Transmission dynamics of Echinococcus multilocularis; its reproduction number, persistence in an area of low rodent prevalence, and effectiveness of control

Parasitology ◽  
2005 ◽  
Vol 131 (1) ◽  
pp. 133-140 ◽  
Author(s):  
K. TAKUMI ◽  
J. VAN DER GIESSEN
Keyword(s):  
Life Cycle ◽  
Intermediate Host ◽  
Central Europe ◽  
Definitive Host ◽  
Echinococcus Multilocularis ◽  
Reproduction Number ◽  
Parasite Burden ◽  
Host Population ◽  
Total Biomass ◽  
Control Campaign

On the basis of high prevalences of Echinococcus multilocularis in the growing fox populations in Central Europe, its total biomass may have increased significantly in the past 20 years. E. multilocularis is now also found in areas outside the known endemic area in Central Europe. Therefore, E. multilocularis, the causative agent of a serious parasitic zoonosis, might be of major concern for public health and a challenge to control. Some experimental field trials to control E. multilocularis using an anti-worm drug reduced parasite burden in a contaminated region during the control campaign, but failed to eradicate the parasite completely. It was our aim to develop a mathematical model describing the biomass of egg, larval, and adult worm stages of the E. multilocularis life-cycle, and simulate a hypothetical control campaign. Additionally, we derived the reproduction number of this parasite and explored conditions for the persistence of the parasite's life-cycle. Our model shows that while control campaigns rapidly reduce the worm burden in the definitive host, and consequently eggs in the environment, the pool of larvae in the intermediate host remains large. The parasite's life-cycle persists in a region where prevalence in the intermediate host is low (∼1%). Therefore, we conclude that the parasite is likely to re-emerge if control is discontinued on the basis of reduced worm population. Continued treatment of the definitive host is required to eradicate the larval stage of the parasite from the intermediate host population.

Smelling the future: subtle life-history adjustments in response to environmental conditions and perceived transmission opportunities in a trematode

Parasitology ◽  
2016 ◽  
Vol 144 (4) ◽  
pp. 464-474 ◽  
Author(s):  
C. LAGRUE ◽  
R. RINNEVALLI ◽  
R. POULIN
Keyword(s):  
Life History ◽  
Life Cycle ◽  
Intermediate Host ◽  
Definitive Host ◽  
Environmental Conditions ◽  
Life History Strategy ◽  
Host Density ◽  
Life Cycles ◽  
Life History Strategies ◽  
Priming Effects

SUMMARYA number of parasites with complex life cycles can abbreviate their life cycles to increase the likelihood of reproducing. For example, some trematodes can facultatively skip the definitive host and produce viable eggs while still inside their intermediate host. The resulting shorter life cycle is clearly advantageous when transmission probabilities to the definitive hosts are low. Coitocaecum parvum can mature precociously (progenesis), and produce eggs by selfing inside its amphipod second intermediate host. Environmental factors such as definitive host density and water temperature influence the life-history strategy adopted by C. parvum in their crustacean host. However, it is also possible that information about transmission opportunities gathered earlier in the life cycle (i.e. by cercariae-producing sporocysts in the first intermediate host) could have priming effects on the adoption of one or the other life strategy. Here we document the effects of environmental parameters (host chemical cues and temperature) on cercarial production within snail hosts and parasite life-history strategy in the amphipod host. We found that environmental cues perceived early in life have limited priming effects on life-history strategies later in life and probably account for only a small part of the variation among conspecific parasites. External cues gathered at the metacercarial stage seem to largely override potential effects of the environmental conditions experienced by early stages of the parasite.

Lack of seasonal variation in the life-history strategies of the trematode Coitocaecum parvum: no apparent environmental effect

Parasitology ◽  
2008 ◽  
Vol 135 (10) ◽  
pp. 1243-1251 ◽  
Author(s):  
C. LAGRUE ◽  
R. POULIN
Keyword(s):  
Life History ◽  
Seasonal Variation ◽  
Life Cycle ◽  
Water Temperature ◽  
Intermediate Host ◽  
Definitive Host ◽  
Natural Environment ◽  
Life History Strategy ◽  
Life Cycles ◽  
Coitocaecum Parvum

SUMMARYParasites with complex life cycles have developed numerous and very diverse adaptations to increase the likelihood of completing this cycle. For example, some parasites can abbreviate their life cycles by skipping the definitive host and reproducing inside their intermediate host. The resulting shorter life cycle is clearly advantageous when definitive hosts are absent or rare. In species where life-cycle abbreviation is facultative, this strategy should be adopted in response to seasonally variable environmental conditions. The hermaphroditic trematode Coitocaecum parvum is able to mature precociously (progenesis), and produce eggs by selfing while still inside its amphipod second intermediate host. Several environmental factors such as fish definitive host density and water temperature are known to influence the life-history strategy adopted by laboratory raised C. parvum. Here we document the seasonal variation of environmental parameters and its association with the proportion of progenetic individuals in a parasite population in its natural environment. We found obvious seasonal patterns in both water temperature and C. parvum host densities. However, despite being temporally variable, the proportion of progenetic C. parvum individuals was not correlated with any single parameter. The results show that C. parvum life-history strategy is not as flexible as previously thought. It is possible that the parasite's natural environment contains so many layers of heterogeneity that C. parvum does not possess the ability to adjust its life-history strategy to accurately match the current conditions.

A comparative study of the life-histories of mammalian schistosomes

Parasitology ◽  
1983 ◽  
Vol 87 (2) ◽  
pp. 343-369 ◽  
Author(s):  
Eric S. Loker
Keyword(s):  
Life Cycle ◽  
Adult Worm ◽  
Intermediate Host ◽  
Definitive Host ◽  
Life Histories ◽  
Egg Production ◽  
Patent Period ◽  
Shell Size ◽  
Progeny Size ◽  
Facultative Parthenogenesis

SUMMARYAvailable data in the literature pertaining to the life-history characteristics of all known species of mammalian schistosomes have been gathered, and correlations between such variables as length of pre-patent period, adult worm size, rate of progeny production and progeny size have been explored. Accommodation of the schistosome life-cycle to the constraints imposed by certain host characteristics such as life-expectancy and size is discussed. Of the 23 known species of mammalian schistosomes, 20 species apparently rely to a major extent on relatively large-bodied and long-lived mammals such as primates, ungulates and proboscideans for their transmission. Only 1 species,Schistosomatium douthitti, is exclusively dependent on rodents for its transmission.S. douthittiattains maturity within its definitive host faster than any other mammalian schistosome, and is the only species known to be capable of producing viable eggs by facultative parthenogenesis. For all species of mammalian schistosomes, adult worm size, as estimated by female length, is positively correlated with the number of uterine eggs contained within the female (r= 0·682). For the 7 species for which data exist, rate of egg production/worm pair/day is positively correlated with uterine egg counts (r= 0·873) and inversely correlated with egg length (r= −0·787) and miracidium length (r= −0·953). Length of the pre-patent period is positively correlated with egg length (r= 0·503). With respect to the molluscan host, the number of cercariae produced by snails is positively correlated with the shell size of the snail (r= 0·657). For the 5 species for which data exist, the rate of egg production is inversely correlated with shell size of the intermediate host (r= −0·955) and the common logarithm of the number of cercariae produced (r= −0·893). Comparisons between species suggest that exceptionally low rates of cercariae production in the intermediate host may be compensated for by rapid rates of egg production in the definitive host, implying a degree of integration in the schistosome life-cycle not previously appreciated. Most species of mammalian schistosomes have long-lived definitive hosts, and snail hosts capable of producing many cercariae; compensatory relationships are therefore less obvious in such species. Additional quantitative data on all aspects of schistosome life-histories, particularly rate and duration of egg production, are needed to confirm or refute the relationships discussed above.

The effect of Toxoplasma gondii and other parasites on activity levels in wild and hybrid Rattus norvegicus

Parasitology ◽  
1994 ◽  
Vol 109 (5) ◽  
pp. 583-589 ◽  
Author(s):  
J. P. Webster
Keyword(s):  
Life Cycle ◽  
Toxoplasma Gondii ◽  
Intermediate Host ◽  
Definitive Host ◽  
Rattus Norvegicus ◽  
Parasite Load ◽  
Life Cycles ◽  
Parasitic Infections ◽  
Activity Levels ◽  
In The Wild

Using both correlational and experimental evidence, the relationship between parasite load and host activity was assessed in brown rats, Rattus norvegicus. Two hypotheses were tested – (1) that parasites with indirect life-cycles, involving transmission between a prey and its predator, will alter the activity of the intermediate host so as to increase its susceptibility to predation by the definitive host and (2) that activity levels in parasitized rats would be increased rather than decreased. Four groups of rats (n = 140) were examined. One group (n = 50) were wild brown rats trapped from 3 UK farmsteads, with naturally occurring parasites. The others were purpose-bred wild/laboratory hybrid rats with experimentally induced parasitic infections of either (n = 15) adult-acquired or (n = 15) congenitally-acquired Toxoplasma gondii (an indirect life-cycle parasite), or (n = 15) Syphacia muris (a direct life-cycle parasite). Uninfected hybrid rats (n = 45), matched for sex, age and weight, served as controls. Rats were housed individually in outdoor cages, and their activities were recorded on video-tapes for 6 non-consecutive 10 h nights. Exercise wheels were also available for the hybrid rats. Out of 6 parasite species detected in the wild rats, T. gondii was the only one which required predation by a definitive host to complete its life-cycle, and was also the only parasite to be associated with higher activity levels in infected than uninfected rats. Hybrid rats infected with T. gondii were also more active than those uninfected, whereas there were no differences in activity levels between S. muris infected and uninfected rats. This study shows that the indirect life-cycle parasite T. gondii can influence the activity of its intermediate host the rat. I suggest that this may facilitate its transmission to the cat definitive host.

Combining data from morphological traits and genetic markers to determine transmission cycles in the tape worm, Echinococcus granulosus

Parasitology ◽  
1998 ◽  
Vol 117 (2) ◽  
pp. 185-192 ◽  
Author(s):  
A. J. LYMBERY
Keyword(s):  
Life Cycle ◽  
Intermediate Host ◽  
Host Range ◽  
Genetic Markers ◽  
Definitive Host ◽  
Host Species ◽  
Phenotypic Variance ◽  
Blade Length ◽  
Total Length ◽  
Transmission Cycles

Species of Echinococcus (Cestoda: Taeniidae) require 2 mammalian hosts to complete their life-cycle; a carnivorous definitive host, and a herbivorous or omnivorous intermediate host. For most species of Echinococcus, the definitive host range is restricted to 1 or a few species, but the intermediate host range is very broad. Programmes to control hydatid disease attempt to break the life-cycle of the parasite and their effectiveness is therefore enhanced by an understanding of local patterns of transmission. Although it is known that the rostellar hooks of protoscoleces may be influenced by the species of intermediate host in which they develop, the application of this knowledge to infer transmission cycles has been limited, because the intermediate host effect has not been isolated from other environmental and genetic components of phenotypic variance. This study presents a method for separating these potentially confounding genetic and environmental effects, by combining quantitative genetic analyses of hook traits with data on population structure from neutral genetic markers. The method was applied to 5 hook traits (hook number, total length of large hooks, blade length of large hooks, total length of small hooks, blade length of small hooks) measured on protoscoleces from 2 intermediate host types (sheep and macropod marsupials) in Australia. Although genetic variance was similar for all traits, they differed markedly in the extent of environmental variance attributed to development in different host types. Total length of small hooks was the trait most affected, with 49–60% of phenotypic variance being explained by environmental differences between intermediate host species. Blade length of small hooks was least affected, with none of the phenotypic variance due to intermediate host origin. These data suggest that hook measurements of adult worms from naturally infected definitive hosts could be used to determine the intermediate host species from which infection was acquired, if the appropriate traits are measured.

scholarly journals Parasites are Particularly Problematic

2018 ◽  
Vol 2 ◽  
pp. e25604
Author(s):  
Susan Perkins
Keyword(s):  
Life Cycle ◽  
Intermediate Host ◽  
Information Content ◽  
Definitive Host ◽  
Complex Life Cycle ◽  
Phylogenetic Study ◽  
Biodiversity Informatics ◽  
Malaria Parasites ◽  
Parasitic Organism

Although they are hyperdiverse and intensively studied, parasites present major challenges when it comes to phylogenetics, taxonomy, and biodiversity informatics. The collection of any parasitic organism entails the linking of at least two specimens - the parasite and the host. If the parasite has a complex life cycle, then this becomes further complicated by requiring the linking of three or more hosts, such as the parasite, its intermediate host (vector) and its definitive host(s). Parasites are sometimes collected as byproduct of another collection event and are not studied immediately - which has the potential to disconnect them further in terms of information content and continuity- and the converse if also common - parasites can be collected by parasitologists, who do not necessarily take host vouchers or incorporate host taxonomy, let alone other metadata for these events. Using the specific example of the malaria parasites (Order Haemosporida) I will present examples of the specific challenges that have accompanied the study of these parasites including issues of delimiting species, phylogenetic study, including genetic oddities that are unique to these organisms, and taxonomic quandries that we now find ourselves in, along with other problems with maintaining continuity of information in a group that is both diverse biologically and important medically.

The Life History of Gastrodiscoides hominis (Lewis and McConnel, 1876) Leiper, 1913– the Amphistome Parasite of Man and Pig

1972 ◽  
Vol 46 (1) ◽  
pp. 35-46 ◽  
Author(s):  
S. C. Dutt ◽  
H. D. Srivastava
Keyword(s):  
Life History ◽  
Life Cycle ◽  
Intermediate Host ◽  
Definitive Host ◽  
Growth And Development ◽  
Snail Host ◽  
Adult Fluke ◽  
History Of

The life cycle of Gastrodiscoidcs hominis has been described using Helicorbis coenosus as the experimental intermediate host and the pig as the definitive host.The morphology of the miracidium, redia and metacercaria has been described. Data have been furnished on the infection and longevity, of and production of cercariae by the snail host, and the growth and development of the adult-fluke in the definitive host.

scholarly journals Management of Hydatid Cyst of the Spleen. A Case Report

2020 ◽  
Vol 1 (1) ◽  
pp. 01-03
Author(s):  
Yakoubi Becherki
Keyword(s):  
Case Report ◽  
Life Cycle ◽  
Hydatid Cyst ◽  
Intermediate Host ◽  
Echinococcus Granulosus ◽  
Hydatid Disease ◽  
Definitive Host ◽  
The Body ◽  
Human Beings ◽  
Larval Form

Echinococcosis (hydatid disease) primarily affects the liver; however, secondary involvement due to hematogenous dissemination may be seen in almost any anatomic location. Isolated hydatid disease of the spleen is rare (1, 2). It is caused by the larval form of the tapeworm Echinococcus granulosus, E. multilocularis, E. vogeli, or E. oligarthrus. E. granulosus is the most common organism involved, with dogsEchinoccocus granulosus; splenic hydatid; Laparotomy as the definitive host and sheep as an intermediate host. Human beings exposed to certain stages of the life cycle of the organism are also an intermediate host. Human hydatid disease can involve the liver (55%–70%), lung (18%–35%), spleen, kidney, peritoneal cavity, skin and muscles (<2%) and rarely the remaining parts of the body.

Life cycle of Gnathostoma nipponicum Yamaguti, 1941

1992 ◽  
Vol 66 (1) ◽  
pp. 53-61 ◽  
Author(s):  
K. Ando ◽  
H. Tokura ◽  
H. Matsuoka ◽  
D. Taylor ◽  
Y. Chinzei
Keyword(s):  
Life Cycle ◽  
Intermediate Host ◽  
Experimental Infection ◽  
Definitive Host ◽  
Field Survey ◽  
Paratenic Host ◽  
Third Stage ◽  
Second Intermediate Host ◽  
First Intermediate Host

ABSTRACTThe life cycle of Gnathostoma nipponicum was examined by field survey and by experimental infection of animals with the larvae. Naturally infected larval G. nipponicum were found in loaches, catfish, and snakes. Experimentally, loaches, killifishes, frogs, salamanders, mice, and rats were successfully infected with the early third-stage larvae of G. nipponicum obtained from copepods (the first intermediate host), whereas snakes, quails, and weasels were not. Frogs, snakes, quails, and rats were experimentally infected with the advanced third-stage larvae (AdL3) from loaches. These results reveal that some species of fishes, amphibians and mammals can act as the second intermediate host and that some species of reptiles, birds and mammals can act as a paratenic host. The life cycle was completed in weasels, the definitive host, which were infected with AdL3 from loaches and started to evacuate eggs of G. nipponicum in faeces on days 65–90 postinfection.

An acanthocephalan parasite boosts the escape performance of its intermediate host facing non-host predators

Parasitology ◽  
2008 ◽  
Vol 135 (8) ◽  
pp. 977-984 ◽  
Author(s):  
V. MEDOC ◽  
J.-N. BEISEL
Keyword(s):  
Life Cycle ◽  
Intermediate Host ◽  
Definitive Host ◽  
Complex Life Cycle ◽  
Escape Performance ◽  
Intermediate Hosts ◽  
Host Condition ◽  
Gammarus Roeseli ◽  
The Cost ◽  
Acanthocephalan Parasite

SUMMARYAmong the potential effects of parasitism on host condition, the ‘increased host abilities’ hypothesis is a counterintuitive pattern which might be predicted in complex-life-cycle parasites. In the case of trophic transmission, a parasite increasing its intermediate host's performance facing non-host predators improves its probability of transmission to an adequate, definitive host. In the present study, we investigated the cost of infection with the acanthocephalanPolymorphus minutuson the locomotor/escape performance of its intermediate host, the crustaceanGammarus roeseli. This parasite alters the behaviour of its intermediate host making it more vulnerable to predation by avian definitive hosts. We assessed the swimming speeds of gammarids using a stressful treatment and their escape abilities under predation pressure. Despite the encystment ofP. minutusin the abdomen of its intermediate host, infected amphipods had significantly higher swimming speeds than uninfected ones (increases of up to 35%). Furthermore, when interacting with the non-host crustacean predatorDikerogammarus villosus, the highest escape speeds and greatest distances covered by invertebrates were observed for parasitized animals. The altered behaviour observed among the manipulated invertebrates supported the ‘increased host abilities’ hypothesis, which has until now remained untested experimentally. The tactic of increasing the ability of infected intermediate hosts to evade potential predation attempts by non-host species is discussed.

Sign in / Sign up

Export Citation Format

Share Document