Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Nymph”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,081 records · Page 60Linked to original sources
PubMed1988

First isolation of Borrelia burgdorferi, the agent of Lyme borreliosis, from Ixodes ricinus (Acari: Ixodidae) in Berlin (West).

In 1984, two human cases of tick-borne Lyme borreliosis with considerable neurologic involvement were reported in Berlin (West). The diagnosis of Lyme borreliosis was serologically confirmed. The ticks which had transmitted the Borrelia were from Berlin (West). In the autumn of 1985, 156 ticks were collected in forests of Berlin (West) for the cultural detection of spirochetes by using BSK II medium. Three strains of spirochetes were isolated (from a pooled sample of two nymphs, and samples of one nymph and one female tick, respectively). These isolates were identified as Borrelia burgdorferi by means of SDS-PAGE, Western blot (using monoclonal antibody H 5332), microscopic agglutination test and electron microscopy. Investigations with the electron microscope showed that cells of two isolates (strains 2/B45 and 3/B56) had 8 flagella inserted at each end. The cells of the third isolate (strain 1/B29) had 9 flagella inserted at each end. This type had not been observed before.

Animals↗
PubMed2002

Seasonal dynamics of ticks (Acari: Ixodidae) on horses in the state of São Paulo, Brazil.

Natural tick infestations were assessed every 14 days on horses over a 2-year period. Amblyomma cajennense adult ticks were counted individually, without detachment from the horses. Larvae and nymphs of A. cajennense were collected using a rubber scraper that scratched engorged immature ticks from the host. Adult females of Anocentor nitens larger than 4mm length were counted on the horses. Blood samples were also obtained from the horses every 14 days and macroclimatic data were obtained for the study period. Infestations of A. cajennense demonstrated distinct peaks of activity for each of the three parasitic stages over each 12-month period, showing a 1-year generation pattern. Larvae predominated from April to July and nymphs from June to October. Adults predominated from October to March with a greater number of adult males than females. Although other studies on seasonal dynamics in the states of Rio de Janeiro and Minas Gerais were performed with the free-living stages of A. cajennense on pastures, the present study in the state of São Paulo, performed with the parasitic stages of A. cajennense on horses, showed similar results to those observed in other states. Infestations by A. nitens demonstrated distinct peaks of activity of adult females (>4 mm), suggesting different tick generations during the year. Infestation with A. nitens was much higher in the first year than the second year which may have been related to horse nutritional status and stocking rate. Although several climatic variables showed statistical significant correlation (r) with tick counts, the determination coefficients (R(2)) were always lower than 0.40, suggesting that any single significant variable (i.e. mean temperature) would not explain the tick distribution pattern over the year. The highest peaks of A. nitens females (>4 mm) were significantly associated with decrease in horse packed cell volumes (R(2)=0.603). The ears and the perineum, tail and groin region accounted for around 70% of all A. nitens females counted on the horses.

Animals↗
PubMed2003

Survey of ixodid tick species on domestic cats in Japan.

Various species of ixodid ticks, attached to domestic cats in Japan, were identified in spring (April to June) and autumn (September to November). In the spring, a total of 282 ticks, including 61 larvae, 70 nymphs, 127 females and 24 males were collected from 126 cats. Of these, 264 were identified up to the species level. In the spring, Haemaphysalis longicornis was the most frequently (39.7%, 50/126) found tick species on feline hosts, followed by Ixodes ovatus (35.0%, 44/126), Ixodes nipponensis (15.9%, 20/126) and Haemaphysalis flava (9.5%, 12/126). Small numbers of Haemaphysalis megaspinosa, Haemaphysalis japonica, Ixodes persulcatus, Ixodes granulatus and Amblyomma testudinarium were also recovered. H. longicornis was the most frequently found tick species on cats around riversides or river basins, while I. ovatus and I. nipponensis were more frequently found on cats kept near woodland or related areas. I. nipponensis was more frequently found on castrated males. No major statistical differences in the frequency of tick attachment among sex, age or hair length for the three major tick species were found. Of 205 ticks including 173 (84.4%) larvae, 27 (13.2%) nymphs, 4 (2.0%) females and 1 (0.5%) male recovered from 62 cats in autumn, only 32 (15.6%) were identified. Most of the larvae were fully- or partly-engorged Haemaphysalis spp., and it was difficult to identify them further by morphological characterization.

Age Factors↗
PubMed1993

Studies of the prevalence of Coxiella burnetii, the agent of Q fever, in the foothills of the southern Bavarian Forest, Germany.

In studies carried out in 1991 in the foothills of the southern part of the Bavarian Forest, in the district of Freyung/Grafenau, ticks and small mammals were collected and examined for the presence of Coxiella (C.) burnetii and sera of small mammals and cattle investigated for antibodies against this rickettsia. A total of 1716 imagines and nymphs of Ixodes ricinus were collected by flagging and 892 larvae and nymphs of the same tick species removed from small mammals. In addition to 1095 serum samples from cattle, 326 specimens of nine species of small terrestrian mammals were examined. Neither in ticks nor in rodents, C. burnetii was detected, however, in 17 of 21 localities, seropositive cattle were found. Altogether, 12% of all 1095 heads of cattle tested were seropositive for C. burnetii antibodies. These serological results indicated a wide dissemination of C. burnetii in cattle of the region investigated, but there was no indication of a natural focus. As in other areas of Europe, an independent natural cycle of the agent involving cattle only is assumed to occur in this region.

Animals↗
PubMed1993

The woodmouse (Apodemus sylvaticus) as a reservoir of tick-transmitted spirochetes (Borrelia burgdorferi) in The Netherlands.

In three widely separated locations in the Netherlands, woodmice (Apodemus sylvaticus) were trapped, examined for ticks and subjected to xenodiagnosis for the detection of tick-transmitted spirochetes (Borrelia burgdorferi). During the spring and summer, an average of 2.4 Ixodes larvae/mouse (n = 170) was observed, but the true numbers were probably greater. The numbers of nymphs could be determined more accurately and amounted to 0.46 nymphs/mouse. The percentage of mice that were infected with tick-transmitted spirochetes was 47% (n = 45), 29% (n = 58) and 0% (n = 64) for the three locations respectively. The absence of spirochete-infected mice in location 3 is puzzling because spirochete-infected I. ricinus nymphs were collected (infection rate up to 11%) in the same location during the subsequent spring. Sexually active mice were more frequently infected with spirochetes than juveniles and non-sexually active ones. On location 1, the island of Texel, a sample of mice was also caught during the subsequent winter and subjected to xenodiagnosis. The results indicate that B. burgdorferi survives the winter in the vector tick rather than in the reservoir rodents.

Aging↗
PubMed1998

Risk of infection with Borrelia burgdorferi sensu lato for a host in relation to the duration of nymphal Ixodes ricinus feeding and the method of tick removal.

The objectives of the present study were to investigate the risk of B. burgdorferi s.1. (Bb)-transmission by I. ricinus-nymphs to a host (i) after different periods of feeding, and (ii) with regard to the particular method of tick removal. On each of 72 Mongolian gerbils 3 tick nymphs taken from a highly infected batch were allowed to feed in a small capsule. Feeding ticks were removed 16.7, 28.9, 47.0, and 65.2 hrs post-attachment. In each of these 4 groups 3 sub-groups with 6 gerbils each were deticked by (a) pulling ticks out with forceps without any pretreatment, (b) pulling ticks out after 3 min of intensive squeezing, and (c) applying nail polish to ticks 1.1 hrs before removal. The infection status in each gerbil was subsequently determined by larval xenodiagnosis. All gerbils with ticks removed > or = 47 hrs post-attachment were found to be infected. After 16.7 hrs as well as after 28.9 hrs of tick feeding, approximately 50% of the gerbils had acquired a transmissible infection, thus Bb-transmission to a host may even occur in the early phases of I. ricinus feeding. There is no evidence from this study that the tick removal method used has any significant influence on a host's Bb-infection risk.

Animals↗
PubMed1998

Expression of outer surface proteins A and C of Borrelia afzelii in Ixodes ricinus ticks and in the skin of mice.

Several studies have described changes in the expression of proteins, especially of OspA and OspC, of B. burgdorferi sensu stricto during tick feeding. In this study, the expression of OspA and OspC of B. afzelii in unfed and feeding I. ricinus nymphs and in the subsequent adults was followed by means of the immunofluorescence test. Spirochaetes expressing OspA and OspC were observed in 70% and 80%, respectively of the unfed nymphs. In feeding and in fully engorged ticks, spirochaetes expressed OspC, while OspA disappeared 24 hours after the beginning of the blood meal. Spirochaetes expressing OspC in salivary glands were observed in one engorged tick. After molting, in unfed adults spirochaetes again expressed OspA and OspC but did so less frequently (6% and 13%, respectively). The mouse strain (AKR/N or BALB/C) on which ticks had their infectious blood meal influenced OspC expression in the following tick stage. In the skin of AKR/N mice, at the tick feeding site, B. afzelii expressed OspC only, as was shown by immunostaining.

Animals↗
PubMed2002

Rhodnius heme-binding protein (RHBP) is a heme source for embryonic development in the blood-sucking bug Rhodnius prolixus (Hemiptera, Reduviidae).

We have previously shown that Rhodnius prolixus' eggs and hemolymph are pink due to the presence of the hemeprotein Rhodnius heme-binding protein (RHBP). In the hemolymph it functions as an antioxidant. Nevertheless, its function in eggs has not been determined. Here we present evidence that RHBP is a source of heme for embryonic development. RHBP content decreases during embryogenesis, but the total heme content of eggs remains unchanged. Biliverdin, the product of heme degradation, is not detectable in late embryos. The activity of the heme-synthesizing pathway is low throughout embryogenesis and rises sharply after nymphs' hatching. Heme-radiolabeled eggs were produced and, at the day of hatching, nymphs were dissected. The presence of radiolabeled heme in their carcass is an indication that heme reutilization is occurring. The only animal known to reutilize heme in significant levels is the cattle tick Boophilus microplus, which cannot synthesize its own heme. Diversely, Rhodnius can synthesize its own heme but, in the context of embryogenesis, heme demand seems to be supplied by the programmed release of heme form RHBP. This behavior indicates that in Rhodnius, we might have a highly unusual profile: heme is both synthesized and reutilized.

Animals↗
PubMed2003

Changes in lipophorins are related to the activation of phenoloxidase in the haemolymph of Locusta migratoria in response to injection of immunogens.

In Locusta migratoria, activation of phenoloxidase in the haemolymph in response to injection of laminarin is age-dependent: being absent in fifth instar nymphs and newly emerged adults, and only becoming evident four days after the final moult. This pattern of change in phenoloxidase activation correlates with the pattern of change in the concentration of apolipophorin-III (apoLp-III) in the haemolymph. Injection of a conspecific adipokinetic hormone (Lom-AKH-I) has no effect on the phenoloxidase response in nymphs or newly emerged adults but, in adults older than four days, co-injection of the hormone with laminarin prolongs the activation of phenoloxidase in the haemolymph: a similar enhancement of the response to laminarin is observed in locusts that have been starved for 48 h but not injected with AKH-I. During most of the fifth stadium, injection of laminarin results in a decrease in the level of prophenoloxidase in the haemolymph; an effect that is not observed in adults of any age. Marked changes in the concentration of apoLp-III, and the formation of LDLp in the haemolymph, are observed after injection of laminarin (or LPS) and these are remarkably similar, at least qualitatively, to those that occur after injection of AKH-I. The involvement of lipophorins in the activation of locust prophenoloxidase in response to immunogens is discussed.

Animals↗
PubMed1998

Characterization and cDNA cloning of a hemoprotein in the salivary glands of the blood-sucking insect, Rhodnius prolixus.

Three major red hemoproteins, named RpSG I, II (identical with prolixin-S) and III, in the salivary glands of the blood-sucking insect, Rhonius prolixus, show homology in N-terminal amino acid (AA) sequences, and are immunologically related. We focussed on one of these proteins, RpSG-I, in this paper. RpSG-I in fresh salivary gland extract was separated into two components (Ia and Ib) by isoelectric focussing gel electrophoresis. Absorption spectra of RpSG-Ia and Ib showed Soret peaks at 400 nm and 420 nm, respectively, suggesting that they are nitric oxide (NO)-unbound and -bound hemoproteins and function as NO-carriers. RpSG-I is stage-specific in appearance, being absent in 3rd and 4th instar nymphs, appearing and increasing gradually in 5th (last) instar nymphs after engorgement, and present in the adult stage. We purified RpSG-I from salivary gland extract by size exclusion and ion exchange HPLCs. It is a single electrophoretic band with an absorption peak at 400 nm, representing the NO-unbound molecule. Full-size cDNA of RpSG-I was cloned by screening with a specific polyclonal antibody from a salivary gland cDNA library. Sequence analysis of RpSG-I cDNA showed an open reading frame encoding a signal peptide (23 AA) and mature protein (179 AA) of 19,778 daltons. The deduced N-terminal AA sequence of the RpSG-I was identical with that of the hemoprotein reported as nitrophorin-3 (Champagne et al., 1995).

Amino Acid Sequence↗
PubMed1999

Purification and characterization of the lysozyme from the gut of the soft tick Ornithodoros moubata.

The gut of the adult soft ticks Ornithodoros moubata displays high lytic activity against the bacteria Micrococcus luteus. The activity differed in the range of two orders of magnitude among individual animals and increased on average 4 fold during the first week following ingestion. In homogenates of first instar nymphs the activity was much lower increasing exponentially as nymphs neared the first molt. The protein responsible for this activity was purified out of gut contents of adult ticks by means of affinity adsorption on magnetic-chitin followed by two chromatography steps on cation exchange FPLC column MonoS. The homogeneous active protein has a mass of 14006 +/- 20 Daltons as determined by MALDI-TOF mass spectrometry. The N-terminal amino-acid sequence of this protein is K-V-Y-D-R-C-S-L-A-S-E-L-R with the highest similarity to the lysozyme from liver of rainbow trout and to lysozymes from digestive tracts of several mammals. The motif DRCSLA is specific for the digestive lysozymes of several dipteran insects. Based on this evidence, we have identified the protein as the tick gut lysozyme. The tick gut lysozyme has a pI near 9.7 and retains its full activity after treatment at 60 degrees C for 30 minutes. The pH optimum of the tick lysozyme was in the range from pH 5-7. Only marginal activity could be detected at pH > 8 which raises the question about the function of lysozyme in anti-bacterial defense in the environment of the tick gut.

Amino Acid Sequence↗
PubMed2002

Phospholipid and triacylglycerol fatty acid composition of major life stages of sunn pest, Eurygaster integriceps (Heteroptera: Scutelleridae).

Phospholipid and triacylglycerol fatty acid compositions of whole animals from all life stages of Eurygaster integriceps, including eggs, nymphs, pre-diapausing adults and diapausing adults, were determined. The fatty acid composition of total lipids of their food, wheat, was also determined. The major components of the insects and their food were the expected C16 and C18 saturated and unsaturated fatty acids. Since fatty acid compositions of third-stadium nymphs were not similar to the profiles of their food, most likely, dietary fatty acids are modified by the insect. The fact is that the food does not provide C20 polyunsaturated fatty acids, but the insect tissue lipids include these components. We suggest biosynthesis of the C20 components by elongation/desaturation of C18:2n-6, an abundant component of the diets. We also show differences in fatty acid profiles from each of the life stages.

Aging↗
PubMed2004

Vectors of tick-borne diseases and epidemiological situation in Latvia in 1993-2002.

During the period of 1993-2002 an increase and the remarkable changes in the incidence of tick-borne encephalitis (TBE) and Lyme borreliosis (LB) as well as annual activities of vector species were noticed. The highest increase of TBE morbidity in Latvia has been observed in 1994 and 1995, and less expressed also in 1998 which was followed by a significant decrease during subsequent years. Whereas the highest peak of LB morbidity has been noticed in 1998 with only a minor decrease during subsequent years. Two epidemiologically significant Ixodes tick species are common in Latvia. Ixodes ricinus L. spread in the western and central part of Latvia; but rarely and in small numbers also in the eastern part. Ixodes persulcatus P. Sch. seems to dominate only in the eastern part of the country. The changes of seasonal and annual activities of I. ricinus were observed in two types of monitoring sites--sylvatic and peridomestic, located in the central part of Latvia. Observations of I. persulcatus were made in the eastern districts. Comparing geographically the Tick-borne diseases (TBD) incidence data for three tick distribution regions (I. ricinus dominated, I. persulcatus dominated and mixed regions), it was observed that the trend of annual changes in LB incidence during the last decade is almost of the same kind for all regions. Whereas TBE incidence extremes in 1994 and 1995 were observed almost only in I. ricinus dominated region. The annual field-collected adult tick infection rate with TBE virus (TBEV) from 1993 to 2002 for I. ricinus adults varied between 1.7% and 26.6% and for I. persulcatus--between 0% and 37.3%. The infection level in ticks removed from humans was much higher and from 1998 to 2002 surpassed 30%. TBEV investigations of removed adults and nymphs in 2002 discovered a high TBEV prevalence also in I. ricinus nymphs (43%). Typing of TBE virus isolated from ticks and patient serum samples in collaboration with German and Swedish virologists revealed that all three TBEV subtypes were co-circulating in Latvia. The mean annual tick infection rate with Borrelia burgdorferi s.l. analysed by means of a nested polymerase chain reaction of OspA gene fragment during the period of 1999-2001 was 18%-38% for I. ricinus adults and 25%-51% for I. persulcatus adults. Typing of Borrelia-positive DNA samples indicated that B. afzelii was dominant in Borrelia-positive I. ricinus (64.9%) and I. persulcatus (81.2%) followed by B. garinii (I. ricinus: 24.3%; in I. persulcatus: 14.5%). Investigations of Ehrlichia phagocytophila genogroup (by nested PCR targeted the 16S rRNA gene) revealed the presence of Ehrlichia sp. in I. ricinus from the central part of Latvia. Obtained data on TBD vectors and the epidemiological situation during the last decade indicates the complex impact of different factors influencing TBE and LB morbidity in Latvia.

Animals↗
PubMed2004

Tick-borne encephalitis (TBE) in Germany--epidemiological data, development of risk areas and virus prevalence in field-collected ticks and in ticks removed from humans.

In Germany, 100-300 autochthonous clinical TBE cases have been recorded annually. There are high-risk areas in Bavaria and Baden-Wuerttemberg and ongoing low-risk areas in Hesse, Thuringia, and the Rhineland-Palatinate and single cases in Saxony. In order to be able to evaluate the epidemiological changes described here, it must be mentioned that a new definition of TBE risk areas was introduced on the district level in 1998 in Germany and in 2001 with the new Infection Protection Act (Infektionsschutzgesetz) which states that TBE is a notifiable disease. This led to the replacement of earlier surveillance systems and to many changes to data collection. In 1998 63 country and town districts were TBE risk areas, in 2001 79 and in 2002 86. There were new risk districts within Bavaria and Baden-Wuerttemberg and outside these regions in Thuringia, Hesse and the Rhineland-Palatinate. An interesting trend was observed in TBE epidemiology. The TBE incidence in Bavaria and Baden-Wuerttemberg has been stable on a high level for years; outside these areas it has steadily been climbing (Odenwald, Thuringia). On the basis of epidemiological data on TBE from the eastern part of Germany since 1960, it is obvious that major changes in virus activity in TBE risk areas also occurred in the past, the explanation of which has remained a matter for speculation. The epidemiological situation in the different risk areas for TBE in Germany was found to vary considerably, if one considers the surveillance data of the last 40 years. 1. Establishment of completely new low-risk areas. 2. Reactivation of formerly active areas with endemic latency. 3. High-risk areas with stable viral activity over long periods. 4. High-risk areas which have expanded and merged with low-risk areas. 5. High-risk areas which have developed into endemic areas or become inactive. High-risk TBE areas from 1960-1975 (i.e. Mecklenburg-Western Pomerania) have since completely disappeared. There were, at the same time, high-risk areas in Thuringia which had only become latent and have now obviously become active again. The Odenwald demonstrated growing virus activity in the 1990s. These changes in TBE activity in German risk areas over more than the last 40 years are presented schematically. This ongoing number of risk areas is certainly linked to the notification obligation and greater public awareness. Nevertheless, any effects of ecological and climatic changes on the natural foci cannot be ruled out nor can changes in human leisure behaviour. Local weather conditions also have a major effect on the TBE incidence. Warm and dry summers may cause low tick activities, rainy summers may lead to low exposure rates of human beings. Even changes in forms of agricultural production prompted by different political structures probably have an impact as do economic constraints which may lead to lower vaccination and higher exposure rates. Regular, systematic virus prevalence measurements from 1997 to 2002 in field-collected ticks in German high-risk areas do not indicate any risk increase nor do they suggest a downward trend. Studies on virus prevalence in questing versus partially engorged ticks indicate that we neither exactly know nor understand the real quantitative relations between the virus and the host. In a first study, virus prevalence in Ixodes ricinus removed from humans was examined. Humans which were exposed in some districts near Passau in Bavaria. In the autumn of 2001, virus prevalence of unengorged free-living nymphs (n = 820) in this area was 0.38 (0.08-1.1)% and of adults (n = 90) 1.17 (0.03-6.38)%. Surprisingly, virus prevalence in partially engorged ticks from the same area collected during the same period was significantly higher (nymphs, n = 86, 6.9% and adults, n = 129, 9.3%). Virus-positive partially engorged ticks were only found in districts known as risk areas. Nucleotide and deduced amino acid sequence data of the PCR products have confirmed the presence of virus prototype Neudoerfl only.

Animals↗
PubMed2000

Detection of three genospecies of Borrelia burgdorferi sensu lato in Ixodes ricinus ticks collected in different regions of Poland.

Ixodes ricinus ticks, collected in 1996-1998 in different Polish woodlands, were examined to assess the frequency of the occurrence of Lyme borreliosis-associated genospecies. A total of 568 samples of individual adults and 162 samples of individual (n =48) and pooled (of 2 to 7) samples of nymphs were analysed by the polymerase chain reaction (PCR) for Borrelia burgdorferi sensu lato. Spirochetes were detected in 130 adult ticks (22.9%) and in a minimum of 32 (5.3%) nymphs. Further identification of 153 B. burgdorferi s.l.-positive samples by nested PCR using three species-specific primers revealed the occurrence of B. afzelii, B. burgdorferi sensu stricto and B. garinii. Both single-species and mixed infections were noted. Single-species infections were observed in the majority of samples (n = 83/153; 54.2%). Within this group B. afzelii was found in 38/153 samples (24.9%), followed by B. burgdorferi sensu stricto (n = 23/153; 15.0%) and B. garinii (n = 22/153; 14.4%). Dual infections with B. burgdorferi s.s. and B. afzelii were detected in 17/121 (14.0%) adults, while both B. burgdorferi s. s./B. garinii and B. afzelii/B. garinii coinfected 11/121 (9.1%) adult ticks. Triple infection with B. burgdorferi s.s., B. afzelii and B. garinii was noted twice (1.6%). In general, B. afzelii was found in 72/153 (47.1%) tick samples and was the predominant species. B. burgdorferi s. s. and B. garinii were detected in a total of 60/153 (39.2%) and 51/153 (33.3%) samples, respectively. Although, 21 (13.7%) samples were infected by B. burgdorferi s.l. genospecies undetectable by the primers used, results of our study confirm that Lyme borreliosis pathogenic genospecies are well established in tick populations throughout Poland.

Animals↗
PubMed1977

Babesia bigemina in Kenya: experimental transmission by Boophilus decoloratus and the production of tick-derived stabilates.

A Babesia-free batch of laboratory reared Boophilus decoloratus ticks was infected with a Kenyan strain of Babesia bigemina by feeding them on a steer infected by inoculation of a blood stabilate. The engorged female ticks showed developing stages of B. bigemina in their haemolymph and subsequently their progeny transmitted the parasite to a susceptible splenectomized steer. Attempts were made to produce stabilates from pre-fed larvae and nymphs derived from infected batches of B. decoloratus. Only the stabilates derived from the nymphs pre-fed either on cattle or rabbits produced B. bigemina infection when inoculated intravenously into susceptible cattle.

Animals↗
PubMed1980

The development of Theileria=Cytauxzoon taurotragi (Martin and Brocklesby, 1960) from eland in its tick vector Rhipicephalus appendiculatus.

The sexual cycle of Theileria taurotragi was identified in the gut lumen of replete Rhipicephalus appendiculatur nymphs maintained at 28 degrees C which had fed on eland with rising parasitaemias. Macro- and micro-gametes developed from ring-form piroplasms within 24 h after repletion. The microgamonts were elongate with 2 or more lateral projections. The nuclei of the microgamonts divided into 4 and the microgamonts differentiated into 4 thread-like microgametes each with a central nucleus. Round macrogametes developed at the same time and stages indicative of the fusion of the macro- and microgametes were observed after 48 h. The resultant zygotes were detected in the gut wall cells by day 4, many being rounded and vacuolated with a peripheral nucleus. By day 7 the zygote cytoplasm became dense and they lay in clusters still within the cells. Binucleate zygotes were observed at this stage. The zygotes increased in size and by day 12 began to transform into kinetes by invagination. By the time the nymphs moulted into adults (about day 14), the kinete straightened to a broad anterior end and a tapering posterior with a mean length of 22.1 micrometer. Kinetes were detected in the haemolymph by day 16. By day 20 the kinetes had penetrated the salivary gland acinar cells where they underwent schizogony until the infected acinar cells were filled with multinucleated sporoblasts. The nuclei of the infected acinar cells became greatly enlarged soon after penetration of the kinete. Division of the sporoblast nuclei was stimulated by feeding of the adult ticks. From the 2nd day of attachment of the ticks to rabbits the sporoblasts underwent a process of schizogony to produce cytomeres. Each nucleus of the cytomere divided to produce several small nuclei which differentiated into uninucleated sporozoites.

Animals↗
PubMed1987

Development and survival of Theileria parva parva in Rhipicephalus appendiculatus exposed in the Trans-Mara, Kenya.

Nymphal Rhipicephalus appendiculatus (Trans-Mara) were fed on a steer infected with a Theileria parva parva (Kilae 1) stock isolated from an indigenous steer in the Trans-Mara Division, Kenya, which had a high piroplasm parasitaemia. A total of 5000 engorged nymphs which had dropped on one day were enclosed in elongated nylon bolting silk tubes in groups of 200-300 and were transported immediately to the Trans-Mara where they were suspended vertically in the grass cover with one end touching the ground. Over 98% of the nymphs moulted into adult ticks and 50% moult occurred by day 28 after exposure. The ticks showed over 80% survival up to 308 days post-exposure but thereafter showed a marked mortality so that only 22.5% of the ticks were alive after 439 days. Theileria parasites were detected in the salivary glands by day 35 post-exposure and infection rates and levels increased markedly between 180 and 235 days post-exposure. Thereafter, the infection rates and levels generally decreased. Groups of ticks were triturated and the resultant supernatant fluid inoculated into pairs of susceptible cattle, and these proved infective from day 44 to 145 after exposure. Three subsequent attempts to induce infections with supernatant fluid were unsuccessful. From 294 days after exposure, groups of 50 ticks were applied to cattle and caused lethal T. p. parva infections up to 439 days post-exposure. Climatic observations showed a relatively even monthly rainfall as well as mean maximum and minimum monthly temperatures.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗