Biomaterial Database

Prevalence of infection, mean worm burden and degree of worm aggregation as determinants of prevalence of disease due to intestinal helminths. 1997

M V José, and A Ruiz, and J R Bobadilla

Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México, D.F. jose@servidor.unam.mx

Theoretical predictions of disease prevalence due to helminth infections based upon a simple probabilistic model which considers the infection prevalence, the mean worm burden and the degree of worm aggregation are presented. A numerical reappraisal of the likely estimates of the degree of aggregation based upon maximum likelihood estimates of the negative binomial distribution is presented. The prevalence of disease shows a positive relationship with the mean worm burden. This association is hyperbolic when helminth parasites are severely aggregated but is s-shaped when helminth parasites tend to be overdispersed. The prevalence of disease decreases with the degree of worm aggregation when the values of the mean intensity are low; as the mean intensity increases this association becomes positive. The relationship between prevalence of disease and prevalence of infection is hyperbolic for severe degrees of parasite aggregation and is s-shaped for intermediate degrees of aggregation. However, if the mean intensity is low and the degree of aggregation is high there could be a negative relationship between the prevalence of disease and the prevalence of infection. The presence of disease due to helminth parasites is feasible for determined ranges of values of the infection prevalence, mean intensity and the degree of worm clumping.

UI	MeSH Term	Description	Entries
D007411	Intestinal Diseases, Parasitic	Infections of the INTESTINES with PARASITES, commonly involving PARASITIC WORMS. Infections with roundworms (NEMATODE INFECTIONS) and tapeworms (CESTODE INFECTIONS) are also known as HELMINTHIASIS.	Parasitic Intestinal Diseases,Disease, Parasitic Intestinal,Diseases, Parasitic Intestinal,Intestinal Disease, Parasitic,Parasitic Intestinal Disease
D008800	Mexico	A country in NORTH AMERICA, bordering the Caribbean Sea and the Gulf of Mexico, between BELIZE and the UNITED STATES, and bordering the North Pacific Ocean, between Guatemala and the UNITED STATES.
D008962	Models, Theoretical	Theoretical representations that simulate the behavior or activity of systems, processes, or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.	Experimental Model,Experimental Models,Mathematical Model,Model, Experimental,Models (Theoretical),Models, Experimental,Models, Theoretic,Theoretical Study,Mathematical Models,Model (Theoretical),Model, Mathematical,Model, Theoretical,Models, Mathematical,Studies, Theoretical,Study, Theoretical,Theoretical Model,Theoretical Models,Theoretical Studies
D006373	Helminthiasis	Infestation with parasitic worms of the helminth class.	Nematomorpha Infections,Infections, Nematomorpha,Helminthiases,Infection, Nematomorpha,Nematomorpha Infection
D006376	Helminths	Commonly known as parasitic worms, this group includes the ACANTHOCEPHALA; NEMATODA; and PLATYHELMINTHS. Some authors consider certain species of LEECHES that can become temporarily parasitic as helminths.	Aschelminthes,Gordius,Nematomorpha,Parasitic Worms,Worms, Parasitic,Aschelminthe,Helminth,Nematomorphas,Parasitic Worm,Worm, Parasitic
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D015995	Prevalence	The total number of cases of a given disease in a specified population at a designated time. It is differentiated from INCIDENCE, which refers to the number of new cases in the population at a given time.	Period Prevalence,Point Prevalence,Period Prevalences,Point Prevalences,Prevalence, Period,Prevalence, Point,Prevalences
D016013	Likelihood Functions	Functions constructed from a statistical model and a set of observed data which give the probability of that data for various values of the unknown model parameters. Those parameter values that maximize the probability are the maximum likelihood estimates of the parameters.	Likelihood Ratio Test,Maximum Likelihood Estimates,Estimate, Maximum Likelihood,Estimates, Maximum Likelihood,Function, Likelihood,Functions, Likelihood,Likelihood Function,Maximum Likelihood Estimate,Test, Likelihood Ratio