scholarly journals Effects of vertical position on trematode parasitism in larval anurans

2019 ◽  
Vol 65 (6) ◽  
pp. 657-664
Author(s):  
Jacob R Jones ◽  
Camille L Steenrod ◽  
John A Marino
Keyword(s):  
Infection Risk ◽  
Adaptive Significance ◽  
Vertical Position ◽  
Intermediate Hosts ◽  
Vertical Variation ◽  
Near Surface ◽  
Host Parasite ◽  
Parasite Behavior ◽  
Future Work ◽  
Parasite Dynamics

Abstract Spatial distributions of animals can affect interactions with their natural enemies, such as parasites, and thus have important implications for host–parasite dynamics. While spatial variation in infection risk has been explored in many systems at the landscape scale, less attention has been paid to spatial structure at smaller scales. Here, we explore a hypothesized relationship between a common spatial variable, vertical position, and risk of parasite infection in a model aquatic system, larval frogs (Rana) and trematode (Digenea) parasites. Vertical position is relevant to this system given evidence that the densities of snail first intermediate hosts, tadpole second intermediate hosts, and trematode infective stages can vary with depth. To test the effects of depth on infection risk of larval frogs by trematodes, we performed two enclosure experiments, one in the laboratory and one in the field, in which larval frogs in cages just below the water surface or near the bottom of the water column were exposed to parasites. Compared with near-surface cages, mean infection load (number of cysts) in tadpoles in near-bottom cages was 83% higher after 48-h exposures in the laboratory and 730% higher after 10-day exposures in the field. Our findings thus indicate that infection risk depends on depth, which may have adaptive significance, as tadpoles have previously been shown to change vertical position in response to parasite presence. These results motivate future work examining vertical variation in infection risk and may have broader implications for host–parasite dynamics and evolution of host and parasite behavior.

Susceptibilities of Various Snail Intermediate Hosts of Schistosoma mansoni to Different Strains of the Parasite

1965 ◽  
Vol 39 (4) ◽  
pp. 363-376 ◽  
Author(s):  
M.F.A. Saoud
Keyword(s):  
Puerto Rico ◽  
Schistosoma Mansoni ◽  
Intermediate Hosts ◽  
Considerable Evidence ◽  
The Past ◽  
Host Parasite Relationship ◽  
Parasite Relationship ◽  
Different Strains ◽  
Host Parasite ◽  
Comprehensive Studies

In the past two decades, considerable evidence has accumulated in the literature about the differences in the susceptibility of various intermediate hosts of Schistosoma mansoni to different strains of the parasite. Comprehensive studies on this aspect of host-parasite relationship have been published by Files & Cram (1949), Abdel-Malek (1950) and Files (1951). The results of more recent studies have been reported by Wright (1962) and Saoud (1964).In the present paper, the writer has studied the susceptibility of four intermediate hosts of S. mansoni from Brazil, Puerto Rico, Egypt and Tanganyika to some strains of the parasite.

scholarly journals A Bit of Sex Stabilizes Host–Parasite Dynamics

2001 ◽  
Vol 212 (3) ◽  
pp. 345-354 ◽  
Author(s):  
THOMAS FLATT ◽  
NICOLAS MAIRE ◽  
MICHAEL DOEBELI
Keyword(s):  
Host Parasite ◽  
Parasite Dynamics

Host-parasite dynamics and the evolution of host immunity and parasite fecundity strategies

1997 ◽  
Vol 59 (3) ◽  
pp. 427-450 ◽  
Author(s):  
Veijo Kaitala ◽  
Mikko Heino ◽  
Wayne M. Getz
Keyword(s):  
Host Immunity ◽  
Host Parasite ◽  
Parasite Dynamics

Insights into the molecular basis of host behaviour manipulation by Toxoplasma gondii infection

2017 ◽  
Vol 1 (6) ◽  
pp. 563-572 ◽  
Author(s):  
Pierre-Mehdi Hammoudi ◽  
Dominique Soldati-Favre
Keyword(s):  
Toxoplasma Gondii ◽  
Stress Responses ◽  
Molecular Mechanisms ◽  
Brain Regions ◽  
Intermediate Hosts ◽  
Toxoplasma Gondii Infection ◽  
Host Parasite ◽  
Host Behaviour ◽  
The Brain ◽  
Brain Homeostasis

Typically illustrating the ‘manipulation hypothesis’, Toxoplasma gondii is widely known to trigger sustainable behavioural changes during chronic infection of intermediate hosts to enhance transmission to its feline definitive hosts, ensuring survival and dissemination. During the chronic stage of infection in rodents, a variety of neurological dysfunctions have been unravelled and correlated with the loss of cat fear, among other phenotypic impacts. However, the underlying neurological alteration(s) driving these behavioural modifications is only partially understood, which makes it difficult to draw more than a correlation between T. gondii infection and changes in brain homeostasis. Moreover, it is barely known which among the brain regions governing fear and stress responses are preferentially affected during T. gondii infection. Studies aiming at an in-depth dissection of underlying molecular mechanisms occurring at the host and parasite levels will be discussed in this review. Addressing this reminiscent topic in the light of recent technical progress and new discoveries regarding fear response, olfaction and neuromodulator mechanisms could contribute to a better understanding of this complex host–parasite interaction.

scholarly journals How host phenology impacts multi-season epidemic cycles

2021 ◽  
Author(s):  
Hannelore MacDonald ◽  
Dustin Brisson
Keyword(s):  
Mathematical Model ◽  
Population Dynamics ◽  
Population Cycles ◽  
Seasonal Activity ◽  
Host Interactions ◽  
Host Phenology ◽  
Demographic Impact ◽  
Host Parasite ◽  
Parasite Populations ◽  
Parasite Dynamics

Parasite-host interactions can result in periodic population dynamics when parasites over-exploit host populations. The timing of host seasonal activity, or host phenology, determines the frequency and demographic impact of parasite-host interactions which may govern if the parasite can sufficiently over-exploit their hosts to drive population cycles. We describe a mathematical model of a monocyclic, obligate-killer parasite system with seasonal host activity to investigate the consequences of host phenology on host-parasite dynamics. The results suggest that parasites can reach the densities necessary to destabilize host dynamics and drive cycling in only some phenological scenarios, such as environments with short seasons and synchronous host emergence. Further, only parasite lineages that are sufficiently adapted to phenological scenarios with short seasons and synchronous host emergence can achieve the densities necessary to over-exploit hosts and produce population cycles. Host-parasite cycles can also generate an eco-evolutionary feedback that slows parasite adaptation to the phenological environment as rare advantageous phenotypes are driven to extinction when introduced in phases of the cycle where host populations are small and parasite populations are large. The results demonstrate that seasonal environments can drive population cycling in a restricted set of phenological patterns and provides further evidence that the rate of adaptive evolution depends on underlying ecological dynamics.

scholarly journals Community diversity reduces Schistosoma mansoni transmission, host pathology and human infection risk

2009 ◽  
Vol 276 (1662) ◽  
pp. 1657-1663 ◽  
Author(s):  
Pieter T.J Johnson ◽  
Peder J Lund ◽  
Richard B Hartson ◽  
Timothy P Yoshino
Keyword(s):  
Community Structure ◽  
Schistosoma Mansoni ◽  
Host Density ◽  
Biodiversity Loss ◽  
Infection Risk ◽  
Human Infection ◽  
Host Community ◽  
Community Diversity ◽  
Complex Life Cycle ◽  
Intermediate Hosts

Global biodiversity loss and disease emergence are two of the most challenging issues confronting science and society. Recently, observed linkages between species-loss and vector-borne infections suggest that biodiversity may help reduce pathogenic infections in humans and wildlife, but the mechanisms underlying this relationship and its applicability to a broader range of pathogens have remained speculative. Here, we experimentally evaluated the effects of host community structure on transmission of the human pathogen, Schistosoma mansoni , which alternates between snail intermediate hosts and vertebrate definitive hosts. By manipulating parasite exposure and community diversity, we show that heterospecific communities cause a 25–50 per cent reduction in infection among snail hosts ( Biomphalaria glabrata ). Infected snails raised alongside non-host snails ( Lymnaea or Helisoma sp.) also produced 60–80 per cent fewer cercariae, suggesting that diverse communities could reduce human infection risk. Because focal host density was held constant during experiments, decreases in transmission resulted entirely from diversity-mediated pathways. Finally, the decrease in infection in mixed-species communities led to an increase in reproductive output by hosts, representing a novel example of parasite-mediated facilitation. Our results underscore the significance of community structure on transmission of complex life-cycle pathogens, and we emphasize enhanced integration between ecological and parasitological research on the diversity–disease relationship.

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