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PubMed2004

Effects of Anaplasma phagocytophilum infection on the molting success of Ixodes scapularis (Acari: Ixodidae) larvae.

We assessed the effects of sympatric (occupying the same or overlapping geographic areas) and allopatric (occurring in separate geographic areas) isolates of Anaplasma phagocytophilum on the survival of Ixodes scapularis Say larvae that were derived from ticks collected in Bridgeport, CT. Seven isolates of A. phagocytophilum, originating from different geographic regions of the United States, were tested: four isolates from the northeast (Bridgeport, Dawson, Gaillard, and NY-8), two from the Midwest (Webster and Sp-Is), and one from California (MRK). BALB/c mice were infected with each of the seven isolates via exposure to infected I. scapularis nymphs, whereas uninfected nymphs fed upon control mice. Both infected and control mice were infested with uninfected larvae at 1, 2, 3, 4, 6, and 9 wk after nymphal infestation. The molting success in cohorts of infected and uninfected ticks was calculated as the percentage of larvae successfully molting into nymphal stage, and the prevalence of infection in molted nymphs was determined by polymerase chain reaction. In ticks that became infected with the Bridgeport or Sp-Is isolates, the molting success decreased with an increase in the prevalence of infection. Ticks that fed upon mice infected with six allopatric isolates (Dawson, Gaillard, NY-8, Sp-Is, Webster, and MRK) showed significantly lower levels of survival than those fed upon control mice, regardless of the prevalence of infection, whereas in ticks fed upon mice infected with a sympatric isolate (Bridgeport), the overall molting success was similar to the control. Thus, some but not all of the A. phagocytophilum isolates have adverse effects on ticks. Ticks exposed to harmful isolates may experience higher levels of bacterial metabolism, and/or reduced quality of their blood meal, thereby reducing their survival. Noted differences between isolates may be due to the origin of a particular isolate and/or the degree of coadaptation between the pathogen and its vector on the population level.

Anaplasma↗
PubMed2004

Pathogenicity of entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae to Ixodidae tick species Dermacentor variabilis, Rhipicephalus sanguineus, and Ixodes scapularis.

Nymphal and adult ticks from three different tick species, Dermacentor variabilis Say, Ixodes scapularis Say, and Rhipicephalus sanguineus Latrielle, were treated with conidia and blastospores of the entomopathogenic fungi Beauveria bassiana (Bals.) Vuill. and Metarhizium anisopliae Metschnikoff. Dose-response experiments indicated that a critical concentration of fungal spores is required for infection and mortality. Over a 28-d time course, fungal suspensions of either B. bassiana or M. anisopliae at 10(8) conidia/ml resulted in 50-70% mortality in adult I. scapularis and R. sanguineus, but <20% mortality in D. variabilis ticks. R. sanguineus nymphs were highly susceptible to both entomopathogenic fungi, displaying >60% mortality within 14 d postinfection and >90% mortality within 21-28 d postinfection. D. variabilis nymphs also were more susceptible than their corresponding adults, displaying mortalities ranging from 20 to 40% 28 d postinfection. I. scapularis nymphs, however, seemed to be slightly less susceptible than adults (45% mortality, 28 d postinfection). The addition of nutrients to fungal cell suspensions did not have any noticeable effects on mortality toward any of the tick species tested. Significant mortality against D. variabilis adults (approximately 65%) was noted only when B. bassiana fungal cells with growth media carryover were used as the inoculum against the ticks. Entomopathogenic fungi such as B. bassiana and M. anisopliae may have the potential for controlling populations of I. scapularis and R. sanguineus, and under certain conditions D. variabilis. Our results indicate that inoculum conditions can greatly affect successful virulence and subsequent mortality.

Animals↗
PubMed2004

Lack of spatial autocorrelation in fine-scale distributions of Ixodes scapularis (Acari: Ixodidae).

Spatial patterns of Ixodes scapularis Say, the vector of the Lyme disease agent, have been examined at various geographic scales, demonstrating that distributions of these ticks are spatially autocorrelated at both national and state scales. We tested the hypothesis that distributions of nymphal I scapularis ticks at the fine scale of an endemic community also are spatially autocorrelated. Nymphal tick densities were determined by collecting ticks from 51 and 47 wooded residential properties in a southern Rhode Island town in 2002 and 2003, respectively. The average tick density at residences during 2002 was 51.17 ( +/- 46.04) nymphs per hour, with a range of 3-297 and median of 40.82. In 2003, the average tick density was 44.48 (+/- 38.31) nymphs per hour, with a range of 3-153 and median of 36. Semivariance analysis revealed no spatial autocorrelation in tick densities between residences, likely due to the high variability of tick distributions at this scale. Further analysis of drag-sampling data at individual residences by using Lloyd's patchiness index (m*/m) demonstrated a patchy distribution of nymphs. High variability of nymphal I. scapularis densities may greatly affect predicting spatial patterns of ticks at a fine scale.

Animals↗
PubMed2001

Transmission of hepatozoon canis to dogs by naturally-fed or percutaneously-injected Rhipicephalus sanguineus ticks.

Hepatozoon canis is an apicomplexan protozoan parasite of dogs, prevalent in Asia, Africa, and southern Europe. Experimental transmission of H. canis to dogs was performed with laboratory-reared Rhipicephalus sanguineus nymphs that fed on a naturally infected dog or were percutaneously injected with canine blood containing H. canis gamonts. Dogs were inoculated by oral ingestion of adult ticks containing H. canis oocysts. Transstadial transmission of H. canis was recorded, whereas transovarial transmission could not be demonstrated. Oocysts were detected in 85% of the adult ticks that had engorged as nymphs on an infected dog and in 61% of the adult ticks resulting from nymphs injected percutaneously with blood from the same dog. Nine of 12 dogs (75%) inoculated with naturally fed or percutaneously injected ticks became parasitologically positive, and all showed seroconversion. Meronts were initially detected in the bone marrow 13 days postinoculation and gamonts 28 days after infection. The variation in the time of initial detection of parasitemia among infected dogs and the rapid appearance of gamonts in dogs immunosuppressed with corticosteroids suggest that immune mechanisms play an important role in controlling H. canis parasitism. The artificial acquisition of Hepatozoon parasites by percutaneous injection of ticks, demonstrated here for the first time, may serve as a useful tool for studies on transmission, vector-host relationships, and the immunology of infection with Hepatozoon species.

Animals↗
PubMed1995

Prevalence of Borrelia burgdorferi sensu lato infection in Ixodes ricinus in Sweden.

Between 1988-1991, a total of 3,141 Ixodes ricinus ticks, 2,740 adults and 401 nymphs, was collected from different localities in 23 of the 25 provinces of Sweden. The ticks were identified, dissected and examined for the presence of Borrelia spirochetes. Indirect immunofluorescence was performed, using an antiserum obtained from rabbits, immunized with sonicated, whole Borrelia burgdorferi spirochetes isolated from Swedish Ixodes ricinus ticks. Borrelia-positive I. ricinus were found in all 23 provinces. The prevalence of infection in adults ranged from 3% in Jämtland to 23% in Södermanland. In nymphs, the infection prevalence ranged from 0% in 9 provinces to 15% in Södermanland. A significantly greater proportion of the adult ticks were found to be positive for Borrelia in the southern and central parts of Sweden as compared to the northern part (Norrland). No significant difference in prevalence could be demonstrated between the western and eastern parts of Sweden. On average, 10% of the nymphs and 15% of the adult I. ricinus were positive for Borrelia. Of 41 non-I. ricinus ticks, none was positive for Borrelia. This study shows that Borrelia burgdorferi sensu lato is present throughout the distributional area of I. ricinus in Sweden. This should lead to increased awareness of signs and symptoms compatible with Lyme borreliosis in persons living in or visiting areas where I. ricinus is present.

Animals↗
PubMed2006

Hosts, seasonality and geographic distribution of the South African tortoise tick, Amblyomma marmoreum.

The tortoise tick Amblyomma marmoreum was collected from large numbers of reptiles and other animals during the course of numerous surveys conducted in South Africa. A total of 1229 ticks, of which 550 were adults, were recovered from 309 reptiles belonging to 13 species, with leopard tortoises, Geochelone pardalis being the most heavily infested. The 269 birds sampled harboured 4901 larvae, 217 nymphs and no adult ticks, and the prevalence of infestation was greatest on helmeted guineafowls, Numida meleagris. Only two larvae were recovered from 610 rodents, including 31 spring hares, Pedetes capensis, whereas 1144 other small mammals yielded 1835 immature ticks, of which 1655 were collected from 623 scrub hares, Lepus saxatilis. The 213 carnivores examined harboured 2459 ticks of which none were adult. A single adult tick and 6684 larvae and 62 nymphs were recovered from 656 large herbivores, and a total of 4081 immature ticks and three adults were collected from 1543 domestic animals and 194 humans. Adult male and female A. marmoreum were most numerous on reptiles during January and February, and larvae during March. The largest numbers of larvae were present on domestic cattle and helmeted guineafowls in the Eastern Cape Province during March or April respectively, whereas larvae were most numerous on helmeted guineafowls, scrub hares and the vegetation in north-eastern Mpumalanga Province during May. In both provinces nymphs were most numerous between October and December. Amblyomma marmoreum appears to be most prevalent in the western regions of the Western and Eastern Cape and Free State provinces, and the north-eastern regions of the Northern Cape, KwaZulu-Natal, Mpumulanga and Limpopo provinces.

Animals↗
PubMed2006

Birds as hosts of immature ixodid ticks in Free State Province, South Africa.

The objective of this study was to determine the species spectrum of ixodid ticks infesting birds in Free State Province, South Africa. To this end a large number of birds belonging to several species were examined for ticks and a total of 180 birds belonging to 39 species at 17 localities were infested, and ticks belonging to eight species were recovered. The immature stages of only two, namely Amblyomma marmoreum and Hyalomma marginatum rufipes, were sufficiently prevalent and numerous to safely assume that they regularly use birds as hosts. Helmeted guineafowls, Numida meleagris, were the most heavily infested and one harboured a total of 319 larvae and four nymphs. Amongst the other species an eastern clapper lark, Mirafra fasciolata, was infested with 69 larvae and a nymph, but no other bird harboured more than 40 ticks. The larvae and nymphs of H. m. rufipes were most numerous on birds from April to August.

Animals↗
PubMed1976

Human babesiosis on Nantucket Island: transmission by nymphal Ixodes ticks.

In order to identify potential vectors of human babesiosis (Babesia microli) in southern Massachusetts, I attempted to transmit the infection via nymphal ticks of that species found to be most abundant on reservoir hosts (Peromyscus leucopus) in nature. Mice were collected at frequent intervals throughout a year in a known enzootic focus on Nantucket Island, and ticks were removed by hand. Ticks of only two species were present; larvae and nymphs of Ixodes scapularis were about 10 times as numerous as were those of Dermacentor variabilis. Accordingly, I. scapularis were used in attempts to transmit a strain of Babesia derived from a human infection recently acquired near the study site. Larvae were permitted to feed on an infected hamster and nymphs derived from these larvae were placed on each of 11 non-infected hamsters. All but one hamster became infected. Nymphs reared from larvae that had attached to a non-infected hamster did not transmit babesiosis to other hamsters. These results suggest that I. scapularis serves as a vector of babesios-s on Nantucket hamsters. These results suggest that I. scapularis serves as a vector of babesiosis on Nantucket Island.

Animals↗
PubMed1989

Transstadial and horizontal transmission of Rift Valley fever virus in Hyalomma truncatum.

We exposed Hyalomma truncatum and Rhipicephalus appendiculatus to Rift Valley fever (RVF) virus in order to assess the possible role of these ticks as enzootic/epizootic RVF vectors. The virus replicated in H. truncatum after intracoelomic inoculation, and a minimum transmission rate of 17% was achieved after 15 days intrinsic incubation. The virus persisted at least 58 days in these ticks. Virus was also shown to pass transstadially from inoculated H. truncatum nymphs to adults, with peak viral titers reaching 10(3.5) plaque-forming units (PFU) in adult males after they were provided with bloodmeals. Virus was recovered from adult females 121 days after they were inoculated as nymphs. Viral titers peaked in inoculated male ticks after dropping off a host (mean titer = 10(4.3) PFU). RVF virus was not detected in pools of eggs and larval progeny from 11 infected female H. truncatum. H. truncatum larvae and nymphs did not become infected after ingesting greater than 10(2.0) PFU while feeding on a RVF viremic hamster. The number of infected specimens declined rapidly after RVF virus was inoculated into R. appendiculatus adults, and virus was undetectable 12 days post-inoculation.

Animals↗
PubMed1990

A comparative study of the infection thresholds of Thogoto virus in Rhipicephalus appendiculatus and Amblyomma variegatum.

Infection thresholds of Thogoto virus in 2 ixodid tick species, Rhipicephalus appendiculatus and Amblyomma variegatum, were compared. Thogoto virus has been isolated from naturally infected R. appendiculatus and A. variegatum in Central Africa, where both commonly parasitize the same hosts. No significant difference was found between the infection thresholds of Thogoto virus in the 2 species. The percentage of nymphs of both species infected by feeding on viremic hamsters was directly correlated with the time between host inoculation and tick engorgement. The blood titers in infected hamsters increased each day during the 3-4 day viremia until the hamsters died. The percentage of nymphs infected correlated with the viremic titer on the final day of engorgement (the time of maximum blood uptake). The 5% infection threshold for nymphs of R. appendiculatus and A. variegatum was estimated as 10(2.8) and 10(2.7) plaque forming units (PFU)/ml viremia, respectively. The prevalence of infection approached 100% for blood titers greater than 10(6.3) PFU/ml and greater than 10(7) PFU/ml, respectively. The apparent bloodmeal size of the 2 species differed by 8-fold and suggested that, in terms of the number of PFU ingested, R. appendiculatus was more susceptible than A. variegatum to per os infection by Thogoto virus.

Animals↗
PubMed1997

Duration of Borrelia burgdorferi infectivity in white-footed mice for the tick vector Ixodes scapularis under laboratory and field conditions in Ontario.

The duration of Borrelia burgdorferi infectivity in white-footed mice (Peromyscus leucopus) experimentally inoculated or infested with infected Ixodes scapularis nymphs was evaluated. Infectivity was assessed by infesting these mice with unfed I. scapularis larvae at 7, 21, 35 and 49 days post-inoculation (DPI) or post-infestation (PI). At 7 DPI, B. burgdorferi was transmitted from 18 of 24 syringe-inoculated mice and all three tick-infected mice to I. scapularis larvae which fed upon them. However, at 21, 35 and 49 DPI, significantly fewer mice were infective. Borrelia burgdorferi was isolated from tissues of 14 of 22 syringe-inoculated mice about 56 DPI, and from all three tick-infected mice. However, the level of agreement between xenodiagnosis and bacterial culture was no greater than would be expected by chance alone. We also determined if B. burgdorferi infectivity of mice varied in relation to periods of tick feeding in the field. White-footed mice were trapped during April, July and August 1993 from two habitats on Long Point peninsula (Ontario, Canada), where B. burgdorferi is endemic. Mice from each habitat were infested with laboratory-reared I. scapularis larvae. Ticks from each mouse were subsequently examined by immunofluorescent assay for B. burgdorferi infection and mice were cultured for B. burgdorferi. None of 3577 I. scapularis larvae fed on 62 mice captured within the cottonwood dune habitat were infected with B. burgdorferi, although it was isolated from six of these mice. Within the maple forest habitat, 0/24, 8/21 (38%) and 1/21 (5%) mice transmitted B. burgdorferi to I. scapularis larvae during April, July and August, respectively. Most mice from the maple forest with B. burgdorferi-positive tissues (14/21) were collected during July, although the level of agreement between xenodiagnosis and tissue culture was poor. Because B. burgdorferi infectivity in mice appears to be of short duration, overwintered I. scapularis larvae and nymphs may have to feed upon infected hosts at the same time of year in order for a cycle of B. burgdorferi infection to be maintained on Long Point. Infected I. scapularis nymphs, rather than persistently infected vertebrate hosts, likely serve as the overwintering "reservoir" for B. burgdorferi on Long Point.

Animals↗
PubMed1996

Feeding of Hard Ticks In Vitro: New Perspectives for Rearing and for the Identification of Systemic Acaricides.

Experiments on in vitro feeding of the hard ticks Ixodes ricinus, Boophilus microplus, Amblyomma variegatum and Amblyomma hebraeum are described. An in vitro test for systemic acaricides is presented. Work started with a feeding chamber continuously supplied with new blood. It proved too susceptible to fungal contamination and not efficient enough. Simple feeding units made of honey jars with an inner glass tube were far more practical. Reinforced silicone membrances or baudruche membrances impregnated with glue were stretched across the bottom end of the tube. Weekly open-collected bovine blood from the slaughter house, where it is considered as discard, served as nutrient and changed 1-3 times a day. The feeding jars were held in a waterbath (38 degrees C). The blood contained microbicides. Attachment of ticks on the membranes was induced with combinations of host hair, conspecific tick faeces, bovine hair extract and synthetic aggregation attachment pheromone mixtures (Amblyomma). Larvae of the one-host cattle tick A. microplus were bred in vitro through the nymphal to the unfed adult stage. Females gained half of the natural body mass and laid eggs. The life-cycle of A. hebraeum was completed in vitro by consecutive feeding of all life-stages (larvae, nymphs, adults) on silicone membranes. In adult B. microplus, A. variegatum and A. hebraeum the reproductive capacity was strongly impaired, possibly in consequence of the low quality of the blood. A suboptimal in vitro nutrition was more fatal for the fertility than for the moult of ticks, as demonstrated by the good results for larvae and nymphs, particularly those of A. hebraeum. The toxicity of the systemic acaricide Ivermectin(R) for nymphs of A. hebraeum was confirmed using the in vitro feeding method. This method offers new in vitro possibilities for tick rearing as well as for tests with systemic acaricides, antifeedants and repellents. It allows experiments on transmission of pathogens and with radioactive markers.

Journal Article↗
PubMed2001

Bionomics of ticks collected from Sinai Peninsula: 2- abundance, attachment sites, and density estimators of ticks infesting Arabian camels.

Ten camels were examined monthly from January to December 1999, in Beer Lehfen North Sinai Gavernorate. A total of 5468 adult ticks of 6 species and subspecies of genus Hyalomma; H. dromedrii, H. ipmeltatum, H. a. excavatum, H. a. anatolicum, H. schulzei, and H. marginatum rufipes, in addition to 115 Hyalomma nymphs' species were collected. Of these, the first 4 types represented about 96.2% of the total collection. The infestation rate was higher during the period from March to November. The average monthly infestation rate was 22.78+/-3. The large number of the adult ticks were concentrated on tail, brisket, anus, and udder which totaled 68.2%. Attachment sites of males and females were not significantly correlated in most species. Nymphs were localized in few sites, whereas 91.6% of the total nymphs were attached to hump, neck, head (ear), and side. H. dromedarii, H. impeltatum, and H. a. excavatum were found on most of the body sites, tail, brisket, udder, and anus, totaling 79.9%. Males exceeded females in all sites, and were alone on neck and legs. Females were the only stage collected from udder. Both sex of H. a. anatolicum were collected from tail. H. schulzei and H. m. rufipes were concentrated in brisket, udder, anus, and tail.

Animal Diseases↗
PubMed2001

The efficacy of co-feeding as a means of maintaining Borrelia burgdorferi: a North American model system.

Although research on co-feeding as a means of maintaining tick-borne pathogens has focused chiefly on viruses, recent interest has been directed toward the importance of this phenomenon in maintaining the Lyme disease spirochete, Borrelia burgdorferi. In the current study, an experimental model was developed to determine under what conditions immature co-feeding ticks exchange B. burgdorferi using the principal North American vector (Ixodes scapularis) and reservoir (Peromyscus leucopus) species. Experiments conducted with the density of ticks likely to be encountered in nature (8 nymphs & < 40 larvae) demonstrated that no co-feeding larvae became infected; in contrast, horizontal transmission infected 30-64% of test larvae. Only the highest densities of ticks (40 nymphs & > 200 larvae) produced infected larvae (5%) upon co-feeding of larvae and nymphs. An important role for co-feeding in the ecology of Lyme disease in North America has yet to be established.

Animals↗
PubMedDate not supplied

[Biologic effect of diflubenzuron on Blattella germanica (Dictyoptera: Blattellidae)].

The Amejeiras strain of Blatella germanica (Dictyoptera: Blattellidae) kept in lab conditions since 1994 and susceptible to arpocarb, malathion and cipermethrin insecticides, was studied. This strain was treated with 4 diflubenzuron (Dimilin OMS 1804) concentrations supplied by feeding nymphs at their first stage of development, with the purpose of determining their effect on the survival, phenotype and period of nynmphal development of this species. The dosage-mortality line of regression was determined and the values of CE50 = 0.042% and CE95 = 0.357% were obtained. Sublethal effects were observed in the nymphs treated with the 4 tested concentrations whereas the morphogenetic effects in adult insects only occurred when they were exposed to higher concentrations (0.25% and 0.4%). The nymph development stage showed a highly significant increase when the diflubenzuron concentration was raised. (F = 11.64; p < 0.001).

Animals↗
PubMed1975

The life history of Plagioporus shawi (McIntosh 1939) (Trematoda:Opecoelida), an intestinal parasite of salmonid fishes.

Podocotyle shawi is transferred to the genus Plagioporus. The miracidium develops and hatches in 11 to 14 days at 22 to 25 C. The operculate snail, Lithoglyphus virens, serves as first intermediate host. Mother and daughter sporocysts develop, the latter producing cotylomicrocercous cercariae within 90 to 130 days. Cercariae encyst in the amphipod, Hyalella azteca; stonefly nymphs of the genus Arcynopteryx; mayfly nymphs of the genera Heptagenia and Paraleptophlebia; chironomid larvae of the genera Chironomus, Polypedilum, Phaenopsectra, Ablabesmyia, and Psectrocladius and caddis larvae of the genera Brachycentrus, Limnephilus, and Hydropsyche. Metacercariae 60 to 100 days old were fed to young steelhead trout, Salmo gairdneri, and partially developed specimens of P. shawi were recovered 26 days later. Stonefly nymphs are believed to be the most important second intermediate host in the natural environment. The parasite seems to be restricted to the Pacific Northwest of the United States and has been reported from the silver salmon, Oncorhynchus kisutch; kokanee, O. nerka; cutthroat trout, Salmo clarki; steelhead trout, S. gairdneri; and the mountain whitefish, Prosopium williamsoni.

Animals↗
PubMed2001

[Feeding and defecation of Rhodnius (hemiptera: Reduviidae) fed human blood].

Feeding and defecation behavior of Rhodnius prolixus Stal, 1859, R. robustus Larrousse, 1927, R. neivai Lent, 1953 and R. pictipes Stal, 1872, artificially fed on human blood, were studied under laboratory conditions. In all species, first instar nymphs did not defecate in the first 30 minutes after feeding. R. pictipes did not accept artificial feeding but fed directly on humans. Nymph and adult R. prolixus had a higher defecation index (DI) than other species; third instar nymphs had the highest DI = 1.62. In all instars, most individuals accepted the food in 3 Pounds minutes and finished feeding in less than 15 minutes.

Animals↗
PubMed2003

[Biological characteristics and spatial distribution of Chorthippus dubius population on high mountain grassland].

Based on rearing observations and surveys in Ganjia High-Mountain Grassland, Xiahe County, Gansu Province, the occurrence period, ingestion capacity, spatial pattern, and dynamics of Chorthippus dubius were studied. The results showed that this grasshopper had only one generation in a year. Its eggs wintered in the soil, and in the next year, they began to hatch from the last ten days of May to the first ten days of June. The hatching peak took place from the middle ten days to the last ten days of June. The majority of the nymphs possessed 4 instars, and about 23% of them possessed 5 instars. The developmental duration of the nymphs underwent about 70 days, and the longevity of the adults lasted for 42 days. The ingestion capacity of the nymphs was 368. 3 mg, and that of the adults was 743.8 mg. The spatial pattern of 1-2 instars belonged to an aggregated distribution, and that of 3-5 instars belonged to even and random distribution.

Animals↗