Evelina L. Tarragona

Divergent environmental preferences and areas of sympatry of tick species in the Amblyomma cajennense complex (Ixodidae)

Four species of Neotropical ticks, Amblyomma mixtum, Amblyomma cajennense, Amblyomma tonelliae and Amblyomma sculptum (formerly included in the catch-all name A. cajennense), have an allopatric distribution in much of their range, with areas of parapatry for at least two of them. We inferred the abiotic niches of these organisms using coefficients of a harmonic regression of the temperature and the Normalized Difference Vegetation Index (NDVI, reflecting plant stress) from remotely sensed data from MODIS satellites with 0.05° spatial resolution. Combinations of coefficients describing the phenology of these two variables pointed to divergent niche preferences, compatible with previous events of vicariance among the species. Amblyomma cajennense has been recorded in areas with small variations in temperature and NDVI. The remaining species were recorded in areas with large variations. The maximum environmental niche overlap was ∼73.6% between A. mixtum and A. cajennense and 73.5% between A. tonelliae and A. sculptum. Projecting these inferences on the geographical space revealed probable areas of sympatry or parapatry between A. mixtum and A. cajennense or between A. tonelliae and A. sculptum, the latter of which was confirmed with field collections. The A. sculptum distribution overlaps with that of A. tonelliae in northern Argentina and Paraguay; parapatry occurs at one extreme of the conditions occupied by both species. Compared with areas of allopatry, sites with both species had consistently lower temperatures, except for 10-12weeks during the summer, and higher NDVI values throughout the year. We hypothesise that the overlap between A. tonelliae and A. sculptum resulted from secondary contact between populations, with A. sculptum adapting to sites with high water availability to balance high summer temperatures. Additional surveys of the areas of spatial overlap among these species are necessary to elucidate the forces driving their evolution and their adaptation to the environment.

Infection with Ehrlichia canis and Anaplasma platys (Rickettsiales: Anaplasmataceae) in two lineages of Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) from Argentina.

Natural infection with Ehrlichia canis and Anaplasma platys in ticks belonging to the tropical and temperate lineages of Rhipicephalus sanguineus sensu lato from Argentina was evaluated. Samples were tested for Ehrlichia canis infection by PCR assays using 16S rRNA, dsb and p28 gene, while detection of A. platys was performed with 16S rRNA and groESL gene. The assignment of the ticks to each lineage was corroborated with 16S rDNA sequences. All ticks infected with E. canis and A. platys belonged to the tropical lineage. These results constitute the first record of E. canis infection in R. sanguineus s.l ticks from Argentina. No ticks from the temperate lineage were found to be infected with E. canis, coinciding with previous studies performed in Argentina and Uruguay where E. canis infection was not detected in R. sanguineus s.l from the temperate lineage. Because the presence of the tropical lineage of R. sanguineus s.l has been documented in tropical areas of northern Argentina between 22° and 24° of south latitude, the findings of this work indicate that transmission of E. canis and A. platys to dogs by R. sanguineus s.l probably occurs along this region.

Bacteria of the genera Ehrlichia and Rickettsia in ticks of the family Ixodidae with medical importance in Argentina

The aim of this study was to get an overview about the occurrence of bacteria from the genus Ehrlichia and Rickettsia in ixodid ticks with medical importance in Argentina. Therefore, in 2013 and 2014, free-living ticks were collected in different provinces of northern Argentina. These ticks were determined as Amblyomma sculptum, Amblyomma neumanni, Amblyomma parvum, Amblyomma triste, Amblyomma ovale, Amblyomma tonelliae and Haemaphysalis juxtakochi. All samples were tested to determine the infection with Ehrlichia spp. and Rickettsia spp. by PCR assays. Rickettsial DNA was detected in all tested tick species, with the exception of A. tonelliae. ‘Candidatus Rickettsia amblyommii’, ‘Candidatus Rickettsia andeanae’, and Rickettsia parkeri were found in A. neumanni, A. parvum, and A. triste, respectively. Another rickettsial species, Rickettsia bellii, was found in A. sculptum, A. ovale and H. juxtakochi. None of the tested ticks showed infection with Ehrlichia. The results of the study demonstrate that Rickettsia species belonging to the spotted fever group are associated with various species of Amblyomma throughout a wide area of northern Argentina, where cases of Amblyomma ticks biting humans are common.

Ticks (Acari: Ixodidae) of northern Misiones Province, Argentina

Abstract Information on distribution and hosts of hard ticks of northern Misiones Province in Argentina is presented in this study. Ticks were identified by morphological characters and by sequences of a 410 bp fragment of the mitochondrial 16S rRNA gene. A total of 292 ticks collected from the environment and wild and domestic mammals were identified: Amblyomma coelebs, A. brasiliense, A. dubitatum, A. incisum, A. ovale, Haemaphysalis juxtakochi and Rhipicephalus microplus. The presence of A. coelebs was confirmed for Argentina and the first record of H. juxtakochi in Misiones was presented. Some of the species as A. incisum, A. ovale and R. microplus are ticks of medical and veterinary importance. Therefore, further studies on the vectorial role of these species in Misiones Province are necessary to determine their epidemiological relevance.

Ticks infesting cattle and humans in the Yungas Biogeographic Province of Argentina, with notes on the presence of tick-borne bacteria

This study was performed to determine the tick species that infest cattle and humans throughout an altitudinal gradient in the Yungas Biogeographic Province of Argentina. The presence of tick-borne bacteria of the genera Rickettsia, Ehrlichia and Borrelia in the collected ticks was also evaluated. Samples of ticks parasitizing cattle and humans were carried out in different seasons. Questing ticks (adults and nymphs) were collected from vegetation and analyzed to detect the presence of Rickettsia, Ehrlichia and Borrelia by a battery of different PCRs. Five species of hard ticks were found parasitizing cattle: Amblyomma sculptum, Amblyomma tonelliae, Amblyomma hadanii, Haemaphysalis juxtakochi and Ixodes pararicinus. Amblyomma sculptum (immature and adults), A. tonelliae (immature and adults), A. hadanii (larvae) and one nymph of I. pararicinus were found attached to humans. Rickettsia amblyommatis was detected in one nymph of A. hadanii. DNA of a Borrelia genospecies belonging to the B. burgdorferi s.l. complex (phylogenetically related to haplotypes previously reported in Ixodes aragaoi from Uruguay and I. pararicinus from Argentina) was detected in adults of I. pararicinus. Amblyomma sculptum and I. pararicinus appear to be the tick species more frequent on cattle in the YBP from Argentina, and A. sculptum and A. tonelliae, were the main ticks found attached to humans. The medical importance of the bacteria of the genus Rickettsia and Borrelia detected in this work remains unknown.

Liolaemus lizards (Squamata: Liolaemidae) as hosts for the nymph of Amblyomma parvitarsum (Acari: Ixodidae), with notes on Rickettsia infection

Adults of Amblyomma parvitarsum are common ectoparasites of South American camelids of the genera Lama and Vicugna, occuring in highlands of Argentina, Bolivia, Chile, Peru and also in Argentinean Patagonia. Whereas larval stages of this tick are known to feed on small lizards, host records for the nymphal instar have remained unreported. Supported by morphological and molecular analyses, herein we report A. parvitarsum nymphs parasitizing two Liolaemus species (Reptilia: Squamata) in the Andean Plateau of Argentina and Chile. Additionally, by a PCR screening targetting gltA and ompA genes, DNA of Rickettsia was detected in one of the collected nymphs. Obtained sequences of this agent were identical to a recent Rickettsia sp. described infecting adults of this tick species in Chile and Argentina.

Ticks (Acari: Ixodidae) of Nepal: First record of Amblyomma varanense (Supino), with an update of species list

Males and females specimens of Amblyomma were collected from Orthriophis hodgsoni (Squamata: Colubridae) caught during routine herpetological work in Kathmandu. Morphological characteristics led to the diagnosis of A. varanense, constituting the second Nepalese species for the genus after the collection of Amblyomma gervaisi, also from a colubrid snake, almost 100 years ago. Amblyomma varanense is the 55th species found in the country, and preceded for the collection of 21 species of Haemaphysalis, 14 Ixodes, 6 Rhipicephalus, 6 Hyalomma, 4 Dermacentor, 1 Amblyomma, 1 Anomalohimalaya and 1 species of Nosomma. Eleven and 19 species have been found on humans and domestic mammals, respectively, evidencing the medical and economic importance of Nepalese Ixodidae.

Molecular detection of the human pathogen Rickettsia parkeri strain Atlantic rainforest in Amblyomma ovale ticks in Argentina

Human rickettsioses caused by Rickettsia parkeri strain Atlantic rainforest in Brazil motivated the analysis of Amblyomma ovale ticks in Misiones province, a similar ecological region in northeastern Argentina. During 2010-2017, 393 A. ovale ticks were collected from domestic and wild animals and from vegetation, and 177 were pooled for rickettsial detection by PCR targeting the gltA, ompA and ompB genes. A sample consisting of a pool of two A. ovale adults collected on Nasua nasua was positive for Rickettsia parkeri strain Atlantic rainforest. Since the Atlantic rainforest areas in Brazil share environmental characteristics with Misiones province, the transmission cycle of R. parkeri strain Atlantic rainforest observed in Brazil should be extrapolated to Argentina, where awareness on the possibility of occurrence of rickettsiosis cases caused by this strain should be raised.

Amblyomma yucumense Krawczak, Martins & Labruna, 2015 (Acari: Ixodidae) in Argentina

Amblyomma yucumense was recently described from specimens collected in the Turvo State Park, southern Brazil. In search of this tick species, free-living ticks were collected at the Mocona Provincial Park and the Yaboti Biosphere Reserve in Misiones province, Argentina. A total of 594 ticks were collected, of which 448 were Amblyomma brasiliense, 90 Amblyomma incisum , one Amblyomma ovale , 48 Haemaphysalis juxtakochi and seven A. yucumense. The latter was confirmed by the presence of certain morphological characters and the analysis of sequences of a 410-bp fragment of the mitochondrial 16S rDNA performed to representative specimens. The sequences showed 100% identity with that of A. yucumense from Turvo State Park in Brazil. Amblyomma yucumense , Amblyomma dubitatum and Amblyomma coelebs phylogenetically group together and are morphologically similar, though they seem to have distinct ecological preferences. Amblyomma coelebs has only been found in northern Misiones province, while the most numerous records of A. dubitatum come from the central area of the province. Until now, the distribution of A. yucumense in Argentina is restricted to Mocona and Yaboti. The findings in this study expand A. brasiliense , A. incisum , A. ovale and H. juxtakochi distribution ranges to the south, and we report for the first time the presence of A. yucumense in Argentina.

Host-parasite association between Didelphis albiventris (Didelphimorphia: Didelphidae) and Ixodes loricatus (Acari: Ixodidae) in their southern ranges

The parasitism of Ixodes loricatus Neumann on white-eared opposum, Didelphis albiventris Lund, was analysed in the southern ranges of both. In central Argentina, 118 wild opossums were captured from 2005 to 2012. Adults of I. loricatus were collected (prevalence = 66.1%, mean = 7.03, median = 4), but no immature stage. Tick infestation was not affected by sex (p = 0.27) or age (p = 0.37) of hosts. In line with previous studies about seasonality of larvae and nymphs of I. loricatus, adult tick infestation showed no seasonal trend. This lack of seasonal pattern of infestation for all parasitic stages of I. loricatus may indicate a life cycle governed by nidicolous behaviour, in such a way that this habit would contribute to minimize the influence of external environmental variables. The tick sex ratio was female biased, with two females per one male (p = 0.002). The absence of I. loricatus immatures on D. albiventris suggests that in the study region there is clear segregation of immatures in rodents and adults in marsupials.