Distribution of Ascaris suum in experimentally and naturally infected pigs and comparison with Ascaris lumbricoides infections in humans

Parasitology ◽  
1998 ◽  
Vol 117 (6) ◽  
pp. 589-596 ◽  
Author(s):  
J. BOES ◽  
G. F. MEDLEY ◽  
L. ERIKSEN ◽  
A. ROEPSTORFF ◽  
P. NANSEN
Keyword(s):  
Worm Burden ◽  
Ascaris Suum ◽  
Natural Infection ◽  
Distribution Patterns ◽  
Human Populations ◽  
Suitable Model ◽  
Post Mortem ◽  
Intensity Of Infection ◽  
Low Intensity ◽  
Low Prevalence

This paper describes the distribution of Ascaris suum in experimentally and naturally infected pigs, and offers a comparison with A. lumbricoides infections in humans. In the first study, worms were recovered post-mortem from a group of 38 pigs that had been trickle inoculated with 10000 infective A. suum eggs twice weekly for 12 weeks. In the second study, worms were collected from a group of 49 pigs that had been kept on a pasture contaminated with infective A. suum eggs for 10 weeks, after which they received treatment with an anthelmintic; they then were turned out on the same pasture for a second 10-week period before slaughter. The worm burdens of the naturally infected pigs were recorded both at treatment and post-mortem. Mean worm counts were similar at all occasions but the prevalence of infection was higher in the trickle infected and naturally reinfected pigs. Furthermore, the prevalence in naturally infected pigs increased significantly over the study period. Worm burden distributions in all groups were heavily overdispersed, but the distribution patterns differed significantly between groups: lower exposure (initial natural infection) gave a low prevalence and an almost uniform distribution of worm burdens among infected hosts. Continued or higher exposure (trickle and natural reinfection) resulted in increased prevalence and a reduction in the proportion of hosts with increasing worm load. A positive correlation was found between initial and reinfection worm burdens in the naturally infected pig population, suggesting that individual pigs are predisposed to a high or low intensity of infection. The prevalence and intensity as well as the distribution observed for A. suum infection in pigs were comparable to those reported for A. lumbricoides in endemic areas, and there is evidence for predisposition to A. suum in pigs, with an estimated correlation coefficient similar to that found in humans. It is concluded that A. suum infections in pigs are a suitable model to study the population dynamics of A. lumbricoides in human populations.

Distribution patterns of Opisthorchis viverrini within a human community

Parasitology ◽  
1991 ◽  
Vol 103 (1) ◽  
pp. 97-101 ◽  
Author(s):  
M. R. Haswell-Elkins ◽  
D. B. Elkins ◽  
Paiboon Sithithaworn ◽  
Phattara Treesarawat ◽  
Sasithorn Kaewkes
Keyword(s):  
Worm Burden ◽  
Distribution Patterns ◽  
Opisthorchis Viverrini ◽  
Parasite Control ◽  
Intensity Of Infection ◽  
Community Based ◽  
Human Community ◽  
Control Programmes ◽  
Over Dispersion ◽  
Antibody Levels

This paper describes patterns of infection with Opisthorchis viverrini within a human community assessed by egg count, parasite-specific antibody levels and worm burden determined by expulsion chemotherapy. All three measurements increased significantly with age, reaching a plateau in young adults. There were no significant sex-associated differences in the prevalence or intensity of infection, antibody levels, or in the frequency of heavy worm burdens. A striking 81·5% of the total Opisthorchis population and 74% of the total egg output were expelled by the most heavily infected 10% of the humans sampled. This extreme over-dispersion, together with recent findings that hepatobiliary disease frequently accompanies heavy infections, argues that the priority for community-based parasite control programmes should be to maximize treatment and health promotion efforts toward heavily infected individuals.

Observations on the use of Trichostrongylus colubriformis (Nematoda) infections of guinea-pigs for laboratory experiments

Parasitology ◽  
1963 ◽  
Vol 53 (1-2) ◽  
pp. 189-199 ◽  
Author(s):  
R. F. Sturrock
Keyword(s):  
Multivariate Analysis ◽  
Guinea Pigs ◽  
Worm Burden ◽  
Laboratory Experiments ◽  
Statistical Treatment ◽  
Post Mortem ◽  
Infective Larvae ◽  
Final Weight ◽  
Cure Mechanism ◽  
Experimental Use

Four groups of guinea-pigs were infected with a range of doses of T. colubriformis. The infections were followed by egg counts and weight measurements, and the adult worms were recovered from the animals post mortem. A multivariate analysis, details of which are given in an appendix, showed that the sensitivity of the measures used was, in descending order, final weight, total egg count and worm burden. The course of the infection is discussed in view of the apparent self-cure mechanism. Precautions are outlined for the experimental use of this hostparasite relationship.The author is grateful to Professor B. G. Peters for his advice on this work, to Dr P. Silverman of Allen and Hanburys Limited for a supply of T. colubriformis infective larvae and to Dr R. E. Blackith for his advice on the statistical treatment of the data.

The regulation ofOstertagia ostertagipopulations in calves: density-dependent control of fecundity

Parasitology ◽  
1987 ◽  
Vol 95 (2) ◽  
pp. 373-388 ◽  
Author(s):  
G. Smith ◽  
B. T. Grenfell ◽  
R. M. Anderson
Keyword(s):  
Worm Burden ◽  
Egg Production ◽  
Inverse Function ◽  
Single Infection ◽  
Intensity Of Infection ◽  
Density Dependent ◽  
Helminth Infections ◽  
Model Predictions ◽  
Initial Peak ◽  
Infection Experiments

SUMMARYThe decline in faecal egg counts, characteristic of calves which have been experimentally infected withOstertagia ostertagi, is analysed using a mathematical model in which parasite fecundity is assumed to be an inverse function of both the duration and intensity of infection. The model incorporates a description of the frequency distribution of mature parasites between hosts (which is less over-dispersed than is usual for many other helminth infections). The model provides a good overall description of the decline in faecal egg production observed during trickle and single infection experiments. The main discrepancy between a comparison of the model predictions and the results of the most detailed available series of trickle infection experiments occurs at the initial peak of egg production. The magnitude of this difference appears to be related to the worm burden at the peak of egg production. The possible mechanisms underlying density-dependent regulation of the fecundity ofO. ostertagiaare discussed.

scholarly journals The impact of mass drug administration expansion to low onchocerciasis prevalence settings in case of connected villages

2021 ◽  
Vol 15 (5) ◽  
pp. e0009011
Author(s):  
Anneke S. de Vos ◽  
Wilma A. Stolk ◽  
Luc E. Coffeng ◽  
Sake J. de Vlas
Keyword(s):  
Intermediate Host ◽  
Drug Administration ◽  
Mass Drug Administration ◽  
Human Populations ◽  
Individual Based Model ◽  
Low Prevalence ◽  
The Impact ◽  
Local Transmission

Background The existence of locations with low but stable onchocerciasis prevalence is not well understood. An often suggested yet poorly investigated explanation is that the infection spills over from neighbouring locations with higher infection densities. Methodology We adapted the stochastic individual based model ONCHOSIM to enable the simulation of multiple villages, with separate blackfly (intermediate host) and human populations, which are connected through the regular movement of the villagers and/or the flies. With this model we explore the impact of the type, direction and degree of connectedness, and of the impact of localized or full-area mass drug administration (MDA) over a range of connected village settings. Principal findings In settings with annual fly biting rates (ABR) below the threshold needed for stable local transmission, persistence of onchocerciasis prevalence can well be explained by regular human traffic and/or fly movement from locations with higher ABR. Elimination of onchocerciasis will then theoretically be reached by only implementing MDA in the higher prevalence area, although lingering infection in the low prevalence location can trigger resurgence of transmission in the total region when MDA is stopped too soon. Expanding MDA implementation to the lower ABR location can therefore shorten the duration of MDA needed. For example, when prevalence spill-over is due to human traffic, and both locations have about equal populations, then the MDA duration can be shortened by up to three years. If the lower ABR location has twice as many inhabitants, the reduction can even be up to six years, but if spill-over is due to fly movement, the expected reduction is less than a year. Conclusions/Significance Although MDA implementation might not always be necessary in locations with stable low onchocerciasis prevalence, in many circumstances it is recommended to accelerate achieving elimination in the wider area.

The evaluation of potential global morbidity attributable to intestinal nematode infections

Parasitology ◽  
1994 ◽  
Vol 109 (3) ◽  
pp. 373-387 ◽  
Author(s):  
M. S. Chan ◽  
G. F. Medley ◽  
D. Jamison ◽  
D. A. P. Bundy
Keyword(s):  
Spatial Heterogeneity ◽  
Ascaris Lumbricoides ◽  
Worm Burden ◽  
Disease Burden ◽  
Trichuris Trichiura ◽  
Intensity Of Infection ◽  
Intestinal Nematode ◽  
Prevalence Estimates ◽  
Global Disease Burden

SummaryThis paper presents a method of estimating the potential global morbidity due to human intestinal nematode infections (Ascaris lumbricoides, Trichuris trichiura and hookworms), based on the observed prevalence of infection. The method relies on the observed relationships between prevalence and intensity of infection, and between worm burden and potential morbidity. This approach is shown to be sensitive to the precision of the original prevalence estimates and, in particular, to the degree of spatial heterogeneity in levels of infection. The estimates presented here indicate that several tens of millions of children are likely to suffer developmental consequences from infection, and suggest that the global disease burden of geohelminthiasis may be significantly greater than was supposed.

Worm burden and immunological responses in Corriedale and Crioula Lanada sheep following natural infection with Haemonchus contortus

2004 ◽  
Vol 51 (1) ◽  
pp. 75-83 ◽  
Author(s):  
P.A Bricarello ◽  
S.M Gennari ◽  
T.C.G Oliveira-Sequeira ◽  
C.M.S.L Vaz ◽  
I Gonçalves de Gonçalves ◽  
...  
Keyword(s):  
Haemonchus Contortus ◽  
Worm Burden ◽  
Natural Infection ◽  
Immunological Responses

scholarly journals A new approach to modelling schistosomiasis transmission based on stratified worm burden

Parasitology ◽  
2010 ◽  
Vol 137 (13) ◽  
pp. 1951-1965 ◽  
Author(s):  
D. GURARIE ◽  
C. H. KING ◽  
X. WANG
Keyword(s):  
Worm Burden ◽  
Field Data ◽  
Ad Hoc ◽  
Negative Binomial ◽  
Traditional Approach ◽  
Human Infection ◽  
World Health ◽  
Human Populations ◽  
Individual Level ◽  
The Impact

SUMMARYBackground/Objective. Multiple factors affect schistosomiasis transmission in distributed meta-population systems including age, behaviour, and environment. The traditional approach to modelling macroparasite transmission often exploits the ‘mean worm burden’ (MWB) formulation for human hosts. However, typical worm distribution in humans is overdispersed, and classic models either ignore this characteristic or make ad hoc assumptions about its pattern (e.g., by assuming a negative binomial distribution). Such oversimplifications can give wrong predictions for the impact of control interventions. Methods. We propose a new modelling approach to macro-parasite transmission by stratifying human populations according to worm burden, and replacing MWB dynamics with that of ‘population strata’. We developed proper calibration procedures for such multi-component systems, based on typical epidemiological and demographic field data, and implemented them using Wolfram Mathematica. Results. Model programming and calibration proved to be straightforward. Our calibrated system provided good agreement with the individual level field data from the Msambweni region of eastern Kenya. Conclusion. The Stratified Worm Burden (SWB) approach offers many advantages, in that it accounts naturally for overdispersion and accommodates other important factors and measures of human infection and demographics. Future work will apply this model and methodology to evaluate innovative control intervention strategies, including expanded drug treatment programmes proposed by the World Health Organization and its partners.

The subtypes of human immunodeficiency virus in Australia and Asia

Sexual Health ◽  
2004 ◽  
Vol 1 (1) ◽  
pp. 1 ◽  
Author(s):  
Robert Oelrichs
Keyword(s):  
Human Immunodeficiency Virus ◽  
Genetic Variability ◽  
Distribution Patterns ◽  
Human Populations ◽  
Regional Diversity ◽  
Subtype B ◽  
Immunodeficiency Virus ◽  
Australasian Region ◽  
Hiv 1

Worldwide, the human immunodeficiency virus exhibits a great genetic variability, with multiple circulating subtypes of the virus. This variability allows study of the movement of HIV strains within and between human populations but also has implications for diagnosis, treatment and monitoring. The type of HIV causing the epidemic in Australia is changing from being homogeneous subtype B, reflecting a greater regional diversity. In this paper the classification of HIV-1 subtypes and their distribution within the Australasian region are reviewed and the implications of these distribution patterns discussed.

Rehydration methods to recover cysticercoids of the rat tapeworm Hymenolepis diminuta from dry flour beetle carcasses

2016 ◽  
Vol 91 (4) ◽  
pp. 470-478 ◽  
Author(s):  
H.M.-H. Chin ◽  
L.T. Luong ◽  
A.W. Shostak
Keyword(s):  
Developmental Stages ◽  
Hymenolepis Diminuta ◽  
Helminth Parasites ◽  
Post Mortem ◽  
Intensity Of Infection ◽  
Internal Organs ◽  
Flour Beetle ◽  
Terrestrial Arthropods ◽  
Early Developmental Stages ◽  
Early Developmental

AbstractTerrestrial arthropods host a variety of helminth parasites, yet quantifying the intensity of infection in these hosts post-mortem is challenging because carcasses may desiccate quickly. We recovered cysticercoids of Hymenolepis diminuta from desiccated flour beetle (Tribolium confusum) carcasses by modifying a published insect rehydration procedure. Without rehydration, carcasses dissected more than 1 day post-mortem had noticeable degradation of cysticercoids. Mild rehydration (soaking in water only for 2 days, or 0.5–10% KOH for 1 h followed by 1 day in water, or 0.5% KOH for 1 day) left carcasses tough and time-consuming to dissect, but all parasites could be recovered and were similar in body size to fresh cysticercoids. Moderate rehydration (5–10% KOH for 1 day) allowed all parasites to be recovered and facilitated dissection by partially dissolving internal organs of the beetle while causing little degradation of the cysticercoids. Harsh rehydration (5–10% KOH for 1 day followed by 5 days in water) not only dissolved internal beetle tissues but also severely damaged cysticercoids, such that parasite counts were unreliable. The degree of initial carcass desiccation had little effect on results following rehydration. However, regardless of treatment used, intact cercomers were rarely retained on rehydrated cysticercoids. Rehydration was less successful on early developmental stages of the parasite, which were recovered reliably only as they neared the cysticercoid stage. This method has utility for studies of parasite-induced mortality by permitting accurate and reliable parasite counts from dead, desiccated hosts.

Epidemiology ofAnguillicola crassusin the European eel (Anguilla anguilla) from two rivers in southern England

Parasitology ◽  
2005 ◽  
Vol 130 (6) ◽  
pp. 679-686 ◽  
Author(s):  
J. NORTON ◽  
D. ROLLINSON ◽  
J. W. LEWIS
Keyword(s):  
Anguilla Anguilla ◽  
Paratenic Host ◽  
Early Years ◽  
Substantial Contribution ◽  
European Eel ◽  
Intensity Of Infection ◽  
Gymnocephalus Cernuus ◽  
High Prevalence ◽  
Gravid Females ◽  
Low Prevalence

European eelsAnguilla anguillafrom the rivers Thames and Test, in the south of England, were examined between 2000 and 2003 for infection with the swim-bladder nematodeAnguillicola crassus. Since its introduction to Thames eels at tidal estuarine locations circa 1987,A. crassushas become established in non-tidal freshwater stretches upriver and data from these locations are reported for the first time. The prevalence of infection at Thames estuary locations was higher during 2000–2003 than for the period 1987–1992. By 2003, similar prevalences were observed at freshwater and estuarine locations, but infection intensities were significantly higher in freshwater. Eels from the river Test appear to have been recently colonized byA. crassus(circa 2000). Parasite population establishment within these eels was uncharacteristically slow during 2000–2001, with low prevalence and intensity of infection, and few gravid females during this period. By 2003, infection levels in Test eels were similar to those in Thames eels. The expansion of theA. crassuspopulation in Test eels has occurred in the absence of the paratenic host ruffeGymnocephalus cernuus, and at suboptimal pH for the survival and infectivity of free-living larvae. The epidemiology ofA. crassusin Test eels demonstrates that transmission ofA. crassusby ruffe is not required for high prevalence and intensity of infection in eels. However, the consistently low and atypical levels of infection in Test eels during 2000 and 2001 suggests that paratenic transmission by ruffe may provide a substantial contribution to the dynamics ofA. crassusin eels in the early years following introduction, by facilitating the rapid increase in prevalence and intensity ofA. crassusinfection that typically occurs during this time.

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