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).

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0031182000052847

Density-dependent mechanisms in the regulation of intestinal helminth populations

Parasitology The Biology of Animal Parasites. By Prof. Elmer R. Noble and Dr. Glenn A. Noble. Pp. 767. (London: Henry Kimpton, 1961.) 82s 6d.

Biology of Parasites

The effect of immunosuppressants on the development of Hymenolepis diminuta in mice.

Immunity and Hymenolepis diminuta.

The hen flea Ceratophyllus gallinae (Siphonaptera: Ceratophyllidae) is a common ectoparasite in Blue Tit Parus caeruleus nests, whereby adult fleas draw blood from the incubating female host and from the nestlings. Host-parasite interactions are influenced by density-dependent growth of the parasite population, which may result from competitive exploitation or interference between parasite individuals, or from density- dependent host defenses. Understanding density dependence in host-parasite interactions is important for understanding the evolution of parasite virulence and of host defense. Here we investigate density-dependent processes in the dynamics of flea subpopulations. In a first experiment, intended to establish the importance of density dependence in this host- parasite system, the founder density of parasites was manipulated, and reproductive rates of parasites measured. A second experiment was designed to identify the demographic levels at which density dependence arises in the growth of the hen flea population. The experiments show that parasite reproductive rates significantly decrease with increasing founder density. The patterns of egg production, larval production, and adult flea survival suggest that competition between larvae is the main process behind the density-dependent pattern of subpopulation growth. Host mortality, body condition, and blood hematocrit level of the female host and the nestlings were not significantly affected by parasite load, sug- gesting that adult fleas are not food limited at high densities.

/pdf/density-dependent-processes-in-the-population-dynamics-of-a-3lb4izp6sf.pdf

Density-dependent processes in the population dynamics of a bird ectoparasite ceratophyllus gallinae

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/E74A21D6DF0325B67C0AC91FBC8374F4/S0031182000071511a.pdf/div-class-title-the-nature-of-the-immune-response-of-the-mouse-to-the-bile-duct-cestode-span-class-italic-hymenolepis-microstoma-span-div.pdf

G. D. Moss

Papers

The nature of the immune response of the mouse to the bile duct cestode, Hymenolepis microstoma

The effect of cortisone acetate treatment on the growth of Hymenolepis microstoma in mice