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Biomedical subjects

A M Downs

Publications and source records attributed to A M Downs.

At least 19 recordsLinked to original sources
PubMed2000

Back-calculation by birth cohort, incorporating age- specific disease progression, pre-AIDS mortality and change in European AIDS case definition. European Union Concerted Action on Multinational AIDS Scenarios.

OBJECTIVES: To adapt and improve methodology for back-calculation of AIDS in Europe and to examine the feasibility of estimating past HIV incidence by birth cohort. METHODS: Empirical Bayesian back-calculation (EBBC) used Markov disease progression models, modified to allow for three diseases added to the AIDS case definition in 1993 and for pre-AIDS mortality, and estimation by penalized maximum likelihood with a neighbour prior. EBBC by 5-year birth cohort assumed a minimum age at infection and age-dependent progression rates; three versions, with varying age effects, were investigated using AIDS cases diagnosed prior to the introduction of highly active antiretroviral therapies (HAART). RESULTS: Compared with the no age-effect version, EBBC by birth cohort tended to produce flattened HIV incidence curves in country-exposure groups with < 1000 AIDS cases, reflecting effects of the neighbour prior when data become sparse. Otherwise, birth cohort analysis, with moderate effects of age on progression, gave initially increasing incidence curves and consistent patterns across countries, with the 1960-1964 cohort most affected. In the European Union, incidence is estimated to have peaked in 1983 among homosexual men and in 1988 among injecting drug users; 460000 persons were estimated to be living with HIV/AIDS at the end of 1995. CONCLUSIONS: Our improved methodology deals effectively with the change in AIDS case definition and has allowed quantitative assessments of the HIV epidemic by birth cohort using all AIDS cases diagnosed before 1996, thus providing a sound basis for public health policy at a time when estimation of more recent prevalence is compromised by the effects of HAART.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Susceptibility of British head lice, Pediculus capitis, to imidacloprid and fipronil.

The head louse, Pediculus capitis De Geer (Phthiraptera: Pediculidae) has developed resistance to organochlorines, the organophosphate malathion and to pyrethroids in the U.K. Therefore, headlice from Bristol school children were bioassayed against two new insecticides, fipronil and imidacloprid. Pediculus capitis was fully susceptible to imidacloprid, but it required a relatively high dose and acted slowly. Fipronil acted faster at lower dose, but seemed to be affected by cross-resistance in a small proportion of P. capitis.

Animals↗
PubMed1999

The epidemiology of head lice and scabies in the UK.

Anecdotal evidence suggests that the prevalence of both scabies and head lice is increasing and also that both conditions are becoming refractory to pesticide treatment. Using information obtained from the Office of National Statistics, Royal College of General Practitioners Weekly Returns Service, Department of Health, local surveys of school children from Bristol and drug sales of insecticides, we have confirmed that there has been a rise in the prevalence of both conditions. We have shown that scabies is significantly more prevalent in urbanized areas (P < 0.00001), north of the country (P < 0.000001), in children and women (P < 0.000001) and commoner in the winter compared to the summer. Scabies was also shown to have a cyclical rise in incidence roughly every 20 years. Head lice were shown to be significantly more prevalent in children and mothers (P < 0.000001) though both conditions were seen in all age groups. Head lice were also less common during the summer. Host behaviour patterns, asymptomatic carriage, drug resistance and tourism from countries or districts with a higher incidence may be important factors in the currently high prevalence of both scabies and head lice.

Adolescent↗
PubMed1999

Evidence for double resistance to permethrin and malathion in head lice.

A rising prevalence of head lice among school children and rising sales of insecticides with anecdotal evidence of their treatment failure, led us to examine whether head lice in Bristol and Bath were resistant to the insecticides available for treating head lice. Ten schools in Bristol and Bath were visited to collect field samples of head lice. A comparison was made of the survival rates of fully sensitive laboratory reared body lice and field samples of head lice on insecticide exposure. To confirm the in vitro relevance of these tests we performed supervised treatments of affected subjects with malathion or permethrin. There were significant differences (P < 10-6 Fishers exact test) between head and body lice survival for malathion and permethrin exposure, but not for carbaryl. There was an 87% failure rate for permethrin and a 64% failure rate for malathion with the topical treatment of a selected number of infested school children. We conclude that there is a high resistance to permethrin and malathion, but head lice remain fully sensitive to carbaryl. This is the first report of doubly resistant head lice. As permethrin, phenothrin (a very similar synthetic pyrethroid) or malathion are the active ingredients in all the over-the-counter head lice treatments in the U.K., then it is likely that head lice prevalence will continue to increase. The resistance against permethrin employed by the head louse is probably the kdr (knockdown resistance) mechanism, and an enzyme-mediated malathion-specific esterase is the likely mechanism against malathion.

Animals↗
PubMed1999

Polymorphic light eruption limited to areas of vitiligo.

Two patients are described with clinical and histological features of polymorphic light eruption (PLE) limited to areas of vitiliginous skin. This phenomenon has not been reported previously and provides evidence for the protective role of melanin in PLE.

Adult↗
PubMed1999

Isotretinoin therapy for antibiotic-refractory acne in Apert's syndrome.

Apert's syndrome is a congenital disorder characterized by the premature fusion of the cranial sutures and early epiphyseal closure. Severe pustular acne is a common feature. We report a case that failed to respond to conventional antibiotic treatment but resolved following isotretinoin therapy. The patient's permanent tracheostomy proved a management challenge during isotretinoin treatment. The role of androgen-sensitivity is discussed in relation to the skin and bones.

Acne Vulgaris↗
PubMed1999

Colophony allergy: a review.

Colophony is a complex mixture of over 100 compounds derived from pine trees. It has countless applications at home and at work and exposure to colophony and modified-colophony is universal. It is the oxidation products of unmodified and modified colophony and some of the new resin acids synthesized during modification that are the principle allergens in colophony. The neutral fraction may account for a small % of positive reactions. When screening for allergy using unmodified gum rosin, allergy to modified rosin will not be revealed. When patients react to both materials, it is probably due to unmodified colophony present in both, rather than a cross-reaction. Relevant positive reactions may be missed if only colophony 20% pet is relied upon as the screening material.

Allergens↗