Human Parasitology Exam 1: Lecture 1 - Intro to Parasitology

Symbiosis

Close Association of Organisms of Different species

Eugene Odum

American Ecologist in 1959, Identified interactions based off population growth

Commensalism

(+/0) One symbiont benefits, the other is unaffected

Ex: Cattle egrets and cattle

Phoresis

(+/0) Symbionts travel together

No physiological dependency

Phoront is smaller, carried

Ex. Algae on a turtle

Mutualism

(+/+) Both partners benefit

Obligatory - physiological dependence

Ex: Termites and intestinal protists

Exploitation

(+/-)

Several Forms:

Parasitoid

Only one host attacked and killed

Ex. Wasps deposit eggs on insects, larva hatches and consumes host

Micropredator

More than one organism attacked, but rarely killed

Mosquitos for example

Parasite

Only one host attacked, seldom killed

Parasite benefits and host is harmed

Parasite

Lives in or on host

Part or all nutrients from the host

Smaller than the host

Greater reproductive potential than the host

Potential of harming the host

What organisms are parasites?

Helminths (worms)

- Cestodes & trematodes (flatworms)

- Nematodes (roundworms)

Protozoa

Arthropods

Ectoparasite

lives on host surface

Endoparasite

lives within host

Obligate Dependency

must be parasitic for at least part of life cycle

Facultative Dependency

not normally a parasite but Can survive being eaten

Definitive Host (DH)

Parasite reaches sexual maturity in the host

In species with no sexual reproduction, DH is host most important to humans

Intermediate Host (IH)

Parasite does not reach sexual maturity in the host

Still required for parasite development

Negative binomial

A few hosts have many parasites

- Heavily infected hosts killed

Most hosts have few parasites

- Most hosts not killed

- Why? Parasite will die when hosts do

Direct Transmission

Parasite transmission from one DH to another through air, fomite, or in food/water

Indirect Transmission

Parasite develops in IH

Disability-adjusted life years (DALY)

Measures time:

- # of healthy years lost

DALY = YLL + YLD

- YLL = Average # of Years of Life Lost

- YLD = Years Lived with Disability

Based on expectancy of 92 years

CC Symbiotic Relationships

(+/+) = Mutualism

(+/0) = Commensalism and Phoresis

(+/-) = Predation, Micropredator, Parasitoid, Parasites

CC Parasites, Nonparasites, Hosts

Parasites are animals that create +/- Relationship with host and have infections chronic and difficult to control

1.) Lives in or on host

2.) Part or all nutrients from the host

3.) Smaller than the host

4.) Greater reproductive potential than the host

5.) Potential of harming the host

Nonparasites are Bacteria and Viruses

Hosts can be definitive (have adult, sexually mature parasites) or Intermediate (have growing, nonsexually mature hosts)

CC Direct and Indirect Lifecycles

Direct = Parasite transmission from one DH to another through air, fomite, or in food/water

Indirect = Parasite develops in IH

CC Leading Causes of Death

In USA = Mostly non-communicable. Not parasites

In poor countries = Bacteria and viruses, Diarrheal diseases, Childhood death, Parasites. >90% of all deaths caused by few diseases

Big 3 are

1.) HIV/AIDs - treated with Antiretroviral medication

2.) Tuberculosis - treated with Antibiotic and vaccine development

3.) Malaria - Drugs for treatment, Bed nets for prevention

CC the 4 Categories of Tropical Pathogens

1.) Helminths (Worms)

- Foodborne trematodiases - 56 million at risk

- Schistosomiasis - 700 million at risk

- Soil-transmitted helminths (STH) - Billions at risk

- Lymphatic filariasis - 1.3 billion

- Onchocerciasis (River blindness) - 90 million

2.) Protozoa

- Human African trypanosomiasis (Sleeping sickness) - 60 million at risk

- Chagas disease - 25 million at risk

- Leishmaniases - 350 million at risk

3.) Bacteria

- Buruli ulcer

- Leprosy (Hansen disease)

- Trachoma

- Yaws

4.) Viruses

- Dengue/Severe dengue

- Rabies

Describe parasitic disease in the US

Travel and migration

- Has everything to do with hosts

Poverty

- High disease and mortality rates

- Chronic disease (heart disease, cancer)

- Neglected infections of poverty include Parasitic, bacterial, and viral

- Some people have been left behind in America

US Congress

- Neglected infections of impoverished Americans Act (2015)