Distribution pattern of chigger mites in south Tamil Nadu, India

Chiggers, the larval Trombiculid mites are the vectors for scrub typhus. Rodents and shrews are the preferred host. Study made at different habitats of chiggers collected in rodents and shrews, revealed more number to Rattus rattus 95(63%) and Suncus murinus 33(22%). Rattus rattus 31(54%) and Suncus murinus 17(30%) alone contributed more in chigger positivity. Chigger mites belonged to eight species under five genera. Leptotrombidium deliense (66%), Schoengatiella ligula (15%), and other chiggers (9%) were collected from 57 positive rodents. Seasonally, there was a significant difference in rodent positivity, and there was no significant difference in the number of chiggers collected. The study indicated the prevalence of chiggers in the various hosts and their variation in rodent/shrew hosts. R. rattus 31(54%) and S. murinus 17(30%) contributed more in chiggers infestation and seasonally wet-cool months favored more chiggers and host positivity from different habitats.

Co-occurrence of Eutrombicula alfreddugesi and Oswaldofilaria chabaudi in Tropidurus torquatus and first report of microfilariae in the chigger mite: possible evidence of a lifecycle pathway?

While much attention has been paid to vector-borne filariasis, diseases that threaten millions of people in tropical and subtropical countries, the literature on host–parasite associations and transmission strategies of filarial nematodes in wildlife is scarce. Here, we report the co-occurrence of chigger mites (Eutrombicula alfreddugesi) and onchocercid nematodes (Oswaldofilaria chabaudi) parasitizing the lizard Tropidurus torquatus in the State of Minas Gerais, Brazil. Examination of chiggers established, for the first time, the occurrence of microfilariae in trombiculid mites (Trombiculidae). These larvae were morphologically similar to those recovered from adult females of O. chabaudi. The current evidence suggests that chiggers do not play a role in the transmission of filarioid nematodes, but rather act as accidental or dead-end hosts. Nevertheless, considering the polyphagous nature of trombiculid mites, similar to blood-sucking insects involved in the transmission of several infectious diseases, further studies may shed light on the potential role of chiggers as vectors of filarioids.

First identification of trombiculid mites (Acari: Trombiculidae) on rodents captured on Chiloé Island, an endemic region of scrub typhus in southern Chile

BackgroundScrub typhus in an emerging vector-borne zoonosis, caused by Orientia spp. and transmitted by larvae of trombiculid mites, called chiggers. It mainly occurs within a certain region of the Asia-Pacific, called tsutsugamushi triangle, where rodents are known as the most relevant hosts for the trombiculid vector. The disease has recently been discovered on Chiloé Island in southern Chile. Still, the reservoir(s) and vector(s) of the scrub typhus outside Asia-Pacific are unknown. The aim of the present work was to study the prevalence of chiggers on different rodent species captured in sites identified as probably hot spots of scrub typhus on Chiloé Island in southern Chile.Methodology/Principal FindingsDuring austral summer 2018, rodents were live-trapped in six sites and examined for chigger infestation. During a total of 4,713 trap-nights, 244 rodents of seven species were captured: the most abundant was Abrothrix olivacea. All study sites were rural areas on Chiloé Island, previously identified as localities of probable human infection with scrub typhus. Chiggers were detected on all seven rodent species with a 55% prevalence rate. Chiggers showed low host specificity and varied according to site specific host abundance. We identified trombiculids of three genera. Colicus was the most abundant chigger (93%), prevalent in five of six sites, followed by Quadraseta (7%) and Paratrombicula (7%), which were in only one site. Infestation rates showed site specific differences, which were statistically different using a GLM model with binomial errors.Conclusions/SignificanceThis study firstly reports the presence of different rodent-associated chigger mites in a region with endemic scrub typhus in southern Chile. Colicus and two other genera of mites were found with high infestation rates in sites previously identified as hot spots of scrub typhus, suggesting their role as vectors and reservoirs of this emerging zoonosis in South America.Author SummaryScrub typhus is a chigger-transmitted zoonotic infection, which is endemic in the tsutsugamushi triangle in Asia-Pacific. Recently, a first focus of scrub typhus in South America has been confirmed on Chiloé Island in southern Chile. Still, the vectors of scrub typhus in this region remain unknown. We undertook a survey to study the prevalence of chiggers on different rodent species in areas identified as probable hot spots of scrub typhus on Chiloé Island. The study showed that 55% of rodents were infested by trombiculids. Three chigger genera were identified, of which Colicus was the most abundant. Chiggers showed low host specificity, but spatial differences. This first demonstration of rodent-associated chigger mites in hot spots of scrub typhus suggests their possible role as vectors of this infection in Chile.

Scrub typhus: a case report

Scrub typhus is a rare rickettsial disease which is endemic in the state of Himachal Pradesh. It is caused by bacteria called Orentia tsutsugumasi and transmitted by larvae of Trombiculid mites. Though rarely seen in the plains, it should be kept as differential for a patient presenting as fever with seizure. Eschar may or may not be seen in all cases. We report a case of scrub typhus in a patient who presented with fever and seizures but no eschar.