- Journal List
- Vet World
- v.15(12); 2022 Dec
- PMC9880837
As a library, NLM provides access to scientific literature. Inclusion in an NLM database does not imply endorsem*nt of, or agreement with, the contents by NLM or the National Institutes of Health.
Learn more: PMC Disclaimer | PMC Copyright Notice
Vet World. 2022 Dec; 15(12): 2979–2985.
Published online 2022 Dec 29. doi:10.14202/vetworld.2022.2979-2985
PMCID: PMC9880837
PMID: 36718316
Mutaz A. I. Hussein,1,2 Nussieba A. Osman,3 Mohamed T. Ibrahim,4 Ayman M. Alhassan,5 and Naglaa A. Abass1
Author information Article notes Copyright and License information PMC Disclaimer
Abstract
Background and Aim:
Newcastle disease (ND), a major constraint to poultry production worldwide, is a highly contagious disease of many species of domestic, exotic, and wild birds caused by ND virus (NDV). Epidemiological studies are lacking regarding ND in village chickens, including the traditional and intensive production systems used in Sudan. However, it is necessary to develop appropriate strategies to control the disease. Therefore, this study aimed to estimate the flock- and bird-level seroprevalence of NDV in backyard chickens in West Kordofan State, Sudan, and to identify the risk factors associated with ND in the study area.
Materials and Methods:
The seroprevalence of the circulating NDV and bird-level risk factors associated with ND was determined in backyard chickens from March to October 2017, in six villages (Alnowara, Alleait, Geibaish, Baiad, Sougoh, and Alnuhoud) in the Geibaish and Elnuhoud localities of West Kordofan State.
Results:
Using the hemagglutination-inhibition test, the bird- and flock-level seroprevalences of antibodies to NDV were estimated as 20.6% (78/378) and 45% (18/40), respectively. Bird-level NDV seropositivity in backyard chickens was significantly associated with the reason for raising chickens, type of housing, contact with neighboring poultry, contact with wild birds, and chicken mortality caused by infectious diseases (p ≤ 0.05).
Conclusion:
This study indicated that NDV is circulating in backyard chickens and may act as a potential source of infection for other birds and thus persistence of ND among local traditionally managed chickens in the areas of West Kordofan State. Risk factors contributing to ND occurrence are important for designing appropriate prevention and control strategies.
Keywords: backyard chickens, epidemiology, Newcastle disease virus, Newcastle disease, risk factors, seroprevalence, Sudan
Introduction
Poultry are generally the most abundant livestock in resource-poor areas and contribute significantly to food availability by supplying nutrient-rich and culturally acceptable products for human utilization and by enhancing crop, vegetable, and other livestock production by providing manure and pest control [1]. Traditional small-scale production from mainly indigenous stock provides the bulk of poultry output in almost all developing countries, including Sudan [2, 3], and remains the main source of dietary protein in the household [4].
Newcastle disease (ND) is caused by the avian orthoavulavirus-1 (formerly named avian paramyxovirus type-1, APMV-1), a member of the genus Avulavirus in the subfamily Avulavirinae, family Paramyxoviridae, and order Mononegavirales [5, 6]. Twenty serotypes of the APMV (1–20) have been described; however, all ND virus (NDV) isolates were identified in APMV serotype-1 [7]. Based on the fusion gene sequence, strains of APMV-1 were classified into two classes (I and II), and these classes were further classified into genotypes (I–XVIII) [8, 9].
The first records of ND in Sudan date from the 1950s and both lentogenic and velogenic NDVs were reported [10, 11]. The morbidity and mortality rates can reach 100% in outbreaks caused by velogenic strains [12]. Newcastle disease is the major constraint of village chickens in Sudan, similar to the situation in other developing countries [3, 13, 14].
No detailed epidemiological studies have been conducted in Sudan regarding ND in village chickens. To develop appropriate strategies to control the disease, epidemiological studies should be conducted in the traditional as well as intensive production systems in the country. This study was designed to estimate the seroprevalence of NDV in backyard chickens in West Kordofan State and to identify bird-level risk factors in the study area. West Kordofan State was selected as a representative for the western part of the country, where generally few studies were conducted.
Materials and Methods
Ethical approval
This study does not require the approval of the Institutional Ethics Committee as live animals were not used in the study.
Study period and location
We conducted a cross-sectional study from March to October 2017. This study was conducted in two localities of West Kordofan State in Sudan, namely, Elnuhoud and Geibaish (Figure-1). Elnuhoud locality covers an area of 14,496 km2 and lies between latitude 12–14° north and longitude 27–30° east. It has an annual level of rainfall ranging from 281 to 455 mm in the semi-desert area. Geibaish locality has an area of about 6125 km2 and is located at latitude 11°30’–12°30’ N and longitude 27°35’–28°30’ E. The area features a semi-desert climate with an average annual rainfall ranging from 105 to 351 mm. At the time of the study, there were no estimates of poultry population and backyard chickens in the state.
Figure-1
Map of Sudan showing West Kordofan State (left). The study area Alnuhoud and Geibaish localities in West Kordofan State were indicated (right) [Source: Dr. Samahir Galal Ismail Adam, Ministry of Animal Resources, Khartoum, Sudan].
Study population
The required sample size was based on detecting an expected NDV prevalence of 41.8% that had been previously assessed [15] with 95% confidence interval and 5% precision [16]. Therefore, the calculated sample size was estimated at 374.
In the study area, chickens are traditionally kept as free-ranging poultry by the villagers in the backyard, possibly with simple nightshades, and complete absence of veterinary services; only 21.4% of the families reared backyard chickens for their own consumption, while the majority (78.6%) raised them for income. Six villages, Baiad, Sougoh, and Alnuhoud in Alnuhoud locality and Alleait, Alnowara, and Geibaish in Geibaish locality were purposively selected for the epidemiological study because of the presence of backyard chickens (Figure-1).
A total of 378 sera were collected from the Alnuhoud (178) and Geibaish (200) localities, from chickens of >3 months of age, including unvaccinated and apparently healthy chickens. In the investigated localities, the 378 backyard chickens originally belonged to 40 flocks reared by 40 randomly selected households. All sampled chickens were of local breeds and several of them mixed with other birds and animals. Out of the 378 chickens examined for the presence of ND, 186 of these were bought from markets, whereas the remaining 192 were bought from breeders before they being raised in households.
Sample and data collection
Blood (3 mL) was collected from the wing vein of the chicken using a sterile syringe. The collected whole blood was allowed to clot at room temperature (25°C) within the syringe and the obtained sera were stored at −20°C. For laboratory analysis, samples were transported to the Department of Poultry at the Central Veterinary Research Laboratory (CVRL), Soba, Khartoum. Blood samples were collected from investigated chickens in Baiad, Sougoh, and Alnuhoud in Alnuhoud locality and Alleait, Alnowara, and Geibaish in Geibaish locality in West Kordofan State in Sudan (Figure-1 and Table-1). Backyard chicken information was collected from villagers in all selected areas using a predesigned questionnaire. Information such as the date of sampling, owner name, location of the flock (village and locality), age of chicken, source of chicken, housing type, presence of other birds, contact with neighboring poultry and wild birds, reason for raising backyard chickens, chicken mortality, and treatment of sick birds were recorded for each bird.
Table-1
Seroprevalence of Newcastle disease virus in 40 flocks of backyard chickens in West Kordofan State.
| Locality | Village | No. of flocks examined | No. of flocks positive | Sero-prevalence | 95% exact binomial CI (%) |
|---|---|---|---|---|---|
| Geibaish | Alnowara | 10 | 6 | 60 | 26.2–87.8 |
| Alleait | 5 | 3 | 60 | 14.7–94.7 | |
| Geibaish | 5 | 1 | 20 | 0.5–71.6 | |
| Total | 20 | 10 | 50 | 27.2–72.8 | |
| Alnuhoud | Baiad | 4 | 2 | 50 | 6.8–93.2 |
| Sougoh | 5 | 2 | 40 | 5.3–85.3 | |
| Alnuhoud | 11 | 4 | 36.4 | 10.9–69.2 | |
| Total | 20 | 8 | 40 | 19.1–64 |
Open in a separate window
CI=Confidence interval
Reference NDV and control sera
The commercial NDV La Sota vaccine strain (reference NDV strain), antiserum against NDV, and negative chicken serum used in this study were kindly provided by the Department of Poultry, CVRL, Soba.
Hemagglutination-inhibition (HI) test
The detection of antibodies and estimation of antibody titers for NDV in chicken sera were determined for each serum sample using the HI test protocol according to the procedure described by the World Organization for Animal Health [5]. The HI titer 2X (log2X) of serum was expressed as the reciprocal of the highest dilution causing complete inhibition of 4 hemagglutination units of the hemagglutinating NDV. Sera with titers ≥24 (log24) were considered positive; the validity of the results was assessed against positive and negative control sera.
Statistical analysis
Data were analyzed using the Statistical Package for the Social Sciences version 20 after data entry using Microsoft Office Excel. Descriptive statistical analysis was first displayed in frequency distribution and cross-tabulation tables. Univariate analysis was performed using the Chi-square for qualitative data, followed by multivariable logistic regression analysis. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the strength of the association between putative risk factors and outcome variables of interest. Variables from univariate analysis with p ≤ 0.2 were included in the multivariable regression and p < 0.05 was considered statistically significant.
Results
Detection of NDV antibodies in backyard chicken sera
Screening of 378 backyard chicken sera using the HI test demonstrated the presence of NDV antibodies in 78 sera (20.6%). All positive birds had a protective level of NDV antibodies due to a previous infection. The obtained HI titers of the positive sera ranged between log24 and log211 with an overall mean titer of log21.5. However, most of the positive sera had titers of log24 (28/378, 7.4%) and log25 (18/378, 4.8%) (Figure-2). Based on the HI titers obtained, positive backyard chicken sera were classified as having low (ranged from log24 to log25), moderate (ranged from log24 to log27), and high (ranged from log24 to log211) titers (Table-2).
Figure-2
Hemagglutination inhibition (HI) test detected Newcastle disease virus antibodies in backyard chickens sera at different HI titers. Sera with HI titers ≥4 were considered as positive (yellow color), negative sera were shown (brown color).
Table-2
Seroprevalence of Newcastle disease in investigated localities in West Kordofan State.
| Locality | Village | No. of chickens examined | No. of chickens positive | Sero-prevalence | 95% exact binomial CI (%) | HI titer | |
|---|---|---|---|---|---|---|---|
| Total | Mean | ||||||
| Geibaish | Alnowara | 50 | 14 | 28 | 16.2–42.5 | 89** | 1.8 |
| Alleait | 50 | 4 | 8 | 2.2–19.2 | 28* | 0.6 | |
| Geibaish | 100 | 33 | 33 | 23.9–43.1 | 247*** | 2.5 | |
| Total | 200 | 51 | 25.5 | 19.6–32.1 | 364 | 1.8 | |
| Alnuhoud | Baiad | 50 | 4 | 8 | 2.2–19.2 | 34* | 0.7 |
| Sougoh | 50 | 5 | 10 | 3.3–21.8 | 35** | 0.7 | |
| Alnuhoud | 78 | 18 | 23.1 | 14.3–34 | 141*** | 1.8 | |
| Total | 178 | 27 | 15.2 | 10.2–21.3 | 210 | 1.2 | |
Open in a separate window
Levels of HI titers:
*=Low (ranged from log24 to log25),
**=Moderate (ranged from log24 to log27),
***=High ranged from log24 to log211). HI=Hemagglutination-inhibition, CI=Confidence interval
Seroprevalence of ND in West Kordofan state
The 378 backyard chickens originated from 40 flocks in Elnuhoud and Geibaish localities in West Kordofan State. Elnuhoud and Alnowara villages had the highest number of examined flocks, 11 and 10, respectively, with five from each of the other investigated villages; Sougoh, Alleait, and Geibaish, and only four flocks from Baiad. Notably, 12.7% (48/378) of the studied backyard chickens were mixed with other birds, most of which were pigeons; 51.1% (193/378) of chickens were kept in open houses as free-ranging.
The flock-level seroprevalence of ND ranged from 20% to 60%, with an overall prevalence of 45% (18/40). All investigated village flocks had positive serum for NDV antibodies, and the highest prevalences of 60% and 50% were recorded in Geibaish and Elnuhoud localities, respectively. There was no significant difference in terms of flock prevalence between the two studied localities (χ2 = 0.404, p = 0.525). The prevalence of each village is presented in Table-1.
Results of the HI test demonstrated 20.6% of overall individual seroprevalence of NDV antibodies among backyard chickens. The highest individual prevalence was demonstrated in Geibaish (33%) and Alnowara (28%) villages. There was a highly significant difference in the seroprevalence of NDV in the examined chickens among different villages of the two localities (χ2 = 24.477, p = 0.0001) (Table-2).
Risk factors affecting the prevalence of ND
All chickens were raised in backyards but had been sourced either from markets or from breeders (186 were from markets, whereas 192 were from breeders). Based on their source, the seroprevalence of NDV was 22.6% (42/186) among chickens from the market and 18.8% (36/192) among those from breeders. The Chi-square test showed no significant difference in seroprevalence between the two sources of chickens (χ2 = 0.847, p = 0.358).
Nearly 80% of the villagers raised backyard chickens for income; however, only 21.4% raised them for family consumption. The seroprevalence of NDV was relatively higher among backyard chickens raised for family consumption (28.4%, 23/81) than those raised for income (18.5%, 55/297). There was a significant difference between ND seropositivity and the purpose of raising backyard chickens (χ2 = 3.791, p = 0.052). Most villagers kept their birds for income compared with family consumption. Notably, chickens raised for income were less infected by NDV compared with those raised for family consumption, indicating the level of care shown by the villagers for the source of their income.
Based on the type of housing, 193 chickens were kept free-ranging, while 185 were kept enclosed. The prevalence of free-ranging chickens was 27.5% (53/193), while only 13.5% (25/185) of chickens were kept in a closed housing. The difference was significant for the types of housing (χ2 = 11.220, p = 0.001).
Of the 378 chickens investigated for NDV infection, only 12.7% were kept with other types of birds. Although the seroprevalence was higher in mixed flocks (27.1%, 13/48) than those with only chickens (19.7%, 65/330), no significant difference in the mean antibody levels was found between the two groups (χ2 = 1.396, p = 0.237).
The way of life in the study area is very simple and it is easy for the family members to observe any contact with neighboring poultry and wild birds. Among the examined chickens, a higher prevalence was recorded in those who came in close contact with neighboring poultry (27.9%, 36/129) and 31.1% (23/74) in chickens that had access to wild birds compared with other groups that had no contact history. Therefore, there was a significant difference (χ2 = 6.324, p = 0.012 and χ2 = 6.131, p = 0.013) between NDV seroprevalence and close contact with neighboring poultry and wild birds, respectively.
Based on our observations concerning their health history, the backyard chickens that experienced mortality due to infectious diseases (61.7%, 66/107) were more likely to develop ND than those without reported deaths (4.4%, 12/271). The Chi-square test revealed a highly significant association between NDV and chicken mortality due to the presence of infectious diseases (χ2 = 153.5, p ≤ 0.001).
The majority (88.9%, 336/378) of the surveyed chickens received treatment when they became sick because of different infectious diseases, in addition to ND, as confirmed by their owners. Univariate analysis demonstrated that there was no significant association between NDV infection and treatment of diseased birds (χ2 = 0.890, p = 0.345). However, ND was more prevalent in chickens without a history of treatment (26.2%, 11/42) compared with other groups that had been treated (19.9%, 67/336). The univariate analysis of potential risk factors for ND in backyard chickens in West Kordofan State is presented in Table-3.
Table-3
Univariate analysis of potential risk factors for Newcastle disease in backyard chickens in West Kordofan State.
| Risk factor | No. of birds examined | No. of positive birds | Prevalence (%) | χ2 | p-value |
|---|---|---|---|---|---|
| Source of chickens | |||||
| Market | 186 | 42 | 22.6 | 0.847 | 0.358 |
| Breeder | 192 | 36 | 18.8 | ||
| Reason for raising chickens | |||||
| Income | 297 | 55 | 18.5 | 3.791 | 0.052 |
| Family consumption | 81 | 23 | 28.4 | ||
| Type of housing | |||||
| Open | 193 | 53 | 27.5 | 11.220 | 0.001 |
| Closed | 185 | 25 | 13.5 | ||
| Presence of other birds | |||||
| Yes | 48 | 13 | 27.1 | 1.396 | 0.237 |
| No | 330 | 65 | 19.7 | ||
| Contact with neighboring poultry | |||||
| Yes | 129 | 36 | 27.9 | 6.324 | 0.012 |
| No | 249 | 42 | 16.9 | ||
| Contact with wild birds | |||||
| Yes | 74 | 23 | 31.1 | 6.131 | 0.013 |
| No | 304 | 55 | 18.1 | ||
| Chickens mortality due to infectious diseases | |||||
| Yes | 107 | 66 | 61.7 | 153.5 | 0.001 |
| No | 271 | 12 | 4.4 | ||
| Treatment of poultry if they are sick | |||||
| Yes | 336 | 67 | 19.9 | 0.890 | 0.345 |
| No | 42 | 11 | 26.2 |
Open in a separate window
Six variables were considered in the final logistic regression model (Table-4) and only “Chicken mortality due to infectious diseases” was found to be positively associated with ND viral infection (OR: 40.4, 95% CI: 18.783–86.826, p ≤ 0.001).
Table-4
Result of multivariable analysis of potential risk factors for Newcastle disease in backyard chickens in West Kordofan State.
| Risk factor | Odds ratio | 95% CI | p-value |
|---|---|---|---|
| Reason for raising chickens | 0.302 | 0.130–0.702 | 0.005 |
| Type of housing | 1.39 | 0.511–3.798 | 0.520 |
| Contact with neighboring poultry | 1.44 | 0.565–3.679 | 0.440 |
| Contact with wild birds | 1.2 | 0.494–2.865 | 0.699 |
| Chickens mortality due to infectious diseases | 40.4 | 18.783–86.826 | 0.001 |
| Presence of other birds | 1.69 | 0.277–1.715 | 0.420 |
Open in a separate window
CI=Confidence interval
Discussion
The results of the recent investigation in six villages (Alnowara, Alleait, Geibaish, Baiad, Sougoh, and Alnuhoud) in Geibaish and Alnuhoud localities of West Kordofan State revealed a relatively high serological prevalence of NDV of 45% (29.3%–61.5% at 95% CI) among the backyard chicken flocks. Alnowara, Alleait, Geibaish, Baiad, Sougoh, and Alnuhoud had flock prevalence of 60%, 60%, 20%, 50%, 40%, and 36.4%, respectively, with no significant difference (χ2 = 0.404, p = 0.525) in antibodies to NDV flock seroprevalence at the locality level. The presence of a high prevalence of NDV antibodies in seropositive flocks may be caused by the circulation of low pathogenic NDV strains producing no clinical signs in these birds, as has been stated previously [17].
Examination of sera from the 378 backyard chickens revealed that 78 sera (20.6%, 16.7%–25.1% at 95% CI) were positive for NDV antibodies with a highly significant difference in ND individual seroprevalence among the different investigated villages. Based on our observations, the high NDV seroprevalence in Geibaish locality and bordering Darfur States may be attributable to the high number of wild birds and poor management practices of traditionally kept backyard chickens compared with those features in Alnuhoud locality bordering North Kordofan State. As there was no history of vaccination against NDV in the study area, the reported seroprevalence in apparently healthy birds was considered as clear evidence of exposure of these chickens to NDV, possibly through contact with infected birds. Positive serology in unvaccinated birds is considered as diagnostic evidence for the presence of ND [18]. Newcastle disease has been reported in traditionally managed village poultry in different areas within the country. In a previous study, serum samples were taken from 910 non-vaccinated birds (843 chickens, 45 pigeons, and 22 ducks) kept under the backyard management system in 14 states of Sudan [15]. Hemagglutination inhibition antibodies against NDV were detected in 41.8% of chickens with a mean antibody titer of log22.75, considering that none of the states investigated were found to be free from NDV antibodies. The Western states reported a disease prevalence of 37.5% in West Darfur, 37.7% in North Kordofan, 38.9% in South Kordofan, and 41.3% in South Darfur; however, in this survey, we detected a much lower individual prevalence (20.6%) of ND in West Kordofan State.
In similar studies, variable seroprevalence values had been reported elsewhere. For instance, 26.8% seroprevalence of NDV antibodies was reported in unvaccinated backyard poultry in Bahi and Njombe districts of Tanzania [19], whereas in Nigeria, 57% of the total serum samples collected were positive for antibodies to NDV [20]. An overall NDV seroprevalence of 30% has been reported in selected districts of Buno Bedele Zone, Ethiopia, [21].
In this study, HI titers of log24 and above were generally considered as positive for antibodies to NDV [22, 23]. In the two localities studied, the HI titers for the positive samples ranged from log24 to log211 with an overall mean titer of log21.5. However, most of the sera had titers of log24 and log25. The higher NDV antibody titers are indicative of recent infection and may be attributed to the fact that natural infection of chickens with NDV produces higher antibody titers than vaccination [23, 24].
In a risk factor investigation, although there was no significant difference in the seroprevalence of ND between the sources of chickens, it was clear that the disease is more prevalent in chickens sourced from the market. This finding is logical as the bird market is an important source of infection where infected birds can simply mix with susceptible ones. Haile et al. [25] recently investigated the role of live chicken markets in the maintenance and spread of ND in the village chickens and proved that apparently healthy appearing birds were reservoirs of velogenic NDV strains that could initiate the endemicity of ND cycles in the village setting due to ease of contact at local open-air markets. Interestingly, chickens raised for income were less infected by NDV compared with those raised for family consumption; this shows that villagers care more about the source of their income.
The infection rate of the disease was 2-fold higher in free-ranging backyard chickens. The free-ranging production system increases the chance of contact with wild birds, and consequently, free-ranging chickens may serve as a threat to wild birds and other poultry and vice versa. Moreover, contact was reported for approximately 34.1% (129/378) and 19.6% (74/378) of the examined backyard chickens with neighboring or wild poultry, respectively, suggesting the spread of ND within village flocks. In this study, contacts with both neighboring poultry and wild birds were considered as risk factors associated with the occurrence of ND among the investigated backyard flocks. This result is consistent with a previous report and confirms that backyard poultry was significantly affected by close contact with wild birds [26].
In this study, mortality was reported for 28.3% of the investigated birds (107/378) because of infectious diseases and ND was more prevalent in chickens with a record of mortality (61.7%). Exposure of traditionally managed backyard chickens to infectious diseases, and therefore mortality, suggested that those birds were kept under inadequate healthcare, which increases the likelihood of contracting diseases resulting in severe economic losses.
Our results indicated that ND was prevalent in the study area throughout the study period. Newcastle disease is reported to occur throughout the year in rural poultry populations in most countries, specifically, those in Africa [27, 28], and the incidence of ND is associated with periods of climatic stress.
Conclusion
This study provides evidence of a relatively high serological flock prevalence of NDV in backyard chickens in West Kordofan State in West Sudan. The bird seroprevalence of ND among the examined unvaccinated chickens could be attributed to different factors: Absence of vaccination, poor management system, contact with wild birds and other poultry, and inadequate healthcare. As almost 80% of the interviewed owners raised chickens for income, it is recommended that chicken owners should be aware of the economic significance of the disease and be educated on biosecurity measures. Future studies should be planned to cover other areas of the country to include a large number of backyard chickens and different types of birds and to consider additional risk factors that may be associated with the disease.
Authors’ Contributions
MAIH: Performed field investigations, sample collection, laboratory work, and data analysis. NAA and NAO: Supervised the study, designed the work, performed data analysis and interpretation, and prepared and finalized the manuscript. MTI: Performed statistical analysis. AMA: Performed laboratory work with MAIH. All authors have read and approved the final manuscript.
Acknowledgments
We are thankful to the staff of the Department of Poultry, Central Veterinary Research Laboratory, Soba, Khartoum, and the Faculty of Veterinary Science, University of West Kordofan, West Kordofan, for their valuable help during sample collection and laboratory experiment. The authors did not receive any funds for this study. We are grateful to Dr. Samahir Galal Ismail Adam, Ministry of Animal Resources, Khartoum, Sudan, for drawing map of the study area.
Competing Interests
The authors declare that they have no competing interests.
Publisher’s Note
Veterinary World remains neutral with regard to jurisdictional claims in published map and institutional affiliation.
References
1. Wong J.T, de Bruyn J, Bagnol B, Grieved H, Lie M, Pym R, Alders R.G. Small-scale poultry and food security in resource-poor settings:A review. Glob. Food Sec. 2017;15:43–52. [Google Scholar]
2. Wilson R.T. An overview of traditional small-scale poultry production in low-income, food-deficit countries. Ann. Agric. Crop Sci. 2021;6(3):1077. [Google Scholar]
3. Khalafalla A.I, Sana A.A, Hassan W, Dwinger R.H, Unger H. Chapter:Village Poultry Production in the Sudan. Leiden, Holland: Backhuys Publishers; 2002. Village poultry production in the Sudan. In:Characterization and Parameters of Family Poultry Production in Africa. [Google Scholar]
4. Emam A.A, Hassan A.M. Economics of egg poultry production in Khartoum State with emphasis on the open-system-Sudan. Afr. J. Agric. Res. 2010;5(18):2491–2496. [Google Scholar]
5. OIE. Newcastle disease (infection with Newcastle disease virus) OIE Manual of Diagnostic Tests and Vaccines for Terrestrial Animals. Official International Epizootic. (7th ed) 2021;3.3.14:555–574. [Google Scholar]
6. Amarasinghe G.K, Ayllón M.A, Bào Y, Basler C.F, Bavari S, Blasdell K.R, Briese T, Brown P.A, Bukreyev A, Balkema-Buschmann A, Buchholz U.J, Chabi-Jesus C, Chandran K, Chiapponi C, Crozier I, de Swart R.L, Dietzgen R.G, Dolnik O, Drexler J.F, Dürrwald R, Kuhn J.H. Taxonomy of the order Mononegavirales:Update 2019. Arch. Virol. 2019;164(7):1967–1980. [PMC free article] [PubMed] [Google Scholar]
7. Rima B, Collins P, Easton A, Fouchier R, Kurath G, Lamb R.A, Lee B, Maisner A, Rota P, Wang L.F. Problems of classification in the family Paramyxoviridae. Arch. Virol. 2018;163(5):1395–1404. [PMC free article] [PubMed] [Google Scholar]
8. Dimitrov K.M, Ramey A.M, Qiu X, Bahl J, Afonso C.L. Temporal, geographic, and host distribution of avian paramyxovirus 1 (newcastle disease virus) Infect. Genet. Evol. 2016;39:22–34. [PubMed] [Google Scholar]
9. Dimitrov K.M, Abolnik C, Afonso C.L, Albina E, Bahl J, Berg M, Briand F. X, Brown I.H, Choi K. S, Chvala I, Diel D.G, Durr P.A, Ferreira H.L, Fusaro A, Gil P, Goujgoulova G.V, Grund C, Hicks J.T, Joannis T.M, Torchetti M.K, Wong F. Updated unified phylogenetic classification system and revised nomenclature for Newcastle disease virus. Infect. Genet. Evol. 2019;74:103917. [PMC free article] [PubMed] [Google Scholar]
10. Karrar G, Mustafa A. Newcastle Disease in the Sudan. Bull. Off. Int. Epizoot. 1964;62:890–896. [Google Scholar]
11. Elmardi N.A, Bakheit M.A, Khalafalla A.I. Phylogenetic analysis of some Newcastle disease virus isolates from the Sudan. Open Vet. J. 2016;6(2):89–97. [PMC free article] [PubMed] [Google Scholar]
12. Diel D.G, da Silva L.H, Liu H, Wang Z, Miller P.J, Afonso C.L. Genetic diversity of avian Paramyxovirus Type 1:Proposal for a unified nomenclature and classification system of Newcastle disease virus genotypes. Infect. Genet. Evol. 2012;12(8):1770–1779. [PubMed] [Google Scholar]
13. Alexander D.J. Newcastle disease. The Gordon memorial lecture. Br. Poult. Sci. 2001;42:5–22. [PubMed] [Google Scholar]
14. Yousif I.A, Berima M.A, Ishag I.A. Evaluation of the Sudanese native chicken production system and major constraints. J. Vet. Med. Anim. Prod. 2015;6(2):127–135. [Google Scholar]
15. Egbal S.A, Khalda A.K, Iman M.E, AlHassan A.M. Serological survey of Newcastle disease and infectious bursal disease in Backyard birds in Sudan. Bull. Anim. Health Prod. Afr. 2012;60(3):273–278. [Google Scholar]
16. Thrusfield M. Veterinary Epidemiology. 3rd ed. Oxford, UK: Blackwell Science Ltd; 2007. [Google Scholar]
17. Alsahami A, Ideris A, Omar A, Ramanoon S.Z, Sadiq M.B. Seroprevalence of Newcastle disease virus in backyard chickens and herd-level risk factors of Newcastle disease in poultry farms in Oman. Int. J. Vet. Sci. Med. 2018;6(2):186–191. [PMC free article] [PubMed] [Google Scholar]
18. Gedara E.A, Alseed H.A, Kammon A.M, Dayhum A.S, Benothman M.A, Al-Garib S.O, Eldaghayes I.M. Seroprevalence and molecular detection of Newcastle disease virus in backyard chickens in Tripoli, Libya. Open Vet. J. 2020;10(1):80–85. [PMC free article] [PubMed] [Google Scholar]
19. Mngumi E.B, Bunuma E. Seroprevalence and risk factors of Newcastle disease virus in local chickens in Njombe and Bahi districts in Tanzania. Trop. Anim. Health Prod. 2022;54(1):53. [PubMed] [Google Scholar]
20. Anzaku S.A, Umoh J.U, Abdu P.A, Kabir J, Bala A. Serological survey of Newcastle disease in free-ranging local chickens in the federal capital territory, Abuja, Nigeria. N. J. Sci. 2017 Article ID 9646138. [Google Scholar]
21. Mamo T, Yimer L. Serological investigation of Newcastle disease in selected districts of Buno Bedelle Zone, Ethiopia. Vet. Med. (Auckl.) 2021;12:253–259. [PMC free article] [PubMed] [Google Scholar]
22. Allan W.H, Gough R.E. A standard haemagglutination-inhibition test for Newcastle disease, a comparison of macro-and micro methods. Vet. Rec. 1974;95:120–123. [PubMed] [Google Scholar]
23. FAO Alexander D.J, Bell J.G, Alders R.G. A Technology Review, Newcastle Disease with special emphasis on its effect on village chickens. Rome, Italy: FAO Animal Production and Health; 2004. p. 161. [Google Scholar]
24. Sinha S.K. Studies on Experimental Epizootiology of Newcastle Disease Virus in Chickens. USA: Ph.D. Thesis, University of Wisconsin; 1975. [Google Scholar]
25. Haile B, Fentie T, Kassa T. The role of live chicken markets as a source of replication and dissemination of Newcastle disease virus in chickens, Northwest Ethiopia. Poult. Sci. 2020;99(11):5415–5421. [PMC free article] [PubMed] [Google Scholar]
26. Brown V.R, Bevins S.N. A review of virulent Newcastle disease viruses in the United States and the role of wild birds in viral persistence and spread. Vet. Res. 2017;48(1):68. [PMC free article] [PubMed] [Google Scholar]
27. sh*ttu I, Joannis T.M, Odaibo G.N, Olaleye O.D. Newcastle disease in Nigeria:Epizootiology and current knowledge of circulating genotypes. Virusdisease. 2016;27(4):329–339. [PMC free article] [PubMed] [Google Scholar]
28. Amoia C.F.A, Nnadi P.A, Ezema C, Couacy-Hymann E. Epidemiology of Newcastle disease in Africa with emphasis on Côte d'Ivoire:A review. Vet. World. 2021;14(7):1727–1740. [PMC free article] [PubMed] [Google Scholar]
Articles from Veterinary World are provided here courtesy of Veterinary World
