Avian influenza vaccines are commonly used in the poultry industry. The objective of this study was to compare, under experimental conditions, the protective efficacy of four imported commercial ...inactivated H9N2 vaccines (A, B, C, and D) in broiler chickens. A total of 150 one-day-old chicks were divided into six groups: four experimental groups, each containing 30 chicks, received one of the vaccines (A, B, C, or D) delivered in a 0.3-ml dose subcutaneously at 1 day of age, whereas the control, Group T, was not vaccinated but challenged and Group E was kept unvaccinated and unchallenged. At 21 days postvaccination, Groups A, B, C, D, and T were challenged with 10
embryo infective dose 50% of A/Chicken/Morocco/01/2016 (H9N2). All chicks were observed daily for clinical signs during the 12 days postchallenge (dpc). At 5 and 12 dpc, chicks were euthanatized for necropsy examination. Blood samples were collected weekly for serologic analysis and oropharyngeal swabs were collected for virus detection by real-time RT-PCR. Respiratory signs started at 48 hr pc and maximum severity was observed on 9 dpc. Chiefly, the birds vaccinated with vaccine B showed significantly more respiratory signs than did their counterparts. Serologic analysis revealed that the sera of Groups A and D birds showed a decrease in antibody (Ab) levels up to day 26; then a slight increase of Ab level was observed until day 31, while Group B and C birds showed a stabilization of the titers from day 21 until the end of the experiment. The viral shedding rate was significantly lower in Groups C and A (40%-50% of the birds shed virus for <7 days) compared with other challenged groups (60%-75% of the birds shed virus for ≥9 days). This experiment illustrated that vaccination applied on the first day in the hatchery with the four vaccines tested did not provide an acceptable protection against H9N2 in comparison with the controls that did not receive any vaccine. However, at first glance, we might favor vaccines A and C for their ability to reduce and shorten viral shedding as compared with vaccines B and D.
Newcastle disease (ND) is still a major poultry disease worldwide. Vaccination remains the principal method of controlling ND in endemic countries. Various vaccination strategies, including the use ...of recently developed recombinant vaccines, have been used to control it. Recombinant vaccines that use the herpesvirus of turkey (HVT) as a vector to express one of the key antigens of Newcastle disease virus (NDV) have been developed to overcome some of the drawbacks related to the use of conventional vaccines. HVT as a vector appears to have unique beneficial characteristics: it is extremely safe, it is not affected by the presence of maternally derived antibodies, and therefore can be applied in the hatchery either in ovo or to day-old chicks. Due to its persistence in the bird, the HVT vector can be expected to induce life-long immune stimulation. In the present study, the efficacy of an HVT-based vector vaccine expressing the F gene of NDV (rHVT-F) was tested against a velogenic genotype IV NDV challenge in commercial turkeys with high levels of maternal antibodies (8.7 ± 0.8 log2 hemagglutination inhibition titer). The birds were vaccinated on the day of hatch by the subcutaneous route. Development of a humoral immune response to vaccination was detectable from 4 weeks of age by ELISA. The challenge strain used represents recent NDV genotype IV field strains from Morocco. Challenge with this strain induced ND-specific clinical signs and stunting without subsequent mortality in the non-vaccinated birds, whereas the vaccinated turkey poults showed protection as early as 3 weeks of age based on lack of clinical signs, better body weight gain, and reduction of challenge virus shedding. This is the first reported efficacy study of an HVT-vectored ND vaccine against a velogenic NDV challenge in commercial turkeys.
Avian influenza viruses of the H9N2 subtype continue to spread in wild birds and poultry worldwide. Infection with H9N2 avian influenza virus was detected for the first time in Morocco in January ...2016. In this study, a total of 105 organ and tracheal swab samples from 21 broiler farms in Morocco were collected from July 2016 to October 2018 for H9N2 screening. The suspicion of disease was based on severe respiratory signs such as sneezing, coughing, rales and gasping, while H9N2 virus infection was confirmed by real-time RT-PCR. Hemagglutinin (HA) genes of four isolates were amplified by conventional RT-PCR, sequenced, and aligned for phylogenetic analyses. Among the 21 flocks, 48% (10/21) were qRT-PCR positive for H9, with the cycle threshold values ranging from18.6 to 34.8. The maximum similarity in nucleotide and protein sequences (96-98%) was observed between the Moroccan viruses and an H9 virus isolated from broiler chickens in 2017 in Burkina Faso (A/chicken/BurkinaFaso/17RS93-19/2017) and from a layer chicken in the United Arab Emirates in 2015 (A/chicken/Dubai/D2506/2015). The HA genes revealed the close relationship between the four Moroccan viruses, with 97.9%-99.9% nucleotide identity. Phylogenetic analysis showed that the Moroccan viruses belonged to the G1 lineage, and likely originated from the Middle East, as previously reported in 2016.
The H9N2 virus continues to spread in wild birds and poultry worldwide. At the beginning of 2016, the H9N2 Avian influenza virus (AIV) was detected in Morocco for the first time; despite the ...implementation of vaccination strategies to control the disease, the virus has become endemic in poultry in the country. The present study was carried out to investigate the origins, zoonotic potential, as well as the impact of vaccination on the molecular evolution of Moroccan H9N2 viruses. Twenty-eight (28) H9N2 viruses collected from 2016 to 2021 in Moroccan poultry flocks were isolated and their whole genomes sequenced. Phylogenetic and evolutionary analyses showed that Moroccan H9N2 viruses belong to the G1-like lineage and are closely related to viruses isolated in Africa and the Middle East. A high similarity among all the 2016-2017 hemagglutinin sequences was observed, while the viruses identified in 2018-2019 and 2020-2021 were separated from their 2016-2017 ancestors by long branches. Mutations in the HA protein associated with antigenic drift and increased zoonotic potential were also found. The Bayesian phylogeographic analyses revealed the Middle East as being the region where the Moroccan H9N2 virus may have originated, before spreading to the other African countries. Our study is the first comprehensive analysis of the evolutionary history of the H9N2 viruses in the country, highlighting their zoonotic potential and pointing out the importance of implementing effective monitoring systems.
This study was carried out to evaluate the effect of different Low Pathogenic Avian Influenza (LPAI) H9N2 vaccines containing different virus strains (vaccine A, vaccine B, and vaccine C) on the ...productivity and immunity of 10 days-old broiler chickens. Two hundred day-old Cobb broiler chicks were divided into eight groups, 25 chicks in each group. Six groups were vaccinated with Vaccine A, Vaccine B, and Vaccine C (2 groups/each vaccine) at 10 day-old, respectively. Chickens of groups 7 and 8 were kept as control groups. One group from each vaccine was challenged at 28 days old with 106 EID50/0.2ml of A/chicken/Morocco/SF1/2016 (H9N2) virus via the oculonasal route. The remaining groups were kept unchallenged to evaluate the immune response. Chicks were sampled each week individually until 42 days old for zootechnical traits and serological evaluation. Two necropsies were done at 5 and 10 days post-challenge (DPC). Lungs and tracheas were collected for histopathology, and the virus shedding was monitored at 5, 7, 9, and 11 DPC by real-time RT-PCR. Results indicated that vaccine B provides significantly better growth performances (P < 0.05), final body weight gain (2689.6 g ± 73.2), and feed conversion ratio (2.10 ± 0.06) when compared to other vaccinated groups. During the challenge (28th -35th days), vaccine B showed a significant increase in antibody titer (26180 ± 1129.1) than other vaccines. In contrast, the vaccine C group had a similar immune response to that of the control group. Both vaccines A and B were able to stop virus shedding by 11 DPC with higher mean Cq values. However, the vaccine C group continued to shed the virus until 11 DPC. Pathological examination of challenged birds revealed lesions predominantly in the respiratory tract. At 5 DPC, fibrinous sinusitis, tracheitis with fibrin plug, pneumonia, and fibrinous airsacculitis were observed. By 10 DPC, the fibrinous inflammation inceased, and only congestion in the trachea, lungs, and sinuses with thickening of air sacs were observed. Histopathology revealed lymphoplasmacytic tracheitis and congestive pneumonia. Scoring of lesions generally revealed more severe lesions at 5 DPC. Statistical analysis of both macroscopic and microscopic scores showed no significant differences between groups in both necropsies. In conclusion, vaccine B has significantly better seroconversion, better growth performance parameters, and a relatively early stop of viral shedding compared to other vaccines.
Virusi ptičje gripe H9N2 nastavljaju se širiti u peradi i divljih ptica širom svijeta. Infekcija niskopatogenim virusom influence H9N2 prvi je put otkrivena u Maroku u siječnju 2016. godine. U ovom ...je istraživanju za probir na H9N2 prikupljeno ukupno 105 organa i obrisaka iz dušnika s 21 farme brojlera od srpnja 2016. do listopada 2018. iz različitih regija Maroka. Sumnja na bolest temeljila se na teškim respiracijskim znakovima kao što su kihanje, kašljanje, hropanje i hripanje, a infekcija virusom H9N2 potvrđena je PCR-om obrnute transkripcije u stvarnom vremenu. Sekvencije gena za hemaglutinin (HA) od četiri izolata amplificirane su pomoću RT-PCR qRT-PCR poravnane za filogenetsku i analizu sličnosti aminokiselina. Od 21 uzorka jata 48 % (10/21) bilo je pozitivno na H9 s pragom broja ciklusa u rasponu od 18,6 do 34,8. Maksimalna sličnost u nukleotidnim i proteinskim sekvencijama (96 -98 %) uočena je između marokanskih virusa i virusa H9 izoliranih iz brojlerskih pilića u 2017. u Burkini Faso (A/piletina/BurkinaFaso/17RS93-19) i od kokošjeg pileta u Ujedinjenim Arapskim Emiratima u 2015. (A/piletina/ Dubai/D2506/2015). HA geni otkrili su blisku vezu između četiriju virusa, s 97,9 % -99,9 % nukleotidnog identiteta. Filogenetska analiza pokazala je da marokanski virusi pripadaju lozi G1 i vjerojatno potječu s Bliskog istoka, kao što je objavljeno 2016. godine.
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