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Biomedical subjects

A R Walker

Publications and source records attributed to A R Walker.

At least 163 records · Page 9Linked to original sources
PubMed1994

Seasonal prevalence of ticks and their association with dermatophilosis in cattle on the Accra plains of Ghana.

The seasonal abundance of adult ticks on cattle and their association with dermatophilosis were investigated in five herds on the coastal plains of Ghana over a 26-month period. Four genera, Amblyomma, Boophilus, Rhipicephalus and Hyalomma were identified, A. variegatum being the predominant species occurring throughout the year with two peaks of infestation, one in April-May and the other in November. A significant positive correlation was revealed between A. variegatum and dermatophilosis in four of the five herds. Significant positive correlations were found between H. m. rufipes and dermatophilosis in two of the herds and between Rh. senegalensis and dermatophilosis in one herd. Negative correlations of statistical significance were observed between Boophilus species and dermatophilosis in three of the herds. Nevertheless, it was considered that A. variegatum was the most important tick factor involved in the pathogenesis of the disease.

Animals↗
PubMed1994

Blood cholesterol and coronary heart disease: changing perspectives.

There has been much controversy concerning the value of efforts to reduce blood cholesterol levels. In this contribution, the risks and benefits of interventions are discussed. Lowering cholesterol level by drugs is not recommended except in a small minority of subjects at very high risk of coronary heart disease (CHD), since it causes an excess of non-CHD deaths. Dietary intervention, by contrast, is safe. However, for it to be effective it must be sufficiently vigorous to achieve a drop in blood cholesterol of at least 6%, though considerably more is preferable. This action should be part of a more general effort aimed at the prevention of all Western diseases based on changes in lifestyle.

Cause of Death↗
PubMed1993

The local effect of hypersensitive or inflammatory reactions to nymphal Amblyomma variegatum on simultaneous infections with Dermatophilus congolensis.

Amblyomma variegatum nymphs were applied to sites infected with Dermatophilus congolensis on eight rabbits. Four rabbits were previously sensitized to the feeding of nymphal A. variegatum to produce hypersensitive reactions to the tick feeding; the remaining four rabbits had no previous exposure to nymphal A. variegatum and produced inflammatory reactions to the tick feeding. The resulting dermatophilosis infections were assessed for three weeks and there was a correlation between the position of the inflammatory tick attachment sites and the foci of infection. There was a significant increase in the lesions at sites with inflammatory reactions to the ticks, compared with sites not exposed to tick feeding; these differences appeared to be due to individual variation in the host response and were not sustained throughout the assessment.

Actinomycetales Infections↗
PubMed1993

The effect of inflammatory and hypersensitive reactions, in response to the feeding of the tick Amblyomma variegatum, on the progression of experimental dermatophilosis infections.

Initial infestations of Amblyomma variegatum larvae and nymphs, on rabbits and sheep respectively, produced inflammatory reactions in the host's skin; repeated infestations resulted in an increase in development of delayed type hypersensitive reactions. Dermatophilus congolensis cocci were applied in titrated doses to hosts at sites of inflammatory or hypersensitive reactions to ticks, and to control hosts with no exposure to ticks. We assessed the resulting infections for three weeks and found no significant difference between the infections on the three groups. We conclude that the local effects of the feeding of immature stages of this tick do not influence the pathogenesis of dermatophilosis.

Actinomycetales Infections↗
PubMed1993

Screening and the costs of treating colorectal cancer.

The objective of this paper is to compare the hospital costs of treating patients with colorectal cancers detected as a result of a faecal occult blood screening programme with those of patients whose cancers present symptomatically (control group). Patient-specific cost estimates are made, using case records and hospital accounts, for 360 patients over 3 years. Mean treatment costs for the group offered screening and for the control group are calculated to be 3,179 pounds and 2,966 pounds respectively, although the difference between these means is insignificant. Low treatment costs in the case of screen-detected cancers are largely accounted for by polypectomy with no subsequent readmission; in the control group case, they tend to be accounted for by early patient death. For the sample as a whole, the costs of treating very early-, and very late-, stage cancer are significantly lower than those of treating cancers in the intermediate stages. On the basis of trial evidence, the introduction of mass screening for colorectal cancer is unlikely to give rise to substantial economies in the costs of treatment.

Colorectal Neoplasms↗
PubMed1993

Experiments on the relationship between feeding of the tick Amblyomma variegatum (Acari: Ixodidae) and dermatophilosis skin disease in sheep.

Experiments on the systemic effect of feeding adult Amblyomma variegatum (F.) on dermatophilosis caused by Dermatophilus congolenis in six sheep were performed by feeding ticks at sites separate from sites of experimental infection with D. congolensis. Comparisons were made with D. congolensis infections on six control sheep without ticks. Tick-infested sheep developed chronic dermatophilosis lesions; tick-free sheep healed rapidly. On two tick-infested and two control sheep a chronological sequence of D. congolensis infection sites were made for histological comparisons. Dermatophilosis lesions on tick-infested sheep were characterized by chronic cellular infiltration and accumulation of plasma cells. Lesions on control sheep healed in association with transient cellular infiltration including plasma cells. In neither test nor control sheep was there evidence of effective phagocytosis of D. congolensis. It was concluded that feeding of these ticks had a systemic effect on the host such that dermatophilosis was aggravated via an effect on immunological reactions in the skin. Control of dermatophilosis by tick control is advocated.

Actinomycetales Infections↗
PubMed1993

Cancer patterns in three African populations compared with the United States black population.

Cancer incidence rates and patterns in three African populations in the Gambia, Mali and South Africa, have been compared with corresponding data on the Black population in Connecticut, USA. In the African populations, total rates for cancer are much lower than that of US Blacks, even allowing for under-reporting. Chief cancers are those of the oesophagus, liver and cervix. In Mali, stomach cancer is very common. As to trends, among South African Blacks, a population in transition, rates are rising, albeit slowly, of cancers of prosperity--prostate, lung, breast and colon-rectum. Salient questions are: can the number of cancers of underprivilege be lessened, and can cancers linked with rising socioeconomic states be restrained? Discussions of common risk factors, including diet, reproduction, smoking and drinking practices, indicate that for Africans as a whole, continuing poverty will prevent major changes in cancer pattern and rises in occurrence of the disease. However, should prosperity increase for Africans in big cities, rates are ultimately likely to attain those prevailing in the US Black population. Significant avoiding action seems almost impossible.

Black or African American↗
PubMed1993

Nutritional and non-nutritional factors for 'healthy' longevity.

The far-reaching effects of the ageing of populations is being increasingly appreciated. Lengthening longevity, associated with decreasing family size, evokes rising charges, socioeconomically, and on health services. Information on these and other parameters is presented for developed and developing populations. Examples are given, with lessons to be learned, of long-living segments of populations, past and present. The roles of diet, physical activity, and smoking and alcohol consumption also of attitudes, are discussed. It is concluded that if the middle-aged and elderly could be persuaded to follow long-term practices associated with good public health, then morbidity could be compressed, and disability-free years extended. However, this goal could only be achieved with a high level of motivation.

Family Characteristics↗
PubMed1993

The systemic effect of adult and immature Amblyomma variegatum ticks on the pathogenesis of dermatophilosis.

The systemic effect of adult and nymphal Amblyomma variegatum on the pathogenesis of experimental infections of Dermatophilus congolensis was investigated. Three groups of four sheep were used with all 12 sheep being infected with identical titrated doses of D. congolensis One group of sheep was simultaneously infested with adult A. variegatum the second with nymphal A. variegatum and the third group were the controls, with no exposure to ticks. Assessment of the resulting infections indicate that the systemic effect of this tick is confined to the adults. Skin and serological tests using foreign antigens showed significantly reduced cell mediated and humoral immune response only in the sheep infested with adult A. variegatum.

Actinomycetales Infections↗
PubMed1993

The effect of tick control on the prevalence of dermatophilosis on indigenous cattle in Ghana.

The effectiveness of three tick control regimes on the occurrence of Amblyomma variegatum and dermatophilosis on cattle on the coastal plains of Ghana were compared. Animals at one kraal were sprayed with amitraz at predilection feeding sites of ticks every second week using a high concentration minimum volume technique. Animals at two other kraals were treated with a deltamethrin based pour-on acaricide; at one kraal it was applied once every month while at the other kraal it was used at strategic times based on the expected seasonal increases in the level of infestation with A. variegatum. Animals in a fourth kraal (control group) were treated, by the herdsmen, to control excessive tick build-up as practised under traditional management systems. Fortnightly treatment with amitraz reduced the level of infestation with A. variegatum and the prevalence of dermatophilosis dropped to a low level. The pour-on acaricide similarly depressed the prevalence of dermatophilosis.

Actinomycetales Infections↗