BMS 655 Exam 1

parasite

evolved to occupy a highly specific niche, organism that lives on or in a host organism to the detriment of the host

Infection

entry and development of an infectious agent in the body

Pathogen

an infectious agent capable of causing disease in a host

Disease

pathological condition with symptoms that set it apart from normal body state

Virulence

the ability of a parasite/infectious agent to reduce it’s host fitness

Fitness:

a measure of the success of an individual in passing on its genes to future gen and its influenced by indiv ability to survive and reproduce

Phoresy

hitching a ride, no trophic interaction: the “phoront” travels with its

Commensalism

eating food “wasted by host”, : one partner benefits no one is harmed

Mutualism

scratch my back I’ll scratch yours, both partners benefit from the assoc

Exploitation:

unidirectional benefit with a disadvantage for the other

Endoparasite:

parasite lives inside the host body

Ectoparasite:

parasite that lives outside or on the host body

Microparasite

microscopic, more difficult to count directly

Macroparasite

larger parasites, easy to count in a host

Obligatory parasite

requires its host to complete its life cycle

Facultative parasite:

free-living but can become parasitic, given the opportunity

Opportunistic parasite

takes advantage of a circumstance to infect a host that it normally doesn’t infect

Hyperparasite:

a parasite of a parasite

Castrator:

stops host reproductive activities (diverts resources to its own devel)

Body snatcher

parasite that takes over the host

Parasitoid.protelean parasite:

parasitic juvenile, free-living as an adult

Host

an animal or plant that noutsihes and supports a parasite it does not benefit and is often harmed by the assoc

Definitive host:

host in which parasite achieves sexual maturity

Intermediate host:

host in parasite undergoes a required dvelop step andmay reproduce asexually but not sexually

Heteroxenous life cycle:

more than one host

Direct/monoxenous life cycle

only a single host

Paratenic/transport

safe haven in which a parasite can persist and prolong survival increasing its likelihood of transmission to a new host

Reservoir host:

an animal that harbors an infection that can be transmitted to a human

Vector

a means by which a pathogen is transmitted

Mechanical vector

picks up a pathogen and carries it to a new host (no dev or replication of the pathogen occurs)

Biological vector:

multiplication or dev of the pathogen occurs before transmission to the new host

Cyclodevelopmental transmission

development of pathogen but no multiplication

Monoxenous direct life cycle

one host

Heteroxenous:indirect

two or more different hosts

Indirect life cycle: intermediate host

develop or proliferating (asexual replication), paratenic host: nonessential host that increases chance of transmission to the definitive host

Fecal-oral transmission

propagule: stage responsible for transmission, released in feces and contaminates water or food, usually needs to survive for long period of time in the environ, low level metabolism to conserve enrgy

Trophic transmission:

parasite takes advantage of a predator-prey relationship btw definitive and intermediate hosts, a host consumes an infected host

Direct penetration:

parasites are motile, can seek out their new host and burrow in, high energy cost, needs to find host within hours before energy reserves are depleted, periodicity: time emergence from previous host to coincide with best chances of encountering new host

Vector transmission:

arthopod blood feeders

Vector competence

ability of a vector type to become infected or transmit a specific pathogen

Vector capacity

other factors that influence the ability of a competent vector to transmit a pathogen, regular feeding on the host, feeding for extended period of time/taking large blood meal, long enough life span to allow for parasite development and replication, abundance, good dispersal ability

Vertical transmission

transmission from parent to baby, ex redwater fever in cattle (babesia bigemina)

Sexual transmission

transmission via sexual contact, trichomonas vaginalis protozoan parasite

Increasing transmission:

if survival or chance of reproducing is completely dependent on finding a specific host then, high fecundity (lot of progeny), high investment in repro when likelihood that any single progeny will survive is low

Protozoans:

have high replicative rates, asexual repro by binary fission with short doubling times

Factors that influence the optimal fecundity of a parasite

size of adult, life span , host range

Host range

how many hosts can the parasite infect, lots of opportunity or limited choices

Other factors that can influence transmission

co infection with other pathogens, host sex (infected adult females that can release oocyts)

Site specificity

some parasites have specific target tissues or cells that they need to infect to replicate or develop

Terra incognita:

migration within the host: diff challenges for ecto vs endo,, ecto attach strongly to particular site bc of morphological adaptations, endo need to navigate through host body to arrive at desired location

Molecular signposts

endoparasites, highly predictable system

Parasites want to settle in

ecto don’t want to fall off in bad weather or during grooming, endo challenge with blood flow and fluid flow

Allee effect

in small pop indiv fitness increases as pop density increases

Chemoattractant:

draw parasites together

Propagule

infectious stage responsible for transmission

Portal of exit:

often depends on the parasite site of infection

Excavata:

unicellular euk, modified mitochondrion, often possess a flagellum, kinetoplastids, (trypanosomes, leishmania), giardia, trichomonas

Protozoa:

unicellular euk, flagella, cilia, gliding, ampicomplexa, kintoplastids

Alveolates

predation, phototrophy and intracellular parasitism, ciliates, dinoflagellates, apicomplexa, flattened membrane vesicles (alveolae) packed in a contious layer underneath the plasma membrane, highly stable microtubules, rigid skin or pellicle

Apicomplexa:

all members are intracellular parasites, parasites of both vertebrates and invertebrates, complex life cycles, apical complex for attachment and invasion of host cells (rhoptries, micronemes), many members have a plastid like organelles called the apicoplast

Apical complex

polar rings, conoid, subpellicular microtubules, rhoptries, micronemes

Host cell invasion:

gliding and attatchment, penetrations and PV formation, PV anf host cell modifcation

The apicoplast:

plastid like organelle with unusual four membrane structure, similar to a chloroplast but nonphotosynthetic, a result of secondary endosymbiosis, separate genome encodes ribosomal components, important for lipid metabolism,  good for drug dev

Endosymbiosis

primary endosymbiosis: mitochondria, chloroplast, kinetoplast

Plasmodium

malaria parasite

Falciparum

in central Africa

Vivax:

more in south amer and asia

Life cycle malaria:

infected mosquito injects sporozoites when she feeds, sporo enter blood, penetrate liver cell, merozoites released form liver, asexual blood cycle, gametocytes circulate in blood

malaria in us

elimination efforts were successful

malaria stages

Sexual stages: mosquito: unaffected mosquito ingests gametocytes when she feed

Asexual stage in human:

Sometimes hypnozoite

in humans if vivax or ovale, dormant, can only be treated with primaguine

Exoerythcytic schizogony

live stages

Plasmodium intraerythrocyctic cycle

24-72 hr on species, parasites replicate by schizogony, produce hemozoin

Plasmodium blood stag:

ring: one nucleus

Trophozoite:

one nucleus, crystals of hemozoin begin to form

Schizont

multiple nuclei

Plasmoidum blood stage development

Responsible for all clinical symptoms, degradation of haemoglobin in the food vacuole, export of parasite proteins to the host plasma membrane- PfEMPS (antogenic variation), formation of maurer’s clefts and knobs

Sequestration

parasites export protein to the surface of the RBC to make them sticky: cytoadherence, resetting, phenomenon during P falciparum infection, parasitized RBCs block capillaries and prevent blood flow to critical tissues (brain) often leads to cerebral malaria and other organ damage

Complicated malaria

cerebral malaria, impaired consciousness, delirium, seizures, severe anaemia, metabolic acidosis, metabolic acidosis (manifests clinically as respiratory distress rapid deep and laboured breathing),hypoglycemia, parasitaemia > 10%

Cyclical fevers

malaria

Treatment of malaria

chloroquine, artemisnin-based combination therapy (ACT)

Anopheles:

vector for malaria

Plasmodium knowlesi a human zoonosis

simian malaria infecting macaques. Hard to distinguish from P. malariae by microscopy, very rapid 24 hr intraerythrocytic cycle, fifth human malaria or zoonic infection

Piroplasms: Apicocomplexa:

hematozoa

Babesiosis

intraerythrocytic parasites of the genus babesia infect a wide range of wild and domestic mammals and occasionally humans, transmitted by ticks and found worldwide, major problem in cattle industry, transmitted by ticks

Piroplasmosis

infection in horse caused by either Babesia caballi or theilria equi

Babesiosis:

the parasite typical nymph stage of the during warm months

Babesia microti life cycle

Indirect two hosts (ticks, white footed mouse)

Sporozoites: enter bloodstream during tick blood feeding invade eryrocytes and undergo asexual reproduction

Small proportion of parasites will stop dividing and differentiate into male and female gametocytes

Gametocytes are ingested by a tick during a blood meal, initiate sexual reproduction in tick gut and generating ookinete

Ookinete travels to tick salivary glands and undergoes sporogony to make sporozoites ready to infect

Babesia intraerythrocytic cycle

merozoites invade red blood cells, become tropzoites and replicate by binary fission, form four merozoites that egress and infect new red blood cells

Babesiosis:

Texas red water fever, usually acute, often aysm or very mild symptoms, but can be sereve

Diagnosis and treatment of plasmodium

microscopic exam of stained blood smears for parasites, treatment combination therapies

Theileria:

cows and horse, life cycle” tick stage and bovine host stage

Coccidians

dixenix coccidians (both hosts vertebraes): toxoplasma, neospora, sacrocytis, monoxenix coccidians (vertebrae): cyclospora, Eimeria, isospora

Neospora caninum

: closely resembles toxoplasma life cycle but canids are the definitive hosts, causes bovine abortion , canine infection is usually asym but can cause progressive hindlimb paralysis in puppies, disease, treatment: clindamycin

Eimeria species

infection of gastro tract that causes diarrhela disease, fecal oral, exxystation: through stomach and small intestine, many differ Eimeria species,e ach with a particular host preference

Cyclospora

coccidian closely related to Eimeria: genotyping suggests it’s actually three distinct species, common in tropical to imported fresh produce, watery diahea, cramping, weight loss, fatigue, infection resolves in immunocompetent people, but symptoms can perist for a few months if left untreated, relapse commonly occurs

Toxoplasma gondii

Cats are the primary host of toxoplasma

Parasite sexual reproduction takes place inside cat intestine

Ubiquitous parasite

Toxoplasma is the most successful protozoan in the world, infects one third of pop, south a

Infect any warm blooded animal

Obligate intracellular parasite, can infect any warm blooded animal, euk organells: nucleus, ER, golgi, mitochondrion, toxoplasma organelles: micronemes, rhoptries, dense granules, apicoplast

Micronemes

initial attachment and invasion

Rhoptries:

invasion and establishment of intracellular infection

Dense granules:

establishment and maintenance of intracellular infection