The objective of this study was to (1) estimate frequencies of Salmonella enterica in growing pigs and (2) investigate farmers' perception and practices towards pig farming in Central Department, Paraguay. Twelve out of 19 districts in the department were selected and 33 farms with growers in the selected districts were recruited. Questionnaire interviews for each study farm, in combination with faecal sample collections (n = 30 per farm), which were microbiologic ally examined and visual inspection of pig production facilities were performed between March and November 2009. A questionnaire was designed to obtain basic information of a farm such as the number of pigs owned and some selected farming management practices. Faecal samples were used for Salmonella isolation, using buffered peptone water to have salmonellae pre-enriched, followed by xylose lysine tergitol 4 agar and brilliant green sulfapyridine agar. Suspect colonies were bio chemically tested by triple sugar iron agar in combination with lysine iron agar to confirm the identity. The true frequency probability and associated 95% Bayesian credible intervals (95% BCI) were computed via the Gibbs sampler, a Markov chain Monte Carlo technique. Overall, 18% (95% BCI: 8-31%) of the tested 1000 faecal samples were classified as positive for Salmonella enterica. All the study farms had at least one positive sample for Salmonella enterica (frequency range: 3-60%). Apparent prevalence at farm-level was therefore 100% (one-sided 97.5% confidence limit: 89%). Twenty-eight different serovars for Salmonella enterica were found. Based on increase the number of study districts, farms as well as animals in combination with improvement of sampling methods, possible spatial differences and risk factors/indicators should be clarified by further investigations.Facultad de Ciencias Veterinaria

Alvarez, M.

Cardozo, L.

Copes, Julio Alberto

Gimenez, G.

Leotta, Gerardo Aníbal

Lopez, D.

Nuñez, L.

Suzuki, Kuniaki

Weiler, N.

Zarate, N.

Research Journal of Microbiology

English

Servicio de Difusión de la Creación Intelectual

Research Journal of Microbiology 6 (2): 159-165, 2011 ISSN 1816-4935 / DOI: 10.3923/jm.2011.159.165 © 2011 Academic Journals Inc.Frequencies of Salmonella entérica in Growing Pigs in Paraguay1J. Copes, 1G. Leotta, 2L. Cardozo, 2G. Giménez, 2L. Nuñez, 2,3N. Zarate, 2D. López, 3N. Weiler, 3M. Alvarez and 1K. SuzukiCátedra de Tecnología y Sanidad de los Alimentos, Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata, Argentina2Cátedra de Microbiología, Facultad de Ciencias Veterinarias, Universidad Nacional de Asunción, Paraguay departamento de Bacteriología y Micología, Laboratorio Central de Salud Púbbca, Ministerio de Salud Púbbca y Bienestar Social, ParaguayCorresponding Author: K  Suzuki, Provetsur, Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata, La Plata, B1900AVW, Argentina Tel/Fax: +54 221 425 3276ABSTRACTThe objective of this study was to (1) estímate frequencies of Salmonella entérica in growing pigs and (2) investígate farmers’ perception and practices towards pig farming in Central Department, Paraguay. Twelve out of 19 districts in the department were selected and 33 farms with growers in the selected districts were recruited. Questionnaire interviews for each study farm, in combination with faecal sampie collections (n = 30 per farm), which were microbiologically examined and visual inspection of pig production facilities were performed between March and November 2009. A questionnaire was designed to obtain basic information of a farm such as the number of pigs owned and some selected farming management practices. Faecal samples were used for Salmonella isolation, using buffered peptone water to have salmonellae pre-enriched, followed by xylose lysine tergitol 4 agar and brilliant green sulfapyridine agar. Suspect colonies were biochemically tested by triple sugar iron agar in combination with lysine iron agar to confirm the identity. The true frequency probability and associated 95% Bayesian credible intervals (95% BCI) were computed via the Gibbs sampler, a Markov chain Monte Cario technique. Overall, 18% (95% BCI: 8-31%) of the tested 1000 faecal samples were classified as positive for Salmonella entérica. All the study farms had at least one positive sampie for Salmonella entérica (frequency range: 3-60%). Apparent prevalence at farm-level was therefore 100% (one-sided 97.5% confidence limit: 89%). Twenty-eight different serovars for Salmonella entérica were found. Based on increase the number of study districts, farms as well as animáis in combination with improvement of sampling methods, possible spatial differences and risk factors/indicators should be clarified by further investigations.Key words: Growers, salmonellosis, serovar, South America, swine INTRODUCTIONSalmonellosis is seen worldwide and in all animáis (Ayana and Surekha, 2008). The incidence has increased with the intensification of livestock production (Malkawi and Gharaibeh, 2004). The clinically normal carrier animal is a serious problem in all host species (Mohammad et al., 2006). The disease is caused by many species of salmonellae and characterized clinically by one or more of three major syndromes; septicemia, acute enteritis and chronic enteritis (Asghar et al., 2002).159Res. J. Microbiol., 6 (2): 159-165, 2011Chronic enteritis may develop in growing pigs (Mohammad et al., 2006). The incidence of human salmonellosis has increased in recent years and animáis have been implicated as the main reservoir (Owlia et al., 2007). Transmission to humans occurs via polluted drinking water and foods; pork meat is one of particularly important sources of infection (Wales et al., 2009). Faeces of infected animáis can contamínate feed and water, fresh and processed meats from slaughterhouses (Frendergast et al., 2008). The organisms may remain alive for months in wet, warm are as such as in feeder pig barns or in water dugouts (Owlia et al., 2007). Wildlife such as rodents are also sources of infection (Prendergast et al., 2008; Wales et al., 2009). The prevalence of infection differs amongst species and countries and is much higher than the incidence of clinical disease, which is frequently caused by stressful situations such as sudden deprivation of feed, parturition, drought, crowding, transportation and the administration of some drugs (Asghar et al., 2002; Prendergast et al., 2008; Wales et al., 2009). In Paraguay, field investigations to estímate frequencies of Salmonella entérica in pig populations were not previously implemented, to the best of the authors’ knowledge. The objective of this study was to (1) estímate frequencies of Salmonella entérica in growing pigs and (2) investígate farmers’ perception and practices towards pig farming in Central Department, Paraguay.MATERIALS AND METHODSThis study was conducted between March and November 2009. Paraguay is located in the centre of South America and consists of 17 departments and one capital district. Paraguay has a pig population of 1.7 million and a pork meat production of 168,000 tonnes per year (FAO, 2010). The study area Central Department has 19 districts. Twelve out of the 19 districts were selected and 33 farms growing pigs in the selected districts were recruited. The required sampie size of 1000 in total from a pig population of 1.7 million was sufficient to obtain a 95% Confidence Interval (CI) with a desired precisión of ±3% when the estimated frequency was 50% (Hintze, 2008). The number of faecal samples of 30 at each farm was assigned by available financial, human and material means. The field study consisted of data collection through questionnaire interviews for each study farm, in combination with faecal sampie collections and visual inspection of pig production facilities to find room of improvement. A questionnaire was designed to obtain basic information of a farm such as the number of pigs owned, some selected farming practices and farmers’ perception for pig farming. Faecal samples were used for diagnostic tests. For Salmonella isolation, buffered peptone water was used to have salmonellae pre-enriched, followed by use of xylose lysine tergitol 4 agar (XLT4) and brilliant green sulfapyridine agar (BGS). Suspect colonies were biochemically tested by Triple Sugar Iron (TSI) agar in combination with Lysine Iron Agar (LIA) to confirm the identity, according to the USDA and OIE's recommendations (FSIS-USDA, 2008; OIE, 2009). Data were entered into a database using the Base in the OpenOffice.org software versión 3.2.1 (Sun Microsystems, Santa Clara, CA, USA). A random effects hierarchical model was fitted at the first lev el using Bayesian methods which facilítate the estimation procedure. The number of test positive samples for individual study district were modelled as a binary response variable with True Frequency (TF) probability pi:r¡ ~ Binomial (p,, ri )At the second lev el of the hierarchy, the model was to assume that percentage of test positive (apparent frequency; AF) were alike in some way. This was equal to specifying a random effects model for the TF probability p¿ as follows. They were assumed to be drawn from a common Normal population distribution:160Res. J. Microbiol, 6(2): 159-165, 2011logit (Pi) = bib¡ ~ Normal (p,x)The TF probability and associated 95% Bayesian credible intervals (95% BCI) were computed via the Gibbs sampler, a Markov Chain Monte Cario (MCMC) technique, which was implemented using WinBUGS software (Lunn et al., 2000). The exponential of these TF probabilities was taken to obtain overall frequency estimates (Freq) and their 95% BCIs:Freq =exp (p) (1+exp (p))p ~Normal (0.0, 1.0E-6)Results presented here were based on múltiple runs of length 100,000 following a burn—in of 10,000 iterations to achieve convergence.RESULTSTwelve different districts were selected (Fig. 1) and 33 farms were recruited (median number of the farms per district: two, range: one to eight). The study farms had 10,619 pigs in total at the visit (equivalent to 0.6% of the total pig population in Paraguay). The number of pigs reared variedFig. 1: A map showing the districts visited, for the field study of Salmonella entérica in growing pigs, in all the 19 administrative districts of Central Department, Paraguay161Res. J. MicrobioL, 6 (2); 159-165, 2011between the study farms frange: 140-500, median: 345). Estimated median body weight at shipment for slaughter was 60 kg (range: 45-75 kg). By visual inspection, 42% of the farms were found room for improvement in production facilities or not installing corred facilities. Forty-five percent of them had an incomplete sanitary plan for pig production or not having any plan. Twelve and three percent of them did not implement appropriate feed and water control and pest control, respectively. Half of them had an incomplete disinfection plan for the facilities or not having any plan. Twenty-four percent of them fed pigs leftover meáis. Thirty-three and 20% of them owned animáis other than pigs and let them free, respectively. Forty-five percent of them responded that their pigs showed possible symptoms causedby Saimonella infection in the last six months. Thirty percent of them gave medical treatment (e.g., antibiotics) to sick pigs. Thirty percent of them also experienced death of the sick pigs during the same period. In total 1000 different faecal sampies randomly collected from the study pigs, on the basis of different sampie sizes per district (range: 30-250, median: 60), were microbiologically examined. All the study farms had at least one positive sampie for Saimonella entérica (frequency range: 3-60%). Apparent prevalence at farm-level was therefore 100% (one-sided 97.5% confidence limit: 89%). Table 1 shows estimated frequencies of Saimonella entérica in study pigs. With regard to adjusted frequencies, all AF point estimates were well within the Bayesian credible intervals. TF point estimates varied between districts (range: 5-57%). O ver all, 18% (95% BCI: 8-31%) of the tested 1000 faecal samples were classified as positive for Saimonella entérica. Twenty-eight different serovars for Saimonella entérica were found. The most predominant serovar was S. typhimurium, followed by S. schwarzengrund and S. derby. Table 2 represents observed frequencies of predominant serovars for Saimonella entérica identified in the 1000 samples. Serovars with frequency of less than 0.5% inelude S. adamstua, S. javiana, S. mbandaka, S. bredeney, S. infantis, S. newport, S. albany, S. enteritidis, S. give, S. livingstone, S. sandiego, S. senftenberg, S. tennessee and S. westhampton in descending order of frequency. Besides Saimonella sp., finds frequency of 3.1% (95% CI: 2.1-4.4%).Table 1: Estimated frequencies of Saimonella entérica in growing pigs in Central Department, ParaguayFrequencies (%)95% BCIDistrict n AF TF Lower UpperAreguá 90 8 8 4 15Capiatá 250 20 20 15 25Itá 60 23 23 14 34Limpio 90 4 5 2 11Luque 60 3 5 1 11Nueva Italia 30 7 9 2 20San Lorenzo 90 14 15 8 22Tablada 210 24 24 18 30Thompson 30 60 57 38 72Villa Elisa 30 37 34 20 51Viüeta 30 53 50 33 67Ypané 30 10 11 3 23n: No of faecal samples, AF: Apparent frequency, TF: True frequency, 95% BCI: Bayesian credible interval162Res. J. Microbiol., 6 (2): 159-165, 2011Table 2: Frequencies of predominant serovars for Salmonella entérica identified in growing pigs in Central Department, Paraguay(n = 1000)Serovar Frequencies (%)95% CI Lower UpperTyphimuriuin 3.1 2.1 4.4Se hwar z engrund 2.5 1.6 3.7Derby 2.1 1.3 3.2Anatum 1.3 0.7 2.2Cerro 1.3 0.7 2.2Stanley 1.0 0.5 1.8Rissen 0.7 0.3 1.4Saintpaul 0.7 0.3 1.4London 0.5 0.2 1.2DISCUSSIONThe results presented here constitute the first departmental-wide survey carried out to estímate frequencies of Salmonella entérica in growing1 pigs in Paraguay. In summary, during the period between March and November 2009, the observed true frequencies at animaldevel (5-57%) and apparent prevalence at farm-level (100%) in this study was similar to that reported by other authors in countries where Salmonella entérica infection is existed (Futagawa-Saito et al., 2008; Kishima et al., 2008; Merialdi et al., 2008; O’Connor et al., 2008; Dorn-In et al., 2009; Garcia-Feliz et al., 2009; Schwarz et al., 2009; Kim et al., 2010). In other countries in South America where Paraguay is located, pigs in Brazil had seroprevalence against Salmonella entérica of 74-83% at slaughterhouses (Schwarz et al., 2009). Other authors reported seroprevalence of Salmonella sp. of 38% in Korea (Kim et al., 2010) and 94-100% at herd-level in Italy (Merialdi et al., 2008). Others ais o reported prevalence of Salmonella entérica using faecal s ampies, such as 3% at animal-level and 36% at farm-level in Japan (Futagawa-Saito et al., 2008), 3% at animal-level and 22% at farm-level ais o in Japan (Kishima et al., 2008), 63% at animal-level in Thailand (Dorn-In et al., 2009) and 100% at farm-level in 232 farms in Spain (Garcia-Feliz et al., 2009). O’Connor et al. (2008) reviewed farming management practices and characteristics associated with Salmonella prevalence in swine herds. The authors performed a questionnaire survey in this study to find a relationship between the positivity of Salmonella entérica at farm-level as outcome and such management practices as possible predictors using a logistic regression analysis, which failed due to the 100% prevalence at the level. Current sampling methods couldbe rise the uncertainty about the results of laboratory diagnostic tests. Rectal faecal sampies collected from individually identified pigs randomly selected will give us more precise information. Based on increase the number of study districts, farms as well as animáis in combination with improvement of sampling methods, possible spatial differences and risk factors/indicators should be clarified by further investigations.ACKNOWLEDGMENTSThis study was carried out as part of the project for the capacity development for impro vement of livestock hygiene in the Southern part of South America through regional cooperation [commonly known as: Broyecto de desarrollo professional continuo para los veterinarios del Sur (BROVETSUR)], fundedby the Japan International Cooperation Agency.163Res. J. MicrobioL, 6 (2); 159-165, 2011REFERENCESAsghar, U., Noor-us-Saba, A. Samad and A.A. Qazilbash, 2002. Identification, characterization and antibiotic susceptibility of salmoneda and Shigella species isolated from blood and stool sampies of patients visiting N. I. H, Islamabad. J. Med. Sci., 2: 85-88.Ayana, N. and K. Surekha, 2008. Antimicrobial susceptibility pattern and characterization of ciprofloxacin resistant Salmonella entérica serovar typhi isolates in Kerala, South India. Res. J. Microbiol., 3: 654-660.Dorn-In, S., R. Fries, P. Padungtod, M.N. Kyule and M.P.O. Baumann et al., 2009. A cross-sectional study of Salmonella in pre-slaughter pigs in a production compartment of northern Thailand. Prev. Vet. Med., 88: 15-23.FAO, 2010. FAOSTAT. Food and Agriculture Organization of the United Nations, Rome, Italy.FSIS-USDA, 2008. Isolation and Identification of Salmonella from Meat, Poultry and Egg Products. United States Department of Agriculture, Athens, GA.Futagawa-Saito, K., S. Hiratsuka, M. Kamibeppu, T. Hirosawa, K. Oyabu and T. Fukuyasu, 2008. Salmonella in healthy pigs: Prevalence, serotype diversity and antimicrobial resistance observed during 1998-1999 and 2004-2005 in Japan. Epidemiol. Infect., 136: 1118-1123.Garcia-Feliz, C., A. Carvajal, J.A. Collazos and P. Rubio, 2009. Herd-level risk factors for faecal shedding of Salmonella entérica in Spanish fattening pigs. Prev. Vet. Med., 91: 130-136.Hintze, J., 2008. PASS 2008 Software. NCSS, Kaysville, UT, USA.Kim, Y.H., Kwon, I.K. and J.H. Han, 2010. Serop revalen ce of swine Salmonellosis in Korean swine herds. Korean J. Food Sci. Anim. Resour., 30: 62-65.Kishima, M., I. Uchida, T. Namimatsu, T. Osumi and S. Takahashi et al., 2008. Nationwide surveillance of Salmonella in the faeces of pigs in Japan. Zoonoses Public Health, 55: 139-144.Lunn, D.J., A. Thomas, N. Best and D. Spiegelhalter, 2000. WinBUGS - a Bayesian modelling framework: Concepts, structure and extensibility. Stat. Comput., 10: 325-337.Malkawi, H.I. and R. Gharaibeh, 2004. Rapid and simultaneous Identification of two Salmonella entérica serotypes, enteritidis and typhimurium from chicken and meat products by multiplex PCR. Biotechnology, 3: 44-48.Merialdi, G., G. Barigazzi, P. Bonilauri, C. Tittarelli and M. Bonci, M. D’incau and M. Dottori, 2008. Longitudinal study of Salmonella infection in Italian farrow-to-finish swine herds. Zoonoses Public Health, 55: 222-226.Mohammad, B., H. Mohagheghi Fard Amir and G. Roqiah, 2006. An investigation on contamination of poultries by Salmonella species in Zahedan (South-East Irán) during 2004. Res. J. Microbiol., 1: 463-466.OIE, 2009. Salmonellosis, Manual of Diagnostic Tests and Vaccines for Terrestrial Animáis. OIE Publishers, Paris.O’Connor, A.M., Denagamage, T., Sargeant, J.M., Rajic, A. and J. McKean, 2008. Feeding management practices and feed characteristics associated with Salmonella prevalence in live and slaughtered market-weight finisher swine: A systematic review and summation of evidence from 1950 to 2005. Prev. Vet. Med., 87: 213-228.Owlia, P., S. Leda, O. Fariba, R. Mohamad and B. Shahin, 2007. Evaluation of ceftriaxone releasing from microspheres based on starch against Salmonella sp. Biotechnology, 6: 597-600.164Res. J. Microbiol., 6 (2): 159-165, 2011Prendergast, D.M., S.J. Duggan, S. Fanning, M. Cormican and U. Gonzales-Barron et al., 2008. Prevalence and numbers of Salmonella sp. and enterobacteriaceae on pork cuts in abattoirs in the republic of Ireland. J. Applied Microbiol., 105: 1209-1219.Schwarz, P., J. Calveira, A. Sella, M. Bessa, D. Barcellos and M. Cardoso, 2009. Salmonella entérica1. Isolation and seroprevalence in swines slaughtered in Rio Grande do Sul. Arq. Bras. Med. Vet. Zootec., 61: 1028-1034.Wales, A.D., I.M. McLaren, S. Bedford, J.J. Carrique-Mas, A.J. Cook and R.H. Davies, 2009. Longitudinal survey of the occurrence of Salmonella in pigs and the environment of nucleus breeder and multiplier pig herds in England. Vet. Rec., 165: 648-657.165

Frequencies of Salmonella enterica in growing pigs in Paraguay

SEDICI - Repositorio de la UNLP

Research Journal of Microbiology 6 (2): 159-165, 2011 
ISSN 1816-4935 / DOI: 10.3923/jm.2011.159.165 
© 2011 Academic Journals Inc.
Frequencies of Salmonella entérica in Growing Pigs in Paraguay
1J. Copes, 1G. Leotta, 2L. Cardozo, 2G. Giménez, 2L. Nuñez, 2,3N. Zarate, 2D. López, 
3N. Weiler, 3M. Alvarez and 1K. Suzuki
Cátedra de Tecnología y Sanidad de los Alimentos, Facultad de Ciencias Veterinarias, 
Universidad Nacional de La Plata, Argentina
2Cátedra de Microbiología, Facultad de Ciencias Veterinarias, Universidad Nacional de Asunción, Paraguay 
departamento de Bacteriología y Micología, Laboratorio Central de Salud Púbbca, Ministerio de Salud 
Púbbca y Bienestar Social, Paraguay
Corresponding Author: K  Suzuki, Provetsur, Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata, 
La Plata, B1900AVW, Argentina Tel/Fax: +54 221 425 3276
ABSTRACT
The objective of this study was to (1) estímate frequencies of Salmonella entérica in growing 
pigs and (2) investígate farmers’ perception and practices towards pig farming in Central 
Department, Paraguay. Twelve out of 19 districts in the department were selected and 33 farms 
with growers in the selected districts were recruited. Questionnaire interviews for each study farm, 
in combination with faecal sampie collections (n = 30 per farm), which were microbiologically 
examined and visual inspection of pig production facilities were performed between March and 
November 2009. A questionnaire was designed to obtain basic information of a farm such as the 
number of pigs owned and some selected farming management practices. Faecal samples were used 
for Salmonella isolation, using buffered peptone water to have salmonellae pre-enriched, followed 
by xylose lysine tergitol 4 agar and brilliant green sulfapyridine agar. Suspect colonies were 
biochemically tested by triple sugar iron agar in combination with lysine iron agar to confirm the 
identity. The true frequency probability and associated 95% Bayesian credible intervals (95% BCI) 
were computed via the Gibbs sampler, a Markov chain Monte Cario technique. Overall, 18% 
(95% BCI: 8-31%) of the tested 1000 faecal samples were classified as positive for Salmonella 
entérica. All the study farms had at least one positive sampie for Salmonella entérica (frequency 
range: 3-60%). Apparent prevalence at farm-level was therefore 100% (one-sided 97.5% confidence 
limit: 89%). Twenty-eight different serovars for Salmonella entérica were found. Based on increase 
the number of study districts, farms as well as animáis in combination with improvement of 
sampling methods, possible spatial differences and risk factors/indicators should be clarified by 
further investigations.
Key words: Growers, salmonellosis, serovar, South America, swine 
INTRODUCTION
Salmonellosis is seen worldwide and in all animáis (Ayana and Surekha, 2008). The incidence 
has increased with the intensification of livestock production (Malkawi and Gharaibeh, 2004). The 
clinically normal carrier animal is a serious problem in all host species (Mohammad et al., 2006). 
The disease is caused by many species of salmonellae and characterized clinically by one or more 
of three major syndromes; septicemia, acute enteritis and chronic enteritis (Asghar et al., 2002).
159
Res. J. Microbiol., 6 (2): 159-165, 2011
Chronic enteritis may develop in growing pigs (Mohammad et al., 2006). The incidence of human 
salmonellosis has increased in recent years and animáis have been implicated as the main reservoir 
(Owlia et al., 2007). Transmission to humans occurs via polluted drinking water and foods; pork 
meat is one of particularly important sources of infection (Wales et al., 2009). Faeces of infected 
animáis can contamínate feed and water, fresh and processed meats from slaughterhouses 
(Frendergast et al., 2008). The organisms may remain alive for months in wet, warm are as such 
as in feeder pig barns or in water dugouts (Owlia et al., 2007). Wildlife such as rodents are also 
sources of infection (Prendergast et al., 2008; Wales et al., 2009). The prevalence of infection differs 
amongst species and countries and is much higher than the incidence of clinical disease, which is 
frequently caused by stressful situations such as sudden deprivation of feed, parturition, 
drought, crowding, transportation and the administration of some drugs (Asghar et al., 2002; 
Prendergast et al., 2008; Wales et al., 2009). In Paraguay, field investigations to estímate 
frequencies of Salmonella entérica in pig populations were not previously implemented, to the best 
of the authors’ knowledge. The objective of this study was to (1) estímate frequencies of Salmonella 
entérica in growing pigs and (2) investígate farmers’ perception and practices towards pig farming 
in Central Department, Paraguay.
MATERIALS AND METHODS
This study was conducted between March and November 2009. Paraguay is located in the 
centre of South America and consists of 17 departments and one capital district. Paraguay has a 
pig population of 1.7 million and a pork meat production of 168,000 tonnes per year (FAO, 2010). 
The study area Central Department has 19 districts. Twelve out of the 19 districts were selected and 
33 farms growing pigs in the selected districts were recruited. The required sampie size of 1000 in 
total from a pig population of 1.7 million was sufficient to obtain a 95% Confidence Interval (CI) 
with a desired precisión of ±3% when the estimated frequency was 50% (Hintze, 2008). The 
number of faecal samples of 30 at each farm was assigned by available financial, human and 
material means. The field study consisted of data collection through questionnaire interviews for 
each study farm, in combination with faecal sampie collections and visual inspection of pig 
production facilities to find room of improvement. A questionnaire was designed to obtain basic 
information of a farm such as the number of pigs owned, some selected farming practices and 
farmers’ perception for pig farming. Faecal samples were used for diagnostic tests. For Salmonella 
isolation, buffered peptone water was used to have salmonellae pre-enriched, followed by use of 
xylose lysine tergitol 4 agar (XLT4) and brilliant green sulfapyridine agar (BGS). Suspect colonies 
were biochemically tested by Triple Sugar Iron (TSI) agar in combination with Lysine Iron Agar 
(LIA) to confirm the identity, according to the USDA and OIE's recommendations (FSIS-USDA, 
2008; OIE, 2009). Data were entered into a database using the Base in the OpenOffice.org software 
versión 3.2.1 (Sun Microsystems, Santa Clara, CA, USA). A random effects hierarchical model was 
fitted at the first lev el using Bayesian methods which facilítate the estimation procedure. The 
number of test positive samples for individual study district were modelled as a binary response 
variable with True Frequency (TF) probability pi:
r¡ ~ Binomial (p,, ri )
At the second lev el of the hierarchy, the model was to assume that percentage of test positive 
(apparent frequency; AF) were alike in some way. This was equal to specifying a random effects 
model for the TF probability p¿ as follows. They were assumed to be drawn from a common Normal 
population distribution:
160
Res. J. Microbiol, 6(2): 159-165, 2011
logit (Pi) = bi
b¡ ~ Normal (p,x)
The TF probability and associated 95% Bayesian credible intervals (95% BCI) were computed 
via the Gibbs sampler, a Markov Chain Monte Cario (MCMC) technique, which was implemented 
using WinBUGS software (Lunn et al., 2000). The exponential of these TF probabilities was taken 
to obtain overall frequency estimates (Freq) and their 95% BCIs:
Freq =
exp (p) 
(1+exp (p))
p ~Normal (0.0, 1.0E-6)
Results presented here were based on múltiple runs of length 100,000 following a burn—in of 
10,000 iterations to achieve convergence.
RESULTS
Twelve different districts were selected (Fig. 1) and 33 farms were recruited (median number 
of the farms per district: two, range: one to eight). The study farms had 10,619 pigs in total at the 
visit (equivalent to 0.6% of the total pig population in Paraguay). The number of pigs reared varied
Fig. 1: A map showing the districts visited, for the field study of Salmonella entérica in growing 
pigs, in all the 19 administrative districts of Central Department, Paraguay
161
Res. J. MicrobioL, 6 (2); 159-165, 2011
between the study farms frange: 140-500, median: 345). Estimated median body weight at 
shipment for slaughter was 60 kg (range: 45-75 kg). By visual inspection, 42% of the farms were 
found room for improvement in production facilities or not installing corred facilities. Forty-five 
percent of them had an incomplete sanitary plan for pig production or not having any plan. Twelve 
and three percent of them did not implement appropriate feed and water control and pest control, 
respectively. Half of them had an incomplete disinfection plan for the facilities or not having any 
plan. Twenty-four percent of them fed pigs leftover meáis. Thirty-three and 20% of them owned 
animáis other than pigs and let them free, respectively. Forty-five percent of them responded that 
their pigs showed possible symptoms causedby Saimonella infection in the last six months. Thirty 
percent of them gave medical treatment (e.g., antibiotics) to sick pigs. Thirty percent of them also 
experienced death of the sick pigs during the same period. In total 1000 different faecal sampies 
randomly collected from the study pigs, on the basis of different sampie sizes per district (range: 
30-250, median: 60), were microbiologically examined. All the study farms had at least one positive 
sampie for Saimonella entérica (frequency range: 3-60%). Apparent prevalence at farm-level was 
therefore 100% (one-sided 97.5% confidence limit: 89%). Table 1 shows estimated frequencies of 
Saimonella entérica in study pigs. With regard to adjusted frequencies, all AF point estimates were 
well within the Bayesian credible intervals. TF point estimates varied between districts (range: 
5-57%). O ver all, 18% (95% BCI: 8-31%) of the tested 1000 faecal samples were classified as positive 
for Saimonella entérica. Twenty-eight different serovars for Saimonella entérica were found. The 
most predominant serovar was S. typhimurium, followed by S. schwarzengrund and S. derby. 
Table 2 represents observed frequencies of predominant serovars for Saimonella entérica identified 
in the 1000 samples. Serovars with frequency of less than 0.5% inelude S. adamstua, S. javiana, 
S. mbandaka, S. bredeney, S. infantis, S. newport, S. albany, S. enteritidis, S. give, 
S. livingstone, S. sandiego, S. senftenberg, S. tennessee and S. westhampton in descending order 
of frequency. Besides Saimonella sp., finds frequency of 3.1% (95% CI: 2.1-4.4%).
Table 1: Estimated frequencies of Saimonella entérica in growing pigs in Central Department, Paraguay
Frequencies (%)
95% BCI
District n AF TF Lower Upper
Areguá 90 8 8 4 15
Capiatá 250 20 20 15 25
Itá 60 23 23 14 34
Limpio 90 4 5 2 11
Luque 60 3 5 1 11
Nueva Italia 30 7 9 2 20
San Lorenzo 90 14 15 8 22
Tablada 210 24 24 18 30
Thompson 30 60 57 38 72
Villa Elisa 30 37 34 20 51
Viüeta 30 53 50 33 67
Ypané 30 10 11 3 23
n: No of faecal samples, AF: Apparent frequency, TF: True frequency, 95% BCI: Bayesian credible interval
162
Res. J. Microbiol., 6 (2): 159-165, 2011
Table 2: Frequencies of predominant serovars for Salmonella entérica identified in growing pigs in Central Department, Paraguay
(n = 1000)
Serovar Frequencies (%)
95% CI 
Lower Upper
Typhimuriuin 3.1 2.1 4.4
Se hwar z engrund 2.5 1.6 3.7
Derby 2.1 1.3 3.2
Anatum 1.3 0.7 2.2
Cerro 1.3 0.7 2.2
Stanley 1.0 0.5 1.8
Rissen 0.7 0.3 1.4
Saintpaul 0.7 0.3 1.4
London 0.5 0.2 1.2
DISCUSSION
The results presented here constitute the first departmental-wide survey carried out to estímate 
frequencies of Salmonella entérica in growing1 pigs in Paraguay. In summary, during the period 
between March and November 2009, the observed true frequencies at animaldevel (5-57%) and 
apparent prevalence at farm-level (100%) in this study was similar to that reported by other 
authors in countries where Salmonella entérica infection is existed (Futagawa-Saito et al., 2008; 
Kishima et al., 2008; Merialdi et al., 2008; O’Connor et al., 2008; Dorn-In et al., 2009; 
Garcia-Feliz et al., 2009; Schwarz et al., 2009; Kim et al., 2010). In other countries in South 
America where Paraguay is located, pigs in Brazil had seroprevalence against Salmonella entérica 
of 74-83% at slaughterhouses (Schwarz et al., 2009). Other authors reported seroprevalence of 
Salmonella sp. of 38% in Korea (Kim et al., 2010) and 94-100% at herd-level in Italy 
(Merialdi et al., 2008). Others ais o reported prevalence of Salmonella entérica using faecal s ampies, 
such as 3% at animal-level and 36% at farm-level in Japan (Futagawa-Saito et al., 2008), 3% at 
animal-level and 22% at farm-level ais o in Japan (Kishima et al., 2008), 63% at animal-level in 
Thailand (Dorn-In et al., 2009) and 100% at farm-level in 232 farms in Spain (Garcia-Feliz et al., 
2009). O’Connor et al. (2008) reviewed farming management practices and characteristics 
associated with Salmonella prevalence in swine herds. The authors performed a questionnaire 
survey in this study to find a relationship between the positivity of Salmonella entérica at 
farm-level as outcome and such management practices as possible predictors using a logistic 
regression analysis, which failed due to the 100% prevalence at the level. Current sampling 
methods couldbe rise the uncertainty about the results of laboratory diagnostic tests. Rectal faecal 
sampies collected from individually identified pigs randomly selected will give us more precise 
information. Based on increase the number of study districts, farms as well as animáis in 
combination with improvement of sampling methods, possible spatial differences and risk 
factors/indicators should be clarified by further investigations.
ACKNOWLEDGMENTS
This study was carried out as part of the project for the capacity development for impro vement 
of livestock hygiene in the Southern part of South America through regional cooperation [commonly 
known as: Broyecto de desarrollo professional continuo para los veterinarios del Sur 
(BROVETSUR)], fundedby the Japan International Cooperation Agency.
163
Res. J. MicrobioL, 6 (2); 159-165, 2011
REFERENCES
Asghar, U., Noor-us-Saba, A. Samad and A.A. Qazilbash, 2002. Identification, characterization and 
antibiotic susceptibility of salmoneda and Shigella species isolated from blood and stool sampies 
of patients visiting N. I. H, Islamabad. J. Med. Sci., 2: 85-88.
Ayana, N. and K. Surekha, 2008. Antimicrobial susceptibility pattern and characterization of 
ciprofloxacin resistant Salmonella entérica serovar typhi isolates in Kerala, South India. Res. 
J. Microbiol., 3: 654-660.
Dorn-In, S., R. Fries, P. Padungtod, M.N. Kyule and M.P.O. Baumann et al., 2009. A 
cross-sectional study of Salmonella in pre-slaughter pigs in a production compartment of 
northern Thailand. Prev. Vet. Med., 88: 15-23.
FAO, 2010. FAOSTAT. Food and Agriculture Organization of the United Nations, Rome, Italy.
FSIS-USDA, 2008. Isolation and Identification of Salmonella from Meat, Poultry and Egg 
Products. United States Department of Agriculture, Athens, GA.
Futagawa-Saito, K., S. Hiratsuka, M. Kamibeppu, T. Hirosawa, K. Oyabu and T. Fukuyasu, 2008. 
Salmonella in healthy pigs: Prevalence, serotype diversity and antimicrobial resistance 
observed during 1998-1999 and 2004-2005 in Japan. Epidemiol. Infect., 136: 1118-1123.
Garcia-Feliz, C., A. Carvajal, J.A. Collazos and P. Rubio, 2009. Herd-level risk factors for faecal 
shedding of Salmonella entérica in Spanish fattening pigs. Prev. Vet. Med., 91: 130-136.
Hintze, J., 2008. PASS 2008 Software. NCSS, Kaysville, UT, USA.
Kim, Y.H., Kwon, I.K. and J.H. Han, 2010. Serop revalen ce of swine Salmonellosis in Korean 
swine herds. Korean J. Food Sci. Anim. Resour., 30: 62-65.
Kishima, M., I. Uchida, T. Namimatsu, T. Osumi and S. Takahashi et al., 2008. Nationwide 
surveillance of Salmonella in the faeces of pigs in Japan. Zoonoses Public Health, 55: 139-144.
Lunn, D.J., A. Thomas, N. Best and D. Spiegelhalter, 2000. WinBUGS - a Bayesian modelling 
framework: Concepts, structure and extensibility. Stat. Comput., 10: 325-337.
Malkawi, H.I. and R. Gharaibeh, 2004. Rapid and simultaneous Identification of two Salmonella 
entérica serotypes, enteritidis and typhimurium from chicken and meat products by multiplex 
PCR. Biotechnology, 3: 44-48.
Merialdi, G., G. Barigazzi, P. Bonilauri, C. Tittarelli and M. Bonci, M. D’incau and M. Dottori, 2008. 
Longitudinal study of Salmonella infection in Italian farrow-to-finish swine herds. Zoonoses 
Public Health, 55: 222-226.
Mohammad, B., H. Mohagheghi Fard Amir and G. Roqiah, 2006. An investigation on 
contamination of poultries by Salmonella species in Zahedan (South-East Irán) during 2004. 
Res. J. Microbiol., 1: 463-466.
OIE, 2009. Salmonellosis, Manual of Diagnostic Tests and Vaccines for Terrestrial Animáis. OIE 
Publishers, Paris.
O’Connor, A.M., Denagamage, T., Sargeant, J.M., Rajic, A. and J. McKean, 2008. Feeding 
management practices and feed characteristics associated with Salmonella prevalence in live 
and slaughtered market-weight finisher swine: A systematic review and summation of evidence 
from 1950 to 2005. Prev. Vet. Med., 87: 213-228.
Owlia, P., S. Leda, O. Fariba, R. Mohamad and B. Shahin, 2007. Evaluation of ceftriaxone 
releasing from microspheres based on starch against Salmonella sp. Biotechnology, 
6: 597-600.
164
Res. J. Microbiol., 6 (2): 159-165, 2011
Prendergast, D.M., S.J. Duggan, S. Fanning, M. Cormican and U. Gonzales-Barron et al., 2008. 
Prevalence and numbers of Salmonella sp. and enterobacteriaceae on pork cuts in abattoirs in 
the republic of Ireland. J. Applied Microbiol., 105: 1209-1219.
Schwarz, P., J. Calveira, A. Sella, M. Bessa, D. Barcellos and M. Cardoso, 2009. Salmonella 
entérica1. Isolation and seroprevalence in swines slaughtered in Rio Grande do Sul. Arq. Bras. 
Med. Vet. Zootec., 61: 1028-1034.
Wales, A.D., I.M. McLaren, S. Bedford, J.J. Carrique-Mas, A.J. Cook and R.H. Davies, 2009. 
Longitudinal survey of the occurrence of Salmonella in pigs and the environment of nucleus 
breeder and multiplier pig herds in England. Vet. Rec., 165: 648-657.
165


http://sedici.unlp.edu.ar/bitstream/handle/10915/84156/Documento_completo.3923_jm.2011.159.165 PDFA.pdf-PDFA.pdf?sequence=1&isAllowed=y

Frequencies of Salmonella enterica in growing pigs in Paraguay

Abstract

Similar works

Full text

Available Versions

Servicio de Difusión de la Creación Intelectual

SEDICI - Repositorio de la UNLP