Ecological characterization of a tick community across a landscape gradient exhibiting differential anthropogenic disturbance in the Atlantic Forest ecoregion in Argentina.

An ecological analysis of a tick (Ixodida: Ixodidae) community across a landscape gradient presenting differential anthropogenic disturbance in the Atlantic Forest ecoregion in Argentina was performed. Ticks were collected from vegetation and hosts between September 2014 and August 2016. A total of 12 697 free-living ticks and 3347 specimens from hosts were collected, including 317 ticks infesting humans. The values obtained show considerable species diversity in the forest environment accompanied by low equitability. The similarity index derived from a comparison of forest and agricultural environments was higher than that calculated by comparing forest and urban environments. The data suggest that although a cycle of one generation per year is apparent in some species, more than one cohort may co-exist within the populations of some of these species. Well-marked patterns of the seasonal distribution of free-living tick species emerged in environments with no anthropic modification. The results indicate that forest environments are more suitable habitats than agricultural and urban environments for many species of native tick, but are unsuitable for exotic species that have successfully established in environments that have been modified by man.

Infection by Paramphistomidae trematodes in cattle from two agricultural regions in NW Uruguay and NW Spain.

The analysis of infection by Paramphistomidae trematodes was conducted in two agricultural regions with different knowledge on this parasitosis. Faecal and blood samples were collected from 374 cattle in Salto (NW Uruguay) where there is a lack of information about paramphistomosis. A total of 429 cattle from Galicia (NW Spain), an area with previous records of infection by gastric flukes, were sampled. Diagnostics of trematodosis was developed by using a copromicroscopic probe and an ELISA with excretory/secretory antigens collected from adult Calicophoron daubneyi (Paramphistomidae) specimens. Results were evaluated according intrinsic and extrinsic factors. In the Uruguay, the percentage of cattle passing Paramphistomidae-eggs by faeces was 7% (95% Confidence Interval 5, 10). A significantly higher prevalence of paramphistomosis in the Hereford × Angus cattle (OR=3.5) was recorded, as observed for the oldest ruminants (>3.5 years). An overall seroprevalence of 29% (25, 34) was obtained by ELISA, with the highest values in the Friesians (OR=3), the youngest bovines (<2.5 years) and dairy cattle (Friesians). Twenty-six percent (22, 30) of the cattle from Spain passed eggs by faeces, and cattle aged 2.5-7 years reached significant highest prevalences. By means of the ELISA, a percentage of 55 cattle (50, 59) had antibodies against the gastric fluke, and the highest seroprevalence was observed among the bovines under 6 years. It is concluded that paramphistomosis is on the increase in cattle from NW Spain, partly due to the absence of an effective treatment against the trematode. There is a need for reducing the risk of infection by Paramhistomidae spp. in cattle from Uruguay, especially by improving their management to avoid exposure to the gastric trematode. Further studies are in progress for identifying the species of Paramphistomidae affecting ruminants in Uruguay.

Maternal care in the soft tick Antricola marginatus.

Among spiders, scorpions, and whip spiders, a common type of maternal care consists of females carrying newly hatched offspring on their body for a few days until they are able to live independently. While this maternal care has been suggested to occur in different argasid tick species, it has been recorded only once, for Antricola marginatus in Cuba; however, this earlier record only superficially mentioned the occurrence of this behavior, with no further details. Here we report the occurrence of maternal care in the argasid tick A. marginatus under natural conditions in a cave at Yucatan, Mexico, where 8 A. marginatus females, while walking on bat guano, had their body entirely covered by a mean number of 305 ± 112 conspecific unfed larvae (range: 105-466). Larvae covered the entire idiosoma of the female tick, where they were motionless or displayed just slight movement. This result substantially expands the number of unique characters that have been found only in Antricola spp. ticks, when compared to the other tick genera. Our findings also indicate that maternal care evolved independently in different taxa of Arachnida, since it has been reported for species of Araneae, Scorpiones, and Amblypygi, and here for an Acari species.

Two new records of helminth parasites of domestic cat from Uruguay: Alaria alata (Goeze, 1782) (Digenea, Diplostomidae) and Lagochilascaris major Leiper, 1910 (Nematoda, Ascarididae).

Eight helminth taxa were recovered from the necropsy of four stray domestic cats from Colonia Miguelete, county of Colonia, Uruguay. Two of them are recorded for the first time for domestic cats in that country: Alaria alata (Goeze, 1782) from the small intestine (which is also the first trematode species found in domestic cat in Uruguay), and Lagochilascaris major Leiper, 1910 from the pharynx. The remaining helminth species found were Toxocara mystax (Zeder, 1800) and Spirometra sp. from the small intestine, Trichuris serrata (von Linstow, 1879) from the caecum, Eucoleus aerophilus (Creplin, 1839) from the trachea, and Pearsonema feliscati (Diesing, 1851) from the urinary bladder. Moreover, four female specimens of an unidentified Spiruroidea were collected from the stomach and small intestine of one host.

The ornithodoros (Alectorobius) talaje species group (Acari: Ixodida: Argasidae): description of Ornithodoros (Alectorobius) rioplatensis n. sp. from southern South America.

A new species of argasid tick, Ornithodoros (Alectorobius) rioplatensis Venzal, Estrada-Peña, & Mangold, is described from larval and adult specimens collected in Uruguay. Further specimens from Argentina, Paraguay, and Chile are ascribed to the new species. Key distinguishing characters of larvae of the species are the number of pairs of dorsal setae (19-20 but typically 20 in O. rioplatensis, compared with 16-17 but typically 17 in O. puertoricensis and O. talaje), and the length of the hypostome, which is clearly longer in O. rioplatensis than in O. talaje. Morphological details of the adults of these species are inadequate for taxonomic purposes. The genetic distance between O. puertoricensis and O. rioplatensis, based on 16S rDNA sequencing, is approximately 12.7%. Variability in some morphological features, using multivariate morphometric discrimination to assess congruence between populations, was examined among larval specimens of O. talaje and O. puertoricensis collected from the United States, and Central and South America. Larval specimens of O. talaje from Guatemala (near the type locality of the species) were morphologically different from Mexican and southern U.S. populations originally described as O. talaje. In the absence of DNA data for these populations, and because of inadequate statistical discrimination among body characters, we prefer to refer to the Mexican and U.S. material as O. nr. talaje until further analysis of population variability is conducted using an adequate sample size.

Amblyomma triste Koch, 1844 (Acari: Ixodidae): hosts and seasonality of the vector of Rickettsia parkeri in Uruguay.

Amblyomma triste Koch, 1844, the tick species most frequently involved in human bites in Uruguay, has been implicated as a vector of human rickettsiosis. Seasonal abundance of adult A. triste was examined by standard flagging at three sites where human tick bites and cases of the disease have been reported. Adult tick activity occurred from August to February (end of winter to mid summer in the southern hemisphere) with a peak in spring. Activity declined in step with decreasing temperatures and photoperiod during winter. This period of activity coincides with seasonal outbreaks of human rickettsiosis in the region. In a small mammal survey, the Sigmodontinae rodents Scapteromys tumidus (Waterhouse, 1837) and Oxymycterus nasutus (Waterhouse, 1837) and the small marsupial Monodelphis dimidiata (Wagner, 1847) were the main hosts for immature A. triste. Immature ticks were observed on hosts in November, well within the period of peak adult abundance. In stored collections, immature ticks were most often collected from January to March. These data suggest that one generation might be completed in 1 year. The main animal host for adult A. triste at our study sites was the domestic dog. Humans were afflicted by the tick in rural and suburban settlements where other host animals are scarce or extinct and where dogs are common.

Toxoplasma gondii: cross-immunity against the enteric cycle.

Eight of nine cats inoculated with strain ME-49 and challenged with three different strains of Toxoplasma were immune to oocyst shedding, as ascertained with bioassays of their feces. In a second experiment, only toxoplasma asexual stages were seen in H&E stained gut sections of cats treated with suppressive doses of sulfamerazine and pyrimethamine starting 2 days after oral inoculation with cysts of the strain ME-49 and killed 6 days later. In a third experiment, four cats were similarly inoculated and treated for 20 days. Six weeks later, the cats received an oral homologous challenge with cysts, and none shed toxoplasma oocysts. An acceptable level of cross-protection was achieved with strain ME-49, and therefore, it can be used as a candidate strain from which antigens could be tested for enteric protection.

Ticks (Ixodidae) on humans in South America.

Twenty eight species of Ixodidae have been found on man in South America (21 Amblyomma, 1 Boophilus, 2 Dermacentor, 2 Haemaphysalis, 1 Ixodes and 1 Rhipicephalus species). Most of them are rarely found on man. However, three species frequently parasitize humans in restricted areas of Argentina (A. neumanni reported from 46 localities), Uruguay (A. triste from 21 sites) and Argentina-Brazil (A. parvum from 27 localities). The most widespread ticks are A. cajennense (134 localities in Argentina, Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Paraguay, Suriname and Venezuela), A. ovale (37 localities in Argentina, Brazil, Ecuador, French Guiana, Guyana, Paraguay, Suriname and Venezuela) and A. oblongoguttatum (28 sites in Brazil, Colombia, French Guiana, Guyana, Suriname and Venezuela). Amblyomma aureolatum (18 localities in Argentina, Brazil, French Guiana and Paraguay), A. cajennense, and A. triste are vectors of rickettsioses to man in South America. A better understanding of the respective roles of these and other tick species in transmitting pathogens to humans will require further local investigations. Amblyomma ticks should be the main subjects of these studies followed by species of Boophilus, Dermacentor, Haemaphysalis and Rhipicephalus species. In contrast with North America, Europe and Asia, ticks of the genus Ixodes do not appear to be major players in transmitting diseases to human. Indeed, there is only one record of an Ixodes collected while feeding on man for all South America.

Notes on New World Persicargas ticks (Acari: Argasidae) with description of female Argas (P.) keiransi.

The female of Argas (Persicargas) keiransi Estrada-Peña, Venzal & González-Acuña (Acari: Argasidae) is described from specimens collected in the type locality in Chile. The female has a unique combination of characters in the dorsal cuticle and in the number and pattern of ventrolateral setae in the basis capituli. Additional features on tarsus I chaetotaxy and dorsal plate are provided for the larva of the species, as observed on flat specimens derived from engorged females collected in the type locality. Keys for the larvae of the New World Persicargas are provided as well as illustrations for prominent characters in hypostome and posterolateral setae. The mitochondrial 16S rDNA sequence of A. keiransi has been obtained, and an analysis of the phylogenetic relationships with other ticks is included. Phylogenetic analysis provides support for a Persicargas grouping of species, separated from species in Argas.

High-resolution predictive mapping for Boophilus annulatus and B. microplus (Acari: Ixodidae) in Mexico and Southern Texas.

In this study we use high-resolution satellite imagery to map habitat suitability for both Boophilus annulatus and B. microplus over an area covering parts of Texas and northeastern Mexico. The habitat for these tick species covers widely different regions. B. microplus finds satisfactory abiotic conditions in wet coastal habitats, whereas B. annulatus finds suitable habitat in the drier inner parts of southwestern Texas and northern Mexico; the two species have very different habitat requirements. We use habitat topology and data concerning abiotic habitat suitability to understand the effects of habitat configuration on tick abundance. This is achieved using traversability (habitat permeability) and recruitment (tick abundance at the patch level) to produce a model that computes the abundance of ticks at the patch level. Results from the computation are then compared with actual data on tick outbreaks at the Texas-Mexico border, as a test of the agreement between actual tick captures and abundance model predictions.

Changes in climate and habitat suitability for the cattle tick Boophilus microplus in its southern Neotropical distribution range.

We addressed the possible effects of several climate scenarios on habitat suitability (HS) for the cattle tick Boophilus microplus and the probability of producing permanent populations from introduced females of that tick in central parts of Argentina, using both a correlative model (derived from climate predictors) and a mechanistic (life cycle) model. There was high correlation (R2 = 0.866) between HS-derived and life cycle outputs for HS values higher than 0.52, suggesting that HS is a good estimator of the life cycle of the tick above a critical threshold of HS values. Scenarios with increased temperatures increased suitable habitats for the tick in southern parts of the study region, extending below parallel 34 degrees S, but suitable habitats remained limited in the west. A concurrent increase in rainfall produced a further increase of HS in these areas. Results from the life cycle model suggest that in areas of suitable habitat, permanent cattle tick populations are most probable if engorged females are introduced during mid-summer.

A collection of ticks (Ixodidae) from wild birds in Uruguay.

Thirty nine wild birds from seven families (Alcedinidae, Emberizidae, Furnariidae, Parulidae, Trochilidae, Turdidae and Tyrannidae) were caught from 4 to 7 of February, 2004 at Rincón da Vassoura (31 degrees 15' S 56 degrees 03' W) Department of Tacuarembó, Uruguay. Ninety one nymphs and forty one larvae of Ixodidae were recovered from them. The majority of ticks were conventionally identified but 16S mitochondrial rDNA sequences were obtained for larvae and nymphs of Amblyomma with uncertain specific status to be compared with sequences of species from this genus. The 16S rDNA of Haemaphysalis juxtakochi Cooley was also obtained. Most ticks, 1 nymph of Amblyomma longirostre (Koch), 5 larvae of Amblyomma aureolatum (Pallas) and 3 nymphs of Amblyomma spp., 10 nymphs and 71 larvae of H. juxtakochi, 23 nymphs and 12 larvae of Ixodes pararicinus Keirans and Clifford, were found on the 5 Turdus albicollis Vieillot and 6 Turdus rufiventris Vieillot (Turdidae) caught. One nymph of A. longirostre and 2 nymphs of I. pararicinus were collected from the only Syndactyla rufosuperciliata (Lafresnaye) (Furnariidae) captured; 1 larva of I. pararicinus was collected on one of two Basileuterus leucoblepharus (Vieillot) (Parulidae) trapped and 1 nymph of A. longirostre was found on one of nine Elaenia parvirostris Pelzeln (Tyrannidae) captured. All these findings constitute new host records with the exception of I. pararicinus on S. rufosuperciliata, and stress the importance of Turdus as hosts for I. pararicinus, H. juxtakochi and A. aureolatum. Nymphs of H. juxtakochi and Amblyomma spp. were also found on man and vegetation.

Reptile trade and the risk of exotic tick introductions into southern South American countries.

Ticks exotic for the Neotropical region were found on Python regius imported into Argentina and Chile. All ticks (7 males and 3 females) were classified as Amblyomma latum Koch, 1844 ( = Aponomma latum). Additionally, four lots comprising 18 males of the Argentinean tortoise tick, Amblyomma argentinae Neumann, 1904, were found on a terrestrial tortoise, Chelonoidis chilensis, and on three terrestrial tortoises (probably C. chilensis) imported to Uruguay presumably from Argentina). These findings alert us to the risk of expanding the distribution of reptile parasites and their diseases into regions previously free of these parasites.

Ticks (Ixodida: Ixodidae) parasitising humans in Uruguay.

During routine collections between November 1999 and November 2002, three species of tick (Amblyomma tigrinum, Amblyomma triste and Rhipicephalus sanguineus) were found on humans in southern Uruguay. The finding of R. sanguineus and A. triste on humans is of particular concern because these tick species may be involved in the transmission of the pathogens causing human rickettsioses, a type of disease already known to occur in Uruguay.

Amblyomma aureolatum (Pallas, 1772) and Amblyomma ovale Koch, 1844 (Acari: Ixodidae): hosts, distribution and 16S rDNA sequences.

DNA sequences of Amblyomma aureolatum (Pallas, 1772) and Amblyomma ovale Koch, 1844 were obtained to determine genetic differences between these tick species. Collections of these species are discussed in relation to distribution and hosts. Seven ticks collections (four from Brazil, one from Argentina, one from Uruguay and one from USA) house a total of 1272 A. aureolatum (224 males, 251 females, 223 nymphs and 574 larvae) and 1164 A. ovale (535 males, 556 females, 66 nymphs and 7 larvae). The length of the sequenced mitochondrial 16S rRNA gene fragment for A. aureolatum was 370bp and for A. ovale was 373bp. The DNA sequence analysis showed a 13.1% difference between the two species. Apart from one male A. ovale found on a toad, all adult ticks were found on mammals. The majority of adult specimens of both tick species were removed from Carnivora (96.1 and 84.3% of A. aureolatum and A. ovale, respectively), especially from dogs (53.1% of A. aureolatum, and 46.4% of A. ovale). Collections on wild Canidae were higher for A. aureolatum (23.3%) than for A. ovale (7.1%). On the other hand, collections of A. ovale adults on wild Felidae were higher (18.3%) than findings of A. aureolatum (9.2%). The contribution of other mammalian orders as hosts for adults of A. aureolatum and A. ovale was irrelevant, with the exception of Perissodactyla because Tapiridae contributed with 13.0% of the total number of A. ovale adults. Adults of both tick species have been found occasionally on domestic hosts (apart of the dog) and humans. Most immature stages of A. aureolatum were found on Passeriformes birds, while rodents and carnivores were the most common hosts for nymphs and larvae of A. ovale. A. aureolatum has been found restricted to the Neotropical region, covering the eastern area of South America from Uruguay to Surinam, including northeastern Argentina, eastern Paraguay, southeastern Brazil and French Guiana. A. ovale showed a distribution that covers the Neotropical region from central-northern Argentina throughout the Neotropics into the Nearctic region of Mexico with a few records from the USA, also with collection sites in Paraguay, Bolivia, most Brazilian states, Peru, Ecuador, French Guiana, Surinam, Guyana, Trinidad & Tobago, Venezuela, Colombia, Panama, Costa Rica, Nicaragua, Belize, Guatemala and several states of Mexico.

Cyst burden in the brains of Wistar rats fed Toxoplasma oocysts.

Six strains of Toxoplasma oocysts were used to infect groups of 4-24 Wistar rats, with each rat being fed 10(1)-10(4) oocysts from a single strain. After 2 months, the rats were killed, their brains screened for Toxoplasma cysts and then bioassayed in mice if negative. Toxoplasma was either observed in the form of brain cysts or was recovered using the bioassay, from 113 out of 138 (82%) rat brains. As few as ten oocysts were capable of initiating a brain infection that lasted for at least 2 months in eight of the nine rats inoculated. However, judging from bioassay 10(2)-10(4) oocysts did not give rise to progressively higher rates of infection. Brain cysts were seen in only 68 of 138 rats (49%). The number of Toxoplasma cysts formed in the brains of rats was generally in the order of tens to hundreds. The frequency of infection in the brains with Toxoplasma and the number of brain cysts formed appeared to be influenced by the individual resistance of the rats as well as by the doses of oocysts and the Toxoplasma strains used. The information gathered is considered to be a basis for a rat model of immunity against acquired toxoplasmosis.

Fetal Toxoplasma infection after oocyst inoculation of pregnant rats.

Six groups totalling 53 Wistar rats were fed 10(4)oocysts from one of six different Toxoplasma strains at 15 days of pregnancy. The overall transplacental transmission rate was 51%. This varied between 10% and 80%, dependent on the strain used. The strains of Toxoplasma which are more pathogenic for mice were transmitted transplacentally more frequently than the strains of intermediate or low pathogenicity. There were no statistically significant differences in the rate of congenital transmission of Toxoplasmain rats fed oocysts (present work) or cysts (previous work).

Argas (Persicargas) keiransi n. sp. (Acari: Argasidae), a parasite of the Chimango, Milvago c. chimango (Aves: Falconiformes) in Chile.

The larva of Argas (Persicargas) keiransi Estrada-Peña, Venzal & González-Acuña n. sp. is described from specimens collected on the neck of a chimango, Milvago c. chimango (Aves: Falconiformes) in the Chillán, Chile, in the Sub-Antarctic biogeographical region. The larva of the new species shares the tarsus I setal formula with A. (P.) giganteus, these being the only two Persicargas species with three pairs of ventral setae plus both av4 and pv4 setae. However, it is unique in having a dorsal plate "V" or "U" shaped, with the anterior end open, without the typical reticulated pattern present in the remaining species of the genus.

Residual infection of 15 toxoplasma strains in the brain of rats fed cysts.

Thirty-seven groups of 4-32 Wistar rats were 2-10(3) cysts of 15 Toxoplasma strains. After 2 months, the rats were euthanized and their brains screened for Toxoplasma cysts and bioassayed in mice if negative. The brains of 323 of 411 rats (78.6%) were found to be infected 2 months after inoculation with Toxoplasma cysts. Two hundred cysts were necessary to infect nearly 90% of the rats. With lower doses, only 60% of the rats had residual brain infection. Brain cysts were formed only in 146 of 411 rats (35.5%). The numbers of cysts formed were in the order of tens to hundreds, only occasionally one or two thousands. The mean percentage of rats with brain cysts, and the number of cysts formed in rat brains by different inocula, increased with higher doses of cysts and then declined. This pattern is difficult to explain and similar results regarding the number of cysts formed have been published. In relation to the mean percentage of rats infected, there appears to be a plateau in infection with the higher inocula. Neither the number of rats with cysts in their brains nor the numbers of cysts formed were dependent on the Toxoplasma strain used, with the exception of one strain. Instead, individual variations were marked, and are presumably related to variations in the individual genetic resistance to Toxoplasma infection in the rat. The information gathered is considered a preliminary step for a rat model of immunity against acquired toxoplasmosis.

Some factors influencing transmission of toxoplasma in pregnant rats fed cysts.

An overall 44% transplacental transmission rate was observed in 221 rats fed cysts of 12 Toxoplasma strains at 15 days of pregnancy, with a range of 0-90% transmission. Considerable variability in the transmission rate was seen among different groups of rats that received similar Toxoplasma inocula; this is attributed to genetically based susceptibility to Toxoplasma among individuals of the outbred Wistar strain of rats. Transplacental transmission was more frequent in Long Evans than in Wistar rats. Significant differences in the rate of transmission were not found between rats that were fed similar Toxoplasma inocula 6-8 days or 15 days after conception. The frequency of transmission was not affected by the strain or dose of Toxoplasma used.