Lice and ticks of the eastern rufous mouse lemur, Microcebus rufus, with descriptions of the male and third instar nymph of Lemurpediculus verruculosus (Phthiraptera: Anoplura)

Sucking lice and ticks were collected from live-trapped eastern rufous mouse lemurs, Microcebus rufus Geoffroy, in and around the periphery of Ranomafana National Park, southeastern Madagascar, from 2007 to 2009. Samples of 53 sucking lice (Insecta: Phthiraptera: Anoplura) and 28 hard ticks (Acari: Ixodidae) were collected from 36 lemur captures representing 26 different host individuals. All of the lice were Lemurpediculus verruculosus (Ward) (6 males, 46 females, 1 third instar nymph). Only the holotype female was known previously for this louse and the host was stated to be a "mouse lemur." Therefore, we describe the male and third instar nymph of L. verruculosus and confirm M. rufus as a host (possibly the only host) of this louse. All of the ticks were nymphs and consisted of 16 Haemaphysalis lemuris Hoogstraal, 11 Haemaphysalis sp., and 1 Ixodes sp. The last 2 ticks listed did not morphologically match any of the Madagascar Haemaphysalis or Ixodes ticks for which nymphal stages have been described.     

Susceptibility of Amblyomma americanum to natural and experimental infections with Theileria cervi

One hundred fifty Amblyomma americanum were examined between March and September 1986 from Cookson Hills Wildlife Refuge in eastern Oklahoma (USA). Of these ticks, 11% (17 of 150) were infected with Theileria cervi. Field-collected nymphal ticks had an 8% (3 of 37) prevalence of infection averaging 1.0 infected acini/nymph. Female ticks had a 16% prevalence of infection averaging 1.6 infected acini/female; T. cervi was not observed in salivary glands of field-collected male ticks. When laboratory reared A. americanum nymphs were allowed to feed on experimental white-tailed deer (Odocoileus virginianus) with varying T. cervi parasitemias (less than 1, 2, 6 and greater than 20%), only ticks which fed on deer with parasitemias greater than 1% became infected. Although prevalence and intensity of infection varied in the infected ticks, there was no significant difference in prevalence of infection between males and females. However, females did acquire significantly greater intensities than males. The data from these studies confirm that T. cervi overwinters in A. americanum and suggests that the prevalence, intensity and abundance of infection of T. cervi in ticks is influenced by the parasitemia of the deer host. Furthermore, fawns may play a more important role in the epidemiology of T. cervi transmission than do adult deer because of the coordination between tick activity patterns and deer fawning.     

Monitoring Theileria parva infection in adult Rhipicephalus appendiculatus ticks

A rapid method is described for preparing and staining salivary glands of Rhipicephalus appendiculatus ticks infected with Theileria parva. The technique, involving the use of a modified methyl green pyronin stained minimizes the risk of losing material and allows examination of stained glands within minutes of preparation. The technique was applied in a series of studies in which ticks were either infected with T. parva under different conditions, or maturation of parasites in adult ticks was stimulated by different means. When nymphal ticks were fed on the ears of cattle the subsequent infection rate of the adult ticks showed no correlation with the parasitaemia of the cattle at the time of nymphal engorgement. There was no difference in infection rates between adult ticks in which parasite maturation had been stimulated either by incubation at 37 degree C or by feeding on rabbits. However, parasite maturation took about 1 day longer in incubated ticks than in rabbit-fed ticks. Female ticks were consistently more highly infected than males, both in terms of the percentage of ticks infected and the mean number of infected acini/tick. Ticks were infected with T. parva by injection of nymphs with parasitaemic bovine blood, but the resultant adult infection was lower than that in ticks which had been infected naturally by feeding on cattle.     

Babesia microti: prolonged survival of salavarian piroplasms in nymphal Ixodes dammini

We determined how long Babesia microti survive in the salivary glands of nymphal Ixodes dammini. Of those ticks held at 21 C, the proportion with demonstrable piroplasms decreased from 95%, prior to 20 weeks post-larval-feeding (p-l-f), to less than 80% at 42 weeks p-l-f. Similarly, the number of infected acini decreased significantly. Nymphal I. dammini were kept alive for as long as 1 year, by transferring them to 4 C, at 20 weeks p-l-f. The proportion of infected ticks at 52 weeks p-l-f was less than half of the proportion of infected nymphs examined prior to 20 weeks p-l-f, and only 1/6 as many acini were infected. Ultrastructural observations of salivary glands from ticks at 44 weeks p-l-f revealed that B. microti parasites in older ticks remain in the sporoblast meshwork phase; such parasites rarely differentiated into sporozoites. Degenerating parasites containing autophagic vacuoles were also observed in older ticks.     

Differential detachment from resting hosts of replete larval and nymphal Ixodes ticks

To determine whether replete subadult Ixodes ticks detach more frequently from resting than from active hosts, diverse rodents and lizards were caged in an apparatus designed to record the ticks' sites of detachment relative to the resting site of the host. Replete larval Ixodes ricinus and Ixodes dammini accumulated mainly beneath the resting places of the mice (Apodemus agrarius and Peromyscus leucopus) most frequently parasitized in nature. Although nymphal I. ricinus similarly detached where these mice rested, nymphal I. dammini detached more randomly. When lizards were used as hosts, both subadult stages of I. ricinus tended to detach away from their main resting sites; these ticks detached from squirrels more randomly. Detachment ratios for other rodent hosts, that are abundantly infested by the larvae of these ticks in nature (Apodemus flavicollis and Clethrionomys glareolus), could not be derived because nymphs generally failed to attach. Our observations are consistent with reports that both subadult stages of I. dammini, but not the adult, feed on the same kind of nest-dwelling hosts and that the host range of I. ricinus is less focused. Detachment of mouse-feeding larvae from resting mice promotes subsequent nymphal attachment to conspecific hosts, and the absence of such behavior among nymphs facilitates access of the resulting adults to deer.     

Infection of Ixodes scapularis ticks with Rickettsia monacensis expressing green fluorescent protein: a model system

Ticks (Acari: Ixodidae) are ubiquitous hosts of rickettsiae (Rickettsiaceae: Rickettsia), obligate intracellular bacteria that occur as a continuum from nonpathogenic arthropod endosymbionts to virulent pathogens of both arthropod vectors and vertebrates. Visualization of rickettsiae in hosts has traditionally been limited to techniques utilizing fixed tissues. We report epifluorescence microscopy observations of unfixed tick tissues infected with a spotted fever group endosymbiont, Rickettsia monacensis, transformed to express green fluorescent protein (GFP). Fluorescent rickettsiae were readily visualized in tick tissues. In adult female, but not male, Ixodes scapularis infected by capillary feeding, R. monacensis disseminated from the gut and infected the salivary glands that are crucial to the role of ticks as vectors. The rickettsiae infected the respiratory tracheal system, a potential dissemination pathway and possible infection reservoir during tick molting. R. monacensis disseminated from the gut of capillary fed I. scapularis nymphs and was transstadially transmitted to adults. Larvae, infected by immersion, transstadially transmitted the rickettsiae to nymphs. Infected female I. scapularis did not transovarially transmit R. monacensis to progeny and the rickettsiae were not horizontally transmitted to a rabbit or hamsters. Survival of infected nymphal and adult I. scapularis did not differ from that of uninfected control ticks. R. monacensis did not disseminate from the gut of capillary fed adult female Amblyomma americanum (L.), or adult Dermacentor variabilis (Say) ticks of either sex. Infection of I. scapularis with R. monacensis expressing GFP provides a model system allowing visualization and study of live rickettsiae in unfixed tissues of an arthropod host.     

Borreliae in Ixodes ricinus ticks feeding on humans

A total of 298 Ixodes ricinus (L.) ticks (Acari: Ixodidae) feeding on humans in the Czech Republic were tested for borreliae (Borrelia burgdorferi sensu lato) by darkfield microscopy between 1997 and 2003. A majority (68%) of the supplied I. ricinus ticks were nymphs, 25% were females and 7% were larvae. Overall, 20% of 74 examined females and 9% of 203 examined nymphs (but none of 21 examined larvae) were infected with borreliae. The proportion of ticks with a high infection load (>100 spirochetes) was 4% in females and 2% in nymphal I. ricinus. During the year, the highest numbers and proportions of infected nymphal and female ticks were taken from humans in June. Detection of borreliae in the ticks feeding on humans might be helpful in the prophylaxis of Lyme borreliosis.     

Role of an aquaporin in the sheep tick Ixodes ricinus: Assessment as a potential control target

Ticks undergo tremendous osmoregulatory stress as they take on up to 100 times their body weight in blood, returning about 75% of the ingested water and ions via their saliva into the host. We postulated that water channels, or aquaporins, involved in this mass water transport might be good targets for acaricide development. An aquaporin (IrAQP1) identified in the sheep tick, Ixodes ricinus, was present only in tissues involved in mass water flux, namely the gut, rectal sac and especially abundant in the salivary glands. IrAQP1 was localised by in situ hybridisation in specific cell and acini types, possibly Type III acini, but absent from the type I acini that are responsible for rehydration of ticks in the non-feeding phase. Gene knockdown of IrAQP1 in isolated salivary glands completely inhibited dopamine-stimulated secretion. Further, IrAQP1 knockdown adult females had 50% reduced body weight gains over the first 5 days feeding on an artificial feeding apparatus and 21% at the point of engorgement on hosts. Haemolymph osmolarity was increased in the IrAQP1-knockdown ticks. Importantly, the blood volume ingested per body weight was reduced by 30%. Overall, it would appear that water passage from the gut to the saliva was disrupted and tick guts were simply too “full” to ingest more blood. However, double-stranded RNA interference of IrAQP1 did not affect mortality of the ticks which successfully fed to detachment at day 9. Overall, our data indicate that IrAQP1 plays a pivotal role in blood meal water handling through the gut and salivary gland, and although its disruption by double-stranded RNA interference dramatically affects feeding performance, ticks remained feeding on the host with subsequent potential pathogen transmission and, therefore, IrAQP1 is not a suitable candidate target for tick control.     

Vectorial capacity of North American Ixodes ticks.

Ixodes dammini, the vector of Lyme disease and babesiosis, is distributed in various locations in the northeastern quadrant of the United States and nearby Canada. The life cycle of this tick, which includes larval, nymphal, and adult stages, spans at least two years. The tick over-winters between larval and nymphal feeding. Horizontal transmission of pathogens is facilitated by a feeding pattern in which both the larval and nymphal stages feed on the white-footed mouse, Peromyscus leucopus, and by a seasonal pattern of activity in which nymphs precede larvae. The species range appears to have expanded from a single island location, and has invaded new sites since the 1940s, some as recently as 1980. This increased abundance appears to be related to the increased abundance of deer, the preferred host of the adult stage. I. muris predominated in coastal Massachusetts before I. dammini became abundant, but is probably now extinct. I. scapularis, which is present in the southern U.S., is a poor vector of mouse parasites because about 90 percent of these immature ticks feed on lizards. To the extent that horizontal transmission occurs, we suggest that mice serve as the principal reservoir for the Lyme spirochete as well as Babesia microti.     

Review The ecology of ticks transmitting Lyme borreliosis

The main vectors of Borrelia burgdorferi sensu lato, the cause of Lyme borreliosis, are ixodid ticks of the Ixodes persulcatus species complex. These ticks, which occur throughout the northern temperate zone, have very similar life cycles and ecological requirements. All are three-host ticks, with the immature stages mainly parasitizing small to medium-sized mammals and birds and the adult females parasitizing large mammals such as deer, cattle, sheep and hares. The host-seeking stages show a distinct seasonality, which is regulated by diapause mechanisms and there appear to be major differences in this respect between the Old World and New World species. Most cases of human borreliosis are transmitted in the summer by the nymphal stages, with the exception of the Eurasian species, I. persulcatus, in which the adult females are mainly responsible. The ticks acquire the spirochaetes from a wide variety of mammals and birds but large mammals do not seem to be infective, so that t icks that feed almost exclusively on large mammals, for example in some agricultural habitats, are rarely infected. The greatest tick infection prevalences occur in deciduous woodland harbouring a diverse mix of host species and the diversity of the different genospecies of B. burgdorferi s.l. is also greatest in such habitats. There is evidence that these genospecies have different host predilections but, apart from the fact that I. persulcatus does not seem to be infected by B. burgdorferi sensu stricto, they do not seem to be adapted to different tick strains or species. © Rapid Science Ltd. 1998     

Saliva-activated transmission (SAT) of Thogoto virus: dynamics of SAT factor activity in the salivary glands ofRhipicephalus appendiculatus,Amblyomma variegatum,andBoophilus microplus ticks

Thogoto (THO) virus is transmitted from infected to uninfected ticks when co-feeding on uninfected guinea-pigs, even though the guinea-pigs do not develop a detectable viraemia. This form of non-viraemic transmission is potentiated by a factor (s) secreted by the saliva of ticks and hence has been termed saliva-activated transmission (SAT). The synthesis of the SAT factor by the salivary glands of three ixodid tick species was determined by placing uninfected nymphal ticks on guineapigs that were subsequently inoculated with a mixture of THO virus and salivary gland extract (SGE) derived from one of the tick species. SAT factor activity was measured by determining the number of nymphs that acquired THO virus. For the three-host ixodid species,Rhipicephalus appendiculatus andAmblyomma variegatum, maximum enhancement of THO virus transmission was observed when salivary glands were derived from uninfected, female ticks that had fed for a period of 6 or 8 days, respectively. In contrast, when salivary glands were derived form uninfected femaleBoophilus microplus, a one-host ixodid tick species, enhancement of THO virus transmission was observed throughout the tick feeding period. Thus, the natural feeding behaviour of ticks appears to be an important factor in determining the relative importance of these vectors in mediating SAT.     

Molecular individuality and adaptation of the tick Rhipicephalus appendiculatus in changed feeding environments

The tick Rhipicephalus appendiculatus Neumann (Acari: Ixodidae) naturally infests many host species. However, the mechanisms that enable it to feed on such a wide range of hosts are unclear. One possibility is that a tick population maintains molecular (genotypic and/or phenotypic) diversity among individuals such that individuals vary in their competency in taking bloodmeals under different feeding conditions. As a first step in testing this hypothesis, we showed that the polymorphism of salivary gland proteins, previously demonstrated in unfed ticks, was maintained during feeding on guinea-pigs. We then compared feeding performance under standard laboratory rearing conditions: one instar (adults or nymphs) feeding on guinea-pigs, with three changed conditions: (1) two instars (adults and nymphs) feeding together on guinea-pigs; (2) one instar (adults or nymphs) feeding on hamsters; and (3) two instars (adults and nymphs) feeding together on hamsters. The mean engorged weight of adult females was significantly reduced under all changed conditions, indicating that most of the adult individuals were significantly challenged by the changed conditions. However, some individuals achieved successful engorgement, indicating competence to the changed condition, and demonstrating variation in adaptive ability among individuals. Engorged females produced egg masses positively correlated to the engorged weights. More interestingly, the correlation coefficient (R) increased when feeding condition was changed. This may lead to more efficient selection for population adaptation under the changed conditions. As the feeding success of ixodid ticks depends on the efficiency of the cocktail of immunomodulatory saliva, the relevance of the polymorphism of salivary gland proteins and host adaptation is discussed.     

Vector competence ofRhipicephalus sanguineus andDermacentor variabilis for American isolates ofBabesia gibsoni

To determine the identity of the tick vector of enzooticBabesia gibsoni in California, two common ixodid ticks were allowed to engorge uponB. gibsoni infected dogs. Sporozoites were observed in the salivary glands of prefed nymphalRhipicephalus sanguineus ticks that fed as larvae onB. gibsoni-infected dogs. A higher proportion (31%) of nymphal ticks that prefed on an uninfected dog for 48 hours contained sporozoites in their salivary glands than did ticks which had fed for 24 hours (13%). Sporozoites were not observed in the salivary glands of prefedR. sanguineus nymphs which were derived from the eggs of adult females that fed on an infected dog, in adults that were fed as nymph on an infected dog, or in the nymphal and adult uninfected controls.Dermacentor variabilis ticks appeared not to become infected. Although attempts to transmitB. gibsoni to susceptible, splenectomized dogs were unsuccessful,R. sanguineus would appear to be the most likely tick vector to maintain this piroplasm in California. This study was supported by grants from the Companion Animal Disease Laboratory, School of Veterinary Medicine, University of California, Davis.     

The effect of the physiological age of Dermacentor marginatus (Ixodidae) ticks on their infection with and the infiltration of the tick-borne encephalitis virus into the saliva

The decisive effect of physiological age of ticks on the infection of their saliva was revealed by means of parenteral infection of D. marginatus females with tick-borne encephalitis virus. The virus was not found in the saliva of young individuals of instar II. Maximum number of cases of saliva infection was recorded in mature ticks of instar III (50%). It was established that the infection of saliva did not depend on the amount of virus in the tick's body. Less susceptibility to the virus of young individuals, associated probably with the way of infection, was noted. Under light microscopy there were observed no significant age differences in salivary glands of ticks of instars II and III. The infection of saliva of young individuals is, apparently, opposed by the barrier of fat body on the way of virus to salivary glands, depending on the age of ticks. The barrier is supposed to have an influence under natural transphase infection of ticks.     

Regeneration of Haller's sensory organ in two species of hard ticks of the genus Haemaphysalis (Acari: Ixodidae)

A study of Haller's organ regeneration in nymphs and adults of Haemaphysalis turturis and parthenogenetic females of H. longicornis, from which the forelegs had been amputated during the previous instar, revealed structural changes in regenerated organs. The adult regenerates reestablished atavistic structural features, while the nymphal regenerates retained larval features, which is typical of regenerates of two other genera examined previously (Ixodes and Hyalomma). Data on regeneration of Haller's sensory organ testify to an ancient character of the genus, standing closely to the base of the phylogenetic tree of hard ticks.     

Ixodes scapularis salivary gland protein P11 facilitates migration of Anaplasma phagocytophilum from the tick gut to salivary glands

Ixodes ticks harbour several human pathogens belonging to the order Rickettsiales, including Anaplasma phagocytophilum, the agent of human anaplasmosis. When ticks feed on A. phagocytophilum-infected mice, the pathogen enters the ticks' gut. The bacteria then migrate from the gut to infect the salivary glands of the ticks and are transmitted to the next host via the saliva. The molecular mechanisms that enable the migration of A. phagocytophilum from the gut to the salivary glands are poorly understood. Here we show that a secreted tick protein, P11, is important in this process. We show that P11 enables A. phagocytophilum to infect tick haemocytes, which are required for the migration of A. phagocytophilum from the gut to the salivary glands. Silencing of p11 impaired the A. phagocytophilum infection of tick haemocytes in vivo and consequently decreased pathogen infection of the salivary glands. In vitro experiments showed that P11 could bind to A. phagocytophilum and thus facilitate its infection of tick cells. This report provides new insights into A. phagocytophilum infection of ticks and reveals new avenues to interrupt the life cycle of Anaplasma and related Rickettsial pathogens.     

Amblyomma cajennense (Acari: Ixodidae): salivary gland cells of partially engorged females ticks and the production of lipid by their mitochondria

Morphologically, the salivary glands of ticks are paired structures consisting of a secretory and an excretory portion, lacking a reservoir for the storage of the secretion. The secretory portion is composed in females by cells that form acini classified into the types I, II, and III. The excretory possess a major duct, from which arise several intermediate ducts that then subdivide to form the canaliculi or acinal tubules, which end at the acini from where they collect the secretion. The present study describes the ultrastructural changes that occur in the mitochondria of cells of the acini I, II, and III in the salivary glands of partially engorged females of the Cayenne tick Amblyomma cajennense. The results show that this organelle exhibits completely disarrayed crests due to the presence of lipidic material inside the matrix and between the crests, thus demonstrating their participation in the production of the lipids that would be used structurally by the cells. These organelles with ultrastructural changes were denominated derived mitochondria.     

Life cycle of Amblyomma cooperi (Acari: Ixodidae) using capybaras (Hydrochaeris hydrochaeris) as hosts

The life cycle of Amblyomma cooperi was evaluated under laboratory conditions testing different host species. Larval infestations were performed on chickens (Gallus gallus) and capybaras (Hydrochaeris hydrochaeris). Nymphal infestations were performed on G. gallus, H. hydrochaeris, guinea pigs (Cavia porcellus) and wild mice (Calomys callosus). Infestations by adult ticks were performed only on capybaras. All free-living stages were observed in darkness at 27 degrees C and RH 85%. Capybaras were significantly (p < 0.05) the most suitable hosts for immature ticks, with the highest larval (63.6%) and nymphal (48%) recovery. Larval and nymphal feeding and premolt periods were significantly different (p < 0.05) between ticks fed on different host species. Male nymphs showed premolt period significantly shorter (p < 0.05) than female nymphs. The overall sex ratio of adult ticks was 0.92:1 (M:F). Infestations by adult ticks on capybaras yielded more than 76% of engorged female recovery. Only three out of 33 engorged females fed on capybaras did not lay fertile eggs. The life cycle of A. cooperi in laboratory, reported for the first time, was completed in an average period of 189.4 days. During the premolt period, all A. cooperi engorged nymphs secreted distinct blackish drops, which seem to be inherent to this species. Our results, associated data in the literature, confirm the high suitability of capybaras for the adult stage of A. cooperi and also indicate this animal species as a primary host for immature stages of A. cooperi in nature. On the other hand, the results of larval and nymphal infestation on chickens and guinea pigs suggest that birds and wild guinea pigs, which are also present in the distribution area of A. cooperi in South America, could be potentially infested by A. cooperi immature stages in nature.