Leptospiral carriage by Mice and Mongooses on the island of Barbados

Leptospirosis is a zoonotic disease, maintained by chronic infection of the kidneys of reservoir animals, usually small mammals. Infection in humans is acquired from direct or indirect exposure to the urine of infected animals. Leptospirosis has a high incidence in tropical regions, and has been studied extensively in several Caribbean countries. We studied the carriage of Leptospira serovars by two small mammals which are potential maintenance host of the disease in Barbados. A total of 136 mongooses (Herpestes auropunctatus) and 97 mice (Mus musculus) were caught in live traps. Leptospiral antibodies were detected by microscopic aggutination test (MAT) using antigens representing 12 serogrouops, and kidney tissues were inoculated into polysorbate medium for isolation of leptospires. The seroprevalence (at a titre of o 100) in mice was 28.2 percent (24/85, 95 percent CI 19.0, 39.1) and in mongooses 40.7 percent (48/118, 95 percent CI 20.1, 39.0) and from 4 mongooses ( 2.9 percent, 95 percent, CI 0.8, 7.4). Mouse isolates were identified as serovars arborea (17) and bim (7). As in other parts of the world, common house mice (Mus musculus) represent a significant reservoir of leptospirosis. Although carriage of the Ballum serovar, arborea, was not unexpected, this represents the first time that an animal reservoir of serovar bim has been identified. This is significant because bim causes about 63 percent of human leptospirosis in Barbados, and control efforts and education for prevention can now be targeted at a specific reservoir. (AU)

Severe leptospirosis in Barbados

Leptospirosis was confirmed in 134 Barbadian patients between November 1979 and December 1982. The average annual number of cases was 42.3 or approximately 17 cases/100,000 population/year. There were 90 males and 44 females (2:1 ration with ages ranging from 9 - 86 years. In 94 cases the infecting leptospiral serogroups could be identified with certainty. They were Autumnalis 68 (72 percent), Icterohaemorrhagiae 18 (19 percent), Ballum 6(6 percent), Canicola 1 (1 percent) and Grippotyphosa 1 (1 percent). A further 25 cases showed mixed infections with Autumnalis/Icterohaemorrhagiae accounting for 14 of them. Eleven of 14 isolates obtained from hospital patients were identified as Autumnalis (7) (new serovar, to be named bim), A. bulgarica (1), Icterohaemorrhagiae copenhageni (2) and Canicola canicola (1). Twenty-five (19 percent) of the patients died (averag 8/year). There were 14 males: 11 females. Just under half of the fatal cases were < 50 years of age, and a quarter of them were between 20 and 39 years. The serogroups found in 16 of the dead patients were Autumnalis (9), Autumnalis/Icterohaemorrhagiae (1), Autumnalis/Ballum (2), Icterohaemorrhagiae (3), and Ballum (1). Thus Autumnalis could have been the infecting group in 12 of 16 (75 percent) of the fatal cases. The majority of Autumnalis infections are probably caused by the new serovar. Although it is antigenicalyy very similar to fort-bragg it appears to cause severer illness than the latter. since Autumnalis infections are responsible for at least (72 percent) of all cases and up to 75 percent of deaths, Autumnalis bim appears to be the major cause of severe human leptospirosis in Barbados (AU)