Risk factors for severe leptospirosis in the parish of St. Andrew, Barbados

Leptospira infection and shedding in dogs in Thailand

BACKGROUND

Leptospirosis is a widespread zoonosis and has been recognized as a re-emerging infectious disease in humans and dogs, but prevalence of Leptospira shedding in dogs in Thailand is unknown. The aim of this study was to determine urinary shedding of Leptospira in dogs in Thailand, to evaluate antibody prevalence by microscopic agglutination test (MAT) and enzyme-linked immunosorbent assay (ELISA), and to assess risk factors for Leptospira infection. In Northern, Northeastern, and Central Thailand, 273 stray (n = 119) or client-owned (n = 154) dogs from rural (n = 139) or urban (n = 134) areas were randomly included. Dogs that had received antibiotics within 4 weeks prior to sampling were excluded. No dog had received vaccination against Leptospira. Urine was evaluated by real-time polymerase chain reaction (PCR) specific for lipL32 gene of pathogenic Leptospira. Additionally, urine was cultured for 6 months in Ellinghausen-McCullough-Johnson-Harris (EMJH) medium. Antibodies were measured by ELISA and MAT against 24 serovars belonging to 15 serogroups and 1 undesignated serogroup. Risk factor analysis was performed with backwards stepwise selection based on Wald.

RESULTS

Twelve of 273 (4.4%; 95% confidence interval (CI): 2.0-6.8%) urine samples were PCR-positive. In 1/273 dogs (0.4%; 95% CI: 0.01-1.1%) Leptospira could be cultured from urine. MAT detected antibodies in 33/273 dogs (12.1%; 95% CI: 8.2-16.0%) against 19 different serovars (Anhoa, Australis, Ballum, Bataviae, Bratislava, Broomi, Canicola, Copenhageni, Coxi, Grippotyphosa, Haemolytica, Icterohaemorrhagiae, Khorat, Paidjan, Patoc, Pyrogenes, Rachmati, Saxkoebing, Sejroe). In 111/252 dogs (44.0%; 95% CI: 37.9-50.2%) immunoglobulin M (IgM) and/or immunoglobulin G (IgG) antibodies were found by ELISA. Female dogs had a significantly higher risk for Leptospira infection (p = 0.023).

CONCLUSIONS

Leptospira shedding occurs in randomly sampled dogs in Thailand, with infection rates comparable to those of Europe and the USA. Therefore, the potential zoonotic risk should not be underestimated and use of Leptospira vaccines are recommended.

Leptospira seroprevalence in owned dogs from Spain

Leptospira is a widespread zoonosis that has been linked to transmission between dogs and humans. The main purposes were to determine the seroprevalence of anti-Leptospira serum antibody and to identify the most common serovars in dogs in Spain. This is a cross-sectional study with 1,310 records of canine Leptospira testing data from Spain since 2015 to 2017. Inclusion criteria were individual cases with MAT test results for 8 serovars (Bratislava, Icterohaemorrhagiae, Australis, Pomona, Grippotyphosa, Autumnalis, Canicola and Saxkoebing) and to have the zip code data. Three hundred and thirty-eight samples (25.8%; 95%CI 23.6–28.4) were seropositive (≥1:100). According to geographic areas, North had the highest seroprevalence (38.0%; 95%CI 28.9–47.1) followed by South (29.4%; 95%CI 20.1–38.8), Center (28.6%; 95%CI 24.3–33.0), Mediterranean (22.3%; 95%CI 19.1–25.6) and Northwest (22.2%; 95%CI 7.9–36.4). Seropositivity (MAT ≥1:100) was most common to serovars Icterohaemorrhagiae (19.4%; 95%CI 17.2–21.5) and Bratislava (8.5%; 95%CI 7.0–10.0), followed by Grippotyphosa (7.2%; 95%CI 5.8–8.6), Australis (6.4%; 95%CI 5.0–7.7), Autumnalis (5.0%; 95%CI 3.8–6.2), Pomona (4.5%; 95%CI 3.3–5.6), Canicola (3.4%; 95%CI 2.4–4.4) and Saxkoebing (0.8%; 95%CI 0.3–1.3). An association was found between positivity (MAT ≥1:100) and males (P = 0.003) and dogs that were 6 years old or older were at higher risk of exposure (P = 0.001; OR 4.61; 95%CI 1.86–11.43). This study has shown that dogs in Spain are commonly exposed to Leptospira infection and points out the necessity to control the prevalence of this severe widespread zoonosis in dogs and humans.

Risk factors associated with leptospirosis in swine in state of Pernambuco, Brazil

ABSTRACT: Leptospirosis is a major public health threat, and swine are one of the most important reservoirs and sources of Leptospira infection for man. The aim of this study was to investigate the epidemiological situation of leptospirosis in swine in the state of Pernambuco, Brazil. Blood samples from 265 swine were collected and tested by the microscopic agglutination test (MAT), and an epidemiological form containing questions about animal production characteristics, reproductive management, and sanitary and hygiene aspects of the herd was applied to evaluate infection risk factors. The data were analyzed by means of a logistic regression model. An occurrence of 53.1% (143/265) of swine positives to Leptospira spp. was observed. The most commons serovars were Icterohaemorrhagiae (39.1%), Pomona (25.9%), and Shermani (14.0%). Factors associated with the infection were stagnant water source (p = 0.034, odds ratio - OR = 2.29; confidence interval of 95% - 95%CI 1.06-4.93), farms where the healthy animals are bred with sick ones (OR = 1.69; 95%CI 1.04-2.75), and the properties with flooded areas (OR = 1.65; 95%CI 1.01-2.68). The risk factors found in this study played an important role in the agent dissemination and should be avoided in a way to control the disease in the herds studied.

Peptide specific monoclonal antibodies of Leptospiral LigA for acute diagnosis of leptospirosis

Leptospirosis is underdiagnosed due to low sensitivity, need of specialised equipment, and expensive reagents for serological and molecular diagnosis respectively. Considering the sensitivity, rapidity, inexpensive reagents and collection of clinical samples, the monoclonal antibody based antigen detection method from urine samples has been developed and evaluated. LigA (LK90) based B-cell specific epitopes were predicted and synthesised as peptides for the production of monoclonal antibody. LK90₅₄₃: SNAQKNQGNA (amino acids: 543 to 552), and LK90₁₁₁₀: DHHTQSSYTP (amino acids: 1110 to 1119) with VaxiJen score of 1.3719 and 1.2215, respectively were used. Thirty two and 28 urine samples from confirmed and seronegative healthy human subjects, respectively were included for the evaluation of MAb-based dot blot ELISA. The specificity of the evaluated MAbs, P1B1 and P4W2 were found to be in the range of ~93–96%. Moreover, the MAbs did not show cross-reactivity with other bacterial antigens as confirmed by IgG ELISA, further validating its specificity for leptospiral antigens. These findings suggest that the developed MAb based dot blot ELISA is a simple, rapid performed in less than 8 h, inexpensive with a ICER of $8.7/QALY, and affordable in developing countries and area where laboratory facilities are limited.

Estimating the Burden of Leptospirosis among Febrile Subjects Aged below 20 Years in Kampong Cham Communities, Cambodia, 2007-2009

BACKGROUND

Leptospirosis is an emerging but neglected public health challenge in the Asia/Pacific Region with an annual incidence estimated at 10-100 per 100,000 population. No accurate data, however, are available for at-risk rural Cambodian communities.

METHOD

We conducted anonymous, unlinked testing for IgM antibodies to Leptospira spp. on paired sera of Cambodian patients <20 years of age between 2007-2009 collected through active, community-based surveillance for febrile illnesses in a convenience sample of 27 rural and semi-rural villages in four districts of Kampong Cham province, Cambodia. Leptospirosis testing was done on paired serological samples negative for Dengue, Japanese encephalitis and Chikungunya viruses after random selection. Convalescent samples found positive while initial samples were negative were considered as proof of acute infection. We then applied a mathematical model to estimate the risk of fever caused by leptospirosis, dengue or other causes in rural Cambodia.

RESULTS

A total of 630 samples are coming from a randomly selected subset of 2358 samples. IgM positive were found on the convalescent serum sample, among which 100 (15.8%) samples were IgM negative on an earlier sample. Seventeen of these 100 seroconversions were confirmed using a Microagglutination Test. We estimated the probability of having a fever due to leptospirosis at 1. 03% (95% Credible Interval CI: 0. 95%-1. 22%) per semester. In comparison, this probability was 2. 61% (95% CI: 2. 55%, 2. 83%) for dengue and 17. 65% (95% CI: 17. 49%, 18. 08%) for other causes.

CONCLUSION

Our data from febrile cases aged below 20 years suggest that the burden of leptospirosis is high in rural Cambodian communities. This is especially true during the rainy season, even in the absence of identified epidemics.

Association between footwear use and neglected tropical diseases: a systematic review and meta-analysis

BACKGROUND

The control of neglected tropical diseases (NTDs) has primarily focused on preventive chemotherapy and case management. Less attention has been placed on the role of ensuring access to adequate water, sanitation, and hygiene and personal preventive measures in reducing exposure to infection. Our aim was to assess whether footwear use was associated with a lower risk of selected NTDs.

METHODOLOGY

We conducted a systematic review and meta-analysis to assess the association between footwear use and infection or disease for those NTDs for which the route of transmission or occurrence may be through the feet. We included Buruli ulcer, cutaneous larva migrans (CLM), leptospirosis, mycetoma, myiasis, podoconiosis, snakebite, tungiasis, and soil-transmitted helminth (STH) infections, particularly hookworm infection and strongyloidiasis. We searched Medline, Embase, Cochrane, Web of Science, CINAHL Plus, and Popline databases, contacted experts, and hand-searched reference lists for eligible studies. The search was conducted in English without language, publication status, or date restrictions up to January 2014. Studies were eligible for inclusion if they reported a measure of the association between footwear use and the risk of each NTD. Publication bias was assessed using funnel plots. Descriptive study characteristics and methodological quality of the included studies were summarized. For each study outcome, both outcome and exposure data were abstracted and crude and adjusted effect estimates presented. Individual and summary odds ratio (OR) estimates and corresponding 95% confidence intervals (CIs) were calculated as a measure of intervention effect, using random effects meta-analyses.

PRINCIPAL FINDINGS

Among the 427 studies screened, 53 met our inclusion criteria. Footwear use was significantly associated with a lower odds of infection of Buruli ulcer (OR=0.15; 95% CI: 0.08-0.29), CLM (OR=0.24; 95% CI: 0.06-0.96), tungiasis (OR=0.42; 95% CI: 0.26-0.70), hookworm infection (OR=0.48; 95% CI: 0.37-0.61), any STH infection (OR=0.57; 95% CI: 0.39-0.84), strongyloidiasis (OR=0.56; 95% CI: 0.38-0.83), and leptospirosis (OR=0.59; 95% CI: 0.37-0.94). No significant association between footwear use and podoconiosis (OR=0.63; 95% CI: 0.38-1.05) was found and no data were available for mycetoma, myiasis, and snakebite. The main limitations were evidence of heterogeneity and poor study quality inherent to the observational studies included.

CONCLUSIONS/SIGNIFICANCE

Our results show that footwear use was associated with a lower odds of several different NTDs. Access to footwear should be prioritized alongside existing NTD interventions to ensure a lasting reduction of multiple NTDs and to accelerate their control and elimination.

PROTOCOL REGISTRATION

PROSPERO International prospective register of systematic reviews CRD42012003338.

Characteristics of rural leptospirosis patients admitted to referral hospitals during the 2008 leptospirosis outbreak in Sri Lanka: implications for developing public health control measures

To determine the exposure risk factors of highly endemic rural leptospirosis in tropical setting, we conducted a prospective, hospital-based case control study in Sri Lanka. A conceptual hierarchy of variables was used to analyze the data. Case patients included 38 (34%) females and 73 (66%) males with a mean age of 36 yr (SD 12.7 yr). Using piped, chlorinated water for drinking/general purposes (odds ratio [OR] 0.33, 95% confidence interval [CI] 0.16-0.67), paddy fields in the vicinity of home (OR 1.77, 95% CI 1.06-2.97), sighting dogs at home yard/dog ownership (OR 1.79, 95% CI 1.11-2.91), sighting cattle at home yard/cattle ownership (OR 1.69, 95% CI 1.00-2.84), and work in a paddy field (OR 3.02, 95% CI 1.68, 5.41) were the main predictors of leptospirosis among febrile patients. In high endemic tropical settings with rural leptospirosis, risk factors in residential environments, rather than individual exposures, seemed to play a major role in leptospirosis disease transmission.

Ameboma: an unusual cause of gastrointestinal bleeding during severe leptospirosis

Background

Severe leptospirosis occurs mainly in a tropical environment and includes icterus, acute renal failure and hemorrhages. These bleedings, which are mainly a consequence of acute homeostatic disturbances, can also reveal simultaneous diseases. Coinfections with other tropical diseases have been previously reported during leptospirosis. To our knowledge, invasive amebiasis, which can induce gastrointestinal bleedings, has never been described in the course of severe leptospirosis.

Case presentation

In this report, we describe a case of a 60 year-old man living in Reunion Island (Indian Ocean, France) admitted to our intensive care unit for severe Leptospira interrogans serovar icterohaemorrhagiae infection with neurological, renal, liver and hematological involvement. Two lower gastrointestinal bleedings occurred 7 and 15 days after admission. The first episode was promoted by hemostatic disturbances while the second bleeding occurred during low-dose heparin therapy. Colonoscopy revealed a pseudo-tumoral inflammatory mass of the recto-sigmoid junction. Histological examination found trophozoites inside mucinous exudate suggestive of Entamoeba histolytica. Amoebic serology was strongly positive whereas careful detection of cysts or trophozoites on saline-wet mount was negative in three consecutive samples of stools. Amoxicillin followed by metronidazole therapy, combined with supportive care, led to an improvement in the clinical and biological patient’s condition and endoscopic appearances.

Conclusion

Clinicians should be aware that gastrointestinal bleeding during severe leptospirosis could not solely be the consequences of hemostatic disturbances. Careful endoscopic evaluation that may reveal curable coinfections should also be considered.

Though not reservoirs, dogs might transmit Leptospira in New Caledonia

Leptospira has been a major public health concern in New Caledonia for decades. However, few multidisciplinary studies addressing the zoonotic pattern of this disease were conducted so far. Here, pig, deer and dog samples were collected. Analyses were performed using molecular detection and genotyping. Serological analyses were also performed for dogs. Our results suggest that deer are a reservoir of L. borgpetersenii Hardjobovis and pigs a reservoir of L. interrogans Pomona. Interestingly, 4.4% of dogs were renal carriers of Leptospira. In dog populations, MAT results confirmed the circulation of the same Leptospira serogroups involved in human cases. Even if not reservoirs, dogs might be of significance in human contamination by making an epidemiological link between wild or feral reservoirs and humans. Dogs could bring pathogens back home, shedding Leptospira via their urine and in turn increasing the risk of human contamination. We propose to consider dog as a vector, particularly in rural areas where seroprevalence is significantly higher than urban areas. Our results highlight the importance of animal health in improving leptospirosis prevention in a One Health approach.

Risk Factors for Leptospirosis Infection in Humans and Implications for Public Health Intervention in Indonesia and the Asia-Pacific Region

Prevention and control of leptospirosis require an understanding of risk factors. This review identifies risk factors associated with leptospirosis infection from countries in the Asia-Pacific region, and compares and contrasts these data with those available from Indonesia. MEDLINE, PubMed, and Scopus databases were used to search for relevant articles. Indonesian gray literature was searched for leptospirosis risk factor studies in Indonesia. A total of 34 articles were included in this review. The contrast between peer-reviewed publications and Indonesian gray literature revealed that the variety of risk factors associated with leptospirosis infection is region or area specific. The presence of skin wounds, the existence of rodents, especially rats, and activities related to contact with contaminated surface water are factors frequently reported to have significant association with leptospirosis infection in human in Indonesia and in other Asia-Pacific countries.

Emergence of novel Leptospira serovars: a need for adjusting vaccination policies for dogs?

A total of 855 sera from dogs in Greece were tested for antibodies to strains belonging to the Pomona, Grippotyphosa and Australis serogroups of Leptospira to assess exposure levels to these serogroups, possible associations with clinical disease and to evaluate whether these findings support the inclusion of additional serovars in dog vaccines. Antibodies were detected in 110 (12·9%) dogs. The highest seroprevalence (4·9%) was to the proposed novel serovar Altodouro belonging to the Pomona serogroup. This serovar also showed a statistically significant association with clinical disease. Serovar Bratislava antibodies were found in 3·4% of sera. Consideration should be given to the inclusion of serovars belonging to the Pomona serogroup and serovar Bratislava in future dog vaccines for the Greek market.

Seasonality of human leptospirosis in Reunion Island (Indian Ocean) and its association with meteorological data

Background

Leptospirosis is a disease which occurs worldwide but particularly affects tropical areas. Transmission of the disease is dependent on its excretion by reservoir animals and the presence of moist environment which allows the survival of the bacteria.

Methods and Findings

A retrospective study was undertaken to describe seasonal patterns of human leptospirosis cases reported by the Centre National de Références des Leptospiroses (CNRL, Pasteur Institute, Paris) between 1998 and 2008, to determine if there was an association between the occurrence of diagnosed cases and rainfall, temperature and global solar radiation (GSR). Meteorological data were recorded in the town of Saint-Benoît (Météo France “Beaufonds-Miria” station), located on the windward (East) coast. Time-series analysis was used to identify the variables that best described and predicted the occurrence of cases of leptospirosis on the island. Six hundred and thirteen cases were reported during the 11-year study period, and 359 cases (58.56%) were diagnosed between February and May. A significant correlation was identified between the number of cases in a given month and the associated cumulated rainfall as well as the mean monthly temperature recorded 2 months prior to diagnosis (r = 0.28 and r = 0.23 respectively). The predictive model includes the number of cases of leptospirosis recorded 1 month prior to diagnosis (b = 0.193), the cumulated monthly rainfall recorded 2 months prior to diagnosis (b = 0.145), the average monthly temperature recorded 0 month prior to diagnosis (b = 3.836), and the average monthly GSR recorded 0 month prior to diagnosis (b = −1.293).

Conclusions

Leptospirosis has a seasonal distribution in Reunion Island. Meteorological data can be used to predict the occurrence of the disease and our statistical model can help to implement seasonal prevention measures.

Determinants of leptospirosis in Sri Lanka: study protocol

Background

Leptospirosis is becoming a major public health threat in Sri Lanka as well as in other countries. We designed a case control study to determine the factors associated with local transmission of leptospirosis in Sri Lanka, in order to identify major modifiable determinants of leptospirosis. The purpose of this paper is to describe the study protocol in detail prior to the publishing of the study results, so that the readership will be able to understand and interpret the study results effectively.

Methods

A hospital based partially matched case control design is proposed. The study will be conducted in three selected leptospirosis endemic districts in central Sri Lanka. Case selection will include screening all acute fever patients admitted to selected wards to select probable cases of leptospirosis and case confirmation using an array of standard laboratory criteria. Age and sex matched group of acute fever patients with other confirmed diagnosis will be used as controls. Case to control ratio will be 1:2. A minimum sample of 144 cases is required to detect 20% exposure with 95% two sided confidence level and 80% power. A pre tested interviewer administered structured questionnaire will be used to collect data from participants. Variables included in the proposed study will be evaluated using conceptual hierarch of variables in three levels; Exposure variables as proximal; reservoir and environmental variables as intermediate; socio-demographic variables as distal. This conceptual hierarch hypothesised that the distal and intermediate variables are mediated through the proximal variables but not directly. A logistic regression model will be used to analyse the probable determinants of leptospirosis. This model will evaluate the effect of same level and upper level variables on the outcome leptospirosis, using three blocks.

Discussion

The present national control programme of leptospirosis is hampered by lack of baseline data on leptospirosis disease transmission. The present study will be able to provide these essential information for formulation of better control strategies.

Epidemiology of human leptospirosis in Trinidad and Tobago, 1996-2007: a retrospective study

A retrospective study to describe the epidemiology of human leptospirosis in Trinidad and Tobago during 1996-2007 was conducted. All confirmed cases of leptospirosis was analyzed according to age, sex, seasonality and geographic distribution. A total of 278 cases were recorded, with an average annual incidence rate of 1.84 per 100,000 population. Seventy-five percent of the cases occurred during the wet season, with the highest number of cases recorded in November. A positive correlation was found between number of cases and rainfall. Males constituted 80% of all cases, and the overall male:female ratio was 4.6:1. The total case fatality rate was 5.8%, with deaths among males four times more common than in females. Clinical leptospirosis was greatest in the 10-19 age group and lowest in the 0-9 age group. The total prevalence was 22 per 100,000 population, with the highest prevalence 41 per 100,000 recorded in the regional corporation of Sangre Grande and the lowest (6 per 100,000) in the city of Port of Spain. The lack of important information and active surveillance showed that the level of awareness of the disease is low in the country. The disease is still under-reported, and is considered to be of significant public health importance.

Molecular detection of Leptospira interrogans in human tissues and environmental samples in a lethal case of leptospirosis

A forensic case of suspected Leptospirosis with fatal course was resolved by the molecular detection of Leptospira interrogans in postmortem human tissues and in environmental samples. Polymerase chain reaction analysis and DNA sequencing confirmed the clinical diagnosis of Weil syndrome, and the death was considered to be an occupational accident with all the legal implications.

Evaluation of a commercial latex agglutination assay for serological diagnosis of leptospirosis

Leptospirosis is a febrile zoonosis of worldwide distribution. A latex agglutination assay was evaluated in two studies, the first using a panel of well-characterized sera from patients with leptospirosis and from patients with other disease states and the second, a prospective hospital-based study, evaluating sera from 186 consecutive patients admitted to hospital with acute febrile illness. The confirmed leptospirosis serum panel included paired acute- and convalescent-phase specimens from 40 cases, of which 34 gave positive latex tests (case sensitivity, 85%; 95% confidence interval [95% CI], 70 to 94%). The other diseases represented in the panel of 112 specimens from nonleptospirosis patients included autoimmune diseases, brucellosis, dengue, melioidosis, malaria, syphilis, toxoplasmosis, viral hepatitis, and a number of other viral infections. The specificity of latex agglutination using this panel was 81% (95% CI, 73 to 87%). Among the patients with acute febrile illness, there were 25 cases of leptospirosis and 161 patients with other diagnoses. The sensitivity and specificity of latex agglutination in this group were 88% (95% CI, 72 to 97%) and 98% (95% CI, 95 to 100%), respectively. In this evaluation, the two distinct groups of specimens gave similar results for sensitivity, but specificity was different in each study. The sensitivity and specificity observed for the hospital study were similar to those obtained in evaluations of other rapid tests in the same population. The results of this study suggest that multiple evaluations of new diagnostic assays should be performed, because performance characteristics may vary in different populations.

Sero-epidemiology of canine leptospirosis in Trinidad: serovars, implications for vaccination and public health

A sero-epidemiological study on canine leptospirosis was conducted in house, stray, farm and hunting dogs, as well as in suspect cases of clinical canine leptospirosis. Serum samples were collected from apparently healthy (vaccinated and non-vaccinated), house dogs. A questionnaire was administered to the owners to elicit information on risk factors for leptospirosis. The microscopic agglutination test was used to screen for leptospirosis using 17 international serovars. Reciprocal titres of between 100 and <800 were considered as evidence of past exposure while reciprocal titres of 800 or greater were classified as suggestive of acute/current infection. Of a total of 419 serum samples tested, 61 (14.6%) were seropositive for Leptospira agglutinins, 23 (5.5%) had mixed infections and 16 (3.8%) had current infection. Amongst 50 suspected cases of clinical leptospirosis, 24 (48.0%) were seropositive and only 13 (26.0%) had current infection compared with 10 (6.3%) and three (1.9%) of 160 apparently healthy house dogs respectively. The difference was statistically significant (P < 0.05; chi2). Twelve (25.5%) of 47 hunting dogs, 10 (20.4%) of 49 farm dogs and five (4.4%) of 113 stray dogs were seropositive (P < 0.05; chi2). Overall, a total of nine serovars were detected with serovars mankarso, icterohaemorrhagiae RGA, autumnalis and copenhageni being involved in 29 (47.5%), 20 (32.8%), 25 (41.0%) and 10 (16.4%) respectively in 61 seropositive dogs (P < 0.05; chi2). Serovar mankarso was most predominant in seropositive apparently healthy dogs, 37.8% (14/37), suspected clinical cases of leptospirosis, 62.5% (15/24) compared with serovar icterohaemorrhagiae with a frequency of 21.6% (8/37) and 50.0% (12/24), the difference being statistically significant (P < 0.05; chi2). Although all vaccines used for prevention of canine leptospirosis in the country contain serovars canicola and icterohaemorrhagiae, serovar mankarso was mostly associated with infection and disease and may be a good candidate for inclusion in the vaccine used locally. The public health risk posed to owners of dogs infected with Leptospira cannot be over-emphasized considering the zoonotic nature of the disease.

Prevention and treatment of leptospirosis

Leptospirosis is a common zoonosis acquired by exposure to body fluids, to tissues of infected animals, or to contaminated soil or fresh water. Large outbreaks of leptospirosis have occurred following excess rainfall or in tourists following exposure to fresh water during adventure activities. Prevention may be achieved through the use of protective clothing or by changes in animal husbandry. Immunization is not widely used in human populations but has a role in agriculture. Oral administration of doxycycline (Periostat , CollaGenex) once-weekly can give short-term protection in high-risk environments. The disease in humans has a broad range of symptoms. Treatment may be symptomatic or may require administration of antibiotics, such as doxycycline or penicillin.

Expression of leptospiral immunoglobulin-like protein by Leptospira interrogans and evaluation of its diagnostic potential in a kinetic ELISA

The search for novel antigens suitable for improved vaccines and diagnostic reagents against leptospirosis led to the identification of LigA and LigB. LigA and LigB expression were not detectable at the translation level but were detectable at the transcription level in leptospires grown in vitro. Lig genes were present in pathogenic serovars of Leptospira, but not in non-pathogenic Leptospira biflexa. The conserved and variable regions of LigA and LigB (Con, VarA and VarB) were cloned, expressed and purified as GST-fusion proteins. Purified recombinant LigA and LigB were evaluated for their diagnostic potential in a kinetic ELISA (KELA) using sera from vaccinated and microscopic agglutination test (MAT)-positive dogs. Sera from vaccinated dogs showed reactivity to whole-cell antigens of leptospires but did not show reactivity in the KELA assay with recombinant antigens, suggesting a lack of antibodies to Lig proteins in the vaccinated animals. The diagnostic potential of recombinant Lig antigens in the KELA assay was evaluated by using 67 serum samples with MAT > or =1600, which showed reactivity of 76, 41 and 35% to rConA, rVarA and rVarB, respectively. These findings suggest that recombinant antigen to the conserved region of LigA and LigB can differentiate between vaccinated and naturally infected animals.

Evaluation of environmental risk factors for leptospirosis in dogs: 36 cases (1997–2002)

OBJECTIVE

To identify environmental risk factors for leptospirosis.

DESIGN

Retrospective study.

ANIMALS

36 dogs with leptospirosis and 138 dogs seronegative for leptospirosis as determined by microscopic agglutination test for antibodies against Leptospira spp.

PROCEDURES

Medical records of dogs evaluated for leptospirosis from 1997 though 2002 were identified. Owner address was used to geocode locations of dogs, and location-specific environmental risk factor data were obtained by use of a geographic information system. Risk of leptospirosis was estimated by odds ratios, controlling for potential confounding by dog age, sex, and breed.

RESULTS

Leptospirosis in 19 of the 30 dogs in which an infecting Leptospira serovar could be identified was associated with Leptospira kirschneri serovar grippotyphosa infection. Dogs in which a diagnosis of leptospirosis was made, and dogs with leptospirosis caused by L kirschneri serovar grippotyphosa, were more likely to have addresses located in areas classified as rural in 1990 but urban in 2000. By use of information on recent urbanization and a logistic regression model, the status of 81.6% and 89.8% of dogs with leptospirosis and leptospirosis caused by serovar grippotyphosa, respectively, were correctly classified. Other environmental variables (proximity to streams, recreational areas, farmland, wetlands, areas subject to flooding, and areas with poor drainage; annual rainfall; and county cattle or pig population) did not significantly improve accuracy of classification.

CONCLUSIONS AND CLINICAL RELEVANCE

Dogs in periurban areas are at greater risk of leptospirosis. Vaccination of dogs in these areas to protect against leptospirosis should be considered.

Direct detection of leptospiral material in human postmortem samples

Leptospiral culture, direct immunofluorescence, and the polymerase chain reaction (PCR) were used to detect leptospiral material in postmortem specimens collected from eight patients who died of leptospirosis. Diagnosis of leptospiral infection was based on clinical summary (premortem) and confirmed by serological analysis and/or culture of leptospires. Leptospiral culture was the least sensitive technique, yielding two isolates (3%) from 65 samples. Both isolates were from the aqueous humour and cerebrospinal fluid of the same patient. Direct immunofluorescence was of intermediate sensitivity for detection of leptospires, confirming the presence of leptospires in 11% (2 of 18) of tissue samples from three patients. PCR analysis was the most sensitive technique for detection of leptospiral material in tissue samples, being positive in 20% (11 of 56) of samples from eight patients. Both samples (cerebellum and liver) positive by immunofluorescence were also positive by PCR. The sensitivity of the PCR assay was 1-10 leptospires ml(-1) sample, and the assay was specific for Leptospira pathogenic species. Multi-system involvement was indicated based on successful amplification of leptospiral DNA from more than one tissue sample, which corroborated with the clinical and pathologic findings. The results suggest that in acute and/or fatal leptospirosis, the pathogenesis of the pathologic features are related to the presence of the organisms in the tissues. In conclusion, PCR combined with serology appears to be a useful tool for diagnosis of leptospirosis and may be invaluable in epidemiological studies.

A Serosurvey of Leptospirosis in Connecticut Peridomestic Wildlife

Recently, leptospirosis has gained attention as a re-emerging infection in domestic dogs in the northeastern United States. In order to gain insight into the epizootiology of leptospirosis in this region, 109 small wild mammals (31 raccoons (Procyon lotor), 30 skunks (Mephitis mephitis), 28 opossums (Didelphis virginiana), and 20 gray squirrels (Sciurus carolinensis)) collected between February 27 and September 17, 2001 were tested for serologic evidence of exposure to five common Leptospira serovars (serovars pomona, icterohemorrhagiae, canicola, hardjo, grippotyphosa). Evidence of exposure to leptospirosis was detected in 36% of raccoons tested; icterohemorrhagiae was the predominant reactive serovar in these animals. Sera from 13% of skunks showed evidence of exposure to serovar grippotyphosa. One squirrel exhibited high antibody titers to serovars grippotyphosa and canicola. All 28 opossums examined tested negative to the five Leptospira serovars. Results from this serosurvey suggest that common peridomestic wildlife species should be considered as potential sources of leptospirosis to dogs and humans in Connecticut. Additional investigation is warranted to clarify their role in the epidemiology of this zoonotic disease in the northeastern United States.

Seasonality of canine leptospirosis in the United States and Canada and its association with rainfall

A retrospective study was undertaken to describe seasonal patterns of leptospirosis diagnosed at veterinary teaching hospitals in the United States and Canada, and to determine if occurrence of cases (diagnoses) was associated with rainfall. The veterinary medicine database (VMDB) was searched for records of dogs in which a diagnosis of leptospirosis was made, and average monthly rainfall recorded at the city where each hospital is located was calculated from historical data. Time-series analysis was used to identify the variables that best described occurrence of cases of leptospirosis. Three-hundred and forty dogs were diagnosed with leptospirosis at 22 veterinary teaching hospitals between 1983 and 1998. Most cases (n = 184) were diagnosed between August and November during each year of the study. A significant correlation (r = 0.41) was detected between the number of cases of leptospirosis diagnosed and average rainfall recorded 3-months prior to diagnosis. The best-fitting (Akaike's corrected information criterion = 2.01) regression on the leptospirosis case series included cases diagnosed in the previous month and 12-months previously, and rainfall recorded 3 months previously. Leptospirosis has a seasonal distribution (late summer to fall), and rainfall can be used to predict the occurrence of leptospirosis. Leptospirosis can affect the health of dogs seriously and its prevalence is increasing, but the disease is preventable by vaccination.

Diagnosis of human leptospirosis by monoclonal antibody-based antigen detection in urine

Hybridomas secreting specific monoclonal antibodies (MAb) to all members of the genus Leptospira (clone LF9) and those that are specific only to the pathogenic species (clones LD5 and LE1) were produced. MAb LF9, which was immunoglobulin G1 (IgG1), reacted to a 38-kDa component of the sodium dodecyl sulfate-polyacrylamide gel electrophoresis-separated whole-cell lysates of all Leptospira spp., while MAb LD5 and MAb LE1, which were IgG1 and IgG2a, respectively, reacted to the 35- to 36-kDa components of all serogroups of the pathogenic species of LEPTOSPIRA: The MAb LD5 was used in a dot blot-enzyme-linked immunosorbent assay (dot-ELISA) for detecting Leptospira antigen in urine samples serially collected from two groups of patients diagnosed with leptospirosis, i.e., 36 clinically diagnosed patients and 25 Leptospira culture confirmed patients. Their serum samples were tested serologically by IgM Dipstick assay, indirect immunofluorescence assay (IFA), and/or microscopic agglutination test (MAT). Urine samples of 26 patients diagnosed with other illnesses and 120 healthy individuals served as controls. For the first group of patients, who had been ill for an average of 3.4 days before hospitalization, the IgM Dipstick test, IFA, and MAT were positive for 69.4, 70.0, and 85.7% of patients, while the Leptospira antigenuria tested by the MAb-based dot-ELISA was positive for 75.0, 88.9, 97.2, 97.2, and 100% of patients on days 1, 2, 3, 7, and 14 of hospitalization, respectively. All but 1 of 11 patients whose serum samples collected on the first day of hospitalization were IgM seronegative, were positive by urine antigen test on day 1. This is strong evidence that detection of antigen in urine can provide diagnostic information that could be useful in directing early therapeutic intervention. The MAT was positive in 10 of 12 patients (83.3%) of the 25 culture-positive Leptospira patients who had been ill for an average of 5.04 days before hospitalization, and the Leptospira antigen was found in 64.0, 84.0, 96.0, 100, 100, 100, and 100% of the patients' urine samples collected on days 1, 2, 3, 4, 5, 6, and 7 of hospitalization, respectively. Leptospira antigenuria was found in 3 of the 26 patients diagnosed with other illnesses and 1 of the 120 healthy controls. The reasons for this positivity are discussed. The detection of antigen in urine by the monoclonal antibody-based dot-ELISA has high potential for rapid, sensitive, and specific diagnosis of leptospirosis at a low cost.

Leptospirosis

Leptospirosis is a worldwide zoonotic infection with a much greater incidence in tropical regions and has now been identified as one of the emerging infectious diseases. The epidemiology of leptospirosis has been modified by changes in animal husbandry, climate, and human behavior. Resurgent interest in leptospirosis has resulted from large outbreaks that have received significant publicity. The development of simpler, rapid assays for diagnosis has been based largely on the recognition that early initiation of antibiotic therapy is important in acute disease but also on the need for assays which can be used more widely. In this review, the complex taxonomy of leptospires, previously based on serology and recently modified by a genotypic classification, is discussed, and the clinical and epidemiological value of molecular diagnosis and typing is also evaluated.

Two methods for rapid serological diagnosis of acute leptospirosis

Leptospirosis is a common and underdiagnosed zoonosis. Two rapid assays for serological diagnosis of acute leptospirosis in diagnostic laboratories, the immunoglobulin M (IgM)-dipstick assay and the indirect hemagglutination assay (IHA), were evaluated and compared with standard assays. Sera were examined from 104 patients admitted to a hospital for investigation in a leptospirosis diagnostic protocol. Specimens for serology were taken on days 1 and 4 of the patients' hospital stay. Antibodies were detected using an IgM-enzyme-linked immunosorbent assay (ELISA), microscopic agglutination test (MAT), an IgM-dipstick assay, and an IHA. Fifty-one patients were found to have leptospirosis. The sensitivity of the IgM-dipstick assay was 98%, its specificity was 90.6%, its positive predictive value was 90.9%, and its negative predictive value was 98%. The sensitivity of the IHA was 92.2%, its specificity was 94.4%, its positive predictive value was 95.9%, and its negative predictive value was 92.7%. The standard IgM-ELISA and MAT, were positive in the first samples tested from 67 and 55% of the cases, respectively, and the rapid IgM-dipstick assay and IHA were positive in 71 and 49%, respectively, in the first sample tested. Both rapid assays are highly sensitive and specific. Neither requires specialized equipment, and both are suitable for use in diagnostic laboratories.

Evaluation of the indirect hemagglutination assay for diagnosis of acute leptospirosis

Serology plays an important role in the diagnosis of leptospirosis. Few laboratories have the resources and expertise to perform the microscopic agglutination test. There is a need for rapid and simple serological tests which facilitate the early diagnosis of leptospirosis, while antibiotic therapy may be most effective. A commercially available indirect hemagglutination assay (IHA; MRL Diagnostics, Cypress, Calif.) was evaluated with multiple serum specimens from 107 patients being investigated for leptospirosis. By using a combination of enzyme-linked immunosorbent assay (ELISA) methods for immunoglobulin M (IgM) and IgG antibodies and the microscopic agglutination test, 54 patients were found to have leptospirosis and 53 were found not to have leptospirosis. The sensitivity of IHA for the detection of acute leptospirosis was 100%, the specificity was 94%, the positive predictive value was 95%, and the negative predictive value was 100%. IHA was negative when 13 antinuclear antibody-positive sera, 24 serum specimens from patients with syphilis, and 16 serum specimens false positive by the Venereal Disease Research Laboratory test were tested. IHA was shown to detect both IgM and IgG classes of antibodies in human sera. Serum specimens from 27 dogs investigated for leptospirosis were studied: 3 samples gave nonspecific hemagglutination, but for all remaining samples, the results of IHA and an IgM ELISA were concordant. Performance of IHA was simple, and IHA requires no specialized equipment. It represents a useful assay for laboratories which require a leptospiral diagnostic capability but lack the expertise to perform specialist investigations.

Seroepidemiology of canine leptospirosis on the island of Barbados

Previous surveillance in Barbados documented the absence of infection with Leptospira serogroup Canicola in dogs. The aim of this study was to survey the current state of canine leptospirosis in Barbados, 10 years after the last survey. Sera from 78 unwanted dogs scheduled for euthanasia and 61 dogs suspected of having acute leptospirosis were tested by microscopic agglutination (MAT) and by an ELISA method adapted for canine IgM and IgG antibodies. The seroprevalence in unwanted dogs was 62% (48/78), at an MAT titre of > or = 100. The majority of animals had low titres, suggestive of previous infection. Serogroup Autumnalis was the most common reactor (45%), followed by serogroups Icterohaemorrhagiae and Australis (each 16%) and Pomona (13%). Serogroup Ballum was uncommon in this group. The seroprevalence determined by MAT in acutely-ill dogs was 75% (46/61). The most common predominant serogroup was Icterohaemorrhagiae (36%) followed by serogroup Australis (13%), while serogroups Autumnalis and Ballum were also of little significance. Paired specimens were available from eight acutely-ill dogs. One animal was seronegative while five dogs showed evidence of seroconversion. An IgM-ELISA titre of > or = 320 was used to confirm current infection in eight of these nine animals. Previous studies in Barbados showed a higher prevalence of serogroup Icterohaemorrhagiae than of Autumnalis, but the relative frequency of these two serogroups may be changing. The high seroprevalence in dogs is of public health concern because the close contact between dogs and man may provide the link between a reservoir in the environment and susceptible humans.