Newcastle disease virus immunization with I-2 vaccine: a case study of local free range chickens in rural communities in Morogoro, Tanzania

R S Mwakapuja, P L M Msoffe*, F Kajuna, D Bunn** and C J Cardona***

mwakapuja@yahoo.co.uk
Faculty of Veterinary Medicine, Sokoine University of Agriculture, Morogoro, Tanzania
* Directorate of Undergraduate Studies, University of Dodoma, Dodoma, Tanzania,
** Wildlife Health Centre, University of California Davis, USA,
*** School of Veterinary Medicine, University of Minnesota, St. Paul, USA

Abstract

This study evaluates the immunization status of free-range local chickens (FRLC) following a mass vaccination program against Newcastle disease virus (ND) that was carried out in Mvomero district, Morogoro, Tanzania. Six villages from two wards (one trial and one control ward) were involved. A total of 819 chickens from the two wards were tested by haemagglutination inhibition (HI) for ND antibodies following I-2 vaccination in the trial ward. The vaccine was administered to FRLC by eye drop in trial villages by trained community vaccinators while chickens in the control villages were not vaccinated. Birds with HI antibody titres equal or greater than 2³ (HI≥2³) were considered immune.

The percentage of birds in each age category with protective NDV antibodies in the trial ward were chicks (25.3%), growers (53.3%) and adults (84.8%), while the percentage in the control ward were chicks (14.0%), growers (30.1%) and adults (40.4%). The percentage of immune chickens by age categories in the trial ward were significantly higher (p<0.05) compared to immune birds in the control ward. The current study indicates that the National vaccination regime is more successful in growers and adults versus chicks. In order to improve flock protection against ND, the vaccination program should cover chicks. This can be achieved if farmers schedule a special vaccination program for chicks and harmonize hatching to conform to the vaccination regime.

Keywords: Immunization, Newcastle disease, thermostable vaccine, village chickens

Introduction

Free-range village poultry are an important component of the socio-economics of Tanzanian rural communities. Village poultry demand is increasing in the urban communities (Spradbrow 2001; Muhairwa et al 2008). However, the productivity of the village poultry is hampered by diseases and other factors, Newcastle disease (ND) is considered the most important cause of death among village chickens of all ages in Tanzania and other developing countries where most poultry are raised as free-ranging scavengers (Minga et al 1989; Yongolo et al 1998; Alders et al 2002). ND vaccination is the best and most cost effective means of ND control and has been used successfully in village settings all over the world to reduce the clinical disease associated with outbreaks of ND (Msoffe et al 2010). Previous studies indicated that I-2 Newcastle disease (ND) vaccine induces high antibody levels and protective immunity in vaccinated chickens in field and laboratory trials when the vaccine administered via eye drop (Mgomezulu et al 2009; Komba et al 2012).  The efficacy of I-2 ND vaccine has been manifested through increased average flock sizes and decreased mortality incidences reflecting significant control of ND (Harrison and Alders 2009; Msoffe et al 2010). 

The thermostable I-2 ND vaccine is a practical and affordable product for rural poultry farmers compared with other vaccines based on strains F, B1 and La Sota. These other vaccines require sound transport and cold chain for effective administration (Bensink and Spradbrow 1999). I-2 ND vaccine showed no adverse reaction after laboratory and field trials (Dias et al 2001). I-2 ND vaccine is based on an Australian strain of avirulent thermo tolerant ND virus; has strong antigenicity and can spread from bird to bird (Spradbrow et al 1995). Bensink and Spradbrow (1999) reported that I-2 produces HI titres that are at or exceed protective levels of 2³ (Allan and Gough 1974).  

The serological response to I-2 eye drop vaccination has been predictable in controlled laboratory trials (Mgomezulu et al 2009). The I-2 vaccine strains induced protection in all vaccinated birds and those in contact with them against a local virulent strain of ND virus. However, when ND vaccine is used under field (village) conditions, the responses are more variable and less predictable. On a population basis, protection rates in excess of 60% are obtainable and acceptable (Spradbrow 1994). In the current investigation, we studied the impact of I-2 ND vaccine had on the control of ND in free-range chickens raised under village conditions typical of rural Tanzania. 

Materials and methods

Study area 

The trial was carried out in Mvomero district in Morogoro region. One administrative ward namely Mzumbe was selected for vaccination program while Mkundi ward was selected as control ward. Vaccination program was conducted in three trial villages namely Lubungo, SangaSanga and Vikenge in the Mzumbe ward while no vaccination program was carried out in three non- trial villages from Mkundi ward including Mawasiliano, Ngulwandege and Kilongo. The selection of the villages was based on their geographic locations and logistical convenience for samples shipment to the Faculty of Veterinary Medicine (FVM) laboratories. Three sub-villages were randomly selected from each village. 

Newcastle disease vaccination program in free range chickens  

A mass vaccination program was carried out and coordinated by Newcastle Disease Control Program project (NDCP). I-2 ND vaccine (Batch: VD67-106, Veterinary Central Laboratory, Dar es Salaam, Tanzania) was used. The vaccine was stored between 0ºC and 8ºC at FVM laboratory; the vaccines were distributed to the vaccinator one day before the scheduled vaccination day.  Prior to the vaccination program two vaccinators were identified from each trial village and trained for proper handling and administration of I-2 ND vaccines. The vaccine was administered through eye drop during morning hours. Birds in trial villages were vaccinated against ND four times at three-month intervals in a period of 12 months. The vaccination program was carried out in September 2008, January, May and September 2009. In the control ward, birds were not provided with vaccines by the project. However farmers were not restricted from carrying out vaccination to their flocks. Normally in non trial villages, few households carried out ND vaccination once in 12 months; the households were identified and the chickens excluded from analysis, instead the households were replaced by households with unvaccinated flocks.   Every attempt to match project and control villages on size, ethnic composition, location and poultry population was made. The target population of chicken flocks was grouped into three age categories including chicks (0-6 weeks), growers (7-20 weeks) and adults (weeks>20) groups.  

Evaluating Clinical Signs and Sample Collection 

All flocks in households were clinically examined by a veterinary clinician from NDCP-SUA and ward livestock officers to rule out ND, fowl pox, infectious coryza and vitamin A deficiency. Rectal swabs were collected from each sampled bird for helminthological and coccidial examinations. Data was collected in April, May June and August, 2009. Twelve birds were randomly selected for sampling from each household; the first four birds under each age category were selected out for sampling as the exited their house/confinement. Blood samples were collected from all the selected birds. About 1-2 ml of blood was collected aseptically by venipuncture.  Blood samples were kept at room temperature for about 12 hours for serum separation.  Sera were collected into sterile eppendorf microtubes and stored at -21^oC at the Faculty of Veterinary Medicine (FVM) Microbiology laboratory before analysis. All collected sera were tested by the end of September 2009. 

Determination of HI antibody titres  

Newcastle disease virus antibody titres were determined by haemaglutination inhibition (HI) test.  The test was performed in 96-well V-bottomed micro titre plates as described by Allan and Gough (1974). Birds with haemaglutination inhibition (HI) antibody titres equal or greater to 2³ (HI titres≥2³)  were categorized as immune against ND while those with HI antibody titres less than 2³ were categorized as not protected against the ND. The birds with HI titres of 2¹and 2² were considered as potential candidates to mount protective titres. The HI titre is expressed as the reciprocal of the highest positive dilution of the serum.  

Data management and statistical analysis 

A database was developed to store quantitative data using Microsoft Excel. Statistix 9 analytical software (Version 9.0) was used to compute descriptive statistics and frequency distribution of variables. One-Way ANOVA was used to test the significance of the differences of continuous variables and means of birds with protective and reactive HI titres. Levene’s test was used to test the homogeneity of within-group variances. Differences at p<0.05 were considered significant. 

Results and Discussion

Humoral immune response to I-2 vaccine 

A total of 440 and 379 serum samples were collected from trial and control villages, respectively. Villages and number of chickens in brackets sampled from trial villages were Lubungo (150), Vikenge (146) and SangaSanga (144) while in control villages were Mawasiliano (125), Ngulwandege (134) and Kilongo (120). Percentages of birds with protective NDV antibodies in six villages are shown in Tables 1 and 2. The overall percentages of individual age categories and comparison of birds with protective titres in trial and control wards are shown (Table 3).  

The percentage of birds with protective NDV antibodies in trial villages was higher compared with that from control villages. Also the results showed that there were significant differences between the percentages of immunized birds by age category in trial and control villages. Adult birds had the highest antibody titres while chicks had the lowest in the flocks. The higher percentage of immunized adult birds in the villages might be because adults had received more than one vaccination boosters compared to the younger ages. This observation is consistent with the findings by Rao et al (1987) who reported that NDV maternal antibodies persist for up 9^th to 10^th day of life but 15 days-old chicks have no detectable levels of NDV antibodies. Furthermore, the study showed that numbers of adults with protective NDV antibodies in trial villages were significantly higher than control villages. This is because birds in trial villages were exposed to more vaccination booster compared to chickens in control villages. 

Generally, the numbers of seropositive birds in trial villages (Mzumbe ward) were higher than birds in control villages (Mkundi ward). However, there was no significant difference in the percentage of age categories with protective NDV antibodies between the villages in the same wards. This was probably due to the consistent performance of the immunization and the synchronized vaccination program in the trial villages. Unvaccinated birds (in trial villages) were probably immunized by coming in contact with vaccinated adult birds. Also eggs laid by immunized hens hatched immunized chicks. Vaccinated birds, regardless of the method, stand a great chance of being immunized as opposed to non-vaccinated ones. This may explain the situation in control villages in which there was relatively lower number of immunized adults. The present results are in line with that of Edison et al (1982) and Yeo et al (2003) who reported that absorption of NDV antibodies from eggs to chicks in gallinaceous birds among day-old chicks are equivalent to those of their immunized parents.  Also the results are in agreement with that of Van Eck (1990), who found that NDV antibody titres in egg yolk were consistent with maternal NDV antibody titres. Similar results were also reported by Msoffe and others (2002).   

There was no significant difference in the percentage of immunized age categories between the trial villages. The different of within and between variances in some project villages is probably due to fact that local chicken ecotypes had divergent response towards ND vaccines (Msoffe et al 2002; Msoffe et al 2005).  Moreover village chickens portray high selection for antibody responses to vaccines as well as for period of responses (Msoffe et al 2002). In each ecotype there are birds with high and low, early and late responses to ND vaccination in controlled settings. This is also manifested in the current study in which birds vaccinated in the same age category presumably with the same exposures had different immunity. In the current investigation, chick ages ranged from 1 to 6 weeks. This implies that the birds had different status of maternal and in contact antibodies. Therefore, vaccination had different effects on some groups of birds. Vaccine administration to chicks with maternal antibodies or immunization can cause neutralization or boost the birds’ immunity to ND. 

According to Spradbrow (1994), birds with HI antibody titres of 1:2 and 1:4 cannot be presumed to be susceptible to challenge. These birds can be categorised as those which respond late to the vaccine. The present study revealed that flocks in all trial villages had rising humoral responses after I-2 immunization while there was no consistency of humoral response in control villages. This adds further support to the importance of coordinated, mass vaccination programmes to achieve uniformity in flock immunization to control ND at the village level. Also this can give a clear picture and anticipate the trend of the disease control programme.  

Conclusion

• At village level, a well-coordinated program is essential for implementing successful ND immunization. The current study indicates that the National vaccination regime is more successful in growers and adults versus chicks. Thus it could increase bird survival but overall flock mortality might be still high. In order to improve flock protection against ND, the vaccination program should cover chicks. This can be achieved if farmers schedule a special vaccination program for chicks and harmonize hatching to conform to the vaccination regime.

Acknowledgements

This project was supported through funding from the Global Livestock Collaboration support programme. The authors are grateful to the Jim Ellis Mentorship Program for sponsoring Dr. Richard Mwakapuja’s work in this study. We are indebted to the Faculty of Veterinary Medicine at Sokoine University of Agriculture for provision of technical support and laboratory facilities.  

References

Alders R, Dos-Anjos F, Bagnol B, Fumo A, Mata B and Young M 2002 Controlling Newcastle disease in village chickens. Brown Prior Anderson, Melbourne. pp. 128.

Allan W H and Gough R E 1974 A standard haemagglutination inhibition test for Newcastle disease; a comparison of macro and micro methods. Veterinary Record 95: 120−123

Bensink Z and Spradbrow P 1999 Newcastle disease virus strain I-2: a prospective thermostable vaccine for use in developing countries. Veterinary Microbiology 68: 131−139 

Dias P T, Alders R G, Fringe R, and Mata B V 2001 Laboratory and Field Trials with Thermostable Live Newcastle Disease Vaccines in Mozambique. In: Alders, R. G. and Spradbrow, P. B. ed. SADC Planning Workshop on Newcastle Disease Control in Village Chickens. ACIAR Proceedings of an International Workshop, Maputo, Mozambique, 6-9 March, 2000. 103:91-96

Edison C S, Thayer S G, Villegas P and Kleven S H 1982 Vaccination of broiler chicks from breeder flocks immunized with a live or inactivated oil emulsion Newcastle disease vaccine. Poultry Science 68: 1621−1629

Harrison J L and Alders R G 2009 An assessment of chicken husbandry including Newcastle disease control in rural areas of Chibuto, Mozambique Tropical animal Health and Production 42 (4): 729-736

Komba E V G, Mbyuzi A O and Mulangila R C T 2012 Adoption of I2VaccineImmunization of Village chickens against Newcastle disease virus in Southern Tanzania: Immune status of farmers vaccinated birds. Journal of Agriculture Science 4(4):23-28

Mgomezulu R A, Alders R G, Chikungwa P B, Young M P, Lipital W G and Wandal G W 2009 Trials with a thermotolerant 1-2 Newcastle disease vaccine in confined Australorp chickens and scavenging village chickens in Malawi.  Available from http://aciar.gov.au/files/node/11133/PR131%20part%202.pdf

Minga U M, Katule A, Maeda T and Mussasa J 1989 Potential and problems of the traditional chicken industry in Tanzania. In: Proceedings of the 7^th Tanzania Veterinary Association Scientific Conference (Msola, P, Editor) 3-5 December, 1989, Arusha Tanzania 115-117

Msoffe P L M, Bunn D, Muhairwa A P, Mtambo M M A, Mwamhehe H, Msago A, Mlozi M R S and Cardona C J 2010 Implementing poultry vaccination and biosecurity at the village level in Tanzania: a social strategy to promote health in free-range poultry populations. Tropical Animal Health and Production, 42: 253–263

Msoffe P L M, Mtambo M M A, Minga U M, Gwakisa P S, Mdegela R H and Olsen J E 2002 Productivity and natural disease resistance potential of free-ranging local chicken ecotypes in Tanzania. Livestock Research for Rural Development volume 14, Article #3. http://www.lrrd.org/lrrd14/3/msof143.htm

Msoffe P L M, Mtambo M M A, Minga U M, Juul-Madsen H R and Gwakisa P S 2005 Genetic structure among the local chicken ecotypes of Tanzania based on microsatellite DNA typing. African Journal of Biotechnology 4(8): 768−771

Muhairwa A P, Msoffe P L M, Mtambo M M A, and Ashimogo G 2008. Misingi ya ufugaji kuku wa asili. Mwongo wa ufugaji bora wa kuku wa asili vijijini pp 1-36

Rao A S, Chetty V L K, Prasal P B, Reddy G V and Reddy B D 1987 Persistence of maternal antibodies against Newcastle disease virus in chicks from immune parents and its effect on vaccination. Journal of Immunology and Infectious Diseases 8: 105−110

Spradbrow P B 1994 Newcastle Disease in village chickens. Poultry Science Review 5: 57-96.

Spradbrow P B 2001 The epidemiology of Newcastle Disease in village chickens. In: Proceedings of SADC Planning International Workshop on Newcastle disease control in village chickens. (Edited by Alders R G et al) 6–9 March, 2000. Maputo, Mozambique. 53-55

Spradbrow P B, Bensink Z and Grimes S 1995 Small scale production and testing of Newcastle disease vaccine manual produced for an ACIAR-funded workshop, held at the Poultry Reference Laboratory, Onderstepoort, 4-6 December, 1995.

Van Eck J H 1990 Protection of broilers against Newcastle disease by hyperimmunization of the dams. Veterinary Quarterly 12: 139−145

Yeo S G, Nagy E and Krell P J 2003 Indirect method for prediction of haemagglutination inhibition antibody titres to Newcastle disease virus in chickens by titration of antibodies in egg yolk. Journal of Veterinary Diagnostic Investigation 15: 184−187

Yeo S G, Nagy E and Krell P J 2003 Indirect method for prediction of haemagglutination inhibition antibody titres to Newcastle Disease virus in chickens by titration of antibodies in egg yolk. Journal of Veterinary Diagnostic Investigation 15: 184–187

Yongolo M G S, Machang’u A M and Minga U M 1998 Newcastle Disease and Infectious bursal disease among free-range village chickens in Tanzania. Available at http://www.google.co.tz/search.11-Newcastle-Yongolo

Received 27 December 2011; Accepted 19 June 2012; Published 1 July 2012

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