The epidemiology of leptospirosis in North Queensland: I. General survey of animal hosts

Abstract

Leptospirosis is a zoonosis that causes appreciable ill health and economic loss in North Queensland. Fourteen serotypes ofLeptospirawere known to infect man in the area, and information on their local distribution and seasonal and occupational incidence had been obtained. The next step in the investigation was to determine the reservoir hosts and estimate their significance.Wild animals examined comprised 5 monotremes, 643 marsupials, 2355 rodents, 67 bats, 30 birds, 28 reptiles, and 21 toads. Evidence of leptospiral infection was obtained from 223 marsupials, 309 rodents, and 6 fruit-bats. Analysis indicated that the principal maintaining hosts were:Peremeles nasuta—ofL. kremastos(and possiblyL. mini) in canefields and rain forest.Isoodon macrourus—ofL. broomi, L. mini, andL. kremastosin canefields.Rattus rattus, R. norvegicus(focal), andMus musculus(focal)—ofL. zanoniin town and canefields.Rattus sordidus conatus—ofL. australisin canefields.Rattus assimilis—of foci ofL. australis, a variant ofL. pomona, and probably ofL. hyosin rain forests.Random infections were also encountered, but the maintaining hosts of the other serotypes known to infect man in the area (icterohaemorrhagiae, canicola, bindjei, robinsoni, bratislava, grippotyphosa, medanensis, celledoni) were not determined.Domestic animals examined included 137 cattle, 54 pigs, 7 sheep, 34 dogs, 31 cats, and a dairy herd in which there was an epizootic ofpomonaleptospirosis. Again, there was a wide scatter of infection, but, apart from the long-known association ofL. pomonaandL. hyoswith cattle and pigs, there was no evidence of maintaining hosts in this series.As indicated in the Introduction, the work reported here was part of a planned investigation into the epidemiology of leptospirosis. Some of the early material was collected by Dr M. J. Mackerras, Dr R. L. Doherty, Mrs D. G. Delamoir, and Miss C. J. Ross, who had previously been stationed at the Institute's Field Station, and we are indebted to Mr D. W. Lavers, Mr S. G. Knott, and Mr R. E. Dunham, of the Queensland Department of Agriculture and Stock, for a number of sera from domestic animals. Many of the mammals were identified by Dr W. A. McDougall, of the Queensland Department of Agriculture and Stock, Mr E. le G. Troughton, then of the Australian Museum, Sydney, Mr B. J. Marlow, then of the C.S.I.R.O. Wildlife Section, Canberra, and by Dr J. L. Harrison, Dr M. J. Mackerras, and Mr R. Domrow of the Institute. We are indebted also to Mrs M. Macgregor, Librarian of the Institute, for considerable help with the literature.

The epidemiology of leptospirosis in North Queensland: II. Further observations on the hosts in the Mossman district

“…The relative frequency of pomona infections is lower (22 %) than that (53 %) reported from the Douglas shire by Emanuel et al (1964).…”

“…New host records Isolation and identification of strains extended the proven host range of six serotypes ( (Emanuel et al 1964) was calculated for each association between serotype and host where the numbers permitted. The samples were small, but the figures may be considered to give an indication of which animals are the maintaining hosts of the two main serotypes, grippotyphosa and medanensis, under investigation.…”

“…On the other hand, I. macrourus had an infection rate of 13 % and excretion index of 0 07, so it may well be only an incidental host, as R. rattus presumably was in the earlier survey. (Emanuel et al 1964) and the serotype has been isolated only from these rodents. On these grounds it may be considered that Melomys species are the maintaining hosts of the serotype in this area.…”

Ecological aspects of the epidemiology of infection with leptospires of the Ballum serogroup in the black rat (Rattus rattus) and the brown rat (Rattus norvegicus) in New Zealand

“…The brown rat is generally regarded as the maintenance host for leptospires of the Jcterohaemorrhagiae serogroup and is an occasional carrier of other serovars (Babudieri, 1958;Fennestad & Borg-Petersen, 1972;Michna & Ellis, 1974). The black rat is a less frequent carrier of leptospires (Broom, 1958;Emanuel, Mackerras & Smith, 1964;Torten et al 1970). …”

EXPERIMENTAL INFECTIONS OF BRUSH‐TAILED POSSUMS, COMMON WOMBATS AND WATER RATS WITH LEPTOSPIRA INTERROGANS SEROVARS BALCANICA AND HARDJO

“…Emanuel et al (1964) noted that water rats appeared to be accidental hosts for several leptospires but reservoir hosts for none. The results of the present study support this and suggest that water rats are probably poor reservoir hosts for either hardjo or halcanica.…”