A Survey on Salmonella Infection among Chicken Flocks in Jimma Town, Ethiopia

A cross sectional study was conducted between November, 2011 and April, 2012 with the intention to determine the prevalence and risk factors associated with Salmonella infection among chicken flocks in Jimma town, Ethiopia. Management system, sex, season, age and breed of the chicken flocks examined in the study were considered as risk factors and evaluated whether they are associated with Salmonella infection or not. A bacteriological examination was carried out on 384 faecal samples originated from 232 exotic chicken flocks which were kept indoor and 152 local chicken flocks which were free ranging. The faecal samples were enriched with peptone water for 24 hours and then seeded on the selective enrichment media, Rappaport Vassiliadis Soy Broth and incubated at 37°C for 24 hours. Following selective enrichment, 0.1 ml of the pre enriched broth of the various dilutions were streaked aseptically onto Xylose Lysine Desoxycholate (XLD) agar plates and incubated at 37°C for 24 hours. Presumptive identification of Salmonella was done based on morphology and colour of the colonies on the culture media. Final identification and assignment of Salmonella was conducted by employing biochemical tests such indole production, citrate utilization and urease tests. The identification result proved the overall prevalence of Salmonella to be 41.9%. The prevalence of Salmonella infection were found to be higher in indoor chickens (42.7%) than chickens that were kept as free ranging (40.8%) but there was no statistical significant difference (p>0.05) on the prevalence of Salmonella infection in chicken flocks between management systems. The prevalence of Salmonella in female chicken flocks (43.0%) was higher than in male chicken flocks (39.0%) and there was no statistical significant difference (P>0.05) on the prevalence of Salmonella between sexes. The highest prevalence of Salmonella was recorded during spring (47.7%) followed by autumn (39.7%) and the lowest prevalence of Salmonella infection among chicken flocks was seen during winter (36.8%). Statistical analysis of the data showed that there was no statistical significant difference (P>0.05) on the prevalence of Salmonella in chicken flocks among seasons. Layers and cocks were proved to be highly infected with Salmonella (46.2%) followed by broilers (41.3%). The lowest prevalence of Salmonella infection was seen in chickens (40.8%). There was no statistical significant difference (P>0.05) on the prevalence of Salmonella in chicken flocks among ages. The prevalence of Salmonella was proved to be higher in exotic breed chicken flocks (42.7%) than chicken flocks which were kept as free ranging …


INTRODUCTION
Ethiopia did not earn the expected production from Chicken flocks are one of the most important which contributes for the low productivity of sources of livelihood food and income in the world in chicken flocks in Ethiopia is attributed to salmonellosis general and in Ethiopia in particular.But the country, [1].
its chicken flock population.The lion's share 1.962 * Pexp (1-Pexp) n = d2 World Appl.Sci.J., 21 (10): [1415][1416][1417][1418][1419][1420]2013 1416 Salmonella orgamnisms live in the intestinal tracts Study Units and Risk Factors: The study units were of warm and cold blooded animals.Some species are ubiquitous.Other species are specifically adapted to a particular host [2].Salmonellosis is a bacterial disease caused by Gram negative facultative rod shaped bacterium strains of Salmonella which is in the same proteobacterial family as Escherichia coli, the family Enterobacteriaceae, trivially known as "enteric" bacteria.It is a diarrheal disease, known more generically as gastroenteritis.The disease is quite common among chickens, ducks and other poultry species [3].
In order to address the chicken flocks related challenges in production and marketing and to improve the livelihoods and food security of rural and urban households by enhancing the benefits from chicken flocks through appropriate production and marketing extension, it is essential to conduct a research that could generate appropriate technology, which is socially acceptable, environmentally sound and economically feasible [4].
In spite of the aforementioned prevailing situation and the presence of a number of economic losses due to Salmonella in Jimma town, Ethiopia, there is paucity of well documented information on the occurrence of the bacteria in chicken flocks.Therefore, this study was designed to determine the prevalence of Salmonella and risk factors associated with Salmonella infection among chicken flocks in Jimma town, Ethiopia.

Study Area:
The study was conducted in Jimma town of Jimma Zone in Oromia Regional State, Ethiopia.Jimma town is found in Southwestern Ethiopia at the altitude and longitude of 7°40'N 36°50'E at 352 km from Addis Ababa, the capital of Ethiopia.Jimma Zone comprises of 13 Districts and has a population of 2.1 million.Jimma town, the capital of the Zone, has a population of over 100,000.The town has an average temperature of 20°C and a bimodal irregular raining system with an average annual rain fall of 200mm.This irregular raining and temperature fluctuation has a great role for the outbreak of disease in animals and humans [5].

Study Period and Sampling Technique:
The study was carried out between November, 2011 and April 2012.The sampling technique which was employed in the current research was simple random sampling technique.those chicken flocks that were randomly selected from chicken flocks which were kept as indoor (n=232) and free ranging (n=152).Management system (indoor, free ranging), sex (male, female), season (autumn, winter, spring), age (chicken, broiler, layers and cocks) and breed (local, exotic) of the chicken flocks examined in the study were considered as risk factors and evaluated whether they are associated with Salmonella infection or not.Chicken flocks which were kept indoor were exotic breeds and those which were free ranging were local breeds.
Study Design: A cross-sectional study was conducted from October 2011, to April, 2012 to determine the prevalence of Salmonella and risk factors associated with Salmonella infection among chicken flocks in Jimma town, Ethiopia.

Sample Size Determination:
To calculate the total sample size, the following parameters were used: 95% level of confidence interval (CL), 5% desired level of precision and with the assumption of 50% expected prevalence of Salmonella among chicken flocks in Jimma town, the sample sizes were determined using the formula given in Thrusfield [6].
Where, n = Required sample size, P = Expected prevalence, exp d = Desired absolute precision 2 Thus, the sample size was calculated to be 384.

Sample Collectionand Transportation:
Faecal samples were collected from chicken flocks that were kept indoor (n=232) and from chicken flocks that were free ranging (n=152) between November, 2011 and April, 2012.Sterile spatulas were used to collect fresh faecal samples from chicken flocks.Samples were aseptically collected and put into labeled sterile screw capped universal bottles and kept in an icebox containing ice packs.Following aseptic collection samples were immediately transported to Microbiology laboratory, School of Veterinary Medicine, College of Agriculture and Veterinary Medicine, Jimma University, Jimma, Ethiopia for bacteriological isolation and identification.Upon arrival, the samples were stored overnight in a refrigerator at 4°C until analyzed.

Study Methodology RESULT Isolation and Identification of Salmonella: Isolation and identification of Salmonella organisms were carried
Overall Prevalence of Salmonella: The overall prevalence out following the standard guidelines give by ISO-66579-3 of Salmonella among chicken flocks in Jimma [7].
Non-Selective Enrichment: Faecal samples which were chicken flocks (42.7%) when compared to birds which kept for overnight in a refrigerator at 4°C were thawed for were kept as free ranging (40.8%) but there was no 3-5 hours at room temperature.Twenty five grams of each statistical significant difference (P>0.05) on the faecal sample was stirred separately into 225 ml of prevalence of Salmonella among the chicken flocks sterile buffered peptone water in a sterile stomacher bag.examined between management system (Table 1).The pre enriched samples were homogenized in a The prevalence of Salmonella among female chicken stomacher for 2 minutes and incubated aerobically at 37°C flocks (43.0%) was higher than the prevalence of for 24 hours Salmonella infection among male chicken flocks Selective Enrichment: Faecal samples were inoculated (P>0.05) on the prevalence of Salmonella between sexes into Rappaport Vassiliadis Soy Broth and incubated (Table 2).at 37°C for 24 hours, before plating out onto selective The highest prevalence of Salmonella was recorded agar.

Spread on Selective Xylose Lysine Desoxycholate Agar
that there was no statistical significant difference (P>0.05)Plates: Following selective enrichment, 0.1 ml of the pre on the prevalence of Salmonella in chicken flocks among enriched broth of the various dilutions were streaked seasons (Table 3).aseptically onto Xylose Lysine Desoxycholate (XLD) agar Layers and cocks were proved to be highly infected plates and the plates were incubated at 37°C for 24 hours.
with Salmonella (46.2%) followed by broilers (41.3%).Presumed Salmonella colonies were then selected and The lowest prevalence of Salmonella infection was seen subjected for further tests.Data on bacterial growth and in chickens (40.8%).Statistical analysis of the data potential Salmonellae selected were recorded at the time showed that there was no statistical significant difference of reading and verified by further bacteriological (P>0.05) on the prevalence of Salmonella in chicken identification methods at regular intervals.Final flocks among ages (Table 4).identification of Salmonella organisms were done based The prevalence of Salmonella was proved to be on recommended biochemical tests.
40.8% among local breed chicken flocks and 42.7% among Biochemical Tests: Final identification of Salmonella there was no statistical significant difference (P>0.05) on organisms were done based on biochemical tests such as the prevalence of Salmonella among chicken flocks indole production, citrate utilization and urease tests.

Data Management and Analysis:
Microsoft Excel was used for data management and computation of descriptive statistics was conducted using SPSS version 16.0.Descriptive statistics such as percentages, proportions and frequency distributions were applied to compute some of the data.The prevalence of Salmonella was calculated by dividing the number of chicken flocks positive for Salmonella infection by the number of chicken flocks examined.Pearson's chi-square (x ) test at 2 a significant level of 5% and 95% CI was used to measure association between prevalence of Salmonella with management system, sex, season, age and breed of the The prevalence of Salmonella was higher in indoor (39.0%).There was no statistical significant difference winter (36.8%).Statistical analysis of the data showed exotic breed chicken flocks.Analysis of the data showed

Prevalence of Salmonella among Local Chicken Flocks:
Of the total 152 local chicken flocks examined, 40.8% were proved to be infected with Salmonella organism of which 41.4% were females and 38.9% were males.Statistical analysis of the data showed that there was no statistical significant difference (P>0.05) on the prevalence of Salmonella infection among local chicken flocks between sexes (Table 6).
The highest prevalence of Salmonella among local chicken flocks was recorded during spring (45.8%) followed by autumn (40.0%) and winter (34.9%).Statistical analysis of the data showed that there was no statistical significant difference (P>0.05) on the prevalence of Salmonella in local breed chicken flocks among seasons (Table 7).
The prevalence of Salmonella infection among local chick flocks was confirmed to be 41.4%, 40.7% and 40.6% among chickens, broilers and layers and cocks, respectively.There was no statistical significant variation (P>0.05) on the prevalence of Salmonella in local chicken flocks among age groups (Table 8).

Prevalence of Salmonella among Exotic Chicken Flocks:
The prevalence of Salmonella infection among exotic chicken flocks was confirmed to be 44.2%.The prevalence of Salmonella was proved to be higher in female exotic chicken flocks (44.2%) when compared to the prevalence of Salmonella among male exotic chicken flocks (39.1%).There was no statistical significant difference (p>0.05) on the prevalence of Salmonella among exotic chicken flocks between sexes (Table 9).
The seasonal prevalence of Salmonella in exotic 39.1% in males and 44.2% in females.Kang et al. [12] chicken flocks was found to be 39.4%, 36.6% and 50.0%explained that there could not be any sexual impact on the during autumn, winter and spring, respectively.prevalence of Salmonella infection in male and female Statistical analysis of the data showed that there was no poultry.statistical significant difference (P>0.05) in the prevalence The highest prevalence of Salmonella was recorded of Salmonella in exotic breed chicken flocks among during spring (47.7%) followed by autumn (39.7%) and seasons (Table 10).
winter (36.8%).The highest prevalence of Salmonella in The age specific prevalence of Salmonella among local chicken flocks was recorded during spring exotic chicken flocks was confirmed to be 40.4%,(45.8%) followed by autumn (40.0%) and winter (34.9%).40.7% and 45.7% among chickens, broilers and in layers The seasonal prevalence of Salmonella in exotic chicken and cocks, respectively.There was no statistical flocks was found to be 39.4%, 36.6% and 50.0%during significant variation (P>0.05) on the prevalence of autumn, winter and spring, respectively.Similarly higher Salmonella in exotic chicken flocks among age groups prevalence of Salmonella during the rainy season (Table 11).

DISCUSSION
This fact could be justified by the fact that highest level The overall prevalence of Salmonella infection in temperatures because temperature may be the major the current research (41.9%) was higher than that reported factor impacting the survival and proliferation of by Kassaye et al. [8] who reported 8% of Salmonella in Salmonella [13].Hawassa by direct swab plating technique from small Layers and cocks were proved to be highly infected scale chicken flock farms.The different prevalence of with Salmonella (46.2%) followed by broilers (41.3%).Salmonella from chicken flocks found in these reports The lowest prevalence of Salmonella infection was seen could be explained by the different techniques used in in chickens (40.8%).The prevalence of Salmonella these studies, differences in the origin of the samples or infection in local chick flocks was confirmed to be 41.4%, by geographical differences.
40.7% and 40.6% among chickens, broilers and layers and The prevalence of Salmonella was higher in indoor cocks, respectively.The prevalence of Salmonella chicken flocks (42.7%) than chicken flocks which were infection in local chick flocks was confirmed to be 41.4%, kept as free ranging (40.8%).This fact could be best 40.7% and 40.6% among chickens, broilers and layers and justified by the fact that all the chicken flocks which were cocks, respectively.The age specific prevalence of kept indoor were exotic breeds and these breeds do have Salmonella in exotic chicken flocks was confirmed to be lower immunity against Salmonella.laying hens in this study might be attributed with the Among local chicken flocks examined in this study, the reality that layers are physiologically stressed during sex specific prevalence of Salmonella was 38.9% in male egg production and molting which significantly depress and 41.4% in female local chicken flocks.The sex specific the immune response of layers and increase the prevalence of Salmonella in exotic chicken flocks was susceptibility to Salmonella infection [17]. of salmonellosis is seen after periods of high seasonal

Fig. 1 :
Fig. 1: Flow chart of the ISO-6579 protocol for isolation chicken flocks.The results were considered significant and identification of Salmonellla when P<0.05.
been reported in Bangladesh by Sikder et al.[11].

Table 1 :
Overall prevalence of Salmonella among chicken flocks between

Table 9 :
Prevalence of Salmonella among exotic chicken flocks between management systems

Table 2 :
Overall prevalence of Salmonella among chicken flocks between sexes

Table 3 :
Overall prevalence of Salmonella in chicken flocks among seasons

Table 4 :
Overall prevalence of Salmonella in chicken flocks among different age groups

Table 5 :
Overall prevalence of Salmonella in chicken flocks between breeds

Table 6 :
Prevalence of Salmonella among local chicken flocks between sexes

Table 7 :
Prevalence of Salmonella in local chicken flocks among seasons

Table 8 :
Prevalence of Salmonella in local chicken flocks among age groups

Table 10 :
Prevalence of Salmonella in exotic chicken flocks among seasons

Table 11 :
Prevalence of Salmonella in exotic chicken flocks among age groups Besides the poor 40.4%, 40.7% and 45.7% in chickens, broilers and in layers management experienced by the owners exposes birds to and cocks, respectively.The age specific prevalence of numerous potential sources of Salmonella contamination this study in broilers was lower than the 47% prevalence on chicken flocks which were kept indoor [9].Even if the of Salmonella in broilers reported by Uyttendaele et al. potential exists for increased bacterial contamination on [14] in Belgium and the 74% prevalence of Salmonella in free ranging chicken flocks due to easier access to broilers reported by Mario [15] in Mexico poultry farms.transmitting vectors, such as birds, rodents, insects Lower prevalence of Salmonella among chicken flocks and/or wild animals local breeds are resistant to (11.1%) were recorded from Ethiopia by Endrias and pathogenic organisms to develop infection [10].Poppe [16].The prevalence Salmonella infection was The sex specific prevalence of Salmonella among increased with the increase in age.Salmonella infection chicken flocks in Jimma town, Ethiopia was known to be was found highest (30.76%) at 39 weeks of age and lowest 41.9% in both females males.The current finding on the (13.33%) at 32 weeks of age in the report by Sikder et al., prevalence of Salmonella infection was in agreement with [11].Sikder et al. [11] who reported 40.5% and 41% prevalence The higher prevalence of Salmonella infection in of Salmonella among chicken flocks in Bangladish.