Management strategies to minimize the use of synthetic chemical acaricides in the control of the cattle tick Rhipicephalus (Boophilus) microplus (Canestrini, 1888) in an area highly favourable for its development in Argentina.

The aim of this work was to test the efficacy of winter-spring control strategies against Rhipicephalus (Boophilus) microplus (Canestrini, 1888) (Ixodida: Ixodidae) in an area highly favourable for its development in Argentina. Control schemes using three or four annual applications of synthetic acaricides were evaluated. Furthermore, the dynamics of the non-parasitic phases of R. microplus were analysed to provide a framework for the application of pasture spelling as a tool for tick control. The treatment schemes provided appropriate levels of efficacy against R. microplus and also prevented the occurrence of the major peak in abundance of this tick in autumn. A significant overall effect against R. microplus can be achieved when the control strategies tested in this study are applied within the area most ecologically favourable for this tick in Argentina. Analysis of the dynamics of the non-parasitic phase of R. microplus indicates that the spelling period required to achieve a significant reduction of larvae in pastures fluctuates between 12 and 17 weeks if spelling is initiated in spring or early summer, but between 20 and 28 weeks if spelling is started in late summer, autumn or winter.

Efficacy of winter-spring strategic control against Rhipicephalus (Boophilus) microplus infestations on cattle in an area with ecological conditions highly favourable for the tick in northeast Argentina.

This work was performed to test the efficacy of winter-spring control strategies against Rhipicephalus (Boophilus) microplus (Ixodida: Ixodidae) infestations on cattle in the area ecologically most favourable for the development of this tick in Argentina. Two control schemes using three and four annual applications of acaricides, respectively, were evaluated. Animals in Group 1 were treated with ivermectin 3.15% on day 0, fluazuron on day 34, and fipronil on day 85. Animals in Group 2 were treated with ivermectin 3.15% on day 0, fluazuron on day 34, flumethrin on day 85, and fipronil on day 114. Animals in Group 3 represented the control group. Both treatment schemes provided appropriate levels of efficacy against R. microplus and also prevented the occurrence of the major peak in the frequency of this tick in autumn. The two treatment schemes were similar in terms of efficacy and thus the addition of a fourth treatment does not seem to confer any further advantage. The results of this work indicate that these strategic control methods provide appropriate levels of control against R. microplus.

Population dynamics of the cattle tick Rhipicephalus (Boophilus) microplus in a subtropical subhumid region of Argentina for use in the design of control strategies.

The population dynamics of Rhipicephalus microplus (Ixodida: Ixodidae) in northwest Argentina was analysed to support the design of strategic methods for its control. Both parasitic and non-parasitic phases were studied. The seasonal activity of R. microplus in its parasitic phase was characterized by three peaks in abundance: the first in mid-late spring; the second in summer, and the third in autumn. The non-parasitic phase of R. microplus was characterized by a long total non-parasitic period observed after exposures of females from mid-summer to early autumn, a short total non-parasitic period observed after exposures of females from late winter to late spring, a short period of larval longevity in early and mid-summer, and no hatch of the eggs produced by females exposed in mid- and late autumn and winter. Treatments of cattle administered during the period from late winter to late spring will act on small cohorts of R. microplus, preventing the emergence of larger generations in summer and autumn. A 17-week spelling period starting in late spring and early summer will be necessary to achieve optimal control of R. microplus free-living larvae. If spelling begins in mid- or late summer or in autumn, the required period will be 26-27 weeks.

Ecology and genetic variation of Amblyomma tonelliae in Argentina.

The ecology of Amblyomma tonelliae (Ixodida: Ixodidae), including its seasonal distribution and the development periods of each stage, was investigated during a study carried out over two consecutive years in northwestern Argentina. In addition, the genetic variation of this tick was studied through analyses of 16S rDNA sequences. Amblyomma tonelliae has a 1-year lifecycle characterized by a long pre-moult period in larvae with no development of morphogenetic diapause. Larvae peak in abundance during late autumn and early winter; nymphs peak in abundance in spring, and adults do so from late spring to early summer. Amblyomma tonelliae shows a marked ecological preference for the driest areas of the Chaco ecoregion. In analyses of 16S rDNA sequences in genes from different populations of A. tonelliae, values for nucleotide diversity and the average number of nucleotide differences showed genetic diversity within this species to be low. No significant differences were found in comparisons among populations.

Fatal bovine anaplasmosis in a herd with new genotypes of Anaplasma marginale, Anaplasma ovis and concurrent haemoplasmosis.

Haematological and molecular analysis of blood samples was carried out during an outbreak of bovine anaplasmosis in Hungary. Acute disease was observed in five animals, two of which died. Anaplasma-carrier state was diagnosed in 69 (92%) of cattle. Further evaluation of 24 blood samples revealed concurrent infections with Mycoplasma wenyonii and 'CandidatusM. haemobos' in 22 and 21 animals, respectively. In addition, two cows were identified with rickettsaemia. Regarding molecular investigation of potential hard tick vectors, Haemaphysalis inermis and Dermacentor marginatus males collected from the animals were PCR-negative. However, in one pool (out of 18) of Ixodesricinus males, and in six pools (out of 18) of D. reticulatus males the msp4 gene of Anaplasma marginale was detected. In the same I. ricinus pool Anaplasma ovis was also identified. All ticks were negative for haemoplasmas. Anaplasma sequences yielded 97-99% homology to sequences deposited in the Genbank. This is the first report of fatal bovine anaplasmosis associated with divergent A. marginale genotypes and concurrent 'CandidatusM. haemobos' infection, as well as of an A. ovis strain in ticks collected from cattle.

Developmental changes in salivary glands of nymphs and adults of the spinose ear tick Otobius megnini.

Otobius megnini has an autogenous 1 host life cycle, where larvae and nymphs stay attached inside the ear canal for long periods, but the adult tick is free living and can lay several egg batches without feeding. In order to obtain information about anatomical structures involved in this particular life cycle, nymphs and adults of O. megnini were dissected and salivary gland images were obtained in situ with the use of scanning electronic microscopy. Measurements of salivary alveoli were obtained with the use of ImageJ 1.40 g software. In the nymphs, the Type I alveoli are relatively small (mean diameter: 19.6 µm) compared with those of the adults (mean: 43.4 µm) and other soft ticks in the literature. Type II alveoli in nymphs are similar (mean: 82.6 µm) to previously described alveoli in adult soft ticks. In contrast, the adults of O. megnini Type II alveoli are smaller (mean: 36.8 µm) and have a wrinkled surface. These findings provide more evidence that Type I alveoli take part in absorption of moisture during the free-living tick stages.

Seasonal distribution of larvae and nymphs of Amblyomma tigrinum Koch, 1844 (Acari: Ixodidae).

The seasonality of immature stages of Amblyomma tigrinum was studied in an area of the Chaco phytogeographical province in Córdoba, Argentina by monthly collection of larvae from ground feeding birds and Sigmodontinae rodents, and nymphs from Caviidae rodents from May 2005 to April 2007. An apparent peak of abundance was found from December to May but differences with other months of the year were not significant (P>0.05). These and previous results suggest that the parasitic stages of A. trigrinum are active throughout the year and has more than one generation per year at the study site. Its life cycle appears to be regulated by temperature with no occurrence of diapause.

Field and laboratory studies in a Neotropical population of the spinose ear tick, Otobius megnini.

One ear of each of five cows on a property close to Dean Funes, province of Córdoba, Argentina, was inspected monthly from December 2004 to November 2006 to determine the presence of Otobius megnini (Dugès) and to ascertain its seasonality. Ticks were collected to study the biological parameters of larvae, nymphs and adult ticks. Groups of nymphs were also maintained at three different photoperiods at 25 degrees C. The abundance of immature stages was greatest during January-April and August-October in the first and second years of the study, respectively. No larvae successfully moulted. Nymphs weighing < 17 mg also failed to moult, but 89% of heavier nymphs moulted into adults. Nymphs moulting to males weighed less (49.5 +/- 16.09 mg) than nymphs moulting to females (98.1 +/- 34.08 mg). The pre-moult period was similar for nymphs moulting to either sex and significantly longer (P < 0.01) for female nymphs maintained at 25 degrees C compared with nymphs kept at 27 degrees C. No effect of photoperiod on the pre-moult periods of nymphs was detected. Female ticks produced a mean of 7.0 +/- 1.94 egg batches after a preoviposition period of 16.4 +/- 8.41 days for the first batch. The mean oviposition period was 61 +/- 20.8 days and the duration of oviposition for each batch varied from 1 to 6 days. The mean number of eggs per batch was 93.1 +/- 87.53. The minimum incubation period for the first egg batch was 13.6 +/- 2.77 days. The total number of eggs laid by each female was 651.6 +/- 288.90. Parthenogenesis was not observed. The reproductive efficiency index (REI) (number of eggs laid/weight of female in mg) was 5.5 +/- 1.26. Pearson's correlations showed a significant direct relationship between the weight of the female and number of eggs laid (P < 0.01) and REI (P < 0.05). Several of the biological values presented above for the tick population from the Neotropical zoogeographic region showed marked differences to equivalent values for O. megnini populations from the U.S.A. (Nearctic) and India (Oriental). Nevertheless, the only two sequences of 16S rDNA deposited in GenBank from ticks originating in Argentina and allegedly in the U.S.A. indicate that they are conspecific (99.8% agreement). We tentatively consider the biological differences among populations of this tick species to represent adaptations for survival at different conditions.

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.

Failure of ivermectin and eprinomectin to control Amblyomma parvum in goats: characterization of acaricidal activity and drug pharmacokinetic disposition.

The therapeutic efficacies of ivermectin (subcutaneous injection) and eprinomectin (topical treatment) given at two different dosage levels to goats naturally infested with Amblyomma parvum were assessed. Treatments included subcutaneous injection of ivermectin at 0.2 and 0.4mg/kg and extra-label pour-on administration of eprinomectin at 0.5 and 1mg/kgb.w. Ivermectin and eprinomectin failed to control Amblyomma parvum on goats. Treatment with ivermectin resulted in a low number of engorged female ticks in relation to untreated control goats and, at the highest dose rate (0.4mg/kg), the female engorgement weights were significantly lower and the pre-oviposition period significantly longer than those observed in ticks recovered from untreated control goats. The tick efficacy assessment was complemented in a separate group of tick-free goats with a pharmacokinetic characterization of eprinomectin (topically administered at 0.5, 1.0 and 1.5mg/kg) and ivermectin (subcutaneous treatment given at (0.2 and 0.4mg/kg) in goats. Heparinized blood samples were taken between 0 and 21 days post-treatment. Higher and more persistent drug plasma concentrations were recovered after the subcutaneous treatment with ivermectin compared to those obtained for eprinomectin topically administered. The understanding of the relationship among the pattern of drug absorption, the kinetic disposition and the resultant clinical efficacy is relevant to improve the poor performance observed for ivermectin and eprinomectin against A. parvum on goats.

Distribution, hosts, 16S rDNA sequences and phylogenetic position of the Neotropical tick Amblyomma parvum (Acari: Ixodidae).

The hosts, distribution, intraspecific genetic variation and phylogenetic position of Amblyomma parvum (Acari: Ixodidae) have recently been re-assessed. Data on this tick's hosts and distribution were obtained not only from existing literature but also from unpublished records. Sequences of the ticks' mitochondrial 16S ribosomal DNA (rDNA) were used to evaluate genetic variation among specimens of A. parvum from different localities in Argentina and Brazil, and to explore the phylogenetic relationships between this tick and other Amblyomma species. Although several species of domestic and wild mammal act as hosts for adult A. parvum, most collected adults of this species have come from cattle and goats. Caviid rodents of the subfamily Caviinae appear to be the hosts for the immature stages. So far, A. parvum has been detected in 12 Neotropical biogeographical provinces (Chaco, Cerrado, Eastern Central America, Venezuelan Coast, Pantanal, Parana Forest, Caatinga, Chiapas, Venezuelan Llanos, Monte, Western Panamanian Isthmus, and Roraima) but the Chaco province has provided significantly more specimens than any other (P<0.0001). The 16S rDNA sequences showed just 0.0%-1.1% divergence among the Argentinean A. parvum investigated and no more than 0.2% divergence among the Brazilian specimens. The observed divergence between the Argentinean and Brazilian specimens was, however, greater (3.0%-3.7%). Although there is now molecular and morphological evidence to indicate that A. parvum, A. pseudoparvum, A. auricularium and A. pseudoconcolor are members of a natural group, previous subgeneric classifications do not reflect this grouping. The subgeneric status of these tick species therefore needs to be re-evaluated. The 16S-rDNA-based evaluation of divergence indicates that the gene flow between Argentinean and Brazilian 'A. parvum' is very limited and that the Argentinean 'A. parvum' may be a different species to the Brazilian.

Prevalence of infection and 18S rRNA gene sequences of Cytauxzoon species in Iberian lynx (Lynx pardinus) in Spain.

The Iberian lynx (Lynx pardinus) is the most endangered felid in the world. Only about 160 individuals remain in 2 separate metapopulations in Southern Spain (Sierra Morena and Doñana). We obtained blood samples of 20 lynxes captured from 2004 to 2006, and determined the prevalence of infection and genetic diversity of Cytauxzoon spp. using 18S rRNA PCR and sequence analysis. Prevalence of infection was 15% (3 of 20). Cytauxzoon sp. was only detected in Sierra Morena. For phylogenetic analysis, we used the sequences reported in the present study and those characterized in different domestic and wild felids and ticks from North and South America, Asia and Europe. Three different Cytauxzoon sp. sequences were obtained. They were closely related to that obtained from a Spanish cat, but diverged in up to 1.0% with respect to the only previously reported sequence from an Iberian lynx. Conversely, the latter sequence clustered together with C. manul sequences obtained from Pallas cats (Otocolobus manul) in Mongolia. Our analysis yields a separate cluster of C. felis sequences from cats, wild felids and ticks in the United States and Brazil. These results suggest that at least 2 different Cytauxzoon spp. may be present in Iberian lynx. The apparent absence in one of the areas, together with the possibility of fatal cytauxzoonosis in lynxes makes necessary disease risks to be taken into account in management conservation strategies, such as translocations and re-introductions.

The ticks (Acari: Ixodida: Argasidae, Ixodidae) of Paraguay.

The ticks reported in Paraguay, which are here reviewed, can be categorized as 'endemic or established' (Argas persicus or a sibling species, Ornithodoros hasei, O. rostratus, O. rudis, O. talaje/O. puertoricensis, Amblyomma aureolatum, Am. auricularium, Am. brasiliense, Am. cajennense, Am. calcaratum, Am. coelebs, Am. dissimile, Am. dubitatum, Am. incisum, Am. longirostre, Am. nodosum, Am. ovale, Am. pacae, Am. parvum, Am. pseudoconcolor, Am. rotundatum, Am. scutatum, Am. tigrinum, Am. triste, Dermacentor nitens, Haemaphysalis juxtakochi, H. leporispalustris, Ixodes loricatus, Rhipicephalus microplus, and Rh. sanguineus), 'probably endemic or established' (Ar. miniatus, Ar. monachus, Am. argentinae, Am. humerale, Am. naponense, Am. oblongoguttatum, Am. pseudoparvum, I. aragaoi/I. pararicinus, I. auritulus, I. luciae), or 'erroneously reported from Paraguay' (O. coriaceus, Am. americanum and Am. maculatum). Most Paraguayan tick collections have been made in the Chaco phyto-geographical domain, in the central part of the country. Argas persicus or a related species, Am. cajennense, D. nitens, Rh. microplus and Rh. sanguineus are important parasites of domestic animals. Ornithodoros rudis, Am. aureolatum, Am. brasiliense, Am. cajennense, Am. coelebs, Am. incisum, Am. ovale and Am. tigrinum have all been collected from humans. In terms of public health, the collections of Am. cajennense and Am. triste from humans may be particularly significant, as these species are potential vectors of Rickettsia rickettsii and Ri. parkeri, respectively.

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.

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.

The natural hosts of larvae and nymphs of Amblyomma tigrinum Koch, 1844 (Acari: Ixodidae).

The hosts of larvae and nymphs of Amblyomma tigrinum, a tick whose adults feed on wild and domestic Canidae in South America, are uncertain. A 17 months survey was carried out trapping wild vertebrates in north-western Córdoba, Argentina, to evaluate their parasitism with A. tigrinum subadults. Larvae and nymphs of this tick species were identified conventionally and by comparison of 16S rDNA sequences with GenBank deposited sequences. A total of 207 small and medium-sized rodents and 182 birds were captured and examined for ticks. Most ticks on birds were from ground forest feeding birds (BB) with a minimal contribution of birds feeding in open pastures. All ticks from rodents were obtained from representatives of the families Cricetidae (SR) and Caviidae (MR). Percent of larvae infestation was higher (P<0.01, Chi-square distribution) in BB (55.2%) and SR (46.4%) than in MR (17.4%) and the same trend was found for number of larvae on these hosts (test of Kruskal-Wallis). Caviidae (only representative Galea musteloides) rodents were extremely prone to be infested with nymphs of A. tigrinum (94.2%) followed by BB (50.6%) and SR (3.6%) (P<0.01) and the same tendency was found for number of nymphs (P<0.01). The index of aggregation for nymphs on MR was the lowest (0.409) followed by nymphs on BB (0.706) which may be a consequence of higher and homogenous exposure of G. musteloides to host-seeking nymphs. Several BB are food source for both larvae and nymphs of A. tigrinum while for rodents larvae were common only on SR (mainly on the Sigmodontinae Akodon dolores and Graomys sp.) and nymphs feed almost exclusively on MR. Therefore, both birds and rodents are of importance for the survival strategy of A. tigrinum subadults. The plasticity of A. tigrinum to colonize areas with different climates plus the capacity of their subadults to feed on hosts widely distributed indicates that this tick has the potential to become a widespread parasite but this does not seem to be the actual situation. Several proposals are presented to further understand its ecology.

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.

Amblyomma tigrinum (Acari: Ixodidae): new data on hosts and biology of immature stages and on DNA composition.

Biological data of immature stages of Amblyomma tigrinum were obtained from larvae and nymphs both fed on rats and rabbits. Data from nymphs recovered from a wild rodent (Galea musteloides) are also reported. Additional results in DNA composition of males moulted from nymphs fed on laboratory and wild hosts are presented. The ticks were maintained in darkness at 27 +/- 1 degrees C and 83-86% RH. The mean recovery rates were 49.1% and 43.6% with a moulting success of 96.2% and 90.8% in larvae fed on rats and rabbits, respectively. The engorgement weights were almost identical in larvae recovered from both hosts. The mean recovery rates of nymphs were 37.3% and 69.9% in specimens fed on rats and rabbits, respectively. The moulting success was 94.5%, 100% and 98.1% in nymphs fed on rats, rabbits and G. musteloides, respectively. Nymphs from all hosts moulting to females were significantly heavier (P < 0.01) than those moulting to males despite their range of engorgement weight showed overlap. A higher proportion (>or=61.5%) of nymphs from all hosts moulted to females. Present results suggest that members of Rodentia and Lagomorpha are suitable hosts for the immature stages of A. tigrinum, contrasting with previous results from Brazilian colonies of this tick. The DNA sequence from ticks fed on G. musteloides showed 99.7% identity with that from ticks fed on rabbits and also with the DNA sequence already available (GenBank AY498562 ) for A. tigrinum.

Genetic diversity of Anaplasma marginale strains from cattle farms in the province of Palermo, Sicily.

Bovine anaplasmosis, caused by the tick-borne rickettsia Anaplasma marginale, is endemic in Sicily and results in economic loss to the cattle industry. This study was designed to characterize strains of A. marginale at the molecular level from cattle in the Province of Palermo, Sicily. Seropositivity of cattle >or=1 year old for A. marginale in the study area ranged from 62% to 100%. The observed prevalence of A. marginale infections in cattle herds ranged from 25% to 100%. Two predominant A. marginale msp4 genotypes were found. A positive correlation was found between the prevalence of infection and the presence of Rhipicephalus (Boophilus) annulatus. Phylogenetic analysis of msp4 sequences of European strains of A. marginale did not provide phylogeographical information. These results suggest that development of farm husbandry systems and vaccines for genetically heterogeneous populations of A. marginale are needed for control of anaplasmosis in this region of Sicily.