were analyzed by hemagglutination inhibition and reverse transcriptase polymerase chain reaction for detection of virus shedding. These techniques revealed that both avian species, when previously immunized with a low pathogenic Newcastle disease virus strain (LaSota), developed high antibody titers that significantly reduced virus shedding after infection with a highly pathogenic Newcastle disease virus strain (São Joao do Meriti) and that, in chickens, prevent clinical signs. Infected pigeons shed the pathogenic strain, which was not detected in sentinel chickens or control birds. When the presence of Newcastle disease virus was analyzed in tissue samples by RT-PCR, in both species, the virus was most frequently found in the spleen. The vaccination regimen can prevent clinical disease in chickens and reduce viral shedding by chickens or pigeons. Biosecurity measures associated with vaccination programs are crucial to maintain a virulent Newcastle disease virus-free status in industrial poultry in Brazil.

KEYWORDS:

Columba livia; Experimental infection; Gallus gallus; RT-PCR; Serology

The susceptibility of pigeons (Columba livia) and other members of the Columbidae family to NDV has been reported by several authors.1112131415 It is now clear that the disease occurs in pigeons as a result of virus dissemination from affected chicken flocks, and it occurs in poultry flocks when the virus is disseminated from domesticated or feral pigeons.16 The source of ND infection to chicken flocks may be food contaminated with feces of feral pigeons infected with NDV.1617

Considering the potential risk of contamination of poultry species by pigeons carrying NDV, it is important to study the pathogenesis of the disease both in pigeons and in chickens. This study was designed to evaluate humoral immune response, viral shedding, and contact transmission after experimental infection of pigeons and chickens with a pathogenic NDV isolate of chicken origin under experimental and controlled conditions.

 However, the use of an exotic Newcastle disease virus strain that was responsible for the most recent outbreak in California (USA) in an experimental infection of adult pigeons yielded a morbidity rate of 20% and two pigeons were euthanized because they displayed severe clinical signs of ND

The different behavior of NDV strain when inoculated in different hosts was also observed in the present study, once 100% of the chickens died in a short period of time, whereas pigeons that were in contact with these chickens (or were experimentally infected) remained healthy, without any clinical signs compatible with ND.

Vaccination of a large number of chickens against ND is usually carried out using non-virulent live virus administrated by spray or in drinking water. These administration techniques usually produce considerable variation in individual antibody responses.6

Several differences have been observed in virus strains isolated from different species of birds, mainly free-living birds in different locations throughout the planet. It is very important to devise more accurate and precise methods to evaluate the virulence of NDV isolates, especially in hosts other than chicken, and further studies are needed to investigate the determinant factors of interspecies transmission.15 These strains circulate in bird populations, generally without causing the disease, in a parasite vs. host balance. When these free-living birds get in contact with commercial birds, outbreaks may occur, with considerable losses to countries that raise and export poultry and poultry products. Biosecurity measures associated with vaccination programs as postulated by the International Animal Health Code are crucial for the preservation of the virulent NDV-free status for industrial poultry in Brazil.19