Density dependence

[citation needed] In dioecious (separate sex) obligatory parasites, mated female worms are required to complete a transmission cycle.

[2] Positive density-dependence processes occur in macroparasite life cycles that rely on vectors with a cibarial armature, such as Anopheles or Culex mosquitoes.

For Wuchereria bancrofti, a filarial nematode, well-developed cibarial armatures in vectors can damage ingested microfilariae and impede the development of infective L3 larvae.

[citation needed] There also exists density-independent inhibition, where other factors such as weather or environmental conditions and disturbances may affect a population's carrying capacity.

In the context of gastrointestinal nematodes, the weight of female Ascaris lumbricoides and its rates of egg production decrease as host infection intensity increases.

[6] In macroparasite life cycles, density-dependent processes can influence parasite fecundity, survival, and establishment.

[7] In reality, combinations of negative (restriction) and positive (facilitation) density-dependent processes occur in the life cycles of parasites.

Conversely, in Aedes and Anopheles mosquitoes, which have well-developed cibarial armatures, facilitation processes predominate.

Facilitation processes increase the extinction threshold, making it easier to achieve using parasite control interventions.

[8] Anderson and Gordon (1982) propose that the distribution of macroparasites in a host population is regulated by a combination of positive and negative density-dependent processes.

For instance, time-series data for Onchocerciasis infection demonstrates that 10 years of vector control lead to reduced parasite burden with a more overdispersed distribution.