Eutrombicula tinami (Oudemans, 1910) (Trombidiformes: Trombiculidae) in Brazil: a neglected ectoparasite of several animals including humans

The genus Eutrombicula comprises ca. 80 species worldwide, some of which have been reported as causative agents of severe irritation to the host’s skin, known as trombiculiasis. Six species of Eutrombicula have been recorded from Brazil until present, with two reports of humans as hosts. In this study, Eutrombicula tinami (Oudemans) is redescribed and new records for the states of Minas Gerais, Rio de Janeiro, Santa Catarina and São Paulo as well as new parasite-host associations with Columbiformes, Cuculiformes, Passeriformes, Tinamiformes, Carnivora, Didelphimorphia and Lagomorpha are listed. Besides that, a two detailed report cases of trombiculiasis is provided.

In the northern region of Brazil, locals use the term 'micuim' for chiggers, but in the southern region, there is no common name, suggesting most Brazilians including the medical community are unaware of chigger and their medical importance.
Here we redescribe E. tinami, with new locality and host records as well as new human trombiculiasis records.

Material and methods
The Instituto Butantan houses the Acari Collection (IBSP) that receives material from various parts of the country. Specimens deposited in this collection are regularly prepared for identification. Of these, two hundred chiggers belonging to the genus Eutrombicula, previously stored in Ethanol (100%) were slide-mounting in Hoyer's medium and some were prepared for scanning electron microscopy (SEM), both preparations according to Walter and Krantz (2009). Drawings were made with a Leica DFC 500 microscope. Extended focal range images were composed with Leica Application Suite version 2.5.0. The scanning electron microscope photographs were obtained using a Digital FEI-Quanta 250 at the Laboratório de Biologia Celular, Instituto Butantan, São Paulo. The distribution map was prepared using DIVAGIS. All the images were prepared with Adobe Photoshop v. 13.0 and Inkscape V.2. Species identifications involved using the key by Brennan and Reed (1974), and original species descriptions. Additional sources included redescriptions of Eutrombicula by Oudemans (1912), Jenkins (1949) as well as illustrations by Brennan and Reed (1974). The terminology follows Bassini-Silva et al. (2018) and Jacinavicius et al. (2018b).
In the present study we also report the parasitism by E. tinami on two humans, one male 39 y/o and other female 31y/o, who were walking in the Atlantic Rain Forest (45°19'28" W, 23°33'42" S) between 9 am and 12 pm on an unspecified day November 2014.

Systematics
The chigger specimens were identified as E. tinami (Oudemans, 1910). Additional specimens from Minas Gerais, Rio de Janeiro, Santa Catarina and São Paulo states were studied and used to improve the redescripition of E. tinami presented below.

Figure 7
Lower leg of female bitten by Eutrombicula tinami (Oudemans, 1910). The arrows show the areas of papular dermatits.

Notes about the trombiculiasis
The subjects came in contact with larval E. tinami in the forest, which were noticed several hours later, around 6:00pm, mainly because of the onset of intense pruritus; at this moment one of the subjects (Author Fournier, G.F.S.R.) had specimens collected by application of adhesive tape, few larvae were collected from the tape at the stereomicroscope and further identified (IBSP 12522). The clinical signs consisted of areas of papular dermatitis located on the feet, legs, knees, hands, fingers, arms, face and scalp. The lesions were circular, focal and multifocal, with papular inflammatory reaction with a center papule and a hyperemic centrifuge halo of sizes ranging from 1 to 3 cm in diameter, probably caused by exuberant cellular inflammatory reaction with manifests severe pruritus and lasts for over 72 hours as described in other Eutrombicula species. No infection symptoms, such as fever, were present. The pruritus ceased after about five days without any medication. Neither subject consulted a physician or used medicine to kill the parasites or control inflammation. Both subjects used physical removal with a hard bath sponge during a shower about 10 hours after exposure, but it was not evaluated whether this action was efficient or not. Both subjects experienced the same symptoms and skin manifestations. Figure 7 shows the inflammatory papules on the female subject 24 hours after exposure.

Discussion
Host records suggest some Eutrombicula species are not host specific. This applies to E. tinami, which has been reported from multiple species of birds, rodents and marsupials (Oudemans 1910;Brennan and Lukoschus 1971;Reed 1974, 1975;Jacinavicius et al. 2018a).
Prior to this study E. tinami had been reported from only five hosts, Dielphis marsupialis from Surinam (Brennan and Lukoschus 1971), Proechimys semispinosus from Panama (Brennan and Lukoschus 1971), Marmosa robinsoni from Venezuela (Brennan and Reed 1974), Didelphis aurita from Brazil (Jacinavicius et al. 2018a) and the original host, Crypturus noctivagus, also from Brazil (Oudemans 1910). In this study, we recorded 207 E. tinami from 70 individual hosts representing 17 mammals and 53 birds sampled in Brazil. Mammals, including humans accounted for only 20% of the E. tinami recovered from hosts. All were new mammalian host records for this species, except for the host species D. aurita. Birds are important hosts for Brazilian E. tinami accounting for 80% of all the specimens recovered with 20 new host records in 15 families. The bird genus Turdus spp. appears to be a common host for E. tinami accounting for about half of all birds with E. tinami and nearly 60% of all specimens recovered.
This species was also found biting humans and joins E. alfreddugesi and E. batatas, in causing human trombiculiasis in Brazil.
Eutrombicula tinami was described for Brazil without specific locality information (Oudemans 1910). The only other published Brazilian record for this species was from a marsupial collected in the São Paulo, SP (Jacinavicius et al. 2018a). Here, we provide new records from the states of Minas Gerais, Rio de Janeiro, Santa Catarina and São Paulo. This species had Previously published records of this species from Panama (Brennan and Lukoschus 1971), Surinam (Brennan and Lukoschus 1971) and Venezuela (Brennan and Reed 1974) indicating perhaps its distribution includes the neighboring countries.
Although E. tinami has been reported from several countries, the two limited redescriptions (Oudemans 1912;Fuller 1952), more than 50 years ago, did not provide enough morphological detail to identify this species. In this study, we provide new figures, SEM images and additional metric data to help identify this species.
The human bite symptoms reported here are similar to those reported by Chaccour (2005) and Faccini et al. (2017). The under reporting of trombiculiasis in Brazil is probably due to the difficulty of finding chiggers on a human host or identifying them when they are found. Fonseca (1932) suggested chiggers may vector pathogens in Brazil. Surveys of Brazilian and South America chiggers their hosts and host symptoms are needed to help understand the potential health risks chiggers may present to humans and domestic animals. recommendation or endorsement by the USDA; USDA is an equal opportunity provider and employer.

Authors' contribution
RB-S, FCJ and DMB-B writing and development of the entire manuscript. AP and GFSRF collected material and aided in reporting on the case report of trombiculiasis, providing crucial information for this record. CL, AF, LM-L and EH-Z collected the recent material, with them it was possible to make the SEM images. In addition, identified all the hosts, of the recent collections as of the old collections. CW and RO contributed to the organization and improved the English and provided valuable insights from their experiences for this manuscript.