Records of ticks (Acari: Ixodidae) on humans and distribution of spotted-fever cases and its tick vectors in Paraná State, southern Brazil.

Brazilian spotted fever (BSF) is the deadliest rickettsiosis in the world. Although the epidemiology of the disease has been established in Brazil, there are still limited data available on distribution of tick vectors and tick species parasitizing humans in the country, particularly in Paraná State. The State of Paraná is located in the southern region of the country and is covered by two biomes: Atlantic rainforest and Cerrado. Thus, the aims of this study were i) to map the distribution of SF tick vectors, ii) to describe and map the distribution of human parasitism by ticks, and iii) to map the distribution of fatal and non-fatal spotted fever (SF) cases in Paraná State, southern Brazil. Data were reviewed and compiled from previous published reports, and also from two scientific collections of Paraná State. SF cases were retrieved from the Brazilian Notifiable Diseases Information System. A total of 50 cases of human parasitism by ticks were recorded, with a total of 64 (22 males, 12 females, 30 nymphs) ticks collected. The following 12 tick species were identified: Amblyomma aureolatum, Amblyomma brasiliense, Amblyomma calcaratum, Amblyomma dubitatum, Amblyomma incisum, Amblyomma longirostre, Amblyomma ovale, Amblyomma parkeri, Amblyomma scalpturatum, Amblyomma sculptum, Haemaphysalis juxtakochi and Rhipicephalus sanguineus sensu lato (s.l.). The most prevalent tick species associated to cases of human parasitism were A. sculptum (13/50; 26 %), A. aureolatum (10/50; 20 %), A. brasiliense (5/50; 10 %), A. ovale (5/50; 10 %) and A. parkeri (4/50; 8%). A total of 51 non-fatal and five fatal SF cases were recorded. Data from this study highlights the need for monitoring ticks parasitizing humans aiming early detection of tick-borne diseases cases, particularly BSF in Paraná State, southern Brazil.

Climate change implications for the distribution of the babesiosis and anaplasmosis tick vector, Rhipicephalus (Boophilus) microplus.

Climate change ranks among the most important issues globally, affecting geographic distributions of vectors and pathogens, and inducing losses in livestock production among many other damaging effects. We characterized the potential geographic distribution of the ticks Rhipicephalus (Boophilus) microplus, an important vector of babesiosis and anaplasmosis globally. We evaluated potential geographic shifts in suitability patterns for this species in two periods (2050 and 2070) and under two emissions scenarios (RCPs 4.5 and 8.5). Our results anticipate increases in suitability worldwide, particularly in the highest production areas for cattle. The Indo-Malayan region resulted in the highest cattle exposure under both climate change projections (2050), with increases in suitability of > 30%. This study illustrates how ecological niche modeling can be used to explore probable effects of climate change on disease vectors, and the possible consequences on economic dimensions.

First Report of the Introduction of an Exotic Tick, Amblyomma coelebs (Acari: Ixodidae), Feeding on a Human Traveler Returning to the United States from Central America.

Introduction of ticks into the United States that can carry disease-causing pathogens to humans, companion animals, and wildlife has accelerated in recent years, mostly due to globalization, frequency of travel, and a rise in legal and illegal animal trades. We hereby report for the first time introduction of a live fully engorged Amblyomma coelebs feeding on a human into the United States from Central America. Amblyomma coelebs is geographically distributed in the Neotropical region and reaches the southern states of Mexico. This species is capable of transmitting a number of pathogens of public health and veterinary importance including spotted fever group rickettsiae, raising concern that A. coelebs, if it became established in the United States, might also be able to carry these pathogens. Considering the risks of exotic ticks as vectors of numerous pathogens and their potential to establish new populations under conducive climatic and habitat conditions, rigorous inspection practices of imported livestock and pet animals at ports of entry are vital. It is also important for travelers and practitioners to develop a heightened awareness of the public health risks associated with the unintended importation of exotic ticks and the potential such parasites have for breaching United States biosecurity defenses.

Risks of cattle babesiosis (Babesia bovis) outbreaks in a semi-arid region of Argentina.

The epidemiology of Babesia bovis was studied in terms of enzootic stability/instability and husbandry and abiotic factors influencing B. bovis transmission rate in northeastern Santiago del Estero province, Argentina. The area is of limited suitability for its only vector in Argentina, the tick Rhipicephalus microplus. The proportion of calf herds in a state of enzootic stability/instability to B. bovis was determined and husbandry practices and abiotic factors associated with variations in B. bovis transmission rates were explored using a cross-sectional observational study design. Daily probability of infection (inoculation rate, h) with B. bovis was calculated from age-specific seroprevalence via ELISAi in 58 herds of 4.5-8.5-month-old calves. Herds were considered to be in enzootic instability (EI) when h < 0.005, and therefore inferred to be at risk of babesiosis outbreaks. Husbandry practices associated with differences in B. bovis transmission were analyzed using generalized linear models. Sixty-two percent of herds were found to be in an EI situation for B. bovis. Calves raised exclusively on permanent pastures -where higher cattle density is achieved- were exposed to higher B. bovis inoculation rates (h = 0.0063, 95% CI 0.0032-0.0123) than those reared under forage combinations (h = 0.0024, 95% CI 0.0011-0.0051) (P =  0.05). In addition, calves from herds located in the area of intermediate suitability for R. microplus development were more likely to become infected with B. bovis (h = 0.0067, 95% CI 0.0037-0.0121) than those reared in the ecologically unfavorable area for the vector (h = 0.0023, 95% CI 0.0010-0.0049) (P =  0.02). Neither the frequency of treatment with acaricides nor the use of long-acting acaricides to control R. microplus influenced the inoculation rate (P =  0.99 and P =  0.26, respectively). This result indicates that current R. microplus control schemes are not effective in reducing B. bovis transmission. Enzootic instability still prevails in the study area despite the drastic changes occurred in cattle production system. However, 38% of herds did reach enzootic stability; therefore, a specific epidemiological status cannot be assumed at a regional level. Yearly determination of the immunological status of each calf cohort is considered a proper approach to decision-making in vaccination against B. bovis.

Ticks as potential vectors of Mycobacterium leprae: Use of tick cell lines to culture the bacilli and generate transgenic strains.

Leprosy is an infectious disease caused by Mycobacterium leprae and frequently resulting in irreversible deformities and disabilities. Ticks play an important role in infectious disease transmission due to their low host specificity, worldwide distribution, and the biological ability to support transovarial transmission of a wide spectrum of pathogens, including viruses, bacteria and protozoa. To investigate a possible role for ticks as vectors of leprosy, we assessed transovarial transmission of M. leprae in artificially-fed adult female Amblyomma sculptum ticks, and infection and growth of M. leprae in tick cell lines. Our results revealed M. leprae RNA and antigens persisting in the midgut and present in the ovaries of adult female A. sculptum at least 2 days after oral infection, and present in their progeny (eggs and larvae), which demonstrates the occurrence of transovarial transmission of this pathogen. Infected tick larvae were able to inoculate viable bacilli during blood-feeding on a rabbit. Moreover, following inoculation with M. leprae, the Ixodes scapularis embryo-derived tick cell line IDE8 supported a detectable increase in the number of bacilli for at least 20 days, presenting a doubling time of approximately 12 days. As far as we know, this is the first in vitro cellular system able to promote growth of M. leprae. Finally, we successfully transformed a clinical M. leprae isolate by inserting the reporter plasmid pCHERRY3; transformed bacteria infected and grew in IDE8 cells over a 2-month period. Taken together, our data not only support the hypothesis that ticks may have the potential to act as a reservoir and/or vector of leprosy, but also suggest the feasibility of technological development of tick cell lines as a tool for large-scale production of M. leprae bacteria, as well as describing for the first time a method for their transformation.

Possible Northward Introgression of a Tropical Lineage of Rhipicephalus sanguineus Ticks at a Site of Emerging Rocky Mountain Spotted Fever.

Increasing rates of Rocky Mountain spotted fever (RMSF) in the southwestern United States and northern Mexico underscore the importance of studying the ecology of the brown dog tick, Rhipicephalus sanguineus, the vector in that region. This species is reported to comprise distinct tropical and temperate lineages that may differ in vectorial capacity for RMSF and are hypothesized to be limited in their geographical range by climatic conditions. In this study, lineage was determined for ticks from 9 locations in California, Arizona, and Mexico by DNA sequencing of 12S, 16S, and D-loop ribosomal RNA. As expected, sites in northern California and eastern Arizona had temperate-lineage ticks, and phylogenetic analysis revealed considerable genetic variability among these temperate-lineage ticks. However, tropical-lineage ticks extended north from Oaxaca, Mexico were well established along the entire border from San Diego, California to western Arizona, and were found as far north as Lytle Creek near Los Angeles, California (a site where both lineages were detected). Far less genetic variability in the tropical lineage despite the large geographical distances is supportive of a hypothesis of rapid northward expansion. Discovery of the tropical lineage north of the identified climatic limitations suggests that more work is needed to characterize this tick's ecology, vectorial capacity, expansion, possible evolution, and response to climate change.

Ticks as potential vectors of Mycobacterium leprae: use of tick cell lines to culture the bacilli and generate transgenic strains

Leprosy is an infectious disease caused by Mycobacterium leprae and frequently resulting in irreversible deformities and disabilities. Ticks play an important role in infectious disease transmission due to their low host specificity, worldwide distribution, and the biological ability to support transovarial transmission of a wide spectrum of pathogens, including viruses, bacteria and protozoa. To investigate a possible role for ticks as vectors of leprosy, we assessed transovarial transmission of M. leprae in artificially-fed adult female Amblyomma sculptum ticks, and infection and growth of M. leprae in tick cell lines. Our results revealed M. leprae RNA and antigens persisting in the midgut and present in the ovaries of adult female A. sculptum at least 2 days after oral infection, and present in their progeny (eggs and larvae), which demonstrates the occurrence of transovarial transmission of this pathogen. Infected tick larvae were able to inoculate viable bacilli during blood-feeding on a rabbit. Moreover, following inoculation with M. leprae, the Ixodes scapularis embryo-derived tick cell line IDE8 supported a detectable increase in the number of bacilli for at least 20 days, presenting a doubling time of approximately 12 days. As far as we know, this is the first in vitro cellular system able to promote growth of M. leprae. Finally, we successfully transformed a clinical M. leprae isolate by inserting the reporter plasmid pCHERRY3; transformed bacteria infected and grew in IDE8 cells over a 2-month period. Taken together, our data not only support the hypothesis that ticks may have the potential to act as a reservoir and/or vector of leprosy, but also suggest the feasibility of technological development of tick cell lines as a tool for large-scale production of M. leprae bacteria, as well as describing for the first time a method for their transformation.

Efficacy of sarolaner (Simparic™) against induced infestations of Amblyomma cajennense on dogs.

BACKGROUND: Amblyomma cajennense is the main vector of Rickettsia rickettsii which causes Brazilian spotted fever. This adult tick preferably infests horses and capybaras, but has low host specificity during its immature stages, thus posing a threat to humans and dogs. In this study, the efficacy of sarolaner (Simparic™/Simparica®, Zoetis) when administered once orally to dogs at 2 mg/kg was evaluated against induced infestations of A. cajennense nymphs for up to 35 days after treatment. METHODS: Based on pretreatment tick counts, 20 dogs were randomly allocated to treatment with sarolaner (Simparic™) dosed at 2 mg/kg of body weight or a placebo on Day 0 of the study. Artificial infestations were performed using laboratory raised A. cajennense nymphs on study days -2, 5, 12, 19, 26 and 33. Efficacy was determined at 48 h post-treatment or post-infestation at each time point relative to the counts for dogs that received placebo. RESULTS: There were no adverse reactions to treatment. A single dose of sarolaner (Simparic™) provided 100% efficacy on study days 2, 7 and 14; and ≥ 99.6% on days 21, 28 and 35. Geometric mean live tick counts for sarolaner were significantly lower than those for placebo on all days (P < 0.0001). CONCLUSIONS: Under the conditions of the present study, sarolaner (Simparic™) administered once orally at 2 mg/kg provided 100% efficacy against existing infestations and ≥ 99.6% efficacy within 48 h against weekly challenges of A. cajennense for at least 35 days after treatment.

Vectorial competence of Amblyomma tonelliae to transmit Rickettsia rickettsii.

The aim of this work was to test the vectorial competence of Amblyomma tonelliae (Ixodida: Ixodidae) to transmit Rickettsia rickettsii (Rickettsiales: Rickettsiaceae), the agent of Rocky Mountain spotted fever (RMSF). All parasitic stages of A. tonelliae were exposed to R. rickettsii by allowing each stage to feed on hosts inoculated with this pathogen. Thereafter, ticks were fed on uninfected hosts. All stages of A. tonelliae were able to acquire the R. rickettsii infection and maintain it by transstadial and transovarial transmission. When infected ticks fed on uninfected hosts, the hosts developed rickettsiosis disease. This study demonstrates the vectorial competence of A. tonelliae to transmit R. rickettsii. These results have epidemiological relevance because A. tonelliae is one of the tick species most likely to infest humans in Argentina, including in areas in which RMSF has been reported.

Dynamics of Exposure to Rickettsia parkeri in Cattle in the Paraná River Delta, Argentina.

Several cases of human rickettsiosis caused by Rickettsia parkeri were recently documented in the Paraná River delta of Argentina, where the tick vector is Amblyomma triste Koch. As cattle suffer recurrent A. triste infestations, they are at risk of becoming infected with R. parkeri Herein we investigated the dynamics of R. parkeri and its A. triste vector in a herd of beef cattle. Cattle were followed for 18 mo and samples were analyzed for the presence of antibodies against four Rickettsia species (R. parkeri, Rickettsia bellii, Rickettsia amblyommii, and Rickettsia felis) and also for the presence of rickettsial DNA. Additionally, cattle were examined for attached ticks and questing adult ticks were collected. All ticks were analyzed for the presence of rickettsial DNA. No evidence of rickettsemia was found in any cow, but the high R. parkeri infection rate documented in A. triste both questing in the study area (13.9%) and feeding on cattle (19.8%) and the identification of antibodies against R. parkeri antigen in 90% of cattle are evidence that infection is taking place. Altogether, our data suggest that A. triste ticks are capable of naturally exposing cattle to R. parkeri However, the progress of R. parkeri infection and its impact on bovine health and production remain to be established.

Altitudinal Assessment of Amblyomma aureolatum and Amblyomma ovale (Acari: Ixodidae), Vectors of Spotted Fever Group Rickettsiosis in the State of São Paulo, Brazil.

Amblyomma aureolatum (Pallas) and Amblyomma ovale Koch are common ectoparasites of domestic dogs in São Paulo state, southeastern Brazil, where they are vectors of distinct spotted fever group rickettsioses, one caused by Rickettsia rickettsii (transmitted by A. aureolatum), and the other caused by Rickettsia sp. strain Atlantic rainforest (transmitted by A. ovale). For the present study, we performed an altitudinal assessment of all 1992-2012 records of A. aureolatum and A. ovale retrieved from a tick collection. The municipalities with A. ovale records presented significantly (P < 0.05) lower altitude than the ones with A. aureolatum records; the higher the altitude, the lower the chances for the occurrence of A. ovale and the greater the likelihood for the occurrence of A. aureolatum. Regarding A. aureolatum, the chances of finding it in municipalities between 101 and 700 m are nine times higher than in municipalities at ≤ 100 m, or 31.5 times higher in municipalities above 700 m, when compared with municipalities at ≤ 100 m. The reverse was observed for A. ovale, which had its odds ratio diminishing at higher altitudes. These findings have a major role to public health, as A. aureolatum is associated with the transmission of a highly lethal spotted fever (caused by R. rickettsii), whereas A. ovale is associated with the transmission of a milder spotted fever (caused by Rickettsia sp. strain Atlantic rainforest, a R. parkeri-like agent), both in the state of São Paulo.

Experimental infection with Rickettsia rickettsii in an Amblyomma dubitatum tick colony, naturally infected by Rickettsia bellii.

Amblyomma dubitatum engorged females, naturally infected by Rickettsia bellii, were used to establish a laboratory colony. Larvae, nymphs, and adults were exposed to two strains of Rickettsia rickettsii by feeding on needle-inoculated guinea pigs, and thereafter reared on uninfected guinea pigs. After acquisition feeding, engorged larvae and nymphs molted to nymphs and adults, respectively, which were shown to be infected (confirming transstadial perpetuation), and were able to transmit both strains of R. rickettsii to uninfected animals, as demonstrated by clinical, serological, and molecular analyses. However, the larval, nymphal, and adult stages of A. dubitatum showed to be only partially susceptible to R. rickettsii infection, since in all cases, only part of the ticks became infected by this agent, after being exposed to rickettsemic animals. While transovarial transmission of R. rickettsii was inefficient in the A. dubitatum engorged females of the present study, 100% of these females passed R. bellii transovarially. Because it has been reported that a primary infection by a Rickettsia species would preclude transovarial transmission of a second Rickettsia species, it is likely that the ineffectiveness of A. dubitatum to perpetuate R. rickettsii by transovarial transmission was related to its primary infection by R. bellii; however, it could also be related to unknown factors inherent to A. dubitatum. The relevance of A. dubitatum as a natural vector of R. rickettsii to humans or animals is discussed.

Rickettsia amblyommii infecting Amblyomma auricularium ticks in Pernambuco, northeastern Brazil: isolation, transovarial transmission, and transstadial perpetuation.

This study investigated rickettsial infection in Amblyomma auricularium ticks from the state of Pernambuco, northeastern Brazil. An engorged female of A. auricularium collected from a skunk (Conepatus semistriatus) was sent alive to the laboratory, where the female was found through molecular analysis to be infected by Rickettsia amblyommii. This engorged female oviposited, and its offspring was reared through three consecutive generations, always using tick-naïve rabbits to feed the ticks. PCR performed on five egg pools, 10 larvae, 10 nymphs, and 10 adults of each of the three generations always yielded rickettsial DNA, indicating maintenance of rickettsial infection in the ticks by transstadial and transovarial passages. DNA sequences of random PCR products from eggs, larvae, nymphs, and adults were identified as R. amblyommii. All infested rabbits seroconverted to R. amblyommii antigens at the 21(st) day after infestation, indicating that larvae, nymphs, and adults transmitted R. amblyommii through parasitism. However, no infested rabbit presented fever or any clinical alteration during the experimental period. Rickettsiae were successfully isolated from the two A. auricularium females, and the isolates were established in Vero cell culture. Molecular characterization of the isolates confirmed R. amblyommii by sequencing partial gltA, ompA, and ompB genes. From another sample of 15 A. auricularium adult ticks collected from two armadillos (Euphractus sexcinctus), eight (53.3%) were infected by R. amblyommii. This study reports R. amblyommii infecting the tick A. auricularium for the first time. This is also the first report of rickettsia infecting ticks in the northeastern region of Brazil.

Red deer (Cervus elaphus) as a host for the cattle tick Rhipicephalus microplus (Acari: Ixodidae) in Yucatan, Mexico.

Rhipicephalus microplus is the most economically important cattle tick in the Mexican tropics. Wild ungulate species, including red deer (Cervus elaphus), are gaining popularity in diversified livestock ranching operations in Mexico. However, there is no information available on the susceptibility of red deer to infestation with the cattle tick, R. microplus, under hot, subhumid tropical conditions in Mexico. Biological data on R. microplus as an ectoparasite of cattle and red deer in a farm in the Mexican tropics are presented here. Ticks collected from red deer were identified as R. microplus (97 %) and Amblyomma cajennense (3 %), and tick species infesting cattle included R. microplus (95 %) and A. cajennense (5 %). Standard counts of R. microplus engorged females on red deer were 11 times higher than on cattle (428 ± 43 vs. 40 ± 18; p < 0.001). The reproductive efficiency index and larval hatching of R. microplus collected from cattle and red deer were similar (p > 0.05). Hemolymph samples of R. microplus collected from cattle were positive for Babesia spp. (10 %, 2/50) and all the samples from ticks infesting red deer were negative. Seventeen and ten percent of the blood samples from cattle and red deer were positive for Anaplasma marginale, respectively. The role of red deer as a host of R. microplus in Yucatan, Mexico and the importance of this host-parasite relationship relative to the epidemiology of R. microplus-borne diseases are discussed.

Wheat curl mite, Aceria tosichella, and transmitted viruses: an expanding pest complex affecting cereal crops.

The wheat curl mite (WCM), Aceria tosichella, and the plant viruses it transmits represent an invasive mite-virus complex that has affected cereal crops worldwide. The main damage caused by WCM comes from its ability to transmit and spread multiple damaging viruses to cereal crops, with Wheat streak mosaic virus (WSMV) and Wheat mosaic virus (WMoV) being the most important. Although WCM and transmitted viruses have been of concern to cereal growers and researchers for at least six decades, they continue to represent a challenge. In older affected areas, for example in North America, this mite-virus complex still has significant economic impact. In Australia and South America, where this problem has only emerged in the last decade, it represents a new threat to winter cereal production. The difficulties encountered in making progress towards managing WCM and its transmitted viruses stem from the complexity of the pathosystem. The most effective methods for minimizing losses from WCM transmitted viruses in cereal crops have previously focused on cultural and plant resistance methods. This paper brings together information on biological and ecological aspects of WCM, including its taxonomic status, occurrence, host plant range, damage symptoms and economic impact. Information about the main viruses transmitted by WCM is also included and the epidemiological relationships involved in this vectored complex of viruses are also addressed. Management strategies that have been directed at this mite-virus complex are presented, including plant resistance, its history, difficulties and advances. Current research perspectives to address this invasive mite-virus complex and minimize cereal crop losses worldwide are also discussed.

Experimental infection of the tick Amblyomma cajennense, Cayenne tick, with Rickettsia rickettsii, the agent of Rocky Mountain spotted fever.

In the laboratory, Amblyomma cajennense (Acari: Ixodidae) (Fabricius) larvae, nymphs and adults were exposed to Rickettsia rickettsii by feeding on needle-inoculated animals, and thereafter reared on uninfected guinea pigs or rabbits. Regardless of the tick stage that acquired the infection, subsequent tick stages were shown to be infected (confirming transstadial and transovarial transmissions) and were able to transmit R. rickettsii to uninfected animals, as demonstrated by serological and molecular analyses. However, the larval, nymphal and adult stages of A. cajennense were shown to be partially refractory to R. rickettsii infection, as in all cases, only part of the ticks became infected by this agent, after being exposed to rickettsemic animals. In addition, less than 50% of the infected engorged females transmitted rickettsiae transovarially, and when they did so, only part of the offspring became infected, indicating that vertical transmission alone is not enough to maintain R. rickettsii in A. cajennense for multiple generations. Finally, the R. rickettsii-infected tick groups had lower reproductive performance than the uninfected control group. Our results indicate that A. cajennense have a low efficiency to maintain R. rickettsii for successive generations, as R. rickettsii-infection rates should decline drastically throughout the successive tick generations.

Tick toxicosis in a dog bitten by Ornithodoros brasiliensis.

Ticks are hematophagous parasites of people and animals and are a public health hazard in several countries. They are vectors of infectious diseases; in addition, the bite of some ticks, mainly from the Ornithodoros genus, may lead to local lesions and systemic illness, referred to as tick toxicosis. In this report, we describe a dog bitten by Ornithodoros brasiliensis, popularly known as the mouro tick. The main clinical findings were disseminated skin rash, pruritus, mucosal hyperemia, lethargy, and fever. Laboratory abnormalities 48 hours after the bites occurred included mild nonregenerative anemia, eosinophilia, basophilia, increased serum creatine kinase activity, increased serum C-reactive protein concentration, and prolonged coagulation times. Tick-borne pathogens were not detected by PCR analysis or serologic testing, supporting the diagnosis of a noninfectious syndrome due to tick bite, compatible with tick toxicosis.

New Spiroplasma in parasitic Leptus mites and their Agathemera walking stick hosts from Argentina.

Here we report the presence of Spiroplasma 16S rRNA in populations of two parasitic Leptus mites (Leptus sayi; Leptus lomani) and their Agathemera walking stick hosts. In walking sticks Spiroplasmas were detected in the gut, as well as muscle-tissues, but not in eggs. Throughout Argentina 15.4% of L. sayi populations and 14.3% of L. lomani populations surveyed screened positive for Spiroplasma. Phylogenetic analyses (ML, BCMC) place all sequences within the Ixodetis group. Most sequences form a well-supported sister subclade to the rest of Ixodetis. We briefly discuss the role of Leptus mites in the natural transmission of Spiroplasma.

Experimental infection of the rabbit tick, Haemaphysalis leporispalustris, with the bacterium Rickettsia rickettsii, and comparative biology of infected and uninfected tick lineages.

The present study consisted of two experiments that evaluated experimental infections of Haemaphysalis leporispalustris ticks by a Brazilian strain of Rickettsia rickettsii, and their effect on tick biology. In experiment I, ticks were exposed to R. rickettsii during the larval, nymphal or adult stages by feeding on rabbits (Oryctolagus cuniculus) needle-inoculated with R. rickettsii, and thereafter reared on uninfected rabbits for the entire next tick generation. Regardless of the tick stage that acquired the infection, all subsequent tick stages were shown to be infected by PCR (infection rates varying from 1.3 to 41.7%), and were able to transmit R. rickettsii to uninfected rabbits, as demonstrated by rabbit seroconversion, guinea pig inoculation with rabbit blood, and PCR on rabbit blood. In Experiment II, ticks were exposed to R. rickettsii during the larval stage by feeding on rabbits co-infested with R. rickettsii-infected adult ticks, and thereafter reared on uninfected rabbits until the next generation of larvae. Again, all subsequent tick stages were shown to be infected by PCR (infection rates varying from 3.0 to 40.0%), and were able to transmit R. rickettsii to uninfected rabbits. Thus, it was demonstrated that larvae, nymphs, and adults of H. leporispalustris were able to acquire and maintain the R. rickettsii infection by transstadial and transovarial transmissions within the tick population, with active transmission of the bacterium to susceptible rabbits by all parasitic stages. Analyses of biological parameters of uninfected and R. rickettsii-infected tick lineages were performed in order to evaluate possible deleterious effects of R. rickettsii to the infected tick lineages. Surprisingly, all but one of the four R. rickettsii-experimental groups of the present study showed overall better biological performance than their sibling uninfected control ticks. Results of the present study showed that H. leporispalustris could support infection by a high virulent strain of R. rickettsii for at least two generations, in which infected tick lineages tended to have better performance than uninfected ticks. Our results support a possible role of H. leporispalustris in the enzootic maintenance of R. rickettsii in Latin America, as previously suggested by earlier works.

Reproductive performance of the mite Brevipalpus phoenicis (Geijskes, 1939) on citrus and coffee, using life table parameters.

The flat-mite Brevipalpus phoenicis (Geijskes, 1939) (Acari: Tenuipalpidae) is considered important in citrus (Citrus spp.) and coffee plants (Coffea spp.) in Brazil, and is known as the leprosis and coffee ring spot mite, as being a vector of the Citrus Leprosis Rhabdovirus - CitLV and Coffee Ring Spot Virus - CoRSV. The objective of this work is to find out about the reproductive success of B. phoenicis on citric fruits and coffee leaves by fertility life table parameters and its biology. The experiments were carried out in laboratory conditions at 25 +/- 2 degrees C, 70 +/- 10% of relative humidity and 14 h of photophase. The lengths of embryonic and post-embryonic periods were different due to the host where the mite was reared. B. phoenicis showed better development and higher survival and fecundity in citric fruits than coffee leaves. The intrinsic rate of the population increase (r(m)) was 0.128 and 0.090 - females/female/day on citric fruits and coffee leaves, respectively. The citric fruits were more appropriate for the development of B. phoenicis than coffee leaves.