Assessment of habitat suitability for the cattle tick Rhipicephalus (Boophilus) microplus in temperate areas.

The aim of this research was to analyze and model the aptitude of temperate areas to support permanent populations of the cattle tick Rhipicephalus microplus, which is principally distributed in tropical and subtropical areas. This work integrated field-derived data of tick development with temperature and land-based models of tick spread in Argentina. The integrated analysis of the results suggest that approximately 31°S is the southern limit where R. microplus finds appropriate climatic conditions to be established permanently. The establishment of permanent populations of R. microplus south of this latitudinal threshold is currently restricted because the low temperatures in autumn and winter inhibit the development of its eggs, but the introduction of cattle infested with R. microplus from early spring to late summer in temperate areas could produce engorged females laying eggs that would originate viable larvae from late spring to winter. The comparison of the temperature-based maps of habitat suitability with those obtained considering the lands suitable for livestock grazing, clearly shows that the models based only on climatic variables overestimate the potential dispersal of the cattle tick. The outcomes of this study suggest that an increase of temperature in the months of autumn and winter around 2°-2.75 °C should be necessary for the establishment of permanent populations of R. micoplus in the region belonging to temperate areas. This would allow that a tick generation emerged in early spring due to the overwintering of eggs and larvae originated from females detached from cattle during autumn or early winter.

Exploring the ecological and evolutionary relationships between Rickettsia and hard ticks in the Neotropical region.

This study addresses a meta-analysis of the distribution of Rickettsia spp. in the Neotropical region, as well as their associations with ticks and vertebrates. A total of 219 published reports on Rickettsia in ticks in the target region were compiled, providing 599 records of 31 species of Rickettsia recorded in 50 species of Ixodidae. The aim is to capture the phylogenetic relationships between rickettsiae and the ticks carrying them in the target region, with a focus on the co-speciation ticks-rickettsiae. We compared the phylogeny of ticks, the records of rickettsiae, the environmental gradients colonized by ticks and the effect of the phylogenetic composition of vertebrates feeding ticks on the detection of Rickettsia in ticks. Results show that differences in rickettsial composition in ticks do not depend on the vertebrate's blood-source. This is the first time this result is demonstrated. This study pinpoints that some Neotropical rickettsial organisms are associated with well-defined phylogenetical clusters of ticks. Secondarily, and probably only in a few cases, rickettsiae share species of phylogenetically distant ticks distributed along a gradient of environmental traits in which the ticks overlap (i.e., the different strains of Rickettsia parkeri sensu lato). We outline the importance of some ticks that share hosts and habitat: these ticks may act as "bridges" for the circulation of rickettsial species. There are also many species of Rickettsia that have been detected so far in only one tick species, pointing to a tight relationship or to the lack of data preventing conclusions about the detection of these bacteria in other ticks. Two species, namely Rickettsia amblyommatis and Rickettsia bellii have been recorded in the majority of ticks in the region (mainly Amblyomma spp.) and seem to be not associated with definite tick species because they may be an essential symbiont of the ticks. We conclude that an adequate analysis of rickettsiae-ticks-habitat is necessary to address the human health issues derived from the infections by rickettsiae.

Species occurrence of ticks in South America, and interactions with biotic and abiotic traits.

The datasets of records of the distribution of ticks and their hosts are invaluable tools to understand the phylogenetic patterns of evolution of ticks and the abiotic traits to which they are associated. Such datasets require an exhaustive collection of bibliographical references. In most cases, it is necessary the confirmation of reliable identification of ticks, together with an update of the scientific names of the vertebrate hosts. These data are not easily available, because many records were published in the so-called "grey literature". Herein, we introduced the Dataset of Ticks in South America, a repository that collates data on 4,764 records of ticks (4,124 geo-referenced) with a special reference to an extra 2,370 records of ticks on cattle, together with a set of abiotic traits, curated from satellite-derived information over the complete target region. The dataset includes details of the phylogenetic relationships of the species of hosts, providing researchers with both biotic and abiotic traits that drive the distribution and evolution of ticks in South America.

Sex-Specific Linkages Between Taxonomic and Functional Profiles of Tick Gut Microbiomes.

Ticks transmit the most diverse array of disease agents and harbor one of the most diverse microbial communities. Major progress has been made in the characterization of the taxonomic profiles of tick microbiota. However, the functional profiles of tick microbiome have been comparatively less studied. In this proof of concept we used state-of-the-art functional metagenomics analytical tools to explore previously reported datasets of bacteria found in male and female Ixodes ovatus, Ixodes persulcatus, and Amblyomma variegatum. Results showed that both taxonomic and functional profiles have differences between sexes of the same species. KEGG pathway analysis revealed that male and female of the same species had major differences in the abundance of genes involved in different metabolic pathways including vitamin B, amino acids, carbohydrates, nucleotides, and antibiotics among others. Partial reconstruction of metabolic pathways using KEGG enzymes suggests that tick microbiome form a complex metabolic network that may increase microbial community resilience and adaptability. Linkage analysis between taxonomic and functional profiles showed that among the KEGG enzymes with differential abundance in male and female ticks only 12% were present in single bacterial genera. The rest of these enzymes were found in more than two bacterial genera, and 27% of them were found in five up to ten bacterial genera. Comparison of bacterial genera contributing to the differences in the taxonomic and functional profiles of males and females revealed that while a small group of bacteria has a dual-role, most of the bacteria contribute only to functional or taxonomic differentiation between sexes. Results suggest that the different life styles of male and female ticks exert sex-specific evolutionary pressures that act independently on the phenomes (set of phenotypes) and genomes of bacteria in tick gut microbiota. We conclude that functional redundancy is a fundamental property of male and female tick microbiota and propose that functional metagenomics should be combined with taxonomic profiling of microbiota because both analyses are complementary.

Different lines of evidence used to delimit species in ticks: A study of the South American populations of Amblyomma parvum (Acari: Ixodidae).

The goal of this work was to combine different lines of evidence besides that of molecular markers to delimit species in ticks when the molecular data are not totally congruent. Two groups (Argentina, Brazil) of South American populations of Amblyomma parvum were compared to test whether the splitting of these two lineages suggested by genetic analyses is complete. Comparative studies of reproductive compatibility, morphological analyses of fixed characters, and comparison of population distributions in spatially defined ecological niches were performed.The morphological comparisons of both discrete and morphometric characters showed no differences among A. parvum ticks from Argentina and Brazil. The intercrosses and backcrosses showed evidence of pre- and post-zygotic compatibility between the two groups. No significant differences in environmental traits were found which would justify the separation of the records of A. parvum in distinct groups. Although the gene flow between the two groups of populations is limited, the absence of reproductive barriers, the lack of significant morphological differences, and the absence of significant differences in the niche preferences indicate that populations of A. parvum from Argentina and Brazil should be treated as a single species. The speciation conjectures suggested by some analyses of mitochondrial DNA sequences were not supported when different lines of evidences were compared.

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.

Modeling the impact of climate and landscape on the efficacy of white tailed deer vaccination for cattle tick control in northeastern Mexico.

Cattle ticks are distributed worldwide and affect animal health and livestock production. White tailed deer (WTD) sustain and spread cattle tick populations. The aim of this study was to model the efficacy of anti-tick vaccination of WTD to control tick infestations in the absence of cattle vaccination in a territory where both host species coexist and sustain cattle tick populations. Agent-based models that included land cover/landscape properties (patch size, distances to patches) and climatic conditions were built in a GIS environment to simulate WTD vaccine effectiveness under conditions where unvaccinated cattle shared the landscape. Published and validated information on tick life cycle was used to build models describing tick mortality and developmental rates. Data from simulations were applied to a large territory in northeastern Mexico where cattle ticks are endemic and WTD and cattle share substantial portions of the habitat. WTD movements were simulated together with tick population dynamics considering the actual landscape and climatic features. The size of the vegetation patches and the distance between patches were critical for the successful control of tick infestations after WTD vaccination. The presence of well-connected, large vegetation patches proved essential for tick control, since the tick could persist in areas of highly fragmented habitat. The continued application of one yearly vaccination on days 1-70 for three years reduced tick abundance/animal/patch by a factor of 40 and 60 for R. annulatus and R. microplus, respectively when compared to non-vaccinated controls. The study showed that vaccination of WTD alone during three consecutive years could result in the reduction of cattle tick populations in northeastern Mexico. Furthermore, the results of the simulations suggested the possibility of using vaccines to prevent the spread and thus the re-introduction of cattle ticks into tick-free areas.

Rickettsia parkeri: a Rickettsial pathogen transmitted by ticks in endemic areas for spotted fever rickettsiosis in southern Uruguay / Rickettsia parkeri: patógeno rickettsial transmitido por garrapatas en áreas endémicas de rickettsiosis por fiebre manchada en el sur de Uruguay

At first Rickettsia conorii was implicated as the causative agent of spotted fever in Uruguay diagnosed by serological assays. Later Rickettsia parkeri was detected in human-biting Amblyomma triste ticks using molecular tests. The natural vector of R. conorii, Rhipicephalus sanguineus, has not been studied for the presence of rickettsial organisms in Uruguay. To address this question, 180 R. sanguineus from dogs and 245 A. triste from vegetation (flagging) collected in three endemic localities were screened for spotted fever group (SFG) rickettsiosis in southern Uruguay. Tick extracted DNA pools were subjected to PCR using primers which amplify a fragment of the rickettsial gltA gene. Positive tick DNA pools with these primers were subjected to a second PCR round with primers targeting a fragment of the ompA gene, which is only present in SFG rickettsiae. No rickettsial DNA was detected in R. sanguineus. However, DNA pools of A. triste were found to be positive for a rickettsial organism in two of the three localities, with prevalences of 11.8% to 37.5% positive pools. DNA sequences generated from these PCR-positive ticks corresponded to R. parkeri. These findings, joint with the aggressiveness shown by A. triste towards humans, support previous data on the involvement of A. triste as vector of human infections caused by R. parkeri in Uruguay.

Inicialmente, Rickettsia conorii fue señalada como el agente causal de la fiebre manchada en Uruguay, diagnosticada mediante pruebas serológicas. Posteriormente, Rickettsia parkeri fue detectada mediante técnicas moleculares en garrapatas Amblyomma triste colectadas sobre humanos. El vector natural de R. conorii, Rhipicephalus sanguineus, no ha sido estudiado en cuanto a rickettsias en Uruguay. Para abordar este tema, 180 R. sanguineus fueron colectados sobre perros y 245 A. triste sobre vegetación en tres localidades consideradas endémicas para fiebres manchadas en el sur de Uruguay. El ADN de las garrapatas fue extraído en pools y sometido a una primera PCR utilizando cebadores que amplifican un fragmento del gen gltA, presente en prácticamente todas las especies de Rickettsia. Las muestras positivas fueron sometidas a una segunda PCR con cebadores que amplifican un fragmento del gen ompA, presente sólo en rickettsias del grupo de las fiebres manchadas (GFM). No se detectó ADN rickettsial en R. sanguineus. Sin embargo, muestras de A. triste fueron positivas a rickettsiales en dos de las tres localidades estudiadas, con prevalencias de pools positivos del 11.8 y 37.5% respectivamente. La secuenciación del ADN evidenció la presencia de R. parkeri. Basados en estos resultados junto a los anteriores y la agresividad de A. triste hacia los humanos, se concluye que esta garrapata es vector de rickettsiosis humana por R. parkeri en Uruguay.

Rickettsia parkeri: a Rickettsial pathogen transmitted by ticks in endemic areas for spotted fever rickettsiosis in southern Uruguay.

At first Rickettsia conorii was implicated as the causative agent of spotted fever in Uruguay diagnosed by serological assays. Later Rickettsia parkeri was detected in human-biting Amblyomma triste ticks using molecular tests. The natural vector of R. conorii, Rhipicephalus sanguineus, has not been studied for the presence of rickettsial organisms in Uruguay. To address this question, 180 R. sanguineus from dogs and 245 A. triste from vegetation (flagging) collected in three endemic localities were screened for spotted fever group (SFG) rickettsiosis in southern Uruguay. Tick extracted DNA pools were subjected to PCR using primers which amplify a fragment of the rickettsial gltA gene. Positive tick DNA pools with these primers were subjected to a second PCR round with primers targeting a fragment of the ompA gene, which is only present in SFG rickettsiae. No rickettsial DNA was detected in R. sanguineus. However, DNA pools of A. triste were found to be positive for a rickettsial organism in two of the three localities, with prevalences of 11.8% to 37.5% positive pools. DNA sequences generated from these PCR-positive ticks corresponded to R. parkeri. These findings, joint with the aggressiveness shown by A. triste towards humans, support previous data on the involvement of A. triste as vector of human infections caused by R. parkeri in Uruguay.

Control of Rhipicephalus (Boophilus) microplus infestations by the combination of subolesin vaccination and tick autocidal control after subolesin gene knockdown in ticks fed on cattle.

Tick subolesin was shown in immunization trials using the recombinant protein to protect hosts against tick infestations. In this study, we demonstrated that subolesin vaccination and release of ticks after subolesin knockdown by RNA interference (RNAi) could be used for the control of Rhipicephalus (Boophilus) microplus tick infestations in cattle and suggested that the combination of these methods could increase the efficacy of cattle tick control under some circumstances. The greatest tick control was obtained when both release of ticks after subolesin knockdown and vaccination were used concurrently. However, modeling results suggested that vaccine efficacy could be increased if at least 80% of the ticks infesting cattle correspond to subolesin-knockdown ticks. The results of this proof-of-concept trial demonstrated the efficacy of the sterile acarine technique (SAT) through production of subolesin-knockdown larvae by dsRNA injection into replete females for the control of R. microplus tick infestations, alone or in combination with subolesin vaccination.

Ecology of Amblyomma neumanni (Acari: Ixodidae).

The life cycle of Amblyomma neumanni was described studying the seasonal distribution of free-living stages and parasitic phases during two consecutive years. Development periods of engorged ticks under different photoperiod conditions were recorded. Larvae of A. neumanni have the peak of abundance in autumn. Nymphs reach the peak in winter. Females were collected on cattle from autumn to late spring. The seasonal distribution pattern of females showed a bimodal curve, with a peak in autumn and other during early and middle spring. The engorged females exposed at shortest photoperiod regimen (10 h light-14 h dark) under both laboratory and field conditions undergo morphogenetic diapause, expressed as a delay in the oviposition. It is concluded that females of A. neumanni that feed and copulate in autumn undergo morphogenetic diapause, and they will lay eggs in spring, simultaneously with the females that feed and copulate in this season. Climate niche analysis shows that adequate suitability for A. neumanni depends mainly from temperature (mean, absolute maximum and minimum, and mean temperature in wettest and driest quarters) as well as from rainfall in warmest and coldest quarters. Sequences of 16S rDNA gene belonging to different populations of A. neumanni, showed no intraspecific genetic differentiation.

Allopatric speciation in ticks: genetic and reproductive divergence between geographic strains of Rhipicephalus (Boophilus) microplus.

BACKGROUND: The cattle tick, Rhipicephalus (Boophilus) microplus, economically impact cattle industry in tropical and subtropical regions of the world. The morphological and genetic differences among R. microplus strains have been documented in the literature, suggesting that biogeographical and ecological separation may have resulted in boophilid ticks from America/Africa and those from Australia being different species. To test the hypothesis of the presence of different boophilid species, herein we performed a series of experiments to characterize the reproductive performance of crosses between R. microplus from Australia, Africa and America and the genetic diversity of strains from Australia, Asia, Africa and America. RESULTS: The results showed that the crosses between Australian and Argentinean or Mozambican strains of boophilid ticks are infertile while crosses between Argentinean and Mozambican strains are fertile. These results showed that tick strains from Africa (Mozambique) and America (Argentina) are the same species, while ticks from Australia may actually represent a separate species. The genetic analysis of mitochondrial 12S and 16S rDNA and microsatellite loci were not conclusive when taken separately, but provided evidence that Australian tick strains were genetically different from Asian, African and American strains. CONCLUSION: The results reported herein support the hypothesis that at least two different species share the name R. microplus. These species could be redefined as R. microplus (Canestrini, 1887) (for American and African strains) and probably the old R. australis Fuller, 1899 (for Australian strains), which needs to be redescribed. However, experiments with a larger number of tick strains from different geographic locations are needed to corroborate these results.

Comments on controversial tick (Acari: Ixodida) species names and species described or resurrected from 2003 to 2008.

There are numerous discrepancies in recent published lists of the ticks of the world. Here we review the controversial names, presenting evidence for or against their validity and excluding some altogether. We also address spelling errors and present a list of 17 species described or resurrected during the years 2003-2008. We consider the following 35 tick species names to be invalid: Argas fischeri Audouin, 1826, Ornithodoros boliviensis Kohls and Clifford, 1964, Ornithodoros steini (Schulze, 1935), Amblyomma acutangulatum Neumann, 1899, Amblyomma arianae Keirans and Garris, 1986, Amblyomma bibroni (Gervais, 1842), Amblyomma colasbelcouri (Santos Dias, 1958), Amblyomma concolor Neumann, 1899, Amblyomma cooperi Nuttall and Warburton, 1908, Amblyomma curruca Schulze, 1936, Amblyomma cyprium Neumann, 1899, Amblyomma decorosum (Koch, 1867), Amblyomma nocens Robinson, 1912, Amblyomma perpunctatum (Packard, 1869), Amblyomma striatum Koch, 1844, Amblyomma superbum Santos Dias, 1953, Amblyomma testudinis (Conil, 1877), Amblyomma trinitatis Turk, 1948, Dermacentor confractus (Schulze 1933), Dermacentor daghestanicus Olenev, 1928, Haemaphysalis himalaya Hoogstraal, 1966, Haemaphysalis vietnamensis Hoogstraal and Wilson, 1966, Hyalomma detritum Schulze, 1919, Ixodes apteridis Maskell, 1897, Ixodes donarthuri Santos Dias, 1980, Ixodes kempi Nuttall, 1913, Ixodes neotomae Cooley, 1944, Ixodes rangtangensis Teng, 1973, Ixodes robertsi Camicas, Hervy, Adam and Morel, 1998, Ixodes serrafreirei Amorim, Gazetta, Bossi and Linhares, 2003, Ixodes tertiarius Scudder, 1885, Ixodes uruguayensis Kohls and Clifford, 1967, Ixodes zealandicus Dumbleton, 1961, Ixodes zumpti Arthur, 1960 and Rhipicephalus camelopardalis Walker and Wiley, 1959. We consider the following 40 names valid: Argas delicatus Neumann, 1910, Argas vulgaris Filippova, 1961, Ornithodoros aragaoi Fonseca, 1960, Ornithodoros dugesi Mazzoti, 1943, Ornithodoros knoxjonesi Jones and Clifford, 1972, Ornithodoros marocanus Velu, 1919, Ornithodoros nattereri Warburton, 1927, Amblyomma beaurepairei Vogelsang and Santos Dias, 1953, Amblyomma crassipes (Neumann, 1901), Amblyomma echidnae Roberts, 1953, Amblyomma fuscum Neumann, 1907, Amblyomma orlovi (Kolonin, 1995), Amblyomma parkeri Fonseca and Aragão, 1952, Amblyomma pseudoconcolor Aragão, 1908, Bothriocroton oudemansi (Neumann, 1910), Bothriocroton tachyglossi (Roberts, 1953), Dermacentor abaensis Teng, 1963, Dermacentor confragus (Schulze 1933), Dermacentor ushakovae Filippova and Panova, 1987, Haemaphysalis anomaloceraea Teng, 1984, Haemaphysalis filippovae Bolotin, 1979, Haemaphysalis pavlovskyi Pospelova-Shtrom, 1935, Hyalomma excavatum Koch, 1844, Hyalomma isaaci Sharif, 1928, Hyalomma rufipes Koch, 1844, Hyalomma turanicum Pomerantzev, 1946, Ixodes arabukiensis Arthur, 1959, Ixodes boliviensis Neumann, 1904, Ixodes columnae Takada and Fujita, 1992, Ixodes maslovi Emel'yanova and Kozlovskaya, 1967, Ixodes sachalinensis Filippova, 1971, Ixodes siamensis Kitaoka and Suzuki, 1983, Ixodes sigelos Keirans, Clifford and Corwin, 1976, Ixodes succineus Weidner, 1964, Rhipicephalus aurantiacus Neumann, 1907, Rhipicephalus cliffordi Morel, 1965, Rhipicephalus pilans Schulze, 1935, Rhipicephalus pseudolongus Santos Dias, 1953, Rhipicephalus serranoi Santos Dias, 1950 and Rhipicephalus tetracornus Kitaoka and Suzuki, 1983.

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 Haller's 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.

Detection of Alpha and Gamma-Proteobacteria in Amblyomma triste (Acari: Ixodidae) from Uruguay.

Amblyomma triste is the most prevalent tick species reported in human tick bites in Uruguay and has been found to be infected with Rickettsia parkeri, but no other microorganisms have been reported from this tick. A sample of 254 adults of A. triste was collected by flagging on vegetation in suburban areas in southern Uruguay. Pools of five ticks were assembled and a screening for the DNA from the resulting 51 pools was realized by PCR assays using primers for amplifying a fragment of 16S rRNA gene for members of Anaplasmataceae. Seventeen pools were positive (33%) and the sequenciation of the gene fragment amplified revealed the presence of a putative new Alpha-Proteobacterium (denominated Atri-uru). The phylogenetic analysis showed that this microorganism is closely related to the symbiont of I. ricinus denominated 'Candidatus Midichloria mitochondrii' and other associated organisms. This rickettsial symbiont of ticks is included in a recent new clade proposed for the Alpha subclass of the Proteobacteria. The discovery of this bacterium in A. triste is the first evidence of this group of Rickettsiales detected in the Genus Amblyomma, and the first record in South America. Also, in two of 17 positive samples a Gamma-Proteobacterium related to Francisella-like organisms was detected.

Effects produced by the feeding of larvae of Ornithodoros aff. puertoricensis (Acari: Argasidae) on laboratory mice.

The clinical picture produced by the feeding of larvae of Ornithodoros aff. puertoricensis on laboratory mice, was studied using different larval infestation protocols that included 30, 40 or 50 larvae per mouse and control uninfested groups. Clinical effects appeared around 72 h of larval feeding, having a first stage characterized by hyperaemia in both nasal and ocular mucosa, followed by respiratory symptoms (96-120 h) and nervous incoordination (120-144 h). No one mouse evidenced paralysis, and nervous symptoms were never observed in animals infested with only 30 larvae. High mortality (commonly up to 70%) was observed in mice with respiratory symptoms, while 100% of animals in the nervous phase died between 168 and 192 h after the beginning of larval feeding. When some infested mice were treated with a solution of Amitraz the larvae were killed and reversion of symptoms was observed. These effects are ascribed to the presence of a toxin in the saliva of the feeding larvae.

Larval feeding performance of two Neotropical Ornithodoros ticks (Acari: Argasidae) on reptiles.

This paper determines the feeding performance of the larvae of two Neotropical soft tick species namely Ornithodoros rostratus Aragão, 1911 and O. puertoricensis Fox, 1947 on reptiles (Gekkonidae) using rabbits, mice and guinea pigs to provide comparisons with feeding features on mammals. O. puertoricensis produced a larval feeding rate of 63% on reptiles, while that of O. rostratus was only 20%. But the final success (attaching + feeding) was similar, 12.4% for O. puertoricensis and 10.4% for O. rostratus. The feeding time was also very different for both species. In O. puertoricensis, detachment begins at 16th day and lasts until day 27. In O. rostratus detachment begins at 1.5 h and lasts until day 10. These values of feeding on reptiles are different from those obtained on mammals (average 5.6 days for O. puertoricensis and 2.9 for O. rostratus).

Ixodes (Ixodes) pararicinus Keirans & Clifford, 1985 (Acari: Ixodidae): description of the immature stages, distribution, hosts and medical/veterinary importance.

The immature stages of the Neotropical tick Ixodes (Ixodes) pararicinus Keirans & Clifford, 1985 are described from specimens in a laboratory colony initiated from engorged females collected on cattle and larvae fed on mice and chickens. The larva and nymph of I. pararicinus are described using SEM micrographs as well as drawings for some features of the larva. Additionally, immature stages of I. pararicinus collected on wild mice and birds in Uruguay and Argentina were compared with specimens from the laboratory colony. A taxonomic key to the nymphs of the species of the ricinus complex established in the Western Hemisphere is presented. The distribution of I. pararicinus comprises Argentina, Colombia and Uruguay, but it is also probably established in Bolivia, Brazil, Chile and Peru. Most adult ticks of this species have been found on introduced domestic artiodactyles, although Neotropical deer species must have been the ancestral host. Larvae and nymphs of I. pararicinus have also been found on sigmodontine rodents and passeriform birds. Although I. pararicinus is a member of the ricinus complex, which contains the main vectors of Borrelia burgdorferi (sensu lato), there are few studies concerning its potential for pathogen transmission.

Rickettsia parkeri in Amblyomma triste from Uruguay.

Our goal was to detect whether spotted fever group Rickettsia are found in the suspected vector of rickettsioses, Amblyomma triste, in Uruguay. Rickettsia parkeri was detected in A. triste, which suggests that this species could be considered a pathogenic agent responsible for human rickettsioses in Uruguay.

Three new species of Antricola (Acari: Argasidae) from Brazil, with a key to the known species in the genus.

Three new species of Antricola (Acari: Argasidae) are described from adult specimens collected on bat guano in different caves in Brazil. The female of Antricola guglielmonei n. sp. is easily determined by the presence of 2 smooth, depressed areas lacking setae in the posterolateral portions of the dorsum of the idiosoma, together with the partial fusion of the tubercles in the anteromedian portion of the idiosoma. The male of this species has a small spiracular plate surrounded by a pattern of tubercles disposed concentrically in its dorsal portion. Both sexes have cervical grooves very slightly marked. Antricola delacruzi n. sp. represents the only Antricola species with the dorsum of the idiosoma devoid of tubercles in both sexes and with scarce and minute setae placed over the smooth cuticle. The female of A. inexpectata n. sp. is known only from a few specimens. In this species, lines of smooth cuticle lacking setae separate the tubercles of the dorsum. In addition, there are 3 clumps of plumose setae close to the spiracular plate, in the ventrolateral portions of the idiosoma, in 3 well-delimited regions over cuticular thickenings. These 3 species share the peculiarity of a Haller's organ with the anterior pit bearing only 7 + 2 setae. The collection of these new species in Brazilian caves greatly expands the known range of the genus. A key to the adults of all known species of the genus is provided.