Emergence of the ehrlichioses as human health problems

Molecular and serological detection of Ehrlichia spp. in cats on São Luís Island, Maranhão, Brazil

Ehrlichiosis is a tick-borne disease that affects both humans and animals. The few existing reports on ehrlichiosis in Brazilian cats have been based on observation of morulae in leukocytes and, more recently, on molecular detection of Ehrlichia sp. In this study, we assessed occurrences of Ehrlichia sp. in the blood of 200 domestic cats in São Luís, Maranhão. Of the 200 animals tested, 11 (5.5%) were seropositive for Ehrlichia sp. and two (1%) were positive for Ehrlichia sp. in PCR. We also performed DNA sequence alignment to establish the identity of the parasite species infecting these animals, using the gene 16S rRNA. One cat presented infection with Ehrlichia sp. with 98% identity with E. canis, and another cat infected with Ehrlichia sp. showed 97% identity with E. chaffeensis. This is the first study on molecular detection of Ehrlichia sp. among domestic cats in São Luís, Maranhão.

Neorickettsial endosymbionts of the digenea: diversity, transmission and distribution

Digeneans are endoparasitic flatworms with complex life cycles and distinct life stages that parasitize different host species. Some digenean species harbour bacterial endosymbionts known as Neorickettsia (Order Rickettsiales, Family Anaplasmataceae). Neorickettsia occur in all life stages and are maintained by vertical transmission. Far from benign however, Neorickettsia may also be transmitted horizontally by digenean parasites to their vertebrate definitive hosts. Once inside, Neorickettsia can infect macrophages and other cell types. In some vertebrate species (e.g. dogs, horses and humans), neorickettsial infections cause severe disease. Taken from a mostly parasitological perspective, this article summarizes our current knowledge on the transmission ecology of neorickettsiae, both for pathogenic species and for neorickettsiae of unknown pathogenicity. In addition, we discuss the diversity, phylogeny and geographical distribution of neorickettsiae, as well as their possible evolutionary associations with various groups of digeneans. Our understanding of neorickettsiae is at an early stage and there are undoubtedly many more neorickettsial endosymbioses with digeneans waiting to be discovered. Because neorickettsiae can infect vertebrates, it is particularly important to examine digenean species that regularly infect humans. Rapid advances in molecular tools and their application towards bacterial identification bode well for our future progress in understanding the biology of Neorickettsia.

The biological basis of severe outcomes in Anaplasma phagocytophilum infection

Anaplasma phagocytophilum causes granulocytic anaplasmosis, an acute disease in humans that is also often subclinical. However, 36% are hospitalized, 7% need intensive care, and the case fatality rate is 0.6%. The biological basis for severe disease is not understood. Despite A. phagocytophilum's mechanisms to subvert neutrophil antimicrobial responses, whether these mechanisms lead to disease is unclear. In animals, inflammatory lesions track with IFNγ and IL-10 expression and infection of Ifng(-/-) mice leads to increased pathogen load but inhibition of inflammation. Suppression of STAT signaling in horses impacts IL-10 and IFN-γ expression, and also suppresses disease severity. Similar inhibition of inflammation with infection of NKT-deficient mice suggests that innate immune responses are key for disease. With severe disease, tissues can demonstrate hemophagocytosis, and measures of macrophage activation/hemophagocytic syndromes (MAS/HPS) support the concept of human granulocytic anaplasmosis as an immunopathologic disease. MAS/HPS are related to defective cytotoxic lymphocytes that ordinarily diminish inflammation. Pilot studies in mice show cytotoxic lymphocyte activation with A. phagocytophilum infection, yet suppression of cytotoxic responses from both NKT and CD8 cells, consistent with the development of MAS/HPS. Whether severity relates to microbial factors or genetically determined diversity in human immune and inflammatory response needs more investigation.

Neorickettsia helminthoeca and salmon poisoning disease: a review

Neorickettsia helminthoeca is an obligate intra-cytoplasmic bacterium that causes salmon poisoning disease (SPD), an acute, febrile, fatal disease of dogs. The complex life-cycle of this pathogen involves stages in an intestinal fluke (Nanophyetus salmincola), a river snail (Oxytrema silicula), in fish, and in fish-eating mammals. This complexity has created confusion with respect to the various bacterial and parasitic infections associated with the disease and its significance in dogs in specific geographical locations has likely to have previously been under-estimated. This paper addresses the history, taxonomy, microbiology of N. helminthoeca and summarises the pathogenesis, clinical signs and pathological features associated with infection. Furthermore, the biological cycles, treatment, control, and both public and veterinary health impacts associated with this pathogen and the intestinal fluke N. salmincola are discussed.

Ehrlichia species, probable emerging human pathogens in sub-Saharan Africa: environmental exacerbation

Ehrlichiae are obligate intracellular Gram-negative tick-borne bacteria that are responsible for life-threatening emerging human zoonoses and diseases of veterinary importance worldwide, collectively called ehrlichioses. The genus Ehrlichia consists of five recognized species, including E. canis, E. chaffeensis, E. ewingii, E. muris, and E. ruminantium. The recent discoveries of Ehrlichia species in new areas and of tick species that were previously thought to be uninfected by these agents have suggested that these agents may have wider distribution than originally thought. Environmental factors like temperature, migration, control failure, and host population have been known to exacerbate the spread of Ehrlichia species. Human cases of moderate to severe disease caused by E. chaffeensis have been reported mainly in North America. In this article, we present an overview of ehrlichiae as emerging pathogens in sub-Saharan Africa, where E. ruminantium, the causative agent of heartwater, a disease of domestic and wild ruminants, is most established. Molecular evidence indicates that E. ruminantium may be an emerging pathogen of a life-threatening human disease. Ehrlichia ruminantium is considered an agricultural biothreat, with several strains reported throughout sub-Saharan Africa, where the infection is considered endemic. Understanding the diversity of E. ruminantium and other Ehrlichia species from all geographically distinct areas of sub-Saharan Africa may enhance our knowledge of the pathogenesis and epidemiology of these pathogens.

Tickborne infections in the southern United States

Established and emerging tickborne infections are significant causes of human illness in the southern United States. Rocky Mountain spotted fever, human monocytic ehrlichiosis, human ewingii ehrlichiosis and tularemia are known pathogens in this geographic distribution. Rickettsia parkeri and novel ehrlichioses are more recently described tickborne infections reviewed in this article. An understanding of the tick vectors, pathogenesis, epidemiology, clinical presentation, diagnosis and treatment is useful for the clinician treating patients potentially infected with any of these pathogens. Prevention measures, the optimal method for removing an attached tick and current and future vaccine development conclude this review.

Molecular and clinical evidence of Ehrlichia chaffeensis infection in Cameroonian patients with undifferentiated febrile illness

In the U.S.A., human monocytotropic ehrlichiosis (HME) caused by Ehrlichia chaffeensis is an emerging tick-transmitted zoonosis. In Cameroon, where E. canis, E. chaffeensis and E. ewingii have recently been detected in dogs and/or ticks (Rhipicephalus sanguineus), the potential exists for human infections. Patients from the coastal region of Cameroon who had acute fevers of unknown aetiology were therefore checked for ehrlichial infection, using a real-time PCR that amplifies part of a genus-specific gene (dsb) that codes for a disulphide-bond formation protein. Ehrlichial blood was detected in the peripheral blood from 12 (10%) of the 118 patients investigated by PCR. When the 12 amplicons from the positive cases were sequenced, they were found to be identical to each other and to the corresponding dsb sequence of an Arkansas strain of E. chaffeensis. The 12 patients who were PCR-positive for E. chaffeensis suffered from fever (100%), headache (67%), myalgia (42%), arthralgia (58%), pulmonary involvement (17%) and/or a diffuse rash (17%).

Strains of Ehrlichia chaffeensis in southern Indiana, Kentucky, Mississippi, and North Carolina

Rates of infection of Amblyomma americanum (L.) by Ehrlichia chaffeensis were compared in 100 ticks collected from sites in each of four states: Indiana, North Carolina, Kentucky, and Mississippi. The overall infection rates were similar among sites, ranging from 1 to 4%. Because pathogenic differences may exist between E. chaffeensis strains, nested polymerase chain reaction (PCR) amplification of the variable-length PCR target (VLPT), and sequencing of the amplicons were performed to differentiate between strains. The most common infecting strains at all sites exhibited a repeat profile of 1,2,3,4 (corresponding to the Arkansas/Jax/Osceola and Liberty strains). To determine whether the minimum infection rates (MIRs) or the most common infecting strain were changing over time in southern Indiana sites, 2765 ticks from six counties in 2000 and 837 ticks from seven counties in 2004 also were examined in pools of five ticks per pool. The MIRs for 2000 and 2004 were 3.5 and 4.2% respectively, suggesting that the overall MIRs remained low. At two sites, in Pike and Harrison counties, however, infection rates more than doubled from 2000 to 2004 (7 to 16% and 0.3 to 2.7% respectively). Across all sites, the most common infecting strains (Arkansas/Jax/Osceola and Liberty) did not significantly change (68% in 2000; 79% in 2004).

The natural history of Anaplasma phagocytophilum

Anaplasma phagocytophilum is the recently designated name replacing three species of granulocytic bacteria, Ehrlichia phagocytophila, Ehrlichia equi and the agent of human granulocytic ehrlichiosis, after the recent reorganization of the families Rickettsiaceae and Anaplasmataceae in the order Rickettsiales. Tick-borne fever (TBF), which is caused by the prototype of A. phagocytophilum, was first described in 1932 in Scotland. A similar disease caused by a related granulocytic agent was first described in horses in the USA in 1969; this was followed by the description of two distinct granulocytic agents causing similar diseases in dogs in the USA in 1971 and 1982. Until the discovery of human granulocytic anaplasmosis (HGA) in the USA in 1994, these organisms were thought to be distinct species of bacteria infecting specific domestic animals and free-living reservoirs. It is now widely accepted that the agents affecting different animal hosts are variants of the same Gram-negative obligatory intracellular bacterium, which is transmitted by hard ticks belonging to the Ixodes persulcatus complex. One of its fascinating features is that it infects and actively grows in neutrophils by employing an array of mechanisms to subvert their bactericidal activity. It is also able to survive within an apparently immune host by employing a complex mechanism of antigenic variation. Ruminants with TBF and humans with HGA develop severe febrile reaction, bacteraemia and leukopenia due to neutropenia, lymphocytopenia and thrombocytopenia within a week of exposure to a tick bite. Because of the severe haematological disorders lasting for several days and other adverse effects on the host's immune functions, infected animals and humans are more susceptible to other infections.

Host surveys, ixodid tick biology and transmission scenarios as related to the tick-borne pathogen, Ehrlichia canis

The ehrlichioses have been subject to increasing interest from veterinary and public health perspectives, but experimental studies of these diseases and their etiologic agents can be challenging. Ehrlichia canis, the primary etiologic agent of canine monocytic ehrlichiosis, is relatively well characterized and offers unique advantages and opportunities to study interactions between a monocytotropic pathogen and both its vertebrate and invertebrate hosts. Historically, advances in tick-borne disease control strategies have typically followed explication of tick-pathogen-vertebrate interactions, thus it is reasonable to expect novel, more sustainable approaches to control of these diseases as the transmission of their associated infections are investigated at the molecular through ecological levels. Better understanding of the interactions between E. canis and its canine and tick hosts would also elucidate similar interactions for other Ehrlichia species as well as the potential roles of canine sentinels, reservoirs and models of tick-borne zoonoses. This article summarizes natural exposure studies and experimental investigations of E. canis in the context of what is understood about biological vectors of tick-borne Anaplasmataceae.

Acute granulocytic ehrlichiosis in a rottweiler

Acute granulocytic ehrlichiosis was identified in a 6-year-old rottweiler that was presented for possible pancreatitis. Intracytoplasmic inclusion bodies were identified within neutrophils on a peripheral blood smear. Serology was ineffective in identifying the disease in the acute state. The diagnosis and identification of the organism were confirmed by polymerase chain reaction (PCR) and deoxyribonucleic acid (DNA) sequencing. Based on elevations in amylase and lipase and the presence of right cranial-quadrant abdominal pain, concurrent pancreatitis was diagnosed. It is unknown if there was any association between the acute granulocytic ehrlichiosis and the pancreatitis. The dog recovered well following doxycycline therapy.

Evolution and function of tandem repeats in the major surface protein 1a of the ehrlichial pathogenAnaplasma marginale

The major surface protein (MSP) 1a of the ehrlichial cattle pathogenAnaplasma marginale, encoded by the single-copy genemsp1α, has been shown to have a neutralization-sensitive epitope and to be an adhesin for bovine erythrocytes and tick cells.msp1αhas been found to be a stable genetic marker for the identification of geographic isolates ofA. marginalethroughout development in acutely and persistently infected cattle and in ticks. The molecular weight of MSP1a varies among geographic isolates ofA. marginalebecause of a varying number of tandemly repeated peptides of 28–29 amino acids. Variation in the sequence of the tandem repeats occurs within and among isolates, and may have resulted from evolutionary pressures exerted by ligand–receptor and host–parasite interactions. These repeated sequences include markers for tick transmissibility that may be important in the identification of ehrlichial pathogens because they may influence control strategies and the design of subunit vaccines.

Immune evasion and immunosuppression by Anaplasma phagocytophilum, the causative agent of tick-borne fever of ruminants and human granulocytic anaplasmosis

Anaplasma phagocytophilum, the causative agent of tick-borne fever (TBF) in sheep and cattle and human granulocytic anaplasmosis, has the unique ability to infect and multiply within neutrophils, eosinophils and monocytes, cells at the frontline of the immune system. Infection with A. phagocytophilum is also characterized by severe leukopenia due to lymphocytopenia, neutropenia and thrombocytopenia lasting for several days. By itself TBF does not cause high mortality rates but infected animals are more susceptible to other secondary infections, pregnant animals may abort and there is a severe reduction in milk yield in dairy cattle. The susceptibility to secondary infections can be attributed to the leukopenia that accompanies the disease and the organism's adverse effects on lymphocyte and neutrophil functions. One of its fascinating features is that it infects and actively grows in neutrophils by employing an array of mechanisms to subvert their bactericidal activity. These include its ability to inhibit phagosome-lysosome fusion, to suppress respiratory burst and to delay the apoptotic death of neutrophils. It is also able to survive within an apparently immune host by employing a complex mechanism of antigenic variation.

Emerging Tick-Borne Disease in African Vipers Caused by aCowdria-Like Organism

Heartwater is a tick-borne infectious disease caused by the rickettsial organism Cowdria ruminantium, currently Ehrlichia ruminantium. It poses an imminent threat to the Western Hemisphere, where it could cause mortality in cattle and other ruminant livestock in excess of 70%. It has been reported in the Caribbean; and its vector, Amblyomma sparsum, has been found on imported African spurred tortoises (Geochelone sulcata) and leopard tortoises (Geochelone pardalis) in southern Florida in the United States, leading to an importation ban on these reptiles. Symptoms have not been previously reported in reptiles. Here, we report peracute and acute deaths in African vipers imported from Africa through Florida. Signs included vomiting mucoid fluid, diarrhea, emaciation, convulsions, and death. Postmortem showed few gross lesions. The most consistent peracute and acute lesions were the pulmonary lesions and pericarditis with considerable bloody fluid in the pericardial sac (hydropericardium). These lesions strongly resembled the lesions of heartwater and a coccobacillus of less than 1-micron diameter was isolated in viper cell culture. The outbreak was brought to a halt by tick control and treatment of all exposed snakes with tetracycline. This isolation, tetracycline sensitivity, clinical signs, preliminary results with polymerase chain reaction of pCS20 ORF, and the viper preference of the disease may indicate a Cowdria-related attenuated species that has adapted to infect reptiles or an emerging new form of this group of microbes.

Detection of Ehrlichia chaffeensis in Brazilian marsh deer (Blastocerus dichotomus)

Ehrlichia chaffeensis was detected for the first time in blood samples from Brazilian marsh deers (Blastocerus dichotomus) captured in the marshes of Parana River in Southeast Brazil in 1998. Seven EDTA-blood samples from deers were analyzed by PCR and nested PCR for presence of Ehrlichia chaffeensis, Ehrlichia ewingii, Ehrlichia canis, Neoriickettsia risticii, Anaplasma phagocytophilum and Anaplasma marginale. Three samples showed positive reactions for E. chaffeensis and Anaplasma marginale. None contained detectable A. phagocytophilum, E. ewingii, E. canis or Neorickettsia risticii DNA. In Brazil, the wild marsh deer may be a natural reservoir of the agents that cause human monocytotropic ehrlichiosis and ruminant erythrocytic anaplasmosis.

Human granulocytic anaplasmosis and Anaplasma phagocytophilum

Human granulocytic anaplasmosis is a tickborne rickettsial infection of neutrophils caused by Anaplasma phagocytophilum. The human disease was first identified in 1990, although the pathogen was defined as a veterinary agent in 1932. Since 1990, US cases have markedly increased, and infections are now recognized in Europe. A high international seroprevalence suggests infection is widespread but unrecognized. The niche for A. phagocytophilum, the neutrophil, indicates that the pathogen has unique adaptations and pathogenetic mechanisms. Intensive study has demonstrated interactions with host-cell signal transduction and possibly eukaryotic transcription. This interaction leads to permutations of neutrophil function and could permit immunopathologic changes, severe disease, and opportunistic infections. More study is needed to define the immunology and pathogenetic mechanisms and to understand why severe disease develops in some persons and why some animals become long-term permissive reservoir hosts.

Comparative study of Anaplasma parasites in tick carrying buffaloes and cattle

A comparative study on the prevalence of Anaplasma parasite was conducted on ticks carrying buffaloes and cattle. Five hundred blood samples of both animals (250 of each) were collected during February, March and April. Thin blood smears on glass slides were made, fixed in 100% methyl alcohol and examined. Microscopic examination revealed that 205 (41%) animals had Anaplasma parasites, out of which 89, 44 and 72 animals had Anaplasma marginale, Anaplasma centrale and mixed infection respectively. Infected buffaloes and cattle were 75 and 130 respectively. The infection in female was 53 and 92 in buffaloes and cattle respectively. Twenty-two and 92 blood samples of male were found positive in buffaloes and cattle respectively. Comparative study revealed that the cattle were 26.82% more susceptible than buffaloes. The parasite prevailing percentage in female of both animals was slightly higher than that of the male. This investigation was aimed at studying the comparative prevalence of Anaplasma parasite in tick carrying buffaloes and cattle.

A real-time combined polymerase chain reaction assay for the rapid detection and differentiation of Anaplasma phagocytophilum, Ehrlichia chaffeensis, and Ehrlichia ewingii

A rapid real-time polymerase chain reaction (PCR) assay capable of the simultaneous detection and differentiation of Anaplasma phagocytophilum, Ehrlichia chaffeensis, and Ehrlichia ewingii was developed using the LightCyclertrade mark instrument (Roche Applied Sciences, Indianapolis, IN). The assay targets the operon groEL of the heat shock protein. Base pair mismatches in amplified DNA in regions of detection probe hybridization allowed organism differentiation by melting curve analysis. The analytical sensitivity was at least 10 copies per reaction. DNA extracts from 59 specimens previously confirmed positive for A. phagocytophilum (n = 37), E. chaffeensis (n = 19), or E. ewingii (n = 3) were used to evaluate the assay. All of the specimens positive for 1 of the 3 organisms by conventional PCR were likewise positive by the LightCycler method. Sensitivity and specificity were at least 100% compared with conventional PCR. This assay provides a rapid method for the detection and differentiation of the causative agents of human ehrlichiosis in the United States.

Transstadial and intrastadial experimental transmission of Ehrlichia canis by male Rhipicephalus sanguineus

The acquisition and transmission of rickettsial pathogens by different tick developmental stages has important epidemiological implications. The purpose of this study was to determine if male Rhipicephalus sanguineus can experimentally acquire and transmit Ehrlichia canis in the absence of female ticks. Two trials were performed where nymphal and male R. sanguineus were simultaneously acquisition fed on the same infected donor hosts, and transstadially or intrastadially exposed male ticks were fed on separate pathogen-free dogs as a test for transmission. A single-step p30-based PCR assay was used to test canine and tick hosts for E. canis infections before and after tick feeding. E. canis was detected after either intrastadial or transstadial passage in male ticks, the organism remained detectable in both tick groups after transmission feeding, and both tick groups transmitted the rickettsia to susceptible dogs. Infection of dogs via tick feeding resulted in milder clinical signs and lower antibody titers than intravenous inoculation of carrier blood, but further investigation is needed to understand the mechanisms responsible for this observation. These results demonstrate that male R. sanguineus can take multiple feedings, and that they can both acquire and transmit E. canis in the absence of female ticks. This tick development stage could be important in transmission of E. canis, and perhaps related pathogens, between vertebrate hosts under natural and experimental conditions.

Genetic variants of Anaplasma phagocytophilum infecting dogs in Western Washington State

Eight dogs from western Washington State suspected of being infected with Anaplasma phagocytophilum because of the finding of morulae in peripheral blood neutrophils were studied for determination of the etiologic agent of disease. All cases were diagnosed between April 2003 and April 2004. Six of the eight dogs had no travel history during the 6 months prior to presentation. Two dogs had traveled within the Northwest United States and Canada. Fever, lethargy, and anorexia were the most common clinical signs in the dogs. Lymphopenia, thrombocytopenia, and an elevated activity of alkaline phosphatase in the serum were the most common laboratory findings. All dogs tested during the acute phase of clinical signs were seropositive for A. phagocytophilum antibodies but negative for Ehrlichia canis antibodies. PCR amplification and direct sequencing of portions of the 16S rRNA gene from the whole blood of all seven dogs that were tested yielded A. phagocytophilum after a comparison to bacterial sequences available in the GenBank database. Five genetic variants were identified based on one or two nucleotide differences in the 16S rRNA gene sequences at nucleotide positions 54, 84, 86, and 120. Individual dogs were infected with more than one variant. Treatment with doxycycline or tetracycline resulted in a rapid resolution of clinical signs. The occurrence of canine granulocytic anaplasmosis in western Washington State suggests that A. phagocytophilum infection should be considered in differential diagnoses of dogs presenting with lethargy, anorexia, fever, and lameness, particularly in the context of lymphopenia, thrombocytopenia, and increased serum alkaline phosphatase. The zoonotic importance of A. phagocytophilum should support an increase in surveillance for horses and people residing in this area.

Repellency of deet and SS220 applied to skin involves olfactory sensing by two species of ticks

Responses of host-seeking nymphs of the blacklegged tick, Ixodes scapularis Say and lone star tick, Amblyomma americanum (Linnaeus) (Acari: Ixodidae) to the repellents N,N-diethyl-3-methylbenzamide (deet) and (1S, 2'S)-2-methylpiperidinyl-3-cyclohexene-1-carboxamide (SS220) were studied using fingertip laboratory bioassays. Ethanol solutions of both compounds applied to the skin strongly repelled both species of ticks at 0.8 and 1.6 micromole of compound/cm2 skin. The ticks were also repelled when two layers of organdie cloth covered the portion of a finger treated with either deet or SS220. Gas chromatographic analyses of the outer layer of cloth that had covered skin treated with 1.6 micromole compound/cm2 skin revealed only 0.1 nmole SS220/cm2 cloth and 2.8 nmole deet/cm2 cloth. However, in bioassays in which a single layer of cloth was treated with a dose of deet or SS220 equivalent to the amount found in the outer layer of cloth, ticks were not repelled. Results unequivocally demonstrated that these ticks responded to the repellents in the vapour phase when repellent treated skin was covered with cloth to obviate tactile contact with them, and made it clear that the ticks detect the repellents by olfactory sensing. Heretofore, the mode of action of deet and SS220 was unclear.

Suspected cases of Neorickettsia-like organisms in Brazilian dogs

Preliminary findings of gross and histopathological lesions consistent with salmon poisoning disease in 10 dogs from southern Brazil are described. Lesions were restricted to the spleen, lymph nodes, and intestinal lymphoid tissues. Grossly, there was marked hyperplasia of mesenteric lymph nodes and Peyer's patches. Microscopic alterations were characterized by diffuse hyperplasia of intestinal lymphoid tissues and Peyer's patches. Intracytoplasmic organisms consistent with Neorickettsia helminthoeca were demonstrated by Giemsa stain in reticuloendothelial cells of the intestine, spleen, Peyer's patches, and lymph nodes. We have named this organism Neorickettsia helminthoeca-like because of its marked similarity with the agent described in the United States.

Evaluation of antibiotic susceptibilities of Ehrlichia canis, Ehrlichia chaffeensis, and Anaplasma phagocytophilum by real-time PCR

We determined MICs of antibiotics against Anaplasma phagocytophilum, Ehrlichia chaffeensis, and Ehrlichia canis by real-time quantitative PCR. The doubling times of the organisms were established: 19 h for E. chaffeensis, 26 h for A. phagocytophilum, and 28 h for E. canis. In comparison to the reference method for determining sensitivities, which uses Diff-Quick staining, our PCR assay was very sensitive and specific. We confirmed that doxycycline and rifampin are highly active against these bacteria and found variable susceptibilities to fluoroquinolones; A. phagocytophilum was susceptible, but E. canis and E. chaffeensis were only partly susceptible. Beta-lactam compounds, cotrimoxazole, macrolide compounds, and telithromycin showed no activity against any of the three organisms. Thiamphenicol was found to be more active than chloramphenicol. For the first time, we showed that these three species have numerous point mutations in their 23S RNA genes, with those at positions 754, 2057, 2058, 2059, and 2611 (Escherichia coli numbering) known to confer resistance to macrolide compounds in other bacteria. The role of each of these mutations in resistance to these drugs should be investigated in the future. Our study confirms previous reports that quantitative PCR is a reliable method for determining antibiotic susceptibility; therefore, it might be useful for screening new drugs.

Pathogenicity of Metarhizium anisopliae (Deuteromycetes) and permethrin to Ixodes scapularis (Acari: Ixodidae) nymphs

Effectiveness of the entomopathogenic fungus Metarhizium anisopliae, for controlling nymphal Ixodes scapularis, was tested in laboratory and field trials. In the laboratory, M. anisopliae (Metschnikoff) Sorokin strain ESC1 was moderately pathogenic, with an LC50 of 10(7) spores/ml and induced 70% mortality at 10(9) spores/ml. In a field study, however, 10(9) spores/ml M. anisopliae did not effectively control questing I. scapularis nymphs, and significant differences were not detected in pre- and post-treatment densities. For nymphs collected and returned to the laboratory for observation, mortality was low in treatment groups, ranging from 20 to 36%. To assess whether a chemical acaricide would synergistically enhance pathogenicity of the fungus, we challenged unfed nymphal I. scapularis with combinations of M. anisopliae and permethrin, a relatively safe pyrethroid acaricide, in two separate bioassays. Significant interactions between M. anisopliae and permethrin were not observed, supporting neither synergism nor antagonism.

Human monocytotropic ehrlichiosis, Missouri

To determine the incidence, clinical and laboratory characteristics, and utility of molecular diagnosis of human monocytotropic ehrlichiosis (HME) in the primary care setting, we conducted a prospective study in an outpatient primary care clinic in Cape Girardeau, Missouri. One hundred and two patients with a history of fever for 3 days (>37.7°C), tick bite or exposure, and no other infectious disease diagnosis were enrolled between March 1997 and December 1999. HME was diagnosed in 29 patients by indirect immunofluorescent antibody assay and polymerase chain reaction (PCR). Clinical and laboratory manifestations included fever (100%), headache (72%), myalgia or arthralgia (69%), chills (45%), weakness (38%), nausea (38%), leukopenia (60%), thrombocytopenia (56%), and elevated aspartate aminotransferase level (52%). Hospitalization occurred in 41% of case-patients. PCR sensitivity was 56%; specificity, 100%. HME is a prevalent, potentially severe disease in southeastern Missouri that often requires hospitalization. Because clinical presentation of HME is nonspecific, PCR is useful in the diagnosis of acute HME.

Obligatory intracellular parasitism by Ehrlichia chaffeensis and Anaplasma phagocytophilum involves caveolae and glycosylphosphatidylinositol-anchored proteins

Obligatory intracellular, human ehrlichiosis agents Ehrlichia chaffeensis and Anaplasma phagocytophilum create unique replicative compartments devoid of lysosomal markers in monocytes/macrophages and granulocytes respectively. The entry of these bacteria requires host phospholipase C (PLC)-gamma2 and protein tyrosine kinases, but their entry route is still unclear. Here, using specific inhibitors, double immunofluorescence labelling and the fractionation of lipid rafts, we demonstrate that bacterial entry and intracellular infection involve cholesterol-rich lipid rafts or caveolae and glycosylphosphatidylinositol (GPI)-anchored proteins. By fluorescence microscopy, caveolar marker protein caveolin-1 was co-localized with both early and replicative bacterial inclusions. Additionally, tyrosine-phosphorylated proteins and PLC-gamma2 were found in bacterial early inclusions. In contrast, clathrin was not found in any inclusions from either bacterium. An early endosomal marker, transferrin receptor, was not present in the early inclusions of E. chaffeensis, but was found in replicative inclusions of E. chaffeensis. Furthermore, several bacterial proteins from E. chaffeensis and A. phagocytophilum were co-fractionated with Triton X-100-insoluble raft fractions. The formation of bacteria-encapsulating caveolae, which assemble and retain signalling molecules essential for bacterial entry and interact with the recycling endosome pathway, may ensure the survival of these obligatory intracellular bacteria in primary host defensive cells.

A novel antigen from Anaplasma marginale: characterization, expression and preliminary evaluation of the recombinant protein

Through a process of protein fractionation and vaccination we previously identified four native antigens that confer a degree of protection against challenge with Anaplasma marginale. One of these, Ana 29 has been successfully cloned and sequenced using degenerate primers designed to N-terminal and internal peptide sequences. The full-length gene codes for a protein with a theoretical molecular weight of 27 kDa and pI 8.6. The sequence is highly conserved, showing 99% identity between two Australian and an American isolate of A. marginale. The gene sequences from these isolates also share 99% identity with the strain of Anaplasma centrale used in the commercial Australian vaccine. Protein prediction algorithms suggest the native protein is an integral membrane protein. This protein has been over-expressed and purified from Escherichia coli and used in vaccination trials in cattle using two adjuvants. The initial results from the trial show a significant level of protection was obtained with one adjuvant; in comparison, the second adjuvant slightly aggravated the disease. Preliminary data suggests a good correlation between the induction of an IgG2 response and protection.

Comparative activity of deet and AI3-37220 repellents against the ticks Ixodes scapularis and Amblyomma americanum (Acari: Ixodidae) in laboratory bioassays

The repellents N,N-diethyl-3-methylbenzamide (deet) and racemic 2-methylpiperidinyl-3-cyclohexene-1-carboxamide (AI3-37220) were evaluated using two different laboratory bioassays to determine their relative effectiveness against host-seeking nymphs of the blacklegged tick, Ixodes scapularis Say, and the lone star tick, Amblyomma americanum (L.). In a petri dish bioassay, ticks were released within a ring of repellent on a horizontal filter paper disk. In the second bioassay, ticks were allowed to climb a vertical strip of filter paper whose central portion was treated with a repellent. Deet and AI3-37220 were more effective against I. scapularis than A. americanum nymphs. In the petri dish bioassay, none of the concentrations of deet or AI3-37220 tested confined A. americanum within the treated ring. However, in the vertical bioassay, both species exhibited avoidance of the repellents, and I. scapularis was repelled by much lower concentrations than A. americanum. I. scapularis were repelled by lower concentrations in the vertical bioassay than in the petri dish bioassay. Deet was slightly more effective against I. scapularis than AI3-37220 in both bioassays, but AI3-37220 was significantly more effective than deet against A. americanum in the vertical bioassay.

L’ehrlichiose granulocytique humaine en Europe

Human granulocytic ehrlichiosis is an emerging infectious disease, which is transmitted by the tick Ixodes ricinus in Europe, like other diseases: Lyme disease, tick-borne encephalitis, babesiosis... This tick lives in the forest and its hematophagic activity ranges from April to October. Flu and febrile symptoms ten days after tick bite should suggest diagnosing the disease. Disease evolution is generally favorable, even if serious complications may occur. Leukopenia, thrombocytopenia, and elevated serum transaminases are common laboratory findings. Complementary assays useful for the diagnosis are: blood smear, indirect immunofluorescence, and polymerase chain reaction. Biological diagnostic criteria are more and more accurate, with the evolution of knowledge and technique. Tetracycline treatment generally leads to clinical and biological recovery. Informing physicians and occupationally exposed people should reinforce current prevention measures against tick bites.

Chemical composition of some components of the arrestment pheromone of the black-legged tick, Ixodes scapularis (Acari: Ixodidae) and their use in tick control

Chemical analysis (high-performance liquid chromatography) and bioassay demonstrated the presence of compounds that seem to be components of the Ixodes scapularis arrestment pheromone. Only two purines, guanine and xanthine, were found in acidified saline extracts made from cast skins after molting of fed nymphs, fed larvae, and fecal/excretory exudates deposited by unfed adults on substrates in their environment. The ratio of guanine to xanthine was 10.6:1 in an extract from the nymphal skins versus 0.95:1 in an extract from the larval skins. Guanine, xanthine, and traces of a third purine, tentatively identified as 8-azaguanine, were found in extracts made from filter paper strips or washings from glass vials contaminated with tick feces and excreta left by unfed adults. 8-azaguanine may be a product of microbial degradation of the other purines rather than a natural product from the ticks. Low concentrations of ammonia also were detected in saline extracts of excreta from feeding ticks. Hematin also was found in NH4OH extracts of the black fecal/excretory exudates deposited by the unfed ticks. Hematin was tentatively identified by comparison of spectra with that of the authentic standard. Bioassays demonstrated a strong positive arrestment response to cast skins found to contain a mixture of guanine and xanthine and to black fecal/excretory exudates containing guanine, xanthine, the putative 8-azaguanine, and hematin. A Noldus video tracking system using a CCD video camera and Ethovision Pro tracking software showed statistically significant increases in the frequency of visits to the treated zone versus the control. Ticks were significantly more likely to assemble in response to the tick exudates within as little as 3 h compared with the controls. Previous bioassay studies also showed strong positive responses to guanine, xanthine, other purines, and hematin. Comparisons with the arrestment pheromones of other tick species are described. The inclusion of the pheromone components in a permethrin-impregnated oily matrix, Last Call, increased the lethal activity of the product to 95% compared with only 65% in the formulation with permethrin alone. More detailed knowledge of I. scapularis arrestment pheromone may be useful for improving the efficacy of this tick-killing technology even further.

A cautionary note: survival of nymphs of two species of ticks (Acari: Ixodidae) among clothes laundered in an automatic washer

Host-seeking ticks often remain on clothing of persons returning home from work or recreation in tick habitats, and can pose at least a temporary risk to people and pets in these homes. Laundering clothing has been one of the recommendations to reduce tick exposure. Host-seeking lone star tick, Amblyomma americanum (L.), and blacklegged tick, Ixodes scapularis Say, nymphs confined in polyester mesh packets, were included with laundry in cold, warm, and hot wash cycles of an automatic clothes washer. Ticks were also placed with washed clothing and subjected to drying in an automatic clothes dryer set on high heat and on air only (unheated). Most nymphs (> or = 90%) of both species survived the cold and warm washes, and 95% of A. americanum nymphs survived the hot wash. At the time of their removal from the washer, I. scapularis nymphs were clearly affected by the hot wash, but 65% were considered alive 20-24 h later. Large percentages of nymphs of both species survived hot washes in which two other detergents (a powder containing a nonchlorine bleach and a liquid) were used. All ticks were killed by the 1 h cycle at high heat in the clothes dryer, but with unheated air some nymphs of both species survived the 1 h cycle in the dryer. Given the laundering recommendations of clothing manufacturers and variation in the use automatic clothes washers, laundry washed in automatic washers should not be considered free of living ticks.

Clinical manifestations, epidemiology, and laboratory diagnosis of human monocytotropic ehrlichiosis in a commercial laboratory setting

Clinical, epidemiological, and laboratory diagnostic issues of human monocytotropic ehrlichiosis (HME) were investigated in a retrospective case study conducted at a national reference laboratory (Focus Technologies, formerly MRL Reference Laboratory), and at the University of Texas Medical Branch at Galveston, Texas, during 1997 and 1998. Standard questionnaires were sent to physicians for each laboratory-diagnosed patient 2 days to 2 weeks after immunofluorescent antibody assay results were available. Among the 41 cases for which data were obtained, 32 (78%) were definite cases of HME, and 9 (22%) were probable cases of HME. Tick bite or exposure to ticks was recorded in more than 97% of cases. The most prominent clinical findings were fever, abdominal tenderness, and regional lymphadenopathy. There was an association between age and severity of illness. The main laboratory findings included leukopenia, thrombocytopenia, and elevated aspartate aminotransferase and alanine aminotransferase. Clinical and laboratory findings were nonspecific and were not good predictors of the severity of illness. The 90% of patients who received doxycycline treatment underwent rapid clinical improvement with a favorable outcome. The usual duration of effective treatment with doxycycline was 7 to 10 days. This retrospective study is unique because it was based in a commercial reference laboratory setting that receives specimens from different geographic locations. The clinical and laboratory information from 41 patients provides insight into the epidemiological, clinical, and laboratory characteristics of HME.

Ehrlichia chaffeensis and Anaplasma phagocytophilum lack genes for lipid A biosynthesis and incorporate cholesterol for their survival

Ehrlichia chaffeensis and Anaplasma phagocytophilum are agents of human monocytic and granulocytic ehrlichioses, respectively. They are extremely sensitive to mechanical stress and are pleomorphic gram-negative bacteria. Membrane incorporation of cholesterol from the eukaryotic host is known to be essential for other fragile and pleomorphic bacteria and mycoplasmas that lack a cell wall. Thus, we tested whether cholesterol is required for E. chaffeensis and A. phagocytophilum. Using a freeze fracture technique and biochemical analysis, these bacteria were found to contain significant levels of membrane cholesterol. These bacteria lack genes for cholesterol biosynthesis or modification. However, host cell-free bacteria had the ability to take up directly exogenous cholesterol or NBD-cholesterol, a fluorescent cholesterol derivative. Treatment of the bacteria with cholesterol extraction reagent methyl-beta-cyclodextrin caused their ultrastructural changes. Furthermore, pretreatment of the bacteria with methyl-beta-cyclodextrin or NBD-cholesterol deprived these bacteria of the ability to infect leukocytes, thus killing these obligate intracellular bacteria. Analysis of E. chaffeensis and A. phagocytophilum genome sequences revealed that these bacteria lack all genes for the biosynthesis of lipid A and most genes for the biosynthesis of peptidoglycan, which confer structural strength to gram-negative bacteria. Taken together, these results suggest that human ehrlichiosis agents became cholesterol dependent due to the loss of these genes. As the first report of gram-negative bacteria incorporating cholesterol for survival, these findings offer insight into the unique nature of their parasitism and imply that cholesterol is important in the control of human ehrlichioses.

Major surface protein 2 of Anaplasma phagocytophilum facilitates adherence to granulocytes

Anaplasma phagocytophilum is an obligate intracellular bacterium that infects myeloid cells in the mammalian host. Msp2 (p44) is the major immunodominant outer-membrane protein of these bacteria. We hypothesized that Msp2 acts as an adhesin for A. phagocytophilum entry into granulocytes. This potential role was investigated by blocking binding with Msp2 monoclonal antibodies and by antagonizing binding and propagation with recombinant Msp2 (rMsp2) in vitro. With HL-60 cells, fresh human peripheral blood neutrophils, and a cell line devoid of the fucosylated platelet selectin glycoprotein ligand 1 (PSGL-1) receptor for A. phagocytophilum or one that was transfected to express this ligand, Msp2 monoclonal antibody and rMsp2 used as the antagonist caused concentration-dependent reductions in bacterial adhesion (P < 0.007 and P < 0.02, respectively) and propagation (P < 0.05 and P < 0.001), although inhibition of adhesion or propagation was moderate and incomplete. Likewise, rMsp2 bound to surfaces of the transfected cell at a level similar to that of extracellular A. phagocytophilum and significantly (P < 0.05) beyond that of nontransfected cells. Moreover, a dose-dependent reduction (P < 0.019) in PSGL-1 monoclonal antibody binding to HL-60 cells was elicited with rMsp2. We conclude that Msp2s of A. phagocytophilum are involved in bacterial adhesion to ligands on host myeloid cells before intracellular infection.

Prevalence of Anaplasma phagocytophila and Borrelia burgdorferi in Ixodes persulcatus ticks from northeastern China

A total of 1,345 Ixodes persulcatus ticks collected from northeastern China were investigated for the presence of Anaplasma phagocytophila and Borrelia burgdorferi by a nested polymerase chain reaction (PCR). Sixty-two (4.6%) ticks were positive for A. phagocytophila and 454 (33.8%) were positive for B. burgdorferi. Seven (0.5%) were coinfected with both agents. Sequence analysis of 919-basepair PCR amplicons revealed three types of A. phagocytophila. Type 1 was identical to the published sequences of A. phagocytophilas responsible for human granulocytic ehrlichiosis (HGE). The other two variants differed from the HGE agent sequence at one and four positions, respectively. These findings imply that infection with A. phagocytophila poses a potential health threat to both humans and animals in northeastern China, and that ehrlichiosis should be considered in the differential diagnosis of febrile patients with a history of tick bite, particularly when clinical manifestations are atypical for Lyme disease.

Interference between the agents of Lyme disease and human granulocytic ehrlichiosis in a natural reservoir host

Agents of Lyme disease (Borrelia burgdorferi) and human granulocytic ehrlichiosis (Ehrlichia phagocytophila) are perpetuated in a natural cycle involving the black-legged tick (Ixodes scapularis) and its vertebrate hosts. Using I. scapularis nymphs as the mode of infectious challenge, we studied how infection with one pathogen in white-footed mice (Peromyscus leucopus) affects their ability to acquire the other agent and subsequently to infect larvae, which these agents would do in nature. Two groups of mice were infected with either B. burgdorferi or E. phagocytophila. One week later, B. burgdorferi-infected mice were challenged with E. phagocytophila, and E. phagocytophila-infected mice were challenged with B. burgdorferi. Simultaneously, two control groups of uninfected mice were infected with each agent from the same tick cohorts used on the first groups of mice. Uninfected I. scapularis larvae were fed on all mice for xenodiagnosis at weekly intervals lasting 2 months. For the B. burgdorferi challenge, all control and E. phagocytophila-infected mice acquired B. burgdorferi. However, fewer xenodiagnostic larvae acquired B. burgdorferi from mice with mixed infections compared with mice infected with B. burgdorferi only. For the E. phagocytophila challenge, all five control mice acquired E. phagocytophila, but only two of five mice infected with B. burgdorferi subsequently acquired E. phagocytophila. Consequently, mice with both infections produced fewer xenodiagnostic ticks infected with E. phagocytophila than mice infected with E. phagocytophila only. Thus, a primary infection with either B. burgdorferi or E. phagocytophila in mice inhibited transmission of a second agent, suggesting interference between these two agents.

Expression of multiple outer membrane protein sequence variants from a single genomic locus of Anaplasma phagocytophilum

Anaplasma phagocytophilum is the causative agent of an emerging tick-borne zoonosis in the United States and Europe. The organism causes a febrile illness accompanied by other nonspecific symptoms and can be fatal, especially if treatment is delayed. Persistence of A. phagocytophilum within mammalian reservoir hosts is important for ensuring continued disease transmission. In the related organism Anaplasma marginale, persistence is associated with antigenic variation of the immunoprotective outer membrane protein MSP2. Extensive diversity of MSP2 is achieved by combinatorial gene conversion of a genomic expression site by truncated pseudogenes. The major outer membrane protein of A. phagocytophilum, MSP2(P44), is homologous to MSP2 of A. marginale, has a similar organization of conserved and variable regions, and is also encoded by a multigene family containing some truncated gene copies. This suggests that the two organisms could use similar mechanisms to generate diversity in outer membrane proteins from their small genomes. We define here a genomic expression site for MSP2(P44) in A. phagocytophilum. As in A. marginale, the msp2(p44) gene in this expression site is polymorphic in all populations of organisms we have examined, whether organisms are obtained from in vitro culture in human HL-60 cells, from culture in the tick cell line ISE6, or from infected human blood. Changes in culture conditions were found to favor the growth and predominance of certain msp2(p44) variants. Insertions, deletions, and substitutions in the region of the genomic expression site encoding the central hypervariable region matched sequence polymorphisms in msp2(p44) mRNA. These data suggest that, similarly to A. marginale, A. phagocytophilum uses combinatorial mechanisms to generate a large array of outer membrane protein variants. Such gene polymorphism has profound implications for the design of vaccines, diagnostic tests, and therapy.

Wolbachia endosymbionts in fleas (Siphonaptera)

Intracellular endosymbionts, Wolbachia spp., have been reported in many different orders of insects and in nematodes but not previously in fleas. This is the first conclusive report of Wolbachia spp. within members of the Siphonaptera. Using nested polymerase chain reaction (PCR) targeting of the 16S ribosomal RNA gene, we screened for Wolbachia spp. in fleas collected from 3 counties in Georgia and 1 in New York. The prevalence of Wolbachia spp. detected varied among the 6 different species screened: 21% in the cat flea Ctenocephalides felis (n = 604), 7% in the dog flea C. canis (n = 28), 25% in Polygenus gwyni (n = 8), 80% in Orchopeas howardi (n = 15), 94% in Pulex simulans (n = 255), and 24% in the sticktight flea Echidnophaga gallinacea (n = 101). Wolbachia spp. infection in fleas was confirmed by sequencing positive PCR products, comparing sequenced 16S ribosomal DNA (rDNA) with Wolbachia spp. sequences in GenBank using BLAST search, and subjecting sequence data to phylogenetic analysis. For further confirmation, 16S rDNA-positive samples were reamplified using the wsp gene.

Cloning and characterization of an Ehrlichia canis gene encoding a protein localized to the morula membrane

A gene encoding a 23.5-kDa ehrlichial morula membrane protein designated MmpA was cloned by screening an Ehrlichia canis expression library with convalescent dog sera, which resulted in three positive clones. Sequence analysis of the insert DNAs from all three clones indicated an open reading frame with a size of 666 bp that encodes MmpA. The structural analysis of MmpA indicated that it is a transmembrane protein with extreme hydrophobicity. Southern blot analysis of the HindIII-digested chromosomal DNA demonstrated the presence of a single copy of the mmpA gene in E. canis and Ehrlichia chaffeensis but not in the human granulocytic ehrlichiosis agent. The mmpA gene was amplified, cloned, and expressed as a fusion protein. Polyclonal antibodies to the recombinant protein (rMmpA) were raised in rabbits. Western blot analysis of E. canis and E. chaffeensis lysates with the anti-rMmpA serum resulted in the presence of an MmpA band only in E. canis, not in E. chaffeenesis. Sera from dogs which were either naturally or experimentally infected with E. canis recognized the recombinant protein. Double immunofluorescence confocal microscopy studies demonstrated that MmpA was localized mainly on the morula membrane of E. canis. Since the morula membrane is the interface between the ehrlichial growing environment and the host cytoplasm, MmpA may play a role in bacterium-host cell interactions.

Ehrlichia platys (Anaplasma platys) in dogs from Maracaibo, Venezuela: an ultrastructural study of experimental and natural infections

Since 1982 Ehrlichia platys, now emended as Anaplasma platys, has been diagnosed in dogs from Maracaibo, Venezuela, using buffy coat smears stained with Dip Quick. Three dogs were inoculated with an A. platys strain. When parasitemia reached 60-97%, blood samples obtained from the inoculated dogs and from two naturally infected dogs were centrifuged to obtain platelet-rich plasma, which was mixed with 0.1% glutaraldehyde at 37 C for 10 minutes. Platelet pellets were fixed in 3% glutaraldehyde for 72 hours and processed for conventional transmission electron microscopy. Platelets contained pleomorphic organisms with a distinct double membrane that was not observed when the bodies were in a determinate developmental stage. There were 1-15 individual bodies included in a host cell vacuole. The organisms had an electron-lucent inner area, whereas the internal surface of their inner plasma membranes exhibited an electron-dense rough substance. In naturally infected dogs, organisms with different ultrastructural features were found inside the same platelet. Some organisms contained central dense material surrounded by a pale zone, which was in turn surrounded by a moderately dense peripheral area. Other organisms contained an eccentrically electron-dense material. The intravacuolar space appeared fully electron-lucent. Each organism usually exhibited inner fine strands. Empty structures displaying junctions with the vacuolar membrane were observed. Our results indicate that distinct ultrastructural characteristics are associated with different stages of A. platys development and may differ among A. platys strains.

Prevalence of granulocytic Ehrlichia and Borrelia burgdorferi sensu lato in Ixodes ricinus ticks collected from Southwestern Finland and from Vormsi Island in Estonia

Altogether, 343 adult and 111 nymphal Ixodes ricinus ticks collected from parks in Turku and suburban and rural islands of the Turku archipelago, Finland, and 100 adult I. ricinus ticks collected from Vormsi Island, Estonia, were included in this study. Using the polymerase chain reaction the ticks were examined for 16S rDNA of the Ehrlichia phagocytophila genogroup and for Borrelia burgdorferi sensu lato recA and flagellin genes. None of the Finnish ticks was found to be infected with E. phagocytophila, whereas 3% of the Estonian ticks were positive for this organism. The rate of Finnish ticks infected with B. burgdorferi sensu lato varied from 0% to 11.6% (mean 5%; 9% for adult and 4% for nymphal ticks). The corresponding rate for Estonian ticks was 15%. Borrelia afzelii was the most common genospecies in both Finnish (2.6%) and Estonian (12%) ticks. B. burgdorferi sensu stricto was detected in 2.0% of the Finnish ticks, but in none of the Estonian ticks. These results suggest that the E. phagocytophila genogroup is very rare in Finnish ticks, although the ticks were collected from an area endemic for Lyme borreliosis. In Estonia, E. phagocytophila is found in ticks and may cause disease.

Human granulocytic ehrlichiosis in Europe

Ehrlichiosis comprises a group of emerging tick-borne infectious diseases caused by obligate intracellular Gram-negative bacteria that infect leukocytes. Infections caused by members of the genus Ehrlichia have been described in animals and humans, but to date there are no convincing reports of the presence of other types of human ehrlichiosis different from human granulocytic ehrlichiosis (HGE) in Europe. The European vector is the same as that of Lyme borreliosis, the hard tick Ixodes ricinus, and HGE has a similar epidemiology to that of Borrelia burgdorferi infection. Across Europe, I. ricinus is infected to a variable extent (0.4-66.7%) with the causative agent Ehrlichia (Anaplasma) phagocytophila genogroup, and since its first description in Slovenia in 1997, details of 15 patients have been published. Diagnosis requires careful consideration of all circumstances and symptoms (history of tick bite and the presence of a flu-like syndrome with variable degrees of anemia, thrombocytopenia, and leukopenia, and elevated liver enzymes). Some differences can be seen between US and European HGE patients. European HGE cases have a less severe course, and the presence of morulae is uncommon. In Europe, verification of HGE has been based on PCR and immunofluorescence antibody tests, because no isolation from humans has been reported.

Molecular Evidence SupportingEhrlichia canis-Like Infection in Cats

Currently, the pathogenic role of Ehrlichia canis in cats has been proposed predominantly on the basis of the serologic evidence of natural infection and the infrequent detection of morulae‐like structures within the cytoplasm of leukocytes in cats. The purpose of this report was to provide molecular evidence supporting E cams‐like infection in 3 cats that had clinical manifestations consistent with canine ehrlichiosis but lacked antibodies to E canis antigens. Serum from all 3 cats contained antinuclear antibodies (ANAs). The predominant disease manifestation was polyarthritis in 1 cat and bone marrow hypoplasia or dysplasia, accompanied by pancytopenia or anemia and thrombocytopenia, in 1 cat each. The alignment of E canis partial 16S ribosomal DNA (rDNA; 382 nucleotide positions), amplified from EDTA blood samples from each cat, was identical to each other and was identical to a canine isolate of E canis (GenBank accession number AF373613). In 1 cat, concurrent treatment with corticosteroids may have interfered with the therapeutic effectiveness of doxycycline for the elimination of E canis‐like infection. To further define the spectrum of ehrlichiosis in cats, polymerase chain reaction (PCR) testing may be necessary until serologic testing is thoroughly validated in experimentally or naturally infected cats. In addition, until E canis has been isolated from cats and several tissue culture isolates are available from disparate geographic regions for detailed comparative genetic study, the molecular evidence presented in this study supporting E canis‐like infection in cats must be interpreted with caution.

Molecular evidence supporting Ehrlichia canis-like infection in cats

Currently, the pathogenic role of Ehrlichia canis in cats has been proposed predominantly on the basis of the serologic evidence of natural infection and the infrequent detection of morulae-like structures within the cytoplasm of leukocytes in cats. The purpose of this report was to provide molecular evidence supporting E. canis-like infection in 3 cats that had clinical manifestations consistent with canine ehrlichiosis but lacked antibodies to E. canis antigens. Serum from all 3 cats contained antinuclear antibodies (ANAs). The predominant disease manifestation was polyarthritis in 1 cat and bone marrow hypoplasia or dysplasia. accompanied by pancytopenia or anemia and thrombocytopenia, in 1 cat each. The alignment of E. canis partial 16S ribosomal DNA (rDNA: 382 nucleotide positions), amplified from EDTA blood samples from each cat, was identical to each other and was identical to a canine isolate of E. canis (GenBank accession number AF373613). In 1 cat, concurrent treatment with corticosteroids may have interfered with the therapeutic effectiveness of doxycycline for the elimination of E. canis-like infection. To further define the spectrum of ehrlichiosis in cats, polymerase chain reaction (PCR) testing may be necessary until serologic testing is thoroughly validated in experimentally or naturally infected cats. In addition, until E. canis has been isolated from cats and several tissue culture isolates are available from disparate geographic regions for detailed comparative genetic study, the molecular evidence presented in this study supporting E. canis-like infection in cats must be interpreted with caution.

Laboratory and field evaluation of the entomopathogenic fungus Metarhizium anisopliae (Deuteromycetes) for controlling questing adult Ixodes scapularis (Acari: Ixodidae)

Unfed adult Ixodes scapularis Say were treated with spores of the entomopathogenic fungus Metarhizium anisopliae Metschnikoff in the laboratory and in the field. An M. anisopliae suspension containing 4 x 10(9) spores per milliliter caused 96% mortality in the laboratory, versus 53% mortality among field-treated ticks. The LC50 value for unfed adult I. scapularis in the laboratory was 4 x 10(7) spores per milliliter. Our results indicate that M. anisopliae was highly pathogenic to unfed adult ticks and showed potential for controlling questing adult I scapularis.

The past and present threat of rickettsial diseases to military medicine and international public health

Morbidity and mortality caused by rickettsioses have had a major influence on military activities and public health for >2000 years. The threat posed by the rickettsioses is reviewed, focusing on the impact and epidemiology of those that have adversely influenced wartime operations and the current challenges posed by these diseases. With their uneven worldwide distribution, the discovery of drug-refractory strains of Orientia tsutsugamushi, the increased threat of their use in acts of bioterrorism, frequent deployment of troops to regions of endemicity, and exposures due to increased humanitarian missions, these diseases continue to be a threat to military personnel in the field. Effective strategies to reduce the impact of these diseases include development of effective vaccines, enhanced surveillance, and development of new safe, effective, and odorless repellants. The continuation of a proven, highly productive military infectious disease research program is essential for providing solutions to these daunting tasks.

Prevalence of granulocytic Ehrlichiae in Ixodes ricinus ticks in Middle Germany (Thuringia) detected by PCR and sequencing of a 16S ribosomal DNA fragment

A total of 305 Ixodes ricinus ticks (243 nymphs and 62 adults) were collected from three different regions of Thuringia in Middle Germany which are known to be endemic for Borrelia burgdorferi. Our aim was to investigate the carrier rate of ticks for granulocytic Ehrlichia species. The presence of ehrlichial 16S ribosomal DNA was investigated by polymerase chain reaction. Using primers specific for the Ehrlichia phagocytophila group PCR fragments of 151 bp and 943 bp, respectively, were produced in positive samples. Adult ticks showed a significantly higher infection rate (4/62; 6.5%) compared to nymphs (3/243; 1.2%). Prevalence rates varied between 0 and 3.8% regarding the different areas under investigation. The nucleotide sequences showed high similarity (between 97.5% and 99% identity) to the known sequences of the three E. phagocytophila group members HGE agent, E. phagocytophila and Ehrlichia equi. The sequence data did not allow a final classification to a particular member of this group.

Granulocytic ehrlichiosis in Swedish dogs and horses

Granulocytic ehrlichiosis is a frequently diagnosed tick-borne disease in Swedish dogs and horses. The infection is caused by a granulocytic Ehrlichia species belonging to the Ehrlichia phagocytophila genogroup. In the acute stage, the disease is mainly characterized as a febrile illness and diagnosis can be confirmed by the demonstration of ehrlichial inclusions in blood granulocytes. Seropositivity in many healthy dogs and horses indicate that the infection also can be transient without clinical signs. The infection can persist in experimentally inoculated animals for months, but to what extent this persistance also occurs in naturally infected animals and is associated with clinical signs, is not clarified yet.