scispace - formally typeset
Search or ask a question
Journal Article•DOI•

The dynamics of helminth infections, with special reference to schistosomes

George Macdonald1•
University of London1
01 Sep 1965-Transactions of The Royal Society of Tropical Medicine and Hygiene (Trans R Soc Trop Med Hyg)-Vol. 59, Iss: 5, pp 489-506
About: This article is published in Transactions of The Royal Society of Tropical Medicine and Hygiene.The article was published on 1965-09-01. It has received 364 citations till now.
Citations
More filters
Journal Article•DOI•
Population biology of infectious diseases: Part II

[...]

Robert M. May1, Roy M. Anderson2•
Princeton University1, Imperial College London2
02 Aug 1979-Nature
TL;DR: 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.
Abstract: 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.

2,652 citations

Journal Article•DOI•
Thresholds and breakpoints in ecosystems with a multiplicity of stable states

[...]

Robert M. May1•
Princeton University1
01 Oct 1977-Nature
TL;DR: This review discusses how alternate stable states can arise in simple 1- and 2-species systems, and applies these ideas to grazing systems, to insect pests, and to some human host–parasite systems.
Abstract: Theory and observation indicate that natural multi-species assemblies of plants and animals are likely to possess several different equilibrium points. This review discusses how alternate stable states can arise in simple 1- and 2-species systems, and applies these ideas to grazing systems, to insect pests, and to some human host–parasite systems.

1,508 citations

Journal Article•DOI•
On the Evidence Needed to Judge Ecological Stability or Persistence

[...]

Joseph H. Connell, Wayne P. Sousa
01 Jun 1983-The American Naturalist
TL;DR: An analysis of census data from many long-term studies revealed a continuum of temporal variability in the dynamics of natural populations and communities, with no evidence of multiple stable states in unexploited natural populations or communities.
Abstract: "The balance of nature has been a background assumption in natural history since antiquity" (Egerton 1973, p. 322). This continues to be true today; some modern field ecologists, assuming that natural ecosystems are stable, have applied ideas of mathematical stability theory to the actual communities they are studying. We believe that, before one applies such theory to a natural population or community, one should first decide whether or not it is stable. Our aim here is to describe the sorts of evidence one would need to obtain from natural populations or communities in order to decide whether they are stable or persistent, as defined below. One aspect we shall stress in particular is whether any given real community exists in multiple stable states in different places at the same time or in the same place at different times (Sutherland 1974).

1,160 citations

Book Chapter•DOI•
Helminth infections of humans: mathematical models, population dynamics, and control.

[...]

Roy M. Anderson1, Robert M. May2•
Imperial College London1, Princeton University2
01 Jan 1985-Advances in Parasitology
TL;DR: The chapter provides a brief description of observed epidemiological patterns, concentrating on age-prevalence and age-intensity trends and a historical review of the development of the mathematical models of helminth infections.
Abstract: Publisher Summary This chapter reviews the role of mathematical models in the investigations of the population or transmission dynamics of human helminths. It focuses on the biological assumptions employed in model construction, the insights that emerge from model analysis, the comparison of predictions with observed trends, and the estimation of parameter values from epidemiological data. The chapter provides a brief description of observed epidemiological patterns, concentrating on age-prevalence and age-intensity trends and a historical review of the development of the mathematical models of helminth infections. The chapter also discusses mathematical models for schistosome flukes, for intestinal nematodes, and for the filarial infections and the essential features of the models for specific infections to provide a general framework for the description of helminth transmission dynamics. The general framework is presented to consider the design of control policies for helminth infections in human communities.

537 citations

Journal Article•DOI•
Now you See them, Now you don't! – Population Crashes of Established Introduced Species

[...]

Daniel Simberloff1, Leah Gibbons1•
University of Tennessee1
01 Jan 2004-Biological Invasions
TL;DR: Except for the few species in which spontaneous collapse has been repeatedly observed, the possibility of such an event is unwarranted as a potential rationale for a do-nothing approach to management.
Abstract: Substantial populations of invasive non-indigenous species occasionally collapse dramatically. Although disease is often invoked, the causes are rarely studied experimentally and/or quantitatively, and some collapses remain quite mysterious. The widespread invasive snail Achatina fulica and pondweed Elodea canadensis appear to be characterized by rapid expansion followed by rapid decline. For the former species, disease may be the proximal cause of the collapse, while repeated collapse of the latter species is unexplained. Several other widely cited collapses of introduced species may simply be temporary lows during a more or less regular boom-and-bust cycle. However, on a restricted site (such as a small island), a boom-or-bust cycle may be impossible and recovery may never ensue; local extinction may even occur. In several instances, apparently spontaneous crashes were in fact probably caused by subsequently introduced competitors. Except for the few species in which spontaneous collapse has been repeatedly observed, the possibility of such an event is unwarranted as a potential rationale for a do-nothing approach to management. For such species, even if a crash ultimately occurs, the species may already have caused persistent ecological damage.

468 citations

Cites background from "The dynamics of helminth infections..."

  • ...Another prominent, widespread invader seems typically to undergo a characteristically rapid population expansion followed by a crash: the giant African snail, Achatina fulica, introduced to many Pacific islands (Mead 1979; Pointier and Blanc 1985). Initially there is an explosive build-up, with large, vigorous individuals of healthy mien. The population remains at this plateau for an indefinite period, and then there is a general decline, often rapid. Not only do numbers fall, but large specimens become rare or disappear entirely, and many shells are distorted. Locally there is even extinction. Mead (1979) describes a disease syndrome in these populations, with a high frequency of leukodermic lesions associated with the bacterium Aeromonas hydrophila, but exactly what triggers the epizootic is mysterious because the bacterium is omnipresent....

    [...]

  • ...From the standpoint of the pathogen, there is a threshold host density, or breakpoint, necessary to maintain a rate of transmission high enough to allow the pathogen to persist (McKendrick 1940; Macdonald 1965; Anderson 1982)....

    [...]

  • ...Another prominent, widespread invader seems typically to undergo a characteristically rapid population expansion followed by a crash: the giant African snail, Achatina fulica, introduced to many Pacific islands (Mead 1979; Pointier and Blanc 1985). Initially there is an explosive build-up, with large, vigorous individuals of healthy mien. The population remains at this plateau for an indefinite period, and then there is a general decline, often rapid. Not only do numbers fall, but large specimens become rare or disappear entirely, and many shells are distorted. Locally there is even extinction. Mead (1979) describes a disease syndrome in these populations, with a high frequency of leukodermic lesions associated with the bacterium Aeromonas hydrophila, but exactly what triggers the epizootic is mysterious because the bacterium is omnipresent. Waterhouse and Norris (1987) suggest that peak populations may exhaust their food and induce starvation, whereas Mead (1979) says that any stress may make the population more susceptible to the bacterium....

    [...]

References
More filters
Book•
The Epidemiology and Control of Malaria.

[...]

George Macdonald
01 Jan 1957

1,329 citations

Journal Article•DOI•
Urological complications of endemic schistosomiasis in school-children: Part 1. Usagara School☆

[...]

D.M. Forsyth, George Macdonald1•
University of London1
01 Mar 1965-Transactions of The Royal Society of Tropical Medicine and Hygiene
TL;DR: On the basis of urological disease only, endemic urinary schistosomiasis has a considerable adverse effect on the economy of a country such as Tanzania where foci of disease are widespread.
Abstract: An account is given of the effects produced by endemic urinary schistosomiasis upon the children attending different schools in the Mwanza Region of Tanzania. At Usagara, where the incidence of infection rises to become 100% in the children of standard 4, up to 37% of the standard 6 pupils have irreversible lesions of the urinary tract. Nearby, where infection is less prevalent, there is a coincident decrease in lesions of the urinary tract. It is firmly established that the lesions—calcified bladder, deformity of the ureter, and hydronephrosis—are due to schistosomiasis, and that their prevalence is related to the weight of infection. Lesions occur even in the youngest examined, aged 6, but the prevalence of deformity of the ureter probably increases with age. There is a very marked and significant difference between boys and girls, hydronephrosis being much rarer in girls, but other lesions are equally common. On the basis of urological disease only, endemic urinary schistosomiasis has a considerable adverse effect on the economy of a country such as Tanzania where foci of disease are widespread. Pulmonary and systemic hypertension were not seen as complications of urinary schistosomiasis in the children studied, but pathological blood urea levels occur.

63 citations

Related Papers (5)
Togetherness among Schistosomes: its effects on the dynamics of the infection

[...]

01 Jan 1977-Bellman Prize in Mathematical Biosciences
Robert M. May
Helminth infections of humans: mathematical models, population dynamics, and control.

[...]

01 Jan 1985-Advances in Parasitology
Roy M. Anderson, Robert M. May
The transmission dynamics of schistosomiasis

[...]

01 Jul 1973-Communications on Pure and Applied Mathematics
Ingemar Nåsell, Warren M. Hirsch
Infectious Diseases of Humans: Dynamics and Control

[...]

11 Jul 1991
Roy M. Anderson, Robert M. May
Regulation and Stability of Host-Parasite Population Interactions: I. Regulatory Processes

[...]

01 Feb 1978-Journal of Animal Ecology
Roy M. Anderson, Robert M. May