Detection of Leishmania (Leishmania) infantum RNA in fleas and ticks collected from naturally infected dogs

The occurrence of the insect vector (sand flies) with low rates of Leishmania infection, as well as autochthonous transmission in the absence of the natural vector in dogs, have been reported. These unexpected data suggest a hypothesis of other arthropods as a possible way of Leishmania transmission. The prevalence of Leishmania (Leishmania) infantum in fleas and ticks collected from dogs with canine visceral leishmaniasis (CVL), as well as parasite viability, were evaluated herein. The presence of L. (L.) infantum was assayed by PCR and ELISA in ectoparasites and biological samples from 73 dogs living in a Brazilian endemic area. As the occurrence of Leishmania DNA in ticks and fleas is expected given their blood-feeding habits, we next investigated whether parasites can remain viable inside ticks. PCR and ELISA confirmed that 83% of the dogs had CVL. Fleas and ticks (nymphs, male and female adults) were collected in 55% and 63% of the 73 dogs, respectively. Out of the 60 dogs with CVL, 80% harbored ectoparasites infected with L. (L.) infantum. The infection rates of the ectoparasites were 23% and 50% for fleas and ticks, respectively. The RNA analysis of the extract from ticks left in laboratory conditions during 7 to 10 days after removal from CVL dogs showed that parasites were alive. In addition, live parasites were also detected inside adult ticks recently molted in laboratory conditions. These findings indicate a higher infection rate of L. (L.) infantum in ticks and fleas, but they do not conclusively demonstrate whether these ticks can act as vectors of CVL, despite the fact that their rates were higher than those previously described in Lutzomyia longipalpis. The presence of viable L. (L.) infantum in ticks suggests the possible importance of dog ectoparasites in CVL dissemination.     

Genetic diversity of Borrelia burgdorferi sensu lato in ticks from mainland Portugal

To date Borrelia lusitaniae is the only genospecies of Borrelia burgdorferi sensu lato isolated from Ixodes ricinus ticks collected in Portugal and Tunisia. This suggests that the genospecies diversity of B. burgdorferi sensu lato decreases toward the southwestern margin of its Old World subtropical range. In order to further explore the genetic diversity of B. burgdorferi sensu lato from this region, 55 I. ricinus and 27 Hyalomma marginatum questing adults, collected during the spring of 1998 from a sylvatic habitat south of Lisbon, Portugal, were analyzed. Infection prevalences of 75% in I. ricinus ticks and 7% in H. marginatum ticks were detected by a nested PCR that targets the rrf (5S)-rrl (23S) spacer of B. burgdorferi sensu lato. Restriction fragment length polymorphism (RFLP) analysis of the I. ricinus-derived amplicons showed that the sequences in the majority of samples were similar to those of B. lusitaniae type strains (76% for strain PotiB1, 5% for strain PotiB3). Two novel RFLP patterns were obtained from 12% of the samples. The remaining 7% of samples gave mixed RFLP patterns. Phylogenetic analysis of rrf-rrl spacer sequences revealed a diverse population of B. lusitaniae in questing adult I. ricinus ticks (the sequences did not cluster with those of any other genospecies). This population consisted of 10 distinct sequence types, suggesting that multiple strains of B. lusitaniae were present in the local I. ricinus population. We hypothesize that B. lusitaniae has a narrow ecological niche that involves host species restricted to the Mediterranean Basin.     

Transmission of bacterial agents from lone star ticks to white-tailed deer

Amblyomma americanum (L.), the lone star tick, is an aggressive ixodid tick that has been implicated as a vector for several bacteria. Among these bacteria are the disease agents Ehrlichia chaffeensis and Ehrlichia ewingii, and the putative disease agent "Borrelia lonestari." The hypothesis in this study was that wild lone star ticks from northeastern Georgia are capable of transmitting all three agents to white-tailed deer, Odocoileus virginianus, a known reservoir host for E. chaffeensis. In this study, transmission of all three agents from wild caught lone star ticks to captive reared white-tailed deer was demonstrated by polymerase chain reaction (PCR), culture, or serology. Two of three deer showed evidence of E. chaffeensis and E. ewingii infection by polymerase chain reaction assay; all three deer showed evidence of B. lonestari by PCR assay. E. chaffeensis was isolated in culture from both PCR-positive deer on multiple days. All three deer seroconverted to E. chaffeensis, whereas one deer seroconverted to B. lonestari. This study supports the role of lone star ticks and white-tailed deer as a vector and reservoir host for E. chaffeensis and E. ewingii and suggests for the first time, transmission of B. lonestari from lone star ticks to white-tailed deer.     

A century of typhus, lice and Rickettsia

At the beginning of the 20th century, it was discovered at the Pasteur Institute in Tunis that epidemic typhus is transmitted by the human body louse. The complete genome sequence of its causative agent, Rickettsia prowazekii, was determined at Uppsala University in Sweden at the end of the century. In this mini-review, we discuss insights gained from the genome sequence of this fascinating and deadly organism.     

Genetic diversity of subgroup 1 ilarviruses from eastern Australia

This is the first report of the genetic diversity within ilarvirus subgroup 1 from eastern Australia. It supports the separation of tobacco streak virus (TSV) strains from parthenium (Parthenium hysterophorus) and crownbeard (Verbescina encelioides) based on serology and host specificity. It has confirmed one previously described strain of TSV as a member of the species Strawberry necrotic shock virus and another as a new subgroup 1 ilarvirus, ageratum latent virus (AgLV), from Ageratum houstonianum. A multiplex RT-PCR showed that the genetically distinct strains of TSV and AgLV were commonly found in symptomless infections in virus-specific alternative weed hosts growing over a wide geographical range in eastern Australia. TSV has been one of the most damaging viruses in Australian oilseed and pulse crops in recent years, and this study has provided the taxonomic knowledge essential for the development of control programs for these viruses.     

A survey of ticks (Acari:Ixodidae) on cattle, sheep and goats in the Dohuk Governorate, Iraq

A survey on hard ticks affecting cattle, sheep, and goats was done in Dohuk Governorate from March 2005 until February 2006 in three areas (Dohuk surrounding area, Barwary Balla near Turkish border, and Eqre). The species collected from cattle were Hyalomma anatolicum anatolicum and Hyalomma anatolicum marginatum, while the species collected from sheep and goats were Rhipicephalus bursa, Rhipicephalus turanicus, Haemaphysalis parva, and Hyalomma spp. The occurrences of the ticks in the three areas were different; in Dohuk surrounding area they occured at the beginning of March and disappeared in the middle of April, while in the Barwary area the ticks occured at the end of March and disappeared at the end of May. In Eqre, the peaks of infestation occurred after harvesting of cereals in the middle of June until end of July.     

Genotypic diversity of Francisella tularensis infecting Dermacentor variabilis ticks on Martha's Vineyard, Massachusetts

Martha's Vineyard, Mass., has been the site of two outbreaks of tularemia (1978 and 2000). Although most patients from both outbreaks presented with pneumonic disease and although aerosol transmission has been suggested, the bite of a dog tick and exposure to rabbits remain the only proven modes of transmission. The factors that precipitated the tularemia outbreaks or the proximal determinants of human risk remain undescribed. We sought to test the hypothesis that the ongoing outbreak is due to a recent introduction event as opposed to amplification of a cryptic enzootic cycle. From 2001-2003, we collected 4,246 dog ticks and tested them in pools for evidence of tularemia by PCR. We then measured the genetic diversity of Francisella tularensis by using multiple-locus variable-number tandem repeat analysis. The prevalence of F. tularensis in dog ticks averaged 0.7%. From 29 positive pools, we identified 10 unique genotypes, which was an unexpectedly large degree of diversity (Simpson's index = 0.86). This degree of genetic diversity is inconsistent with a recent introduction event. We conclude that there has been long-standing enzootic transmission of tularemia on the island.     

Source of host blood affects prevalence of infection and bacterial loads of Yersinia pestis in fleas

Yersinia pestis, the etiological agent of plague, is transmitted by multiple flea species. Previous studies have reported wide variability in transmission efficiency among competent vectors. However, it is unclear to what extent such variation is explained by methodological differences among studies. To optimize an artificial feeding system where fleas are infected with controlled numbers of Y. pestis under standardized laboratory conditions that could be used to systematically compare vector efficiency, we sought to test the effect of host bloodmeal source on (1) the flea's ability to remain infected with Y. pestis and (2) bacterial loads in fleas. Here, we demonstrate that both prevalence of infection with a virulent strain of Y. pestis (CO96-3188) and bacterial loads in rock squirrel fleas (Oropsylla montana) are affected by host-associated blood factors. The generality of this observation was confirmed by repeating the study using the rat flea (Xenopsylla cheopis) and a commonly used avirulent laboratory strain of Y. pestis (A1122). Implications of the results for rate of spread of Y. pestis in naturally infected host populations are discussed.     

Genetic diversity of Burkholderia pseudomallei isolates in Australia

Melioidosis is caused by the gram-negative saprophytic bacterium Burkholderia pseudomallei, which is endemic to southeast Asia and northern Australia. We have previously found evidence of geographic localization of strains based on multilocus sequence typing (MLST). In this study, we examined the diversity of 277 isolates from northern Australia, which were resolved into 159 different sequence types. No sequence types were common to both Queensland and the Northern Territory, and there was significant differentiation between the alleles present in the two regions. The considerable diversity in sequence types contrasts with the limited diversity of alleles at MLST loci, supporting previous work suggesting a high rate of recombination relative to mutation in B. pseudomallei, where new sequence types are primarily generated by reassortment of existing alleles.     

Prevalence and genetic diversity of pneumococcal serogroup 6 in Australia

The prevalence of the newly discovered pneumococcal serotype 6C has increased in some countries since the introduction of seven-valent conjugate pneumococcal vaccine (PCV7). The distribution of invasive serogroup 6 serotypes, in Australia, including 6C and 6D, has not been reported previously. During the period 1999 to 2008, 6097 isolates were referred to the New South Wales Pneumococcal Reference Laboratory for serotyping. Of these, 847 were identified by Quellung reaction as belonging to serogroup 6 and 702 were available for further study. Serotypes were determined by serotype-specific PCR as follows: 6A, 197 (28.1%); 6B, 452 (64.4%); 6C, 52 (7.4%) and one 6D. The average numbers of invasive serogroup 6 isolates, per annum, fell from 62.2 before (2000– 2005) to 49.7 after (2006–2008) the introduction of PCV7. The proportions of invasive 6B fell (from 72.4% to 47.3%, p 0.03), those of 6C rose (from 3.3% to 17%, p 0.02) significantly and those of 6A remained fairly constant (24.3% vs 27%, p 0.69) between the two periods. All 6C and 6D and selected 6A and 6B isolates were further characterized by multilocus sequence typing and sequence analysis of cps genes cpsA-cpsB (wzg-wzh) and wchA-wciN^beta-wciO, wciP. Results showed considerable diversity within serotype 6C, apparently as a result of both mutation and recombination. Sequence typing indicates that, in Australia, 6C has been largely derived from 6A. The genetic diversity and rapid increase in incidence of serotype 6C causing invasive pneumococcal disease has potential implications for vaccine efficacy.     

Extract of the seeds of the plant Vitex agnus castus proven to be highly efficacious as a repellent against ticks, fleas, mosquitoes and biting flies

About 70 plant extracts were tested for their ability to repel the attacks of blood-sucking arthropods. It was found that a CO₂ extract of the seeds of the Mediterranean plant Vitex agnus castus (monks pepper) can be used as a spray to keep away especially Ixodes ricinus and Rhipicephalus sanguineus ticks from animals and humans for at least 6 h. In addition mosquitoes, biting flies and fleas are also repelled for about 6 h.Extract of the seeds of the plant Vitex agnus castus is available as: Anticks—Trademark of Gimborn, Emmerich, Germany; Viticks-Cool—Trademark of Alpha-Biocare, Düsseldorf, Germany; Viticks-Cool-Plus with additional etheric oils—Trademark of Alpha-Biocare, Düsseldorf, Germany