Monthly Occurrence of Vectors and Reservoir Rodents of Scrub Typhus in an Endemic Area of Jeollanam-do, Korea

Monthly surveys were conducted to investigate the occurrence of chigger mites and seroprevalence of scrub typhus among small mammals in Jeollanam-do, the southwestern part of Korea, from November 2006 through October 2007. Fifty-eight small mammals, including 57 Apodemus agrarius (98.3%) and 1 Crocidura lasiura (1.7%), were captured, and a total of 4,675 chigger mites representing 4 genera and 8 species were collected from them. The chigger infestation rate among small mammals was 69.0%. The most predominant species in A. agrarius was Leptotrombidium scutellare (54.0%), followed by Leptotrombidium pallidum (39.4%), Leptotrombidium orientale (4.4%), Leptotrombidium palpale (1.1%), Neotrombicula tamiyai (0.6%), Eushoengastia koreaensis (0.3%), Neotrombicula gardellai (0.3%), and Cheladonta ikaoensis (<0.1%). The chigger index of A. agrarius was the highest in October (740.0), followed by November (242.0), September (134.6), March (98.3), February (38.2), January (35.3), December (34.5), April (30.8), and May (1.7). The average antibody positive rate of scrub typhus in wild rodents was 50.0%. The seropositive rates were high in October (100.0%) and November (83.3%), whereas those in other months were relatively low (28.6-57.1%). The chigger index of L. scutellare rapidly increased in September to form an acuminate peak in October, followed by a gradual decline. These results suggest that the outbreak of scrub typhus in the southwestern part of Korean peninsula is mostly due to L. scutellare.

Tunguíase / Tunguiasis

O autor faz uma revisäo da história, morfológia, biologia, clínica e terapêutica da tunguíase. Relata suas observaçöes destacando nove casos generalizados tratados com tiabendazol

Chigger mite infestation of small mammals in a feral biotope of a public park area of south Delhi.

Examination of Bandicota bengalensis (8) and Suncus murinus (4) trapped in a feral biotope of a public park area of south Delhi revealed presence of the known scrub typhus vector Leptotrombidium (L.) deliense, the suspected vector Gahrliepia (S.) ligula and Gahrliepia (Walchia) sp. of chigger mites, on them. The epidemiologically important population indices (chigger infestation rate-CIR and incidence rate--1R) were estimated. The overall CIR of the three mite species on the hosts was 2.83 mite/host, and that of L. deliense on B. bengalensis and S. murinus was 1.62 and 0.25 respectively, whereas that of G. ligula was 0.50 on both the host species. The overall 1R was 66.66 per cent being 62.5 per cent for B. bengalensis and 75.0 per cent for S. murinus. Incidence of L. deliense on B. bengalensis was higher (62.5 per cent) than on S. murinus (25.0 per cent), whereas IR of G. ligula was higher (50.0 per cent) on S. murinus than on B. bengalensis (25.0 per cent). The Chi square test of independence has shown that these chigger species are not host specific, but are rather habitat specific. Chiggers were absent on Mus platythrix from a habitat about 40 meters away from the B. bengalensis and S. murinus collection sites. The high CIR value for scrub typhus vector L. deliense (1.62) warrant investigations on natural infection rates of R. tsutsugamushi in the chiggers and screening of local human population for the infection.