ND, popularly known as Ranikhet disease, occurs every year in the form of an epidemic, causing 40-60% of the total mortality of the poultry population in Chowdhury, Bangladesh (1982b). Strains of the ND virus have been distinguished based on the clinical symptoms observed in the infected chickens. A thickening of the air sacs with catarrhal or case-like secretions is often observed Beard and Hanson, (1984).
The efficacy of each of the components of multivalent and combined vaccines must be demonstrated with the combined vaccine. In the case of Immunosera; Specific attention should be paid to providing supporting data for the efficacy of the regimen to be recommended. Unless otherwise justified, challenge is performed using a strain different from the one used in the manufacture of the vaccine.
The diagnosis of various disease conditions is made on the basis of history, age of birds, clinical signs, gross and microscopic lesions. Antibodies against NDV were found in each region ranging from 5 to 83% (mean 35%) of sampled chickens. In Mauritania, serum samples were collected from 80 chickens in village poultry flocks in each of three different regions Bell et al., (1990).
Thereafter, mean titers increased steadily as bird age increased, peaking in birds older than 3 years.
- Study area
- Study population
- Season
- Blood collection
- Egg collection
- Test principles
- Test procedure Equipments
- Preparation of 1% chicken red blood cell suspensions for use in Haemagglutination Inhibition (HI) test
- HI Test procedure
- Interpretation of the Test result
- Precautions
- Statistical analysis
A close inspection was then made regarding the condition of the eye, the presence or absence of debris material in the beak. The proventriculus, curds and liver, intestines were then inspected both internally and externally to detect any type of lesions. A total of 60 blood samples were collected from 3 commercial chicken farms; 20 samples from each of the farms.
The titer was determined twice for the poultry from each farm; one at the time of vaccination (in the early stages of ND infection) with the ND killed vaccine (Lasota) and another titer was taken after 7 days of vaccination. A total of 48 egg samples were collected from 3 commercial laying hen farms; 16 samples from each of the farms. In the syringe in which the blood is drowned, an anticoagulant such as EDTA (necessary amount) was taken.
The cells were then used to prepare a 1% cell suspension in isotonic PBS in the assay. Two-fold serial dilutions of 25 µl volumes of serum were made across the plate to the second to last well. 25 ul fluid was discarded from the second last well and the last well of the row was not diluted.
Clinical signs showed that the sick birds were lethargy, depression, reduced intake of food and water, crowding in the corner of the sheds, weight loss, brown pad, etc. Postmortem examination revealed pericarditis, petechial hemorrhage and fibrinous layer formation in the heart, air sac infection, enteritis, dilatation of the last part of the intestine. Post-mortem lesion includes hemorrhage in thigh and breast muscles, enlarged and necrotic bursa of Fabricius, yellow gelatinous membrane found over swollen bursa, hemorrhage in bursa.
The autopsy showed bleeding on the cecal tonsil, loss of tonicity of two cecums, clotted blood in the cecum, white foci in the intestinal mucosa, catarrhal enteritis. Autopsy showed catarrhal secretions in the nose and paranasal passages, trachea, bronchi, cloudy air sacs and congestion of the lungs. Difficulty breathing. Postmortem examinations were white caseous nodules in the lungs or air sac of affected birds.
The post mortem examinations were pin point bleeding in tip of gland of proventricular, hemorrhagic tracheitis which was also present.
Mortality rate before and after challenge vaccination
This may be due to vaccination, when the anti-ND titer level has increased to a protective level that prevents infection.
Results of HI titre level due to challenge vaccination
But after 7 days of vaccination, the range of titer levels increased to 7.5 to 8.0 (Table: 4.5), which was the most protective level for ND infection. In laying farms, before challenge vaccination, the range of HI to ND titer was 4.5 to 5.5 (Table: 4.4), which was susceptible to ND infection. As a result of the challenge vaccination, the HI vs. ND titer level increases from a non-protective level to a protective level in broiler flocks (Graph: 4.1) and in layer flocks (Graph: 4.2) when the titer was determined 7 days after infection.
Table: 4.3: Results of HI titer of atypical fowl disease in broilers (infected flock; before challenge vaccination). Table: 4.4: Results of HI titer of atypical fowl disease in layers (infected flock; before provocation vaccination). The prevalence of atypical fowl disease was moderately high in January and February 2012.
This can immediately increase the protective titer level of the herd against ND when the herd has been previously vaccinated with any shortage of ND vaccine. But there is no detailed information about this type of challenge vaccination against ND in poultry. Detection of maternal antibodies to Newcastle disease virus in chicks using an indirect immunoperoxidase assay.
Identification and grouping of Newcastle disease virus strains by restriction site analysis of a region from the F gene. Serological survey of Newcastle and Gumboro disease, pasteurellosis and pullorum disease in chickens of local breeds in Niger. Prevalence of Newcastle disease virus antibodies in local and exotic chicken under different management systems in Nigeria.
III Simultaneous measurements of antibodies to infectious bronchitis virus, infectious bursal disease and Newcastle disease virus in a single serum dilution.
APPENDIX
CHAPTER-VII
