A.T. Venugopalan

Characterization of Newcastle Disease Viruses Isolated from Chickens and Ducks in Tamilnadu, India

During 1993, outbreaks of Newcastle disease occurred on many farms in Tamilnadu, India. Six Newcastle disease virus (NDV) isolates were obtained from the chickens on five different farms and from the birds on one duck farm during outbreaks of the disease. All the isolates were characterized as velogenic, based on the mean death time, intravenous pathogenicity index, intracerebral pathogenicity index (ICPI), stability of haemagglutinin at 56°C, agglutination of equine erythrocytes, haemagglutination elution pattern and adsorption of haemagglutinin by chick brain cells. The isolate obtained from ducks resembled a group D strain, based on its ICPI and its reaction with a panel of monoclonal antibodies. The other five NDV isolates obtained from chickens were placed in groups B(1), C1(2) and D(2) on the basis of their binding patterns with the panel of monoclonal antibodies. In challenge experiments, it was found that LaSota vaccine provided 100% protection against each of these field isolates and against a local NDV strain obtained from the Institute of Veterinary Preventive Medicine, Tamilnadu, India, while unvaccinated chickens succumbed to challenge. The possible origin of epizootic viruses causing outbreaks in vaccinated flocks is discussed.

Efficacy of live adjuvanted mesogenic Newcastle disease vaccine in chickens.

120 white leghorn chickens primed with a lentogenic Newcastle disease (ND) live vaccine at 7 days of age were divided into three equal groups of 8 weeks of age and vaccinated with a live mesogenic ND vaccine (NDV). One group received only Newcastle disease mesogenic vaccine (RDVK) in normal saline, the second group received RDVK with groundnut oil as adjuvant and the third group received RDVK with liquid paraffin as adjuvant. Sera were collected at different time points for the assessment of antibody level against ND virus (NDV) by the haemagglutination inhibition (HI) test. The commonly used non-adjuvanted RDVK could not evince 100% protective HI titre beyond 11 weeks of age but in both the adjuvanted groups 100% protective HI titre was evident up to 20 weeks of age. On challenge at 20 weeks of age both the adjuvanted groups withstood challenge but in the non-adjuvanted group 80% of chickens withstood the challenge. A significant difference in immune response between the adjuvanted and non-adjuvanted groups was seen but not between both the adjuvanted groups. The advantage of vegetable oil (groundnut oil) as an adjuvant for live mesogenic ND vaccine has been discussed.

PATHOGENICITY AND IMMUNOSUPPRESSIVE PROPERTIES OF INFECTIOUS BURSAL DISEASE VIRUS FIELD ISOLATES AND COMMERCIAL VACCINES IN INDIA

The pathogenicity and immunosuppressive properties of two field isolates of infectious bursal disease virus (IBDV) and five commercial IBDV live virus vaccines marketed in India were evaluated in this study. The pathogenicity of the wild type viruses and vaccines were based on mortality, the bursa:body weight ratio and microscopic lesions in the bursa in 3-week-old chicks that received these viruses. The immunosuppressive effects of these viruses were evaluated by measuring the antibody responses to sheep red blood cells, Brucella abortus plain antigen and Newcastle disease virus (NDV) vaccine in one-day-old chicks. One field isolate (N35/93) was found to be more pathogenic and immunosuppressive than the other (N45/92) while none of the commercial mild ‘Lukert’ type vaccines were found to be pathogenic. One of the vaccine strains marked as ‘Mild Lukert type’ was highly immunosuppressive; one was moderate and one could be classified as mild. Both the intermediate vaccines tested were highly immunosuppressive.

Antigenetically Unusual Newcastle Disease Virus from Racing Pigeons in India

Newcastle disease virus isolated from an outbreak in racing pigeons in India was found to be velogenic, based on the mean time to death in 10-day-old embryonated hens eggs, the intravenous pathogenicity index in 6-week-old chickens and the pathogenesis in chickens and pigeons. The virus induced disease in chickens without prior adaptation in chickens. The virus was antigenically unusual since it could not be grouped with the available panel of monoclonal antibodies at the World Reference Laboratory for Newcastle disease, UK. However, commercially available lentogenic and mesogenic vaccines provided 100% protection to chickens against this antigenically unusual NDV.

A modified filter paper technique for serosurveillance of Newcastle disease.

Newcastle disease (ND) poses a continuous and unresolved threat to poultry farmers. In tropical countries, with a dense population of poultry in open houses near farms, eradication of ND is difficult. Hence, vaccination is necessary to control the disease. Assessment of the post-vaccinal immune response is essential to monitor the efficacy of a vaccination schedule and of the vaccines used. This can be done by the haemagglutination-inhibition (HI) test, which is easy to perform and rapid, but large-scale serosurveillance presents some problems. These include collection of the sera, their storage and transportation to a laboratory. To overcome some of these difficulties, the use of filter paper to collect blood samples for serosurveillance has been recommended (Beard and Brugh, 1977; Brugh and Beard, 1980; Giambrone, 1981; Rivetz et al., 1985). An attempt was made to reduce the test time by modifying the fdter paper technique using Whatman No. I filter paper for collection of blood samples, Brij-35 solution for quick elution of antibody, and a micro-HI procedure to evaluate the antibody content.

Postvaccinal immune response to regimens of Newcastle disease vaccination by filter paper sampling technique.

SummarySeven hundred and ten blood samples were collected at random from commercial layers in Tamil Nadu on Whatman filter paper No. 1 instead of the conventional method of serum collection. The birds were subjected to different Newcastle disease (ND) vaccination schedules and samples were collected to study the vaccinal response to ND at field level. Eluates were obtained from sample areas of filter paper using Brij-35 solution [detergent] and subjected to the micro haemagglutination inhibition (HI) test for ND antibodies. The HI titre ranged from less than 24 to 29. The possible causes of poor immune response to ND vaccinations are discussed.Résumé710 échantillons de sang furent collectés au hasard dans des élevages industriels dans le Tamil Nadu utilisant des filtres Whatman No. 1 au lieu de la méthode conventionnelle d’échantillonnage des serums. Les oiseaux furent soumis à différents traitements de vaccination contre la maladie de Newcastle et les échantillons furent recueillis pour étudier la réponse vaccinale contre la maladie de Newcastle au miveau environnemental. Les éluats furent obtenus à partir de la surface des filtres utilisant une solution de Brij-35 (détergent) et soumis à un test d’inhibition par micro-hémagglutination des anticorps contre la maladie Newcastle. Les titres d’inhibition par hémagglutination furent compris entre 24 et 29, les causes probables de cette faible réponse immunitaire face à la vaccination contre la maladie de Newcastle sont discutées.ResumenSe obtuvieron 710 muestras de sangre de ponedoras seleccionadas al azar en Tamil Nadu. En lugar de utilizar el método tradicional de obtención de suero, las muestras de sangre se recognieron sobre papel de filtro Waltham no. 1. Los animales habían recibido diferentes protocolos de vacunación frente a la enfermedad de Newcastle y las muestras se recogieron para estudiar la respuesta vacunal a nivel de campo. El papel de filtro se lavó con solución Brij-35 y después se realizó el test de inhibición de la microhemaglutinación para detectar anticuerpos frente a Newcastle. Los títulos de anticuerpos variaron entre 24 y 29. Se discuten las posibles causas de la baja respuesta observada.

Quantitative counter-immunoelectrophoresis for estimation of antibodies to infectious bursal disease virus.

Quantitative counter-immunoelectrophoresis was standardized to detect antibodies to the avian infectious bursal disease virus. This technique correlated well with the conventional quantitative agar gel precipitation test in estimating antibodies to IBDV. The use of blood dried on filter paper as an alternative to serum is discussed. QCIE is simple, easy to perform and faster than QAGP.

Dot-enzyme linked immunosorbent assay for demonstration of Newcastle disease virus infection.

Dot-enzyme linked immunosorbent assay (ELISA) was standardised to detect Newcastle disease virus (NDV) specific antigen in chicken tissues, embryos and allantoic fluid samples. Samples positive by virus isolation were also found positive by haemagglutination (HA) and haemagglutination inhibition (HI) tests and by dot-ELISA but negative samples were found negative by all the serological tests used. Dot-ELISA was able to detect 0.25-0.50 HA units of virus. The emerging utility of dot-ELISA for diagnosis of Newcastle disease virus infection has been discussed.

Immunorheophoresis for the diagnosis of infectious bursal disease.

The immunorheophoresis (IR) technique was used for the detection of infectious bursal disease antigen from bursae collected from field cases and experimentally infected chickens. When these results were compared with that of the agar gel immunodiffusion (AGID) test, they showed excellent agreement as determined by kappa value. However, the time taken for the appearance of the precipitin lines was reduced from 14-24 hr in the AGID test to 3-5 hr in the IR technique.

Comparison of Newcastle disease vaccines by serology using serum, tears and feather pulp samples

Seroconversion of 3 lentogenic commercial Newcastle disease (ND) vaccines and experimental V4 vaccines was compared based on the haemagglutination inhibition (HI) test against ND. It was found that for primary vaccination all the vaccines produced similar response but for secondary vaccinations V4 and LaSota were better than RDVF. Eighty-five samples each of serum, tears and feather pulp were collected from respective birds and antibody assessment was done against ND by HI test. The geometric mean HI titres (GMT) of serum samples were highest followed by tears and feather pulp samples before vaccination and 3 weeks after vaccination by oculonasal route and the difference was statistically significant (p<0.01). Three weeks after booster vaccination by oculonasal route, however, the GMT of serum samples were highest followed by feather pulp and tears samples. The ease of collection of feather pulp samples and their role in ND serology is discussed.