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).

Evaluation of two methods for rapid serological diagnosis of acute leptospirosis

OBJECTIVE: To evaluate two rapid assays for serological diagnosis of acute leptospirosis in diagnostic laboratories. DESIGN AND METHODS: 209 specimens were examined from 104 patients admitted to hospital for investigation in a leptospirosis diagnostic protocol. Specimens for serology were taken on days 1 and 4 of the hospital admission. Antibodies were detected using IgM-ELISA, microscopic agglutination (MAT), an IgM-dipstick assay and indirect haemagglutination assay. RESULTS: 51 patients were found to have leptospirosis. The sensitivity of the IgM-dipstick was 98 percent, specificity was 90.6 percent, positive predictive value was 90.9 percent and the negative predictive value was 98 percent. The sensitivity of IHA was 92. percent, specificity was 94.4 percent, positive predictive value was 95.9 percent and negative predictive value was 92.7 percent. The IgM-dipstick assay was positive in 71 percent of the cases in the first sample tested. CONCLUSIONS: Both assays are highly sensitive and specific. Neither requires specialized equipment, and both are suitable for use in diagnostic laboratories.(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)

Surveillance of leptospiral carriage by feral rats in Barbados

Rodents, particularly rats, are widely held to be the source of most human cases of leptospirosis. Feral rats were trapped at sites throughout Barbados during two-six month surveys: from October to March 1986/87 and from October to March 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. Leptospires 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 the blood. During the first study, isolates were identified as serovars copenhageni (11), 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 > or = 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 aparts we confirmed that rats in Barbados are commonly infected with leptospires, and that viable organisms are found in the kidneys and urine, evidence of chronic infection and thus excretion of leptospires in rodent urine. Moreover, the predominant serovar isolated was copenhageni, of which Rattus spp. are the worldwide reservoir. 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)