SciELO - Scientific Electronic Library Online

 
vol.49 issue5Prevalence, and virulence determination of Listeria monocytogenes strains isolated from clinical and non-clinical samples by multiplex polymerase chain reactionExpression of co-stimulatory molecules CD80 and CD86 is altered in CD14 + HLA-DR + monocytes from patients with Chagas disease following induction by Trypanosoma cruzi recombinant antigens author indexsubject indexarticles search
Home Pagealphabetic serial listing  

Services on Demand

Journal

Article

Indicators

Related links

Share


Revista da Sociedade Brasileira de Medicina Tropical

Print version ISSN 0037-8682On-line version ISSN 1678-9849

Rev. Soc. Bras. Med. Trop. vol.49 no.5 Uberaba Sept./Oct. 2016

http://dx.doi.org/10.1590/0037-8682-0115-2016 

Short Communications

Seroprevalence of and risk factors for leptospirosis in the City of Manaus, State of Amazonas, Brazil

Luciete Almeida Silva1 

Kátia Maria da Silva Lima1 

Ormezinda Celeste Cristo Fernandes1 

Ilana Teruszkin Balassiano2 

Kátia Eliane Santos Avelar2 

Michele Silva de Jesus1 

1Laboratório de Diversidade Microbiana da Amazônia de Importância para a Saúde, Instituto Leônidas e Maria Deane, Manaus, Amazonas, Brazil.

2Laboratório de Referência Nacional para Leptospirose, Instituto Oswaldo Cruz, Rio de Janeiro, Rio de Janeiro, Brazil.

Abstract

INTRODUCTION

Leptospirosis is caused by a bacterium of the genus Leptospira. This study aimed at investigating the seroprevalence of and risk factors for leptospirosis in humans in Manaus, State of Amazonas.

METHODS

Interviews were performed, and 1,000 blood serum samples were examined using a microscopic agglutination test.

RESULTS

Forty-three cases were positive; there were 10 serotypes, with coagglutination in 8 cases. The most frequently occurring serotypes were Icterohaemorrhagiae (20.7%), Cynopteri (20.7%), Australis (18.8%), and Copenhageni (16.9%), and the Midwest (54.7%) and South (23.8%) had the most cases; these areas lack basic sanitation.

CONCLUSIONS

Disease occurrence might be reduced through improved basic infrastructural conditions.

Keywords: Leptospirosis; Serovars; Manaus

Leptospirosis is an acute, infectious, and systemic disease caused by a pathogenic bacterium of the Leptospiraceae family, Leptospira gender known as L. interrogans; more than 200 serovars have been described, with distribution into 19 serogroups1.

According to the Centers for Disease Control and Prevention, leptospirosis is a globally spread zoonotic disease that affects feral and domestic animals and subsequently human beings who come in contact with the urine of infected animals. In the urban environment, the main Leptospira reservoir hosts are dogs and rodents (mainly Rattus norvegicus and Rattus rattus species), which are regarded as important modes of leptospirosis transmission to humans2) (3.

Despite its global presence, leptospirosis is endemic in tropical and subtropical countries, particularly in areas that lack basic sanitation and have a high population of rodents. In Brazil, leptospirosis occurrence is closely related with the socioeconomic conditions of the population, humid tropical climate, and long and heavy rainfall seasons3.

From 1980 to 2005, about 60,000 cases of the disease were reported in Brazil, and in 2008, the Ministry of Health reported 3,306 leptospirosis cases4. According to the Health Surveillance report, 114 cases were reported in Amazonas from 2013 to 2014, of which 111 cases were reported in Manaus5.

The diversity of Leptospirosis serovars can be identified by using a microscopic agglutination test (MAT), which is considered the gold standard for diagnosis in humans by the World Health Organization. These results are mostly used in epidemiological investigations and provide important data for the serogroups in the study area6. This technique enables not only detection of circulating antibodies in an infected person but also identification of standardized serovars in affected people. The most frequent serovars detected in human beings are Icterohaemorrhagiae, Canicola, Copenhageni, and Autumnalis7) (8.

This study aimed at investigating the seroprevalence of human leptospirosis in high-risk areas for disease spread in Manaus, State of Amazonas and its associations with socioenvironmental factors.

The research was conducted with 1,802,014 residents of Manaus, Amazonas, a state in the North Region of Brazil, which has a humid tropical climate, medium temperatures, and heavy rainfalls that are more frequent in the regional winter, from January to April9.

In 2011, 1,000 blood serum samples were analyzed from asymptomatic humans in areas in which the disease had been reported and the socioenvironmental conditions were propitious for infection. Twenty neighborhoods were selected from different areas of Manaus, with characteristics that have been described previously, avoiding possible population effects on the selected neighborhoods. High-risk blocks were defined based on previously confirmed cases of leptospirosis through data analysis from the Municipal Secretariat of Health [Secretaria Municipal de Saúde (SEMSA)] of Manaus. All of the houses within a 200m radius of a positive case were identified numerically; then, 20 houses were selected using a random number table. Samples were collected from residents of these houses, of either sex and any age, that agreed to participate, with the aim of collecting samples from 50 independent individuals from the 20 randomly selected homes.

Interviews were conducted to collect socioenvironmental data for the residents of houses in which samples had been collected.

For the leptospirosis serological test, blood samples were collected in tubes without anticoagulant and transported to the Leonidas and Maria Deane Institute (ILMD) laboratory for serum separation. Then, the serum samples were transported to the Leptospirosis Reference Laboratory (FIOCRUZ/Rio de Janeiro) to undergo MAT. For this technique, 19 live antigens corresponding to globally circulating Leptospira serovars were used.

According to the Ministry of Health manual (2014), a confirmed case of leptospirosis using serology was defined using the following criteria: a negative first sample and a second sample at least 14 days later with titers ≥200; 2 samples, collected 14 days apart, with at least a 4-fold increase in titers based on MAT; or a sample with titers ≥800 based on MAT.

Of the 1,000 blood serum samples that were analyzed using MAT, 43 were positive. Ten types of globally circulating serovars were identified. The most frequently occurring serovars detected in asymptomatic people were Icterohaemorragiae (20.7%), Cynopteri (20.7%), Australis (18.8%), and Copenhageni (16.9%) (Table 1).

TABLE 1 Frequency of Leptospirosis serovars in sera samples of asymptomatic humans living in the City of Manaus, State of Amazonas, in 2011. 

Of the 53 identified serovars, 8 (16.3%) samples showed positive serological reactions to more than one Leptospira serovar (Table 2). This could be explained by the existence of paradoxical reactions and cross-reactions between serogroups observed with the MAT10. Among the main antibodies detected using this methodology are those specific against lipopolysaccharides (LPS), one of the most abundant macromolecules present in the leptospiral outer membrane. It was previously observed that antibodies against LPS in patients with leptospirosis are highly related with Leptospira serovars11.

TABLE 2 Results of Leptospirosis serovar coagglutination in sera samples of asymptomatic humans living in the City of Manaus, State of Amazonas, in 2011. 

In the analysis of sociodemographic features, a percentage of the positive samples was distributed in 6 districts of Manaus; the highest serovar concentration rate was observed in the West area (54.7%), followed by the South (23.8%), North (19,2%), and Midwest (2.3%). The West and South areas had the highest seropositive rates (each, 73.7%) (Figure 1).

FIGURE 1 Distribution of leptospirosis cases in the neighborhoods of Manaus, State of Amazonas. 1: Nova Esperança; 2: Cidade Nova; 3: Santo Agostinho; 4: Compensa; 5: Crespo; 6: Raiz; 7: Glória; 8: Santo Antônio; 9: Lírio do Vale; 10: Praça 14; 11: Nova Cidade; 12: Cachoeirinha; 13: Alvorada. 

Of the infected people, 25 (58.1%) were men, and 18 (41.8%) were women. The highest rate was observed for individuals aged 23-44 years old (51.1%), who were mostly men (58.3%). Regarding education, 71.4% had not finished any grade, 9.30% had finished elementary school, 9.3% had not finished high school, 4.6% had finished high school, and 4.6% were illiterate; none of the participants had started undergraduate studies.

The results of the present study indicate an endemic scenario of leptospirosis in the city of Manaus, based on the detection of different serovars in asymptomatic individuals. The prevalence of leptospirosis infection (4.3%) is one of the lowest reported in serological surveys in Brazil, which range from 9.7% to 28.5%. However, those surveys were conducted with high-risk groups, whereas the present study included the general population. The results support another study conducted in the City of Belém, State of Pará, which also had an endemic profile with a few cases during the investigation12.

Among the analyzed samples, ten different globally circulating serovars were detected, with no significant statistical difference. However, Icterohaemorragiae (20.7%), Cynopteri (20.7%), Australis (18.8%), and Copenhageni (16.9%) were the most frequently detected serovars. In most of the leptospirosis cases detected in urban areas in Brazil, strains of the serogroup Icterohaemorragiae, whose main host carriers are Rattus rattus and Rattus norvergicus (domestic rat), have been observed, reinforcing the participation of ordinary rats in the leptospirosis transmission chain13. Similarly, in the present study, the serogroup Icterohaemorragiae was the most pathogenic serovar for human beings.

Socioenvironmental conditions in Manaus favor infection by more than one serovar, as identified in several individuals; the diversity of infected reservoirs and favorable environment for bacterial proliferation to which people are exposed might explain these results. Human infections are related with exposure to contaminated water, urine, or other infected animal tissues and to the environmental conditions in countries with tropical and subtropical climates, mainly during seasons of heavy rain3) (13.

In Manaus, the South and West areas had the highest rate of seropositivity (73.7%); these areas are located around the two river basins for the São Raimundo and Educandos rivers, which are often affected by seasonal floods. The highest rate was present for young men; similarly, previous studies in Manaus showed that the disease mainly affected young male adults with limited schooling who had been infected while performing strenuous activities either at home or work14.

The infected individuals lived in high-risk areas, in substandard housing near streams or open sewage, usually exposed to floods. Previous studies also identified that areas with poor sanitation, rodents, and dogs contribute to the natural spread of leptospirosis15.

Therefore, the risk of leptospirosis transmission in urban areas of Manaus may be reduced through improved basic infrastructural conditions (sewage, pluvial water drainage, proper garbage collection and disposal, and extinction of rodents); in addition, streams and rivers should be cleaned and dredged, which are fundamental measures to mitigate the frequency of floods and consequently reduce disease proliferation.

Acknowledgments

The authors thank Fernanda Fonseca and Antônio Alcirley da Silva Balieiro.

References

1. Machry L, Ribeiro RL, Vital-Brazil JM, Balassiano IT, Oliveira ICM, Avelar KES, et al. Caracterização de cepas de referência de Leptospira sp utilizando a técnica de pulse field gel electrophoresis. Rev Soc Bras Med Trop 2010; 43:166-169. [ Links ]

2. Sampaio GP, Wanderley MR, Casseb GB, Negreiros MAMP. Descrição epidemiológica dos casos de leptospirose em hospital terciário de Rio Branco. Rev Bras Clin Med 2011; 9:338-342. [ Links ]

3. Castro JR, Salaberry SRS, Souza MA, Ribeiro AMCL. Sorovares de Leptospira spp. predominantes em exames sorológicos de caninos e humanos no município de Uberlândia, Estado de Minas Gerais. Rev Soc Bras Med Trop 2011; 44:217-222. [ Links ]

4. Vasconcelos CH, Fonseca FR, Lise MLZ, Arsky MLNS. Fatores ambientais e socioeconômicos relacionados à distribuição de casos de leptospirose no Estado de Pernambuco, Brasil, 2001-2009. Cad Saude Colet 2012; 20:49-56. [ Links ]

5. Ministério da Saúde.Secretaria de Vigilância Sanitária em Saúde: Boletim de Vigilância em Saúde. Amazonas: SVS/MS; 2013-2014. [ Links ]

6. Majd NS, Darian EK, Khaki P, Bidhendi SM, Yahaghi E, Mirnejad R. Epidemiological patterns of Leptospira spp. among slaughterhouse workers in Zanjan-Iran. Asian Pac J Trop Dis 2012; 2 (supl 2):S550-S552. [ Links ]

7. Bezerra LFM. Diagnóstico laboratorial de dengue e leptospirose em pacientes com síndrome febril aguda. Dissertação de Mestrado em Patologia. Fortaleza: Universidade Federal do Ceará; 2012. 109p. [ Links ]

8. Miraglia F, Matsuo M, Morais ZM, Dellagostin AO, Seixas FK, Freitas JC, et al. Molecular characterization, serotyping, and antibiotic susceptibility profile of Leptospira interrogans serovar Copenhageni isolates from Brazil. Diagn Microbiol Infect Dis 2013; 195-199. [ Links ]

9. Instituto Brasileiro de Geografia e Estatística (IBGE). Resultado da amostra do censo demográfico 2010 (Internet). IBGE; 2010. Cited 2015 september 10. Disponível em Disponível em http://www.ibge.com.gov.br . [ Links ]

10. Nascimento AL, Verjovski-Almeida S, Van Sluys MA, Monteiro-Vitorello CB, Camargo LE, Digiampietri LA, et al. Genome features of Leptospira interrogans serovar Copenhageni. Braz J Med Biol Res 2004; 37:459-477. [ Links ]

11. Bourhy P, Herrmann Storck C, Theodose R, Olive C, Nicolas M, Hochedez P, et al. Serovar diversity of pathogenic Leptospira circulating in the French West Indies. PLoS Negl Trop Dis 2013; 7:e2114. [ Links ]

12. Lima RJS, Abreu EMN, Ramos FLP, Santos RD, Santos DD, Santos FAA, et al. Análise da distribuição espaço-temporal da leptospirose humana em Belém, Estado do Pará, Brasil. Rev Pan-Amaz Saude 2012; 3:33-40. [ Links ]

13. Figueiredo CM, Mourão AC, Oliveira MAA, Alves WR, Ooteman MC, Chamone CB, et al. Leptospirose humana no município de Belo Horizonte, Minas Gerais, Brasil: uma abordagem geográfica. Rev Soc Bras Med Trop 2001; 34:331-338. [ Links ]

14. Jesus MS, Silva LA, Lima KMS, Fernandes OCC. Cases distribution of leptospirosis in city of Manaus, state of Amazonas, Brasil, 2000-2010. Rev Soc Med Trop 2012; 45:713-716. [ Links ]

15. Soares TSM, Latorre MRDO, Laporta GZ, Buzzar MR. Análise espacial e sazonal da leptospirose no município de São Paulo, SP, 1998 a 2006. Rev Saude Publica 2010; 44:283-291. [ Links ]

Fundação de Amparo à Pesquisa do Estado do Amazonas (FAPEAM) provided financial support (public notices N. 007/2009-Programa Pesquisa para o SUS (PPSUS) and N. 020/2013-PAPAC)

Received: March 29, 2016; Accepted: August 08, 2016

Corresponding author : Msc. Michele Silva e-mail: michele@amazonia.fiocruz.br

The authors declare that there is no conflict of interest.

Creative Commons License This is an open-access article distributed under the terms of the Creative Commons Attribution License