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Pathological imapact of Italy 02 IB virus studied

Spanish investigators have provided more information about the pathological consequences of the Italy 02 serotype of infectious bronchitis virus.

Even though it is a predominant infectious br serotype in several European countries, little is known the pathogenesis of Italy 02 serotype, they say.

In their study, they infected chicks as well as old hens with the Italy 02 serotype and then evaluated clinical signs and gross and microscopic findings. They also utilized in situ hybridization (ISH) and real-time polymerase chain reaction (RT-PCR).

The Italy 02 serotype was shown to cause severe respiratory and renal damage in 1-day-old chicks but not in adult hens, which had only respiratory disease and a drop in egg production. The use of ISH demonstrated the presence of viral RNA in nasal turbinates prior to the trachea, but replication periods were more consistent and longer in lower gastrointestinal tract enterocytes.

In addition, the detection of viral nucleic acid in the gut by RT-PCR was consistent, and there was more persistent viral shedding detected in feces than in nasal exudates, Roser Dolz and colleagues, of the Centre de Recerca en Sanitat Animal, wrote in a recent issue of Veterinary Microbiology.

CEO vaccines for ILT given in water replicate differently

Two chicken-embryo-origin vaccine strains for infectious laryngotracheitis replicated differently in drinking water, Australian investigators say.

It is notable, they say, that recent infectious laryngotracheitis (ILT) outbreaks affecting intensive poultry production have been caused by vaccine-related virus strains. Consequently, they sought to characterize and compare the viral replication and transmission patterns of two attenuated chicken-embryoorigin ILT vaccines delivered in drinking water.

They inoculated two groups of specific-pathogen-free chickens with SA-2 ILT or Serva ILT vaccine strains. Unvaccinated birds were then placed in contact with vaccinated birds at regular intervals.

In addition, investigators collected tracheal swabs every 4 days over a period of 60 days and then evaluated the presence and amount of virus using quantitative polymerase chain reaction.

A rapid increase in viral-genome copy numbers was observed shortly after inoculation with SA-2 ILT virus.

In contrast, a comparatively delayed virus replication was observed after vaccination with the Serva ILT virus.

Transmission to in-contact birds occurred soon after exposure to Serva ILT virus but only several days after exposure to the SA-2 ILT virus, according to a report in Avian Pathology by Mauricio Coppo, DVM, PhD, MVSc, and colleagues of the University of Melbourne.

‘Poor flock immunity’ blamed for ND outbreaks

Inadequate vaccination may be to blame for Newcastle disease outbreaks in the Netherlands, Dutch investigators say.

In their article, they presented the complete genome sequence of a highly virulent genotype VII virus (NL/93) obtained from vaccinated poultry during a 1992-1993 outbreak of Newcastle disease (ND) in the Netherlands.

When challenged with the NL/93 strain, chickens vaccinated with a classic vaccine were completely protected against clinical disease; in addition, mortality and virus shedding were significantly reduced, even with a supposedly suboptimal vaccine dose. In contrast, a live vaccine antigenically adapted to match the genotype VII NL/93 outbreak strain did not provide increased protection.

It has been argued that ND outbreaks may be due to antigenic divergence between the vaccine strains and circulating field strains. However, “These results suggest that it is not antigenic variation but rather poor flock immunity due to inadequate vaccination,” report J.C. Dortmans and colleagues, of the Central Veterinary Institute of Wageningen UR, the Netherlands, in Veterinary Microbiology.

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