- Email: [email protected]
Infectious Laryngotracheitis Virus in Commercial and Backyard Chicken Production Systems in Central and South Ethiopia (First report) ILT in Ethiopian Poultry Production
C 2019 Poultry Science Association Inc.
Asamenew Tesfaye,∗,1 Mesfin Sahle,∗ Teshal Sori,† Tadewos Kassa,∗ Abebe Garoma,∗ Tafese Koran,∗ Chala Dima,∗ Chala Guyassa,∗ Hailemariam Hilu,‡ Sintayehu Guta,∗ and Fanose Tadesse† ∗
National Animal Health Diagnostic and Investigation Center (NAHDIC), P.O. Box 04; Collage of Veterinary Medicine and Agriculture (CVMA), P.O. Box 34; and ‡ Ministry of Agriculture (MoA), 62347
†
Primary Audience: Poultry producers, Veterinarians and researchers SUMMARY Infectious laryngotracheitis virus (ILT) affects the respiratory tracts of chickens with profound effects in the world poultry industry. The aims of this study are to determine the prevalence and risk factors associated with ILT. The overall prevalence for ILT was 19.4% of which 13.3% (66/496) and 34.4% (74/215) accounted for commercial and backyard poultry production systems, respectively. The prevalence was significantly different between commercial and backyard poultry production systems (P < 0.05). Study areas, breed, and purpose had no significant effect on the prevalence of ILT in commercial production systems. However, study areas significantly affect (P < 0.05) the prevalence in backyard production systems. The mean antibody titer was significantly higher (P < 0.05) in backyard production system (mean = 1209.9) over commercial production systems (mean = 334.1). As the first report in Ethiopia, this study revealed that ILT is prevalent in the country with a higher prevalence in chickens raised in backyard production systems. This indicates further studies are encouraged to determine the role of backyard chickens in the epidemiology of ILT in Ethiopia and develop vaccine(s) to prevent and control the disease. Key words: backyard, commercial, ILT, prevalence 2019 J. Appl. Poult. Res. 0:1–6 http://dx.doi.org/10.3382/japr/pfz100
DESCRIPTION OF PROBLEM The respiratory viral diseases such as Newcastle Disease, Infectious Bronchitis, Infectious Laryngotracheitis (ILT), Pneumoviral Infections, and Avian Influenza are among diseases that could jeopardize the health status of the 1
Corresponding author: [email protected]
poultry [1]. The Ethiopian poultry industry is growing quickly; however, high mortality and morbidity during production due to diseases are becoming major constraints. The backyard production system is the dominant within Ethiopia, it mainly consists of local chicken breeds. Parent stocks or breeds for commercial poultry farms are imported from different parts of the world such as Netherlands, France, Brazil and
Downloaded from https://academic.oup.com/japr/advance-article-abstract/doi/10.3382/japr/pfz100/5599827 by UMass Amherst Libraries user on 20 October 2019
Infectious Laryngotracheitis Virus in Commercial and Backyard Chicken Production Systems in Central and South Ethiopia (First report) ILT in Ethiopian Poultry Production
JAPR: Research Report
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Table 1. Univariate Analysis for Prevalence of ILT in Commercial and Backyard Production Systems.
Production
No. sampled
No. Positive (%)
F-test
P-value
496 215 711
64(12.9) 74(34.4) 138(19.4)
47.2
0.0001
Commercial Backyard Total
Table 2. Prevalence of ILT Among Different Risk Factors and Univariate Analysis. Variables Commercial Location
Breed
Purpose
Backyard production Location
No. sampled
No. positive
F-test
P-value
Bishoftu Awash Bonga Hawassa Total Cobb 500 Lohmann brown Ross Bovans brown Isa brown Koekoek Total Broiler Layer Duall Total
299 45 51 101 496 111 69 43 122 50 101 496 154 191 151 496
39 (13) 7(16.6) 9(17.6) 11(10.9) 66(13.3) 13(11.7) 6(8.7) 4(9.3) 24(19.7) 8(16.0) 11(10.9) 66(13.3) 17(11.0) 30(15.7) 19(12.6) 66(13.3)
0.517
0.671
1.45
0.202
0.852
0.427
Bishoftu Modjo Awash Bonga Gubre Hawassa Total
72 35 39 42 42 20 215
9(12.5) 6(17.1) 15(38.5) 29(69.0) 16(38.1) 5(25.0) 74(34.4)
South Africa. As poultry production expands and grows within Ethiopia, poor bisecurity has increased the emergence of different poultry viral diseases like infectious Bronchitis, ILT and Infectious Bursal Disease virus. These diseases have little or no previous history in the country. Despite the prevalence, there are no any reports on ILT, most commercial poultry farms in Ethiopia are never allowed to use any types of ILT vaccines. ILT was first described in 1925 and caused by a pneumotropic virus of the family Herpesviridae, subfamily Alphaherpesvirinae, genus Iltovirus. Taxonomically, this virus is classified as a Gallidherpesvirus 1 [2]. It has been reported in many countries where it remains an endemic disease. As such, this survey of flocks, both commercial and backyard poultry production systems will be the first report on the detection of ILT in Ethiopia.
11.6
0.000
Therefore, the aims of this study are to generate baseline data, determine sero-prevalence and determine the associated risk factors for ILT in commercial and backyard chicken production in Ethiopia.
MATERIALS AND METHODS Study Areas Commercial and backyard poultry production systems in central (Bishoftu and Awash) and Hawassa, Wolkite, Bonga from Southern Nations, Nationalities and Peoples’ Region (SNNPR) were surveyed from 2017 November to 2018 October. These production areas are found within different agro-ecologies and have different densities of commercial poultry farms.
Downloaded from https://academic.oup.com/japr/advance-article-abstract/doi/10.3382/japr/pfz100/5599827 by UMass Amherst Libraries user on 20 October 2019
Variable
TESFAYE ET AL.: ILT IN ETHIOPIA
3
Sample Collection
Figure 1. Comparison of mean antibody titer among backyard poultry production systems.
Blood samples of 2–3 ml were collected through puncturing the wing vein using 21 gage needles and kept at room temperature overnight to separate serum samples. Then sera samples were poured into cryovial tubes and transported using an ice box to National Animal Health Diagnose and Investigation center (NAHDIC) and kept at −20◦ C until the laboratory analysis was performed. All chickens were sampled according to international animal care and use guide lines adopted by Animal Research Scientific and Ethical Committee (ARSEC) of NAHDIC. Laboratory Analysis
Figure 2. Comparison of mean antibody titer among backyard production systems.
Study Population The chickens in this study were of existing exotic breeds, cross-breeds and indigenous breeds. The age ranges from chicks to adult birds whose purpose ranged widely from breeders, egg production, and meat production. Moreover, chickens included in this study represented the health of age groups and purpose, were apparently healthy or diseased, and may or may not be vaccinated against ILT in the past. Study Designs and Sample Size Samples were taken from cross-section of farms in different areas. Five commercial farms from Bishoftu (Alema, Elfora, Genesis, Maranata, and Eleri), 2 from Awash (AYMA and SW), 3 from SNNPR (Hawassa, Gubre and Bonga) were sampled. Moreover, in all regions chickens under backyard production systems were certainly unvaccinated against ILT. Chickens from backyard production systems were also
Serology: Standard Quantitative Indirect ELISA kit [3] was used to detect antibodies against ILTV in diluted sera samples (1ul sample:500ul of diluent) according to the manufacturer’s instructions. Test kit was validated and verified before analyzing the samples. Sera sample will be diluted 1: 500 Samples with sample to positive ratio (S/P) value ≤0.3 (Titre ≤611per microliter) and >0.3 (Titre>611 per microliter) were interpreted as Negative and positive respectively. Data Analysis All collected data were coded and entered to excel spread sheet. Descriptive, Univariate and one-way ANOVA analyses were conducted using SPSS [4] The differences were considered statistically significant at P < 0.05.
RESULTS The overall prevalence for ILT was 19.4% of which 13.3% (66/496) and 34.4% (74/215) accounted for commercial and backyard poultry production respectively. The identification
Downloaded from https://academic.oup.com/japr/advance-article-abstract/doi/10.3382/japr/pfz100/5599827 by UMass Amherst Libraries user on 20 October 2019
sampled from markets or villages. From each commercial and backyard poultry production 25 chickens per flock were sampled. Accordingly, a total of 711, of which 496 and 215 chickens were sampled from commercial and traditional poultry production systems, respectively.
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Table 3. Comparison of Mean Antibody Titer (One way ANOVA). Variable Production
Commercial Backyard
No. sampled
Minimum
Maximum
Mean Ab (95% CI)
F test
P-value
496 215
0 0
7822.1 11,927.2
334.1[269, 399.2) 1209.9[917.4,1502.3]
63.6
0.000
and recovery of ILT was significantly different between commercial and backyard poultry production systems (P < 0.05) (Table 1). The overall prevalence of ILT in backyard production systems for 5 of the study areas (Bishoftu, Awash, Bonga, Gubre and Hawassa) was accounted 34.4% (74/215). The highest and lowest prevalence was recorded in backyard production systems found in Bong and Bishoftu areas, respectively. The prevalence was significantly different among backyard production systems [(F4, 215) = 11.6, P < 0.05]. The post hoc analysis indicate the prevalence at Bong significantly differed among other study areas (P < 0.05) (Table 2). The highest and lowest mean antibody titer for ILT in commercial farms was recorded 1371.9 and 89 for farm VII and IX, respectively (Figure 1). In case of backyard production system 2491.6 and 308.9 highest and lowest titer was recorded respectively (Figures 1, 2 and 3). One way ANOVA analysis revealed the mean antibody titer was significantly different between commercial and backyard production systems [(F1, 711) = 63.6, P < 0.05] (Table 3). The mean antibody titer was significantly different for at least one of the commercial farms (F9, 496 = 4.92, P = 0.05). According to post
hoc test, the mean antibody titer for commercial farm VI significantly differedfrom the others (P < 0.05). Similarly, there was a significance difference in mean antibody titer among backyard production farms (F5, 215 = 6, P < 0.05) and particularly the mean antibody titer for backyard production system in Bonga area was higher as compared to other farms (P < 0.05) (Table 2).
DISCUSSION The survey of flocks for the presence of ILT was performed in commercial and backyard chickens in the central and southern part of Ethiopia where there was no history of vaccination against ILT. The present study revealed an overall sero-prevalence of 19.4%. The prevalence in the commercial poultry production system revealed sero-positive birds at a rate of 13.3% (66/496). This finding was in accordance with 20% prevalence in Nigeria [5] and 17.33% in Bangladesh [16]. However, other researchers in Bangladesh found positive flocks at an even higher rate of 81.47% and 92.28% prevalence in Bangladesh [6, 7], 67.55% in Trinidad & Tobago [18] and 42.56% in Turkey [8]. The
Downloaded from https://academic.oup.com/japr/advance-article-abstract/doi/10.3382/japr/pfz100/5599827 by UMass Amherst Libraries user on 20 October 2019
Figure 3. Comparison of antibody titer between commercial and backyard poultry production systems.
TESFAYE ET AL.: ILT IN ETHIOPIA
CONCLUSION AND APPLICATIONS 1. Out of 711 samples 140 (19.4%) were found sero-positive. Of which 13.3% (66/496) and 34.4% (74/215) accounted for commercial
2.
3.
4.
5.
and backyard poultry production, respectively. Location of farms, breed of chickens, and purpose has no effect on the prevalence of ILT. However, in case of backyard production systems location significantly affects the prevalence. The prevalence was significantly higher in backyard chickens than commercial production systems. Since any kind of ILT vaccines are not allowed to be use in Ethiopia, the seroconversion certainly due to field virus exposure. Despite the sero-conversion is found high in both commercial and backyard chicken production systems, further research on virus isolation and molecular characterization is needed. Using inactivated and/or recombinant vaccines in commercial poultry farms are encouraged to avert the impact of ILT.
REFERENCES AND NOTES 1. Beard, C. W. 1998. Avian influenza (fowl plague). In US Animal Health Association, Committee on Foreign Animal Disease. Foreign animal diseases: the gray book. Ed 6. Hosted on University of Georgia. 2. May, H. G., and R. P. Tittsler. 1925. Tracheo laryngotracheitis in poultry. J. Am. Vet. Med. Assoc. 67:229–231. 3. IDvet, Louis Pasture, Grabels, France. 4. IBM Corp. Released 2011. IBM SPSS Statistics for Windows, Version 20.0. IBM Corp, Armonk, NY. 5. Owoade, A. A., M. F. Ducatez, and C. P. Muller. 2006. Seroprevalence of avian influenza virus, infectious bronchitis virus, reovirus, avian pneumovirus, infectious laryngotracheitis virus, and avian leukosis virus in Nigerian poultry. Avian. Dis. 50:222–227. 6. Mohammad, I. U., B. S. Ashim, S. I. Muhammad, D. Shubhagata, S. Nasima, N. R. Ripatun, K. Abul, and M. K. Kazi. 2014. Seroepidemiology of infectious Laryngotracheitis (ILT) in the commercial layer farms of Chittagong District, Bangladesh. J. Anim. Vet. Adv. 6:316–320. 7. Md. Mijanur, R., U. Md. Karim, H. Md. Zakir, R. Md. Mamunur, A. Md Zulfekar, R. Md. Lutfor, A. Mir Rowshan, and R. Md. Mostafizer. 2018. Seroprevalence study of infectious laryngotracheitis virus antibody of commercial layer in Gazipur Districts of Bangladesh. Res. 4:1–6. 8. Brown, J. A., J. Sookhoo, L. Blake, P. Crooks, Z. Mohammed, J. Molawatti-Bisnath, C. V. F. Carrington, and C. A. L. Oura. 2018. Serological evidence for eight globally important poultry viruses in Trinidad & Tobago. Prev. Vet. Med. 149:75–81. 9. Aras, Z., O. Yavuz, and G. G. Sanio˘glu. 2018. Occurrence of infectious laryngotracheitis outbreaks in commercial layer hens detected by ELISA. J. Immunoassay Immunochem. 39:190–195.
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current finding was by far higher than 0.194% prevalence report in Ecuador [9]. Several epidemiologic surveillance studies have implicated backyard flocks as a reservoir for poultry diseases; however, much debate still exists over the risk these small flocks pose [10]. A prevalence of 34.4% (74/215) in backyard poultry production was recorded in this study. The result was in agreement with previous 30% in Belgium and 28% of the Swiss birds were sero-positive [11–13]. However, lower than the prevalence in the Dutch and Swiss studies, 65% and 64% of the fancy breed flocks, respectively, were seropositive for ILTV [11–13] and 77% report Maryland [12]. The prevalence of ILT was quite higher than 12% sero-positivity in Finland [14]. In both production systems, the difference in the prevalence of ILT might be associated with difference in the sensitivity and specificity of the test used and study design used. Moreover, the use of live-attenuated vaccines has been associated with adverse effects such as spreading of vaccine to non-vaccinated chickens, insufficient attenuation, development of latent carriers and even gaining virulence and resulting in outbreaks of vaccinal laryngotracheitis [15]. The significance difference in the prevalence of ILT between production systems (P < 0.05) and mean antibody titer (P < 0.05) in this study might be attributed to a difference in poultry management system and a higher risk of exposure to filed of ILT virus in backyard chickens due to poor biosecurity. This may be the reason why we saw significance difference (P < 0.05) in mean antibody titer in chickens under commercial and backyard production systems. Moreover, the prevalence of ILT in backyard production system also differed significantly (P < 0.05) among locations. This is might be associated with the difference in the density of commercial farms and agro-ecology of the locations. One confirmed that spatial-temporal clustering accounted for higher prevalence of ILT [16].
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pathogens in backyard chicken farms in Finland. Avian. Pathol. 46:166–172. 15. Guy, J. S., and M. Garcia. 2008. Laryngotracheitis. 137–152. In: Diseases of Poultry, 12th edn, Saif, Y. M., A. M. Fadly, J. R. Glisson, L. R. McDougald, L. K. Nolan, and D. E. Swayne. Arres, IA: Blackwell Publishing. 16. Pitesky, M., R. P. Chin, S. Carnaccini, C. G. Sent´ıesCu´e, B. Charlton, P. R. Woolcock, and H. L. Shivaprasad. 2014. Spatial and temporal epidemiology of infectious laryngotracheitis in central California: 2000–2012. Avian. Dis. 58:558–565.
Acknowledgments We are grateful to Yohannes Getnet agent for Ceva Company in Ethiopia, laboratory staffs at NAHDIC and experts from Ministry of agriculture for supporting this research work.
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10. Garrido, A., M. Barrionuevo, I. Santiana-Jara, P. Sandoval, P. Alfonso, and M. Barrera. 2016. Serologic and molecular Survey of avian infectious Laryngotracheitis in Ecuador. Ecuador es calidad: Revista Cient´ıfica Ecuatoriana 3:43–49. 11. Madsen, J. M., N. G. Zimmermann, J. Timmons, and N. L. Tablante. 2013. Prevalence and differentiation of diseases in Maryland backyard flocks. Avian. Dis. 57:587–594. 12. Wunderwald, C., and R. K. Hoop. 2002. Serological monitoring of 40 Swiss fancy breed poultry flocks. Avian. Pathol. 31:157–162. 13. Haesendonck, R., M. Verlinden, G. Devos, T. Michiels, P. Butaye, F. Haesebrouck, F. Pasmans, and A. Martel. 2014. High seroprevalence of respiratory pathogens in hobby poultry. Avian. Dis. 58:623–627. 14. Pohjola, L., N. Tammiranta, C. Ek-Kommonen, T. Soveri, M. L. H¨anninen, A. M. Fredriksson, and A. Huovilainen. 2017. A survey for selected avian viral
Asamenew Tesfaye,∗,1 Mesfin Sahle,∗ Teshal Sori,† Tadewos Kassa,∗ Abebe Garoma,∗ Tafese Koran,∗ Chala Dima,∗ Chala Guyassa,∗ Hailemariam Hilu,‡ Sintayehu Guta,∗ and Fanose Tadesse† ∗
National Animal Health Diagnostic and Investigation Center (NAHDIC), P.O. Box 04; Collage of Veterinary Medicine and Agriculture (CVMA), P.O. Box 34; and ‡ Ministry of Agriculture (MoA), 62347
†
Primary Audience: Poultry producers, Veterinarians and researchers SUMMARY Infectious laryngotracheitis virus (ILT) affects the respiratory tracts of chickens with profound effects in the world poultry industry. The aims of this study are to determine the prevalence and risk factors associated with ILT. The overall prevalence for ILT was 19.4% of which 13.3% (66/496) and 34.4% (74/215) accounted for commercial and backyard poultry production systems, respectively. The prevalence was significantly different between commercial and backyard poultry production systems (P < 0.05). Study areas, breed, and purpose had no significant effect on the prevalence of ILT in commercial production systems. However, study areas significantly affect (P < 0.05) the prevalence in backyard production systems. The mean antibody titer was significantly higher (P < 0.05) in backyard production system (mean = 1209.9) over commercial production systems (mean = 334.1). As the first report in Ethiopia, this study revealed that ILT is prevalent in the country with a higher prevalence in chickens raised in backyard production systems. This indicates further studies are encouraged to determine the role of backyard chickens in the epidemiology of ILT in Ethiopia and develop vaccine(s) to prevent and control the disease. Key words: backyard, commercial, ILT, prevalence 2019 J. Appl. Poult. Res. 0:1–6 http://dx.doi.org/10.3382/japr/pfz100
DESCRIPTION OF PROBLEM The respiratory viral diseases such as Newcastle Disease, Infectious Bronchitis, Infectious Laryngotracheitis (ILT), Pneumoviral Infections, and Avian Influenza are among diseases that could jeopardize the health status of the 1
Corresponding author: [email protected]
poultry [1]. The Ethiopian poultry industry is growing quickly; however, high mortality and morbidity during production due to diseases are becoming major constraints. The backyard production system is the dominant within Ethiopia, it mainly consists of local chicken breeds. Parent stocks or breeds for commercial poultry farms are imported from different parts of the world such as Netherlands, France, Brazil and
Downloaded from https://academic.oup.com/japr/advance-article-abstract/doi/10.3382/japr/pfz100/5599827 by UMass Amherst Libraries user on 20 October 2019
Infectious Laryngotracheitis Virus in Commercial and Backyard Chicken Production Systems in Central and South Ethiopia (First report) ILT in Ethiopian Poultry Production
JAPR: Research Report
2
Table 1. Univariate Analysis for Prevalence of ILT in Commercial and Backyard Production Systems.
Production
No. sampled
No. Positive (%)
F-test
P-value
496 215 711
64(12.9) 74(34.4) 138(19.4)
47.2
0.0001
Commercial Backyard Total
Table 2. Prevalence of ILT Among Different Risk Factors and Univariate Analysis. Variables Commercial Location
Breed
Purpose
Backyard production Location
No. sampled
No. positive
F-test
P-value
Bishoftu Awash Bonga Hawassa Total Cobb 500 Lohmann brown Ross Bovans brown Isa brown Koekoek Total Broiler Layer Duall Total
299 45 51 101 496 111 69 43 122 50 101 496 154 191 151 496
39 (13) 7(16.6) 9(17.6) 11(10.9) 66(13.3) 13(11.7) 6(8.7) 4(9.3) 24(19.7) 8(16.0) 11(10.9) 66(13.3) 17(11.0) 30(15.7) 19(12.6) 66(13.3)
0.517
0.671
1.45
0.202
0.852
0.427
Bishoftu Modjo Awash Bonga Gubre Hawassa Total
72 35 39 42 42 20 215
9(12.5) 6(17.1) 15(38.5) 29(69.0) 16(38.1) 5(25.0) 74(34.4)
South Africa. As poultry production expands and grows within Ethiopia, poor bisecurity has increased the emergence of different poultry viral diseases like infectious Bronchitis, ILT and Infectious Bursal Disease virus. These diseases have little or no previous history in the country. Despite the prevalence, there are no any reports on ILT, most commercial poultry farms in Ethiopia are never allowed to use any types of ILT vaccines. ILT was first described in 1925 and caused by a pneumotropic virus of the family Herpesviridae, subfamily Alphaherpesvirinae, genus Iltovirus. Taxonomically, this virus is classified as a Gallidherpesvirus 1 [2]. It has been reported in many countries where it remains an endemic disease. As such, this survey of flocks, both commercial and backyard poultry production systems will be the first report on the detection of ILT in Ethiopia.
11.6
0.000
Therefore, the aims of this study are to generate baseline data, determine sero-prevalence and determine the associated risk factors for ILT in commercial and backyard chicken production in Ethiopia.
MATERIALS AND METHODS Study Areas Commercial and backyard poultry production systems in central (Bishoftu and Awash) and Hawassa, Wolkite, Bonga from Southern Nations, Nationalities and Peoples’ Region (SNNPR) were surveyed from 2017 November to 2018 October. These production areas are found within different agro-ecologies and have different densities of commercial poultry farms.
Downloaded from https://academic.oup.com/japr/advance-article-abstract/doi/10.3382/japr/pfz100/5599827 by UMass Amherst Libraries user on 20 October 2019
Variable
TESFAYE ET AL.: ILT IN ETHIOPIA
3
Sample Collection
Figure 1. Comparison of mean antibody titer among backyard poultry production systems.
Blood samples of 2–3 ml were collected through puncturing the wing vein using 21 gage needles and kept at room temperature overnight to separate serum samples. Then sera samples were poured into cryovial tubes and transported using an ice box to National Animal Health Diagnose and Investigation center (NAHDIC) and kept at −20◦ C until the laboratory analysis was performed. All chickens were sampled according to international animal care and use guide lines adopted by Animal Research Scientific and Ethical Committee (ARSEC) of NAHDIC. Laboratory Analysis
Figure 2. Comparison of mean antibody titer among backyard production systems.
Study Population The chickens in this study were of existing exotic breeds, cross-breeds and indigenous breeds. The age ranges from chicks to adult birds whose purpose ranged widely from breeders, egg production, and meat production. Moreover, chickens included in this study represented the health of age groups and purpose, were apparently healthy or diseased, and may or may not be vaccinated against ILT in the past. Study Designs and Sample Size Samples were taken from cross-section of farms in different areas. Five commercial farms from Bishoftu (Alema, Elfora, Genesis, Maranata, and Eleri), 2 from Awash (AYMA and SW), 3 from SNNPR (Hawassa, Gubre and Bonga) were sampled. Moreover, in all regions chickens under backyard production systems were certainly unvaccinated against ILT. Chickens from backyard production systems were also
Serology: Standard Quantitative Indirect ELISA kit [3] was used to detect antibodies against ILTV in diluted sera samples (1ul sample:500ul of diluent) according to the manufacturer’s instructions. Test kit was validated and verified before analyzing the samples. Sera sample will be diluted 1: 500 Samples with sample to positive ratio (S/P) value ≤0.3 (Titre ≤611per microliter) and >0.3 (Titre>611 per microliter) were interpreted as Negative and positive respectively. Data Analysis All collected data were coded and entered to excel spread sheet. Descriptive, Univariate and one-way ANOVA analyses were conducted using SPSS [4] The differences were considered statistically significant at P < 0.05.
RESULTS The overall prevalence for ILT was 19.4% of which 13.3% (66/496) and 34.4% (74/215) accounted for commercial and backyard poultry production respectively. The identification
Downloaded from https://academic.oup.com/japr/advance-article-abstract/doi/10.3382/japr/pfz100/5599827 by UMass Amherst Libraries user on 20 October 2019
sampled from markets or villages. From each commercial and backyard poultry production 25 chickens per flock were sampled. Accordingly, a total of 711, of which 496 and 215 chickens were sampled from commercial and traditional poultry production systems, respectively.
JAPR: Research Report
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Table 3. Comparison of Mean Antibody Titer (One way ANOVA). Variable Production
Commercial Backyard
No. sampled
Minimum
Maximum
Mean Ab (95% CI)
F test
P-value
496 215
0 0
7822.1 11,927.2
334.1[269, 399.2) 1209.9[917.4,1502.3]
63.6
0.000
and recovery of ILT was significantly different between commercial and backyard poultry production systems (P < 0.05) (Table 1). The overall prevalence of ILT in backyard production systems for 5 of the study areas (Bishoftu, Awash, Bonga, Gubre and Hawassa) was accounted 34.4% (74/215). The highest and lowest prevalence was recorded in backyard production systems found in Bong and Bishoftu areas, respectively. The prevalence was significantly different among backyard production systems [(F4, 215) = 11.6, P < 0.05]. The post hoc analysis indicate the prevalence at Bong significantly differed among other study areas (P < 0.05) (Table 2). The highest and lowest mean antibody titer for ILT in commercial farms was recorded 1371.9 and 89 for farm VII and IX, respectively (Figure 1). In case of backyard production system 2491.6 and 308.9 highest and lowest titer was recorded respectively (Figures 1, 2 and 3). One way ANOVA analysis revealed the mean antibody titer was significantly different between commercial and backyard production systems [(F1, 711) = 63.6, P < 0.05] (Table 3). The mean antibody titer was significantly different for at least one of the commercial farms (F9, 496 = 4.92, P = 0.05). According to post
hoc test, the mean antibody titer for commercial farm VI significantly differedfrom the others (P < 0.05). Similarly, there was a significance difference in mean antibody titer among backyard production farms (F5, 215 = 6, P < 0.05) and particularly the mean antibody titer for backyard production system in Bonga area was higher as compared to other farms (P < 0.05) (Table 2).
DISCUSSION The survey of flocks for the presence of ILT was performed in commercial and backyard chickens in the central and southern part of Ethiopia where there was no history of vaccination against ILT. The present study revealed an overall sero-prevalence of 19.4%. The prevalence in the commercial poultry production system revealed sero-positive birds at a rate of 13.3% (66/496). This finding was in accordance with 20% prevalence in Nigeria [5] and 17.33% in Bangladesh [16]. However, other researchers in Bangladesh found positive flocks at an even higher rate of 81.47% and 92.28% prevalence in Bangladesh [6, 7], 67.55% in Trinidad & Tobago [18] and 42.56% in Turkey [8]. The
Downloaded from https://academic.oup.com/japr/advance-article-abstract/doi/10.3382/japr/pfz100/5599827 by UMass Amherst Libraries user on 20 October 2019
Figure 3. Comparison of antibody titer between commercial and backyard poultry production systems.
TESFAYE ET AL.: ILT IN ETHIOPIA
CONCLUSION AND APPLICATIONS 1. Out of 711 samples 140 (19.4%) were found sero-positive. Of which 13.3% (66/496) and 34.4% (74/215) accounted for commercial
2.
3.
4.
5.
and backyard poultry production, respectively. Location of farms, breed of chickens, and purpose has no effect on the prevalence of ILT. However, in case of backyard production systems location significantly affects the prevalence. The prevalence was significantly higher in backyard chickens than commercial production systems. Since any kind of ILT vaccines are not allowed to be use in Ethiopia, the seroconversion certainly due to field virus exposure. Despite the sero-conversion is found high in both commercial and backyard chicken production systems, further research on virus isolation and molecular characterization is needed. Using inactivated and/or recombinant vaccines in commercial poultry farms are encouraged to avert the impact of ILT.
REFERENCES AND NOTES 1. Beard, C. W. 1998. Avian influenza (fowl plague). In US Animal Health Association, Committee on Foreign Animal Disease. Foreign animal diseases: the gray book. Ed 6. Hosted on University of Georgia. 2. May, H. G., and R. P. Tittsler. 1925. Tracheo laryngotracheitis in poultry. J. Am. Vet. Med. Assoc. 67:229–231. 3. IDvet, Louis Pasture, Grabels, France. 4. IBM Corp. Released 2011. IBM SPSS Statistics for Windows, Version 20.0. IBM Corp, Armonk, NY. 5. Owoade, A. A., M. F. Ducatez, and C. P. Muller. 2006. Seroprevalence of avian influenza virus, infectious bronchitis virus, reovirus, avian pneumovirus, infectious laryngotracheitis virus, and avian leukosis virus in Nigerian poultry. Avian. Dis. 50:222–227. 6. Mohammad, I. U., B. S. Ashim, S. I. Muhammad, D. Shubhagata, S. Nasima, N. R. Ripatun, K. Abul, and M. K. Kazi. 2014. Seroepidemiology of infectious Laryngotracheitis (ILT) in the commercial layer farms of Chittagong District, Bangladesh. J. Anim. Vet. Adv. 6:316–320. 7. Md. Mijanur, R., U. Md. Karim, H. Md. Zakir, R. Md. Mamunur, A. Md Zulfekar, R. Md. Lutfor, A. Mir Rowshan, and R. Md. Mostafizer. 2018. Seroprevalence study of infectious laryngotracheitis virus antibody of commercial layer in Gazipur Districts of Bangladesh. Res. 4:1–6. 8. Brown, J. A., J. Sookhoo, L. Blake, P. Crooks, Z. Mohammed, J. Molawatti-Bisnath, C. V. F. Carrington, and C. A. L. Oura. 2018. Serological evidence for eight globally important poultry viruses in Trinidad & Tobago. Prev. Vet. Med. 149:75–81. 9. Aras, Z., O. Yavuz, and G. G. Sanio˘glu. 2018. Occurrence of infectious laryngotracheitis outbreaks in commercial layer hens detected by ELISA. J. Immunoassay Immunochem. 39:190–195.
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current finding was by far higher than 0.194% prevalence report in Ecuador [9]. Several epidemiologic surveillance studies have implicated backyard flocks as a reservoir for poultry diseases; however, much debate still exists over the risk these small flocks pose [10]. A prevalence of 34.4% (74/215) in backyard poultry production was recorded in this study. The result was in agreement with previous 30% in Belgium and 28% of the Swiss birds were sero-positive [11–13]. However, lower than the prevalence in the Dutch and Swiss studies, 65% and 64% of the fancy breed flocks, respectively, were seropositive for ILTV [11–13] and 77% report Maryland [12]. The prevalence of ILT was quite higher than 12% sero-positivity in Finland [14]. In both production systems, the difference in the prevalence of ILT might be associated with difference in the sensitivity and specificity of the test used and study design used. Moreover, the use of live-attenuated vaccines has been associated with adverse effects such as spreading of vaccine to non-vaccinated chickens, insufficient attenuation, development of latent carriers and even gaining virulence and resulting in outbreaks of vaccinal laryngotracheitis [15]. The significance difference in the prevalence of ILT between production systems (P < 0.05) and mean antibody titer (P < 0.05) in this study might be attributed to a difference in poultry management system and a higher risk of exposure to filed of ILT virus in backyard chickens due to poor biosecurity. This may be the reason why we saw significance difference (P < 0.05) in mean antibody titer in chickens under commercial and backyard production systems. Moreover, the prevalence of ILT in backyard production system also differed significantly (P < 0.05) among locations. This is might be associated with the difference in the density of commercial farms and agro-ecology of the locations. One confirmed that spatial-temporal clustering accounted for higher prevalence of ILT [16].
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Acknowledgments We are grateful to Yohannes Getnet agent for Ceva Company in Ethiopia, laboratory staffs at NAHDIC and experts from Ministry of agriculture for supporting this research work.
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