Print version ISSN 1519-566X
Neotrop. Entomol. vol.32 no.2 Londrina Apr./June 2003
SYSTEMATICS, MORPHOLOGY AND PHYSIOLOGY
Ixodid ticks (Acari: Ixodidae) present at Parque Nacional El Rey, Argentina
Carrapatos (Acari: Ixodidae) do Parque Nacional El Rey, Argentina
Pablo M. BeldomenicoI; Cecilia J. BaldiI; Leandro R. AntoniazziI; Guillermina M. OrdunaI; Mariano MastropaoloI; Ana C. MacedoI; Marcelo F. RuizI; Viviana M. OrcelletI; José L. PeraltaI; José M. VenzalII; Atilio J. MangoldIII; Alberto A. GuglielmoneIII
IFacultad de Ciencias Veterinarias,Universidad Nacional del Litoral, P. Kreder 2805 (3080) Esperanza, Santa Fe, Argentina
IIDepto. Parasitología Veterinaria, Facultad de Veterinaria, Alberto Lasplaces 1550, (11600) Montevideo, Uruguay
IIIINTA, EEA, CC22 (2300) Rafaela, Santa Fe, Argentina
Information on autochthonous ticks and their hosts is scarce in South America, especially in Argentina. To contribute to tick knowledge in the region, 2094 ticks were collected from the vegetation, humans, domestic and wild animals at a host-and-tick rich area of northern Argentina during six field trips conducted in 1999 (January and August), 2000 (March and November), and 2001 (March and June). The ticks were identified as Amblyomma cajennense (Fabricius), Amblyomma coelebs Neumann, Amblyomma sp., Haemaphysalis juxtakochi Cooley, H. leporispalustris (Packard), Ixodes pararicinus Keirans & Clifford, I. loricatus Neumann, I. longiscutatum Boero and Ixodes sp. Small mammals were mainly parasitized by immature stages of Ixodes; humans and domestic animals, predominantly by Amblyomma spp., and birds, mainly by nymphs and larvae of Haemaphysalis spp.
Key words: Amblyomma, Ixodes, Haemaphysalis
Informações sobre carrapatos autóctones e seus hospedeiros são escassas na América do Sul, especialmente para a Argentina. Com o objetivo de contribuir para o conhecimento dos carrapatos na região, 2094 carrapatos foram coletados da vegetação, de humanos e de animais domésticos e selvagens numa área no norte da Argentina rica em carrapatos e hospedeiros, durante seis viagens de campo conduzidas em 1999 (janeiro e agosto), 2000 (março e novembro) e 2001 (março e junho). Os carrapatos foram identificados como Amblyomma cajennense (Fabricius), A. coelebs Neumann, Amblyomma sp., Haemaphysalis juxtakochi Cooley, H. leporispalustris (Packard), Ixodes pararicinus Keirans & Clifford, I. loricatus Neumann, I. longiscutatum Boero e Ixodes sp. Pequenos mamíferos foram principalmente parasitados por estágios imaturos de Ixodes; humanos e animais domésticos, predominantemente por Amblyomma spp., e pássaros, principalmente por ninfas e larvas de Haemaphysalis spp.
Palavras-chave: Amblyomma, Ixodes, Haemaphysalis
Ticks (Acari: Ixodoidea) are highly specialized blood-feeding arthropods that parasitize vertebrates and may act as biological vectors for many pathogens of man and animals (Balashov 1972). Most information presently available on Argentinean ticks arises from findings from domestic animals. Around forty tick species are reported for Argentina, with the greatest diversity and abundance in the subtropical northern part of the country (Boero 1957, Guglielmone & Viñabal 1994). Thirty-four of these species belong to the family Ixodidae, and are represented by the genera Amblyomma (22 species), Ixodes (7 species), Haemaphysalis (2 species), Anocentor (1 species), Boophilus (1 species), and Rhipicephalus (presumably 1 species) (Boero 1957, Mangold et al. 1983, Keirans et al. 1985). The last two genera, represented by single species each, are the cattle tick (Boophilus microplus [Canestirini]) and the dog brown tick (Rhipicephalus sanguineus [Latreille]), both introduced to the continent along with their hosts. The rest consist of autochthonous species that, with variable distribution ranges, belong to the Neotropical zoogeographic region. Host-specificity is variable among these ticks, but some tick species adapted well to feed on man and/or his domestic animals, parasitizing them while in some stages, like Amblyomma neumanni Ribaga, Amblyomma cajennense (Fabricius) and Ixodes pararicinus Keirans & Clifford (Keirans et al. 1985; Guglielmone et al. 1990, 1991).
The objective of the present study was to identify the tick species present at the host-and-tick rich Parque Nacional El Rey, Anta Department, Salta Province, as well as the hosts they were feeding on.
Materials and Methods
The Parque Nacional El Rey (24º 15' S 64º 40' W) is a 44,162-ha reserve located in the northwestern Argentina. This park consists of environmental settings of Chaco and Cloudforest biomes, with altitudes ranging from 600 m to 2300 m. The climate is subtropical and most of the 1500 mm annual rainfall occurs in spring and summer.
Ticks were collected from humans, domestic and wild animals, and from the vegetation (using the dragging technique with pieces of white flannel as described by Sonenshine et al. , or by hand collection) in six 13-day field trips conducted in 1999 (January and August), 2000 (March and November), and 2001 (March and June). Small mammals and birds (the latter were individuals that accidentally fell in the traps) were captured in the last three field trips, with official permission of Administración de Parques Nacionales. For such collection, Tomahawk (1620 trap-days total) and Sherman (2160 trap-days total) traps were evenly placed at three environmental settings of the park (mountainous Chaco, transitional forest and mountain forests [the last belongs to the Cloudforest]). Table 1 shows the number and species of wild animals examined. Park personnel contributed with tick collection during the inter-trip periods. Mouse genus and species identification were conducted by one of the authors (PMB) and confirmed by Carlos Galliari (Universidad Nacional de La Plata). Birds were identified using the descriptions provided by de la Peña & Rumboldt (1998).
Ticks were identified following the keys provided by Clifford et al. (1961), Guglielmone & Viñabal (1994), Jones et al. (1972) and Kohls (1960). The description by Kohls & Clifford (1967) for Ixodes longiscutatum Boero (named as Ixodes [Haemixodes] uruguayensis Kohls & Clifford) was also used. Larvae and nymphs of Ixodes pararicinus Keirans & Clifford and Ixodes loricatus Neumann were identified and confirmed by comparing with material obtained at the laboratory from adults collected by one of the authors (JMV). Ticks were stored at the Universidad Nacional del Litoral Ixodoidea Collection (accession numbers SAER001-SAER200).
Results and Discussion
A total of 2094 ticks belonging to eight species were collected. Table 2 shows numbers and sources of the tick species collected.
Parasitism. Six hundred and sixty six ticks were collected from humans at the following proportions: 69.2% Amblyomma sp. larvae; 19.5% Amblyomma sp. nymphs; 9.3% A. cajennense adults; 1.7% Amblyomma coelebs Neumann adults; 0.33% Haemaphysalis juxtakochi Cooley nymphs. Only 19 ticks (2.9%) were attached: Amblyomma sp. (10 nymphs and 2 larvae), A. cajennense (5 adult females), A. coelebs (1 adult female) and H. juxtakochi (1 nymph).
Two hundred and three sigmodontin mice of the genera Akodon, Calomys, Oligoryzomys, Oryzomys, and Oxymycterus, in order of abundance, were captured. Not all of them could be identified to the species level, but the majority identified were Akodon simulator Thomas, A. spegazzini Thomas, Calomys venustus Thomas, Oligoryzomys chacoensis Myers & Carlenton, Oryzomys legatus Thomas, Oxymycterus paramensis Thomas. A total of 226 ticks were found on 28.1% of those hosts. All ticks found on mice were immatures. The species I. pararicinus was the dominant one, present in 91.2% of the parasitized mice. Less frequent were I. loricatus (17 larvae and 1 nymph) and I. longiscutatum (3 larvae on 1 Akodon sp.). Nine unfed larvae of Amblyomma sp. were found on one mouse.
A total of 486 ticks were collected from 20 horses present at the park. Males and females of A. cajennense were the dominant ticks on horses, accounting for 69.4% of the findings. They were found year-round, more abundantly in spring and summer. Two females of A. coelebs were found on horses. Amblyomma sp. nymphs (9.2%) were found year round, and larvae (6.4%) were only present in fall (22 larvae) and winter (9 larvae). The species H. juxtakochi was the second most frequent tick species on horses (14.4%). Adults of H. juxtakochi were present in every season, but were more abundant in fall (25 females and 9 males), and least frequently found in summer (2 adults or less per sampling trip). Five nymphs of this species were found in winter, spring and summer. Larvae were not found. One male of I. pararicinus was found in March 2001.
Eighty ticks were recovered from the three dogs present at the park. The majority (96.3%) corresponded to immature stages of Amblyomma (56 larvae and 21 nymphs). Two males of A. cajennense and a single male of H. juxtakochi were also collected.
Individuals belonging to two bird species were found harboring ticks. Ticks were collected in June, in mountainous Chaco, where the majority (87.5%) of the birds were captured. All ixodids found on them were immatures. Ten out of 13 plush-crested jay (Cyanocorax chrysops [Vieillot]) (Passeriformes: Corvidae) were found infested with Amblyomma sp. (2 nymphs and 8 larvae), H. juxtakochi (3 nymphs and 21 larvae), Haemaphysalis leporispalustris (Packard) (1 larvae), I. pararicinus (2 larvae), and Ixodes sp. (15 larvae). The single captured saffron-billed sparrow (Arremon flavirostris Swainson) (Passeriformes: Emberizidae) had H. leporispalustris (17 engorged larvae), H. juxtakochi (1 larvae) and Ixodes sp. (1 larvae).
Four cavies (Cavia tschudii Fitzinger [Rodentia: Caviidae]) were captured in mountainous Chaco during spring. The only tick species found on three of them was I. longiscutatum (2 females, 1 nymph, 9 larvae).
Three opossums (Didephimorphia: Didelphidae), two Thylamys venusta (Thomas) and one Lutreolina crassicaudatta (Desmarest), were examined for ticks. One larva of I. pararicinus on a T. venusta was the only finding.
The species A. cajennense (2 females and 1 male), Amblyomma sp. (19 nymphs), and I. pararicinus (2 females) were found on two sacrificed feral bovines.
Questing Stages. A total of 528 ticks were collected from vegetation. Most specimens (99%) were found in forested areas. A small proportion (1%) of Amblyomma sp. nymphs and A. cajennense adults were found in open areas. Amblyomma was the genus most frequently collected (98.4%). Other species found were H. juxtakochi (2 females, 2 males, 8 nymphs and 2 larvae) and I. pararicinus (2 females and 1 male).
The genus most commonly found in humans and domestic animals was Amblyomma. This correlates with other studies in the region (Guglielmone et al. 1990, 1991). Only a small proportion of the ticks found on humans were attached. However, this proportion may be underestimated, because most of the non-attached ticks were Amblyomma spp. that could have bitten humans if they were left on, but were removed as soon as noticed to prevent tick borne diseases. Nymphs and larvae of Amblyomma were not identified to species level, because currently there is no key to immature Ammblyomma of the Neotropical region, but we assumed that they were either A. cajennense or A. coelebs, on the basis of not finding any other adult Amblyomma species, and also because only two types of different Amblyomma nymphs were identified. Rodents did not appear to be important in the maintenance of A. cajennense and A. coelebs at the park. Instead, larvae and nymphs of Amblyomma seemed to prefer larger mammals and birds. Very little is known about the biology of Amblyomma coelebs, but the adult stage is commonly found on Tapirus terrestris (L.) (Peryssodactyla: Tapiridae), of which large populations are found in the study area (Heinonen & Chebez 1997). Fifty-two of the 65 adults of A. coelebs collected were questing. They were found in every season, but more frequently in summer (mean 2 ticks/day), remaining lower the rest of the year (mean 0.4 ticks/day). The rest were found on horses (2 female ticks) and humans (11 specimens, 1 female attached). This constitutes the first record of this species with confirmation of attachment to a human, and the first record on horses in Argentina.
Adults of H. juxtakochi are known to prefer cervid hosts and they adapt well to cattle (Boero 1957, Kohls 1960), but they where mostly found on horses. Birds appeared to be important hosts for immature stages of H. juxtakochi, particularly for larvae.
The species H. leporispalustris was last reported in Argentina in 1954 (Boero 1954). This species' preferred hosts are lagomorphs of the genus Silvilagus (Lagomorpha: Leporidae) (Kohls 1960). Parque Nacional El Rey hosts populations of Silvilagus brasiliensis (L.) (Chebez & Heinonen 1997), but no rabbit was available for tick examination. Larvae of H. leporispalustris were only found on birds, 17 on A. flavirostris, and 1 on C. chrysops. It is noteworthy that the H. juxtakochi : H. leporispalustris ratio was 24:1 for C. chrysops and 1:17 for A. flavirostris.
Horses did not appear as important hosts for I. pararicinus, but mice seemed to be very important for their maintenance at the park, as larvae and nymphs of this species frequently parasitized them. A few larvae were also found on C. chrysops and T. venusta. Both questing females of this tick species responded very apprehensively to human proximity, retracting completely their limbs and remaining immobile, as opposed to what was seen for species of Amblyomma, which always showed a reaching out attitude whenever human skin was approached.
The species I. loricatus was absent on the three opossums captured, but their immature stages were found on mice.
Immature stages of I. longiscutatum were unknown until recently, when Venzal et al. (2001) found that the immatures described as I. uruguayensis were in fact I. longiscutatum. This species was found mainly on C. tschudii captured during spring in mountainous Chaco. These cavies were found to harbor every known stage of I. longiscutatum (2 females, 1 nymph, 9 larvae). Three larvae of this species were found on a mouse that was captured in the same area and time as the cavies, but the species was absent on the remaining 202 mice examined, suggesting that the occurrence of immature stages of this species on mice is associated with the concurrent presence of cavies in the area, from which that tick could occasionally move onto mice.
Sixteen larvae that resembled I. pararicinus, but with shorter palpi, were collected from birds; one such larva was found on a mouse.
Small mammals at the park appeared to harbor principally Ixodes spp., whereas domestic animals and humans were principally parasitized by Amblyomma spp. This might indicate that direct pathogen transmission from rodents to humans or domestic animals by a single tick species, as for Lyme disease, human granulocitic ehrlichiosis and babesiosis, transmitted by Ixodes scapularis Say, 1821 in the eastern United States (Chang et al. 1998, Kjemtrup & Conrad 2000), would be rather unusual in the park's ecosystems.
To the staff of Parque Nacional El Rey and Delegación Técnica Regional Noroeste de Administración de Parques Nacionales, for their collaboration. To Carlos Galliari (Universidad Nacional de La Plata) for the identification of mice genera and species.
This study was funded by the Field Veterinary Program of Wildlife Conservation Society and Universidad Nacional del Litoral.
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