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The diagnosis of trombiculiasis in a cat was based on the presence of an orange, crusting dermatosis, and identification of 6-legged larvae in skin scrapings. The prevalence of the disease may be higher than suggested by the number of reports in the literature, and due to the lack of pruritus, often may be overlooked.
We found trombiculid mite (Trombiculidae) infestations in 32 of 101 (32%) freeranging Florida black bears (Ursus americanus floridanus) live-captured or necropsied in Florida from January 1999 to April 2000. Prevalence of chigger infestation was greatest in June with no infestations seen October to March. Chigger infestations were recognized as accumulations of bright orange granular material usually associated with hair shafts. Mites were found in clusters of one to 102 (mean +/- SD = 8.5+/-19.5) and were distributed primarily over the ventral abdomen and thorax, inguinal and axillary regions, and proximal medial aspect of the extremities. Mites were identified as larval Eutrombicula splendens. Cutaneous lesions were seen in two of 32 (6%) infested bears.
In four villagers parasitic prurigo caused by the autumnal chigger (Neotrombicula autumnalis) was diagnosed. The clinical picture consisted of intensely itchy, erythematous papules, at sites where clothes fitted tightly or in body folds. Further investigation in the village revealed that in 16 of the 48 homes at least one person in the preceding two months had suffered from prurigo possibly caused by the autumnal chigger. The characteristics of the parasite, the clinical picture, treatment and prevention are discussed.
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Larval Leptotrombidium deliense were recovered from live-trapped Suncus murinus, Rattus rattus and R. norvegicus captured in the Pescadores Islands of Taiwan during 1976 and 1977. Weekly and monthly indices of chigger infestation expressed as a percentage of hosts infested and the number of chiggers per host for S. murinus and Rattus spp. were calculated. Close correlations were observed between monthly indices of L. deliense measured for S. murinus and Rattus spp. and the number of laboratory-confirmed cases of scrub typhus per month. Weekly indices from S. murinus correlated more closely with number of cases than did weekly indices from Rattus spp. The critical level of chigger infestation necessary for a single case of scrub typhus in a month was estimated at 0.69 chigger per S. murinus and 0.68 chigger per Rattus spp. The weekly index of chigger infestation necessary for a single case of scrub typhus during a week was calculated at 0.47 chiggers per shrew. Critical levels of chigger infestations expressed as percentages of hosts infested were not calculated.
A total of 10 strains of Orientia tsutsugamushi were isolated from field rodents and chiggers in Taiwan, and characterized by immunofluorescence analysis with monoclonal antibodies and by restriction fragment length polymorphism analysis of the 56-kilodalton (kDa) protein gene. The isolates were divided into two groups consisting of 1 and 9 strains which showed some relation to Gilliam and Karp type strains, respectively. However, all these isolates possessed characteristics distinct not only from those of known prototype strains including Gilliam and Karp but also from all isolates from Japan. These findings suggest the existence of a large number of immunotypic and genotypic variants among the strains of O. tsutsugamushi, and the distribution of distinguishable strains in each area to which this species is endemic.
Chigger infestation is often associated with severe cutaneous reactions. Mice were given four infestations with the pest chigger Eutrombicula cinnabaris, and each exposure was separated by a 14-day mite-free period. Mean duration of engorgement was nine to ten days for a first exposure and four to five days for a fourth exposure. An initial exposure did not elicit macroscopic changes at chigger attachment sites, while all third and fourth exposure animals had marked reactions consisting of erythema, epidermal thickening and serous exudation. Approximately 20% of second exposure animals had macroscopic changes at chigger feeding sites, but these reactions were much less intense than the responses of third and fourth infestation hosts. Third and fourth exposure animals had infiltrates of lymphocytes, eosinophils, basophils and neutrophils at attachment sites, with eosinophil influx the most intense. Cutaneous reactivity to chigger feeding was adoptively transferred with lymphocytes from fourth exposure animals. Passive transfer of serum from fourth infestation donors resulted in heightened reactivity to a challenge infestation. Skin testing, after a fourth infestation, with an extract of whole E. cinnabaris larvae provided evidence for Arthus and delayed type hypersensitivity responses to chigger antigens. Chigger-reactive homocytotropic antibody was not detected by skin testing and active cutaneous anaphylaxis.
Colicus spinosus Goff & Gettinger, n. sp., is described from Marmosa agilis. Quadraseta brasiliensis Goff & Gettinger, n. sp., is described from Marmosa agilis, Monodelphis americana, and Oryzomys capito. All specimens were collected in central Brazil. The diagnosis of the genus Arisocerus Brennan, 1970, is corrected to describe the setation of the palpal tarsus as 7BS rather than 6BS as listed in the original description.
In the Philippine Islands, the genus Leptotrombidium currently consists of members of the subgenera Leptotrombidium and Trombiculindus. The following species are described as new: L. (L.) macacaphilus, L. (L.) longimedian, L. (L.) mindanensis, L. (L.) urogale, L. (L.) oculascutum, L. (T.) roseannleilaniae. The distribution of, and comments on, the known vectors of Rickettsia tsutsugamushi, L. (L.) deliense and L. (L.) fletcheri and the previously reported L. (L.) sandfordi, are given. Information on species of the potential scrub itch genera Blankaartia, Eutrombicula, and Schoengastia and a key to the genera and species of medically important trombiculids is provided.
The ecology of Orientia tsutsugamushi (Hayashi) was studied in chiggers and small animals in an orchard near Bangkok, Thailand. Small animals were trapped monthly between July and November 1992 and examined for the presence of O. tsutsugamushi and ectoparasitic chiggers. A total of 40 Rattus rattus (L.) and 16 Tupaia glis (Diard) was trapped. O. tsutsugamushi was isolated from liver and spleen samples of 30.8% of R. rattus and 18.6% of T. glis. Antibodies to O. tsutsugamushi were detected in 95% of R rattus, and IgG antibodies persisted for up to 10 mo after removing rats from potential reinfection in the field. A total of 1,133 chiggers was identified and examined for the presence of O. tsutsugamushi using a direct fluorescent antibody test, and 2.6% Leptotrombidium deliense Walch, 5.1% Aschoshoengastia indica Hirst, 2.6% A. (Laurentella) sp. #2 and 0.9% A. (Laurentella) sp. #4 were infected. Forty-four pools of chiggers from these animals were triturated and injected into mice. Seven pools were obtained from T. glis and 1 was positive for O. tsutsugamushi, and 3 of 37 pools from R. rattus were positive. A proportion of the engorged chiggers collected was reared to the adult stage, and the progeny of these adults tested for the presence of O. tsutsugamushi. The progeny of 186 females was tested, and the progeny of 2 L. deliense was found to be naturally infected with O. tsutsugamushi.
A case of harvest-mite infestation acquired in the South Lakeland area is described in a 7-year-old boy and his immediate family. The characteristic papular urticarial lesions produced are extremely florid and may cause diagnostic problems when patients present in areas where the mite is uncommon. The life cycle of the harvest mite is discussed and recommendations for treatment given.
To evaluate the efficacy of fipronil in controlling trombiculid infestations, 18 dogs and three cats infested with Trombicula autumnalis larvae were treated monthly from examination to the end of the Trombicula season (range one to four months) with a 0.25 per cent fipronil spray applied to the whole body, with particular emphasis on the feet, face, ears, perineum and tail. No other antiparasite measures were used. Follow-up was by clinical examination and telephone interview until the end of the Trombicula season (range one to four months). No adverse effects were seen. Monthly treatment controlled trombiculids in 15 dogs. In two dogs localised pedal reinfestations were controlled with additional local application of fipronil to the feet every 14 days. In one dog therapy was of no benefit. In the three cats, treatment was initially effective, but generalised infestations recurred after seven to 10 days. Fipronil is a safe and effective treatment for trombiculid infestations in dogs. Residual activity lasts for 14 to 30 days. Further studies are required to examine the apparent short duration of efficacy in cats.
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During a routine blood collection at a wildlife management checkpoint, several white-tailed deer (Odocoileus virginianus) from Lake Russell Wildlife Management Area, Habersham County, Georgia, were observed to have accumulations of orange granular material around the eyes and mouth accompanied by serous exudate, crusting, and alopecia. Microscopic examination of the granular material disclosed numerous larval mites of the family Trombiculidae. Histologic examination revealed severe chronic diffuse plasmacytic dermatitis with intralesional larval trombiculid mites. Several stylostomes were also identified in the tissue sections. This paper describes the gross and histologic changes associated with severe trombiculid infestation in a white-tailed deer and suggests potential causes for this unusual finding.