Lecture 1

Parasitology

Study of symbiosis

Germen scholar A. de Bary, 1879 definition of Parasitology

Any two organisms living in close association, commonly one living in or on the body of the other, are symbiotic, as contrasted with free living. usually the symbionts are of different species but not necessarily

Animal association

1. Homogenetic

2. Heterogenetic

Homogenetic association

Between individuals of the same genotype

Heterogenetic association

between individuals of different genotype

Interactions of Symbionts

1. No physiological or biochemical dependence

2. Physiological or biochemical dependence

Types of No physiological or biochemical dependence

Phoresis and Commensalism

Phoresis

“Traveling together” no physiological or biochemical dependence on either side

Commensalism

“Eating on the same table” One benefits from the other while the host is not harmed nor helped

Types of Physiological or biochemical dependence

Mutualism and Parastism

Mutualism

both partners benefit from the association ( Usually obligatory)

Parasitism

the parasite harms its host

Metabolic Dependence

1. Developmental Stimuli

2. Nutritional Materials

3. Digestive Enzymes

4. Control of Maturation

Typical characteristics of parasitism

1. higher reproductive potential

2. unique morphological or physiological specialization

3. special site specificity

4. usually non-lethal

5. generally more numerous and much smaller than the host

6. have evolved methods of evading the immune system

7. change host behavior

Types of parasites (A)

Ectoparasite and Endoparasite

Types of parasites (B)

Facultative and Obligate

Facultative Parasites

not normally parasites but can become so when they are accidentally eaten or enter a wound

Example of Facultative Parasites

freeliving amebas

Obligate Parasites

cannot complete their life cycle without spending at least part of the time as a parasite

Types of Obligate Parasites

1. Temporary or intermittent

2. Permanent

3. Incidental

4. Erratic

Temporary or intermittent parasite

Only Reeds on the host and then leaves

Example of temporary parasite

Mosquito / bed bugs

Permanent parasite

Live their entire adult lives within or on their host

Example of permanent parasite

Ascaris / hard ticks

Incidental parasite

Enters or attaches to the body of a species of host different from its normal one.

Example of incidental parasite

Dipylidium caninum

Erratic parasite

Wanders in to an organ in which it is not usually found

Example of erratic parasite

Entamoeba histolytica in the liver or lung

How to differentiate among various types of hosts

According to the role the host plays in the life cycle of the parasite

Types of hosts

1. Definitive host

2. Intermediate host

3. Paretenic or transport host

4. Reservoir host

Definitive host

The parasite reaches sexual maturity

Intermediate host

Require for parasite development but on in which the parasite doesn’t reach sexual maturity

Paratenic / Transport host

Parasite does not undergo any development but in which it remains alive and infective to another host

Reservoir host

Animal that harbors an infection but shows no il effects and serves as a source of parasite

Image of definitive host

Image of Intermediate host

Life cycle of parasites

1. Single or direct life cycle

2. Complex or indirect life cycle

Single or direct life cycle

Complex or indirect life cycle

Source of parasite names

1. The name of the individual who originally named the parasite

2. Named after their host

3. Named after the organ where they were discovered

4. The geographical location or the place they were discovered

5. Based on their morphology

Example of a parasite that was named after the person who originally named it

Giardia parasite

Example of a parasite that was named after their host

Emeria Bovis

What does the scientific name of a parasite consist of

Genus and species

Example of a parasite that was named after the organ was discovered in

Fasciola Hepatica

Example of a parasite that was named after the location it was found

Leishmania braziliansis

Example of a parasite that was named after thier morphology

Fasciola gigantica

Parasites are divided into major divisions, including

1. Protozoa

2. Platyhelminthes

3. Acanthocephala

4. Nematoda

5. Arthropoda

Example of Protozoa

Amoebae, Flagellates, Ciliates

Example of Platyhelminthes (flatworms)

Cestodes, trematodes

Another name for Acanthocephala

Thornyheaded worms

Another name for Nematoda

Roundworms

Example of Arthropoda

Insect, Spiders, Mites, Ticks

Methods of infection

1. Oral (eggs or larvae swallowed)

2. Vector (a blood feeding arthropod)

3. Penetration (specialized mouthpart that can pierce through skin)

Methods of escape

1. Sputum

2. Vector ( removes parasites while feeding)

3. Urine / Faeces

What the most common method of escape

Urine / Faeces

Direct effect of parasite on host

1. The parasites are undoubtedly the reason for its state

2. They can be discussed under the heading of trauma, nutrition robbing , toxin production, etc

Indirect effect of parasite on hosts

1. Exposing the host to concomitant infectious diseases

2. Impact on physical and mental development

3. Impact on production rates

Pathogen

As parasite which injures the host

Infection

The penetration of a parasite within the host

Infestation

The presence of arthropods on the skin of the host

Epidemic

The sudden appearance of an infection which spreads rapidly found in a large population

Endemic

An infection which has always existed in a region

Incubation

The time between the entrance of the parasite and the begin of the disease

Habitat

The natural abode of a parasite species

carrier

A person who carries a certain parasite without displaying any signs of disease

Zoonoses

The diseases of animal which are transmissible to man

Incidence

The rate part which a disease or a certain event occurs

Prevalence

The total number of cases of a disease at a certain time in a designated area