Flavio A. Terassini

Geographical distribution of Amblyomma cajennense (sensu lato) ticks (Parasitiformes: Ixodidae) in Brazil, with description of the nymph of A. cajennense (sensu stricto)

BackgroundUntil recently, Amblyomma cajennense (Fabricius, 1787) was considered to represent a single tick species in the New World. Recent studies have split this taxon into six species. While the A. cajennense species complex or A. cajennense (sensu lato) (s.l.) is currently represented by two species in Brazil, A. cajennense (sensu stricto) (s.s.) and Amblyomma sculptum Berlese, 1888, their geographical distribution is poorly known.MethodsThe distribution of the A. cajennense (s.l.) in Brazil was determined by morphological examination of all lots of A. cajennense (s.l.) in two large tick collections of Brazil, and by collecting new material during three field expeditions in the possible transition areas between the distribution ranges of A. cajennense (s.s.) and A. sculptum. Phylogenetic analysis inferred from the ITS2 rRNA gene was used to validate morphological results. Morphological description of the nymphal stage of A. cajennense (s.s.) is provided based on laboratory-reared specimens.ResultsFrom the tick collections, a total 12,512 adult ticks were examined and identified as 312 A. cajennense (s.s.), 6,252 A. sculptum and 5,948 A. cajennense (s.l.). A total of 1,746 ticks from 77 localities were collected during field expeditions, and were identified as 249 A. cajennense (s.s.), 443 A. sculptum, and 1,054 A. cajennense (s.l.) [these A. cajennense (s.l.) ticks were considered to be males of either A. cajennense (s.s.) or A. sculptum]. At least 23 localities contained the presence of both A. cajennense (s.s.) and A. sculptum in sympatry. DNA sequences of the ITS2 gene of 50 ticks from 30 localities confirmed the results of the morphological analyses. The nymph of A. cajennense (s.s.) is morphologically very similar to A. sculptum.ConclusionOur results confirmed that A. cajennense (s.l.) is currently represented in Brazil by only two species, A. cajennense (s.s.) and A. sculptum. While these species have distinct distribution areas in the country, they are found in sympatry in some transition areas. The current distribution of A. cajennense (s.l.) has important implications to public health, since in Brazil A. sculptum is the most important vector of the bacterium Rickettsia rickettsii, the etiological agent of Brazilian spotted fever.

Description of a new argasid tick (Acari: Ixodida) from bat caves in Brazilian Amazon.

Abstract Nothoaspis amazoniensis n. sp. (Acari: Ixodida: Argasidae) is described from adult and immature ticks (nymph II, nymph I, larva) collected from bat caves in the Brazilian Amazon. Also, 16S rDNA sequences are provided. The diagnostic characters for adults are the presence of false shield or nothoaspis, an anteriorly projecting hood covering the capitulum, a medial extension of palpal article I (flaps), genital plate extending from coxa I to IV, absence of 2 setae on the internal margin of the flaps, a minute hypostome without denticles, presence of a central pore in the base of hypostome, and a reticulate surface pattern on the posterior half of the nothoaspis in males. The nymph II stage is characterized by a hood that is small in relation to the capitulum, short coxal setae, palpal flaps lacking setae on the internal margin, long hypostome, pointed with dentition 4/4 apically, and the anterior half of the body is covered by a cell-like configuration. Nymph I stage is characterized by a hood, small in relation to the capitulum, dorsum of the body covered by a cell-like configuration, venter integument covered by a cell-like configuration, and hypostome dentition 4/4 with apices that are “V”-shaped. Diagnostic characters of the larvae are the number and size of dorsal setae, and the shape of scutum and hypostome. The new species appears to have a life cycle with a larva that feeds on bats, a non-feeding nymphal stage (nymph I), a feeding nymphal stage (nymph II), and adults that probably represent non-feeding stages.

Notes on Population Dynamics of Amblyomma Ticks (Acari: Ixodidae) in Brazil

Abstract Previous population dynamics data, generated for Amblyomma parvum Aragão and Amblyomma cajennense (Fabricius) in Argentina and southeastern Brazil, have indicated that these ticks complete 1 generation per year, with larvae predominating in autumn, nymphs in winter, and mostly adults during spring and summer. The present study reports population dynamics data for free-living Amblyomma spp. ticks in northern Brazil (Amazon forest, latitude 10°S, 63°W), and for Amblyomma spp. ticks collected on birds in southeastern Brazil (latitude 23°S, 45°W). In northern Brazil, adult ticks predominated from mid-spring to mid-autumn, larvae predominated in early winter, and nymphs from mid-winter to mid-spring. Seven Amblyomma spp. were identified, although A. cajennense predominated in 1 of the 2 sites sampled. In southeastern Brazil, larval infestations on birds peaked in autumn, followed by a nymphal infestation peak in late winter. At least 32% and 75% of these larvae and nymphs, respectively, were identified as Amblyomma longirostre (Koch). Similar to previous work, the present study showed that Amblyomma spp. larvae and nymphs predominated during autumn–winter months, and mostly adults during spring–summer months, a pattern compatible with 1 generation/yr, even at latitude 10°S in northern Brazil.

New Reports of Antricola guglielmonei and Antricola delacruzi in Brazil, and a Description of a New Argasid Species (Acari)

Adults of 3 tick species (Acari: Argasidae) identified as Antricola guglielmonei, Antricola delacruzi, and Carios rondoniensis n. sp. were collected on bat guano in a cave in the state of Rondônia, western Amazon, Brazil. Adults of C. rondoniensis possess a unique combination of characters that distinguish them from all described adults in the Argasidae, i.e., a large spiracular plate densely filled with small goblets, a well-developed flap covering the female genital opening, and palpi containing several tufts of long setae on articles 2 and 3. Unlike Ornithodoros or other Carios species, adults of C. rondoniensis have a scooplike hypostome devoid of denticles, as in Antricola spp. Conversely, the presence of a pair of long posthypostomal setae, and a slitlike transverse fissure at the capsule opening of the Hallers organ, are characters of C. rondonensis that are also found in species of Carios and Ornithodoros, but not in Antricola species. Molecular analyses inferred from a portion of the 16S rRNA mitochondrial gene indicate that C. rondoniensis is phylogenetically closest to species of Carios, followed by species of Antricola, and then Ornithodoros. Because the highest bootstrap value linking C. rondoniensis to Carios spp. was 62%, further phylogenetic studies are needed to better evaluate the taxonomic status of the former species.

Comparison of two methods for collecting free-living ticks in the Amazonian forest

In the present study, we compared 2 methods for collecting ixodid ticks on the verges of animal trails in a primary Amazon forest area in northern Brazil. (i) Dragging: This method was based on passing a 1-m(2) white flannel over the vegetation and checking the flannel for the presence of caught ticks every 5-10 m. (ii) Visual search: This method consisted of looking for questing ticks on the tips of leaves of the vegetation bordering animal trails in the forest. A total of 103 adult ticks belonging to 4 Amblyomma species were collected by the visual search method on 5 collecting dates, while only 44 adult ticks belonging to 3 Amblyomma species were collected by dragging on 5 other collecting dates. These values were statistically different (Mann-Whitney Test, P=0.0472). On the other hand, dragging was more efficient for subadult ticks, since no larva or nymph was collected by visual search, whereas 18 nymphs and 7 larvae were collected by dragging. The visual search method proved to be suitable for collecting adult ticks in the Amazon forest; however, field studies should include a second method, such as dragging in order to maximize the collection of subadult ticks. Indeed, these 2 methods can be performed by a single investigator at the same time, while he/she walks on an animal trail in the forest.

Description of Adults and Nymph, and Redescription of the Larva, of Ornithodoros marinkellei (Acari: Argasidae), with Data on Its Phylogenetic Position

Abstract The argasid tick Ornithodoros marinkellei Kohls, Clifford, and Jones, 1969 was described 4 decades ago based on larval specimens collected from bats (Pteronotus spp.) in Colombia and Panama. Thereafter, larval O. marinkellei parasitizing bats were reported from Venezuela, Guyana, and Brazil. Herein, we describe the adults and nymph, and redescribe the larva of O. marinkellei based on specimens recently collected in the western Brazilian Amazon region. In contrast to all other known adult argasids, the idiosoma of both males and females of O. marinkellei is covered with sclerotized plaques. The idiosoma of the nymph of O. marinkellei is entirely micromamillated, and differs from the adults by the absence of plaques. The larva of O. marinkellei is morphologically similar to the larvae of the 2 other species belonging to the subgenus Subparmatus, i.e., Ornithodoros viguerasi Cooley and Kohls, 1941 and Ornithodoros mormoops Kohls, Clifford, and Jones, 1969. Because of the long and narrow dorsal plate, the larva of O. marinkellei is readily distinguished from O. viguerasi and O. mormoops. Comparison of our larvae from Brazil with O. marinkellei paratype specimens from Colombia confirmed their taxonomic identification. However, a few morphological differences, particularly in the size of the gnathosoma, were observed. Further studies are necessary to clarify whether O. marinkellei is a complex of different species, or a single species represented by morphologically polymorphic, and geographically distinct populations. Partial mitochondrial 16S rDNA gene sequences were generated for O. marinkellei specimens from Brazil, and compared with available homologous sequences in GenBank. Phylogenetic analyses revealed O. marinkellei to be distinct from the remaining argasid species available in GenBank, including other bat-associated tick species that are found in sympatry with O. marinkellei in the Neotropical region.

First report of Panstrongylus lignarius , Walker, 1873 (Hemiptera, Reduviidae, Triatominae), in the State of Rondônia, Brazil

INTRODUCTION: This study reports, for the first time, the presence of Panstrongylus lignarius in the State of Rondonia, Brazil. METHODS: Specimen of P. lignarius was collected from a flat in an urban area of the municipality of Porto Velho, Western Amazon. RESULTS: With this finding of P. lignarius, the number of Triatominae species in the State of Rondonia has increased from six to seven. CONCLUSIONS: The occurrence of P. lignarius is worrisome, because this species has been found to be naturally infected with Trypanosoma cruzi and there has been evidence of its domiciliation capabilities in other countries of South America.

Some biological and behavioral aspects of Amblyomma longirostre (Acari: Ixodidae) under laboratory and natural conditions

Abstract Amblyomma longirostre (Koch, 1844) has been reported as one of the most common ticks parasitizing wild animals in Brazil; however, information about its life cycle is inexistent, as well as information on its behavior in nature. In order to determine some aspects of the life cycle of A. longirostre in the laboratory, we performed infestations of larvae and nymphs on Serinus canaria (Common Canary - Passeriformes), Calomys callosus (Vesper mouse), Sphiggurus villosus (Brazilian porcupine), and Gallus gallus (chicks - no Passeriformes); this later host species only for larvae. While the overall recovery rates of engorged larvae and nymphs were low (at most 11.1%), the highest rates were for ticks that had fed on S. canaria (Passerifomes). This result is supported by field data, which indicate Passeriformes as preferable hosts for larvae and nymphs of A. longirostre. Interestingly, the suitability of the porcupine S. villosus as host for larvae and nymphs was statistically similar to S. canaria, although the recovery rates on the later host species were slightly higher. The Cricetidae mouse C. callosus displayed the lowest recovery rates (0–0.5%) of engorged ticks, indicating that mice might not be suitable hosts for A. longirostre under natural conditions. We also report three adult females of A. longirostre that were collected from two Bristle-spined porcupine Chaetomys subspinosus. Curiously, each of the three ticks was attached to the median third of a spine of the porcupines. The hypostome was surrounded by a cement-like structure at the spine external surface, but did not break through the external surface of the spine. Biological explanations for this behavior are discussed.