Host – Parasite relationships and co-infection of nasal mites of Chrysomus ruficapillus ( Passeriformes : Icteridae ) in southern Brazil

One hundred twenty-two Chrysomus ruficapillus were examined in southern Brazil, in order to research the presence of nasal mites and the parasite-host relationships. Nasal mite infections were analyzed for: presence of Ereynetidae and Rhinonyssidae considering the total number of hosts examined; Sexual maturity of males (juveniles and adults); Periods of bird collection and presence of co-infections. Were identified five taxa, four belongs to Rhinonyssidae (Sternostoma strandtmanni, Ptilonyssus sairae, P. icteridius and Ptilonyssus sp.) and one to Ereynetidae (Boydaia agelaii). Adult males were parasitized for one taxa more than juvenile males. Co-infections occurred in 22 hosts, between two, three and four taxa, belonging to Ereynetidae and Rhinonyssidae.The co-infections were more prevalent in austral autumn / winter. The host-parasite relations and co-infections by nasal mites in C. ruficapillus were reported for the first time, contributing to the knowledge about nasal mites in Brazil.

Rhinonyssidae and Ereynetidae are parasites that inhabit the respiratory system of birds, besides being bloodsucking and consumers of tissue, respectively.Ereynetidae species are located in the innermost portion of the nasal cavity (drier environment) and are very agile because of the presence of setae in the body (Hyland, 1979).Species of Rhinonyssidae are found embedded in the secretions of the cavity (higher humidity), they move slowly in the mucous membranes and cavities (Furman, 1957).
In addition, Rhinonyssidae is considered the most diverse taxon, distributed in eight genera.Species vary in its degree of host specificity, and, many are restricted to a single family of birds and others occur in hosts of different orders (Pence, 1973a;1975;Skoracki et al., 2012).
Ereynetidae apparently are little pathogenic, as well as Rhinonyssidae, when in low intensities of infection (Knee & Proctor, 2010).About the biology and mode of transmission of nasal mites there is not much information in the literature, Brooks & Strandtmann (1960) suggested that the transmission of Rhinonyssidae occurs quickly in the moment of feeding the juvenile birds or during the cohort when the two birds are closely associated, which would hinder the interspecific transmission.
Chrysomus ruficapillus (Vieillot, 1819) occurs in French Guiana, Brazil, Bolivia, Paraguay, Argentina and Uruguay (Narosky & Yzurieta 2003;IUCN, 2016).It is a swamp species of Brazilian Pampa with gregarious habit and can be found in flocks ranging from a few birds until thousands, and is considered one of the most abundant birds of Rio Grande do Sul state (Belton, 1994), being and closely linked to rice cultivation (Oryza spp.) (Silva, 2004).
The study of host-parasite relationships is essential to assist and understand the biology of both groups in these interactions.In this context, the parasitological indexes of the infections by Ereynetidae and Rhinonyssidae of C. ruficapillus in southern of Brazil are compared according to the periods of collect of hosts, the sexual maturity of the males, and the occurrence of co-infections.

Collection of hosts.
One hundred twenty-two hosts (20 females, 102 males: 46 adults and 56 juveniles) of Brazilian Pampa were examined from the municipality of Rio Grande, state of Rio Grande do Sul, Brazil (32°14'S; 52°29'W).The capture was performed in a farm (rice plantation) in "Granjas 4 Irmãos S. A.", where the trap (one cube with sized 2.5 m 3 with metal edges, covered with screen and top opening, which allows the entry of birds but not their exit) was installed containing potable water and bird food ad libitum.The samples were collected in the months of December 2013, January, February, May, June and July 2014 (were collect 20 birds in each month and other two were added in the last sample).
Collecting, preparing and identification of nasal mites.For mites collection, a cut was made in one nostril reaching (on the same side) to the external orifice of the ear, and then repeating the process on the opposite side.In order to form a right angle to the inferior portion, the turbinates were sectioned lengthwise, and then returned back to the top of the head (Fain, 1956).Later on, the cavity was washed with water jet in a sieve opened mesh (150 μm).The resulting content, the cavity and the respiratory tract were examined in stereomicroscope (Olympus ® SZ 61).Mites were preserved in alcohol 70%, mounted between slides and coverslip with Hoyer's, photographed under an Olympus ® BX 41 microscope with an attached camera system.Morphological identification was performed according to the dichotomous key of Pence (1975).Vouchers were deposited in the "Coleção de Artrópodes do Laboratório de Parasitologia de Animais Silvestres" -CALAPASIL/UFPel (478 at 488 and 522 at 525) Departamento de Microbiologia e Parasitologia, Instituto de Biologia, UFPel.
Parasitological analyzes.The term "assembly" was used in this study according to the concept of Fauth et al. (1996), because it represents the universe of species (taxonomic limits) and limits of distribution (geographic) according to the objectives of the study.This differs from the classic non-operational concept of community.
The assembly of nasal mites C. ruficapillus was analyzed using the following parameters: prevalence (P%), mean abundance of infection (MA), and mean intensity of infection (MII), according to Bush et al. (1997) and range of infection (R) according to Bush et al. (2001).Statistical analysis were performed using the "Quantitative Parasitology 3.0 Version 2.0" program (Rózsa et al., 2000), for comparisons between the P% (p <0.05), using the Chisquare test (X²) and MI confidence interval for the "bootstrap" (BCα p <0.05).
The infections by nasal mites were analyzed as: (a) the presence of Ereynetidae (E) and Rhinonyssidae (R) mites, when considering the total hosts examined (n=122) to assess whether there are differences in the infections between the two groups of mites.Similarly, infections were compared only between species Rhinonyssidae and the total sample of host; (b) maturity sexual of males: juvenile males (JM) (n=56) and adult males (AM) (n=46), in order to check if there is any difference between infections nasal mites (E+R), nasal mites Ereynetidae (E) and Rhinonyssidae mites (R).The females were collected in minor number (n = 20 birds) and have not been defined as the stage of development (adult or juvenile).Therefore, it was excluded for this analysis; (c) the collect periods: Collection period-I (CP-I, n=60 birds): December, January and February = summer in the southern hemisphere; Collection period-II (CP-II, n=62 birds): May, June and July = autumn / winter in the southern hemisphere.With the aim of cheking for differences in infections nasal mites (E+R) between periods; (d) the presence of co-infections (one host parasitized by at least two species of nasal mites) being a species of Ereynetidae and Rhinonyssidae (ExR) or species Rhinonyssidae (RxR) considering the total hosts (n = 122).In this context, it analyzed the P% of co-infections to check for differences between the sampling periods (CP-I and CP-II).
The parasitological indexes P%, MA, MII and R, the total number of infected birds and host's gender are presented in Tab.I.
Boydaia agelaii was the nasal mite with the highest values of prevalence and abundance of infection (P%=47.5;MA=1.8) (Tab.I).While the highest value of intensity of infection was from S. strandtmanni (MII=5.5)and the range was from P. icteridius (R=1-21) (Tab.I).Ereynetidae even represented by only one species, had the highest value of prevalence (P%=47.5)(p<0.05) when compared with Rhinonyssidae (Tab.II).Comparisons of P% and MII between the taxa of Rhinonyssidae did not show differences (Tab.II).Boydaia agelaii, S. strandtmanni, P. sairae and P. icteridius were found in C. ruficapillus female, and males: adult and juveniles, however, Ptilonyssus sp.occurred only in male adults (Tab.I).The hosts male adults were parasitized by five taxa, while male juveniles by four (Tab.I).However, have not difference statistic (interfamily) in relation to P% and MII of nasal mites between hosts adults and juveniles (Tab.III).
Regarding periods of host collection, the prevalence of nasal mites (E+R) was higher (p<0.05) in CP-II (n=62) (P%=72.6),when compared to CP-I (n=60) which was equal to P%= 50.There was no significant difference in the mean intensity of infection of mites, in CP-I (MII=4.3)and in CP-II (MII=5.9).
Studies relating differences in the assembly composition of nasal mites, and on the development stage of the birds were approached by Porter & Strandtmann (1952), Terbush (1963) and Amerson (1967), without statistical tests.
Co-infections with nasal mites apparently occur at low prevalence rates, according to Spicer (1987), Butenko & Stanyikovich (1999) and Knee et al. (2008).However, the authors examined a great diversity of hosts (orders / families / bird species) and low sample numbers of the same species.Therefore, the sample number should be considered as an important factor in future studies aimed at evaluating this relationship, either between species of Rhinonyssidae, or between species of Rhinonyssidae and Ereynetidae that parasitize Passeriformes, and probably other groups of birds.In this sense, the co-infections observed in C. ruficapillus (P% = 18.03), reinforce that the sample number (same host species) may be an important factor in the results with nasal mites.It should also be pointed out that aspects related to biology of bird, and also to biology of the species of mites should be considered.
In relation to the co-infections in the collection periods, the highest prevalence found in the collection period-II (P%=81,8) (18/22 occurrences), may be related to the behavior of the bird, because this period corresponds to winter in the southern hemisphere, characterized by low temperatures 10-25° (average of the last 30 years) (Fritzsons et al., 2015).This fact causes birds to pool up in the vegetation near to the field and road, which may facilitate contact between hosts, favoring so the transmission of mites.However, little is known about the biology and transmission of these species of mites and reproductive factors of mites should be studied.Therefore, additional studies on the behavior of C. ruficapillus should be conducted to aid in the understanding of parasitehost relationships and to evaluate possible forms of mite transmission among hosts.
In the study of host-parasite relationships, it is essential to consider the different taxonomic groups of birds, the peculiarities of behavior and evolutionary history, in addition to different geographical regions involved, both for the taxa of mites as of the hosts.Spicer (1987) comments that these factors are important and therefore may influence the prevalence of nasal mites.Thus, considering such factors, comparisons should be made with caution.
Boydaia agelaii was the only Ereynetidae found parasitizing C. ruficapillus.Cases of co-infections between Ereynetidae and Rhinonyssidae taxa have been reported.Adult males were parasitized for a higher rate than juvenile males.Co-infections by nasal mites were more prevalent in the collection period-II (austral autumn /winter in southern hemisphere).The most prevalent co-infection was between B. agelaii (Ereynetidae) and Ptilonyssus sairae (Rhinonyssidae).And the maximum number of taxa co-infecting C. ruficapillus was four species: B. agelaii, P. sairae, P. icteridius and S. strandtmanni.
The relationship of parasite-host, and co-infection by nasal mites in Chrysomus ruficapillus were reported for the first time, contributing to the knowledge parasitological of the host and enlarge the information about nasal mites in Brazil.