Estimating Leptospirosis Incidence Using Hospital-Based Surveillance and a Population-Based Health Care Utilization Survey in Tanzania

Background

The incidence of leptospirosis, a neglected zoonotic disease, is uncertain in Tanzania and much of sub-Saharan Africa, resulting in scarce data on which to prioritize resources for public health interventions and disease control. In this study, we estimate the incidence of leptospirosis in two districts in the Kilimanjaro Region of Tanzania.

Methodology/Principal Findings

We conducted a population-based household health care utilization survey in two districts in the Kilimanjaro Region of Tanzania and identified leptospirosis cases at two hospital-based fever sentinel surveillance sites in the Kilimanjaro Region. We used multipliers derived from the health care utilization survey and case numbers from hospital-based surveillance to calculate the incidence of leptospirosis. A total of 810 households were enrolled in the health care utilization survey and multipliers were derived based on responses to questions about health care seeking in the event of febrile illness. Of patients enrolled in fever surveillance over a 1 year period and residing in the 2 districts, 42 (7.14%) of 588 met the case definition for confirmed or probable leptospirosis. After applying multipliers to account for hospital selection, test sensitivity, and study enrollment, we estimated the overall incidence of leptospirosis ranges from 75–102 cases per 100,000 persons annually.

Conclusions/Significance

We calculated a high incidence of leptospirosis in two districts in the Kilimanjaro Region of Tanzania, where leptospirosis incidence was previously unknown. Multiplier methods, such as used in this study, may be a feasible method of improving availability of incidence estimates for neglected diseases, such as leptospirosis, in resource constrained settings.     

Seroprevalence and Spatial Epidemiology of Lymphatic Filariasis in American Samoa after Successful Mass Drug Administration

Background

As part of the Global Programme to Eliminate Lymphatic Filariasis (LF), American Samoa conducted mass drug administration (MDA) from 2000–2006, and passed transmission assessment surveys in 2011–2012. We examined the seroprevalence and spatial epidemiology of LF post-MDA to inform strategies for ongoing surveillance and to reduce resurgence risk.

Methods

ELISA for LF antigen (Og4C3) and antibodies (Wb123, Bm14) were performed on a geo-referenced serum bank of 807 adults collected in 2010. Risk factors assessed for association with sero-positivity included age, sex, years lived in American Samoa, and occupation. Geographic clustering of serological indicators was investigated to identify spatial dependence and household-level clustering.

Results

Og4C3 antigen of >128 units (positive) were found in 0.75% (95% CI 0.3–1.6%) of participants, and >32 units (equivocal plus positive) in 3.2% (95% CI 0.6–4.7%). Seroprevalence of Wb123 and Bm14 antibodies were 8.1% (95% CI 6.3–10.2%) and 17.9% (95% CI 15.3–20.7%) respectively. Antigen-positive individuals were identified in all ages, and antibody prevalence higher in older ages. Prevalence was higher in males, and inversely associated with years lived in American Samoa. Spatial distribution of individuals varied significantly with positive and equivocal levels of Og4C3 antigen, but not with antibodies. Using Og4C3 cutoff points of >128 units and >32 units, average cluster sizes were 1,242 m and 1,498 m, and geographical proximity of households explained 85% and 62% of the spatial variation respectively.

Conclusions

High-risk populations for LF in American Samoa include adult males and recent migrants. We identified locations and estimated the size of possible residual foci of antigen-positive adults, demonstrating the value of spatial analysis in post-MDA surveillance. Strategies to monitor cluster residents and high-risk groups are needed to reduce resurgence risk. Further research is required to quantify factors contributing to LF transmission at the last stages of elimination to ensure that programme achievements are sustained.     

Leptospirosis outbreak following severe flooding: a rapid assessment and mass prophylaxis campaign; Guyana, January-February 2005

Background

Leptospirosis is a zoonosis usually transmitted through contact with water or soil contaminated with urine from infected animals. Severe flooding can put individuals at greater risk for contracting leptospirosis in endemic areas. Rapid testing for the disease and large-scale interventions are necessary to identify and control infection. We describe a leptospirosis outbreak following severe flooding and a mass chemoprophylaxis campaign in Guyana.

Methodology/Principal Findings

From January–March 2005, we collected data on suspected leptospirosis hospitalizations and deaths. Laboratory testing included anti-leptospiral dot enzyme immunoassay (DST), immunohistochemistry (IHC) staining, and microscopic agglutination testing (MAT). DST testing was conducted for 105 (44%) of 236 patients; 52 (50%) tested positive. Four (57%) paired serum samples tested by MAT were confirmed leptospirosis. Of 34 total deaths attributed to leptospirosis, postmortem samples from 10 (83%) of 12 patients were positive by IHC. Of 201 patients interviewed, 89% reported direct contact with flood waters. A 3-week doxycycline chemoprophylaxis campaign reached over 280,000 people.

Conclusions

A confirmed leptospirosis outbreak in Guyana occurred after severe flooding, resulting in a massive chemoprophylaxis campaign to try to limit morbidity and mortality.     

Where Does Human Plague Still Persist in Latin America?

Background

Plague is an epidemic-prone disease with a potential impact on public health, international trade, and tourism. It may emerge and re-emerge after decades of epidemiological silence. Today, in Latin America, human cases and foci are present in Bolivia, Brazil, Ecuador, and Peru.

Aims

The objective of this study is to identify where cases of human plague still persist in Latin America and map areas that may be at risk for emergence or re-emergence. This analysis will provide evidence-based information for countries to prioritize areas for intervention.

Methods

Evidence of the presence of plague was demonstrated using existing official information from WHO, PAHO, and Ministries of Health. A geo-referenced database was created to map the historical presence of plague by country between the first registered case in 1899 and 2012. Areas where plague still persists were mapped at the second level of the political/administrative divisions (counties). Selected demographic, socioeconomic, and environmental variables were described.

Results

Plague was found to be present for one or more years in 14 out of 25 countries in Latin America (1899–2012). Foci persisted in six countries, two of which have no report of current cases. There is evidence that human cases of plague still persist in 18 counties. Demographic and poverty patterns were observed in 11/18 counties. Four types of biomes are most commonly found. 12/18 have an average altitude higher than 1,300 meters above sea level.

Discussion

Even though human plague cases are very localized, the risk is present, and unexpected outbreaks could occur. Countries need to make the final push to eliminate plague as a public health problem for the Americas. A further disaggregated risk evaluation is recommended, including identification of foci and possible interactions among areas where plague could emerge or re-emerge. A closer geographical approach and environmental characterization are suggested.     

Association between Age and Severity to Leptospirosis in Children

Background

In endemic areas, leptospirosis is more common and more severe in adults compared with children. Reasons to explain this discrepancy remain unclear and limited data focusing on adolescents are available. The objective of the study was to describe disease spectrum and outcome differences in children and adolescents admitted for leptospirosis in a large at-risk population.

Methods

Clinical and laboratory data were obtained on hospitalized cases in New Caledonia from 2006 to 2012.

Results

Data of 60 patients <18 years of age (25 children under 14 and 35 adolescents aged 14 to 17) with confirmed leptospirosis were analyzed. Compared with children, adolescents presented more often with classic features of Weil disease (p = 0.02), combining hepatic and renal involvement with or without pulmonary participation. Jarisch-Herxheimer reactions were observed more often among adolescents (p<0.01). The overall case fatality rate was low (1 adolescent versus 0 children).

Conclusion

Severe leptospirosis in adolescents may be more likely to show adults'' characteristics compared with children. Further studies are required to explore age-dependant host factors, including puberty-related physiological changes.     

Household transmission of leptospira infection in urban slum communities

Background

Leptospirosis, a spirochaetal zoonotic disease, is the cause of epidemics associated with high mortality in urban slum communities. Infection with pathogenic Leptospira occurs during environmental exposures and is traditionally associated with occupational risk activities. However, slum inhabitants reside in close proximity to environmental sources of contamination, suggesting that transmission during urban epidemics occurs in the household environment.

Methods and Findings

A survey was performed to determine whether Leptospira infection clustered within households located in slum communities in the city of Salvador, Brazil. Hospital-based surveillance identified 89 confirmed cases of leptospirosis during an outbreak. Serum samples were obtained from members of 22 households with index cases of leptospirosis and 52 control households located in the same slum communities. The presence of anti-Leptospira agglutinating antibodies was used as a marker for previous infection. In households with index cases, 22 (30%) of 74 members had anti-Leptospira antibodies, whereas 16 (8%) of 195 members from control households had anti-Leptospira antibodies. Highest titres were directed against L. interrogans serovars of the Icterohaemorrhagiae serogroup in 95% and 100% of the subjects with agglutinating antibodies from case and control households, respectively. Residence in a household with an index case of leptospirosis was associated with increased risk (OR 5.29, 95% CI 2.13–13.12) of having had a Leptospira infection. Increased infection risk was found for all age groups who resided in a household with an index case, including children <15 years of age (P = 0.008).

Conclusions

This study identified significant household clustering of Leptospira infection in slum communities where recurrent epidemics of leptospirosis occur. The findings support the hypothesis that the household environment is an important transmission determinant in the urban slum setting. Prevention therefore needs to target sources of contamination and risk activities which occur in the places where slum inhabitants reside.     

Unsuspected Leptospirosis Is a Cause of Acute Febrile Illness in Nicaragua

Background

Epidemic severe leptospirosis was recognized in Nicaragua in 1995, but unrecognized epidemic and endemic disease remains unstudied.

Methodology/Principal Findings

To determine the burden of and risk factors associated with symptomatic leptospirosis in Nicaragua, we prospectively studied patients presenting with fever at a large teaching hospital. Epidemiologic and clinical features were systematically recorded, and paired sera tested by IgM-ELISA to identify patients with probable and possible acute leptospirosis. Microscopic Agglutination Test and PCR were used to confirm acute leptospirosis. Among 704 patients with paired sera tested by MAT, 44 had acute leptospirosis. Patients with acute leptospirosis were more likely to present during rainy months and to report rural residence and fresh water exposure. The sensitivity of clinical impression and acute-phase IgM detected by ELISA were poor.

Conclusions/Significance

Leptospirosis is a common (6.3%) but unrecognized cause of acute febrile illness in Nicaragua. Rapid point-of-care tests to support early diagnosis and treatment as well as tests to support population-based studies to delineate the epidemiology, incidence, and clinical spectrum of leptospirosis, both ideally pathogen-based, are needed.     

Relative Risk of Visceral Leishmaniasis in Brazil: A Spatial Analysis in Urban Area

Background

Visceral leishmaniasis (VL) is a vector-borne disease whose factors involved in transmission are poorly understood, especially in more urban and densely populated counties. In Brazil, the VL urbanization is a challenge for the control program. The goals were to identify the greater risk areas for human VL and the risk factors involved in transmission.

Methodology

This is an ecological study on the relative risk of human VL. Spatial units of analysis were the coverage areas of the Basic Health Units (146 small-areas) of Belo Horizonte, Minas Gerais State, Brazil. Human VL cases, from 2007 to 2009 (n = 412), were obtained in the Brazilian Reportable Disease Information System. Bayesian approach was used to model the relative risk of VL including potential risk factors involved in transmission (canine infection, socioeconomic and environmental features) and to identify the small-areas of greater risk to human VL.

Principal Findings

The relative risk of VL was shown to be correlated with income, education, and the number of infected dogs per inhabitants. The estimates of relative risk of VL were higher than 1.0 in 54% of the areas (79/146). The spatial modeling highlighted 14 areas with the highest relative risk of VL and 12 of them are concentrated in the northern region of the city.

Conclusions

The spatial analysis used in this study is useful for the identification of small-areas according to risk of human VL and presents operational applicability in control and surveillance program in an urban environment with an unequal spatial distribution of the disease. Thus the frequent monitoring of relative risk of human VL in small-areas is important to direct and prioritize the actions of the control program in urban environment, especially in big cities.     

Using Structured Additive Regression Models to Estimate Risk Factors of Malaria: Analysis of 2010 Malawi Malaria Indicator Survey Data

Background

After years of implementing Roll Back Malaria (RBM) interventions, the changing landscape of malaria in terms of risk factors and spatial pattern has not been fully investigated. This paper uses the 2010 malaria indicator survey data to investigate if known malaria risk factors remain relevant after many years of interventions.

Methods

We adopted a structured additive logistic regression model that allowed for spatial correlation, to more realistically estimate malaria risk factors. Our model included child and household level covariates, as well as climatic and environmental factors. Continuous variables were modelled by assuming second order random walk priors, while spatial correlation was specified as a Markov random field prior, with fixed effects assigned diffuse priors. Inference was fully Bayesian resulting in an under five malaria risk map for Malawi.

Results

Malaria risk increased with increasing age of the child. With respect to socio-economic factors, the greater the household wealth, the lower the malaria prevalence. A general decline in malaria risk was observed as altitude increased. Minimum temperatures and average total rainfall in the three months preceding the survey did not show a strong association with disease risk.

Conclusions

The structured additive regression model offered a flexible extension to standard regression models by enabling simultaneous modelling of possible nonlinear effects of continuous covariates, spatial correlation and heterogeneity, while estimating usual fixed effects of categorical and continuous observed variables. Our results confirmed that malaria epidemiology is a complex interaction of biotic and abiotic factors, both at the individual, household and community level and that risk factors are still relevant many years after extensive implementation of RBM activities.     

Seroprevalence of Alphavirus Antibodies in a Cross-Sectional Study in Southwestern Tanzania Suggests Endemic Circulation of Chikungunya

Background

To date, Alphavirus infections and their most prominent member, chikungunya fever, a viral disease which first became apparent in Tanzania in 1953, have been very little investigated in regions without epidemic occurrence. Few data exist on burden of disease and socio-economic and environmental covariates disposing to infection.

Methods

A cross-sectional seroprevalence study was undertaken in 1,215 persons from Mbeya region, South-Western Tanzania, to determine the seroprevalence of anti-Alphavirus IgG antibodies, and to investigate associated risk factors.

Results

18% of 1,215 samples were positive for Alphavirus IgG. Seropositivity was associated with participant age, low to intermediate elevation, flat terrain and with IgG positivity for Rift Valley fever, Flaviviridae, and rickettsiae of the spotted fever group. When comparing the geographical distribution of Alphavirus seropositivity to that of Rift Valley fever, it was obvious that Alphaviruses had spread more widely throughout the study area, while Rift Valley fever was concentrated along the shore of Lake Malawi.

Conclusion

Alphavirus infections may contribute significantly to the febrile disease burden in the study area, and are associated with several arthropod-borne infections. Their spread seems only limited by factors affecting mosquitoes, and seems less restricted than that of Rift Valley fever.     

Men Traveling Away from Home Are More Likely to Bring Malaria into High Altitude Villages,Northwest Ethiopia

Background

Information about malaria risk factors at high altitudes is scanty. Understanding the risk factors that determine the risk of malaria transmission at high altitude villages is important to facilitate implementing sustainable malaria control and prevention programs.

Methods

An unmatched case control study was conducted among patients seeking treatment at health centers in high altitude areas. Either microscopy or rapid diagnostic tests were used to confirm the presence of plasmodium species. A generalized linear model was used to identify the predictors of malaria transmission in high altitude villages.

Results

Males (AOR = 3.11, 95%CI: 2.28, 4.23), and those who traveled away from the home in the previous month (AOR = 2.01, 95% CI: 1.56, 2.58) were strongly associated with presence of malaria in high altitude villages. Other significant factors, including agriculture in occupation (AOR = 1.41, 95% CI: 1.05, 1.93), plants used for fencing (AOR = 1.70, 95% CI: 1.18, 2.52) and forests near the house (AOR = 1.60, 95% CI: 1.15, 2.47), were found predictors for malaria in high altitude villages.

Conclusion

Travel outside of their home was an important risk of malaria infections acquisition. Targeting males who frequently travel to malarious areas can reduce malaria transmission risks in high altitude areas.     

Leptospirosis in Rio Grande do Sul,Brazil: An Ecosystem Approach in the Animal-Human Interface

Background

Leptospirosis is an epidemic-prone neglected disease that affects humans and animals, mostly in vulnerable populations. The One Health approach is a recommended strategy to identify drivers of the disease and plan for its prevention and control. In that context, the aim of this study was to analyze the distribution of human cases of leptospirosis in the State of Rio Grande do Sul, Brazil, and to explore possible drivers. Additionally, it sought to provide further evidence to support interventions and to identify hypotheses for new research at the human-animal-ecosystem interface.

Methodology and findings

The risk for human infection was described in relation to environmental, socioeconomic, and livestock variables. This ecological study used aggregated data by municipality (all 496). Data were extracted from secondary, publicly available sources. Thematic maps were constructed and univariate analysis performed for all variables. Negative binomial regression was used for multivariable statistical analysis of leptospirosis cases. An annual average of 428 human cases of leptospirosis was reported in the state from 2008 to 2012. The cumulative incidence in rural populations was eight times higher than in urban populations. Variables significantly associated with leptospirosis cases in the final model were: Parana/Paraiba ecoregion (RR: 2.25; CI_95%: 2.03–2.49); Neossolo Litolítico soil (RR: 1.93; CI_95%: 1.26–2.96); and, to a lesser extent, the production of tobacco (RR: 1.10; CI_95%: 1.09–1.11) and rice (RR: 1.003; CI_95%: 1.002–1.04).

Conclusion

Urban cases were concentrated in the capital and rural cases in a specific ecoregion. The major drivers identified in this study were related to environmental and production processes that are permanent features of the state. This study contributes to the basic knowledge on leptospirosis distribution and drivers in the state and encourages a comprehensive approach to address the disease in the animal-human-ecosystem interface.     

Cytokine Response Signatures in Disease Progression and Development of Severe Clinical Outcomes for Leptospirosis

Background

The role of the immune response in influencing leptospirosis clinical outcomes is not yet well understood. We hypothesized that acute-phase serum cytokine responses may play a role in disease progression, risk for death, and severe pulmonary hemorrhage syndrome (SPHS).

Methodology/Principal Findings

We performed a case-control study design to compare cytokine profiles in patients with mild and severe forms of leptospirosis. Among patients hospitalized with severe disease, we compared those with fatal and nonfatal outcomes. During active outpatient and hospital-based surveillance we prospectively enrolled 172 patients, 23 with mild disease (outpatient) and 149 with severe leptospirosis (hospitalized). Circulating concentrations of pro- and anti-inflammatory cytokines at the time of patient presentation were measured using a multiplex bead array assay. Concentrations of IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-17A, and TNF-α were significantly higher (P<0.05) in severe disease compared to mild disease. Among severe patients, levels of IL-6 (P<0.001), IL-8 (P = 0.0049) and IL-10 (P<0.001), were higher in fatal compared to non-fatal cases. High levels of IL-6 and IL-10 were independently associated (P<0.05) with case fatality after adjustment for age and days of symptoms. IL-6 levels were higher (P = 0.0519) among fatal cases who developed SPHS than among who did not.

Conclusion/Significance

This study shows that severe cases of leptospirosis are differentiated from mild disease by a “cytokine storm” process, and that IL-6 and IL-10 may play an immunopathogenic role in the development of life-threatening outcomes in human leptospirosis.     

Comparison of Human and Animal Surveillance Data for H5N1 Influenza A in Egypt 2006–2011

Background

The majority of emerging infectious diseases are zoonotic (transmissible between animals and humans) in origin, and therefore integrated surveillance of disease events in humans and animals has been recommended to support effective global response to disease emergence. While in the past decade there has been extensive global surveillance for highly pathogenic avian influenza (HPAI) infection in both animals and humans, there have been few attempts to compare these data streams and evaluate the utility of such integration.

Methodology

We compared reports of bird outbreaks of HPAI H5N1 in Egypt for 2006–2011 compiled by the World Organisation for Animal Health (OIE) and the UN Food and Agriculture Organization (FAO) EMPRESi reporting system with confirmed human H5N1 cases reported to the World Health Organization (WHO) for Egypt during the same time period.

Principal Findings

Both human cases and bird outbreaks showed a cyclic pattern for the country as a whole, and there was a statistically significant temporal correlation between the data streams. At the governorate level, the first outbreak in birds in a season usually but not always preceded the first human case, and the time lag between events varied widely, suggesting regional differences in zoonotic risk and/or surveillance effectiveness. In a multivariate risk model, lower temperature, lower urbanization, higher poultry density, and the recent occurrence of a bird outbreak were associated with increased risk of a human case of HPAI in the same governorate, although the positive predictive value of a bird outbreak was low.

Conclusions

Integrating data streams of surveillance for human and animal cases of zoonotic disease holds promise for better prediction of disease risk and identification of environmental and regional factors that can affect risk. Such efforts can also point out gaps in human and animal surveillance systems and generate hypotheses regarding disease transmission.     

The Jarisch-Herxheimer Reaction in Leptospirosis: A Systematic Review

Background

Leptospirosis is an endemo-epidemic zoonotic disease associated with potentially fatal renal, cardiovascular or pulmonary failure. Recommended treatment includes antibiotics, which may induce a Jarisch-Herxheimer reaction (JHR). Since little information on the importance of this adverse event is available, we performed this review to quantify frequency and impact of JHR in leptospirosis management.

Methodology/Principal Findings

This review systematically summarizes the literature on the JHR in leptospirosis. To approach the broader aspects of the subject, articles considering the treatment of leptospirosis, national leptospirosis guidelines and textbook and technical reports of the World Health Organisation were reviewed. Publications describing JHR in leptospirosis are very limited and consist mainly of single case reports and small case series. A single randomized control trial specifically assessed the JHR occurrence, but it has never been systematically investigated in large trials. Not all guidelines and not all literature on leptospirosis mention this reaction which can be fatal.

Conclusions/Significance

Although generally assumed to be a rare event, the true prevalence of JHR in leptospirosis is unknown and the awareness of this event is insufficient. All leptospirosis guidelines and local leptospirosis protocols should stress on systematic monitoring for clinical status early after antibiotic administration. Large well designed studies are required to precise the incidence and the impact of JHR as well as the severity and rates between various antibiotics.     

A comparative study of leptospirosis and dengue in Thai children

Background

Leptospirosis is an emerging zoonosis that is often under-recognized in children and commonly confused with dengue in tropical settings. An enhanced ability to distinguish leptospirosis from dengue in children would guide clinicians and public health personnel in the appropriate use of limited healthcare resources.

Methodology/Principal Findings

We conducted a prospective, hospital-based, study of children with acute febrile illnesses and dengue in Thailand. Among the children without dengue, we identified those with leptospirosis using anti-leptospira IgM and microscopic agglutination titers in paired acute and convalescent blood samples. We then performed a case-control comparison of symptoms, signs, and clinical laboratory values between children with leptospirosis and dengue.In a semi-rural region of Thailand, leptospirosis accounted for 19% of the non-dengue acute febrile illnesses among children presenting during the rainy season. None of the children with leptospirosis were correctly diagnosed at the time of hospital discharge, and one third (33%) were erroneously diagnosed as dengue or scrub typhus. A predictive model to distinguish pediatric leptospirosis from dengue was generated using three variables: the absolute neutrophil count, plasma albumin, and aspartate aminotransferase levels in the first 72 hours of illness.

Conclusions/Significance

Unrecognized leptospirosis can be a significant cause of “dengue-like” febrile illness in children. Increased awareness of pediatric leptospirosis, and an enhanced ability to discriminate between leptospirosis and dengue early in illness, will help guide the appropriate use of healthcare resources in often resource-limited settings.     

How Well Are Malaria Maps Used to Design and Finance Malaria Control in Africa?

Introduction

Rational decision making on malaria control depends on an understanding of the epidemiological risks and control measures. National Malaria Control Programmes across Africa have access to a range of state-of-the-art malaria risk mapping products that might serve their decision-making needs. The use of cartography in planning malaria control has never been methodically reviewed.

Materials and Methods

An audit of the risk maps used by NMCPs in 47 malaria endemic countries in Africa was undertaken by examining the most recent national malaria strategies, monitoring and evaluation plans, malaria programme reviews and applications submitted to the Global Fund. The types of maps presented and how they have been used to define priorities for investment and control was investigated.

Results

91% of endemic countries in Africa have defined malaria risk at sub-national levels using at least one risk map. The range of risk maps varies from maps based on suitability of climate for transmission; predicted malaria seasons and temperature/altitude limitations, to representations of clinical data and modelled parasite prevalence. The choice of maps is influenced by the source of the information. Maps developed using national data through in-country research partnerships have greater utility than more readily accessible web-based options developed without inputs from national control programmes. Although almost all countries have stratification maps, only a few use them to guide decisions on the selection of interventions allocation of resources for malaria control.

Conclusion

The way information on the epidemiology of malaria is presented and used needs to be addressed to ensure evidence-based added value in planning control. The science on modelled impact of interventions must be integrated into new mapping products to allow a translation of risk into rational decision making for malaria control. As overseas and domestic funding diminishes, strategic planning will be necessary to guide appropriate financing for malaria control.     

Increasing Trends of Leptospirosis in Northern India: A Clinico-Epidemiological Study

Background

Leptospirosis, a zoonosis associated with potentially fatal consequences, has long been a grossly underreported disease in India. There is no accurate estimate of the problem of leptospirosis in non-endemic areas such as north India.

Methods/Principal Findings

In order to understand the clinical spectrum and risk factors associated with leptospirosis, we carried out a retrospective study in patients with acute febrile illness in north India over the last 5 years (January 2004 to December 2008). There was increased incidence of leptospirosis (11.7% in 2004 to 20.5% in 2008) as diagnosed by IgM ELISA and microscopic agglutination titer in paired acute and convalescent sera. The disease showed a peak during the rainy season (August and September). We followed up 86 cases of leptospirosis regarding their epidemiological pattern, clinical features, laboratory parameters, complications, therapy, and outcome. Mean age of patients was 32.6 years (2.5 years to 78 years) and males (57%) outnumbered females (43%). Infestation of dwellings with rats (53.7%), working in farm lands (44.2%), and contact with animals (62.1%) were commonly observed epidemiological risk factors. Outdoor workers including farmers (32.6%), labourers (11.6%), para-military personnel (2.3%), and sweepers (1.2%) were commonly affected. Modified Faine''s criteria could diagnose 76 cases (88.3%). Renal failure (60.5%), respiratory failure (20.9%), the neuroleptospirosis (11.6%), and disseminated intravascular coagulation (DIC) (11.6%) were the commonest complications. Five patients died, giving a case fatality rate of 5.9%.

Conclusions/Significance

There has been a rapid rise in the incidence of leptospirosis in north India. Severe complications such as renal failure, respiratory failure, neuroleptospirosis, and DIC are being seen with increasing frequency. Increased awareness among physicians, and early diagnosis and treatment, may reduce mortality due to leptospirosis.     

Detection of Avian Influenza A(H7N9) Virus from Live Poultry Markets in Guangzhou,China: A Surveillance Report

Purpose

A virologic surveillance program for A(H7N9) virus was conducted from April 15, 2013 to February 14, 2014 in Guangzhou, aiming to clarify the geographical distribution of A(H7N9) viruses among live poultry markets (LPMs) and poultry farms in Guangzhou. Virological and serological surveys of poultry workers were also conducted to evaluate the risk of poultry-to-human transmission of the A(H7N9) virus.

Methods

36 retail LPMs, 6 wholesale LPMs and 8 poultry farms were involved in our surveillance program. About 20 live poultry and environmental samples were obtained from each surveillance site at every sampling time. Different environmental samples were collected to represent different poultry-related work activities. RT-PCR and virus culture were performed to identify the A(H7N9) virus. Hemagglutinin inhibition assay and RT-PCR were conducted to detect possible A(H7N9) infection among poultry workers.

Results

A total of 8900 live poultry and environmental samples were collected, of which 131(1.5%) were tested positive for A(H7N9) virus. 44.4% (16/36) of retail LPMs and 50.0% (3/6) of wholesale LPMs were confirmed to be contaminated. No positive samples was detected from poultry farms. A significant higher positive sample rate was found in environmental samples related to poultry selling (2.6%) and slaughtering (2.4%), compared to poultry holding (0.9%). Correspondingly, A(H7N9) viruses were isolated most frequently from slaughter zone. In addition, 316 poultry workers associated with the 19 contaminated-LPMs were recruited and a low seroprevalence (1.6%) of antibody against A(H7N9) virus was detected. An asymptomatic A(H7N9) infection was also identified by RT-PCR.

Conclusions

Our study highlights the importance of conducting effective surveillance for A(H7N9) virus and provides evidence to support the assumption that slaughtering is the key process for the propagation of A(H7N9) virus in retail LPMs. Moreover, the ability of A(H7N9) virus to cross species barrier is proved to be still limited.     

Inter-epidemic Transmission of Rift Valley Fever in Livestock in the Kilombero River Valley,Tanzania: A Cross-Sectional Survey

Background

In recent years, evidence of Rift Valley fever (RVF) transmission during inter-epidemic periods in parts of Africa has increasingly been reported. The inter-epidemic transmissions generally pass undetected where there is no surveillance in the livestock or human populations. We studied the presence of and the determinants for inter-epidemic RVF transmission in an area experiencing annual flooding in southern Tanzania.

Methodology

A cross-sectional sero-survey was conducted in randomly selected cattle, sheep and goats in the Kilombero river valley from May to August 2011, approximately four years after the 2006/07 RVF outbreak in Tanzania. The exposure status to RVF virus (RVFV) was determined using two commercial ELISA kits, detecting IgM and IgG antibodies in serum. Information about determinants was obtained through structured interviews with herd owners.

Findings

An overall seroprevalence of 11.3% (n = 1680) was recorded; 5.5% in animals born after the 2006/07 RVF outbreak and 22.7% in animals present during the outbreak. There was a linear increase in prevalence in the post-epidemic annual cohorts. Nine inhibition-ELISA positive samples were also positive for RVFV IgM antibodies indicating a recent infection. The spatial distribution of seroprevalence exhibited a few hotspots. The sex difference in seroprevalence in animals born after the previous epidemic was not significant (6.1% vs. 4.6% for females and males respectively, p = 0.158) whereas it was significant in animals present during the outbreak (26.0% vs. 7.8% for females and males respectively, p<0.001). Animals living >15 km from the flood plain were more likely to have antibodies than those living <5 km (OR 1.92; 95% CI 1.04–3.56). Species, breed, herd composition, grazing practices and altitude were not associated with seropositivity.

Conclusion

These findings indicate post-epidemic transmission of RVFV in the study area. The linear increase in seroprevalence in the post-epidemic annual cohorts implies a constant exposure and presence of active foci transmission preceding the survey.