Assessment of the efficacy of an IgM-elisa and microscopic agglutination test (MAT) in the diagnosis of acute leptospirosis

In a prospective study in Barbados between 1979 and 1989, 321 cases were diagnosed in 638 patients presenting at a hospital with symptoms of leptospirosis. Initial diagnosis was based on patient history and characteristic signs and symptoms. In 92 cases (29 percent), diagnosis was confirmed by isolation of organisms from the blood, urine, or dialysate fluid; in the remaining 229 cases (71 percent) diagnosis was confirmed by serology alone. Results of an IgM-ELISA and microscopic agglutination test (MAT) in cases with isolates and in non-specificity of the tests. The sensitivity of IgM detection by ELISA was 52 percent in the first acute-phase specimen, increasing to 89 percent and 93 percent in the second acute-phase specimen, increasing specimens respectively. The specificity of the IgM-ELISA was high (> or =94 percent) in all specimens. The sensitivity of the MAT was low (30 percent) in the first acute-phase specimen, increasing to 63 percent in the second acute-phase specimen and 76 percent in the convalescent specimen. The specificity of the MAT was > or = 97 percent in all specimens. (AU)

Surveillance of leptospiral carriage in feral rats in Barbados - abstract

Rodents, particularly rats, are widely held to be the source of most human cases of leptospirosis. Feral rats were trapped at sites throughout the island of Barbados during two six month surveys, from October - March 1986/87 and 1994/95. During the first survey, 63 rats were trapped, of which 26 (41 percent) were identified as Rattus rattus and 37 (59 percent) as Rattus norvegicus. In the second study, 100 rats were trapped, of which R. rattus comprised 24 percent (24) and R. norvegicus 76 percent (76). Cultures of blood, urine and kidney were made in EMJH medium. Leptospira were isolated from 12/63 (19 percent) and from 16/100 (16 percent) of the rats during 1986/87 and 1994/95, respectively; 27/28 isolates were recovered from the kidneys or urine or both, while only one isolate was recovered from blood. During the first study, isolates were identified as serovars copenhageni (11) and arborea (1), while in the second study, serovars copenhageni (9), arborea (5) and bim (1) were identified; one isolate was lost before it could be identified. In the first study, antibodies were detected by microscopic agglutination at a titre of > 100 in 26/62 (42 percent) of rats tested, while in the second survey, 5/100 (5 percent) of rats had similar titres. In two surveys, conducted eight years apart, we confirmed that rats in Barbados are commonly infected with leptospira, and that viable organisms are found in the kidneys and urine, evidence of chronic infection and thus excretion of leptospira in rodent urine. Moreover, the predominant serovar isolated was copenhageni, of which Rattus spp. are the worldwide reservoirs. There was little evidence that rats act as a reservoir for the serovar bim, the most common cause of human leptospirosis in Barbados. (AU)

Use of the polymerase chain reaction for rapid diagnosis of leptospirosis - abstract

Leptospirosis is endemic in Barbados with 97 percent of severe cases caused by three serovars of leptospira interrogans. Early diagnosis is important since the disease can run a fulminant course and patients may die before the appearance of characteristic clinical manifestations of Leptospirosis and/or leptospiral antibodies are detected, and therefore the disease may go unrecognized. In this study, the potential of the polymerase chain reaction (PCR) was explored for the early diagnosis of leptospirosis, with a view to detecting leptospirosis within the first ten days of the onset of the disease. Blood and urine samples from 83 patients with leptospirosis admitted to the Queen Elizabeth Hospital, Barbados, between January 1990 and December 1992, were examined serologically, by culture and by PCR. The mortality rate during the study period was 8.4 percent. PCR was more often positive than culture for the detection of leptospires in proven cases by antibody titre and detected the presence of leptospires in sera before the development of antibodies. As culture can take up to 13 weeks, it does not contribute to an early diagnosis. Seroconversion usually occurs on about the seventh day of the disease, thus diagnosis by serology can take a week or more to be decisive. PCR, on the day of admission, and the characterization of PCR products by Southern hybridization can be completed within one or two subsequent days. PCR is potentially a valuable addition to the diagnostic process in leptospirosis (AU)

An investigation of some risk factors for severe leptospirosis on Barbados

Between November 1979 and the end of December 1986 (7.17 years), 248 cases of leptospirosis were confirmed among hospital patients on Barbados (mean 35 per year; range 25-57). Considering the 235 who were greater than or equal to 15 years of age, the annual incidence of leptospirosis was 19.2/100,000 population (14.0 for all age groups). There were 173 males and 62 females, and for cases aged 15-34 leptospirosis was 9.6 times more common in men than women. Among men, incidence increased fairly steadily with age, and an even steadier increase was apparent in women up to age 64, with some decline in later years. The incidence of disease was much higher among agricultural than other workers and the un-employed. Highest case numbers were recorded in the parishes of St Michael (65 or 28 percent) and Christ Church (36 or 15 percent), though the incidence was lowest in these two parishes (13.1/100,000 and 17.4/100,000, respectively). The highest incidence rates were in St Andrew and St Joseph ((50.2 and 36.1/100,000, respectively). The incidence in areas with rainfall greater than or equal to 1600 mm (32.6/100,000) was nearly twice that in areas with rainfall less than 1600 mm (17.3/100,000). There is a clear link between cases of severe disease and recent rainfall. Using 134 patients greater than or equal to 15 years of age with fever due to other illnesses as controls, a higher proportion of cases than controls came from rural areas. The risk of contracting leptospirosis was increased for all categories of manual workers relative to the group at lowest risk (non-manual indoor workers). Sugar-cane workers were five times more likely to contract leptospirosis than were non-manual indoor workers, while those with rodents in their garden/yard were 1.8 times more likely to do so. Other risk factors examined did not show significant associations with the disease. Despite increasing mechanization and the use of more protective clothing, agricultural workers are still at high risk from leptospirosis. The annual range of cases is likely to stay much as it is in the foreseeable future. (AU)

Leptospires isolated from toads and frogs on the island of Barbados

Four pathogenic strains of leptospires were isolated from the kidneys of toads (Bufo marinus) and seven from frogs (Eleutherodactylus johnstonei). Isolates from two toads and one frog belonged to serovar bim, the causative agent of most cases of severe leptospirosis on Barbados. The other eight strains belonged to a new serovar within the Australis serogroup. The name bajan is proposed for this new serovar of Leptospira interrogans. (AU)

Retention of leptospiral agglutinins and long-term response to administration of monoclonal antibodies in vervet monkeys (Cercopithecus aethiops) on Barbados

In a study of 21 wild-caught Barbadian vervet monkeys (Cercopithecus aethiops sabaeus), naturally-acquired leptospiral agglutinins were found to persist for over five years. Groups of seropositive as well as seronegative vervets were given a placebo, or full-strength monoclonal antibodies MCA F12C3 (Icterohaemorrhagiae copenhageni), or diluted F12C3 MCAs. They were challenged 24 hours later with a suspension of highly virulent leptospires (copenhageni) administered intraperitoneally. Immunoprotection was evident in animals receiving full strength MCAs as measured by their failure to develop any sunstantial antibody response and by their lower geometric mean titres over a period of 142 weeks (maximum GMT of 113 compared with a maximum of 1280 in the placebo group). Diluted MCAs had little or no protective value. The serological response of the monkeys which were seropositive at capture to challenge with virulent copenhageni antigen was strongly anamnestic both in those given MCAs and those given placebo. None of the naturally or experimentally infected vervets showed clinical signs of leptospiral illness. (AU)

The sero-epidemiology of subclinical leptospirosis in Barbados - abstract

In an investigation of the relationship between serogroup, titre and age in subclinical leptospirosis, a further analysis was made of some of the data from three published surveys. Altogether, the records of 336 seropositive subjects were re-examined. The previously noted increase in seropositivity prevalence with age was found to be due mainly to a sharp increase in the prevalence of antibodies to serogroup Autumnalis; the prevalence of antibodies to serogroup Panama was found to decline. Similarly, despite the previously noted increase in titre with age, titres to serogroup Panama were found to fall. Panama is the serogroup most commonly recorded in children. The steep rise in the prevalence of Autumnalis with age, and the increasing, titres, suggest an anamnestic response to re-exposure, both to Autumnalis and to related serogroups. The Leptospira serovar producing antibodies in Barbadian subjects may be a semi-saprophytic form (AU)

Absence of epidemicity of severe leptospirosis in Barbados

The possibility of micro-epidemics of severe leptospirosis occurring on the island of Barbados was investigated by examining the space-time clustering of the disease in 212 laboratory confirmed cases admitted to Queen Elizabeth hospital, Bridgetown, over a 7-year period. A series of 109 patients with symptoms compatible with leptospirosis but shown to be otherwise by laboratory examination were also examined for comparison. No significant space-time clustering was found among the leptospirosis cases, indicating no evidence for micro-epidemics. By comparison, statistically significant clustering was apparent among the smaller non-leptospirosis series. Possible explanations for the absence of observed micro-epidemics of leptospirosis are discussed. (AU)

Hyperamylasemia and pancreatitis in leptospirosis

Hyperamylasemia has been documented in up to 65 percent of our patients with leptospirosis and jaundice. However, pancreatitis is an uncommon complication of leptospirosis. Three patients with leptospirosis and pancreatitis are described and compared with two leptospirosis patients who had hyperamylasemia but in whom the diagnosis of pancreatitis could not be substantiated. The cause of the hyperamylasemia in the latter patients was nonpancreatic. The elevation of the amylase in these latter two patients could not be explained by renal insufficiency, because the level of the amylase was greater than three to fourtimes the normal value, the upper limit to which amylase rises in renal failure.Thus, hyperamylasemia in patients with leptospirosis can be from pancreatic and nonpancreatic sources. Leptospirosis should be considered in the differential diagnosis of hyperamylasemia and pancreatitis (AU)

Leptospiral infection: a household serosurvey in urban and rural communities in Barbados and Trinidad

A longitudinal study of leptospiral agglutinins in subjects five years of age and over was undertaken in Trinidad and Barbados between 1980 and 1982. Households were sampled randomly from one urban and two rural communities on each island, giving a total of 576 eligible individuals in Barbados and 524 in Trinidad. Participants were examined three times at approximately annual intervals. The prevalance of seropositivity at a titre of 1:50 using the microscopic agglutination test was 18.5 percent in Barbados and 21.9 percent in Trinidad. Prevalence increased steeply with age in both sexes and was higher in males than females on both islands. There was a marked difference in predominating serogroups on the two islands--Autumnalis (42 percent of positive cases) predominated in Barbados while Bataviae (29 percent of positive cases) predominated in Trinidad. Estimates of incidence rates for seroconversion were 2.9 percent per annum for Barbados and 3.5 percent per annum for Trinidad. Occupational risk varied between the islands, but in both cases highest seropositivity rates (greater than 50 percent) were found in outdoor labourers and lowest were found in indoor non-manual workers and urban homeworkers. In Barbados seroprevalence was higher among persons who cleared drains or who had contact with livestock. Lack of an island toilet was associated with an increase in seropositivity on both islands. There was little evidence of household clustering of seropositive cases. (AU)

Leptospires in the whistling frog (Eleutherodactylus johnstonei) on Barbados

Two groups of whistling frogs (Eleutherodactylus johnstonei) comprising 99 and 117 animals were examined for leptospiral infection. Group I animals were caught in 14 areas of Barbados, and group II animals in seven areas of suburban Bridgetown. Leptospires were isolated from the kidneys or body fluid of six frogs in Group I and the kidneys of 3 frogs in Group II. Two of the group I isolates died; the others were identified as bajan (a new serovar in the Australis serogroup) (6) and bim (Autumnalis) (1). The macerated body tissues and fluid of Group I frogs were put into phosphate buffered saline and examined by the microscopic agglutination test using 22 antigens. The results were all negative. For the Group II frogs the methodology was altered; blood was collected unto filter paper discs and allowed to dry out before being agitated in PBS and examined by the MAT. 15/117 (12.8 percent) animals were positive at o 1:50. The geometric mean titre was 179. Seventeen of the sera reacted predominantly to antigens in the Australis serogroup, and two to Pyrogens on its own. The serological results reflected the identity of the isolates. Serovars of Australis are not known to cause illness on Barbados, but bim is the commonest cause of severe leptospirosis on the island. (AU)

Leptospirosis in Barbados: a clinical study

A 39-month clinical study of leptospirosis was undertaken at the Queen Elizabeth Hospital, Barbados. Eighty-eight patients had a confirmed diagnosis of the disease during the period. The major serogroups identified were autumnalis (including a new serovar bim), icterohaemorrhagiae, ballum and canicola. The majority of patients presented with jaundice (95 percent), anorexia and headaches (85 percent), fever (76 percent) and conjunctival suffusion (54 percent). While abnormal creatinine levels were seen in 49 percent of patients on admission, only 16 percent were judged to have renal failure. The urine to plasma urea ratio showed high sensitivity and specificity in the diagnosis of pre-renal azotemia. Cardiac arrthymias and myocarditis occurred in 18 percent of patients and pericarditis in 6 percent. An elevated serum amylase was found in 65 percent of cases. The bilirubin level took 5.5 weeks to return to normal. Thrombocytopenia was shown not to be due to a disseminated intravascular coagulation, and a randomised trial dose penicillin did not reveal any benefit to jaundiced patients. The overall mortality during the study was 5.7 percent (AU)

Persistence of leptospiral agglutinins in Trinidadian survey subjects

Participants in a survey for leptospiral agglutinating antibodies undertaken in Trinidad, West Indies, in 1977-78, were further monitored for up to 5-and-a-half years. 52 individuals with a titre >1:400 were matched for age, sex and occupation with seronegative subjects. They were re-bled twice (on average 2.38 and 4.84 years leater), and changes of titre were noted. At the first follow-up, 78 percent of negative controls remained negative, and 22 percent, showed titre changes. Among the seropositive subjects, 47 percent showed a fall in titre, 38 percent showed no change, and in 15 percent the titre rose. New exposure rates between the original and fist follow-up samples were 96/1,000 survey population per year in the controls, and 68/1,000 for the subjects with titres >1:400. Between the first and second follow-up, 47 percent ofthe seropositive subjects lost titre, 40 percent showed no change, and 13 percent showed a rise in titre. These data demonstrate that although antibody titre may be maintained for a few years at the same level, or show a loss as is usually expected, about 8.3 percent of individuals in Trinidad may be infected/reinfected per year. The infection/reinfection rate is an important factor in the epidemiology of leptospirosis. (AU)

Leptospiral infection in school-children from Trinidad and Barbados

A serological survey for leptospiral agglutinins was undertaken between 1980 and 1983 in over 500 Barbadian and 500 Trinidadian school-children aged 7-14 years. The children were selected randomly from urban and rural schools, and examined three times at approximately annual intervals. A total of 12.5 percent of the Barbadian children and 9.5 percent of the Trinidadian children were seropositive at a titre of 50 using the microscopic agglutination test. On both islands, seroprevalence was higher in males than females, the difference being significant in rural schools. There was no evidence of a difference in prevalence between urban and rural schools, or between junior and secondary age-rangers. Analysis of the association of serology with socio-economic and behavioral factors showed a significant association in Trinidad with father's occuption, but most other variables on both islands showed only weak non-significant associations. Fourteen children in Trinidad and three in Barbados seroconverted. Seroconversion in Trinidad occurred at a rate of 1.6 percent per annum and was significantly associated with livestock contact and with absence of tapped water supply. In Trinidad, Autumnalis was the most commonly recorded serogroup, but this accounted for less than a quarter of seropositives. In Barbados, Panama accounted for over half the seropositives and was about four times more common than the next most common serogroup, Autmnalis. In Barbados, 39 persons aged 19 or less were hospitalized with leptospirosis between November 1979 and December 1986. Average annual incidence rates were 2.2, 4.9 and 13.3 per 100000 in the 5-9, 10-14 and 15-19 age-groups, respectivley. (AU)

Leptospirosis in piggery workers on Trinidad

Of 133 cases of human leptospirosis recorded in Trinidad between 1977 and the end of February 1982, at least eight (6 percent) were in people who worked on pig farms. Three of the eight died,and their presumptive infecting serogroups were Icterohaemorrhagiae (3), Canicola (2), Pyrogenes (2) and Grippotyphosa(1). Six of the eight cases followed up. Altogether, sera from 201 pigs, 78 other livestock animals, 38 workers and 34 dogs were tested for leptospiral agglutinins. The seropositivity prevalence among pigs on farms with human illness(43 percento1:100) was similar to that in pigs from farms not associated with illness (46 percent), but the titres among the former group (geamatic mean 209.5) were higher than among the latter (91.5), where only titers ó1:400 were recorded. Similar infecting serogroups were recorded among pigs on the two groups of farms, with Icterohaemorrhagiae, Autmnalis, Canicola and Pyrogenes most frequently recorded overall. There was little evidence of the pig-adapted serogroups Pomona and Tarassovi. Twelve of 13 workers (93 percent) from a farm on which at least two other people had contracted leptospirosis had serological evidence of exposure, compared with seven of 24 (29 percent) on a neighbouring farm not associated with human illness. Dogs and rodents are thought to be the major sources of leptospirosis in pigs and piggery workers in Trinidad. (AU)

The prevalence of leptospiral antibodies in a health Tobago community - abstract

Between 1976 and 1982, blood was collected from all consenting adults in a known censused area of Plymouth, Bethesda in Tobago. Serum was tested using the ELISA test. One hundred and seventeen of 532 persons showed evidence of exposure to leptospires at titres of > 1:50. The serogroup most commonly detected was Bataviae. Agricultural workers tended to have high exposure rates particularly to Pyrogenes, Syroe, Bataviae and Canicola. The presence of animals associated with the homes studied appeared to increase exposure to leptospires (AU)

A serological survey for leptospiral agglutinins among patients in a Barbadian general practice - abstract

Sera from 1,419 patients who attended a Barbadian general practice for a variety of complaints between 1st April and 30th April 1988 were examined for leptospiral agglutinins by the microscopic agglutination test. Sera from patients presenting with pyrexia of unknown origin, jaundice or kidney complaints, and from those whose titre was > 1:400, were also examined by the ELISA for IgM and IgG antibodies. Only one patient was diagnosed clinically as possibly having mild leptospirosis, but three others had been recently infected and some mild cases may have been missed. Altogether, 177 of the patients (12.5 percent) were positive at titres> 1:50. These were 104 of the 739 males (14 percent) and 73 of the 680 females (11 percent) (no statistically significant difference). Seropositivity tended to increase with age (p<0.01), and the highest rates were in agricultural workers (35 percent), labourers (24 percent) and non-manual outdoor workers (19 percent). The difference in seropositivity between the various indoor and outdoor occupational groups was highly significant (p<0.005). Autumnalis (31 percent of the sero postives), Panama (15 percent), Australia (14 percent) and Pyrogenes (11 percent) were the serogroups most commonly recorded among the seropositive patients. Autumnalis predominated in each of the main occupational groups except indoor non-manual workers where Panama, Pyrogenes and Australis occurred more frequently. Ninety-five per cent of the positive titres ranged between 1:50 and 1:400. Titres tended to increase with age, but there was no obvious association between higher titres and particular occupations (AU)

Urinary diagnostic indices in the management of leptospirosis: selection of patients for dialysis therapy

Cases of leptospirosis admitted to the Queen Elizabeth Hospital (QEH), Barbados, were assessed for the presence of "pre-renal azotaemia" (NON-ARF) as opposed to "acute renal failure" (ARF). Distiction between the two diagnoses was made on the basis of clinical course. Peritoneal dialysis was inappropriately utilised in 26 percent of patients receiving such therapy. This study evaluates diagnostic tests for pre-renal azotaemia, and acute renal failure in leptospirosis, and indicates guidelines for the management of azotaemia in such patients. U/P urea and osmolar ratios show high sensitivity and specificity in diagnosing pre-renal azotaemia. While "early" dialysis is essential for patients with acute leptospiral renal failure, in those with plasma creatinines less than 600 umol/litre on entry and indices indicating NON-ARF, decisions regarding dialysis can safely be delayed for 48-72 hours while the effect of rehydration is assessed (AU)