A ten-year follow-up of human leptospirosis in Uruguay: an unresolved health problem

Leptospirosis seroprevalence and associated risk factors in dairy goats in the Brazilian semi-arid region

Leptospira spp. infection is a worldwide zoonosis that causes economic losses to goat rearing, mainly due to reproductive disorders. Hence, the objective of this research was to determine the seroprevalence and associated risk factors of leptospirosis in a goat milk-producing region in the states of Paraiba and Pernambuco, Northeast Brazil. The microscopic agglutination test was used as serological method and risk factor analysis was carried out using univariable and multivariable analyses. Out of the 937 animals sampled, 102 (10.9 %; 95 % CI = 8.9-12.9 %) were seropositive for Leptospira spp. and the most frequent serogroups were Ballum (41.2 %; 95 % CI = 31.6-50.7 %), Icterohaemorrhagiae (25.5 %, 95 % CI = 17-33.9 %) and Semaranga (23.5 %, 95 % CI = 15.3-31.8 %), with antibody titres ranging from 1:50 to 1:200. Thirty-four of 51 herds (66.7 %; 95 % CI = 53.7-79.6 %) had at least one seropositive animal. The risk factor identified in the multivariable two-level random effect binary logistic regression was the animal being an adult (odds ratio = 4.2; 95 % CI = 1.93-9.13; P < 0.001). Our results provide important information on the epidemiology and risk factors associated with goat leptospirosis seroprevalence in one of the main Brazilian goat milk-producing regions. Furthermore, the need for adopting sanitary control measures, especially those involving sanitary management practices, is highlighted.

Advancing serologic diagnosis: assessing the efficacy of rErpY-like protein in human leptospirosis detection

Leptospirosis is a globally distributed infectious disease caused by pathogenic spirochetes of the Leptospira genus, often overlooked. It is estimated that the disease affects approximately one million people annually, resulting in more than 58,900 deaths. The gold standard for serodiagnosis of leptospirosis is the Microscopic Agglutination Test (MAT). However, the limitations of this technique necessitate the exploration of alternative diagnostic methods. In this study, we evaluated the ErpY-like recombinant protein (rErpY-like) in the development of a serologic diagnostic assay for human leptospirosis. Eighty-six human sera samples, characterized by MAT, underwent evaluation through indirect IgM-ELISA and IgG-ELISA. The sensitivity and specificity values obtained from IgM-ELISA were 60% and 76%, respectively, while those from IgG-ELISA were 96.4% and 100%, respectively. The use of the rErpY-like protein in both IgM-ELISA and IgG-ELISA proves to be a sensitive and specific method for antibody detection. This could potentially serve as a valuable alternative tool in the diagnosis of human leptospirosis.

Seroprevalence of anti-Leptospira antibodies in equines and associated workers-Isolation of Leptospira interrogans serogroup Canicola from equine urine

To investigate seroprevalence of anti-Leptospira antibodies in equines and associated workers in Uruguay, 891 equine and 150 human sera were drawn; 212 equine urine samples were also taken for culture. Environmental conditions and equine raising or managing practices were recorded in all 72 visited establishments; epidemiological information was obtained from each worker. Microscopic agglutination technique (MAT) was performed with 10 Leptospira strains for equines and 18 for human sera, that were also studied with IgM indirect immunofluorescence (IgM-IIF). Equine titres ≥100 were considered positive, and human sera titres ≥200 suggested probable recent or past infection. Urines were cultured in Ellinghausen-McCullough-Johnson-Harris (EMJH) media; local identification of one obtained isolate with lipL32 PCR, Multiple Locus Variable number tandem repeat Analysis and partial rrs gene sequencing, were completed at Institut Pasteur, Paris. Estimated reactivity was 61.3% for equines, which was higher than the studied bovine national levels (21%) and mainly observed with Icterohaemorrhagiae serogroup (40.3%), Sejroe, Canicola, Pomona or Ballum. Aged animals from slaughterhouses and cattle farms were the most frequently positive. Multiple regression analysis confirmed a significant association between seropositivity and equine age. Only one positive culture could be fully studied, and confirmed to be Leptospira interrogans serogroup Canicola; it was added to the MAT antigen panel and revealed fairly frequent reaction with equine and human sera. Three workers (2%) showed titres = 200 with Icterohaemorrhagiae or Canicola serogroups, without recent clinical manifestations. Their attended equines reacted with the same serogroups, suggesting common source infections or infection transmitted by equines. Three other humans yielded titres = 100, and none of the 150 showed an IgM-IIF-positive result. Equines seem not to be an important origin of regional human leptospirosis, except perhaps during acute animal infection. More culture work is required to study intensity and lapses of leptospiruria, as well as to further identify circulating strains.

Seroprevalence of leptospirosis in human groups at risk due to environmental, labor or social conditions

Leptospirosis is important in Uruguay due to the economic loss caused by the diseases of production animals, mainly bovines, and also due to frequent human infection. We decided to study anti-Leptospira antibodies in the sera of dairy workers, rice laborers, veterinarians, suburban slum dwellers and garbage recyclers. Our aims were to estimate the seroprevalence of infection by Leptospira spp. in these people at risk, the relative importance of the known risk factors associated with infection, and the impact of human infections in each setting. Groups at risk were identified and 35 visits to their locations were made, conducting field surveys and exchange talks for information and education. Simple epidemiological questionnaires were administered and sera samples were taken from 308 persons. The microagglutination Technique (MAT) and the IgM Indirect Immunofluorescence (IIF) assay were employed to detect antibodies. Environmental water samples, canine and equine sera were also examined. More than 45% of human sera were reactive and the studied groups were confirmed to be widely exposed to infection. Female sera were frequently reactive, though most illnesses occur in men, and the most severe cases in elderly males; the emergence and evolution of the disease may strongly depend on the host condition and functions. Animal contact and unsafe water usage were the main identified risk factors to be considered in prevention. Fifty per cent of the studied horses showed a positive MAT reaction. The underdiagnosis of the illness and its long-term symptoms require further study, as well as greater health and social attention efforts.

Isolation of pathogenic Leptospira strains from naturally infected cattle in Uruguay reveals high serovar diversity, and uncovers a relevant risk for human leptospirosis

Leptospirosis is a neglected zoonosis with worldwide distribution. The causative agents are spirochete bacteria of the Leptospira genus, displaying huge diversity of serovars, the identity of which is critical for effective diagnosis and vaccination purposes. Among many other mammalian species, Leptospira infects cattle, eliciting acute signs in calves, and chronic disease in adult animals often leading to abortions. In South America, and including in Uruguay, beef and dairy export are leading sources of national income. Despite the importance of bovine health, food safety, and bovine-related dissemination of leptospirosis to humans, extremely limited information is available as to the identity of Leptospira species and serovars infecting cattle in Uruguay and the South American subcontinent. Here we report a multicentric 3-year study resulting in the isolation and detailed characterization of 40 strains of Leptospira spp. obtained from infected cattle. Combined serologic and molecular typing identified these isolates as L. interrogans serogroup Pomona serovar Kennewicki (20 strains), L. interrogans serogroup Canicola serovar Canicola (1 strain), L. borgpetersenii serogroup Sejroe serovar Hardjo (10 strains) and L. noguchii (9 strains). The latter showed remarkable phenotypic and genetic variability, belonging to 6 distinct serogroups, including 3 that did not react with a large panel of reference serogrouping antisera. Approximately 20% of cattle sampled in the field were found to be shedding pathogenic Leptospira in their urine, uncovering a threat for public health that is being largely neglected. The two L. interrogans serovars that we isolated from cattle displayed identical genetic signatures to those of human isolates that had previously been obtained from leptospirosis patients. This report of local Leptospira strains shall improve diagnostic tools and the understanding of leptospirosis epidemiology in South America. These strains could also be used as new components within bacterin vaccines to protect against the pathogenic Leptospira strains that are actually circulating, a direct measure to reduce the risk of human leptospirosis.

Several species of the genus Leptospira cause leptospirosis, a disease that is transmitted from animals to humans (zoonosis). Leptospirosis is the most extended zoonosis worldwide, with over a million human cases each year. Leptospira spp. infect a broad range of wildlife and domestic animals, including cattle. In several South American countries beef and dairy exports rank among the most important national income sources, explaining why in Uruguay cattle outnumber human population by a factor of 4. Yet, we did not know which Leptospira species and serovariants (serovars) circulate among Uruguayan cattle. Current serologic diagnostic methods and whole killed-cell vaccination approaches, critically depend on using the proper serovars, which are hugely variable in Leptospira spp. from different regions of the world. Through a multidisciplinary consortium effort, we now report the isolation and typing of 40 strains of pathogenic Leptospira spp. An unexpectedly large variation in terms of species and serovars was found. These data are extremely important: 1- to improve diagnostics by updating the available reference antigen panels; 2- to evaluate the efficacy of novel vaccines; and, 3- to implement efficacious bovine vaccination as a means of reducing the incidence of bovine and human leptospirosis.

Detección molecular de leptospiras patógenas en roedores sinantrópicos y silvestres capturados en Yucatán, México

Introducción. La leptospirosis es una enfermedad zoonótica endémica en México, ocasionada por la bacteria del género Leptospira, la cual constituye un problema de salud pública y veterinaria. Los roedores son los reservorios más relevantes de Leptospira spp., debido a que la bacteria se establece y se reproduce en su tejido renal y es excretada por la orina.Objetivo. Identificar la presencia de Leptospira spp. en tejido renal de roedores capturados en Yucatán, México.Materiales y métodos. Se capturaron roedores sinantrópicos y silvestres en el municipio rural de Cenotillo, Yucatán, México. Se tomó un riñón de cada roedor y se extrajo el ADN total. La identificación de Leptospira spp. se hizo mediante la detección de dos fragmentos del gen 16S rRNA con una reacción en cadena de la polimerasa (PCR) de punto final. Los productos positivos se secuenciaron y se analizaron con herramientas de alineamiento.Resultados. Se capturaron 92 roedores pertenecientes a siete especies distintas. La PCR arrojó 5,4 % (5/92) de positividad global. El análisis del alineamiento de los aislamientos de los roedores infectados demostró 100 % de cobertura e identidad con la especie Leptospira interrogans. Esta es la primera evidencia molecular de la circulación de Leptospira spp. en Heteromys gaumeri capturados en Yucatán, México.Conclusión. Se evidenció que los roedores de Yucatán, México, son reservorios de Leptospira spp. y participan en el ciclo de infección de la leptospirosis en la región.

Analysis of the spatial distribution of scientific publications regarding vector-borne diseases related to climate variability in South America

Most vector-borne diseases exhibit a distinct seasonal pattern, which clearly suggests that they are weather sensitive. Rainfall, temperature, and other climate variables affect in many ways both the vectors and the pathogens they transmit. Likewise, climate can be determinant in outbreaks incidence. A growing number of studies have provided evidence indicating the effects of climate variability on vector-borne diseases. However, oftentimes, the different diseases and regions are not uniformly represented, scarcity or lack of publications in some countries is common. The objectives of this work were to analyze the distribution and abundance of publications on vector-borne diseases associated with climate variability in South America, identify those works that conducted a geographic analysis and detect the countries where outbreaks occurred and the climate variables with which they were associated. A systematic review of the literature published on vector-borne diseases linked to climate variability in South America was conducted, identifying, evaluating and summarizing scientific papers. The distribution of the study areas and disease type in the publications were represented on maps. Dengue and leishmaniasis were the most studied and widely represented diseases in South America. The country with the largest number of published papers and presence of all disease types was Brazil. Outbreaks of disease were related to different climate variables. Most diseases from the publications under study occurred in equatorial and tropical climates. The disease represented by the largest number of different types of climates was dengue. The technique used in this work allowed us to determine the status of knowledge of the main diseases associated with climate variability in South America. This methodology could be improved in the future by incorporating other bibliographic sources as well as other diseases related to climate variability.

Characterization of Leptospira isolates from humans and the environment in Uruguay

Laboratory diagnosis of human leptospirosis usually relies on indirect methods exploring specific immune response. Isolation and identification of the involved strains are cumbersome, but can provide biological resources for pathogenic studies and relevant information for guiding prevention and control measures. The aim of the research we are hereby reporting was the characterization of Leptospira isolates obtained from humans and the environment in Uruguay. Blood cultures were performed from early samples of 302 Uruguayan patients, mainly rural workers, and from 36 water samples taken from their living or working environments. Eight human isolates and seven environmental isolates were obtained and analyzed by end point Polymerase Chain Reaction (PCR), Multilocus Variable Number of Tandem Repeat Analysis (MLVA) and other molecular methods. Human isolates corresponded to several serogroups and serovars of Leptospira interrogans and Leptospira kirschneri species, probably reflecting the infection with similar involved Leptospira species and serovars of an extended animal reservoir in rural settings of the country, mostly dedicated to meat and dairy production. Culture-positive patients were older than usually affected workers, and presented signs and symptoms of severe illness. A high organic and circulating bacterial burden may explain an easier positive result from these workers’ samples. Environmental isolates were mainly identified as Leptospira biflexa strains, with a single L. meyeri isolate of uncertain significance.

Assessment of anticoagulant rodenticide exposure in six raptor species from the Canary Islands (Spain)

Anticoagulant rodenticides are highly toxic compounds that are widely used for pest control of rodents, but that also may threaten the wildlife's health. This work aimed to assess the exposure to first- and second-generation anticoagulant rodenticides (ARs) in six birds of prey species from the Canary Islands (Spain). The concentrations of seven widely used ARs were determined by LC-MS/MS in 104 liver samples of six species of birds of prey (Buteo buteo, Accipiter nisus, Falco pelegrinoides, Falco tinnunculus, Asio otus, and Tyto alba). We determined that 61% of the livers had detectable residues of at least one AR. The most frequently detected AR was bromadiolone, which was detected in 60.3% of the positive cases. The detection frequencies of these compounds varied widely, depending on the species. More than 75% of the A. nisus, T. alba, and A. otus individuals had detectable rodenticide residues in the liver. However, F. tinnunculus exhibited the highest concentrations of AR, with median values above 100 ng/g w.w. We did not detect first-generation ARs in any of the samples. When grouped, nocturnal species exhibited higher AR concentrations than diurnal species (P<0.001). The residue levels were higher among small mammal-eaters than bird-eaters (P<0.01). While most animals exhibited no macroscopic signs of coagulation disorders, approximately 35% exceeded the threshold levels of toxicity, which suggests that these compounds could weaken these animals in their natural environment. In conclusion, the control of rodent populations by ARs suggests that these compounds will enter the food chain and thus threaten the vulnerable populations of raptors on the Canary Islands. Our findings require authorities to ban or strictly control the use of these rodenticides in the natural environment for the conservation of raptors and other predatory species.

Leptospirosis: current situation and trends of specific laboratory tests

Leptospirosis is re-emerging as a worldwide zoonosis and is caused by bacteria of the genus Leptospira. Human leptospirosis is associated with high temperature and humidity. Laboratory tests are indispensible for the early diagnosis and proper disease management. The demand for suitable leptospirosis point-of-care diagnostic tests grows with the awareness and number of incidences. Confirmation is achieved by the microscopic agglutination test, bacterial cultivation, PCR or histopathologic methods. However, high costs, poor standardization and/or elaborate sample preparation prevent routine use at the point of care. Cost-efficient, but insensitive serological methods dominate the diagnostic landscape and, likewise, urgently need improvement toward greater compliance with some of the point-of-care criteria. Combined application of antigen and antibody detection methods increases accuracy, but also new development or transfer of diagnostic technologies should be considered useful. Nano- and microparticle technology may play a key role in improving future antigen detection methods.