Ticks on birds caught on the campus of the Federal Rural University of Rio de Janeiro , Brazil

The prevalence of parasitic infections, particularly those caused by ectoparasites, may influence the biology and ecology of wild birds. The aim of this study was to investigate occurrences and identify the species of ticks collected from wild birds caught on the campus of the Federal Rural University of Rio de Janeiro. The birds were caught using mist nets between October 2009 and December 2010. In total, 223 birds were caught, represented by 53 species and 19  families in nine orders. Nineteen birds (n  =  7 species) were parasitized by immature ticks (prevalence of 8.5%). Forty-four ticks were collected, of which 23 were nymphs and 21 were larvae. There were associations between parasitism by ticks and non-Passeriformes birds, and between parasitism and ground-dwelling birds, which was possibly due to the presence (or inclusion among the captured birds) of Vanellus chilensis (Charadriiformes: Charadriidae). All the nymphs collected were identified as Amblyomma cajennense. In general terms, we must emphasize that wild birds in the study area may play the role of dispersers for the immature stages of A. cajennense, albeit non-preferentially.


Introduction
Ectoparasitism occurs widely across the globe, affecting different groups of organisms at a variety of levels (CLAYTON et al., 2004).Among the organisms affected, birds are considered to be the hosts for various species including mites, ticks, lice and dipteran insects (CLAYTON;JOHNSON, 2003;LYRA-NEVES et al., 2003;CLAYTON et al., 2004;HIGGINS et al., 2005;STORNI et al., 2005).Ticks are vectors for many pathogenic agents, both for domestic and wild animals and for humans.Because of their low mobility, ticks depend on hosts for their dispersal (TOLESANO-PASCOLI et al., 2010).Many bird species have been reported to be their hosts, not only during the larval and nymph stages (BARROS-BATTESTI et al. 2006), but also during the adult stage (JORDAN et al., 2009;TOLESANO-PASCOLI et al., 2010;COSTA, 2011).
Few published papers have addressed parasitism of ticks on wild birds.The recent studies by Labruna et al. (2007), Ogrzewalska et al. (2009Ogrzewalska et al. ( , 2010) ) and Tolesano-Pascoli et al. (2010) in Brazil, as well as those carried out by Graham et al. (2010) and Jordan et al. (2009) can be highlighted.As stated by Ogrzewalska et al. (2009), studies on species of ticks carried by wild birds in different ecosystems may help towards understanding their dispersion as possible vectors for disease transmission.Thus, the objective of the present study was to identify the tick species that infested wild birds that are present on the campus of the Federal Rural University of Rio de Janeiro, in the municipality of Seropédica, state of Rio de Janeiro, in remnant fragments of the Atlantic Forest biome, which might provide complementary information for mapping the tick species that infest these animals.

Materials and Methods
The Federal Rural University of Rio de Janeiro (UFRRJ) (22° 48' 27" S and 43° 37' 17" W) is located in the municipality of Seropédica, state of Rio de Janeiro, at km 7 of the BR-465 highway, and covers an area of approximately 3,024 hectares.The region presents typical Atlantic Forest vegetation, with forest fragments, but a large proportion is characterized as presenting secondary vegetation with large areas of cleared fields and pasture as consequence of urbanization (FERREIRA et al., 2010) (Figure 1).
The birds used in the present study were caught on 10 mist nets of dimensions 12 × 2.5 m and mesh size of 36 × 36 mm, which were positioned linearly.Bird-catching was performed monthly between morning and twilight from October 2009 to December 2010.The birds were identified and classified in accordance with Sigrist (2007) and CBRO (2009).Ticks were removed manually and/or using tweezers and were taken to the laboratory in order to perform taxonomic identification procedures.After checking each bird's body and removing the ticks, the birds were released into the environment.The ticks collected during the nymph stage were identified by means of the dichotomous key of Martins et al. (2010), and then were stored in flasks containing alcohol (70GL).Some of the larvae that were collected were placed on domestic rabbits, as an experimental infestation, in order to complete the tick lifecycle, as described by Pinter et al. (2002).The larvae that were not fixed on domestic rabbits were put in a B.O.D. heated chamber at a temperature of 27 ± 1 °C and relative humidity of 80 ± 5% in order to allow ecdysis to occur.If they still did not complete their lifecycles, they were stored in flasks containing alcohol (70GL) and were identified at genus level by means of the identification key proposed by Clifford and Anastos (1960).
All samples were gathered with permission from IBAMA, in accordance with procedural no.16753-1/2009.The experimental infestations were performed with authorization from the Ethics Committee of UFRRJ under protocol no.010016/2010.The ticks collected in the present study will be deposited in the Tick Collection of the Butantan Institute (IBSP), São Paulo, state of São Paulo (curator: Dr. D. M. Barros-Battesti).

Statistical analysis
For the statistical analysis, the birds were grouped according to order (Passeriformes and Non-Passeriformes), habitat (canopy, undergrowth, field or ground-dwelling) and trophic guild (insectivorous, frugivorous, granivorous, necrophagous, nectarivorous or omnivorous).The chi-square (χ 2 ) test was used for the order variable, while Fisher's test was used for the habitat and trophic guild variables.Both tests were performed with a significance level of 5%.These tests were performed in order to ascertain whether the observed distribution of ectoparasitism frequencies diverged significantly from the expected frequencies, using the R statistical package (R DEVELOPMENT CORE TEAM, 2009).

Results
In total, 44 ticks (23 nymphs and 21 larvae) were collected from the 223 birds caught.All the nymphs collected were identified as Amblyomma cajennense (Fabricius, 1787).After ecdysis of three larvae (14%) to the nymph stage had occurred, these specimens were also identified as A. cajennense.The remaining 18 larvae (86%) were identified as Amblyomma spp.Out of the total number of birds, 19 specimens distributed in seven species were infested by ticks, which corresponded to a total prevalence of 8.5% and mean intensity of 1.0 tick per bird (Table 1).The Passeriformes order presented the highest number of infested species: Turdus amaurochalinus (n = 4), Sporophila leucoptera (n = 1), Volatinia jacarina (n = 1), Pitangus sulphuratus (n = 1) and Ramphocelus bresilius (n = 1).Columbiformes was the least representative order, with only 1 infested species, Columbina talpacoti (n = 1).Vanellus chilensis, which belongs to the Charadriiformes order, was the species with the greatest prevalence of parasitism, with 66% (n = 10 individuals).The analysis on associations with parasitism shown by the order (Passeriformes versus non-Passeriformes), and in relation to the habitat and the trophic guild, was performed using the chi-square test.The variables of the order (Passeriformes versus non-Passeriformes) and the habitat occupied by the bird (p = 0.001 and p = 0.0000008 for p < 0.05, respectively) presented associations, thus showing that the probability of infestation by ticks on birds was greater among non-Passeriformes birds and grounddwelling birds.For the variables of trophic guild and parasitism, no association was observed (p = 0.6731 for p > 0.05) (Table 2).

Discussion
Only nymph and larval stages were found on the birds on the UFRRJ campus.Both of these stages are commonly found infesting birds (BARROS-BATTESTI et al., 2006).The absence of adult ticks infesting birds was also mentioned by Labruna et al. (2007) and Ogrzewalska et al. (2009) after studying birds in Atlantic Forest areas in the state of São Paulo.
Vanellus chilensis was the bird species that presented the greatest number of infested individuals.This species is common on the UFRRJ campus, where they forage and nest on the ground (FERREIRA et al., 2010), and it is this ground-dwelling behavior that favors parasitism (ARZUA et al., 2003).Another important factor favoring this parasitism that should be mentioned is that this bird species lives in areas commonly frequented by horses and capybaras.
The species with the second greatest number of infested individuals was T. amaurochalinus, which some authors have reported in association with ticks (ARZUA et al., 2005;PEREZ et al., 2008).Larval and nymph parasitism in Turdus was reported in the states of Rio de Janeiro (STORNI et al., 2005) and Paraná (ARZUA, 2007).The presence of ticks among this group of birds is related to their foraging habit, which consists of hopping and turning leaves, often making holes in the ground with their beaks in searching for food (STORNI et al. 2005;WALDENSTRÖM et al., 2007).
The geographical distribution of the parasites coincided with the geographical distribution of the host fauna (KLOMPEN et al., 1996).Thus, the presence of A. cajennense on birds may be associated with the high degree of anthropization of the area, as well as the presence of horses and capybaras.The predominance of this ixodid on the campus is also corroborated by Silveira (2010), who correlated greater occurrence of A. cajennense on the UFRRJ campus with environments with high levels of anthropic activities and the presence of horses and capybaras.Previous reports also correlated the high degree of anthropization with the presence of this ixodid (LABRUNA et al., 2001;SZABÓ et al. 2009) because this species is less sensitive to changes in the ecological structure of the area, which relates mainly to the availability of wild hosts (CANÇADO et al., 2008).Rojas et al. (1999) also reported that A. cajennense was the dominant ixodid in captures performed in special protection areas in the cerrado (savanna-like terrain).However, comparisons between the results reported in their study and the results from the present study should be made carefully, since not only do the two areas present completely different phytophysiognomies, but also the methodology used by those authors for identifying ticks needs to be reviewed (LABRUNA et al., 2007).Other studies carried out in the cerrado have also reported low prevalence of immature stages of A. cajennense and greater occurrence of Amblyomma longirostre and Amblyomma nodosum (TOLESANO-PASCOLI et al., 2010).
A. cajennense is considered to be a generalist concerning host species, especially during the larval and nymph stages, since during these immature stages it does not have sufficient energy to use in searching for an ideal host, in comparison with adult ticks (RANDOLPH, 2004).Thus, they can use birds not only for feeding but also for dispersal.Considering that, in the area studied, there is frequent activity of horses and capybaras, which are preferred hosts of this ixodid, the possibility of occurrence of A. cajennense in other host species is reduced.This can be correlated with the low mean intensity of ticks associated with the birds found in the present study, which was close to the intensities reported by Ogrzewalska et al. (2009) from studying birds in the Atlantic Forest, and Tolesano-Pascoli et al. (2010) among birds in the cerrado.Their studies indicated that these birds could be used as alternative hosts for the immature stages of this species.
The statistical analysis showed that birds that live on the ground, especially non-Passeriformes birds, were more prone to parasitism by ticks in the area studied.This association was probably due to the presence (or inclusion among the birds caught) of V. chilensis.It should be highlighted that in most inventories involving parasitism among wild birds, there are reports of greater, and sometimes exclusive, parasitism of the order Passeriformes in areas with typical cerrado vegetation (PASCOAL, 2009;TOLESANO-PASCOLI et al., 2010) and typical areas of Atlantic Forest (LABRUNA et al., 2007;OGRZEWALSKA et al., 2009OGRZEWALSKA et al., , 2010)).This order has also been considered to be important for maintaining the lifecycle of ticks such as A. nodosum, playing the role of host for their immature stages (OGRZEWALSKA et al., 2009).However, none of the surveys involving non-Passeriformes birds have reported captures of V. chilensis.The result from the analysis between different trophic guilds corroborated the results of Marini et al. (1996), who reported a weak association between parasitism and trophic guilds.Thus, it can be concluded that despite the low number of birds infested by A. cajennense, it is possible that the local avifauna plays an important role in the lifecycle of this ixodid, even in the presence of preferred hosts, such as horses and capybaras.In general terms, the fact that wild birds in the area studied may play the role of dispersers for immature stages of A. cajennense, even though not preferentially, should be highlighted.

Figure 1 .
Figure 1.Location of the study area.Federal Rural University of Rio de Janeiro, Seropédica -RJ.

Table 1 .
List of bird species captured in UFRRJ between October 2009 and December 2010, with their classification (order, family, trophic guild and habit), and the number (N) of infested birds in relation to the number (N) of birds caught.Indicative values of prevalence of infestation (PI) and mean infestation intensity (MII).

Table 2 .
Number of individuals (% infested) caught at UFRRJ between October 2009 and December 2010, in relation to the variable of order, habitat and trophic guild.Note: Lower-case letters represent significance of association by means of the chi-square test (χ 2 ) for the order variable and by means of Fisher's test for the habitat and trophic guild variables, with 5% significance level.