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

Abstract

SUMMARYEpidemiological aspects of infection with leptospires of the Ballum serogroup in black rats (Rattus rattus) and brown rats (Rattus norvegicus) are described. Rats inhabiting a variety of habitats were investigated and isolates identified as belonging to the Ballum serogroup were obtained from 21 of 61 black rats (34 %) and 63 of 243 brown rats (26 %). The high level of endemic Ballum serogroup infection in these species reported here has not been described in other countries.A statistical relationship was shown between the prevalence of infection in brown rat populations and population density but this was not evident for black rats. Epidemiological data indicates that the black rat is a maintenance host for leptospires ofthe Ballum serogroup in New Zealand. The brown rat does not appear to be an efficient maintenance host for these leptospires, however endemic infection can be maintained in high-density populations inhabiting synanthropic foci.

Carriage of Leptospira interrogans among domestic rats from an urban setting highly endemic for leptospirosis in Brazil

“…Both rodent control and the infrastructure of the sewage system were observed to be of a higher standard in these areas and may explain the failure to trap any animals. Compared to other surveys where carriage rates ranged from 4 to 59% when based on culture isolation (Thiermann, 1977; Carter and Cordes, 1980; Hathaway and Blackmore, 1980; Pereira and Andrade, 1988; Taylor et al, 1991; Webster et al, 1995; Levett et al, 1998; Vado-Solis et al, 2002; Sharma et al, 2003; Vanasco et al, 2003; Priya et al, 2007), our results detected a much higher proportion (>80%) of leptospiral carriage among captured rats. In a survey carried out over 50 years ago in the city of Salvador, the carriage rate in rats was reported to be 29% by silver impregnation of kidney samples (Andrade and Oliveira, 1954).…”

Prevalence ofLeptospiraspp. in wild brown rats (Rattus norvegicus) on UK farms

“…Its presence within rat populations may suggest that it is a recently acquired leptospira and/or that rats are normally incidental rather than maintenance hosts for this serovar. Wild brown rats in New Zealand, which are maintenance hosts for copenhageni are incidental carriers of ballum at low population densities but become maintenance hosts at high densities [18,22]. The two farms with bratislava in our study had the largest rat populations (Table 1).…”

“…Low prevalence might have arisen if the age structure of rats trapped was biased, for example towards juveniles or sub-adults, since a number of workers have found significantly lower prevalences within younger rats [7,22]. Yet, not only was our sample not biased, the FA technique indicated an approximately equal leptospira prevalence within each age-category.…”

Leptospira and Leptospirosis

“…For example, in a New Zealand study the brown rat did not maintain Ballum infection under most conditions, but it did so when present in high density populations found on rubbish dumps (Hathaway and Blackmore 1981). Other host maintained infections have a more limited geographical spread either due to limitations in host distribution or to unrecognized factors, e.g., serovars Kenniwicki or Tarassovi infection in pigs.…”