Quantification of the crowding effect during infections with the seven Eimeria species of the domesticated fowl: its importance for experimental designs and the production of oocyst stocks

Williams, R. B.

doi:10.1016/s0020-7519(01)00235-1

Cited by 126 publications

(107 citation statements)

References 45 publications

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“…The most remarkable result is the striking similarity between the model-derived graph in figure 3a and the results as published by Williams (2001), but also shown by others (Brackett and Bliznick 1952;Johnston et al 2001), who observed a crowding effect with increasing oocyst dose (figure 2). Two possible mechanisms have been suggested to cause the crowding effect: reduction in the availability of epithelial cells and acquired immunity (Williams 1998;Johnston et al 2001).…”

Section: (A) Biological Implicationssupporting

confidence: 84%

“…If the immune effector function f were a negative exponential instead of a hyperbolic function, the graph would decrease much faster, which is not supported by experimental data (Brackett & Bliznick 1952;Johnston et al 2001;Williams 2001).…”

Section: Model Analysismentioning

confidence: 81%

“…The increase in excretion with very high dose is caused by the saturation of the immune response with high schizont numbers. If the third linear part is a realistic phenomenon, the doses administered by Williams (2001) may have been too small to reveal it, or the required doses too high to keep the chickens alive. In this case, z is very small compared with b, so the number of schizonts will hardly saturate the increase of y.…”

Section: K6mentioning

confidence: 99%

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A simple model for the within-host dynamics of a protozoan parasite

Klinkenberg

Heesterbeek

2005

Proc. R. Soc. B.

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The dynamics of parasite-host systems can be complicated if the parasite life cycle contains an obligatory environmental stage and if the hosts' immunity increases upon re-infection. The dynamics then greatly depend on the relation between infection history and parasite uptake and excretion of individual hosts. In an effort to better understand such systems, we study Eimeria spp. in chickens as our model. In this paper we take a first step and study the within-host dynamics of Eimeria spp., transmitted through oocysts in the environment, with a mathematical model for the parasite life cycle in discrete time, interacting with a single variable describing the immune response. The model can explain various types of oocyst input-output behaviour as described in previous experiments, in particular the characteristic crowding effect, which causes a decreasing oocyst production with increasing single dose oocyst uptake. Oocyst excretion during constant oocyst uptake (trickle infection) and the immunizing effect of single and trickle infections also appears in accordance with published experiments. The model seems a good description of oocyst input-output behaviour in individual hosts; it provides a solid basis for the study of between-host dynamics, where individuals interact in a common environment, thereby affecting their own and each other's infection pattern.

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Section: (A) Biological Implicationssupporting

confidence: 84%

Section: Model Analysismentioning

confidence: 81%

Section: K6mentioning

confidence: 99%

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A simple model for the within-host dynamics of a protozoan parasite

Klinkenberg

Heesterbeek

2005

Proc. R. Soc. B.

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“…Higher prevalence in exotic breeds was also reported by Gari and colleagues (2008) who stated that the frequency of occurrence of coccidial infection in Rhode Island Red (RIR) breed was significantly higher than the local breed and this could be due to management system and breed factor (Williams, 2001).…”

Section: Discussionsupporting

confidence: 56%

Poultry coccidiosis: Prevalence and associated risk factors in extensive and intensive farming systems in Jimma Town, Jimma, Ethiopia

Chalchisa¹,

Begna²

2016

J. Vet. Med. Anim. Health

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Despite the presence of large number of chicken in Ethiopia, contribution to national economy or benefit from this sector of activity is very limited due to diseases and management, out of which poultry coccidiosis is a leading problem. A cross sectional study was undertaken in Jimma town and College of Agriculture and Veterinary Medicine's (JUCAVM) poultry farm from November 2014 to April 2015 with the objective of determining the prevalence of poultry coccidiosis and associated risk factors. The fecal samples collected from live poultry and some after postmortem were subjected to flotation technique to increase sensitivity of the coprological examination of coccidian oocysts using light microscopy (10x). Postmortem examination was also performed to observe the pathological lesion and harvest coccidian oocysts. Out of the total 384 chicken examined, 152 (39.6%; 95% CI 34.7, 44.5) were positive for coccidian oocysts. Statistically significant difference (P=0.003) in the prevalence of coccidiosis was observed between young and adult as well as between exotic and local breeds of chickens. Higher infection proportion was detected in birds under intensive management system as compared to birds in back yard. The difference was statistically significant (P=0.000). The prevalence was also statistically significantly different (P=0.000) between exotic and local breed chickens. Higher prevalence was observed in chickens that were clinically diseased than subclinically harboring the oocysts which was statistically significant (P=0.03). However, no statistical significant association was observed between the prevalence and risk factors like sexes, feeding and watering sources. This study demonstrated that coccidiosis is an important problem of poultry for owners in Jimma town and JUCAVM poultry farm. Therefore, appropriate preventive strategies have to be designed to reduce the burden of this disease.

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“…Cross resistance between polyether ionophores is well documented (Weppelman et al, 1977;Voeten, 1989). Nonetheless, caution must be exercised when using oocyst counts as a means of evaluating anticoccidial efficacy (Reid, 1975) as factors such as initial infection level, Eimeria species involved, reproduction potential, crowding effect and acquired immunity influence the oocyst output (Brackett & Bliznick, 1952;Williams, 1973;Henken et al, 1994;Graat et al, 1996;Williams, 2001). …”

Section: Discussionmentioning

confidence: 99%

Coccidial infections in commercial broilers: epidemiological aspects and comparison ofEimeriaspecies identification by morphometric and polymerase chain reaction techniques

et al. 2008

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The objective of this study was to add to existing knowledge of the epidemiology and the aetiology of coccidial infections in commercial broiler flocks. Polymerase chain reaction (PCR) and morphometric identification of the Eimeria species were compared as means of differentiation in the field samples of faeces and litter. For morphometry, the Eimeria species were categorized into three groups based on lengths of the oocysts. Two random samples of commercial broilers were studied, one during 2000/01 and the other during 2003/04. The prophylactic regime (in-feed narasin), husbandry and methods applied were broadly the same for both subpopulations. Coccidial infection prevalence increased from approximately 45% to approximately 75% during this period, but infection levels (oocysts per gram of faeces) did not significantly change. There were substantial geographical differences in both prevalence and infection levels. A change in Eimeria species profile occurred during the study period. Five Eimeria species were identified at slaughter, by PCR targeting the ITS-1 region of the genome; Eimeria acervulina (100%), Eimeria tenella (77%), Eimeria maxima (25%), Eimeria praecox (10%) and Eimeria necatrix (2%). PCR and morphometric tentative identification were in complete agreement in only 49% of the cases.

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Quantification of the crowding effect during infections with the seven Eimeria species of the domesticated fowl: its importance for experimental designs and the production of oocyst stocks

Cited by 126 publications

References 45 publications

A simple model for the within-host dynamics of a protozoan parasite

A simple model for the within-host dynamics of a protozoan parasite

Poultry coccidiosis: Prevalence and associated risk factors in extensive and intensive farming systems in Jimma Town, Jimma, Ethiopia

Coccidial infections in commercial broilers: epidemiological aspects and comparison ofEimeriaspecies identification by morphometric and polymerase chain reaction techniques

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