Transmission tree of the highly pathogenic avian influenza (H5N1) epidemic in Israel, 2015.

The transmission tree of the Israeli 2015 epidemic of highly pathogenic avian influenza (H5N1) was modelled by combining the spatio-temporal distribution of the outbreaks and the genetic distance between virus isolates. The most likely successions of transmission events were determined and transmission parameters were estimated. It was found that the median infectious pressure exerted at 1 km was 1.59 times (95% CI 1.04, 6.01) and 3.54 times (95% CI 1.09, 131.75) higher than that exerted at 2 and 5 km, respectively, and that three farms were responsible for all seven transmission events.

Detection of wild- and vaccine-type avian infectious laryngotracheitis virus in clinical samples and feather shafts of commercial chickens.

Infectious laryngotracheitis (ILT) is a respiratory disease of poultry caused by an alphaherpesvirus (ILTV). To evaluate differential detection of ILTVs belonging to the two types, wild-type or vaccine-type, both causing clinical signs, five PCRs were evaluated to detect wild-type and vaccine-type ILTV in clinical samples. By directly sampling the organs, we aimed to avoid changes in the virus genome and to facilitate a fast diagnosis. The samples were tracheal and spleen homogenates and feather shafts. The latter are easy to collect, nonlethal for the bird, and advantageous for monitoring purposes. We investigated the time interval for vaccine virus detection following commercial vaccination by the vent application, which is successfully practiced in Israel. The study indicated that ILTV amplification from feather shafts was possible in clinical cases for about a one-month period after vaccination. Vaccine strains were identified by nested PCR for the ILTV-gE gene and differed from wild-type ILTV strains by two criteria: (1) While avirulent vaccines could be detected for about a month after the vent application, wild-type virus could be detected, in conjunction with clinical signs, for an unlimited time period; and (2) The ILTV vaccine was present in the bird in minute quantities compared to the wild-type virus. We assessed the virus type that appeared in conjunction with the clinical signs and determined that the clinical signs appeared in conjunction with both molecular forms of ILTV. The vaccine virus-type and the wild-type ILTV differed by their distinct restriction pattern when using the HaeIII restriction enzyme digestion of the nested amplification product.

Integration of the reticuloendotheliosis virus envelope gene into the poultry fowlpox virus genome is not universal.

Fowlpox virus (FWPV) is found worldwide in poultry and wild birds. FWPV is a natural example of recombination between viruses, as reticuloendotheliosis virus (REV) fragments have been found in all poultry FWPVs and these are implicated in virulence alteration. We aimed to determine the commonality of this phenomenon and analysed FWPVs collected from 128 poultry flocks and birds over the last 10 years. Various fragments of both viruses were amplified and sequenced at the FWPV integration site, located between FWPV open reading frames 201 and 203. Seven isolates were found to contain no REV insertions, including fragments of the REV env, gag and 5' REV-long terminal repeat (LTR). We demonstrate here for the first time, the existence of poultry FWPVs without REV inserts (two from chickens, one from turkey FWPV and four from wild birds). The REV inserts were heterogeneous in size. In addition to poultry and wild bird isolates, three FWPV vaccine virus strains were examined and found to contain only remnant REV-LTR and no REV envelope gene fragments.