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PubMed1999

WHO Expert Committee on Biological Standardization.

This report presents the recommendations of a WHO Expert Committee commissioned to coordinate activities leading to the adoption of international requirements for the production and control of vaccines and other biologicals and the establishment of international biological reference materials. The report starts with a discussion of general issues brought to the Committee's attention and provides information on the status and development of reference materials for various antibodies, antibiotics, antigens, blood products and related substances, cytokines and growth factors and other substances for which the Committee has discerned a need for international reference materials. The second part of the report, of particular relevance of manufacturers and national control authorities, contains guidelines for the production and control of synthetic peptide vaccines, requirements for tick-borne encephalitis vaccine (inactivated), guidelines for thromboplastins and plasma used to control oral anticoagulant therapy, an amendment to the requirements for hepatitis B vaccine made by recombinant DNA techniques and a report on the standardization and calibration of cytokine immunoassays.

Biological Products↗
PubMed1996

A 10-year follow-up study of tick-borne encephalitis in the Stockholm area and a review of the literature: need for a vaccination strategy.

143 people treated for tick-borne encephalitis (TBE) were included in a retrospective follow-up study. Sequelae and epidemiological characteristics in 114 individuals were analysed. The case fatality rate and the prevalence of residual paresis were low, 1.4 and 2.7%, respectively. However, 40 (35.7%) individuals were found to have a postencephalitic syndrome after a median follow-up time of 47 months, and a majority (77.5%) of these were classified as moderate to severe. Various mental disorders, balance and co-ordination disorders and headache were the most frequently reported symptoms. Increasing age was correlated to a longer duration of hospital stay, longer convalescence and increased risk of permanent sequelae. Results from a neuropsychiatric questionnaire showed marked differences between the subjects with sequelae compared to controls. 57% had noticed a tick bite before admission, and 48% were aware of at least one person in their environment who previously had contracted TBE. 79% were permanent residents or visited endemic areas often and regularly. In conclusion, we have found that TBE in the Stockholm area has a low case fatality rate, but gives rise to a considerable number of different neurological and mental sequelae, which justifies vaccination of a defined risk population in endemic areas.

Adolescent↗
PubMed2001

Efficacy of a single whole-body spray treatment of spinosad, against Boophilus microplus (Acari: Ixodidae) on cattle.

The efficacy of a single whole-body spray of spinosad, a naturally derived control agent, applied at three concentrations was evaluated against cattle infested three separate times prior to treatment and at four weekly intervals following treatment with Boophilus microplus (Canestrini). At 0.0167% active ingredient (AI) both tick numbers (1894 ticks per calf) and index of fecundity (IF) of females (258.3) were no different than that of the control group. However, spinosad treatment at both 0.05 and 0.15% AI resulted in fewer ticks per calf (600 and 935, respectively) with lower IF values for females (43.4 and 38.4, respectively). The percent control of ticks on the animals at the time of treatment (acute efficacy) was dramatically lower at 0.0167% AI (21.4%) than at 0.05 (86.3%) and 0.15% AI (87.9%). Spinosad treatments appeared to be more effective against immature stages (nymphs and larvae) than against adult ticks that were on the animals at the time of treatment. The mean weight of females that survived to repletion was similar (322-348 mg) in all groups. By contrast, the mean weight of egg masses produced by females was highest in the control group (155 mg), whereas each increase in spinosad concentration resulted in a substantial decrease in egg mass weight, with the 0.15% AI group averaging only 73 mg. The hatch rate of eggs derived from females ranged from 93.4% in control females down to 53.9% hatch for females treated at 0.15% AI spinosad. The residual efficacy of spinosad at 0.0167% AI was poor even at 1 week following treatment, resulting in 101 ticks per calf and a level of control of only 66.4%. At 0.05% AI, protection against successful reinfestation was high at 1-week post-treatment where only five ticks per calf reached repletion, and control of the IF of these females was 99.3%. The 0.15% AI treatment provided almost complete protection against reinfestation for 2 weeks following treatment (< or =5 ticks per calf), and control of the IF of these ticks was >99.9%. Thus, the use of spinosad at US ports-of-entry would be unacceptable because of the critical necessity of achieving 100% control with a single treatment to prevent the reintroduction of ticks. However, it is likely ticks could be eradicated using spinosad in tick infested areas of the US if repeated (systematic) treatments were applied to cattle maintained on the premises.

Administration, Topical↗
PubMed1994

Vertical migration of adult Ixodes rubicundus, the Karoo paralysis tick (Acari: Ixodidae).

Mortality due to Karoo paralysis amongst livestock is of considerable economic importance in South Africa. Indications are that the extent of vertical migration of adult ticks, to reach questing positions on grasses, is influenced by sudden climatic changes. Such influences as well as selection of questing substrates were investigated under controlled conditions. Vertical migration of adult Ixodes rubicundus on copper rods was determined in a square metal arena within a closed glass container in a room in which temperature and light could be controlled. Significantly more female and male ticks migrated vertically on 1.5 mm diameter rods than on 4.0 mm rods and on 450 mm long rods than on 100 mm rods. More ticks of both sexes migrated vertically at RH > 80% than at RH < 50% and at 12 degrees C than at 21 degrees C. More female than male and more older than younger ticks migrated vertically in all experiments. The results of this study contribute towards an understanding of the epidemiology of Karoo paralysis.

Animals↗
PubMedDate not supplied

Borrelia lonestari DNA in adult Amblyomma americanum ticks, Alabama.

Polymerase chain reaction analysis of 204 Amblyomma americanum and 28 A. maculatum ticks collected in August 1999 near the homes of patients with southern tick-associated rash illness and in control areas in Choctaw County, Alabama, showed Borrelia lonestari flagellin gene sequence from two adult A. americanum. The presence of B. lonestari in A. americanum ticks from Alabama suggests that this suspected pathogen may be widespread in the southeastern United States.

Alabama↗
PubMed1999

Lyme disease.

Lyme disease (LD) is the most common tick-borne disease in the United States. The overall trend has been an average annual increase in reported cases since surveillance was initiated by the Centers for Disease Control and Prevention in 1982. Ixodes ticks often carry more than one potential pathogen, and co-infection with Borrelia burgdorferi and other organisms has been reported. The impact of dual infection upon the clinical course of LD is not known. Further studies of erythema migrans-like rashes in the Southern United States have indicated that it is likely caused by a related spirochetal organism. Case reports of unusual presentations have broadened our understanding of the clinical spectrum of LD. Studies in patients with chronic Lyme arthritis have indicated that an autoimmune process may be responsible for such cases. Results of two large, placebo-controlled trials of a recombinant Lyme vaccine have been reported and results indicate that the vaccine is safe and effective in preventing LD in adults.

Adult↗
PubMed1989

Development of resistance in calves to nymphs of Rhipicephalus appendiculatus (Acarina:Ixodidae) during test feeds.

A test of host resistance to infestation by the tick Rhipicephalus appendiculatus was repeated 5 times, at weekly intervals, on 2 initially susceptible calves. One hundred nymphs (NN) were used each time. Pairs of tick-susceptible rabbits served as controls. The engorged NN were weighed, then allowed to moult individually, and the sex of each was noted after emergence of the adult. During the course of the experiment there was a significant reduction in mean engorged weight (especially in the pre-male NN) and also in the length of the feeding period, and a downward trend in the percentage of NN which engorged. There was a significant increase in the percentage of engorged NN that moulted. Pre-male NN were significantly heavier than pre-female NN after feeding on susceptible hosts, but though mean feeding times were the same, they took 1-2 days longer to moult than pre-females at 28 degrees C. It was concluded that the test itself could induce resistance if applied to fully susceptible calves.

Analysis of Variance↗
PubMed2001

Mortality caused by experimental infection with the yeast Candida haemulonii in the adults of Ornithodoros moubata (Acarina: Argasidae).

A relatively high rate of mortality among engorged females of Ornithodoros moubata (Murray, 1877) was observed in our laboratory colony. The general aim of the study was to identify the causative agent responsible for this mortality. The diagnostic tests were performed by Yeast Identification Service (CBS-Delft, Netherlands) and the pathogen was identified as the yeast Candida haemulonii (van Uden et Kolipinski, 1962) Meyer et Yarrovi, 1978. The artificial infection study was performed by intrahaemocoelic inoculation of yeast suspension, resulting in a mortality of 37%. The maximum mortality of ticks infected per os by contaminated blood meal was 13%. Re-isolated yeast cells from haemolymph of dead and paralysed ticks were apparently identical with primary yeast cells, without loosing reproductive abilities. An occasional formation of elongated chains of yeast cells (pseudomycelium) was recorded. The majority of ticks infected in both experiments mentioned above survived and displayed no evident symptoms of the infection. The presence of yeast cells in the haemolymph of surviving ticks was not detected. The in vitro phagocytosis assay performed with FITC-labelled yeast cells showed that about 4% of tick haemocytes were phagocytically active against the pathogenic yeast cells. Thus phagocytosis seems to be a potent defence reaction against spreading and multiplying of the yeast C. haemulonii within the tick haemocoel.

Animals↗
PubMed2006

Pharmacological characterization of the ergot alkaloid receptor in the salivary gland of the ixodid tick Amblyomma hebraeum.

Female ticks of the family Ixodidae osmoregulate by secreting the excess fluid of the blood meal back into the host's circulation via the salivary glands. At least three receptors control salivary fluid secretion in the tick Amblyomma hebraeum: (1) dopamine (DA) stimulates fluid secretion via a DA receptor, (2) ergot alkaloids (ErAs) stimulate fluid secretion via an ErA-sensitive receptor (the natural ligand of which has not been identified), and (3) a GABA receptor potentiates the action of DA and ErAs. Here we present some pharmacological properties of the ErA-sensitive receptor. Of the 11 ErAs we tested, (i) four were complete agonists (approximate concentration eliciting 50% maximum response is given in parentheses): dihydroergotamine (0.02 micromol l(-1)), ergonovine (ErN; 0.06 micromol l(-1)), methylergonovine (0.1 micromol l(-1)) and alpha-ergocriptine (0.9 micromol l(-1)); (ii) three were ;incomplete agonists' (approximate concentration eliciting 20% maximum response is given in parentheses): ergocorninine (3.5 micromol l(-1)), ergocristinine (7.5 micromol l(-1)) and ergocristine (10 micromol l(-1)); (C) three were partial agonists (approximate concentration eliciting the respective maximum response in parentheses): ergocornine (50% maximum by 1 micromol l(-1)), methysergide (28% maximum by 10 micromol l(-1)) and bromocriptine (22% maximum by 10 micromol l(-1)); and (D) one had no activity up to 1 mmol l(-1): ergothioneine. Bromocriptine and methysergide did not antagonize the action of DA, but were effective competitive antagonists of ErN, with K(i)s of approximately 0.3 micromol l(-1) and 11 micromol l(-1), respectively. Ergothioneine was not an antagonist at either the DA- or ErA-sensitive receptor. The putative protein kinase C activators, 1-oleoyl-2-acetyl-sn-glycerol (OAG) and 1,2-dioctanoyl-sn-glycerol (DiC8), neither stimulated salivary fluid secretion nor potentiated the action of DA or ErN. The putative protein kinase C inhibitors, bisindolymaleimide (BIM) and calphostin C did not inhibit the action of DA or ErN, although low concentrations of calphostin C (10 nmol l(-1)) appeared to potentiate the action of DA but not ErN. The ion transport inhibitors, furosemide and amiloride (both up to 1 mmol l(-1)), had no significant effect on DA-stimulated or ErN-stimulated fluid secretion.

Animals↗
PubMed2000

Effects of permethrin on the salivary glands and neuroendocrine organs of unfed female Hyalomma (Hyalomma) dromedarii (Ixodoidea: Ixodidae).

Permethrin-impregnated fabric has been shown to be an effective repellent against various tick species. However, some tick species are not repelled by this chemical. In Hyalomma dromedarii (Koch), permethrin exposure is reported to actually enhance the tick's attachment behavior. This study evaluated the histological effects of permethrin exposure on the salivary glands and neuroendocrine organs of unfed, virgin H. dromedarii ticks of uniform age. Three fabric treatments consisting of unwashed-untreated (control), washed after treatment (0.125 mg [AI] / cm2) and unwashed-treated were used after 5- and 10-min exposure times for unfed, unmated females. For all of the organs examined, the cellular structure of treated ticks differed from controls as evidenced by increases in cellular activity, as well as significant increases in the size of the cells of the organs under study (P < 0.05). These data conclusively demonstrate that an unexpected enhanced attachment response observed in this tick species after permethrin exposure is the direct result of increased neurosecretory and salivary gland activity induced by that exposure.

Animal Feed↗
PubMed2004

Reinfection with Anaplasma phagocytophilum in BALB/c mice and cross-protection between two sympatric isolates.

Infection with Anaplasma phagocytophilum in white-footed mice results in partial protection against reinfection with the same agent. However, humans and domestic animals may be sequentially exposed to different isolates of the agent circulating in the same or adjacent foci. We investigated whether immune response to a tick-borne infection with A. phagocytophilum provides protection against homologous and heterologous challenges. BALB/c mice were infected with one of the two sympatric isolates of A. phagocytophilum via tick bite and challenged 16 weeks later by Ixodes scapularis nymphs infected with either the same or the alternative isolate. As controls, groups of infected mice were challenged by uninfected ticks to confirm an absence of reactivation of the original infection or groups of naive mice were fed upon by ticks from cohorts used for an infectious challenge. Xenodiagnostic I. scapularis larvae were fed upon each mouse at 14 and 21 days postchallenge (PCH) and tested for the presence of A. phagocytophilum as freshly molted nymphs. Blood samples for quantitative PCR were collected at 7, 14, 21, and 70 days PCH. Serum samples were collected weekly to monitor development of immune response. The proportion of infected animals, levels of bacteremia, and the prevalence of infection in xenodiagnostic ticks were higher in groups of control mice exposed to A. phagocytophilum for the first time than in mice reinfected with either homologous or heterologous isolates. The presence of antibodies against A. phagocytophilum did not protect mice from a challenge with either homologous or heterologous isolates, however the ensuing reinfection was significantly milder and of a shorter duration than the first infection with either isolate.

Anaplasma phagocytophilum↗
PubMed1983

Protection of cattle against Theileria annulata infection using Corynebacterium parvum.

Four groups of calves (A, B, C and D) each consisting of five calves were used for the present study. Group A calves were given Corynebacterium parvum alone. Group B calves were inoculated with inactivated ground-up-tick supernate (GUTS) prepared from Hyalomma anatolicum anatolicum infected with Theileria annulata plus C. parvum. Group C received only inactivated GUTS. All the surviving calves of groups A to C were exposed on day 45 post-inoculation to a lethal tick challenge along with susceptible control calves of group D. All the calves of groups A and B withstood the challenge whereas all the calves of groups C and D died of theileriosis. Complement fixing antibodies were detected in calves of groups B and C. A significant decrease in neutrophils and a significant increase in monocytes was observed in calves of groups A and B. No significant changes were seen in other cell types. The results of this study demonstrated that C. parvum alone may be used as an immunostimulant for producing non-specific resistance against T. annulata.

Animals↗
PubMed2000

Zoonotic infections in Nigeria: overview from a medical perspective.

Infections of domestic and wild animals that are transmitted directly or by an arthropod vector to humans are a major cause of morbidity and mortality worldwide and particularly in Nigeria. With a population of over 100 million and the need for improved health care delivery, Nigerians are at considerable risk considering the seriousness of these infections. Zoonotic infections that are endemic in Nigeria include tuberculosis, trypanosomiasis, toxoplasmosis, taeniasis, rabies, lassa fever and yellow fever. Zoonotic food-borne infections (caused by Campylobacter, Salmonella and Escherichia coli O157:H7) and cryptosporidiosis are emerging. Sporadic cases such as strongyloidiasis, ascariasis, leptospirosis, scabies, pentastomiasis and African histoplasmosis have been reported. There is a need to determine the prevalence of tick-borne zoonoses. Prevention and control of zoonoses in humans is by vaccination, treatment and health education. As a first measure to improve control, the link between veterinary and medical officers, which is presently very weak, needs to be strengthened. Furthermore, regional multidisciplinary approaches to the control of zoonotic infections should be adopted in West Africa, which take into consideration the huge inter-border traffic.

Animals↗
PubMed2002

Heterogeneity in the effect of different ixodid tick species on human natural killer cell activity.

Tick saliva plays a vital role in blood-feeding, including manipulation of the host response to tick infestation. Furthermore, a diverse number of tick-borne pathogens are transmitted to vertebrate hosts via tick saliva, some of which exploit the immunomodulatory activities of their vector's saliva. We report that salivary gland extracts (SGE) derived from Dermacentor reticulatus adult ticks induce a decrease in the natural killer (NK) activity of effector cells obtained from healthy human blood donors. The decrease was observed with SGE from both female and male D. reticulatus fed for either 3 or 5 days on mice, but no significant effect was observed with SGE from unfed ticks or ticks that had fed for 1 day. These results indicate that the tick anti-NK factor(s) is only active after blood-feeding has commenced. Microscopic examination revealed that the first step of NK activity, namely effector/target cell conjugate formation, was affected by SGE. The observed reduction in conjugate formation occurred when effector (but not target) cells were treated with SGE for 30 min, and the effect persisted after 12 h of treatment. Similar but less potent anti-NK activity was detected for SGE from Amblyomma variegatum and Haemaphysalis inermis. By contrast, SGE derived from Ixodes ricinus and Rhipicephalus appendiculatus female ticks did not decrease NK activity. The apparent absence of such activity in these two important vectors of tick-borne viruses suggests that control of NK cells does not play an important role in promoting virus transmission, at least for these particular species.

Animals↗