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D H Kemp

Publications and source records attributed to D H Kemp.

54 records · Page 3Linked to original sources
PubMed1983

In vitro feeding of Dermacentor andersoni (Stiles): effects of histamine and other mediators.

Female Dermacentor andersoni were induced to feed on defibrinated bovine blood through fixed mouse skin membranes. Their feeding behaviour was recorded electronically, the tick being incorporated into the circuit and acting as a variable resistor during the periods of sucking, salivation and rest. Recordings of the feeding behaviour of these ticks were similar to those of ticks feeding on rabbits. Known concentrations of histamine, serotonin, dopamine, prostaglandin E1 and prostaglandin F2a were added singly or in combination to the feeding medium of ticks attached to the mouse skin membrane. Addition of both histamine and serotonin was followed by a significant reduction in the amplitude or recordings associated with sucking and salivation. The concentration of mediators producing this effect was less than 10 mM, a concentration comparable to that of histamine found locally in the skin of tick-resistant guinea-pigs. Comparisons are made between the effects produced by these mediators in ticks and the effects of serotonin and other amines known to produce modulation of complex behaviour patterns in other invertebrates.

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PubMed1982

Observations on the behaviour of Dermacentor andersoni larvae infesting normal and tick resistant guinea-pigs.

In three separate experiments the behaviour of Dermacentor andersoni larvae on normal and tick-resistant guinea-pigs was studied at intervals throughout 5-day infestation periods. Fewer larvae survived on resistant hosts and their mean sizes were less than those of larvae on normal hosts, the differences becoming more obvious as time progressed. When measured at 32 degrees C, the peristaltic rates of midgut diverticula of the larvae surviving on resistant hosts were consistently lower than those of larvae from normal hosts. Mean surface temperatures of infested ears were higher on resistant than on normal hosts. This was assumed to be a result of cutaneous hypersensitivity reactions in the resistant animals. Larvae detached, or changed attachment sites, more often on resistant than on normal hosts. This was consistently evident after 26 h post-infestation and correlated with the known timing of basophil cell infiltration and degranulation in the skin of infested, resistant guinea pigs. It appeared that most larvae, after detaching from the resistant host, died off the host. However, some died in situ while still attached. Such deaths occurred on resistant but not on normal animals between 8 and 26 h post-infestation.

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PubMed1981

A putative role for eosinophils in tick rejection.

In the reaction of Bos taurus cattle to infestation by the tick Boophilus microplus, mast cell histamine is translocated by the eosinophils to the attachment site. The concentration pattern of this cutaneous mediator for pain appears related to the grooming behaviour of the host.

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PubMed1981

Cutaneous hyperaemia elicited by larvae of the cattle tick, Boophilus microplus.

The responses of skin capillary blood flow (BF) to infestation by larvae of B. microplus have been determined using radioactive microspheres. Larvae were placed in gauze-covered rings glued to the closely clipped skin. In pilot experiments on three Brahman-cross calves which had prior exposure to ticks, BF measurements at intervals up to 25 h post-infestation revealed a continuing increase. 'High' rates of infestation (5000 larvae per ring) elicited up to an 80-fold increase in BF. In four Australian Illawarra Shorthorn (AIS) calves with prior exposure to ticks, BF had increased by 0.5 h post-infestation, it reached a peak at 24 h, and fell markedly by 48 and 75 h. In contrast, two AIS calves without prior tick exposure showed no significant increase in BF until 24 h and this increase continued until observations were terminated at 72 h. BF in the neck area (normally favoured by ticks) increased most in calves of highest resistance to ticks, but the flank area (normally unfavoured) showed no consistent difference in BF response between animals of different tick resistance. It is concluded that skin capillary hyperaemia is triggered by the host's immune response to larval attachment. Within the relatively narrow range of tick resistance in the present animals, the degree of hyperaemia was directly related to level of resistance to the tick in skin regions normally favoured by ticks and therefore it may play a role in determining resistance to ticks.

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PubMed1980

Boophilus microplus: the effect of histamine on the attachment of cattle-tick larvae--studies in vivo and in vitro.

Circumstantial evidence suggests that the earlier detachment of Boophilus microplus larvae from highly resistant cattle follows the release of histamine at the attachment site. In vivo and in vitro experiments show that a proportion of the larvae will detach following injection or infusion of histamine. Other mediators such as bradykinin, prostaglandin E2, 5-hydroxytryptamine and dopamine have little or no effect on tick behaviour in vivo. Sensitivity to histamine declines as larval attachments stabilize, and repeated injections have no effect on the weight of larvae after 3 days on the host. Response to histamine is discussed in relation to host resistance, histology of the feeding lesion and larval behaviour.

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PubMed1978

Boophilus microplus: rejection of larvae from British breed cattle.

Larvae of Boophilus microplus were labelled with [32P] and used to study the rejection of larvae from British breed cattle with different levels of resistance. On animals of high resistance the loss of larvae due to grooming ranged from 9-54% during the first 24 h of infestation, and more time was spent grooming by these animals. Most of the grooming activity could be attributed to the presence of tick larvae and the presence of older tick stages did not increase the percentage of larvae lost. Grooming was directed to attached larvae and these could be removed. Animals of low resistance did not lose a significant number of larvae as a result of grooming, but all previously infested hosts lost a proportion of the larvae (18-39%) which could not be accounted for by grooming. This loss was greater than the total loss of larvae (11%) on animals not previously exposed to B. microplus.

Animals↗
PubMed1977

Paralysis of calves by the tick, Ixodes Holocyclus.

Adult female Ixodes holocyclus were collected from the field at Fig Tree Pocket, a Brisbane suburb, at Tamborine Mountain, Queensland and at Lismore, New South Wales, in November 1974. Females were also reared from engorged nymphs collected off bandicoots from Tamborine Mountain July 1974 and 1975. In November 1974 unexposed 2-3 week old British breed calves, weighing between 26 and 46 kg were infested with 2,4,8 or 10 ticks. Neither 2 nor 4 females per calf caused paralysis. A challenge of 8 to 10 females induced paralysis 6 to 9 days after infestation by which time most ticks had engorged. There was little difference between ticks from different geographic localities. The site of attachment had no influence on tick toxicity. In September 1975, 2-3 week old British breed and Sahiwal x Jersey calves were infested with female ticks which had moulted 2-4 weeks prior to infestation. All but one calf with 10 ticks and all calves with 4 ticks became paralysed 8 to 13 days after infestation. At the time of paralysis only 1 of the 86 ticks had engorged and the remainder were small (30 to 50 mg). The greater toxicity of the latter ticks may have been due to the different treatment of ticks prior to infestation or to variations in the production of toxin associated with slow feeding. Four of 7 paralysed calves were saved using canine antitick serum.

Animals↗
PubMed1977

Histology of bovine skin reactions to Ixodes holocyclus Neumann.

The histology of skin responses to infestations with female Ixodes holocyclus ticks was investigated in naive and previously infested cattle. In the latter hosts, infiltration of the skin site with basophil leucocytes was an early event. Concurrent spongiosis and vesiculation occurred in the epidermis adjacent to the tick mouthparts. This was followed by infiltration of the upper dermis by eosinophils and other leukocytes. Such reactions were evident one hour after attachment of ticks in hosts which had received two prior infestations. Pronounced epidermal vesiculation and bulla formation with eventual serous exudation followed in previously infested cattle, leading to entrapment of ticks.

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PubMed1976

Boophilus microplus: the effect of host resistance on larval attachments and growth.

Growth and behaviour of Boophilus microplus larvae on British breed cattle, with different resistance levels to the tick, were studied to elucidate the nature of resistance. On highly resistant animals, larval growth rate was slower for the first 3 days, but by day 4 they had attained the normal weight and the majority were subsequently able to moult. Using phosphorus-32 labelled larvae, it was found that attachment times were shorter and more time was spent wandering on highly resistant animals during the first 16 h. On the second day, attachments had stabilized, but more detachments were still made from highly resistant animals. This was considered to impose an additional stress as the cattle skin environment can rapidly desiccate larvae. However, the larvae were able to compensate by uptake of fluid from the host. Loss by repulsion of live larvae from the host or drowning in serous exudate were also not considered of major importance. The nature of rejection is discussed in a further paper. The distribution of larvae after 24 h suggests that their early behaviour largely determines the areas favoured by adults. Movement to, and accumulation in, favoured areas is discussed.

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PubMed1976

Boophilus microplus: cellular responses to larval attachment and their relationship to host resistance.

The histology of early feeding lesions of the cattle tick B. microplus has been studied using 32P labelled larvae to standardize the duration of attachment. Critical studies were made on 3-h lesions in six separate experiments on different groups of British breed animals. Each group consisted of three animals--one previously unexposed to ticks, one of high resistance and one of low resistance. The degree of mast cell disruption, eosinophil concentration and degranulation, and the extent of epidermal vesiculation were all significantly greater at the site of attachment on highly resistant hosts. In previously unexposed animals there was no mobilization of eosinophils nor mast cell breakdown and no epidermal vesiculation. Possible immune mechanisms producing mast cell disruption and the infiltration and concentration of eosinophils are suggested, and the effect of eosinophil degranulation on larval attachment and feeding is discussed.

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PubMed1975

Feeding of Boophilus microplus larvae on a partially defined medium through thin slices of cattle skin.

Larvae of the cattle tick Boophilus microplus will attach to thin (0-3--0-5 mm) slices of cattle skin and engorge on a partially defined medium at 35 degrees C. Forty-seven to 83 per cent of the larvae had engorged by 8 days, and 51--71 per cent of these moulted to nymphs. Tissue culture medium alone allowed little growth unless supplemented with dialysed, freeze dried bovine serum (7 per cent, w/v). This medium could be further difined by substituting purified bovine serum albumin (Cohn fraction V) for the dialysed bovine serum. In one experiment, nymphs of Haemaphysalis longicornis engorged and later moulted to adults. Skin slices were used fresh or after freeze-drying and storing at --25 degrees C. The possible uses of the culture method are discussed.

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PubMedDate not supplied

Development of tick gut forms of Babesia bigemina in vitro.

Development of a laboratory cultured tick-transmissible strain of Babesia bigemina was followed in vitro after addition of gut material from engorged female Boophilus microplus ticks and incubation at 37 degrees C. Sequential development of stages, from intraerythrocytic strahlenkörper through multiplication to the fusion of what is assumed to be two gametes, is described. A change in physical environment (temperature, gas composition) experienced during passage of Babesia stages into the in vitro culture tubes possibly mimics the changes experienced in passage from host blood to the midgut of the tick vector. The effect in vitro was to induce the erythrocytic parasites to remain inactive at a trophozoite-like stage. Addition of factor(s) within midgut initiated further development of strahlenkörper. Two populations of strahlenkörper were recognized; an elongated form which did not appear to develop further, and a polymorphic population which underwent further multiplication initiated while the parasites were still within the erythrocyte, and continuing after they had emerged. These strahlenkörper increased in size as multiple division of nuclei occurred. with cell division being completed more slowly. Large aggregations of multinucleated strahlenkorper formed, but once division was complete, single-nucleated strahlenkörper emerged from the aggregates. Two individuals of post-aggregation strahlenkörper, assumed to be gametes, fused together. The morphology and ultrastructure of all stages of development are described and compared with forms already described from the tick midgut.

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