Prevalence Of Leptospiral Infection Research Articles

Epidemiology and enzyme-linked immunosorbent assay of Leptospira spp. in humans in the Republic of Guinea

Introduction: Leptospirosis is a zooanthroponosis caused by spirochete bacteria called leptospire of the genus Leptospira. Objective: To contribute to the knowledge and circulation of the Leptospira germ in humans in the Republic of Guinea. Methods: This prospective and descriptive cross-sectional study lasted 18 months, from June 2019 to December 2020. Results: Of 2346 human blood samples analysed in the laboratory using the enzyme-linked immunosorbent assay (ELISA) for IgG antibodies against leptospirosis, the largest number of samples was taken in Lower Guinea (31.58%), followed by Forest Guinea (27.66%), Middle Guinea (20.97%) and Upper Guinea (19.77%). More samples were taken from females (50.89%) than males (49.10%), for a sex ratio of 1.03 in favour of females. In terms of natural regions, Basse Guinée recorded the highest number of female samples (36.85%). On the other hand, the highest number of male samples was observed in Guinée Forestière with 28.55%. The results of anti-leptospira class G immunoglobulin tests identified the germ in 93 patients, representing a prevalence of 4%. The average age of the patients was 45, with extremes ranging from 10 to 90 years. Of the 93 positive cases, the prevalence of Leptospira infection was highest in subjects aged 31 to 40 (46.23%), followed by individuals in the 41 to 50 age group (18.27%). Prevalence was lower in the 11-20 age group (9.67%), the 51-60 age group (7.52%) and the 61-70 age group (3.22%). No cases of Leptospire infection were recorded in the 0-10, 71-80 and 81-90 age groups. Males accounted for 53.76% of Leptospire infections, compared with 46.23% for females, with a 95% confidence interval (CI) ranging from [13.08-20.82]. Lower Guinea recorded 25.80%, followed by Middle Guinea with 32.25%, Upper Guinea with 20.43% and Forest Guinea with a prevalence of 21.51%. The prevalence of Leptospira infection is higher among women in Middle Guinea (21.50%) than in the other natural regions. We also note that Lower Guinea recorded the highest rate of positivity among males at 18.28% compared with the other regions of Guinea. Farmers are the most affected by infections with 46.23%, followed by veterinarians with 25.80%, health workers with 18.28%, retired people with 4.30% and commercial workers with 3.22% (3/93). Students and workers were the least represented in this study, with 1 case each, representing a prevalence of 1.07%. Conclusion: The results obtained prove that the leptospirosis pathogen does exist in the Republic of Guinea in the entire human population.

Epidemiology of Leptospira spp. infection in a beef cattle area of Argentina.

Leptospirosis is an infectious disease caused by pathogenic Leptospira that affect humans and animals. This disease is complex and non-eradicable in nature. Therefore, the understanding of it is epidemiology in different environments is crucial to implement prevention and control measures. The prevalence of Leptospira infection in beef cattle farms is affected by multiple environmental, management and individual factors. In this study, a cross-sectional serological survey was carried on to estimate the prevalence of Leptospira antibodies in beef cattle in Tandil and Ayacucho Departments (Buenos Aires Province) and to identify risk factors and spatial clusters associated with seropositivity. Using a probabilistic two-stage sampling, 25 farms and 15 animals per farm were selected. The Microagglutination Test was used to analize all serum samples. Bivariate and multivariate analyses were performed. Seventy-three out of 375 cows were seropositive, representing a positivity rate of 19.47% (95% CI: 10.51-28.42), with Sejroe and Pomona being the most reactive serogroups: 9.33% (95% CI: 6.26-12.41) and 8.27% (95% CI: 5.35-11.19), respectively. The prevalence in Ayacucho was 23.11% (95% CI: 10.05-36.17), and in Tandil, 14% (95% CI: 3.25-24.75). The animals from Ayacucho presented 2.01 (1.16-3.49) more chances of being positive compared with those from Tandil (p < 0.01). After the Generalized Linear Mixed Model (GLMM) with random effect of farm-level risk, the presence of lagoons (OR: 7.32, 95% CI: 1.68-31.8, p < 0.05) and undulating terrain (OR: 0.24, 95% CI: 0.07-0.74, p < 0.05) were associated with bovine leptospirosis. Four spatial clusters with higher rates of seropositivity were detected. A new GLMM was performed with the significant variables detected in the first GLMM and a new variable, "being inside the spatial cluster," being the only one that remained significant (OR: 9.58, 95% CI: 3.39-27.08, p < 0.0001). The animals inside the clusters belonged to farms with a greater presence of creeks (OR: 9.03, 95% CI: 3.37-24.18, p < 0.0001), higher accumulated rainfall (OR: 1.01, 95% CI: 1-1.01, p < 0.0001) and less undulating terrain (OR: 0.18, 95% CI: 0.10-0.35, p < 0.0001). We conclude that Leptospira is seroprevalent in beef cattle in Tandil and Ayacucho Departments, especially in the latter, where the largest cattle farms are located. Prevalence of seropositivity animals was associated with selected environmental risk factors.

Serological and molecular detection of pathogenic Leptospira in domestic and stray cats on Reunion Island, French Indies.

Indian Ocean islands are endemic areas for human and animal leptospirosis. Maintenance host species for Leptospira spp. have still not been completely elucidated, and recently the role of cats (Felis catus) has been questioned. This cross-sectional study aims to determine whether cats are part of the maintenance community of different strains of Leptospira spp. in Reunion Island. The prevalence of Leptospira infection in an opportunistic sample of stray and domestic cats (n = 92) from Reunion Island has been studied using serological (microagglutination test) and molecular detection (polymerase chain reaction (PCR)). The results revealed a seroprevalence of 37.0% (34/92) (cut-off 1:40) without a significant difference in the living conditions of animals. The predominant serogroup was Icterohaemorrhagiae, but Ballum, Cynopteri and Australis were also detected. Using PCR, 28.6% (12/42) of stray cats were tested positive. Leptospiral DNA was detected in renal tissue, urine and blood of respectively 14.3% (6/42), 10.3% (4/39) and 11.9% (5/42) of stray cats, but 0% (0/3), 0% (0/50) and 0% (0/36) of domestic cats (P = non-applicable, P = 0,038, P = 0,058 respectively). Partial rrs gene (16S rRNA) sequencing identified Leptospira interrogans in all PCR-positive samples. Our study confirms that renal carriage and urinary shedding are possible, positioning cats, and especially stray cats as potential actors within the maintenance community of L. interrogans in Reunion Island.

Prevalence of Leptospira Infection in Rodents from Bangladesh.

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

Passive surveillance of Leptospira infection in swine in Germany

BackgroundAs no current data are available on the prevalence of leptospiral infection in swine in Germany, we analysed laboratory data from diagnostic examinations carried out on samples from swine all over Germany from January 2011 to September 2016. A total of 29,829 swine sera were tested by microscopic agglutination test (MAT) for antibodies against strains of eleven Leptospira serovars.ResultsOverall, 20.2% (6025) of the total sample collection tested positive for leptospiral infection. Seropositivity ranged between 16.3% (964) in 2011 and 30.9% (941) in 2016 (January to September only). Of all samples, 11.6% (57.3% of the positives) reacted with only one Leptospira serovar, and only 8.6% (42.7% of the positives) reacted simultaneously with two or more serovars. The most frequently detected serovar was Bratislava, which was found in 11.6% (3448) of all samples, followed by the serovars Australis in 7.3% (2185), Icterohaemorrhagiae in 4.0% (1191), Copenhageni in 4.0% (1182), Autumnalis in 3.7% (1054), Canicola in 2.0% (585), and Pomona in 1.2% (368). Modelling shows that both the year and the reason for testing at the laboratory had statistically strong effects on the test results; however, no interactions were determined between those factors. The results support the suggestion that the seropositivities found may be considered to indicate the state of leptospiral infections in the German swine population.ConclusionAlthough data from passive surveillance are prone to selection bias, stratified analysis by initial reason for examination and analyses by model approaches may correct for biases. A prevalence of about 20% for a leptospiral infection is most probable for sows with reproductive problems in Germany, with an increasing trend. Swine in Germany are probably a reservoir host for serovar Bratislava, but in contrast to other studies not for Pomona and Tarassovi.

Meta-analysis to estimate the load of Leptospira excreted in urine: beyond rats as important sources of transmission in low-income rural communities

BackgroundLeptospirosis is a major zoonotic disease with widespread distribution and a large impact on human health. Carrier animals excrete pathogenic Leptospira primarily in their urine. Infection occurs when the pathogen enters a host through mucosa or small skin abrasions. Humans and other animals are exposed to the pathogen by direct contact with urine, contaminated soil or water. While many factors influence environmental cycling and the transmission of Leptospira to humans, the load of pathogenic Leptospira in the environment is likely to play a major role. Peridomestic rats are often implicated as a potential source of human disease; however exposure to other animals is a risk factor as well. The aim of this report is to highlight the importance of various carrier animals in terms of the quantity of Leptospira shed into the environment. For this, we performed a systematic literature review and a meta-analysis of the amount of pathogen that various animal species shed in their urine.ResultsThe quantity of pathogen has been reported for cows, deer, dogs, humans, mice, and rats, in a total of 14 research articles. We estimated the average Leptospira per unit volume shed by each animal species, and the daily environmental contribution by considering the total volume of urine excreted by each carrier animal. Rats excrete the highest quantity of Leptospira per millilitre of urine (median = 5.7 × 106 cells), but large mammals excrete much more urine and thus shed significantly more Leptospira per day (5.1 × 108 to 1.3 × 109 cells).ConclusionsHere we illustrate how, in a low-income rural Ecuadorian community, host population demographics, and prevalence of Leptospira infection can be integrated with estimates of shed Leptospira to suggest that peridomestic cattle may be more important than rats in environmental cycling and ultimately, transmission to humans.

First report of Leptospira infections in red deer, roe deer, and fallow deer in Poland

Abstract Introduction: Recently in Europe an increase in the population of red deer (Cervus elaphus), roe deer (Capreolus capreolus), and fallow deer (Dama dama) has been observed. Research on the prevalence of Leptospira infections in Polish cervids has been performed for the first time. Material and Methods: During 2014/2015 hunting season, 147 blood samples from red deer, roe deer, and fallow deer were collected. The animals originated from different geographical regions across Poland. Serum samples were tested by microscopic agglutination test (MAT) for the presence of specific antibodies to the following Leptospira serovars: Icterohaemorrhagiae, Grippotyphosa, Sejroe, Tarassovi, Pomona, Canicola, Bratislava, Hardjo, Ballum, Zanoni, Hebdomadis, and Poi. Results: Serum antibody titres specific to Grippotyphosa, Pomona, and Zanoni serovars were found; none of the sera were positive for any of the other serovars. Out of 147 serum samples only 7 were positive, which gave an overall prevalence of 4.8% in the tested animal population. Conclusion: The low Leptospira antibody titres along with the low number of positive serum samples in deer indicate that these animals may not act as significant reservoirs of Leptospira for either humans or animals in Poland.

Comparison of Leptospira interrogans infection in the goats and sheep

Background: Most leptospiral infections in sheep and goat are asymptomatic but may result in high fever, abortion, stillbirth, agalactiae. There is a different foraging behavior between sheep and goat that may cause the different prevalence of Leptospira interrogans infection in sheep and goats. OBJECTIVES: The purpose of the present study was to compare the prevalence of L. interrogans antibodies in sheep and goats. METHODS: Blood samples were taken from 246 sheep and 210 goats in 12 herds from 8 areas of Ahvaz where the animals were kept together. Sera were initially screened at dilution of 1:100 against 8 live serovars of L. intrrogans: pomana, canicola, hardjo, ballom, ictrohaemorrhagiae, grippotyphosa, tarasovi and australis using the microscopic agglutination test (MAT). RESULTS: The prevalence of leptospiral infection was 8.53% in sheep and 10.95% in goats. The highest reacting leptospira in both species was L.i. Pomona with a reactor rate of 68.18% in sheep and 56% in goats, followed in descending order by ictrohaemorrhagiae (18.8%), canicula, hardjo and grippotyphosa (each of them 4.54%), in sheep and ictrohaemorrhagiae (28%), canicula (16%) in goats. Statistical analysis showed that were no significant differences between sheep and goat (P=0.428). There were no significant differences among age groups in sheep (p=0.301) and goats (p= 0.363), but there was a tendency in adults sheep and goats (≥3years) to be more seropositive than young sheep and goats. Seroprevalence of leptospiral infection among various areas in sheep (p= 0.464) and goats (p= 0.710) was also not significantly different. CONCLUSIONS: It is concluded that there is no difference between sheep and goats in terms of leptospiral infection when they are kept together in the same herd and husbandry condition.

Epidemiology of leptospira transmitted by rodents in southeast Asia.

BackgroundLeptospirosis is the most common bacterial zoonoses and has been identified as an important emerging global public health problem in Southeast Asia. Rodents are important reservoirs for human leptospirosis, but epidemiological data is lacking.Methodology/Principal FindingsWe sampled rodents living in different habitats from seven localities distributed across Southeast Asia (Thailand, Lao PDR and Cambodia), between 2009 to 2010. Human isolates were also obtained from localities close to where rodents were sampled. The prevalence of Leptospira infection was assessed by real-time PCR using DNA extracted from rodent kidneys, targeting the lipL32 gene. Sequencing rrs and secY genes, and Multi Locus Variable-number Tandem Repeat (VNTR) analyses were performed on DNA extracted from rat kidneys for Leptospira isolates molecular typing. Four species were detected in rodents, L. borgpetersenii (56% of positive samples), L. interrogans (36%), L. kirschneri (3%) and L. weilli (2%), which were identical to human isolates. Mean prevalence in rodents was approximately 7%, and largely varied across localities and habitats, but not between rodent species. The two most abundant Leptospira species displayed different habitat requirements: L. interrogans was linked to humid habitats (rice fields and forests) while L. borgpetersenii was abundant in both humid and dry habitats (non-floodable lands).Conclusion/Significance L. interrogans and L. borgpetersenii species are widely distributed amongst rodent populations, and strain typing confirmed rodents as reservoirs for human leptospirosis. Differences in habitat requirements for L. interrogans and L. borgpetersenii supported differential transmission modes. In Southeast Asia, human infection risk is not only restricted to activities taking place in wetlands and rice fields as is commonly accepted, but should also include tasks such as forestry work, as well as the hunting and preparation of rodents for consumption, which deserve more attention in future epidemiological studies.

A Serological Survey on Leptospiral Infection Among Wild Rats (Rattus rattus) of Ahvaz District, Southwest of Iran: A Preliminary Study

Background: Leptospirosis is an important zoonotic disease caused by pathogenic Leptospira which can infect both humans and animals. This disease is caused by various serovars of Leptospira interroganssensu lato infection. Rats are known to be one of the most important reservoirs and transmission sources of leptospirosis. However, the status of leptospirosis in wild rats has been unknown in many areas of Iran. Objectives: This study was conducted to evaluate the seroprevalence of leptospiral infection in wild rats (Rattus rattus) in Ahvaz district (southwest of Iran) from October 2009 to November 2011. Materials and Methods: Rats were trapped alive, anaesthetized, and blood-extracted by cardiac puncture. Serum samples were collected from 120 wild rats and screened for different leptospiral serovars using the microscopic agglutination test (MAT). The rats were classified according to sex, season and region of capture. The results were analyzed by Chi-square analysis and Fisher’s exact test. Results: From a total of 120 rats, 4 (3.33%) were serologically positive for the L. gryppotyphosa serovar. All positive titers were detected at 1:100 dilutions. Antibodies against more than one serovar were not detected in any sample. The prevalence of leptospiral infection was 2.5% and 0.83% in male and female rats, respectively. There was no significant difference in positive titer prevalence between different sexes, seasons and areas (P > 0.05). Conclusions: This survey indicated that serovars of L. gripotyphosa are prevalent in the rats population of this area and can be a source of infection for humans. The results of the present study provide useful information on the epidemiology of leptospirosis in this species, which was not well studied before.

Seroprevalence of leptospiral infection in horses, donkeys and mules in East Azerbaijan province

This study was conducted on 490 animals (390 horses, 80 donkeys and 20 mules) in East Azarbaijan province in Iran in order to verify seroprevalence of leptospiral infection in 2011. Sera were initially screened at dilution of 1:100 against 6 live serovars of Leptospira interrogans: Pomona, Canicola, Hardjo, Ballum, Icterohaemorrhagiae and Grippotyphosa using the microscopic agglutination test. The prevalence of leptospiral infection was 39.18% in animals. 153 horses (39.23%), 33 donkeys (41.25%) and 6 mules (39.18%) were positive and the difference between them was significant (P < 0.05); furthermore, 176 males (42.93%) and 25 (31.25%) females were positive. There was significant difference between males and females (P < 0.05). There was no significant relationship between aging and the incidence of leptospiral infection. The highest number of reactors in samples (38.96%) was due to serovar Pomona, followed by Grippothyphosa (32.73%), Icterohaemorrhagiae (15.15%), Canicola (10.39%), Hardjo (1.73%) and Ballum (1.04%). Most titre levels were between 100 and 200 for all the serovars. These results confirm that the majority of leptospiral infections are asignologic and the presence of antibodies in apparently healthy animals indicates exposure to leptospires. Key words: Equines, cross sectional study, seroprevalence, Leptospira, Iran.

A serological survey of Leptospiral infection of cats in Ahvaz, south-western of Iran

Leptospirosis is a zoonosis with numerous reservoir hosts. The disease is caused by infection with various serovars of Leptospira interrogans sensu lato. This study was conducted to evaluate the seroprevalence of leptospiral infection in stray cats in Ahvaz (south-western Iran) from April 2007 to June 2008. Blood samples were collected from 102 stray cats and screened for leptospiral infection using the microscopic agglutination test (MAT). Five of the 102 cats (4.9%) were serologically positive for at least one serovar of L. interrogans. The greatest number of reactors was for L. interrogans serovar balum (five serum samples). Antibodies against more than one serovar (namely, serovars balum and australis) were detected in one sample. All positive titers were detected at 1:100 dilution. The prevalence of leptospiral infection was 5.3% and 4.4% in male and female cats, respectively. There was no significant difference in positive titer prevalence between different sexes but prevalence was significantly different between age groups (P = 0.021), as all cats with positive titers were three years of age or more. This is also the first report of infection with L. interrogans serovars balum and australis from cats in Iran.

Seroprevalence of Leptospirosis and Risk Factor Analysis in Flood-prone Rural Areas in Lao PDR

A cross-sectional seroprevalence study on leptospirosis, using microscopic agglutination test (MAT), was conducted in rural villages in Khammouane Province, Lao People's Democratic Republic, in December 2006. The overall prevalence of leptospiral infection among 406 subjects was 23.9% (95% confidence interval [CI] 19.7-28.0%). Independent risk factors for the infection, identified by multivariate logistic regression, were male sex (odds ratio [OR], 1.92; 95% CI: 1.24-2.98), recent flooding on one's own property (OR, 2.12; 95% CI: 1.25-3.58), and collecting wood in the forest (OR, 1.90; 95% CI: 1.17-3.09). Age, occupation, and animal ownership were not associated with seropositivity. Flooding was associated with the risk of infection particularly for women, whose behaviors or activities involving contact with floodwater were presumed to play an important role. This study showed that leptospirosis is endemic in Khammouane Province and that local flooding plays an important role in the transmission of the disease.

Serological survey for evidence of Leptospira interrogans in free‐living platypuses (Ornithorhynchus anatinus)

To survey free-living platypuses for evidence of Leptospira interrogans. A serological study of Leptospira antibodies was carried out on 21 platypuses captured between May and October 2001 in the Wollondilly River 200 km south of Sydney, New South Wales. Positive reactions, all to the L Hardjo serovar, were seen in 14 (66%) of the captured animals, with adult males showing a higher prevalence of antibodies than adult females. Several individual platypuses showed a high titre of L Hardjo antibodies, and some animals demonstrated cross-reactions to the serovars L Medanensis and L Kremastos. The serological findings demonstrate that these animals are constantly exposed to infection with Leptospira in their environment, but it is not known if platypuses suffer from clinical leptospirosis or if they mount an immune response, but are unaffected by the bacteria. The prevalence of Leptospira infection among the platypus population could not be precisely estimated because of the unknown number of individuals inhabiting the Wollondilly River inside the survey property. Domestic livestock, mostly cattle, may be the major source of Leptospira infection. The effects of this disease on population dynamics and on reproduction in wild platypuses are not well understood. The role of other wildlife in the transmission and maintenance of Leptospira in the environment is unknown.

Prevalence of Leptospira spp. in wild brown rats (Rattus norvegicus) on UK farms.

Wild brown rats (Rattus norvegicus) are frequently implicated in the carriage and spread of Leptospira spp. Wild brown rats (n = 259) were trapped from 11 UK farms and tested for Leptospira spp. using a number of diagnostic tests. The prevalence of leptospiral infection was low, but there was variation in the results obtained with the different diagnostic tests. Estimates of prevalence ranged between 0% by silver-staining of tissues, 1% by the microscopic agglutination test, 4% by the enzyme-linked immunosorbent assay, 4% by culture, and 8% by fluorescent antibody technique. In total, 37 (14%) rats were positive by at least one of the tests, which contrasts with the frequently reported prevalences of 50-70% for wild rats in the UK. Serovar bratislava was a prevalent as icterohaemorrhagiae, although it was present only on farms with larger rat populations.

Survey on the prevalence of leptospira infections in the Italian population.

This investigation is the first nationwide survey on the circulation of leptospira infections in human beings in Italy. In nine out of twenty Italian regions, representative samples of the population were investigated for the presence of leptospira infections. Unexpectedly, leptospira infections were found to be widespread, the number of cases being much higher than the diagnosed clinical cases. There were found to be high, medium, and low risk areas. On the whole, the risk for the rural population was no higher than the risk for urban dwellers; leisure activities, contact with animals and residence on the plain versus residence in the hills were important risk factors. There was an unidentified risk factor in urbanites which was absent in the rural population. A changing pattern in infecting serovars was observed, with infections from serogroups Sejroe, Javanica and Australis prevailing over infections from the Icterohaemorrhagiae and Bataviae serogroups, which were the main agents of human leptospirosis during the 1950s. The mechanisms of these changes, the need for epidemiological surveys and improved diagnostic methods of screening are discussed.

Diagnosis and Prevalence of Leptospira Infection in Aborted and Stillborn Horses

A study was conducted to evaluate a recently available fluorescent antibody test (FAT) conjugate for the detection of leptospires in tissues of aborted and stillborn horses, to determine the leptospira antibody titers and compare serologic test results with FAT results, and to determine the prevalence of leptospira-induced abortions and stillbirths in the equine population of central Kentucky. From July 1, 1988 through June 30, 1989, 15 (2.5%) of 594 submissions (fetuses, stillborn foals, and/or placentas) were diagnosed as leptospirosis by the FAT (14 of 15 tested) and/or microscopic agglutination test (12 of 14 tested). Of the 12 serologically positive fetal fluids, 10 had high tigers against Leptospira interrogans serovar pomona and 2 against serovar grippotyphosa.

Prevalence of Leptospira infection in aborted pigs in Northern Ireland

During an investigation of pig abortions and stillbirths in Northern Ireland, leptospires were isolated from 55 of the 78 litters examined. Strains belonging to four serogroups (Australis, Icterohaemorrhagiae, Hebdomadis and Autumnalis) were recovered but leptospires of the Australis serogroup accounted for 91 per cent of the isolates. Two serovars of the Australis group bratislava and muenchen, were identified.

Leptospirosis: I. Clinical investigation of the infection in dairy cattle in the Waikato district of New Zealand

An investigation was made into the prevalence of leptospiral infection in cattle. An area 50 km radius was selected in a region where leptospirosis was reputedly common. Farmers volunteered 250 herds with 39 500 cows for testing and 7 500 animals were selected and sampled. Twenty-nine cows (0.4%) on 14 (5.6%) of the farms had leptospiruria at the first examination. Leptospirae were cultured from the urines of nine of these animals and all were Leptospira interrogans serovar hardjo. Serologically 12.5% of cows had titres of 1:200 or greater to hardjo and 3.5% titres of 1:200 or greater to pomona. In the Spring of 1977, there was evidence of clinical leptospirosis in calves associated with only one of the herds and no clinical leptospirosis in the 250 lactating herds, although leptospiral titres were found in 88% of them. This indicated that clinical disease was much less common than infection. We concluded that leptospirosis was of minor economic importance in dairy cattle, although it could be significant in individual herds, and a health hazard to farm workers.