Seroepidemiology and occupational and environmental variables for leptospirosis, brucellosis and toxoplasmosis in slaughterhouse workers in the Paraná State, Brazil

Soroepidemiologia e variáveis ocupacionais e ambientais relacionadas à leptospirose, brucelose e toxoplasmose em trabalhadores de frigorífico do Estado do Paraná, Brasil

SEROEPIDEMIOLOGY

Seroepidemiology and occupational and environmental variables for leptospirosis, brucellosis and toxoplasmosis in slaughterhouse workers in the Paraná State, Brazil

Soroepidemiologia e variáveis ocupacionais e ambientais relacionadas à leptospirose, brucelose e toxoplasmose em trabalhadores de frigorífico do Estado do Paraná, Brasil

Daniela Dib Gonçalves^I; Paulo Sérgio Teles^III; Célia Rosimarie dos Reis^I; Fabiana Maria Ruiz Lopes^I; Roberta Lemos Freire^II; Italmar Teodorico Navarro^II; Lucimara Aparecida Alves^IV; Ernest Eckehardt Muller^II; Julio Cesar de Freitas^II

^IPost-Graduation Program, Animal Science, Department at Preventive Veterinarian Medicine (DMVP), Universidade Estadual de Londrina (UEL), Paraná State, Brazil

^IIProfessor at Preventive Veterinarian Medicine Department (DMVP), UEL, Paraná State, Brazil

^IIIVeterinary; Federal Inspection Service in the Northern region of Paraná State, Brazil

^IVBiochemist of the Leptospirosis Laboratory, DMVP, UEL, Paraná State, Brazil

^{Correspondence to}

SUMMARY

Leptospirosis, brucellosis and toxoplasmosis are widely-distributed zoonosis, being the man an accidental participant of their epidemiological chains. The aim of this paper was to make a seroepidemiological report and identify occupational and environmental variables related to these illnesses in 150 workers in a slaughterhouse in the Northern region of Paraná. For the diagnosis of leptospirosis a microscopical seroagglutination test was applied; for brucellosis, the tamponated acidified antigen test and the 2-mercaptoetanol tests were used, and for toxoplasmosis the indirect immunofluorescence reaction test. For each employee an epidemiological survey was filled, which investigated occupational and environmental variables which could be associated with these infections. Positive results for leptospirosis were found in 4.00% of the samples, for brucellosis in 0.66% of samples and toxoplasmosis in 70.00%. From the three diseases researched, only the results for leptospirosis suggest occupational infection.

Keywords:Leptospira spp.; Brucella spp.; Toxoplasma gondii; Occupational diseases; Slaughterhouse workers.

RESUMO

A leptospirose, brucelose e a toxoplasmose são zoonoses de ampla distribuição, sendo o homem participante acidental das suas cadeias epidemiológicas. O objetivo deste trabalho foi realizar levantamento soroepidemiológico e identificar variáveis ocupacionais e ambientais relacionadas a estas enfermidades em 150 trabalhadores de um frigorífico da região Norte do Paraná. Para o diagnóstico de leptospirose foi realizada a prova de soroaglutinação microscópica; para a brucelose, a prova do antígeno acidificado tamponado e do 2-mercaptoetanol e para toxoplasmose, a reação de imunofluorescência indireta. Para cada funcionário foi preenchido um questionário epidemiológico que investigou variáveis ocupacionais e ambientais que poderiam estar associadas a estas infecções. Resultados positivos para leptospirose foram encontrados em 4,00% das amostras, para brucelose em 0,66% das amostras e para toxoplasmose 70,00%. Das três enfermidades pesquisadas, somente os resultados obtidos para leptospirose sugerem infecção de modo ocupacional.

INTRODUCTION

Occupational diseases are those which emerge through apparent or non-apparent signs and can be related, in some way, to activities executed by men in their working environment³.

Leptospirosis, brucellosis and toxoplasmosis are zoonosis of great importance to public health. These diseases affect many groups of workers which keep direct or indirect contact with animals, mainly without adequately using protection measures^12,16,21.

Leptospirosis has cosmopolitan distribution and epidemiological studies have shown a clear predominance of this infection in low-remuneration professions¹⁶. In slaughterhouse workers transmission occurs through contact with urine, blood and organs from infected animals^6,16.

Brucellosis is a disease which can be accidentally transmitted to men. It is widely distributed, having high morbidity and low mortality. In slaughterhouse workers, contact with infection sources can be represented by carcasses and viscera of slaughtered animals and by formation of aerosols present in the slaughtering area¹³.

Toxoplasmosis is also a widely distributed zoonosis which affects animals and men, being one of the parasitary infections of greatest interest to public health²¹. In slaughterhouse workers, the handling of carcasses and viscera from contaminated animals represent risk of infection by Toxoplasma²¹.

The aim of this paper was to prepare a seroepidemiological survey for leptospirosis, brucellosis and toxoplasmosis and identify occupational and environmental variables related to these illnesses in 150 workers of a slaughterhouse in the Northern region of Paraná.

MATERIALS AND METHODS

Sample collection: Blood samples were collected voluntarily from all 150 workers of a slaughterhouse with Federal Inspection Service in the Northern region of Paraná State, Brazil, which slaughtered only bovines until April, 2003 and only swine from May, 2003 onwards. All the workers wore gloves, rubber boots, waterproof aprons, helmets and masks as protection equipment. The blood collection was made by professional nurses from the local Health Center between July and September, 2003. The serological exams were performed in the Leptospirosis Laboratory, Microbiology and Infectious Diseases Laboratory and Zoonosis and Public Health Laboratory of the Department of Preventive Veterinary Medicine (DMVP), Universidade Estadual de Londrina (UEL).

Research tool: To obtain the epidemiological information, each worker was interviewed in order to fill in a questionnaire including information on occupational and environmental variables related to the studied diseases (Tables 1 and 2 and ^{Annex 1}).

Laboratory exams: Each serum sample was divided in three aliquots with equal volume, packed in sterile containers and kept at -20 ºC, for later serological analysis.

In order to detect antibodies against Leptospira spp., all sera were submitted to a microscopical seroagglutination test (SAM), using 22 reference serovars¹⁹. The sera presenting 2+ or more in agglutination in the dilution 1:100 were considered positive, these being diluted progressively until the determination of the maximum positive dilution.

To detect antibodies against Brucella spp., all the samples were submitted to a trial test using the tamponated acidified antigen test (AAT) and as confirmatory test, the 2-mercaptoetanol (2-ME)¹. The AAT test was considered positive when a macroscopic agglutination occurred and on 2-ME when there was the formation of a precipitation with film at the bottom of the tube and a clear supernatant. The sample was only considered positive when it reacted on both serologic tests.

To detect antibodies against T. gondii, the indirect immunofluorescence test (IFI) was performed⁴. All titers presenting completely fluorescent tachyzoite from titer 16 were considered as being positive.

Statistical analysis: The results obtained after the study of variables were submitted to a statistical analysis by the Chi-Square Test (c²) corrected by Yates or Fisher Test, using the statistics program Epi6 version 6.04 (CDC, Atlanta, USA), adopting a 95% trust interval⁹.

RESULTS

From 150 serum samples from slaughterhouse workers analyzed, six (4.00%) were considered positive for leptospirosis, one (0.66%) for brucellosis and 105 (70.00%) for toxoplasmosis. Four samples (66.67%) presented antibodies only against one Leptospira serovar and two samples (33.33%) against two serovars simultaneously. Antibodies against serovars Hardjo, Wolffi and Castellonis were found, with titers between 100 and 400. The positive serum samples were from three employees from the waxing sector, one from the slaughtering room, one who operated machines and one from the animal and packages loading sector. The analysis of the variables indicated the living in an urban zone (p = 0.033) as a risk factor for leptospirosis (Table 1). For brucellosis, only one sample (0.66%) was considered positive, presenting agglutination on the AAT test and titer of 100 on 2-ME. This sample belongs to a worker in the administrative sector. In relation to toxoplasmosis, 105 samples (70.00%) were considered positive to IFI, with titers varying from 16 to 4096. These samples were from 63 workers from the slaughter room, six from the inspection room, five from the cauldron, 27 from general services and four from the office. There were no statistically significant differences among the variables studied and the presence of T. gondii (Table 2).

DISCUSSION

The percentage of workers in the slaughterhouse with positive 1.96% positivity among the employees from the slaughterhouses studied. The different results obtained could have been influenced by the difference in the prevalence of animal leptospirosis in the respective regions and countries studied and could also reflect the periods studied, which leads to higher or lower probabilities of infection in workers who handle carcasses, organs and viscera from animals infected with different serovars of Leptospira. Antibodies against serovars Hardjo, Wolffi and Castellonis with titers between 100 and 400 were found. Similar results in titers and antibodies against serovars were obtained in São Paulo State, Brazil⁶ and Colombia¹⁸. The serological results of this paper suggest these workers had already had contact with some Leptospira serovars and probably been infected for some time. The low serological titers found on the workers, associated with the antibodies detected against the serovars traditionally related to cattle, suggest chronic infections occurring when this slaughterhouse worked only with bovines. In relation to the different sectors of the slaughterhouse, from six positive employees in MAT, three (50.00%) worked in the waxing sector. These results are similar to those found in workers in the same sector in Minas Gerais State, Brazil and S. Paulo State, Brazil, also with 50.00% positivity²⁰. These results confirm this sector as having a high infection risk due to the exposure of organs and viscera of possibly infected animals. Despite leptospirosis being an occupational disease in slaughterhouse workers, the occupational variables analyzed were not significant. However, we should not discharge the possibility of this infection having occurred by other environmental and behavioral situations, once that, even though the variable living in urban zone (p = 0.033) was being considered as a risk factor, the infection could have occurred in the working environment, when the slaughterhouse still killed only bovines.

For brucellosis, one sample was considered positive (0.66%) on both serological tests. This employee worked in administration and did not have direct contact with the animals. However, he had the habit of ingesting non-pasteurized milk, which could indicate the probable source of infection. This low prevalence of human brucellosis among the slaughterhouse workers researched in this paper is probably related with the low prevalence (3.02%) of bovine brucellosis in the State of Paraná, Brazil¹⁰.

The 105 (70.00%) employees who were found positive for toxoplasmosis indicate that the infection by this microorganism is still in high levels when compared to others in the region studied. In Jaguapitã, Paraná State, Brazil¹⁴ the prevalence of human toxoplasmosis is of 66.00% seroreagents. In Londrina, Paraná State, Brazil¹¹ a positivity of 59.50% was detected in employees of a pork sausage factory and in Pato Branco, Paraná State, Brazil⁸ a positivity of 67.20% among workers of slaughterhouses. The titers of antibodies found by IFI in this paper varied from 16 to 4096, with 11 (10.48%) employees presenting titers of 4096, suggesting recent infection by T. gondii. The sector of the slaughterhouse which had most workers affected was the inspection room, with 75.00% positivity, followed by the slaughtering room, with 70.00%. However, there were no statistically significant differences among the sectors, suggesting the infection also occurred in an external environment, not only in the working environment. Despite toxoplasmosis being considered an occupational disease, the occupational variables analyzed in this study were of no significance. Among the three diseases studied in this work, it is possible that the infection of the workers by Leptospira spp. had occupationally occurred, despite the variable living in urban zone (p = 0.033) having been considered as a risk factor, while the infections by Brucella spp.and T. gondii occurred probably outside working environment.

ETHICS COMMITTEE: The present paper was approved by the Ethics in Research Committee of the Hospital Universitário Regional do Norte do Paraná, Decision CEP 142/03.

ACKNOWLEDGEMENTS

The authors would like to thank the workers of the slaughterhouse and the Health Center for their attention and constant collaboration.

3. BRASIL, 2005. http://portal.saude.gov.br/saude/

Received: 20 October 2005

Accepted: 20 February 2006

Project financed by PROPPG/ProDICI-UEL/CAPES

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Annex 1

Publication Dates

• Publication in this collection
  20 July 2006
• Date of issue
  June 2006

History

• Accepted
  20 Feb 2006
• Received
  20 Oct 2005