Evaluation of Factors Limiting Turkey Production in Enugu State and Comparison of Pathology Associated With Newcastle Disease in Turkeys and Chickens

Abstract

The objectives of this study were to evaluate the factors limiting turkey production in Enugu State, Nigeria, determine the sero-prevalence of Newcastle disease (ND) virus infection in turkeys raised in Enugu State and compare the clinical signs and lesions of velogenic ND virus (NDV) in turkeys and chickens.The study consisted of a cross-sectional survey of turkey producers in the three senatorial zones of Enugu State and an experimental infection of chickens and turkeys with a velogenic NDV (VNDV). Three Local Government Areas in each of the three senatorial zones, Enugu East, West and North were purposively selected for the survey because of the preponderance of turkeys in the selected areas. A structured questionnaire was used for data collection. Two hundred and fifty copies of the questionnaire were administered to turkey producers in the selected areas. Five hundred and sixty-nine serum samples were randomly collected from unvaccinated turkeys in ninety backyard poultry farms in Enugu East, Enugu West and Enugu North senatorial zones. The sera were analysed for ND antibody titres using haemagglutination inhibition (HI) test. For the challenge experiment, 120 turkeys and 120 chickens were used. The 120 turkeys and chickens were divided into two groups of sixty vaccinated and sixty unvaccinated. The vaccinated groups were given HB1 (I/O) and La Sota ND vaccines on day 1 and day 21 of age respectively. Inoculated birds were given 0.2 ml (10 6.46 per ml) of the VNDV (KUDU 113) intramuscularly, at 6 weeks of age. Morbidity and mortality, changes in live body weight and gross lesions were recorded. Antibody response of the birds were carried out by collection of sera on days 0, 5, 10, 15 and 21 PI. Pack cell volume (PCV), haemoglobin concentration (HbC), red blood cell count (RBC) and white blood cell (WBC, total and differential) were carried out on days 0, 3, 6, 10, 15 and 21 PI. Data generated from survey were subjected to descriptive statistics and Chi-square test, while for the challenge studies, students’ t test and one way analysis of variance were used. Variant means were analyzed post hoc using the least significant difference method. Significance was accepted at p < 0.05. Turkey production was carried out mainly by adult female in Enugu East (65.3%) and Enugu West (57.7%) and adult males in Enugu North (51.1%) Although most (87.5%) of the respondents in the three senatorial zones had formal education, they were not (48.8%) experienced in turkey production. The major (52.5%) age group involved in the business was 36-50 years old. Turkey production in Enugu State was generally a part-time occupation as respondents were engaged in other primary occupation such as crop farming, trading, civil service etc. The management system adopted by the respondents in the three senatorial zones, Enugu East, Enugu West and Enugu North respectively were mainly (20.4%,55.0%,47.3%) intensive or semi-intensive (59.2%,34.0%,36.8%). Majority (84.8%) of the respondents in Enugu State keep turkeys in small numbers (1-20) along with local chicken, exotic chicken, guinea fowl, ducks etc. According to majority (91.2%) of the respondent, turkey production was found to be profitable venture based on the cash generated after sale of the turkeys. Newcastle Disease (57.0%), fowl pox (65.0%), fowl typhoid (6.0%), fowl cholera (3.7%), ectoparasitism (1.0%), fracture and nutritional deficiencies (2.6%) were the diseases constantly encountered in turkey production by majority of the respondents and of all the diseases reported by the respondents, fowl pox (65%) and Newcastle Disease (57%) were the major diseases limiting production in the study area. The major factors limiting turkey production in Enugu State as identified by the respondents in the study area were high cost of feed (86.5%), high disease morbidity and mortality (85.2%), inadequate access to veterinary care (78.80%), unavailability and high cost of poults (74.40%), lack of management skills (63.3%) and lack of capital (61.7%) while minor problems were low reproductive potential (56.9%), theft and predators (52.5%). Out of the 569 sera collected from the three senatorial zones and tested for Newcastle Disease virus antibody, a total of 186 sera representing 32.7% were positive for Newcastle Disease antibody. Out of the 186 sera, 138 (74.1%) had titres of 8 and above and were considered protected while 48 (25.9%) had titres of less than 8 and considered to be at risk. The mean HI antibody titre in Enugu East senatorial zone against ND was significantly (P<0.05) higher than mean HI antibody titres in Enugu West and North senatorial zones. The results showed that these turkeys were exposed to Newcastle Disease Virus. Following intramuscular inoculation with the KUDU 113, severe depression, whitish -greenish diarrhoea, lethargy, hunched posture, tremors and torticolis were consistent clinical feature observed in unvaccinated turkeys and chickens while mild depression and lethargy were observed in vaccinated chickens and very mild clinical signs in few vaccinated turkeys. Morbidity was 100%, 92%, 22.2% and 4.1% in unvaccinated infected chickens and turkeys, vaccinated inoculated chickens and turkeys respectively, while mortality of 90%, 80%, 13.3% and 0% were recorded for unvaccinated inoculated chickens and turkeys, vaccinated inoculated chickens and turkeys respectively. Reduction in weight was highly significant in both unvaccinated and vaccinated inoculated groups (p<0.05). Postmortem examination showed atrophy of the lymphoid organs (thymus, bursa of Fabricius and spleen) and congestion of kidneys in inoculated groups. Haemorrhages on the mucosa of the proventriculus, sharply-demarcated haemorrhagic ulcers in the intestine and haemorrhagic and swollen caecal tonsils were observed only in inoculated chickens. Congestion of the brain vessels was present in inoculated turkeys. By day 6 PI all the unvaccinated inoculated chickens had died showing no significant changes in the weights of the thymus. Inoculated vaccinated chickens also showed no significant changes in thymic weights (p>0.05). But the gross lesions of the control and inoculated chickens showed clear reduction in sizes of the thymus of both unvaccinated and vaccinated inoculated chickens on days 5 and 6 PI. The only change in the weight of the spleen was significant reduction in vaccinated inoculated chickens on day 5 PI only. The gross lesions showed clear atrophy of the spleen in vaccinated and unvaccinated inoculated chickens on day 10 and 5 PI respectively and in the vaccinated and unvaccinated inoculated turkeys on days 20 and 10 PI respectively. The weights of the bursa were lower (p<0.05) in the unvaccinated inoculated chickens on days 3 and 5 PI and days 3, 10, 15 and 21 PI in the unvaccinated inoculated turkeys. There was a significant increase (p<0.05) in antibody titre in both inoculated unvaccinated/ vaccinated cockerels and turkeys. Newcastle Disease virus was detected in brain, intestine and spleen but none detected in the cloacal swabs. No significant (p>0.05) changes were observed in the erythrocytic parameters in chickens while there was a significant decrease (p<0.05) in PCV on day 15 PI in unvaccinated turkeys. Significant (p<0.05). leucocytosis, heterophilia and lymphopenia were observed in unvaccinated inoculated chickens on day 3PI while days 3, 10 and 21PI for unvaccinated turkeys. Despite the factors limiting turkey production as outlined by the respondents such as high cost of feed, high disease morbidity and mortality, inadequate access to veterinary care, unavailability and high cost of poults, lack of capital and lack of reasonable degree of management skills, turkey production has great potential in bridging the animal protein supply therefore, poultry farmers should be encouraged by the government to increase their level of production by establishing reliable breeding centres in the South East Nigeria which will ensure regular supply of day old poults, subsidizing the price of feed and drugs, prompt disease control by employment of more veterinarians, provision of animal health care delivery vehicles provision of poultry vaccines, provision and easy access to soft loans. These will boost overall production and increase the standard of living of the farmers. The seroprevalence of 32.7% shows exposure of the turkeys to Newcastle Disease virus thus the local husbandry practice of keeping different species together, increases the chances of transfer of Newcastle Disease virus across these species, it will be noteworthy to recommend that turkey farmers be encouraged in the study area to keep species separately and vaccinate against Newcastle Disease regularly. Susceptibility to highly virulent NDV was shown to vary among chickens and turkeys. However, in general, disease among turkeys was less severe, despite virus detection in its various organ (Spleen, Intestine and Brain), than in chickens. Intramuscular inoculation test showed high mortality in chickens with intestinal ulcers and haemorraghic lesions which indicated that the KUDU-113 NDV strain is a velogenic viscerotropic virus.