Investigations into the control of Newcastle disease in village chickens in Mozambique

• National Veterinary Research Institute, Mozambique

Village chickens have not been utilised to their full potential in many developing countries because of Newcastle disease, a viral disease that can produce mortalities of up to 100%. Commercial vaccines are unsuitable for developing countries because they must be kept within a cold chain from manufacturer to recipient chicken and the vaccinated population must be under strict physical control. Heat lability, high price (in foreign exchange) and large dose format (minimum 1000 doses) all mitigate against the use of these vaccines in village flocks.
A vaccine suited to village needs was needed, and ACIAR since 1984 has supported research and development to provide answers. The work has been based on an avirulent strain of the disease found in Australia, which was further selected for heat resistance that enabled its use without refrigeration in the village environment.
This was the vaccine (NDV4-HR) used in the initial ACIAR projects, commencing in Malaysia and extending to four other Asian countries. A commercial vaccine resulted, but the product was often unsuitable for village use because of cost and the large-dose format. ACIAR then sponsored the development of a new vaccine master seed, based on the Australian avirulent I-2 strain-with properties similar to NDV4-HR but no commercial ownership, and available for production in developing countries.
This project in Mozambique was an extension of small-scale trials that had been sponsored by ACIAR in Vietnam, Zambia and Tanzania.

The original objectives were concerned with vaccine production and testing and the investigation and development of distribution systems. Modified objectives as the project was extended were on training, development of extension strategies, research relevant to quality assurance and registration, and creation of the foundations for a large AusAID development project.

Activities in Mozambique involved laboratory and field testing of commercial heat-tolerant NDV4-HR vaccine, and the production, testing and distribution of I-2 vaccine, together with the development of field testing associated with a variety of extension packages. Field trials were initiated in the first year after a prolonged phase of extension activities to educate field officers and villagers. Three routes of vaccination (eye drop, drinking water and oral drench) were compared by measuring the antibody response. Importation of I-2 master seed was delayed until the second year of the project. The National Veterinary Research Institute (INIVE) then produced I-2 vaccine (in eggs from the institute flock) which was tested in the laboratory and in the field, using protocols developed for the NDV4-HR trials.

Research work at The University of Queensland emphasised basic studies that would help with the production of thermostable vaccines in laboratories in developing countries and with the acceptance of the vaccines by registration authorities. Challenge trials, which cannot be undertaken in Australia, took place in Mozambique.

NDV4-HR vaccine was effective in both laboratory and field trials in Mozambique. The vaccine spread from vaccinated to unvaccinated chickens under laboratory conditions, produced adequate levels of antibody and gave absolute protection against contact challenge with virulent virus. In the field NDV4-HR vaccine delivered by eye drop gave the best antibody response, resulted in the greatest increase in flock size and was preferred by farmers.

I-2 vaccine was produced under experimental conditions and subjected to tests similar to those used with NDV4-HR vaccine. Again there was spread from vaccinated to unvaccinated chickens and absolute protection against a challenge that killed all control chickens. In the field eye drop administration of I-2 vaccine also gave the best results, yielding the greatest increase in flock size and was the farmers' preferred option. I-2 vaccine then went into production at INIVE, with a peak production of 2 million doses in 1999-2000. The vaccine was supplied for vaccine campaigns in Mozambique.

It was shown that effective vaccination resulted in greatly increased numbers of chickens in village flocks. The individual elements of a vaccination campaign are now established-production of an appropriate vaccine, demonstration of efficacy and safety in the field, mechanisms for cost recovery, a distribution system, trained vaccinators, aware NGOs and an effective extension package.
At the University of Queensland a safety trial confirmed that I-2 vaccine is safe in chickens when administered at 10x and 100x the recommended minimum dose, which exceeds the international standard. A subsidiary Master Seed was prepared with an information dossier that will be included with future dispatches of the seed.
The laboratory in Brisbane has been able to train laboratory workers from other African and Asian countries, and those people will be pivotal in national vaccine production. The University of Queensland is investigating the establishment of Graduate Certificate courses on the Production and Quality Control of I-2 ND vaccine and village chicken production (dealing with health, production and extension issues).
The benefits will be felt beyond Mozambique. The seed material can now be taken by other countries with confidence. Experience gained with vaccine production at INIVE can be transferred to other production laboratories. The large range of posters, laboratory manuals and audiovisual extension materials can be modified for use in other countries.

This project has formed the basis for the three-year AusAID-funded Southern Africa Newcastle Disease Control Project that commenced in 2002.