Skip Navigation
Skip to contents

PHRP : Osong Public Health and Research Perspectives

OPEN ACCESS
SEARCH
Search

Articles

Page Path
HOME > Osong Public Health Res Perspect > Volume 7(3); 2016 > Article
Original Article
Study on Seroprevalence and Leptospiral Antibody Distribution among High-risk Planters in Malaysia
J. Mohd Ridzuan, B.D. Aziah, W.M. Zahiruddin
Osong Public Health and Research Perspectives 2016;7(3):168-171.
DOI: https://doi.org/10.1016/j.phrp.2016.04.006
Published online: May 5, 2016

Department of Community Medicine, School of Medical Sciences, Universiti Sains Malaysia Health Campus, Kota Bharu, Malaysia

∗Corresponding author. aziahkb@usm.my
• Received: September 14, 2015   • Revised: April 19, 2016   • Accepted: April 20, 2016

Copyright © 2016 Korea Centers for Disease Control and Prevention. Published by Elsevier Korea LLC.

This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

  • 2,567 Views
  • 18 Download
  • 12 Crossref
  • 16 Scopus
  • Objectives
    To determine the leptospirosis seroprevalence and to identify the predominant infecting serovars among oil palm plantation workers.
  • Methods
    The cross-sectional study involved 350 asymptomatic oil palm plantation workers in Melaka and Johor. A serological test using the microscopic agglutination test was conducted in the Institute of Medical Research with a cut-off titre for seropositivity of ≥1:100.
  • Results
    The overall seroprevalence of leptospiral antibodies was 28.6%. The job category with the highest seroprevalence was the fruit collector with 59.2%. The predominant serovar identified was serovar Sarawak (Lepto 175) (62%).
  • Conclusion
    A high seroprevalence of leptospiral antibodies was detected among oil palm plantation workers and specifically among fruit collectors. The predominant infecting serovar among the workers was serovar Sarawak (Lepto 175). The findings suggest that more studies are needed to determine the reasons for the high seroprevalence and the transmission and pathogenicity of the local serovar Sarawak (Lepto 175).
Leptospirosis is a potentially fatal bacterial infection recognized as a zoonotic spirochetal disease. The disease is also considered as a re-emerging global public health issue of worldwide importance, especially in tropical and subtropical countries. The exact number of human cases in the world is not precisely known because of the lack of surveillance data worldwide [1]. Recent data have shown that Malaysia is an endemic country for leptospirosis, with an increased number of reported cases and outbreaks and a significant number of deaths over the past decade 2, 3. The prevalence of leptospirosis in Malaysia increased from 2004 to 2009, and the case fatality rate within that period varied from 1.8% to 7.6% [4].
Leptospirosis is transmitted to humans through skin or the mucous membrane coming into contact with water, moist soil, vegetation, or environmental surfaces contaminated with the urine of an infected animal. Symptomatic leptospirosis usually manifests itself as a range of diseases from a flu-like illness to Weil's syndrome, with the case fatality rate ranging from 5% to 15%, and is characterized by jaundice, renal failure, and hemorrhage [5]. The past outbreaks of leptospirosis in developed countries were often related to recreational activities, whereas these outbreaks tended to be seasonal in nature, related to animal activities, and related to agricultural and occupational factors in developing countries 6, 7. A recent hospital-based study reported that the majority of leptospirosis cases in Malaysia were among agricultural workers [8].
The palm oil industry is the main agricultural sector in Malaysia, one of the world’s main palm oil exporters, and it accounts for 77% of the total agricultural land and has become the fourth largest contributor to the Malaysian economy 9, 10. The available data show that the palm oil industry in Malaysia is a major sector of employment, with the industry supporting more than 1.4 million jobs and 468,056 people hired as field workers in plantations 10, 11.
2.1 Study design and population
A cross-sectional study was conducted in June 2014 involving 10 oil palm plantations in Melaka and Johor, which are southern states of Malaysia. The study was granted ethical approval by the Research and Ethics Committee (Human), School of Medical Sciences, Health Campus, Universiti Sains Malaysia, Kota Bharu, Malaysia. All the workers involved voluntarily signed the informed consent form after they were given a detailed explanation about the procedure and adequate time to make a decision.
Oil palm plantation workers have seven job categories: (1) fruit collector; (2) harvester; (3) pruner; (4) pesticide applicator; (5) fertilizer applicator; (6) driver; and (7) nursery worker.
Calculated based on a 32.6% seroprevalence of leptospirosis among oil palm workers [12], 95% confidence interval (CI) and 10% nonresponse rate, the estimated sample size required for the study was 374. The sampling frame consisted of workers who had been working in the plantation for more than 6 months. Office workers were excluded.
2.2 Blood samples and serologic tests
The consenting respondents were interviewed for sociodemographics, job category, and duration of employment. Venous blood samples were tested for the presence of antileptospiral antibodies using microscopic agglutination test (MAT) at the Institute of Medical Research (IMR) following standard methods [13]. The MAT was performed with a panel of live leptospire reference cultures obtained from the Royal Tropical Institute (World Health Organization/Food and Agriculture Organization of the United Nations Collaborating Centre for Reference and Research on Leptospirosis) in Amsterdam, The Netherlands (Australis, Autumnalis, Bataviae, Canicola, Celledoni, Grippotyposa, Icterohaemorrhagiae, Javanica, Pomona, Pyrogenes, Hardjoprajitno, Patoc, Tarassovi, and Djasiman) and from the IMR (Melaka, Terengganu, Sarawak, Lai, Hardjobovis, and Copenhagani).
Live leptospire cell suspensions representing 20 serovars were added to serially diluted serum specimens in 96-wells microliter plates and were incubated at 30°C for 2 hours. Through dark field microscopy, agglutination was examined at a magnification of 100 times. Using the control well for comparison, agglutination was examined by observing free leptospires in each well. The MAT were considered positive if the free leptospire approximate numbers were < 50% in the control well. A titer of ≥ 1:100 was used as the cut-off titer for leptospirosis seropositive in this study. The level of titer indicated previous exposure to the leptospira bacteria [3].
2.3 Statistical analysis
Data were entered and analyzed using IBM SPSS version 22 for Windows [14]. All continuous variables were described using means and standard deviations. Frequencies and percentages were presented for categorical variables. Seroprevalence of leptospirosis was described with a 95% CI.
Among the 374 total respondents recruited, there were 350 participants in this study, resulting in a response rate of 93.6%. Table 1 shows the sociodemographic characteristics of the oil palm plantation workers. The respondents were workers who were relatively young, with a mean age of 31.38 (standard deviation, 9.68) years and the majority of the workers were men (84.6%). According to citizenship, 285 (81.4%) of the respondents were non-Malaysians. Most of the respondents (71.1%) had either primary or secondary school experience and 101 (28.9%) had no formal education.
The overall seroprevalence of leptospirosis was 28.6% (95% CI: 0.24, 0.33). Among the respondents, fruit collectors showed the highest seroprevalence of 59.2%, followed by harvesters and pesticide applicators at 24.5%, respectively (Table 2).
Table 3 shows the distribution of serovars among 100 seropositive cases determined by the positive MAT titer ≥ 1:100. The most common reaction obtained in the sera tested was the leptospira spp. strain isolated from the serovar Sarawak (Lepto 175) at 62.0%, followed by serovar Patoc at 42% and serovars Pyrogenes, Copenhageni, and Terengganu at 1%, respectively.
This study revealed a high seroprevalence rate of 28.6% obtained from the scientific laboratory MAT, consistent with other studies. This finding is supported by that of a survey on anti-Leptospira antibodies using the sensitized-erythrocyte-lysis test conducted on 18 occupational groups in West Malaysia: the highest antibody rate of 32.6% was found among oil palm plantation workers [12]. Another local study conducted among healthy paddy planters in Northeastern Malaysia using the sensitized-erythrocyte-lysis test also reported 24.2% seroprevalence [15]. Using similar methods and a cut-off value of the MAT titer for comparison, Shafei et al [3] reported a low seroprevalence (24.8%) of leptospirosis among town service workers in Kelantan, which are considered another high-risk occupational group for the infection. This finding shows that oil palm plantation workers are comparably at a high risk of leptospiral infection.
The high positivity in the seroprevalence of leptospiral antibodies in this study may be related to rats, which are the main leptospire carrier and can be found in abundance in oil palm plantations because rats are attracted to fresh oil palm fruit 15, 16. Moreover, the pathogenic leptospires are able to survive for long periods of time in the oil palm plantation environment, which is characterized by a favorable tropical climate and moist and warm soil and surface water conditions [17].
The highest seropositivity of anti-leptospira antibodies was detected among fruit collectors (29, 59.2%), followed by harvesters (23, 24.5%), pesticide applicators (13, 24.5%), and pruners (15, 23.4%). Compared with the other job categories, fruit collectors are the oil palm plantation workers with the most contact with the surface environment of soil and water, and are the most at risk to obtain wounds on their hands. This condition is due to the nature of their job that consists of collecting loose fruits from the ground and manually lifting the thorny fruits into the cart. The higher frequency of serovars detected in this workers group may also be due to their poor personal protective equipment practices. As observed during the study, only a few fruit collectors wore gloves while working, and this practice further contributes to the high exposure to the leptospire-contaminated environment.
The predominant pathogenic serovar noted was Sarawak (62%), followed by Patoc (42%). Currently, no information on the pathogenicity of the serovar Sarawak and its endemicity in Malaysia is available. An on-going study is conducted by the IMR Kuala Lumpur on the serovar Sarawak [18]. Similar to the finding of the current study, a seroprevalence survey conducted in Selangor, Malaysia, among town service workers, who also fall in the leptospirosis high-risk occupational group, found that the highest local serovar was Sarawak at 37.0% [19]. Moreover, a leptospirosis study involving wild animals in Sarawak, East Malaysia, found that 72% of the seropositive samples from monkeys, rats, bats, squirrels, and mongooses were also positive for the serovar Sarawak (Lepto 175) antibody [18]. Local animal sources of particularly identified infecting serovars should be determined to ascertain the transmission pathway. In relation to our study, we could not speculate on animal reservoirs as surveys involving local animals have not been conducted in these areas.
The seroprevalence study in this high-risk occupational group of workers may reflect exposure but not necessarily the overt disease. The reason is that serovar-specific antibodies are protective, and the person is considered immune to reinfection with the same serovar, even if reinfection involving different serovars may still occur 19, 20.
The high seroprevalence indicates that oil palm plantation workers are the occupational risk group for leptospiral infection. The workers become exposed in the possibly leptospire-contaminated workplace through manual work practices that put them at risk of leptospiral infection.
Sarawak (Lepto 175) is the predominant infecting serovar detected among the seropositive oil palm plantation workers. As this study did not include leptospirosis among animal reservoirs, we could not conclude the pattern and interaction between humans and animal hosts. We recommend further studies on local animal reservoirs to provide important information on predominant serovars.
We declare that we have no conflict of interest in the publication of this paper.
Acknowledgements
The authors would like to express their deepest gratitude to all the respondents of the study who provided their valuable responses.
  • 1. Hartskeerl R., Collares Pereira M., Ellis W.. Emergence, control and re-emerging leptospirosis: dynamics of infection in the changing world. Clin Microbiol Infect 17(4). 2011 Apr;494−501. PMID: 21414083.ArticlePubMed
  • 2. Disease Control Division, Department of Public Health, Ministry of Health Malaysia . Guidelines for the Diagnosis, Management, Prevention and Control of Leptospirosis in Malaysia. 2011. Ministry of Health Malaysia; Malaysia.
  • 3. Shafei M., Sulong M.R., Yaacob N.A.. Seroprevalence of leptospirosis among town service workers in Northeastern State of Malaysia. Int J Collab Res Internal Med Public Health 4(4). 2012 Apr;395−403.
  • 4. Thayaparan S., Robertson I., Fairuz A.. Leptospirosis, an emerging zoonotic disease in Malaysia. Malays J Pathol 35(2). 2013 Dec;123−132. PMID: 24362475.PubMed
  • 5. Bharti A.R., Nally J.E., Ricaldi J.N.. Leptospirosis: a zoonotic disease of global importance. Lancet Infect Dis 3(12). 2003 Dec;757−771. PMID: 14652202.ArticlePubMed
  • 6. Faine S.. Leptospira and leptospirosis. 1994. CRC Press Inc.; Boca Raton (USA).
  • 7. Katz A.R., Sasaki D.M., Mumm A.H.. Leptospirosis on Oahu: an outbreak among military personnel associated with recreational exposure. Mil Med 162:1997 Feb;101−104. PMID: 9038027.ArticlePubMed
  • 8. Rafizah A.A.N., Aziah B.D., Azwany Y.N.. A hospital-based study on seroprevalence of leptospirosis among febrile cases in northeastern Malaysia. Int J Infect Dis 17(6). 2013 Jun;394−397.Article
  • 9. Economic Planning Unit . Tenth Malaysia Plan 2011–2015. 2010. Economic Planning Unit, Percetakan Nasional Malaysia Berhad; Malaysia.
  • 10. Malaysian Palm Oil Board . Palm oil development and performance in Malaysia. Proceedings from USITC, Washington DC. 2010.
  • 11. Malaysian Palm Oil Council . Malaysian Palm Oil Industry. 2013. [Internet]. Available from:. www.mpoc.org.my. [accessed 09.01.14].
  • 12. Tan D.S.. Leptospirosis in West Malaysia—Epidemiology and laboratory diagnosis. Malays J Pathol 2:1979 Aug;1−6. PMID: 263416.PubMed
  • 13. World Health Organization . Leptospirosis: Laboratory Manual. 2007. WHO; New Delhi.
  • 14. International Business Machines . IBM SPSS Statistics for Windows, Version 22.0. 2013. IBM Corporation; Armonk, NY.
  • 15. Tan D.S.. Leptospirosis in rural West Malaysia. Med J Malaya 24(4). 1970 Jun;261−266. PMID: 4248346.PubMed
  • 16. Mohamed-Hassan S., Bahaman A., Mutalib A.. Prevalence of pathogenic leptospires in rats from selected locations in peninsular Malaysia. Res J Anim Sci 6(1). 2012 Jan;12−25.Article
  • 17. Ridzlan F., Bahaman A.R., Khairani-Bejo S.. Detection of pathogenic Leptospira from selected environment in Kelantan and Terengganu, Malaysia. Trop Biomed 27(3). 2010 Dec;632−638. PMID: 21399605.PubMed
  • 18. Thayaparan A., Robertson I., Fairuz A.. Serological prevalence of leptospiral infection in wildlife in Sarawak, Malaysia. Borneo J Resour Sci Technol 2(2). 2013;79−82.Article
  • 19. Ganoza C.A., Matthias M.A., Collins-Richards D.. Determining risk for severe leptospirosis by molecular analysis of environmental surface waters for pathogenic Leptospira. PLoS Med 3(8). 2006 Aug;308−310.Article
  • 20. Romero E.C., Bernardo C.C.D.M., Yasuda P.H.. Human leptospirosis: a twenty-nine-year serological study in São Paulo, Brazil. Rev Inst Med Trop Sao Paulo 45(5). 2003 Sep–Oct;245−248. PMID: 14743663.ArticlePubMed
Table 1
Sociodemographic characteristics of the respondents (n = 350).
Variables Frequency (%) Mean (SD)
Age (y) 31.4 (9.68)
Sex
 Male 296 (84.6)
 Female 54 (15.4)
Citizenship
 Malaysian 65 (18.6)
 Non-Malaysian 285 (81.4)
Marital status
 Married 229 (65.4)
 Single/widower 121 (34.6)
Income
 <RM1,000 135 (38.6)
 RM1,000–2,000 201 (57.4)
 >RM2,000 14 (4.0)
Education
 No formal education 101 (28.9)
 Primary school 144 (41.1)
 Secondary school 105 (30.0)

RM = Malaysian Ringgit.

Table 2
Seroprevalence of leptospirosis seropositivity according to job category (n = 350).
Job category n MAT ≥ 1:100
95% CI
Frequency (%)
Driver 23 5 (21.7) 3.5, 39.9
Fertilizer applicator 48 11 (22.9) 10.6, 35.3
Fruit collector 49 29 (59.2) 44.9, 73.5
Harvester 94 23 (24.5) 15.6, 33.3
Pesticide applicators 53 13 (24.5) 12.6, 36.5
Pruner 64 15 (23.4) 12.7, 34.1
Nursery worker 19 4 (21.1) 0.9, 41.2
Total 350 100 (28.6) 23.8, 33.3

CI = confidence interval; MAT = microscopic agglutination test.

Table 3
Serovar distribution among 100 plantation workers determined by positive microscopic agglutination test (titer ≥ 1:100).
Serovars tested Frequency %
Sarawak 62 62
Patoc 42 42
Celledoni 7 7
Javanica 3 3
Australis 3 3
Autumnalis 2 2
Pyrogenes 1 1
Copenhageni 1 1
Terengganu 1 1

Workers tested may be positive to one or more serovars.

Figure & Data

References

    Citations

    Citations to this article as recorded by  
    • Leptospirosis in Vietnam
      N. K. Tokarevich, O. V. Blinova
      Russian Journal of Infection and Immunity.2022; 12(6): 1019.     CrossRef
    • Seroprevalence and serovar distribution of Leptospirosis among healthy people in Vietnam: Results from a multi-center study
      Van Dinh Tran, Le Thi Phuong Mai, Nguyen Thi Thu, Bui Kim Linh, Phan Dang Than, Nguyen Tu Quyet, Luu Phuong Dung, Tran Ngoc Phuong Mai, Nguyen Thi My Hanh, Hoang Hai, Tran Nhu Duong, Dang Duc Anh
      Clinical Epidemiology and Global Health.2021; 10: 100700.     CrossRef
    • Cross-sectional survey for sheep leptospirosis in the northeast region of Brazil
      José Dêvede da Silva, Maira Porto Viana, Lucas Gonzales Lima Pereira Calado, Ana Milena César Lima, Francisco Selmo Fernandes Alves, Raimundo Rizaldo Pinheiro, Diego Figueiredo da Costa, Glaucenyra Cecília Pinheiro da Silva, Sérgio Santos de Azevedo, Cleb
      Preventive Veterinary Medicine.2021; 197: 105525.     CrossRef
    • Seroprevalence of leptospirosis in an endemic mixed urban and semi-urban setting—A community-based study in the district of Colombo, Sri Lanka
      Senaka Rajapakse, Praveen N. Weeratunga, Krishan Balaji, Kyra Charmaine Ramchandani, Udani Savbhagya de Silva, Shenali Avishka Ranasinghe, Dinesh Gunarathne, Pasindu P. B. Wijerathne, Narmada Fernando, Shiroma M. Handunnetti, Sumadhya Deepika Fernando, Me
      PLOS Neglected Tropical Diseases.2020; 14(5): e0008309.     CrossRef
    • An historical view of the experimental leptospiral infection in ruminants
      Bruno Ribeiro Rocha, Gabriel Martins, Walter Lilenbaum
      Comparative Immunology, Microbiology and Infectiou.2020; 73: 101532.     CrossRef
    • Detection of Leptospira kmetyi at recreational areas in Peninsular Malaysia
      Aznida Mohamad Zaki, Rozita Hod, Nadia Aqilla Shamsusah, Zaleha Md Isa, Siti Khairani Bejo, Hani Kartini Agustar
      Environmental Monitoring and Assessment.2020;[Epub]     CrossRef
    • High incidence of asymptomatic leptospirosis among urban sanitation workers from Kota Kinabalu, Sabah, Malaysian Borneo
      Mohammad Saffree Jeffree, Daisuke Mori, Nur Athirah Yusof, Azman Bin Atil, Khamisah Awang Lukman, Rafidah Othman, Mohd Rohaizat Hassan, Lela Suut, Kamruddin Ahmed
      Scientific Reports.2020;[Epub]     CrossRef
    • Association of rodent-borne Leptospira spp. with urban environments in Malaysian Borneo
      Kim R. Blasdell, Serge Morand, David Perera, Cadhla Firth, Mathieu Picardeau
      PLOS Neglected Tropical Diseases.2019; 13(2): e0007141.     CrossRef
    • Seroprevalence of leptospiral antibodies among market workers and food handlers in the central state of Malaysia
      S. Samsudin, S. N. S. Sakinah, O. Malina, B. A. Norliza, M. A. Noh, A. Fairuz, T. Z. M. T. Jamaluddin, R. A. Hamat, W. M. Zahiruddin, S. Mohd Nazri, S. Sukeri, B. D. Aziah, I. Zawaha, A. W. Zainudin, N. A. Munirah, M. N. Desa, V. Neela, S. N. Masri
      Tropical Medicine & International Health.2018; 23(3): 327.     CrossRef
    • Seroprevalence and distribution of leptospirosis serovars among wet market workers in northeastern, Malaysia: a cross sectional study
      Mas Harithulfadhli Agus Ab Rahman, Suhaily Mohd Hairon, Rukman Awang Hamat, Tengku Zetty Maztura Tengku Jamaluddin, Mohd Nazri Shafei, Norazlin Idris, Malina Osman, Surianti Sukeri, Zainudin A. Wahab, Wan Mohd Zahiruddin Wan Mohammad, Zawaha Idris, Aziah
      BMC Infectious Diseases.2018;[Epub]     CrossRef
    • Chronic experimental genital leptospirosis with autochthonous Leptospira santarosai strains of serogroup Sejroe
      Bruno Ribeiro Rocha, Mário Balaro, Paulo Victor Pereira, Gabriel Martins, Walter Lilenbaum
      Small Ruminant Research.2018; 164: 28.     CrossRef
    • Occurrence of Leptospira Species from Rodents, Soil and Water from an Oil Palm Plantation in Northern Sarawak
      Lesley Maurice Bilung, Chai Fung Pui, Ahmad Syatir Tahar, Kasing Apun, Lela Su`ut, Yee Ling Chong, Jayasilan Mohd-Azlan
      Asian Journal of Animal and Veterinary Advances.2018; 13(4): 332.     CrossRef

    • PubReader PubReader
    • Cite
      Cite
      export Copy
      Close
    • XML DownloadXML Download

    PHRP : Osong Public Health and Research Perspectives