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Biomedical subjects

T N Petney

Publications and source records attributed to T N Petney.

At least 19 recordsLinked to original sources
PubMed2004

Argas persicus sensu stricto does occur in Australia.

The status of Argas persicus in Australia has been a matter of controversy for over 25 years. Although early records of A. persicus sensu stricto are common, a major revision of the genus indicated that these records refer to A. robertsi, first described in 1968 from northern Australia, and to an "undescribed" member of the complex occurring in the south. Here, we show that A. persicus sensu stricto does occur in southern Australia and is the only species of Argas in the area recorded from poultry. Another undescribed species belonging to the A. persicus complex, from crows' nests near Lake Eyre in South Australia, was also discovered. This information is of considerable epidemiological significance, as A. persicus sensu stricto is a major vector for a number of highly pathogenic diseases of poultry, not all of which have yet been recorded from Australia.

Animals↗
PubMed2004

Striped mice, Rhabdomys pumilio, and other murid rodents as hosts for immature ixodid ticks as in the Eastern Cape Province.

Striped mice, Rhabdomys pumilio, were trapped over a period of 17 months in the Thomas Baines Nature Reserve, and placed in cages, over water, until all the ticks they harboured had detached. The mice were then returned to the reserve. Four ixodid tick species were recovered from the mice of which the larvae and nymphs of Rhipicephalus follis and Rhipicephalus simus were the most numerous. Most larvae of R. follis detached from mice trapped from March to July, and most nymphs in March and from June to September. Most larvae of R. simus detached from mice trapped from December to March, and most nymphs from January to March and during May and June. Seven ixodid tick species were collected from striped mice, house rats, Rattus rattus, vlei rats, Otomys spp. and Praomys sp. captured in the vicinity of human dwellings or animal holding facilities in the Grahamstown district. The striped mice captured in the Thomas Baines Reserve harboured considerably larger numbers of ticks than any of the rodent species in the more urbanized localities.

Animals↗
PubMed2001

Environmental, cultural and social changes and their influence on parasite infections.

The changes taking place within the societies, cultures and the environments in which we live are massive and complex. By referring to simple epidemiological models it is possible to build an objective framework with which to look at these changes in terms of their likely impact on the epidemiology of parasitic diseases within human communities. These parameters are listed for hosts and both micro- and macroparasites, as are epidemiologically significant cultural, social and environmental variables. Changes in these variables may be either detrimental or beneficial to human health and may, in addition, interact in complex ways. Examples of the complexity of changes which can influence epidemiology are provided for a cultural template of the population living in the north-east of Thailand.

Animals↗
PubMed2000

A simplified method of cleaning ixodid ticks for microscopy.

The cleaning of ixodid ticks for microscopy can be achieved quickly and efficiently using a combination of a wax solvent and an ultrasonic cleaner. The technique involves minimum handling of specimens, produces no detectable damage and is suitable for cleaning many specimens at the same time.

Acetone↗
PubMed1998

Multiparasite communities in animals and humans: frequency, structure and pathogenic significance.

Individual humans and animals are subject to infection by a variety of parasites (broadly defined to include viruses, bacteria and other non-protozoan microparasites) at any one time. Multiple parasite infections occur frequently in populations of wild animals as well as in humans from developing countries. In some species and regions, hosts with multiple infections are more common than hosts with either no infection or a single infection. Studies, predominantly on animals, show that a wide variety of environmental and host-dependent factors can influence the structure and dynamics of the communities of parasites that make up these multiple infections. In addition, synergistic and competitive interactions can occur between parasite species, which can influence the likelihood of their successful transmission to other hosts and increase or decrease their overall pathogenic impact. This review summarises aspects of our current knowledge on the frequency of multiparasite infections, the factors which influence them, and their pathogenic significance.

Animals↗
PubMed1998

Transmission risk of Borrelia burgdorferi sensu lato from Ixodes ricinus ticks to humans in southwest Germany.

The risk of Borrelia burgdorferi infection and the value of antibiotic prophylaxis after tick bite are controversial. In this study, performed in two areas of southwestern Germany, ticks were collected from 730 patients and examined by the polymerase chain reaction (PCR) for B. burgdorferi. To assess whether transmission of B. burgdorferi occurred, the patients were clinically and serologically examined after tick removal and during follow-up examinations. Data from all tick bites gave a total transmission rate of 2.6% (19 patients). Eighty-four ticks (11.3%) were PCR positive. Transmission occurred to 16 (26.7%) of 60 patients who were initially seronegative and could be followed up after the bite of an infected tick. These results indicate that the transmission rate from infected ticks in Europe is higher than previously assumed. Examination of ticks and antibiotic prophylaxis in the case of positivity appears to be indicated.

Adolescent↗
PubMed1997

Ecological implications of control strategies: arthropods of domestic and production animals.

The control of arthropods of veterinary importance represents a disturbance for the ecosystem and its animal community. This disturbance can influence the densities of target and non-target organisms and their associated indirect interactions in the food web, leading to reductions in the species richness and diversities in the communities involved. Finely tuned control affecting the target organism alone can have unexpected consequences, depending on the relationships between the target and other organisms within the food web. Broad-spectrum control methods will have more wide ranging and less predictable consequences. Modifications within the community caused by arthropod control can take place over generations and may not be immediately apparent. Most modern techniques of control are designed to minimize environmental impact by concentrating specifically on the target organism. The effects of control of arthropod pests of domestic and production stock must be seen against a background of more general effects caused by rural development which acts to modify the environment continuously over a long time span.

Animals↗
PubMed1996

Tick infestation patterns and prevalence of Borrelia burgdorferi in ticks collected at a veterinary clinic in Germany.

A total of 4803 domestic and wild animals which were presented for examination at a veterinary clinic in north Baden, Germany over a period of 1 year were examined for tick infestation. A total of 434 nymphal and adult ticks were collected from 175 hosts. Ticks found belonged to the species Ixodes ricinus (385), Ixodes hexagonus (48), and Ixodes ventalloi (one). The polymerase chain reaction was used to examine 132 I. ricinus and 21 I. hexagonus for the presence of Borrelia burgdorferi. Twenty-two per cent of adult I. ricinus were infected as were one female and one larval I. hexagonus.

Animals↗
PubMed1996

Comparison of urinary bladder and ear biopsy samples for determining prevalence of Borrelia burgdorferi in rodents in central Europe.

PCR was used to compare urinary bladder and ear biopsy samples from four European species of wild rodents for the presence of Borrelia burgdorferi sensu lato. From 60 paired comparisons of bladder and ear biopsy samples, the PCR results were concordantly positive or negative in 43 samples (71.7%). Of the 17 which differed, 14 bladder samples were positive and ear samples were negative while the converse occurred for three samples. Thus ear biopsy samples led to a significantly lower estimate of infection than bladder biopsy samples. This suggests that the use of ear biopsy samples in epidemiological studies of B. burgdorferi in Central European rodents is likely to lead to underestimates of the prevalence.

Animals↗
PubMed1995

[Natural epidemiology of Lyme borreliosis with reference to clustered incidence of illnesses in the suburbs of a North Baden community].

Human infection with Borrelia burgdorferi, the causative agent of Lyme disease, is unusually common in the "Scheelkopf" area of the town Bruchsal in north Baden (Germany), a situation which has led to considerable publicity and public concern. This study was carried out in order to clarify this situation by determining the prevalence of B. burgdorferi in both the free-living tick populations (Ixodes ricinus) and the rodent population from the "Scheelkopf" as well as from surrounding control areas. The polymerase chain reaction (PCR) was used to determine the presence of infection in whole tick preparations and in mouse bladders. The prevalence of B. burgdorferi in freeland ticks ranged from 19% to 44% and in mice from 6% to 29% depending on the area studied. The "Scheelkopf", with prevalences for ticks and mice of 33% and 10% respectively, was not significantly different from the control areas. Our results indicate that there is a high risk of human infection throughout the study area. This is probably related to the intensive use of the area for gardens and the related recreational behaviour of the human population in conjunction with the high rate of infection prevailing in I. ricinus.

Animals↗
PubMed1993

Small and medium sized mammals as predators of ticks (Ixodoidea) in South Africa.

A total of 1,640 stomach contents from 56 South African species of small and medium sized mammals were examined for ticks. Only six ticks were found in three specimens of the caracal Felis caracal. Although identification of the tick species was not possible owing to fragmentation and partial digestion, the genus Haemaphysalis was represented in four of these cases. We conclude that predation by small and medium sized mammals on ticks is uncommon in South Africa.

Animals↗
PubMed1991

Resistance of restrained Bos taurus dairy bull calves to the bont tick Amblyomma hebraeum (Acarina: Ixodidae).

Three infestations of restrained Jersey and Friesland bull calves with adult Amblyomma hebraeum did not affect the rate of engorgement of female ticks and resulted in an insignificant decline in the mean engorgement weight of female ticks recovered from the Friesland group. Repeated infestations significantly affected the egg-laying capacity of engorged female ticks recovered from both groups of hosts. The Friesland calves manifested an enhanced resistance to the larvae and nymphs of Amblyomma hebraeum resulting in prolonged attachment, and a significant decline in engorgement rate of these instars compared with the Jersey group. Skin reaction tests using crude tick extracts yielded antigen-specific hypersensitivity reactions which were not related to resistance to A. hebraeum. Histological changes at the attachment site associated with tick rejection are discussed in relation to host resistance mechanisms.

Analysis of Variance↗
PubMed1991

Acquisition of resistance to the bont tick Amblyomma hebraeum (Acarina: Ixodidae) by goats.

Goats acquired resistance to larvae of Amblyomma hebraeum following three repeated infestations. Resistance was associated with immediate Type I hypersensitivity reactions following intradermal skin tests using crude egg extracts. In a separate experiment, the inoculation of tick-naive goats with extracts of the larvae of A. hebraeum failed to induce observable effects on feeding larvae despite the development of anti-larval antibodies.

Analysis of Variance↗
PubMed1990

The dispersion of the Karoo paralysis tick, Ixodes rubicundus, within a naturally infested population of sheep in South Africa.

The ratio of variance to mean (s2/means) of numbers of Ixodes rubicundus (males and females) per sheep was used as a measure of the dispersion pattern of this tick within a naturally infested population of sheep. Sheep were divided into two groups, one with previous contact with I. rubicundus and the other with no previous contact. Samples of 10 sheep from each group were searched for ticks on a weekly basis for 19 weeks during the winter of 1986. In each group, both male and female ticks had an s2/means ratio greater than 1 for the majority of observation periods indicating an aggregated dispersion pattern. The degree of aggregation was greater with increasing density of the ticks. The implications of these results are discussed both in relation to sampling procedures and potential control strategies.

Animals↗
PubMed1990

On sampling tick populations: the problem of overdispersion.

Data collected on both free-living and parasitic tick populations are likely to be overdispersed. The use of means from few replicate samples of overdispersed data as quantitative estimators of tick population density is in turn likely to lead to inaccurate interpretations which may be scientifically misleading. In this paper ways of estimating overdispersion are listed and suggestions for the use of correct statistical tests for handling overdispersed data are given.

Animals↗
PubMed1989

The effect of the pattern of attachment weights of female Ixodes rubicundus on Karoo paralysis in a naturally infested flock of sheep.

The weights of feeding female Ixodes rubicundus attaching to sheep was studied in a natural focus of Karoo paralysis. The studies showed fewer females in the middle weight ranges and more in the heavier and lighter categories than would be expected if the distribution was normal. Weights were also strongly skewed towards the lighter females between 0 and 400 mg. No differences in the pattern of attachment weights occurred over the four experimental groups used, suggesting that previous contact of sheep with I. rubicundus had no effect on the ability of the tick to engorge.

Animals↗