8_Basic Concepts and Principles

inner and outer compartments of other organisms

have played important roles in the evolution of members of the microbial world

commensalism, syntrophy, symbiosis and mutualism

Cell–cell interactions where at least one partner benefits are observed in __

competition, parasitism, predation, and antagonism

Cell interactions where one of the partners is subjected to negative effects are evident in ___

Fleas and bacteria

caused black death in the 14th century

Roberts and Janovy Jr. 2005

Global prevalence of A. lumbricoides is at 26% in 2003-(___) – unchanged for the last 50 years

Pneumocystis, Toxoplasma, and Cryptosporidium

are among the most common opportunistic infections in patients with AIDA

Foodborne Ascaris infection and foodborne toxoplasmosis

most common foodborne parasitic diseases.

Human cysticercosis, foodborne trematodosis and foodborne toxoplasmosis

resulted in the highest burdens in terms of DALYs (Disability-Adjusted Life Year)

Foodborne enteric protozoa

reported elsewhere, resulted in an additional 67.2 million illnesses

Symbiosis

describe biological interactions such as mutualism, commensalisms, and parasitism.

Cyanobacteria

are known to have either an intracellular or extracellular association with diatoms

diatom

major contribution of the ____ is the fixation of carbon dioxide, which provides the symbiont with sugars, although the cyanobiont also fixes carbon dioxide.

mutualism

limited application - describe relationship where both organisms involved benefit, and it this case it could also be called

Ectosymbiosis

microorganism remains outside the other organism

Endosymbiosis

microorganism is found within the other organism

Ecto/endosymbiosis

microorganism lives both on the inside and the outside of the other organism

intermittent and cyclic or permanent

Physical associations can be

Parasitism

• relationship where participant, the parasite, either harms its host or in some sense lives at the expense of the host.

• Consequences:

  • mechanical injury, such as boring a hole into the host or digging into its skin or other tissues,

  • stimulate a damaging inflammatory or immune response, or

  • simply rob the host of nutrition. • or a combination

Ectoparasites

Types of parasites:

• surface of host

Endoparasites

Types of parasites:

• inside host

Obligate parasite

Types of parasites:

• at least one life stage is parasitic

Facultative parasite

Types of parasites:

• not normally parasitic but can be when accidentally in the situation. i.e. N. fowleri

Accidental or incidental parasite

Types of parasites:

• enters the wrong host

• May not survive or become extremely pathogenic

Permanent

Types of parasites:

• live their entire adult lives in a host

Temporary/intermittent

Types of parasites:

• only feeds in the host then leave, i.e. micropredators like mosquitoes

Parasitism

• at the expense of host without killing

• Small and weak

• only one host

• symbiotic

Predation

• At the expense of prey by killing

• Larger and stronger

• Several prey

• Not symbiotic

Parasitoids

Variation of parasitism:

• insects’ immature stages feed on host and finally kill their host

• may resemble predators

Protelean

Variation of parasitism:

• insects whose immature stages are parasitic

Definitive

where parasites reach sexual maturity

Intermediate

required for parasite development but not until sexual stage

Paratenic

• transport host; no parasite development but remains alive and infective to another host

• insects shrews owls

• Bridges ecological gap between intermediate and definitive.

Reservoir

animal that harbors infection transmissible to humans

Host specificity

restricted range of host

Hyperparasitism

when parasites becomes hosts to other parasites.

Medical Parasitology

deals with the parasites, which cause human infections and the diseases they produce

• Plasmodium spp.

• Babesia spp.

• Toxoplasma gondii

• Echinococcus granulosus

• Echinococcus multilocularis

• Taenia solium

• Spirometra spp.

Parasites with man as intermediate or secondary host

Direct life cycle

• Parasites require only single host to complete development.

• Ex. Entamoeba histolytica

Indirect life cycle

• requires an intermediate host (2 or more hosts) to develop into adults

• Ex. Human and mosquitos in Malarial parasites.

Protozoa

• Entamoeba histolytica

• Giardia lamblia

• Trichomonas vaginalis

• Balantidium coli

• Cryptosporidium parvum

• Cyclospora cayetanensis

• Isospora belli

• Microsporidia

Helminths

• Ascaris lumbricoides

• Enterobius vermicularis

• Trichuris trichiura

• Ancyclostoma duodenale

• Necator americanus

• Hymenolepis nana

Parasites having direct life cycle

C.F.I.O.S.A

(Contaminated soil and water, Food, Insect Vectors, Other persons, Self (autoinfection), Animals)

Sources of Parasites:

O.S.V. D.V.I.C

(oral, skin, vector, direct, vertical, iotrogenic, congenital

Modes of transmission

1. Lytic necrosis

2. Trauma

3. Allergic manifestations

4. Physical obstruction

Pathogenic Mechanisms

Lytic necrosis

Pathogenic Mechanisms:

• Enzymes produced by some parasite can cause___

• E. histolytica lyses intestinal cells and produces amoebic ulcers

Trauma

Pathogenic Mechanisms:

• Attachment of hookworms on jejunal mucosa leads to traumatic damage of villi and bleeding at the site of attachment.

Allergic manifestations

Pathogenic Mechanisms:

• Clinical illness may be caused by host immune response to parasitic infection

• e.g. eosinophilic pneumonia in Ascaris infection and anaphylactic shock in rupture of hydatid cyst

Physical obstruction

Pathogenic Mechanisms:

• Masses of roundworm cause intestinal obstruction.\

• Plasmodium falciparum malaria may produce blockage of brain capillaries in cerebral malaria

Morphologic adaptations

Adaptations to Parasitism:

• organs not necessary for parasitic existence are lost

• ➢ Plasmodium – no locomotory organelles

• ➢ Cestodes – no digestive system

• ➢ Trematodes – reduced digestive tract

• ➢ to compensate the lost, they have highly developed reproductive system; addition of hooks and suckers.

M.PBC.S.IE.IRC

(Morphological, Profound biochemical changes, Specialized mechanism for effecting entrance into the body of host, Immune evasion, Increased reproductive capacity)

Adaptations to Parasitism:

Cestodes

no digestive system

Plasmodium

no locomotory organelles

Trematodes

reduced digestive tract

Profound biochemical changes

Adaptations to Parasitism:

• loss of certain metabolic pathways common to free-living

Specialized mechanism for effecting entrance into the body of host

Adaptations to Parasitism:

• E. histolytica – proteolytic enzyme to penetrate intestinal mucosa

• H. nana – with hooklets

• Cercaria Stage – with penetration glands

Immune evasion

Adaptations to Parasitism:

• depends on how successfully the host’s immunity is overcame.

• Evading mechanisms

• Intracellular habitats, encystment, antigen variation

Increased reproductive capacity

Adaptations to Parasitism:

• single egg in intermediate host develops into a larva, which in turn produces more larva

• Ex. Miracidium –redia –large number of cercaria

M.B.P.R.LC.AST

(morphological, behavioral, physiological, reproductive, life cycle adaptation, adaptation to starvation time)

Tick and parasitic adaptions

Microscopy • Culture • Serological test • Skin test • Molecular method • Animal inoculation • Xenodiagnosis • Imaging • Hematology

Types of Laboratory Diagnosis

Stool • Blood • Urine • Sputum •Cerebrospinal fluid (CSF) • Tissue and aspirates •Genital specimens

Specimens for Diagnosis

Stool Examination

Detection of intestinal infections like Giardia, Entamoeba, Ascaris, Ancylostoma, etc.

Protozoa: Plasmodium spp., Babesia spp., Tryponosoma spp., Leishmania spp.

Nematodes: Wuchereria bancrofti, Brugia malayi, Loa loa, Mansonella spp.

Parasites found in Peripheral blood film

• Schistosoma haemtobium, Wuchereria bancrofti, Trichomonas vaginalis

• lateral spined eggs of S. haemtobium and trophozoites of T. vaginalis

Parasites found in urine

eggs of P. westermani

Sputum Examination can detect

• Trophozoites of T. vaginalis are found in the vaginal and uretheraldischarge.

• Eggs of E. vermicularis are found in anal swabs

Genital Specimen Examination can detect

protozoa like T. brucei, Naegleria, Acanthamoeba, Balamuthia, and Angiostrongylus

Cerebrospinal Fluid Examination can detect

axenic and polyxenic

Some parasites like Leishmania, Entamoeba, and Trypanosoma can be cultured in the laboratory in various ___media

Antibody Detection

• Complement fixation test (CFT)

• Indirect hemagglutination (IHA)

• Indirect immunofluorescent antibody test (IFA)

• Rapid immunochromatography test

• ELISA test.

Molecular method

most frequently used to diagnose human parasitic infection: DNA probes, PCR), and microarray technique.

Animal Inoculation

It is useful for the detection of Toxoplasma, Trypanosoma, and Babesia from the blood and other specimens.

Xenodiagnosis

Some parasitic infection like Chagas’ disease caused by T. cruzi can be diagnosed by feeding the larvae of reduviid bugs with patients blood and then detection of amastigotes of T. cruzi in their feces.

Imaging

Xray, ultrasonography (USG), computed tomography (CT) scan and magnetic resonance Imaging (MRI) for neurocysticercosis and hydatid cyst disease.