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Biomedical subjects

R M May

Publications and source records attributed to R M May.

At least 109 records · Page 6Linked to original sources
PubMed1982

Population dynamics of human helminth infections: control by chemotherapy.

An analysis is presented of the population dynamics of the major helminth parasites of man with the aim of understanding observed patterns in the age-specific prevalence and intensity of infection. Mathematical models are used to investigate the possibility of controlling helminth diseases by mass chemotherapy, and to explore the advantages of selective treatment of the most heavily infected individuals in a community.

Adolescent↗
PubMed1982

Directly transmitted infections diseases: control by vaccination.

Mathematical models for the dynamics of directly transmitted viral and bacterial infections are guides to the understanding of observed patterns in the age specific incidence of some common childhood diseases of humans, before and after the advent of vaccination programs. For those infections that show recurrent epidemic behavior, the interepidemic period can be related to parameters characterizing the infection (such as latent and infectious periods and the average age of first infection); this relation agrees with the data of a variety of childhood diseases. Criteria for the eradication of a disease are given, in terms of the proportion of the population to be vaccinated and the age-specific vaccination schedule. These criteria are compared with a detailed analysis of the vaccination programs against measles and whooping cough in Britain, and estimates are made of the levels of protection that would be needed to eradicate these diseases.

Age Factors↗
PubMed1981

Population dynamics of fox rabies in Europe.

A simple mathematical model for the overall dynamics of the interaction between fox populations and rabies is presented. The model helps to explain epidemiological patterns observed in Europe, including the 3 to 5 year cycle in fox populations infected with rabies, threshold densities and average levels of prevalence of infection. We give a quantitative discussion of the possibilities of controlling rabies by culling or vaccinating foxes (or by a mixture of the two).

Animals↗
PubMed1979

Population biology of infectious diseases: Part II.

In the first part of this two-part article (Nature 280, 361--367), mathematical models of directly transmitted microparasitic infections were developed, taking explicit account of the dynamics of the host population. The discussion is now extended to both microparasites (viruses, bacteria and protozoa) and macroparasites (helminths and arthropods), transmitted either directly or indirectly via one or more intermediate hosts. Consideration is given to the relation between the ecology and evolution of the transmission processes and the overall dynamics, and to the mechanisms that can produce cyclic patterns, or multiple stable states, in the levels of infection in the host population.

Bacterial Infections↗
PubMed1979

Population biology of infectious diseases: Part I.

If the host population is taken to be a dynamic variable (rather than constant, as conventionally assumed), a wider understanding of the population biology of infectious diseases emerges. In this first part of a two-part article, mathematical models are developed, shown to fit data from laboratory experiments, and used to explore the evolutionary relations among transmission parameters. In the second part of the article, to be published in next week's issue, the models are extended to include indirectly transmitted infections, and the general implications for infectious diseases are considered.

Animals↗
PubMed1979

Prevalence of schistosome infections within molluscan populations: observed patterns and theoretical predictions.

The paper draws together a large and scattered body of empirical evidence concerning the prevalence of snail infection with schistosome parasites in field situations, the duration of the latent period of infection in snails (and its dependence on temperature), and the mortality rates of infected and uninfected snails in field and laboratory conditions. A review and synthesis of quantitative data on the population biology of schistosome infections within the molluscan host is attempted and observed patterns of infection are compared with predictions of a schistosomiasis model developed by May (1977) which incorporates differential snail mortality (between infected and uninfected snails) and latent periods of infection. It is suggested that the low levels of prevalence within snail populations in endemic areas of schistosomiasis are closely associated with high rates of infected snail mortality and the duration of the latent period of infection within the mollusc. In certain instances, the expected life-span of an infected snail may be less than the duration of the latent period of infection. Such patterns generate very low levels of parasite prevalence. A new age prevalence model for schistosome infections within snail populations is developed and its predictions compared with observed patterns. The implications of this study of observed and predicted patterns of snail infection within molluscan populations are discussed in relation to the overall transmission dynamics of schistosomiasis.

Animals↗
PubMed1978

Consequences of helminth aggregation for the dynamics of schistosomiasis.

The distribution of schistosome worms among their human hosts is not random but aggregated. The consequences of introducing aggregation into models of schistosomiasis transmission, especially that of Macdonald, are explored. There are two possibilities for aggregation, with the sexes distributed either independently or together. Both have profound though differing effects on the breakpoint concept, which is largely destroyed when the sexes are aggregated together, and Macdonald's epidemiological conclusions are not robust to variations from the Poisson distribution. The conclusion from his model that if schistosome densities in man are reduced appropriately the infection will spontaneously proceed to extinction even in the presence of conditions suitable for transmission, is also not therefore robust.

Humans↗