The Socio-economic Environment of Newcastle Disease Control Strategies for Backyard Poultry Systems[1],[2]

Roger Oakeley

Veterinary Epidemiology and Economics Research Unit
Department of Agriculture, The University of Reading
Earley Gate, P.O. Box 236, Reading RG6 6AT
E-mail: veeru@reading.ac.uk

Summary

Backyard poultry are an important source of income for many rural households in Africa, but is constrained by the presence of Newcastle disease. With limited resources available to control the disease, heat stable Newcastle disease vaccines have been championed as a means of generating community participation in control strategies. Trials in Zimbabwe have examined both the technical effectiveness of heat stable vaccines in controlling Newcastle disease, and their suitability for involving the rural community in vaccination activities. Reliability of the vaccines using alternative delivery methods and the capacity of rural communities to apply those methods are questioned. Sustainable Newcastle disease control strategies for extensive poultry systems cannot ignore the wider production and health concerns of extensive producers.

Key words: Backyard poultry, Newcastle Disease, Vaccine Approaches, disease control

Introduction

Zimbabwe is subject to sporadic outbreaks of Newcastle disease particularly in extensively raised poultry. In 1996, the ‘Emergency Assistance for the Control of Newcastle Disease’ project was initiated to develop a sustainable, community-based strategy for the control and prevention of Newcastle disease in backyard flocks. The project focused on the identification of an effective technical package, and the appropriateness of that package in the production and socio-economic context of the back­yard system. This paper reviews the results of technical vaccine trials, but focuses on the production and socio-economic context within which those trials were conducted.

Conventional methods for controlling Newcastle disease are based on live vaccine delivered by the intra-nasal, intra-ocular or intra-muscular routes. Live vaccines have traditionally been heat-sensitive and require storage at or below 4^°C. Consequently, there has been need for an effective cold chain in which to store vaccine until the point of vaccination. Complete and effective cold chains are expensive and difficult to maintain and this has limited Newcastle disease control in small and dispersed back­yard flocks in tropical climates.

Additional constraints cited for conventional vaccines include the suggestion that extensively raised birds are difficult to catch, and that vaccination is laborious and labour intensive (Spradbrow, 1994). Vaccination campaigns have remained the responsibility of veterinary professionals and technicians, with the inevitable high level of associated labour costs. A combination of cold chain, labour requirements and the search for a suitable vaccine has continued to hamper development of sustainable Newcastle disease control strategies for backyard poultry in tropical regions.

More recently, two heat resistant vaccine strains have been developed, known as V4 and I2, and two potential advantages have been put forward for backyard produc­ers. In theory, they remove the need for a complete cold chain and are potentially cheaper to deliver. Also, the heat-stable properties favour alternative delivery methods such as via coating on bird feed, or in water. Heat-stable vaccines may, therefore, offer the potential for a more cost-effective, community-based method of controlling Newcastle disease in backyard poultry.

The search for a community-based control strategy

A comprehensive survey of the backyard poultry production system and its socio-economic context was undertaken across 5 Provinces of Zimbabwe (Madzima et al, 1998a). The survey included a longitudinal production study, a seasonal study and informal interviews with women producers. The following discussion summarises key factors drawn from this survey relevant to the development of a community-based Newcastle disease control strategy.

Use of feed grains as vaccine carriers

From trials into potential feed carriers for V4 and I2, only rapoko[3] was found to be suitable, but not maize, rice, millet or sorghum. This indicates that the V4 and I2 vaccines are highly sensitive to the grain they are delivered on, and that no single grain type can be identified as suitable. This is confirmed by similar findings in both Africa and Asia. (Rushton, 1995; Spradbrow, 1994). To develop a feed-borne vaccine strategy, therefore, requires examination of all potential grains in any country, and possible separate trials in different areas of the country, since grain characteristics may vary from region to region. There is also limited understanding of the impact on the vaccine of grain variety, quality and condition, chemical additives present, and also the surfaces grains are fed on.

Significantly, in Zimbabwe only 15 % of producers provide supplementary feed for their birds, and feeding regimes vary significantly. If feed grains are not a traditional input for many backyard producers, basing a vaccine strategy on their use represents a significant constraint. As an example, rapoko is not grown in all areas of the country, nor is it widely available at all times of the year (Mavhenyengwa, pers. comm.[4]).

Although called ‘heat-stable’, no quantified definition has been applied to this term, and it is unclear how many hours and at what temperatures the vaccine can be kept before its potency deteriorates (Palya, 1998; Jackson, 1992). Vaccine performance is also affected by excessive vibration and extended exposure to direct sunlight (Madzima et al, 1998b). Feed-based vaccination, however, inevitably requires vibration during mixing and exposure to sunlight during application. Finally, the feeding rates of individual birds are difficult to monitor and control. To achieve protection, individual birds must consume a given quantity of grain and vaccine, but feeding rates and pecking order in flocks can disadvantage younger and weaker birds (Spradbrow, 1994; Jackson, 1992).

Backyard flock dynamics

The epidemiology of Newcastle disease under backyard systems remains unclear (Awan et al, 1994), but it is estimated that within a population, the disease can be considered under control if less than 30% of birds are infected (Palya, pers. comm.). The average backyard flock in Zimbabwe numbers 20 birds, and is com­posed of 8 chicks, 6-7 growers, 4-5 hens and 1 cock (Oakeley, 1998a). Based on rates of egg incubation and loss, and mortality in chicks and growers, flock turn­over rate due to the introduction of ‘new’ birds, means that from a point in time, the average flock may comprise of 30% unprotected birds within 4 months. This indicates the need for vaccination between 2 and 3 times a year if effective cover is to be maintained in these flocks (Oakeley, 1998b).

These statistics must be viewed in the light of vaccine trial results. Field trials focused on the use of rapoko as a carrier for both V4 and I2, but also examined water-based application of V4, and eye-drop delivery of I2 and the conventional vaccine La Sota. Birds in the various trial groups were vaccinated every month, for up to 6 months, and tested for antibody levels using the haemagglutination-inhibi­tion test. (Madzima et al, 1998a). Both I2 and La Sota delivered by the intra-ocular route afforded adequate protection rates after a single application. Water-borne V4 achieved less than 40% protection of flocks after three vaccinations, and feed-borne I2 and V4 less than 30% and zero protection, respectively, after six applica­tions (Palya, 1998).

These test results confirm findings from trials elsewhere in Africa and Asia (Palya, 1998; Aini et al, 1990; Fontanilla et al, 1994; Tantaswasdi et al, 1992; Bell et al, 1995; Spradbrow, 1994). The findings suggest the need for further develop­ment and improvement of heat-stable vaccines before feed - or water-based delivery strategies can offer an effective technical solution to Newcastle disease control (Bell et al, 1995; Oakeley, 1998b). However, there remains the question of how any control strategy can incorporate community participation, and thereby offer a more sustainable approach to Newcastle disease control in backyard poultry sys­tems.

The prioritisation of Newcastle disease control

Ultimately, maintaining control of Newcastle disease in backyard flocks will depend on the involvement of the farming community, and farmer enthusiasm reflects the level of priority they give the disease. A complex array of production and health constraints is associated with varying levels of technical, management and husbandry input in Zimbabwe. The survey identified massive variation between flocks in the levels of egg and bird off-take at every stage of the produc­tion cycle. While impossible to attribute to any single factor, this variation results from differential levels of egg and bird management, feeding, health care, chick rearing and other husbandry activities.

Despite the evident variation in backyard flock productivity, 78% of extensive producers surveyed claimed to have no support or contact with the formal veterinary and extension services. There is evidence that the research and extension sys­tem does not cater adequately, either for women producers, who are the primary stakeholders in extensive poultry, or for the system of extensive poultry production as a whole. Poultry production must be seen as only one of many household and farm activities, and is rarely the priority concern, even of women who tend to value it more highly than men. Other responsibilities such as household duties, other livestock or seasonal crop-related work can take precedence over poultry activities. It is, therefore, not clear how much additional time some households are prepared to commit to activities like poultry disease control.

Customary practices can also complicate vaccination campaigns. The transfer and movement of chickens between villages and regions is a fundamental part of the extensive system, enabling owners to use birds for celebrations, gifts and as ready sources of cash. These movements influence the epidemiology of the disease, and complicate the monitoring and control of vaccination cover. Mass vaccination campaigns have also been hampered by absence of producers at key times, and reports of outbreaks following previous campaigns (Mavhenyengwa, pers. comm.).

Most producers appear well informed about Newcastle disease and its impact, but it is only one of numerous health constraints threatening backyard flocks. There is widespread incidence of fowl pox, infectious bursal disease, losses to predators, and internal and external parasites, as well as considerable management and hus­bandry constraints (Oakeley, 1998b). No information is available on what propor­tions of losses are a result of different diseases or problems, and no quantitative data are available on the specific losses attributable to Newcastle disease.

The absence of a complete production and health extension package specifically aimed at extensive poultry producers was highlighted by the study. Since a sustained control strategy depends upon producer commitment, the benefits of that commitment must be clear and acceptable to the farming community. While there remain gaps in the services offered to backyard producers, limited commitment toward isolated health campaigns such as Newcastle disease vaccination can only be expected. This may be one reason why extensive poultry producers have limited interest in Newcastle disease control.

In addition, it is not clear how great a threat backyard producers perceive New­castle disease to be. In commercial systems, the threat is significant when large numbers of birds, in confined areas, can die within short time periods as a result of an outbreak. In extensive flocks, however, some birds can be salvaged in the face of an outbreak, through consumption, sale or gift (Spradbrow, 1994). Such strate­gies will greatly effect the true economic loss associated with an outbreak, but may not be reflected in the statistics of birds that die or are slaughtered in response to an outbreak.

Concluding discussion

A question remains over the readiness of backyard producers to adopt any strategy based on the use of supplementary feeds that do not currently feature in many backyard production systems. Not only does the purchase of feed grain represent a constraint to some producers, delivery procedures are also open to misapplication and problems of monitoring. Involving producers in feed-based vaccine delivery may, in practice, prove no less problematic than facilitating their participation in more conventional techniques. Zimbabwe now uses V4 delivered by intra-ocular route (Oakeley, 1998b), and is training individual producers how to handle and apply the vaccine in this way. It appears that the skills are being readily transferred to producers that catching birds is not a problem, and that subsequent vaccinations will be handled by producers themselves, with only limited input from veterinary staff.

It is clear that the potential risk of Newcastle disease to the poultry industry in Zimbabwe will ensure the issue remains a high priority. Equally clear is the need to sustain producer commitment and co-operation if the disease is to be controlled in the extensive poultry flock. Newcastle disease represents only one of many con­straints to the backyard sector in Zimbabwe. Other health, management and hus­bandry limitations have been largely ignored by the service sector, and community support for Newcastle disease control will depend on the commitment of the service sector to meet this much broader range of needs.

References

Aini, I., Ibrahim, A.L. and Spradbrow, P.B. (1990). “Vaccination of chickens against Newcastle disease with a food pellet vaccine”, Avian Pathology, 19, 371-384.

Awan, M.A., Otte, M.J. and James, A.D. (1994). “The epidemiology of Newcastle disease in rural poultry: A review”, Avian Pathology, 23, 405-423.

Bell, J.G., Fotzo, T.M., Amara, A. and Agbede, G. (1995). “A field trial of the heat resis­tant V4 vaccine against Newcastle disease by eye-drop inoculation in village poultry in Cameroon”, Preventative Veterinary Medicin,e 25,19-2.5

Fontanilla, B.C., Silvano, F. and Cumming, R. (1994). “Oral vaccination against Newcastle disease of village chickens in the Philippines”, Preventative Veterinary Medicine, 19, 39-44.

Jackson, A.R.B. (1992). “Observations on Some Difficulties Encountered in Trials with Oral Newcastle Disease Vaccination”, in Spradbrow, P.B. (ed), Proceedings: Newcastle Disease in Village Chickens. Control with Thermostable Oral Vaccines, No. 39, Can­berra: ACIAR.

Madzima, W.N., Gwaze, G., Mavhenyengwa, M., Chitate, F., Guta, M., Madekurozwa, R.,

Munyombwe, T., Nquindi, J. and Ncube, C. (1998a). Progress Report 3: Emergency Assistance for the Control of Newcastle Disease in Zimbabwe, Project TCP/ZIM/8821 (A), Rome: FAO.

Madzima, W.N., Gwaze, G., Mavhenyengwa, M., Chitate, F., Guta, M., Madekurozwa, R.,

Munyombwe, T., Nquindi, J. and Ncube, C. (1998b). Progress Report 4: Emergency Assistance for the Control of Newcastle Disease in Zimbabwe, Project TCP/ZIM/8821 (A), Rome: FAO.

Oakeley, R.D. (1998a). Emergency Assistance For The Control Of Newcastle Disease, Consultancy, Report on Rural Poultry Production-Socio-Economy, May 25th - June 9th 1998, Project TCP/ZIM/8821 (A), Rome: FAO.

Oakeley, R.D. (1998b). Emergency Assistance For The Control Of Newcastle Disease, Consultancy, Report on Rural Poultry Production-Socio-Economy, December 12^th -22nd 1998, Project TCP/ZIM/8821 (A), Rome: FAO.

Palya, V.J. (1998). Assistance For The Control of Newcastle Disease Phase II Of TCP/ZIM/4553 (E), Consultancy Report on Feed-Based Newcastle Disease Vaccine, December 12th-22^nd 1998, Project TCP/ZIM/8821 (A), Rome: FAO.

Rushton, J. (1995). Assistance to Rural Women in Protecting their Chicken Flocks Against Newcastle Disease, Consultancy Report on Rural Poultry Production-Socio-Economy, December 1995, Project TCP/RAF/2376, Rome: FAO.

Spradbrow, P. (1994). “Newcastle Disease in Village Chickens”, Poultry Science Review 5, 57-96.

Tantaswasdi, U., Danvivatanaporn, J., Siriwan, P., Chaisingh, A. and Spradbrow, P. B. (1992). “Evaluation of an oral Newcastle disease vaccine in Thailand”, Preventative Veterinary Medicine, 12, 87-94.