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1.
Newly replete nymphal Dermacentor andersoni (principals) were percutaneously exposed to Anaplasma marginale by injection of either intact or lysed infected bovine erythrocytes. Control nymphs were fed on calves with anaplasmosis. The subsequently molted adults were examined for infection by light microscopy, and companion ticks were tested for infectivity by allowing them to feed on susceptible calves. When they fed as adults, both control ticks and percutaneously inoculated principals transmitted A marginale to susceptible calves. Prepatent periods in calves varied according to the method by which nymphs were infected. Colonies of A marginale were found in all ticks that acquired infection by feeding, but colonies were not observed in any ticks exposed percutaneously. The possible developmental cycle of A marginale in artificially infected ticks is discussed.  相似文献   

2.
Infectivity of three Anaplasma marginale isolates for Dermacentor andersoni   总被引：1，自引：0，他引：1  
Three isolates of Anaplasma marginale--Virginia (VAM), Illinois (IAM), and Florida (FAM)--were compared for infectivity for Dermacentor andersoni. The isolates were selected, in part, because of a tail-like appendage that has been demonstrated in the VAM and IAM, but not in the FAM. Ticks were exposed to the isolates as nymphs either naturally by feeding on a calf with anaplasmosis or artificially by percutaneous inoculation with infected bovine erythrocytes. They were examined for infectivity after molting to the adult stage by determining their capability to transmit the disease to susceptible calves and by demonstrating colonies in tick gut sections. Only those ticks exposed to the VAM proved to be infected with A marginale; ticks naturally exposed and those artificially infected with this isolate transmitted the disease to susceptible calves. Colonies of A marginale were observed only in gut tissues of ticks naturally infected with VAM. The IAM (appendage present) and FAM (appendage absent) could not be found in ticks exposed by either method, indicating that factors other than the presence of inclusion appendages may be involved in infection of ticks by A marginale.  相似文献   

3.
Salivary glands from males of 3 Dermacentor species (D andersoni, D variabilis and D occidentalis) that were infected with either the Virginia or Idaho isolate of Anaplasma marginale as nymphs or adults were examined for colonies of A marginale by use of light and electron microscopy. Prior to dissection of salivary glands, exposed ticks were held at 25 C for 15 to 18 days, followed by a 3-day incubation at 37 C. Ticks of 2 species transmitted A marginale to calves; the third tick species was confirmed infected by demonstration of typical colonies in tick gut cells, but transmission was not attempted; Colonies of A marginale were seen with light microscopy in salivary glands of all 3 species of ticks; they were located in acinar cells that contained simple granules. Colonies varied morphologically from small, compact ones to larger structures that contained distinct organisms and often were adjacent to the host cell nucleus. Electron microscopy confirmed that the colonies were rickettsial organisms. Morphologic features of A marginale varied and included reticulated forms, forms with electron-dense centers, and small particles; these various forms were similar to those described previously in midgut epithelial cells of ticks. We believe that the organism seen within tick salivary glands may replicate in the glands before its transmission to the vertebrate host.  相似文献   

4.
The development of Anaplasma marginale was studied in Dermacentor andersoni nymphs after they had fed on a calf with ascending Anaplasma infection. Gut tissues were collected on day 4 of tick feeding, from newly replete (fed) nymphs and on postfeeding days (PFD) 5, 10, 15, 20, and were processed for light and electron microscopy to determine density of A marginale colonies. Homogenates of gut tissues were prepared from nymphs collected on the same days and inoculated into susceptible, splenectomized calves to test for infectivity. Anaplasma colonies were detected in gut cells on PFD 5, 10, 15, and 20. Although colony density appeared to be higher on PFD 10 and 15, differences were not significant. Nymphal type-1 colonies were detected in highest numbers on PFD 5 and 10, transitional colonies were seen in highest numbers at PFD 10 and 15, and nymphal type-2 colonies were observed only on PFD 20. Gut homogenates that were collected from ticks at 4 days of feeding, when newly replete, and on PFD 20 caused anaplasmosis when injected into susceptible calves, but homogenates made from ticks collected on PFD 5, 10, and 15 were not infective. The data indicate that of the colony types of A marginale that develop in replete nymphs, nymphal type-1 and transitional colonies may contain organisms that are not infective for cattle.  相似文献   

5.
The development and transmission of Anaplasma marginale was studied in Dermacentor andersoni males. Laboratory-reared male D andersoni were allowed to feed for 7 days on a calf with ascending A marginale parasitemia. The ticks were then held in a humidity chamber for 7 days before being placed on 2 susceptible calves. Anaplasmosis developed in the calves after incubation periods of 24 and 26 days. Gut and salivary glands were collected from ticks on each day of the 23-day experiment and examined with light and electron microscopy. Colonies of A marginale were first observed in midgut epithelial cells on the sixth day of feeding on infected calves, with the highest density of colonies found in gut cells while ticks were between feeding periods. The first colonies contained 1 large dense organism that subsequently gave rise to many reticulated organisms. Initially, these smaller organisms were electron-lucent and then became electron-dense. On the fifth day after ticks were transferred to susceptible calves for feeding, A marginale colonies were found in muscle cells on the hemocoel side of the gut basement membrane. A final site for development of A marginale was the salivary glands. Colonies were first seen in acinar cells on the first day that ticks fed on susceptible calves, with the highest percentage of infected host cells observed on days 7 to 9 of that feeding. Organisms within these colonies were initially electron-lucent, but became electron-dense.  相似文献   

6.
The development of Anaplasma marginale in midgut epithelial cells was studied in feeding, transmitting adult Dermacentor andersoni ticks. Laboratory-reared ticks experimentally infected as nymphs were allowed to feed from 1 to 9 days on susceptible calves. Gut tissues from ticks were collected on each day they fed (total, 9 days) and were processed for light and transmission electron microscopy. Colonies of A marginale were abundant during the first 6 days of feeding, after which numbers decreased. Colonies were adherent to the basement membrane of gut cells early during feeding, with resultant flattening of the colonies. Colonies also were seen in muscle cells on the hemocoel side of the basement membrane. Morphologic features of A marginale within muscle cells varied and were similar to those observed in gut cells. In addition, however, a large reticulated form in the colonies was observed in muscle cells and appeared to give rise to small particles by budding. Development of A marginale in muscle cells appears to represent an intermediate site of development between those in gut and in salivary glands.  相似文献   

7.
Laboratory-reared Dermacentor andersoni ticks experimentally infected as nymphs with Anaplasma marginale were allowed to feed as adults from 1 to 9 days on susceptible, splenectomized calves to determine when, during feeding, the hematozoan was transmitted from ticks to cattle. In experiment 1, ticks were allowed to feed on calves for 1, 2, 3, 4, 5, or 6 days and anaplasmosis did not result. The same calves were used for experiment 2, and ticks were allowed to feed for 1, 3, 6, 7, 8, or 9 days and anaplasmosis occurred in all calves on which ticks fed for greater than or equal to 6 days. In 2 trials in experiment 3, ticks were allowed to feed on calves for 1 to 9 days. Anaplasmosis developed only in calves on which ticks fed for 7, 8, or 9 days. The prepatent periods shortened with longer tick feeding, and linear regression analysis of combined prepatent periods of both trials of experiment 3 indicated a significant (P = 0.05) slope with an estimated daily decrease of 7.75 days from day 7 to 9 of feeding. There was no apparent correlation between length of tick feeding and severity of clinical signs in those calves that developed anaplasmosis. Seemingly, A marginale can be transmitted to cattle by adult D andersoni ticks no earlier than the 6th or 7th day of feeding.  相似文献   

8.
Previous studies have shown that one Brazilian Anaplasma marginale isolate presents an inclusion appendage (tail), while other isolates do not present such inclusion. Studies on tick transmission have been carried out with tailless isolates but little is known about transmission of tailed isolates by Boophilus microplus. Two splenectomized calves were experimentally inoculated with the tailed A. marginale isolate. During ascending rickettsemia, B. microplus larvae, free from hemoparasites, were fed on the calves and the resulting nymphs, adult males and engorged females were examined by optic and electronic microscopy. No A. marginale colonies were observed in the gut cells of engorged females and the larvae originated from them did not transmit A. marginale to susceptible calves. In addition, no colonies of A. marginale were seen in the gut cells or in salivary glands of adult males and nymphs. These results suggest that B. microplus is not the biological vector for this tailed isolate.  相似文献   

9.
Colonies of Anaplasma marginale in midgut epithelial cells of experimentally infected Dermacentor andersoni were studied in adult ticks 1, 3, and 6 months old. Longevity of the parasite in ticks was assessed by evaluating its infectivity for splenectomized calves; calves were exposed by feeding ticks and by inoculation of tick gut homogenates. Longevity was also evaluated by determining size, type, and density of colonies in male and female ticks. The effect of incubation (2.5 days at 37 C) on colony density was also examined for ticks at each age period. All methods used to assess longevity of A marginale in ticks (tick transmission, calf inoculation, and histologic studies) indicated a decrease of the numbers of organisms in 6-month-old ticks. Furthermore, when tick gut homogenates from 6-month-old nonincubated ticks were not infectious for susceptible calves, incubation of ticks before dissection restored infectivity of homogenates. Colonies of A marginale were detected in gut tissues of 6-month-old ticks that were not infective; therefore, infectivity of ticks could not be confirmed merely by presence of A marginale colonies.  相似文献   

10.
Isolate of Anaplasma marginale not transmitted by ticks   总被引：3，自引：0，他引：3  
The tick-borne transmissibility of 2 isolates of Anaplasma marginale was compared. Dermacentor variabilis were exposed to A marginale as nymphs by feeding on 1 of 4 splenectomized calves during periods of ascending parasitemia (maximum 49% to 81% parasitized erythrocytes) induced by injection of a stabilate. Tick-borne transmission was attempted, using 26 to 224 adult ticks within 30 to 220 days after molting. Adult D variabilis did not transmit an Illinois isolate of A marginale in 7 tick-borne transmission experiments (P = 0.0047), including 2 experiments in which calves were inoculated IV with homogenates of adult ticks. In contrast, a Virginia isolate of A marginale was readily transmitted by the same tick colony. Thus, previously reported morphologic and immunologic differences among A marginale isolates may extend to tick-borne transmissibility. The Virginia and Illinois A marginale isolates had an inclusion appendage that was not a marker for tick transmissibility.  相似文献   

11.
SUMMARY Experiments were done to explore the possible relationship between cattle, Australian dog ticks (Rhipicephalus sanguineus) and Anaplasma marginale. Calves' ears were exposed to larval, nymphal and adult ticks on 8, 9 and 7 occasions, respectively. The immature instars fed readily, but the adults attached very poorly to calves. Transtadial transmission of A. marginale was achieved on 6 occasions from 9 attempts: ticks infected as larvae or nymphs were able to transmit at the subsequent stage or stages. Transovarial transmission was not achieved. Six calves supported more than one infestation of ticks. Attached ticks caused the calves no apparent discomfort and calves developed no noticeable skin reactions. An abattoir survey of 200 hides detected no R. sanguineus.  相似文献   

12.
On each day of feeding on susceptible calves, salivary glands obtained from groups of adult ticks that transmitted Anaplasma marginale were examined for A marginale colonies by use of light microscopy and transmission electron microscopy. On day 8 of feeding, salivary glands were examined, using fluorescein-labeled antibody and methyl green-pyronine stain. Use of fluorescein-labeled antibody consistently revealed small numbers of fluorescent foci in salivary gland acinar cells obtained from ticks that had fed for 8 days. Colonies of A marginale were seen by transmission electron microscopy only in salivary gland acini of male ticks; these colonies could not be identified, using light microscopy, in companion 1-micron plastic sections stained with Mallory stain. Methyl green-pyronine stain, used commonly to detect theilerial parasites in tick salivary glands, did not differentiate A marginale from cytoplasmic inclusions normally found in salivary gland acinar cells.  相似文献   

13.
Two strains of Rhipicephalus sanguineus acquired Ehrlichia canis by feeding as either larvae or nymphs on acutely infected dogs and, in subsequent instars, transmitted the agent to normal dogs. Three strains of R sanguineus transmitted E canis as adults after their larval and nymphal stages fed on infected dogs. More than 400 adult female ticks were fed on infected dogs as larvae or nymphs or both, but none transmitted E canis transovarially.  相似文献   

14.
SUMMARY: Boophilus microplus ticks collected from calves with patent Anaplasma marginale infections were incubated at either 4 to 5°C, 14°C, 22°C, 27°C or 37°C for up to 14 days. Extracts prepared either from larvae, nymphs, immature females, adult males or mixtures of both sexes were infective for 14 of the 16 splenectomised calves inoculated. Extracts either from nymphs or from adult ticks deriving from nymphs moulted in vitro were infective for 11 of 12 nonsplenectomised calves. Possible application of the findings to producing a vaccine strain of A. marginale is discussed.  相似文献   

15.
Bovine babesiosis is responsible for serious economic losses in Uruguay. Haemovaccines play an important role in disease prevention, but concern has been raised about their use. It is feared that the attenuated Babesia bovis and Babesia bigemina vaccine strains may be transmitted by the local tick vector Boophilus microplus, and that reversion to virulence could occur. We therefore investigated the possibility that these strains could be transmitted via the transovarial route in ticks using a Babesia species-specific polymerase chain reaction (PCR) assay. DNA was extracted from the developmental stages of the tick vector that had fed on calves immunized with the haemovaccine. It was possible to detect Babesia DNA not only in adult ticks, but also in their eggs and larvae. In addition, it was shown that calves infested with larvae derived from eggs laid by ticks fed on acutely infected calves, were positive for Babesia using PCR. Caution should therefore be shown with the distribution of the haemovaccine in marginal areas. It is still advisable that suitable tick control measures be used to prevent transovarial transmission and the potential risk of attenuated Babesia reverting to virulence.  相似文献   

16.
The cattle rickettsia Anaplasma marginale is distributed worldwide and is transmitted by about 20 tick species, but only Rhipicephalus simus, a strictly African tick species, has been shown to transmit the vaccine strain of A. centrale. The aim of the present study was to examine transmission of field strains of A. marginale and of the vaccine strain of A. centrale by three tick species -Hyalomma excavatum, Rhipicephalus sanguineus and Rhipicephalus (Boophilus) annulatus - to susceptible calves. Two genetically distinct Israeli field strains of A. marginale, tailed and non-tailed (AmIsT and AmIsNT, respectively), were efficiently transmitted by R. sanguineus, whereas H. excavatum transmitted only the tailed isolate, and R. (Boophilus) annulatus did not transmit A. marginale. None of the three tick species transmitted A. centrale. By means of msp1a primers in PCR assays, amplicons of similar sizes were obtained from either A. marginale-infected calves that were used for acquisition feeding, from R. sanguineus fed on the infected calves, or from calves to which anaplasmosis had been successfully transmitted by these ticks. Although an A. centrale-specific fragment was amplified from salivary glands of R. sanguineus, no transmission to susceptible cattle occurred during 3 months of observation, and anaplasmosis was not induced in splenectomized calves that were subinoculated with blood from calves on which R. sanguineus had fed.  相似文献   

17.
Hemolymph was collected from adult Dermacentor andersoni Stiles that had been infected with Anaplasma marginale Theiler as nymphs. Before hemolymph was collected, the adult ticks were either incubated and unfed at 37 C for 2.5 days or fed for 6 days on sheep. Hemolymph collected from groups of 100 ticks was inoculated into susceptible splenectomized calves. Smears of hemolymph from the same groups of ticks were prepared for examination by fluorescent antibody technique. Hemolymph from incubated ticks caused anaplasmosis in 2 of 4 trials, and hemolymph from feeding ticks caused anaplasmosis in 4 of 4 trials. Moderately fluorescing bodies were demonstrated in some hemocytes from incubated ticks, whereas hemocytes from feeding ticks contained numerous clusters of brightly fluorescing bodies. Fluorescing bodies were not observed in hemocytes from control ticks.  相似文献   

18.
Morphology and development of Cowdria ruminantium in Amblyomma ticks   总被引：2，自引：0，他引：2  
The morphology and development of Cowdria ruminantium have been studied in Amblyomma hebraeum and A. variegatum. Colonies of C. ruminantium have so far been demonstrated microscopically in gut, salivary gland cells, haemocytes and malphighian tubules of infected Amblyomma ticks. Colonies in gut cells were seen in both unfed and feeding ticks but colonies in salivary gland acini were observed only in nymphs that had fed for 4 days. Although the predominant type seen in both tick stages was the reticulated form that appeared to divide by binary fission, electron dense forms were also present. The latter are similar to those forms documented in endothelial cells of the vertebrate host as well as in cell culture. The presence of colonies of C. ruminantium in salivary glands of feeding ticks, along with the demonstration of different morphologic forms of the organism, suggests that a developmental cycle of the organism occurs in its invertebrate host. It is thought that organisms first infect and develop within gut cells. From there subsequent stages continue their development in haemolymph and salivary glands and are then transferred to the vertebrate host during tick feeding. Further studies are needed to completely understand the development of C. ruminantium in ticks and its subsequent transmission by these parasites.  相似文献   

19.
Yin H  Luo J  Guan G  Lu B  Ma M  Zhang Q  Lu W  Lu C  Ahmed J 《Veterinary parasitology》2002,108(1):21-30
Experiments on the transmission of an unidentified Theileria sp. infective for small ruminants by Haemaphysalis qinghaiensis and Hyalomma anatolicum anatolicum were carried out. Three Theileria-free batches of adult, larvae, and nymphs of laboratory reared H. qinghaiensis and Hy. a. anatolicum ticks were infected by feeding them on sheep infected with Theileria sp. The Theileria sp. was originally isolated from adult ticks of H. qinghaiensis, by inoculation of blood stabilates or tick transmission. H. qinghaiensis has been shown to be capable of transmitting the Theileria sp. infective for small ruminants transstadially to sheep and goats. The nymphs developed from the larvae engorged on the sheep infected with the parasite transmitted the pathogen to splenectomized sheep with prepatent periods of 30, 31 days, respectively; but the subsequent adult ticks of H. qinghaiensis derived from the nymphs did not transmit the pathogen to sheep. However, adults developed from the nymphs engorged on the sheep infected with the parasite transmitted the pathogen to sheep with prepatent periods of 24-27 days. The larvae, nymphs and adult ticks derived from female H. qinghaiensis ticks engorged on infected sheep were not able to transmit the parasite transovarially. The same experiments were done with Hy. a. anatolicum, but examination for presence of piroplasma of Theileria sp. from all animals were negative, demonstrating that Hy. a. anatolicum could not transmit the organism to sheep or goats.  相似文献   

20.
Infectivity and antigenicity of Anaplasma marginale from tick cell culture   总被引：1，自引：0，他引：1  
The infectivity and immunogenicity of Anaplasma marginale grown in a tick cell culture from embryonic Dermacentor variabilis ticks were assessed in splenectomized and intact calves, respectively. Culture 1 consisted of the cell line inoculated with midguts of adult ticks infected with the Mississippi isolate of A marginale and dissected 5 to 10 days after repletion and detachment from an experimentally infected calf. Cultures 2 and 3 consisted of the cell line inoculated with midguts of ticks infected with the Virginia isolate of the organism. Inoculum for culture 2 was derived from nymphal ticks dissected 5 to 10 days after repletion and detachment from the infected calf; inoculum for culture 3 was midguts from adult ticks that were fed as nymphs, allowed to molt in the laboratory and dissected 21 to 24 days after molting. In trial 1, cultures 1, 2, and 3 were maintained at pH 6.9 and incubated at 28 C; in trial 2, cultures 1 and 3 were maintained at pH 7.4 and incubated at either 28 C or 37 C. Cultures 1, 2, and 3 failed to induce infection when injected IV and SC into 6 calves in 2 separate trials. Pre-challenge sera from these calves reacted with 2 purified Anaplasma antigens in the ELISA, but failed to react in the complement-fixation test. Results of a trial to use cultures 1 and 3 in combination with an oil-in-water adjuvant to immunize intact calves against A marginale were inconclusive. However, pre-challenge sera from immunized calves reacted with the 2 purified Anaplasma initial body antigens in the ELISA but failed to react in the complement-fixation text.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

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