HS Quiz 3

10/6 14-17

epidemic

sudden increase of disease in a location

legionnaire’s disease (bacteria)

a serious type of pneumonia caused by legionella bacteria

legionella bacteria normally

live in soil and water and rarely affect people from these sources unless they get into an aerosolized water source (cooling towers, AC units, humidifiers, etc)

toxic shock syndrome

staphylococcus aureus and 2 other bacterial species produce toxin that builds up and enters blood stream and causes multi-organ failure

TSS bacteria

can exist in harmony outside the body but easily enter through thin membranes and cause lots of harm once inside

severe acute respiratory syndrome (SARS)- virus

coronavirus

“germs” (bacteria and viruses) are considered parasites, which

benefit off of the harm of another and are rejected by our immune system

neutral interaction

neither species affects the other

competition interaction

both species are negatively affected

mutualism interaction

both species benefit

commensalism interaction

one species benefits, the other is unaffected

parasitism interaction

one species benefits, the other is harmed

microparasites

very small, common in nature, love humans as hosts

macroparasites

larger, can be seen with the naked eye

when exposed to a parasite

you can either develop an infection or no infection. infection can either be cleared quickly (no illness) or turn into illness. Illness results in recovery or death.

how do parasites and associated diseases get passed along in populations?

infectious agents → reservoirs → portals of entry → modes of transmission → portals of exit → susceptible host

reservoirs

where parasites are normally found (where they live, grow, and/or multiply)

three types of reservoirs

1. human (typhoid mary - infectious but asymptomatic)

2. animals (bats - rabies, ebola, etc)

3. abiotic sources (contaminated well water)

contaminated well water is

a common reservoir for viruses, bacteria, protozoa, and worms that cause human disease

parasites most often enter the body through

1. skin

2. mucous membranes

3. blood

modes of transmission (general)

1. abiotic environmental factors (wind - inhalation of spores, water - entry into skin)

2. animal vectors (mosquitos, fleas, etc)

modes of transmission (human to human)

1. direct contact

2. indirect contact (surfaces, air)

3. droplets

4. airborne

5. fecal-oral (contaminated food/water)

hosts

vary in their likelihood of getting infected, some are more resistant than others

more susceptible hosts

1. immunocompromised people (very young or old, organ transplant, chemo, HIV/AIDS)

2. already sick/injured (barriers compromised, underlying stress on body)

3. stressed (psychological, physiological, nutritional)

4. unexposed (naive to pathogens/parasites, unvaccinated)

herd immunity

resistance of an entire community to infectious disease due to the immunity of a large proportion of individuals in that community to the disease

immunized means people have protective immune responses due to

1. vaccination

2. prior exposure and recovery

malaria parasites

single-celled microorganisms that belong to the animal lineage called protozoa

genus: plasmodium

humans are infected by 5 malaria species

1. plasmodium falciprum

2. plasmodium vivax

3. plasmodium ovale

4. plasmodium malariae

5. plasmodium knowlesi

step 1 of malaria parasite infection

malaria parasites enter the body through anopheles mosquito bite

• sprozoites go directly into the host through the mosquite bite

step 2 of malaria parasite infection

parasites move to liver to develop and replicate (hepatocyte invasion)

step 3 of malaria parasite infection

parasites move to the blood stage where they infect and destroy RBCs

step 4 of malaria parasite infection

another mosquito ingests malaria gametocytes from an infected human and the cycle continues

the human liver

• largest gland/organ in the body

• at rest, about 1.5 liters of blood flow through the liver every minute

liver functions

1. synthesis (bile, proteins for blood plasma, proteins for clotting, some hormones)

2. detoxification (converts ammonia to urea, filters and clears blood of alcohol, medicines, harmful substances)

3. storage (stores and releases glucose as needed, stores iron and copper, stores some vitamins)

4. immune function (produces immune proteins and molecules, filters pathogens and toxins from blood)

5. waste handling and recycling (processes hemoglobin to re-use its iron, clears bilirubin waste, bile carries away waste)

6. transport (makes cholesterol and other special proteins to help carry fats through the body, regulates levels of amino acids in the blood)

red blood cells (erythrocytes)

small (7.5um) concave discs without a nucleus

# of RBCs in the body

20-30 trillion, which is roughly 89% of all cells

the body makes about

2 million RBCs per second, avg lifespan is 100-120 days

RBCs are broken down and

recycled in the liver and spleen by macrophages via phagocytosis

RBCs are

specialized cells that circulate through the body delivering O2 to cells and transporting CO2 back to the lungs for expiration

red coloring of blood comes from the

iron-containing protein hemoglobin

after water, RBCs are

97% hemoglobin (which each bind 4 O2 molecules)

small size and large surface area of RBCs allows for

rapid diffusion of oxygen and carbon dioxide across the plasma membrane

in the lungs (capillaries)

carbon dioxide is released and oxygen is taken in by the blood

in the tissues (capillaries)

oxygen is released from the blood and CO2 is bound for transport back to the lungs

pathology of malaria is due to

parasitic asexual reproduction in RBCs

why is this the pathology of malaria?

• parasite proteins and waste enter the blood when infected RBCs burst

• body responds with inflammation

• fewer RBCs to do work

• liver is overwhelmed

what happens if too many RBCs are destroyed?

plasmodium parasites can infect and destroy a significant number of circulating blood cells, leading to severe anemia

symptoms of malaria

headache, fever, fatigue, pain, chills/sweating, dry cough, spleen enlargement, nausea/vomiting

uncomplicated malaria

fever and/or chills, sweats, headaches, n/v, body aches, general malaise, enlarged liver or spleen, mild jaundice, increased resp. rate

severe malaria

impairment of consciousness, seizures, coma, severe anemia, hemoglobin in urine, acute resp. distress, abnormal blood coagulation, low BP, >5% RBCs infected, high blood acidity, low blood glucose levels, organ failure

how does malaria cause cyclical fevers?

fever coincides with RBCs bursting and parasites and waste being released, which happens in waves because of the similar timing of infection + bursting

diagnosis of malaria

• cyclic fevers are one indicator

• observing parasites or particles or antibodies in blood

• rapid diagnostic tests for specific proteins in blood drop/sample

incubation period

time between infection by parasite and onset of symptom

• no signs or symptoms at this time but # of microorganisms is increasing

prodromal period

vague, general symptoms

illness

most severe signs and symptoms

decline

declining signs and symptoms

convalescence

no signs or symptoms

incubation period for malaria

generally between 7 and 30 days depending on what species and strain of plasmodium

anti-malarial drugs can

prolong the incubation period, delaying the onset of symptoms

where does malaria occur?

in tropical and subtropical regions of the world (91 countries/territories)

• ½ of the world’s population lives in an area with malaria transmission

tropical and subtropical regions have

the right mix of climate and ecology

• temp, humidity, rainfall, insect and human population density

at temps below 68F

plasmodium falciprum cannot complete the growth cycle in mosquitos

incidence

number of new cases over a period of time

why is africa so intensely impacted by malaria

1. very efficient disease vector (anopheles gambiae)

2. highly virulent malaria species

3. local weather conditions ideal all year

4. relatively fewer resources for prevention and treatment

5. economic and political instability thwarts control efforts

africa has the largest burden of malaria, followed by

asia

how many cases and deaths result?

2022- 249 million cases and 600-700k deaths (WHO)

why did deaths increase in 2020-2021?

1. disruptions in preventative services

2. less access to health care

3. emergence of new strains resistant to treatment

who is most vulnerable for malarial infection?

those with little or no immunity

1. children

2. pregnant women

3. travelers/migrants from area with little transmission

in 2021,

57% of deaths due to malaria were in children under 5 yrs old

what are the social and economic costs of malaria?

direct (preventing, diagnosing, treating) - 12B+/yr

indirect-productivity loss

how can incidence of malaria be reduced?

1. insecticide treated nets

2. spraying houses with insecticide

3. intermittent prevention treatments for vulnerable populations

4. seasonal malarial chemoprevention treatments

5. rapid testing

history of malaria in the US

1914- first public funding to control malaria (window screens, larvicide)

1933- Tennessee Valley Authority develops land and waterways, reduces mosquitos

1947- National Malaria Eradication Program (NMEP), DDT spraying and wetland draining

1951 - malaria is no longer a public health concern

current cases of malaria in the US

roughly 2000 per year

current source of malaria in the US

• most cases are in people who traveled to places with ongoing transmission

• occasionally acquired through exposure to blood products, congenital transmission, lab exposure, or local mosquito-borne transmission