Genotype classification and pathogenicity of infectious bursal disease virus circulating in vaccinated broiler chicken farms.

This study investigated the genotype classification and pathogenicity of infectious bursal disease virus (IBDV) circulating in vaccinated broiler chicken farms in Egypt. A total of 150 samples were collected from 30 vaccinated commercial broiler chicken farms and pooled into 30 working samples. IBDV was tested using reverse transcriptase polymerase chain reaction (RT-PCR) amplification of the hypervariable region of the viral protein 2 (hvVP2) and the VP1 gene 5' extremity. Both RT-PCR fragments were sequenced from six samples, and then the obtained nucleotide sequences were analyzed. The IBDV genotypes were identified using nucleotide sequences. Five sequences of the six strains examined were classified as genotype A3B2 for the highly virulent segments A and B (vv-A/vv-B IBDV). Interestingly, this study identified and classified a novel segment-reassortant strain as the A1B2 genotype. Specifically, it involved the segment reassortment of classical virulent segment A (cv-A) with vv-B producing cv-A/vv-B reassortant IBDV. Subsequently, we compared the pathogenicity of reassortant (cv-A/vv-B) IBDV and vvIBDV strains identified in this study. Both strains developed typical IBD clinical signs, postmortem lesions, histopathology, immunohistochemistry, and lesion scores, which were more severe in vvIBDV than reassortant IBDV. In conclusion, this is the first report of the genotype classification based on both genome segments (hvVP2 and VP1) with pathogenicity of IBDV circulating in vaccinated broiler chicken farms and this pathogenicity is more severe in vvIBDV strain than a novel reassortant IBDV strain.

Effect of omega-3 rich diet on the response of Japanese quails (Coturnix coturnix japonica) infected with Newcastle disease virus or avian influenza virus H9N2.

This study was performed to evaluate the effects of omega-3 supplementation on growth performance, clinical signs, post-mortem lesions, haemagglutination inhibition (HI) antibody titres, gene expression and histopathology in quails (Coturnix coturnix japonica) infected with Newcastle disease virus (NDV) and avian influenza virus (AIV) H9N2. One hundred, 40-day-old male quails were divided into 5 groups: G1, fed a control basal diet; G2A, infected with NDV; G2B, infected with H9N2; G3A, infected with NDV and given omega-3, and G3B, infected with H9N2 and given omega-3. The dietary omega-3 supplementation was continued for 4 weeks: two weeks before infection and two weeks after intranasal infection with virulent NDV and AIV H9N2. Our results revealed significant differences (P < 0.05) in growth performance, HI antibody titres, clinical signs, post-mortem lesions, mortality, viral shedding rates, immunological parameters, and histopathological lesions between the treated (G3A and G3B) and untreated (G2A and G2B) groups. In conclusion, dietary omega-3 supplementation for 4 weeks can improve growth performance and alleviate the deleterious immunological and pathological effects of NDV and AIV H9N2 infection in quails.

Effect of colibacillosis on the immune response to a rabbit viral haemorrhagic disease vaccine.

Viral haemorrhagic disease (VHD) and colibacillosis are common diseases in rabbits that cause economic losses worldwide. The effect of colibacillosis on the immune response of vaccinated rabbits against rabbit haemorrhagic disease virus (RHDV) was studied. Four groups (G1-G4) were included. G1 was the negative control group; G2 was the RHDV vaccine group; G3 was the E. coli-infected group; and G4 was the E. coli-infected + RHDV vaccine group. The E. coli infection and RHDV vaccination were simultaneously performed, with another previous infection, 3 days before vaccination. At 28 days post-vaccination (PV), the rabbits (G2-G4) were challenged intramuscularly with 0.5 ml of RHDV at a dose of 103 50% median lethal dose (LD50)/rabbit. The rabbits were observed for clinical signs, body weight gain and mortality rates. Tissue, blood, serum, and faecal samples and rectal swabs were collected at 3, 5, 7, 14, 21 and 28 days PV. Significant clinical signs and mortality and a decrease in BW were observed in the infected + RHDV vaccine group. On the 3rd day post-infection (PI), compared with all the other groups, the vaccinated group (G2) had significantly upregulated hepatic tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) levels; however, the infected + RHDV vaccine group had significantly higher intestinal levels of TNF-α and IL-6 than the other groups. Furthermore, E. coli infection in vaccinated rabbits led to immunosuppression, as shown by significant decreases (P < 0.05) in heterophil phagocytic activity, the CD4+/CD8+ ratio, and HI antibody responses to RHDV and a significant increase in the heterophil to lymphocyte (H/L) ratio. In conclusion, colibacillosis leads to immunosuppression involving a shift in the equilibrium of cytokines and reduced weight gain and mortality in vaccinated rabbits and could be a contributing factor in RHDV vaccination failure in rabbit farming.

Isolation of a Novel Reassortant Highly Pathogenic Avian Influenza (H5N2) Virus in Egypt.

Highly pathogenic avian influenza (HPAI) H5N1 and H5N8 have become endemic among domestic poultry in Egypt since 2006 and 2016, respectively. In parallel, the low pathogenic avian influenza H9N2 virus has been endemic since 2010. Despite the continuous circulation of these subtypes for several years, no natural reassortant has been detected so far among the domestic poultry population in Egypt. In this study, the HPAI (H5N2) virus was isolated from a commercial duck farm, giving evidence of the emergence of the first natural reassortment event in domestic poultry in Egypt. The virus was derived as a result of genetic reassortment between avian influenza viruses of H5N8 and H9N2 subtypes circulating in Egypt. The exchange of the neuraminidase segment and high number of acquired mutations might be associated with an alteration in the biological propensities of this virus.

Enhanced infection of avian influenza virus H9N2 with infectious laryngeotracheitis vaccination in chickens.

Avian influenza and infectious laryngeotracheitis viruses are common causes of respiratory diseases in chickens with economical importance worldwide. In this study, we investigated the effect of experimental co-infection of avian influenza virus-H9N2 (AIV-H9N2) with infectious laryngeotracheitis virus (ILTV) live-attenuated vaccine (LAR-VAC®) on chickens. Four experimental groups were included in this study: negative control group, AIV-H9N2 group, AIV-H9N2+LAR-VAC® group, and LAR-VAC® group. AIV-H9N2 was inoculated intranasally to challenged groups at 35 days of age. On the same day, LAR-VAC® was ocularly administered to vaccinated groups. Chickens were observed for clinical signs, changes in body weight and mortality rates. Tissue samples, sera, tracheal and cloacal swabs, and blood were also collected at 3, 6, 9 and 12 days post-infection (PI). A significant increase in clinical signs and mortality rates were observed in the AIV-H9N2 + LAR-VAC® group. Moreover, chickens coinfected with AIV-H9N2 and LAR-VAC® showed a significant decrease in body weight and lymphoid organs indices. The tracheal gross and histopathological lesions and the shedding titer and period of AIV-H9N2 were significantly higher in AIV-H9N2 + LAR-VAC® group when compared to other groups. Furthermore, AIV-H9N2 infection leads to humoral and cellular immunosuppression as shown by a significant decrease in the CD4+/CD8+ ratio and antibody responses to ILTV and a significant increase in H/L ratio. In conclusion, this is the first report of co-infection of AIV-H9N2 and ILTV vaccine in chickens, which leads to increased pathogenicity, pathological lesions, and AIV-H9N2 shedding titer and period, which can lead to severe economic losses due to poor weight gain and mortality.