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Combined Usage of Rhvt-h5 and Re-6 Vaccines Towards an Effective Avian Influenza Vaccination Program for Commercial Layer Chickens

Md Zulfekar Ali*
Animal Health Research Division, Bangladesh Livestock Research Institute, Savar, Dhaka 1341, Bangladesh

Abstract/ Executive Summary:

Vaccination against highly pathogenic avian influenza virus (HPAIV) of subtype H5N1 is one of the possible means to protect chickens against its outbreak in endemic countries. Early vaccination of layer birds with recombinant vector vaccine based on turkey herpesvirus expressing H5 gene (rHVT-H5) provides longer protection while inactivated vaccine Re-6 needs multiple booster doses to achieve continuous antibody titer. Therefore, this study was carried out to offer a vaccination program using live rHVT-H5 and inactivated Re-6 vaccines in field condition. For this trial, five ISA brown commercial layer chicken farms were raised with 500 birds per farm. Two licensed vaccines- rHVT-H5 and Re-6 in Bangladesh were used for this trial where birds in farms 1 and 2 were administered only rHVT-H5 vaccine at one-day-old, and farms 3 and 4 rHVT-H5 vaccine at one-day-old then boosted with Re-6 vaccine at 25 weeks of age. Farm 5 was not vaccinated and functioned as control. Blood samples were randomly collected from 20 birds in each farm at 3-week interval from 2 weeks old till 65 weeks and harvested serum analyzed by haemagglutination inhibition (HI) test for antibodies against HPAIV H5N1. The titer of haemagglutination inhibiting antibodies against AIV H5N1 on farms 3 and 4 was considerably high and remained up to 65 weeks. However, in farm 1 and 2 there was decline in antibody titer after 56 weeks of age. This study demonstrated that the combined use of rHVT-H5 vaccine at one-day-old and Re-6 at 25 weeks of age enhanced a longer lasting protective antibody against circulating HPAIV H5N1 in commercial layer chickens in Bangladesh.

Keywords: Vaccine, Serology, Avian influenza, Poultry.

Location: Animal Health Research Division, Bangladesh Livestock Research Institute, Savar, Dhaka 1341, Bangladesh

Start Date:

End Date:

Program Area: Animal Health and Management

Commodity: Vaccine, Broiler chick

Objectives:

This study was carried out to suggest an effective vaccination routine in poultry against HPAIV H5N1 by using live rHVT-H5 and inactivated Re-6 vaccines for commercial layer chickens in Bangladesh.

Methodology:

Experiment design. Five ISA brown layer chicken farms with 500 birds per farm were selected in collaboration with poultry farmers and raised for this research. The management practices like feeding, housing, daylight, biosecurity, floor space were same for all farms and located in the same geographic area. The birds were reared from one-day-old to 65 weeks of age. Two vaccines against avian influenza subtype H5N1 that were approved by the Government of Bangladesh namely, rHVT-H5 (Cevac) and Re-6 (Merial) were selected for this trial. The farmsteads were divided into five groups as Farm 1, 2, 3, 4, and 5. Only rHVT-H5 vaccine was given to Farms 1 and 2 at one-day-old chickens. In Farms 3 and 4, rHVT-H5 vaccine was used at oneday-old and then Re-6 vaccine used at 25 weeks old chickens. Farm 5 was non-vaccinated (control) and data were used to compare with vaccinated group. Doses and routes of vaccines were 0.5ml subcutaneously for rHVT-H5 and 0.5ml intramuscularly for Re-6 vaccines.

Sample collection and preparation. Twenty blood samples were collected randomly from each farm at 3 weeks interval from 2 to 65 weeks old (22 times). About 1 ml of blood was collected from each bird using sterile needle and syringe from either the jugular vein (one-day-old birds) or wing vein (older birds). Sera were obtained from the clotted blood and stored at -20 °C until required for haemagglutination inhibition test.

Haemagglutination inhibition (HI) test. The haemagglutination inhibition (HI) test was implemented on all serum samples using 4 HA haemagglutination units of the antigen according to the OIE guideline. Inactivated HPAIV H5N1 antigen and positive control antisera were used for HI test. Geometric mean titer (GMT) was calculated using Microsoft Excel spreadsheet (Microsoft Corporation, USA).

Source of Information: Stamford Journal of Microbiology, 2020. Vol. 10, Issue 1, p. 9-11 ISSN: 2074-5346 (Print); 2408-8846 (Online)

Article Link (Online Journal): DOI: https://doi.org/10.3329/sjm.v10i1.50725

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The use of rHVT-H5 at first day of age and followed by boosting vaccination after 25 weeks of age by inactivated Re-6 vaccine which gave better protection compared to vaccinated by rHVT-H5 or Re-6 vaccination alone in commercial layer chickens.

Knowledge Management: Journal