Seroprevalence of leptospirosis in a rural flood prone district of Bangladesh

Major zoonotic diseases of public health importance in Bangladesh

Zoonotic diseases cause repeated outbreaks in humans globally. The majority of emerging infections in humans are zoonotic. COVID‐19 is an ideal example of a recently identified emerging zoonotic disease, causing a global pandemic. Anthropogenic factors such as modernisation of agriculture and livestock farming, wildlife hunting, the destruction of wild animal habitats, mixing wild and domestic animals, wildlife trading, changing food habits and urbanisation could drive the emergence of zoonotic diseases in humans. Since 2001, Bangladesh has been reporting many emerging zoonotic disease outbreaks such as nipah, highly pathogenic avian influenza, pandemic H1N1, and COVID‐19. There are many other potential zoonotic pathogens such as Ebola, Middle East respiratory syndrome coronavirus, Kyasanur forest disease virus and Crimean–Congo haemorrhagic fever that may emerge in the future. However, we have a limited understanding of zoonotic diseases’ overall risk in humans and associated factors that drive the emergence of zoonotic pathogens. This narrative review summarised the major emerging, re‐emerging, neglected and other potential zoonotic diseases in Bangladesh and their associated risk factors. Nipah virus and Bacillus anthracis caused repeated outbreaks in humans. More than 300 human cases with Nipah virus infection were reported since the first outbreak in 2001. The highly pathogenic avian influenza virus (H5N1) caused more than 550 outbreaks in poultry, and eight human cases were reported so far since 2007. People of Bangladesh are frequently exposed to zoonotic pathogens due to close interaction with domestic and peri‐domestic animals. The rapidly changing intensified animal–human–ecosystem interfaces and risky practices increase the risk of zoonotic disease transmission. The narrative review's findings are useful to draw attention to the risk and emergence of zoonotic diseases to public health policymakers in Bangladesh and the application of one‐health approach to address this public health threat.

Predominance of Leptospira wolffii in north-central Bangladesh, 2019

Leptospira was detected in 48.9% of blood samples from 182 febrile patients in north-central Bangladesh in 2019. Most Leptospira were classified as L. wolffii (93%) on the basis of phylogenetic analysis of 16S ribosomal RNA genes, while others were assigned to L. borgpetersenii and L. meyeri.

Seroprevalence, Risk Factors, and Rodent Reservoirs of Leptospirosis in an Urban Community of Puerto Rico, 2015

BACKGROUND

The burden of leptospirosis in Puerto Rico remains unclear due to underreporting.

METHODS

A cross-sectional survey and rodent trapping was performed in a community within San Juan, Puerto Rico to determine the seroprevalence and risk factors for Leptospira infection. The microscopic agglutination test was used to detect anti-Leptospira antibodies as a marker of previous infection. We evaluated Leptospira carriage by quantitative polymerase chain reaction among rodents trapped at the community site.

RESULTS

Of 202 study participants, 55 (27.2%) had Leptospira agglutinating antibodies. Among the 55 seropositive individuals, antibodies were directed most frequently against serogroups Icterohaemorrhagiae (22.0%) and Autumnalis (10.6%). Of 18 captured rodents, 11 (61.1%) carried pathogenic Leptospira (Leptospira borgpetersenii, 7 and Leptospira interrogans, 2). Four participants showed their highest titer against an isolate obtained from a rodent (serogroup Ballum). Increasing household distance to the canal that runs through the community was associated with decreased risk of infection (odds ratio = 0.934 per 10-meter increase; 95% confidence interval, .952-.992).

CONCLUSIONS

There are high levels of Leptospira exposure in an urban setting in Puerto Rico, for which rodents may be an important reservoir for transmission. Our findings indicate that prevention should focus on mitigating risk posed by infrastructure deficiencies such as the canal.

Prevalence of Leptospira Infection in Rodents from Bangladesh

Worldwide, Leptospira infection poses an increasing public health problem. In 2008, leptospirosis was recognised as a re-emerging zoonosis of global importance with South-East Asia being one of the most significant centres of the disease. Rodents are thought to be the most important host for a variety of Leptospira serovars. Because Bangladesh offers a suitable humid climate for the survival of these pathogenic bacteria, the presence of rodents could be a serious risk for human infection, especially in peri-urban areas or locations where food is stored. In order to gain more understanding of the multi-host epidemiology, a prevalence study was conducted in Comilla, Bangladesh to determine the presence of pathogenic Leptospira species in rodents. Real-time Polymerase Chain Reaction (qPCR) and sequencing showed that 13.1% (61/465) of the trapped rodents were infected with pathogenic Leptospira. Sequencing of the qPCR products identified the presence of three species: Leptospira interrogans, Leptospira borgpetersenii, and Leptospira kirschneri. Rodents of the genus, Bandicota, were significantly more likely to be positive than those of the genus, Rattus and Mus. Our results confirm the importance of rodents as hosts of pathogenic Leptospira and indicate that human exposure to pathogenic Leptospira may be considerable, also in places where food (rice) is stored for longer times. This study emphasizes the need to improve rodent management at such locations and to further quantify the public health impacts of this neglected emerging zoonosis in Bangladesh.

First molecular identification of two Leptospira species (Leptospira interrogans and Leptospira wolffii) in Bangladesh

Leptospiral 16S rRNA genes were detected in 13 blood samples from 74 febrile patients in north-central Bangladesh, and their sequences phylogenetically clustered with those of Leptospira interrogans or Leptospira wolffii. Genetic diversity in O-antigen polymerase (wzy) was found in an L. interrogans sample.

Prevalence and clinical presentation of Rickettsia, Coxiella, Leptospira, Bartonella and chikungunya virus infections among hospital-based febrile patients from December 2008 to November 2009 in Bangladesh

BACKGROUND

We conducted a study to identify Rickettsia, Coxiella, Leptospira, Bartonella, and Chikungunya virus infections among febrile patients presenting at hospitals in Bangladesh.

METHODS

We collected blood samples from patients at six tertiary hospitals from December 2008 to November 2009 and performed laboratory tests at the United States Centers for Disease Control and Prevention (CDC).

RESULTS

Out of 720 enrolled patients, 263 (37%) were infected with Rickettsia; 132 patients had immunofluorescence antibody titer >64 against spotted fever, 63 patients against scrub typhus fever and 10 patients against typhus fever. Ten patients were identified with Coxiella. We isolated Leptospira from two patients and Bartonella from one patient. Ten patients had antibodies against Chikungunya virus. The proportion of patients who died was higher with rickettsial fever (5%) compared to those without a diagnosis of rickettsial infection (2%). None of the patients were initially diagnosed with rickettsial fever.

CONCLUSIONS

Rickettsial infections are frequent yet under-recognized cause of febrile illness in Bangladesh. Clinical guidelines should be revised so that local clinicians can diagnose rickettsial infections and provide appropriate drug treatment.

Human Leptospirosis Infection in Fiji: An Eco-epidemiological Approach to Identifying Risk Factors and Environmental Drivers for Transmission

Leptospirosis is an important zoonotic disease in the Pacific Islands. In Fiji, two successive cyclones and severe flooding in 2012 resulted in outbreaks with 576 reported cases and 7% case-fatality. We conducted a cross-sectional seroprevalence study and used an eco-epidemiological approach to characterize risk factors and drivers for human leptospirosis infection in Fiji, and aimed to provide an evidence base for improving the effectiveness of public health mitigation and intervention strategies. Antibodies indicative of previous or recent infection were found in 19.4% of 2152 participants (81 communities on the 3 main islands). Questionnaires and geographic information systems data were used to assess variables related to demographics, individual behaviour, contact with animals, socioeconomics, living conditions, land use, and the natural environment. On multivariable logistic regression analysis, variables associated with the presence of Leptospira antibodies included male gender (OR 1.55), iTaukei ethnicity (OR 3.51), living in villages (OR 1.64), lack of treated water at home (OR 1.52), working outdoors (1.64), living in rural areas (OR 1.43), high poverty rate (OR 1.74), living <100m from a major river (OR 1.41), pigs in the community (OR 1.54), high cattle density in the district (OR 1.04 per head/sqkm), and high maximum rainfall in the wettest month (OR 1.003 per mm). Risk factors and drivers for human leptospirosis infection in Fiji are complex and multifactorial, with environmental factors playing crucial roles. With global climate change, severe weather events and flooding are expected to intensify in the South Pacific. Population growth could also lead to more intensive livestock farming; and urbanization in developing countries is often associated with urban and peri-urban slums where diseases of poverty proliferate. Climate change, flooding, population growth, urbanization, poverty and agricultural intensification are important drivers of zoonotic disease transmission; these factors may independently, or potentially synergistically, lead to enhanced leptospirosis transmission in Fiji and other similar settings.

Leptospirosis is a bacterial infection transmitted from animals to humans, and many outbreaks are associated with flooding. Globally, leptospirosis is responsible for at least a million cases of severe illness each year, and many deaths. The bacteria are excreted in the urine of infected animals; humans can become infected through direct contact with animals or through contaminated water and soil. In Fiji, two successive cyclones and severe flooding in 2012 resulted in 576 cases and 40 deaths. We conducted this study to improve our understanding of the factors that increase the risk of leptospirosis transmission, so that public health control measures can be improved. Our study found that infection risk is related to many factors including individual demographics and behaviour, contact with animals, living conditions, poverty, and flooding risk. With global climate change, flooding is expected to become a bigger problem in the South Pacific. Population growth could lead to more intensive livestock farming; and urbanization in developing countries is often associated with slums with high risk of infectious diseases. Climate change, flooding, population growth, urbanization, poverty and livestock farming are important factors for leptospirosis transmission; these factors may combine to increase the risk of leptospirosis in Fiji and other Pacific Islands in the future.

Studying risk factors associated with human leptospirosis

BACKGROUND

Leptospirosis is one of the most under diagnosed and underreported disease in both developed and developing countries including India. It is established that environmental conditions and occupational habit of the individuals put them at risk of acquiring disease, which varies from community to community. Various seroprevalence studies across the world have documented emerging situation of this neglected tropical disease, but limited have probed to identify the risk factors, especially in India.

OBJECTIVES

The objective of this study was to identify the environmental and occupational risk factors associated with the disease in Udupi District.

MATERIALS AND METHODS

This population-based case-control study was carried out in Udupi, a District in Southern India from April 2012 until August 2012. Udupi is considered to be endemic for Leptospirosis and reported 116 confirmed cases in the year 2011. Seventy of 116 laboratory confirmed cases and 140 sex matched neighborhood healthy controls participated in the study. A predesigned, semi-structured and validated questionnaire was used for data collection through house to house visit and observations were noted about environmental conditions. Univariate analysis followed by multivariate analysis (back ward conditional logistic regression) was performed by using STATA version 9.2 (StataCorp, College Station, TX, USA) to identify potential risk factors.

RESULTS

Occupational factors such as outdoor activities (matched odds ratio [OR] of 3.95, 95% confidence interval [CI]: 1.19-13.0), presence of cut or wound at body parts during work (matched OR: 4.88, CI: 1.83-13.02) and environmental factors such as contact with rodents through using the food materials ate by rat (matched OR: 4.29, CI: 1.45-12.73) and contact with soil or water contaminated with urine of rat (matched OR: 4.58, CI: 1.43-14.67) were the risk factors identified to be associated with disease.

CONCLUSION

Leptospirosis is still considered as neglected disease in the district. Early diagnosis and prompt treatment of cases can save many lives. However, there is a need of integrated rodent control measures with great effort to increase awareness and education among subjects in controlling the disease.

Evidence of a major reservoir of non-malarial febrile diseases in malaria-endemic regions of Bangladesh

In malaria-endemic regions any febrile case is likely to be classified as malaria based on presumptive diagnosis largely caused by a lack of diagnostic resources. A district-wide prevalence study assessing etiologies of fever in 659 patients recruited in rural and semi-urban areas of Bandarban district in southeastern Bangladesh revealed high proportions of seropositivity for selected infectious diseases (leptospirosis, typhoid fever) potentially being misdiagnosed as malaria because of similarities in the clinical presentation. In an area with point prevalences of more than 40% for malaria among fever cases, even higher seroprevalence rates of leptospirosis and typhoid fever provide evidence of a major persistent reservoir of these pathogens.

Neighborhood-level socioeconomic and urban land use risk factors of canine leptospirosis: 94 cases (2002-2009)

Associations of housing, population, and agriculture census variables, and presence near public places were retrospectively evaluated as potential risk factors for canine leptospirosis using Geographic Information Systems (GIS). The sample population included 94 dogs positive for leptospirosis based on a positive polymerase chain reaction test for leptospires on urine, isolation of leptospires on urine culture, a single reciprocal serum titer of 12,800 or greater, or a four-fold rise in reciprocal serum titers over a 2-4 week period; and 185 dogs negative for leptospirosis based on a negative polymerase chain reaction test and reciprocal serum titers less than 400. Multivariable logistic regressions revealed different risk factors among different census units; however, houses lacking complete plumbing facilities [OR=2.80, 95% C.I.=1.82, 4.32 (census unit, block group); OR=1.36, 95% C.I.=1.28, 1.45 (census tract); OR=3.02, 95% C.I.=2.60, 3.52 (county)]; and poverty status by age (18-64) [OR=2.04, 95% C.I.=1.74, 2.39 (block group); OR=1.53, 95% C.I.=1.41, 1.67 (census tract); and OR=1.62, 95% C.I.=1.50, 1.76 (county)] were consistent risk factors for all census units. Living within 2500 m of a university/college and parks/forests were also significantly associated with leptospirosis status in dogs. Dogs that live under these circumstances are at higher risk for leptospirosis and pet owners should consider vaccination.

Leptospirosis as a cause of fever in urban Bangladesh

We tested paired sera from 584 febrile persons in an low-income urban community in Bangladesh for evidence of Leptospira infection. A total of 8.4% of the persons met criteria for definite or probable infection. Persons with leptospirosis were older than those with undifferentiated fever in this population. The dominant infecting serogroups in Bangladesh differed from serogroups commonly reported in nearby regions.

Risk factors associated with the seroprevalence of leptospirosis, amongst at-risk groups in and around Tanga city, Tanzania

The epidemiological status of human leptospirosis in Tanzania has not been well defined because of a general lack of awareness of the disease and difficulties in its diagnosis. A cross-sectional seroprevalence study, using the microscopic agglutination test with a threshold titre of 1 : 160, was therefore conducted, among various occupational groups from Tanga city, in November 2005. Of the 199 subjects investigated, 30 (15.1%) were found to have antibodies that reacted with antigens from at least one of the six Leptospira interrogans serovars used in the agglutination test. Of the seropositive samples, 36.6% were positive for serovar Icterohaemorrhagiae, 30.0% for Bataviae, 20.0% for Hardjo, 6.6% for Tarrassovi, 3.3% for Ballum and 3.3% for Pomona. Amongst the occupational groups examined, livestock farmers, veterinary/meat inspectors and abattoir workers appeared to be most at risk, with seroprevalences of 19.4%, 18.1% and 17.1%, respectively. Subjects who reported that they milked cows were significantly more likely to be found seropositive for Leptospira infection than the other subjects (odds ratio=3.44; P<0.001). These findings indicate that a significant proportion of the population of Tanga city is being exposed to pathogenic Leptospira. Public-health interventions against leptospirosis will need to target not only the occupational groups considered to be at high risk of infection but also the general population at large.

Leptospirosis in the Asia Pacific region

Background

Leptospirosis is a worldwide zoonotic infection that has been recognized for decades, but the problem of the disease has not been fully addressed, particularly in resource-poor, developing countries, where the major burden of the disease occurs. This paper presents an overview of the current situation of leptospirosis in the region. It describes the current trends in the epidemiology of leptospirosis, the existing surveillance systems, and presents the existing prevention and control programs in the Asia Pacific region.

Methods

Data on leptospirosis in each member country were sought from official national organizations, international public health organizations, online articles and the scientific literature. Papers were reviewed and relevant data were extracted.

Results

Leptospirosis is highly prevalent in the Asia Pacific region. Infections in developed countries arise mainly from occupational exposure, travel to endemic areas, recreational activities, or importation of domestic and wild animals, whereas outbreaks in developing countries are most frequently related to normal daily activities, over-crowding, poor sanitation and climatic conditions.

Conclusion

In the Asia Pacific region, predominantly in developing countries, leptospirosis is largely a water-borne disease. Unless interventions to minimize exposure are aggressively implemented, the current global climate change will further aggravate the extent of the disease problem. Although trends indicate successful control of leptospirosis in some areas, there is no clear evidence that the disease has decreased in the last decade. The efficiency of surveillance systems and data collection varies significantly among the countries and areas within the region, leading to incomplete information in some instances. Thus, an accurate reflection of the true burden of the disease remains unknown.

Factors associated with Leptospira sp infection in a large urban center in northeastern Brazil

Leptospirosis is a zoonotic disease that has emerged to cause epidemics in urban communities in developing countries. However, little is known about the infection in the general population. A seroprevalence survey was performed on a random sample of 1,390 subjects in Salvador, Brazil. Data on environmental and socioeconomic factors were collected. The microagglutination test of serum samples was used to show any prior Leptospira infection. The overall seroprevalence was 12.4%. Among the seropositive individuals, 111 (61%) had high titers for serovars of the Icterohaemorrhagiae serogroup. Seroprevalence increased with age and was similar for males and females. A positive correlation between Leptospira infection and low educational level was found. These findings indicate that a significant proportion of this urban population is exposed to pathogenic Leptospira. Public health actions for leptospirosis control will need to target not only the traditional groups at risk of infection with severe forms of this disease, but also the general population that is at risk.

Leptospirosis: skin wounds and control strategies, Thailand, 1999

After an outbreak of leptospirosis in workers who participated in cleaning a pond during September 1999 in Thailand, a serologic survey was conducted. Among a cohort of 104 persons from one village who participated in pond cleaning activity, 43 (41.3%) were seropositive for immunoglobulin M antibodies against Leptospira, indicating recent infection. Only 17 (39.5%) of 43 seropositive persons reported a recent febrile illness; the remaining seropositive persons were considered asymptomatic, suggesting that asymptomatic leptospirosis infection may be common where leptospirosis is endemic. Multivariable logistic regression indicated that wearing long pants or skirts was independently protective against leptospirosis infection (OR(adjusted) = 0.217), while the presence of more than two wounds on the body was independently associated with infection (OR(adjusted) = 3.97). Educational efforts should be enhanced in areas where leptospirosis is endemic to encourage the use of protective clothing. In addition, wound management and avoidance of potentially contaminated water when skin wounds are present should be included in health education programs.

Uveitis associated with an epidemic outbreak of leptospirosis

PURPOSE

To define uveitis associated with leptospirosis in a clinical setting.

METHODS

We present the clinical features of 73 consecutive cases of uveitis linked clinically to an outbreak of systemic leptospirosis in patients with antibodies to Leptospira species who were examined from January to September 1994.

RESULTS

In 73 patients, the pattern of ocular involvement was unilateral in 35 and bilateral in 38. Panuveitis was seen in 106 eyes (95.5%), retinal periphlebitis in 57 eyes (51.4%), and hypopyon in 14 eyes (12.6%). Anterior uveitis alone without hypopyon was observed in three eyes (2.7%), whereas vitreous inflammatory reaction alone was seen in two eyes (1.8%). Sixty of 73 patients (82.2%) or 91 of 111 eyes (82.0%) were followed up for 8 months. Final visual acuity was 6/6 (20/20) in 47 eyes (52%) and improved during treatment, although not up to 6/6, in 15 eyes (16%). Twenty-eight eyes (31%) maintained same vision, and one eye showed deterioration of vision.

CONCLUSION

Uveitis associated with leptospirosis may manifest as unilateral or bilateral uveitis, anterior uveitis, or panuveitis. The prognosis is generally good in this entity, even when the inflammation is severe. Awareness of this disease in endemic areas is important in order to differentiate it from other uveitic entities, especially in young male patients in whom other immunologic uveitides are also common.