Studies With the Strongyloid Nematode, Haemonchus Contortus. Ii. Potential Infestation Curves Under Conditions of Natural Reinfection*

Stoll, Norman R.

doi:10.1093/oxfordjournals.aje.a117884

Cited by 10 publications

(14 citation statements)

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“…The interpretation of possible mechanisms of population regulation in intestinal nematode infections is complicated by the existence of two phenomena which are as yet not thought to be involved to any large extent in the dynamics of cestodes and acanthocephalans, namely 'self-cure' (Stoll, 1929) and hypobiosis (see Michel, 1974). Both are to a greater or lesser extent considered to be related to the complexity of host-generated immune responses (Dobson, 1972) although arrested development may also be dependent on both environmental and parasite-related factors (Schad, 1977).…”

Section: Nematodesmentioning

confidence: 99%

Density-dependent mechanisms in the regulation of intestinal helminth populations

Keymer

1982

Parasitology

145

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The regulation of helminth populations tends to occur primarily as a result of limitations imposed on the build up of parasite subpopulations within individual hosts (Anderson & May, 1979; May & Anderson, 1979). Considering the relevance of these factors to the success or otherwise of intestinal helminth control programmes, it is perhaps surprising that more information is not yet available concerning the particular mechanisms which may be responsible, and in particular, the population consequences of the immune responses which such parasites may precipitate. Density-dependence in a single rate parameter, if operative over the naturally observed numerical range, is sufficient to regulate parasite population flow throughout the life-cycle, whether direct or indirect (Anderson, 1976). For the genera given in Table 1, this could be provided by the observed pattern of parasite mortality and/or fecundity. It is of interest to note, however, that circumstantial evidence cited in the Table suggests that each of the 6 genera is also potentially able to induce host mortality under certain conditions. Whether this acts in a density-dependent manner in natural infections is almost entirely unknown. Rapid reproduction may be of great selective advantage to intestinal helminths, even if it is necessarily accompanied by pathogenicity (see Anderson, 1981). If the manner in which this pathogenicity acts in any way enhances the stability of the host-parasite interaction, then perhaps it may have contributed to the selection pressures which have led so many genera to continue to break the rules of the ‘well-adapted’ parasite (see, for example, Noble & Noble, 1971).

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Section: Nematodesmentioning

confidence: 99%

Density-dependent mechanisms in the regulation of intestinal helminth populations

Keymer

1982

Parasitology

145

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“…The following are examples of helminths which appear to reach sexual maturity in the sites initially occupied by their immature stages, and without any major change: Acanthocephala, P o~~o r p h u s minutus (Crompton & Whitfield, 1968 b ;Lingard & Crompton, 1972); Cestoda, Echinococcus granulosus (Smyth, Gemmell & Smyth, 1970), Hydatigera taeniaeformis (Hutchison, 1959) and Hymenolepis exigua (Alicata & Chang, 1939) ; Nematoda, Ancylostoma caninum (Krupp, 1961)) Trichinella spiralis (Larsh & Hendricks, 1949)) Strongyloides ratti and S. venexuelensis (Wertheim, 1970), Nippostrongylus brasiliensis (Brambell, 1965 ; Alphey, 1970)) Syphacia obvelata (Philpot, 1924)) Physaloptera hispida (Schell, 1952)) Obeliscoides cuniculi (Alicata, 1932), Haemonchus contortus (Veglia, 1915 ;Stoll, 1929) and Trichuris muris (Fahmy, 1954) ; Trematoda, Loxogmes arcanum (Crawford, 1938)) Haplometrana utahmis (Olsen, 1937), Psilostomum ondatrae (Beaver, 1939), Echinoparyphium recurvaturn (Soulsby, 1955) and Alaria canis (Pearson, 1956).…”

Section: (I) Direct Arrivalmentioning

confidence: 99%

The Sites Occupied by Some Parasitic Helminths in the Alimentary Tract of Vertebrates

Crompton

1973

Biological Reviews

134

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Summary 1. The sites occupied by adult helminths in the alimentary tracts of vertebrates, the events leading to the establishment of the helminths in these sites and some of the factors involved in extensions or changes of site have been described and discussed in an attempt to summarize the present state of knowledge and stimulate more research into the ecology of helminths in the tract. 2. In an attempt to reduce confusion and ambiguity in the future literature on the ecology of helminths, definitions have been proposed for the terms site, emigration and migration. 3. Since it has been assumed that the distribution and survival of some species of helminth in the tract are related to phases of digestive activity or inactivity, the morphology, histology and physiology of the alimentary tract of vertebrates have been considered with emphasis on events and features which appear to be of significance to helminths. 4. Many phases of a helminth's association with its host appear to be related to the host's intestinal motility. 5. Digestion in vertebrates is considered to be an ordered sequence of events producing different conditions in different parts of the tract. These conditions, however, are not entirely predictable; digestion is affected by the nature of the diet, the feeding routine and the psychosomatic state of the animal in question. 6. An accurate description of a helminth's site is fundamental to our understanding of its ecology. The description should include information about (I) the helminth's linear distribution, (2) the helminth's radial distribution, (3) the length of time which passed between the death of the host and finding the parasites, (4) the time of day when the search was made, (5) the stage of digestion in progress on the death of the host, (6) the season of the year when the parasites were observed, (7) the parasite's reproductive state and (8) the worm burden and the other species of parasite present in the host's alimentary tract. 7. Special care must be taken when describing the site of a cestode because of the nature of the strobila and the degrees of independent existence shown by the proglot‐tids of certain species. 8. The distribution of sites occupied by the adults of 252 species of helminth in the alimentary tract of vertebrates is given in Tables 2–6, and some sites are illustrated diagrammatically in Figs. 36–57. The sites given in the tables should be accepted with caution, for not all the authors recognized the need for information of the type proposed in paragraph 6 above. 9. The adult stages of most species of Acanthocephala and of most species of Cestoda are confined to the lumen and paramucosal lumen of the small intestines of their hosts. Their mode of feeding and dependence on their hosts' digestive processes fit in with their observed distribution. Acanthocephalans and cestodes are likely to be competitors because their restriction to the small intestine and their feeding behaviour suggest that they may have similar ecological niches. 10. The adult stages of Nematoda ca...

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“…The earliest work in this field, so far as the writer is aware, is that of Stoll (1932), who studied Haemonchtts contort us population growth in sheep.…”

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confidence: 99%

The Extent to which Self-Augmentation of Nematode Parasitism Occurs in Lambs

Tetley

1959

J. Helminthol.

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Studies With the Strongyloid Nematode, Haemonchus Contortus. Ii. Potential Infestation Curves Under Conditions of Natural Reinfection*

Cited by 10 publications

References 0 publications

Density-dependent mechanisms in the regulation of intestinal helminth populations

Density-dependent mechanisms in the regulation of intestinal helminth populations

The Sites Occupied by Some Parasitic Helminths in the Alimentary Tract of Vertebrates

The Extent to which Self-Augmentation of Nematode Parasitism Occurs in Lambs

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