Micro lecture exam #3

protozoa

• single celled, eukaryotic, have complicated life cycles and multiple hosts

• change form and physiology during life cycle

what is the parasite, vector, and reservoir for MALARIA?

• parasite: Plasmodium

• vector: female anopheles mosquito (host for sexual phase of life cycle)

• reservoir: humans (host for asexual phase of life cycle)

describe the sexual phase of malaria parasite life cycle in female anopheles mosquito.

• mosquito bites an infected human

• it collects gametocytes through the bite which then fuse to form a zygote

• the zygote divides through meiosis turning itself into oocytes

• in each oocyte, sporozoites are made through schizogeny (asexual reproduction)

• these sporozoites can then be found in the mosquitoes salivary glands, and are ready to infect a new human

describe the asexual phase in humans that ends with merozoites forming more gametocytes.

• infected mosquito bites human

• sporozoites are injected into humans which then travel down to the human’s liver

• in the liver, they mature into merozoites through schizogeny

• when merozoites are made, they are released into the blood and infect RED BLOOD CELLS

• merozoites divide by schiogeny in RBCs and are even released into plasma

• These mezoroites continue to infect RBCs and can even turn into gametocytes

• those gametocytes can be taken up by other mosquitoes

what is schizogeny? where does it occur and what does it form?

• schizogeny is asexual reproduction

• protozoan cells divide repeatedly in host cell

• forms merozoites in

• occurs in liver cells and RBCs

Plasmodium’s influence on mosquito feeding behavior (malaria)

• when they have sporozoites in their salivary glands, they feed more than normal

• when they just acquired a gametocyte form a human, they stop feeding to complete their sexual stage

plasmodium’s effect on human’s body odor (malaria)

• when they are recently infected (just bit), humans smell LESS attractive to a human — havent gone through their asexual phase

• when they have mature merozoites — they are already infected and humans smell more attractive to mosquitos (want to get their gametocyte)

statistics of malaria

• oldest evidence of malaria in dominican republic (mosquito in amber)

• paradoxism symptoms: high fevers, chills, shivering, sweating

• 300-500 million new cases per year

what does human malaria come from?

• form gorilla strain

toxoplasma life stage cycles

• cat becomes infected by eating an intermediate host like a bird or rat that contain bradyzoites(humans can be hosts too — just not eaten by cats)

• the parasite undergoes sexual reproduction in the small intestine

• through the sexual reproduction, immature, unsporalated oocytes are formed

• released in cat feces into environment (takes 1-5 days to sporolate and be infectious)

asexual reproduction of toxoplasma after ingested by rodent

• rodent ingests oocytes with sporozoites

• sporozoites phagotyze in rodent which form tachyzoites

• tachyzoites infect tissue cells — forming tissue cysts with bradyzoites

• bradyzoites reactivate and form more tissue cysts ORRR are ingested by a cat

difference between toxoplasma and malaria life cycles?

• the hosts are different for both: malaria is anopheles mosquito while toxoplasma are cats

• intermediate host for malaria is humans while toxoplasma can have multiple —humans, rodents, livestock, birds

• malaria need a vectors (mosquito) which toxoplasma does not — can be contracted by undercooked meat or cat feces

how do humans become infected with toxoplasma?

• eating undercooked meat or ingesting oocytes from cat feces, soil, produce

cryptosporidium — diarrhea disease

• reflects different levels of sanitation in water

• can be found in fecal contaminated water and food

why is cryptosporidium difficult to eliminate from water supply?

• their oocytes are too small to filter, are resistant to chlorine, and are difficult to stain

reservoirs for cryptosporidium

mammals, birds, reptiles, humans

platyhelminths

• flatworms

• acoelomate — lack a body cavity

nemahelminthes

• round worms

• possess a false body cavity

structure of beef tapeworm

• scolex — head w suckers for attachment

• proglottid segments — have their reproductive organs

beef tapeworm life cycle (taenia)

• adult version forms in human

• larvae and cyst forms in cow

human portion of beef tapeworm life cycle

• human eats undercooked meat with cysticercus (cyst)

• the larva in the cysticercus forms the scoled

• the scolex then attaches to the intestinal wall, forming the adult

• the adult version of virus forms the proglottid segments with eggs

• eggs released in feces

cow side of beef tapeworm

• consumes grass with fertilized eggs

• those eggs form larvae in cow intestine

• larvae move forward from intestine into body of cow

• once in body they form cysts in muscle of cow

how can humans contract dog tapeworm?

from pet kisses

How does the human role in Echinococcus differ from the beef tapeworm?

Humans are accidental intermediate hosts in Echinococcus, but definitive hosts in beef tapeworms.

What disease does Enterobius cause, and what is its main characteristic?

Causes round worm infection (most common); characterized by perianal itching, especially at night.

• mostly infects kids, easily spread

What disease does Ascaris cause, and what is its main characteristic?

Causes ascariasis; large intestinal roundworms that can migrate to lungs.

What disease does Necator cause, and what is its main characteristic?

Causes hookworm disease; larvae penetrate bare skin and feed on blood in intestines.

• free living larvae

What disease does Trichinella cause, and what is its main characteristic?

Causes trichinellosis; acquired from undercooked pork, larvae encyst in host muscle tissue.

• reservoirs: wild hogs, pigs, rodents, dogs, cats

What disease does Wuchereria cause, and what is its main characteristic?

Causes lymphatic filariasis (elephantiasis); transmitted by mosquitoes, blocks lymphatic vessels.

• human only host

What disease does Dirofilaria cause, and what is its main characteristic?

Causes heartworm disease; transmitted by mosquitoes, primarily targets canine hearts.

What disease does Anisakis cause, and what is its main characteristic?

Causes anisakiasis; acquired from raw seafood, larvae irritate stomach/intestinal walls.

• fish roundworm

life cycle and hosts for clonorchis — liver fluke

• Organism Type: Monoecious (hermaphroditic).

• Hosts Required:

  1. 1st Intermediate Host: Freshwater snail.

  2. 2nd Intermediate Host: Freshwater fish.

  3. Definitive Host: Humans (or fish-eating mammals).

• Transmission: Humans eat undercooked or raw freshwater fish containing encysted metacercariae. The larvae migrate up the bile ducts and mature into adults in the liver.

How do Schistosoma hosts and life cycle differ from Clonorchis?

Schistosoma has no second intermediate fish host (snail and human only); cercariae directly penetrate human skin.

anthropod vectors

blood sucking insects

ex: anophelesmosquitoes, deer tick, blackfly, etc

mechanical vectors

• pick up parasite, pathogen, egg, cyst in one place and drop it off at another

ex: flies and roaches

biological vectors

• all or part of life cycle of agent occurs in vectors

ex: mosquitoes, lice, and ticks

what is a reservoir?

organism maintaining pathogen in nature, often a bird or rodent

• can be stable or unstable (unstable could die — has disease)

transovarial transmission

• arthropods serve as both reservoir and vector

• all stages of vector life cycle infected

• bacteria passed from eggs into adults and back into eggs

• no other host needed

• ensures babies born infected

EX: rickettsia rickettsia

What is the life cycle of the agent causing epidemic typhus?

Rickettsia prowazekii is transmitted by human body lice through feces rubbed into bites.

What is the life cycle of the agent causing plague?

Yersinia pestis is maintained in wild rodents and transmitted to humans by fleas.

What is the life cycle of the agent causing Lyme disease?

Borrelia burgdorferi is transmitted by blacklegged deer ticks feeding on rodents and deer.

What is the life cycle of the agent causing Rocky Mountain spotted fever?

Rickettsia rickettsii is transmitted through tick bites and maintained via transovarial transmission.

What factors promote mosquito-vectored diseases, and how are they controlled?

Warm standing water and high humidity; controlled by removing water and using insecticides.

yellow fever

• Causes fever, chills, jaundice (yellow skin due to liver damage).

• or hemorrhagic symptoms.

dengue fever — mosquito

"Breakbone fever" (severe muscle/bone pain), can progress to hemorrhagic fever.

west nile virus

Mostly asymptomatic, but can cause severe encephalitis in the elderly.

reservoir is crows

zika

Can cause mild symptoms, but is highly teratogenic (causes microcephaly in unborn babies)

ebola

Not mosquito-vectored (spread by contact with bodily fluids); causes severe hemorrhagic fever

Infestations vs. Arthropod Diseases

An infestation is when arthropods live on or in the host's body tissues directly, rather than just transmitting an internal pathogen.

What are two examples of infestations?

Scabies (mites) and pediculosis (lice).

epidemiology

study of the cause of disease, development of disease, and transmission of disease

retrospective epidemiology

• looks backwards from outbreak to find cause of disease

• they do not know the bacterium that caused the disease

• look for factors that allow disease to occur

• remove those same factors that allow it to occur

prospective epidemiology

• look forward

• understand cause of disease and recognize factors/conditions that cause disease

• look for and remove factors that allow disease to occur

• they separate sewage water from drinking water

what are the stages of development and their characteristics?

• incubation: time between infection and symptoms

• prodromal: onset of mild illness symptoms (may or may not occur) — when you can sense you are getting sick

• illness: display classic symptoms of disease

• decline: get medications, immune system responds & symptoms decrease

• convalescence: recover and return to health

what are the four disease transmission patterns?

endemic, pandemic, epidemic, and sporadic

endemic

• always present at low but constant levels

• ex: chicken pox, lyme disease, or even cholera

epidemic

• widespread illness with higher level of infection than normal

• ex: ebola

sporadic

• occurs occasionally at low levels in diff locations

• ex: hookworms, chagas disease

pandemic

world wide occurrence

• ex: HIV, flu, HPV, chlamydia, COVID 19

what are the four factors that influence incubation time of a disease agent?

• type of pathogen/parasite, virulence characteristics

• infective dose — # of cells entering body

• infection site — lungs and skin

• health of immune system: incubation varies for diff disease

john snow

• determined fecal contaminated water to be source of cholera

• capped contaminated well and removed handle

• obtaining drinking water from other wells - end of cholera

semmelweis

• investigated maternal deaths in childbirth

• realized they were delivering babies with contaminated hands = higher death rates

• introduced hand washing with chlorine

florence nightingale

• introduced handwashing, disinfection, and aseptic techniques into nursing

• figured out lice was the vector for epidemic typhus

• cleanliness and removal of lice helped decrease typhus

3 forms of bacterial flora that grow on, in or around our body

• normal

• transient: normally not harmful, removable with hand washing, not adapted to body

• opportunistic

all may cause infection if get below epithelium

describe ways that different conditions/ treatments can allow the opportunistic flora to proliferate and damage the body

anytime your body becomes vulnerable (like the scenarios listed below) they allow opportunistic flora to damage body:

• weakened immune system due to illness

• treatment with broad spectrum antibiotics

• joint and catheter implantations

• burns/other injuries

• exposure to unsanitary conditions

NOTE: transient and normal can both become opportunistic

How can treatments allow opportunistic flora to damage the body?

Antibiotics kill competitive normal flora, allowing resistant opportunists to overgrow

How does normal flora change over time?

It shifts based on age, diet, hormones, and environmental exposures

How does normal flora benefit us?

By preventing pathogen colonization (microbial antagonism) and producing vitamins.

What is the structure and genetics of the influenza virus?

Enveloped virus with a segmented, single-stranded RNA genome and surface spikes (H and N).

• H and N are antigens on surface that allow virus to bind and enter host cell

How does influenza spread?

Through respiratory droplets and aerosols from coughing or sneezing.

What is the difference between antigenic drift and antigenic shift?

Drift is minor mutations; shift is major genetic reassortment creating new subtypes

What are the host characteristics and pandemic potential of Influenza Strain A?

• Influenza A infects humans as well as animals (birds, swine, horses)

• high pandemic potential due to antigenic shift.

What is the structure and genetic characteristics of HIV?

• HIV is a retrovirus containing two identical strands of single-stranded RNA

• reverse transcriptase

• enveloped virus

Which cells does HIV infect and why?

CD4+ T cells and macrophages, because gp120 binds to CD4 receptors

How does HIV affect the immune system?

It destroys CD4+ T helper cells, severely crippling cell-mediated immunity

Why do many HIV-positive patients eventually die from AIDS?

• HIV progresses to AIDS — AIDS destroys immune response

Severe immunodeficiency leads to fatal opportunistic infections or cancers.

Why are multiple drug treatments (cocktails) most effective against HIV?

They prevent drug resistance, target multiple replication stages, and lower viral load.

What are three examples of HIV inhibitors and their targets?

• fusion inhibitors: block receptors on virus (entry)

• Reverse transcriptase inhibitors (genome replication)

• integrase inhibitors: prevent HIV DNA from inserting into host DNA

What is the organelle of motion in Phylum Sarcodina?

Pseudopods (false feet).

What is a karyosome?

A dense chromatin mass within the nucleus of some protozoa

What are two prominent disease agents in Sarcodina?

Entamoeba histolytica (amebic dysentery) and Naegleria fowleri (primary amebic meningoencephalitis

What is the motility characteristic of Phylum Ciliophora?

Movement via short, hair-like cilia.

Which Ciliophora parasite causes human disease, and how is it transmitted?

Balantidium coli; transmitted via the fecal-oral route from swine.

• it is the only ciliated human intestinal pathogen

Why are Ciliophora and Sarcodina cysts and trophozoites easy to distinguish?

Trophozoites are motile and irregular; cysts are round, dormant, and thick-walled.