Morphological aspects of blood digestion in a parasitic mite Bakericheyla chanayi.

All life stages of B. chanayi (Acariformes: Cheyletidae) are characterized by occasional bloodsucking and a long period of digestion. No newly engorged mites were found during the period of their host birds' migration. The fine structure of the digestive tract of a blood-feeding acariform mite is described for the first time. The anterior midgut (AMG) is a place of blood digestion, while the posterior midgut (PMG) is involved in nitrogen metabolism forming guanine crystals as the main end-product. The AMG epithelium consists of digestive cells that probably arise from mitotically active basal cells with high synthesizing activity. As observed in ticks, blood digestion is accompanied by the formation of huge endosomes that serve as places of storage and sorting of ingested material. Digestive cells show different types of endocytotic activity as well as various late endosomes, which implies different subcellular pathways for different blood components. In both midgut regions, elimination of the excretory material occurs by apocrine secretion or by discharging of apical cell fragments (loaded with lysosomes) into the gut lumen. The formation of guanine granules occurs inside the lysosomes of PMG epithelial cells thus having much in common with intracellular digestion. Peculiarities of intracellular blood digestion were analyzed according to the modern hypothesis of endocytosis and compared to what is known in ticks.

Systematics and ecology of the brown dog tick, Rhipicephalus sanguineus.

Rhipicephalus sanguineus, the brown dog tick, kennel tick, or pan-tropical dog tick, is probably the most widespread ixodid tick, colonising both human and canine dwellings. It is of great significance in both human and veterinary medicine as a vector of several important pathogens and can also cause clinical illness in heavy infestations of dogs. However, there are still significant taxonomic uncertainties, and it is probable that some records of this tick refer to other species. Most past reviews have been broad-ranging or have focused on the pathogens that R. sanguineus transmits, and relatively few have considered its biology in detail or the issues around its true identity. The present review has paid most attention to the taxonomy of R. sanguineus and to the ecological factors that influence tick survival and distribution, particularly in a climate change context. It is evident that more research is required on the systematics of the R. sanguineus species complex, in order to elucidate the epidemiology and prevention of the diseases that it transmits, and to provide the relevant biological data required for development of predictive models of future tick distribution in a climate change scenario.

[The main evolutionary trends in sensory organs and questing behavior of parasitiform ticks and mites (Parasitiformes)].

Studies of sensory organs in parasitiform mites by methods of scanning and transmitting electron microscopy and electrophysiology in Russia were initiated by Yu. S. Balashov. A review of the material accumulated since that time allows revealing the main trends in evolution of the morphology the main complicated sense organs (the Haller's organ, palpal and tarsal organs, and eyes). Tight correlation between the evolution of the questing behavior and of sensory organs was demonstrated.

Observation of live ticks (Haemaphysalis flava) by scanning electron microscopy under high vacuum pressure.

Scanning electron microscopes (SEM), which image sample surfaces by scanning with an electron beam, are widely used for steric observations of resting samples in basic and applied biology. Various conventional methods exist for SEM sample preparation. However, conventional SEM is not a good tool to observe living organisms because of the associated exposure to high vacuum pressure and electron beam radiation. Here we attempted SEM observations of live ticks. During 1.5×10(-3) Pa vacuum pressure and electron beam irradiation with accelerated voltages (2-5 kV), many ticks remained alive and moved their legs. After 30-min observation, we removed the ticks from the SEM stage; they could walk actively under atmospheric pressure. When we tested 20 ticks (8 female adults and 12 nymphs), they survived for two days after SEM observation. These results indicate the resistance of ticks against SEM observation. Our second survival test showed that the electron beam, not vacuum conditions, results in tick death. Moreover, we describe the reaction of their legs to electron beam exposure. These findings open the new possibility of SEM observation of living organisms and showed the resistance of living ticks to vacuum condition in SEM. These data also indicate, for the first time, the usefulness of tick as a model system for biology under extreme condition.

Amblyomma imitator ticks as vectors of Rickettsia rickettsii, Mexico.

Real-time PCR of Amblyomma imitator tick egg masses obtained in Nuevo Leon State, Mexico, identified a Rickettsia species. Sequence analyses of 17-kD common antigen and outer membrane protein A and B gene fragments showed to it to be R. rickettsii, which suggested a potential new vector for this bacterium.

Ultrastructural study of muscles fibers in tick Hyalomma (Hyalomma) anatolicum anatolicum (Ixodoidea: Ixodidae).

In the present study, ticks were obtained from a colony maintained at 28 degrees C and 75% relative humidity in at the Department of Biology, University College Umm Al-Qura University, Saudi Arabia and the Transmission Electron Microscope technique (TEM) was used to describes the ultrastructure and description of muscle of the of ixodid tick Hyalomma (Hyalomma) anatolicum anatolicum. The results showed that muscles of the unfed ticks Hyalomma (Hyalomma) anatolicum anatolicum in longitudinal sections are spindle-shaped to cylindrical muscle fibers. In the unfed nymph Hyalomma (Hyalomma) anatolicum anatolicum skeletal and visceral muscles are distinguished according to structure, function and position. These muscles include the capitulum, dorsoventral and leg oblique muscles. All muscle fibers are ensheathed (covered by sheath) in a sarcolemma. Their muscle fibers have striated pattern of successive sarcomeres whose thick myosin filaments are surrounded by orbitals of up to 12 thin actin filaments. The cytoplasm of the epidermal cell appears largely devoted with complicated microtubules present in parallel with long axis of adjacent muscle fibers. The cell membrane invaginates into tubular system extending deeply into the sarcoplasm and closely associated to cisternae of sarcoplasmic reticulum. The tubular system and sarcoplasmic reticulum forming two-membered (dyads) are considered to be the main route of calcium ions whose movement are synchronized with the motor impulse to control muscles contraction. In the sarcoplasm two types of muscle fibers are recognized according to thickness and density and mitochondrial size, distribution and population. Both skeletal and visceral muscles are invaginated by tracheoles and innervated by nerve axons containing synaptic vesicles. The actin and myosin filaments are slightly interrupted and the tubular system sarcoplasmic reticulum is well demonstrated.

Boophilus microplus infection by Beauveria amorpha and Beauveria bassiana: SEM analysis and regulation of subtilisin-like proteases and chitinases.

Beauveria bassiana is a well-known broad-range arthropod pathogen which has been used in biological control of several pest insects and ticks such as Boophilus microplus. Beauveria amorpha has both endophytic and entomopathogenic characteristics, but its capacity for biological control has still not been studied. During the processes of host infection, B. bassiana and B. amorpha produce several hydrolytic extracellular enzymes, including proteases and chitinases, which probably degrade the host cuticle and are suggested to be pathogenicity determinants. To access the role of these enzymes during infection in the tick B. microplus, we analyzed their secretion during fungus growth in single and combined carbon sources, compared to complex substrates such as chitin and B. microplus cuticle. Chitin and tick cuticle-induced chitinase in both fungus and protease was induced only by tick cuticle. SEM analysis of B. amorpha and B. bassiana infecting B. microplus showed apressorium formation during penetration on cattle tick cuticle.

[Ticks (Acarina: Ixodidae) as vectors and reservoirs of pathogen microorganisms in Spain]. / Las garrapatas (Acarina: Ixodida) como transmisores y reservorios de microorganismos patógenos en España.

Hard and soft-ticks are obligate haematophagous arachnids of medical and veterinary significance mainly because of the animal disease agents transmitted by them, which include an array of different pathogens (virus, bacteria, protozoa and nematodes). Ticks transmit microbes by several routes including salivary secretions, coxal fluids, regurgitation and faeces. Among the biological factors that contribute to the high vector potential of ticks are their living habits and characteristic properties of their saliva secretions and blood digestion. In the Iberian Peninsula, the prostriata tick Ixodes ricinus, and the metastriata Dermacentor marginatus, Rhipicephalus sanguineus and Hyalomma marginatum are the main species that could bite man, and are involved in the transmission of Borrelia burgdorferi sensu lato, several genoespecies of Rickettsia (R. conorii, R. slovaca, R. aeschlimannii) and Anaplasma phagocytophila.

Aponomma hydrosauri, the reptile-associated tick reservoir of Rickettsia honei on Flinders Island, Australia.

Rickettsia honei is the etiologic agent of Flinders Island (Australia) spotted fever. The tick Aponomma hydrosauri is associated with reptiles and is the arthropod reservoir for this rickettsia on Flinders Island. The rickettsia appears to be maintained in the tick via vertical transmission. Of 46 ticks examined, 29 (63%) were positive for spotted fever group rickettsiae by detection of the citrate synthase gene by a polymerase chain reaction (PCR). From the positive tick samples, seven were sequenced and found to be 100% homologous with R. honei. Of 17 reptiles examined, none had evidence of rickettsiae by PCR or culture of blood.

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

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

Tick infestation of sika deer (Cervus nippon) in the western part of Yamaguchi Prefecture, Japan.

Ticks were collected from 94 sika deer (Cervus nippon) hunted in the western part of Yamaguchi Prefecture, Japan from August to November 1999, and March to July 2000. Haemaphysalis longicornis and H. yeni were the dominant species from April to August, while H. flava and H. megaspinosa were dominant in October, November and March. This is the first report of H. yeni in the mainland of Japan. Small numbers of H. kitaokai, Amblyomma testudinarium and Ixodes ovatus were also recorded.

Expression and immunolocalization of a Boophilus microplus cathepsin L-like enzyme.

Efforts are being undertaken to control tick infestations that cause important economic losses. A cathepsin L-like endopeptidase of Boophilus microplus was expressed in Escherichia coli; the recombinant enzyme was capable of hydrolysing gelatin, tick vitellin and bovine haemoglobin. In this paper we focus on the expression and local of synthesis of this enzyme in the tick. RT-PCR experiments showed that this endopeptidase is transcribed in the gut of partially engorged tick females. In immunoblotting, polyclonal antibodies against the recombinant enzyme reacted with proteins of larvae older than 5 days, of fully and partially engorged female gut. In immunolocalization experiments the enzyme was localized in probable secretory cells of the gut. Based on our findings we postulate that BmCL1 may be involved in haemoglobin degradation in the B. microplus gut. This enzyme may be used as target for the control of this parasite.

Ultrastructural study of the infection process of Rickettsia conorii in the salivary glands of the vector tick Rhipicephalus sanguineus.

This work was designed to study the infection process of Rickettsia conorii in the salivary glands of experimentally infected Rhipicephalus sanguineus ticks. One hundred six uninfected engorged nymphs were intracelomically inoculated with approximately 2 x 10(3) plaque-forming units of a rickettsial suspension. After the molt, unfed and fed adults were dissected, and the salivary glands were extracted and processed for transmission electron microscopy observation. Three different uninfected control groups were used for (1) evaluating the impact of the inoculation procedure, (2) establishing the feeding period of infected ticks, and (3) ultrastructural characterization of the salivary glands. Overall, 75.5% (80 of 106) of the nymphs inoculated with rickettsiae died during the molt or soon after hatching into adult instars; 50% (12 of 24) of the remaining infected adults showed severe malformations compromising their viability. In apparently healthy specimens, time of engorgement was longer. The contrast with the negative control groups was statistically significant, suggesting that R. conorii exerts a strong negative effect on the vector ticks. The ultrastructural study showed that in the salivary glands of infected ticks, rickettsial growth occurs preferentially in central, peripheral, and interstitial acini cells.

Experimental teratogeny in the tick Hyalomma marginatum marginatum (Acari: Ixodida: Ixodidae): effect of high humidity on embryonic development.

The effect of 90% RH on the embryonic development of Hyalomma marginatum marginatum Koch was investigated at 25 degrees C. Under the influence of this factor, 2.1% dead eggs, 13.0% dead embryos, 6.9% abnormally hatched larvae, 0.2% larvae with malformations, and 77.8% normal larvae appeared. The embryos died during the cleavage of nuclei, the formation of the blastoderm, the formation of the germ band and its metamerization, and the differentiation of the leg anlagen. Egg hatch was also inhibited in various phases. Various kinds of anomalies were observed in larvae of Hyalomma m. marginatum. Most teratological changes (70.8%) occurred within the idiosoma. They were hetromorphose (32.6%), oligomely (15.4%), heterosymely (12.3%), symely (1.5%), atrophy (6.1%), and ectomely (3.1%). Anomalies within the gnathosoma occurred rarely (3.1%). As many as 26.2% larvae had composite anomalies (oligomely, heterosymely, atrophy) together. They contained various structures of the gnathosoma or idiosoma. These anomalies decreased the survival rate of the larvae. The investigations showed that during the formation of the blastoderm, the formation of the germ band and its metamerization the embryos have the largest susceptibility of being affected by high humidity. Some anomalies in specimens collected from nature may develop under influence of unfavorable humidity levels.

Pathological effects and reduced survival in Rhipicephalus appendiculatus ticks infected with Theileria parva protozoa.

Pathological effects have been demonstrated in a number of arthropod species as a consequence of parasitic infection. This is usually manifest as reduced arthropod survival and/or fecundity. This paper describes the detrimental effects the protozoan parasite, Theileria parva has on Rhipicephalus appendiculatus ticks. R. appendiculatus ticks were dissected and sectioned at regular intervals during their nymph to adult moult after detaching from a T. parva infected calf, and assessed by light and electron microscopy. The reproductive capacity of the T. parva infected ticks was also compared with that of control, uninfected ticks. The number of T. parva forms seen during the ticks' moult were recorded and showed a substantial reduction as the moult progressed. A non-linear relationship between piroplasm ingestion by the engorged nymph and eventual adult salivary gland infection levels was shown. Tick gut and salivary gland pathology was noted at various stages throughout the moult and correlated with the parasite burdens in the affected organs at those timepoints. The reproductive performance of infected ticks was greatly impaired compared to controls. Infected female ticks had longer bloodmeal engorgement times, reduced bloodmeal volumes, smaller egg batch weights and greatly decreased egg hatching success. The pathological effects are discussed in relation to parasite population dynamics within the ticks and compared with similar examples of pathology evidenced with other parasite infected arthropod species.

Invasion and intracellular development of the human granulocytic ehrlichiosis agent in tick cell culture.

Human granulocytotropic ehrlichias are tick-borne bacterial pathogens that cause an acute, life-threatening illness, human granulocytic ehrlichiosis (HGE). Ehrlichias within neutrophil granulocytes that invade tick bite sites are likely ingested by the vector, to be transmitted to another mammalian host during the tick's next blood meal. Thus, the cycle of replication and development in the vector is prerequisite to mammalian infection, and yet these events have not been described. We report tick cell culture isolation of two strains of the HGE agent directly from an infected horse and a dog and have also established a human isolate from HL60 culture in tick cells, proving that the blood stages of the HGE agent are infectious for tick cells, as are those replicating in the human cell line HL60. This required changes to the culture system, including a new tick cell line. In tick cell layers, the HGE agent induced foci of infection that caused necrotic plaques and eventual destruction of the culture. Using the human isolate and electron microscopy, we monitored adhesion, internalization, and replication in vector tick cells. Both electron-lucent and -dense forms adhered to and entered cells by a mechanism reminiscent of phagocytosis. Ehrlichial cell division was initiated soon after, resulting in endosomes filled with numerous ehrlichias. During early development, pale ehrlichias with a tight cell wall dominated, but by day 2, individual bacteria condensed into dark forms with a rippled membrane. These may become compacted into clumps where individual organisms are barely discernible. Whether these are part of an ehrlichia life cycle or are degenerating is unknown.

Sporogonic development of Hepatozoon americanum (Apicomplexa) in its definitive host, Amblyomma maculatum (Acarina).

Light microscopic observations of the sporogonic development of Hepatozoon americanum are described in its acarine host, Amblyomma maculatum. Laboratory-reared nymphal ticks were fed on 2 dogs infected with H. americanum. Nymphal ticks were sampled daily, starting 3 days after being placed on a parasitemic dog, until 18 days after infestation (PI), and then every 3 or 4 days until replete nymphs molted. Ticks were examined as unstained wet mounts and hematoxylin-eosin-stained paraffin sections. Gametes were found within the gut cells of nymphs 4 and 6 days PI. Although differentiation of gamonts into gametes was not detected, syngamy and sporogony were observed. Sporogony appears to occur wholly within tick gut cells, followed by release of mature oocysts into the hemocoel. The earliest evidence of sporoblast formation was observed 23 days PI and of sporozoite formation, 10 days later. Mature oocysts were first found 42 days PI in newly molted adult ticks. Most adult ticks (>98%) that were dissected contained mature oocysts. Oocysts were multisporocystic, and sporocysts contained a variable number of sporozoites. Oocysts in various stages of development were often seen within the same tick, and the number of mature oocysts ranged from 4 to 573.

African swine fever virus infection in the argasid host, Ornithodoros porcinus porcinus.

The pathogenesis of African swine fever virus (ASFV) infection in Ornithodoros porcinus porcinus was examined in nymphal ticks infected with the ASFV isolate Chiredzi/83/1. At times postinfection (p.i.) ranging from 6 h to 290 days, ticks or dissected tick tissues were titrated for virus and examined ultrastructurally for evidence of virus replication. The ASFV infection rate in ticks was 100% in these experiments, and virus infection was not associated with a significant increase in tick mortality. Initial ASFV replication occurred in phagocytic digestive cells of the midgut epithelium. Subsequent infection and replication of ASFV in undifferentiated midgut cells was observed at 15 days p.i. Generalization of virus infection from midgut to other tick tissues required 2 to 3 weeks and most likely involved virus movement across the basal lamina of the midgut into the hemocoel. Secondary sites of virus replication included hemocytes (type I and II), connective tissue, coxal gland, salivary gland, and reproductive tissue. Virus replication was not observed in the nervous tissue of the synganglion, Malpighian tubules, and muscle. Persistent infection, characterized by active virus replication, was observed for all involved tick tissues. After 91 days p.i., viral titers in salivary gland and reproductive tissue were consistently the highest detected. Successful tick-to-pig transmission of ASFV at 48 days p.i. correlated with high viral titers in salivary and coxal gland tissue and their secretions. A similar pattern of virus infection and persistence in O. porcinus porcinus was observed for three additional ASFV tick isolates in their associated ticks.

Sense organs in post-embryonic stages of Hyalomma marginatum marginatum Koch, 1844 (Acari: Ixodida: Ixodidae). I. Tarsal sensory system.

Light and scanning electron microscopic studies showed the differences in morphology and in size of Haller's organ in larvae, nymphs and adults (females and males) of Hyalomma marginatum marginatum Koch, 1844. The length of the anterior pit setae increases during post-embryonic development. The localization of these setae is the same in all stages. Six setae (one porose seta, two grooved setae, two fine setae, one conical seta) contain anterior pit of various developmental stages. In nymphs and adults more numerous pores appear on the wall surface of porose seta than in the larval stage. The structure of the capsule roof also differs in various developmental stages. Haller's organ of Hyalomma m. marginatum shows great degree of morphological development which is connected with the complicated life cycle and feeding behaviour of this tick species.

Rickettsia peacockii sp. nov., a new species infecting wood ticks, Dermacentor andersoni, in western Montana.

Rickettsia peacockii, a new species of spotted fever group rickettsiae, was identified from Rocky Mountain wood ticks (Dermacentor andersoni) collected in the Sapphire Mountain Range on the eastern side of Bitterroot Valley, Montana. DNA from R. peacockii SkalkahoT (T = type strain) in naturally infected tick tissue was amplified by a PCR assay with primer sets derived from eubacterial 16S ribosomal DNA (rDNA), rickettsial citrate synthase, and 190-kDa surface antigen (rOmpA) genes. Partial 16S rDNA and rOmpA gene sequences exhibited levels of similarity of 99.7 and 93.2%, respectively, with the sequences of the spotted fever agent Rickettsia rickettsii R. By using Gimenez staining, fluorescent antibody tests, a PCR assay, and a restriction fragment length polymorphism analysis, 76 of 115 female ticks (minimal field infection rate, 66.1%) collected between 1992 and 1995 were found to be infected. The organism is passed transstadially and transovarially (minimal vertical transmission rate, 73.3%), and infections are localized in ovarial tissues. Attempts to cultivate R. peacockii were unsuccessful.