Parasites: General Concepts & Ectoparasites (Micro) Flashcards
Definitions
A facultative parasite is an organism that ? become parasitic, but does not require a ? for completion of its life cycle.
Examples of facultative parasitism occur among many species of * ? * (e.g. Blastomyces dermatitidis, Blastomycosis)
An opportunistic infection is an infection caused by ? (bacteria, viruses, fungi, or protozoa) that take advantage of an opportunity * not ? available*, such as a host with a * ? *, an altered microbiota (such as a disrupted gut flora), or breached integumentary barriers
PARASITISM: is when an organism (the parasite) for all or part of its life, derives at least some, but often ? of it’s food from a living organism of another species (the host), usually living ? or ? the body or cells of the host, which is usually ? to some extent by the association,
‘ONE WHO EATS AT ? TABLE’
A flea living on a dog: the flea feeds off the dog’s blood, which is detrimental to the dog. This is an examples of an * ? *
A caligid copepod living on the skin of fish, again an ectoparasite, but these parasites spend part of their life cycle as ?
A cestode platyhelminth living in the intestine of fish and mammals, an example on an ?
Definitions
A facultative parasite is an organism that may become parasitic, but does not require a host for completion of its life cycle.
Examples of facultative parasitism occur among many species of * FUNGI * (e.g. Blastomyces dermatitidis, Blastomycosis)
An opportunistic infection is an infection caused by pathogens (bacteria, viruses, fungi, or protozoa) that take advantage of an opportunity * not normally available*, such as a host with a * weakened immune system *, an altered microbiota (such as disrupted gut flora), or breached integumentary barriers
PARASITISM: is when an organism (the parasite) for all or part of its life, derives at least some, but often all of it’s food from a living organism of another species (the host), usually living in or on the body or cells of the host, which is usually harmed to some extent by the association,
‘ONE WHO EATS AT ANOTHER TABLE’
A flea living on a dog: the flea feeds off the dog’s blood, which is detrimental to the dog. This is an examples of an * ectoparasite *
A caligid copepod living on the skin of fish, again an ectoparasite, but these parasites spend part of their life cycle as free-living
A cestode platyhelminth living in the intestine of fish and mammals, an example on an endoparasite
EPIBIOSIS AND PHORESIS: ‘THE ACT OF BEING CARRIED’
In this case, the two organisms or symbionts are ? independent of each other and have a ? association (non- obligatory).
The larger, ?, carries the smaller ? around on its surface. The epibiont benefits from this ? by gaining access to differing environments.
Example: Stalked ? using copepod as transport to gain access to ? particles. Such ciliates may however inhabit other surfaces and are not restricted to the ?.
EPIBIOSIS AND PHORESIS: ‘THE ACT OF BEING CARRIED’
In this case, the two organisms or symbionts are nutritionally independent of each other and have a facultative association (non- obligatory).
The larger, basibiont, carries the smaller epibioint around on its surface. The epibiont benefits from this transportation by gaining access to differing environments.
Example: Stalked ciliates using copepod as transport to gain access to waterborne particles. Such ciliates may however inhabit other surfaces and are not restricted to the copepods.
COMMENSALISM
Latin com mensa meaning ‘sharing a table’
This occurs when the smaller symbiont, the commensal, feeds on the food available in or on the surface of the ?, for whom it is ? or unwanted, while the host neither benefits nor is harmed. There are both ?commensals and ?commensals.
Examples: ? feeding on bacteria on the surface of fish, and ? sp. also feeding on bacteria in the human intestine.
Latin com mensa meaning ‘sharing a table’
This occurs when the smaller symbiont, the commensal, feeds on the food available in or on the surface of the host, for whom it is unusable or unwanted, while the host neither benefits nor is harmed. There are both ectocommensals and endocommensals.
Examples: flagellates feeding on bacteria on the surface of fish, and Entamoeba sp. also feeding on bacteria in the human intestine.
Host-parasite balance
parasitism = Ht - x or X
NOTE: if taking a small amount then not a problem for host but if taking a lot of chunk of host then becomes a problem (big X) -> VIRULENCE OR PATHOGENICITY !!
commensalism = Ht - or + 0 (-x)
mutualism = Ht + Y
(symbiosis - long term)
Ht = host table complex (food available)
Host-parasite balance
parasitism = Ht - x or X
commensalism = Ht - or + 0 (-x)
mutualism = Ht + Y
(symbiosis - long term)
Ht = host table complex (food available)
PARASITES OF VET IMPORTANCE
Helminths: ? worms, large and ?
The term “helminth” includes a number of phyla, many of which are ? (phylogenetically) but they have ? similarities:
-they are vermiform or “?-like” in form-
Phylum ? (roundworms)
Phylum ? (flatworms)
– Class ? (tapeworms)
– Class ? (flukes: endoparasites)
– Class ? (skin flukes: ectoparasites)
– Class ? (free-living flatworms, some parasitic forms)
Phylum ? (thorny-headed worms)
Phylum ? (segmented worms) not parasitic (leeches)
PARASITES OF VET IMPORTANCE
Helminths: parasitic worms, large and multicellular
The term “helminth” includes a number of phyla, many of which are unrelated (phylogenetically) but they have superficial similarities:
-they are vermiform or “worm-like” in form-
Phylum Nematoda (roundworms)
Phylum platyhelminths (flatworms) - CTMT
– Class Cestoda (tapeworms)
– Class Trematoda (flukes: endoparasites)
– Class Monogenea (skin flukes: ectoparasites)
– Class Turbelleria (free-living flatworms, some parasitic forms)
Phylum Acanthocephala (thorny-headed worms)
Phylum Annelida (segmented worms) not parasitic (leeches)
Parasites of veterinary importance
- Kingdom ? (Protists)
– Phylum ? (flagellates)
– Phylum ?
– Phylum Ciliophora (ciliates) - Kingdom ?
- Kingdom Animalia
Trichodina
– Phylum ? (insects/arachnids, copepods)
– Phylum ? (Myxozoa)
Parasites of veterinary importance
- Kingdom Protozoa (Protists)
– Phylum Mastigophora (flagellates)
– Phylum Apicomplexa
– Phylum Ciliophora (ciliates) - Kingdom Fungi
- Kingdom Animalia
Trichodina
– Phylum Arthropoda (insects/arachnids, copepods)
– Phylum Cnidaria (Myxozoa)
- Parasitism: a non-? non-symbiotic relationship between species, where one species which is the ?, benefits at the expense of the other, the host
- How many species of parasite are there?? * And how many full stop!!!?
- Live in or on their host – Ectoparasite
– Endoparasite - ? than their host
- Parasites ? host biological fitness, to some extent (pathogenicity/virulence)
- Typically do not ? their host
- Reproduce at a ? rate than their host
- Parasites use the host for survival
– Food
– Water
– ?
– Habitat
– ?
- Parasitism: a non-mutual non-symbiotic relationship between species, where one species which is the parasite, benefits at the expense of the other, the host
- How many species of parasite are there?? * And how many full stop!!!?
- Live in or on their host – Ectoparasite
– Endoparasite - smaller than their host
- Parasites reduce host biological fitness, to some extent (pathogenicity/virulence)
- Typically do not kill their host
- Reproduce at a faster rate than their host
- Parasites use the host for survival
– Food
– Water
– heat
– Habitat
– transmission
Mode of infection
- Oral
– ? in the environment
– Oocyst/eggs in the environment
– Larvae in the ?
– Larvae in ?, ?
– ? in other host
– ? in milk - ? infection
- ?
- ? (vertical transmission)
via intermediate host: accidental ingestion of larvae in tissue of another host
fecal-oral route: accidental ingestion of eggs or larvae originating from feces of infected larvae
active skin penetration: larval stages invade through skin
injection by a blood-sucking insect
- larval stages develop to infectivity in insect intermediate host
Mode of infection
- Oral
– spore in the environment
– Oocyst/eggs in the environment
– Larvae in the environment
– Larvae in the intermediate host (IH), paratenic host (PH) - aka transport host
– cyst in another host
– larvae in milk - skin infection
- injection
- transplacental (vertical transmission)
[pic: via intermediate host: accidental ingestion of larvae in tissue of another host
fecal-oral route: accidental ingestion of eggs or larvae originating from feces of infected larvae
active skin penetration: larval stages invade through the skin
injection by a blood-sucking insect
- larval stages develop to infectivity in insect intermediate host (everything else is considered horizontal)]
Hosts and life cycles
Intermediate host (IH)
– * ? *, serves as ? but necessary host for
* ? development * of essential life stages
Paratenic host (PH) or transport hosts
– A * ? * transport host in which * ? development* of the parasite occurs
Aberrant or abnormal host
– Host not usually used by the parasite, development is ? or ?
Dead-end or incidental host
– A host that generally does not allow ? to the definitive host, thereby preventing the parasite from completing its ?
Hosts and life cycles
Intermediate host (IH)
– * REQUIRED *, serves as temporary but necessary host for * continued development * of essential life stages
Paratenic host (PH) or transport hosts
– A * non-required * transport host in which * no development* of the parasite occurs
Aberrant or abnormal host
– Host not usually used by the parasite, development is slow or incomplete
Dead-end or incidental host
– A host that generally does not allow transmission to the definitive host, thereby preventing the parasite from completing its development
HOST AND LIFE CYCLES
Host spectrum varies by ? and ? group
- Direct life cycle (a simple life cycle)
– Only one ? required to complete the life
cycle
– Stages in this host and the ?
– Host-specific or ? host spectrum (non- specific)
– Parasites without an intermediate host have
** ? life cycles **
– Definitive host (DH)–? reproduction takes place
HOST AND LIFE CYCLES
Host spectrum varies by parasitic and taxonomic group
- Direct life cycle (a simple life cycle)
– Only one host required to complete the life
cycle
– Stages in this host and the environment
– Host-specific or broad host spectrum (non- specific)
– Parasites without an intermediate host have
** direct life cycles **
– Definitive host (DH)–sexual reproduction takes place
adult worm in animal -> eggs passed in faeces -> eggs embryonate in 5 days + -> first stage larvae in feaces (L1) -> second stage larvae in faeces (L2) -> third stage larvae migrate onto grass in approx. 3 weeks -> ingested L3 develop through L4 and L5 to adult, egg-laying, worms
- Indirect life cycle (a complex life cycle)
– Two or more hosts are required to ? the life cycle
– Host-specific or broad host spectrum (non- specific)
– ? host: sexual reproduction (DH)
– ? host (IH)
– Involves ? in the hosts and the environment
- Indirect life cycle (a complex life cycle)
– Two or more hosts are required to complete the life cycle
– Host-specific or broad host spectrum (non- specific)
– final host: sexual reproduction (DH)
– intermediate host (IH)
– Involves stages in the hosts and the environment
Indirect life cycle: e.g. Dirofilaria immitis
larvae mature into adults in the heart
female adult worms release microfilariae
mosquito ingests microfilariae with blood meal
DEVELOPMENT takes place
microfilariae develop in mosquitoes to infective larvae
mosquito bites dog or cat and transmits infective larvae.
(thus sexual repro. occurs in the dog, DH - definitive host)
DIRECT LIFE CYCLE; Paratenic Host
Toxocara canis: as paratenic (or transport) hosts, a number of vertebrates and some invertebrates can become infected.
adult worms lay eggs in small intestine, eggs passed in feces, eggs embryonate, embryonated eggs in faeces (mouse host is not required - no development; embryonated eggs ingested by mouse) -> dog eats the mouse - gets the embryonated eggs in its system
Direct life cycle; aberrant host (human)
Toxocara canis; dead-end host - human brain - for worms.
INDIRECT life cycle with paratenic host
Nematode lungworms
- adult worms in lungs produce eggs. larvae hatch from eggs
- larvae move to the intestine via tracheal migration
- larvae are passed in faeces
- larvae are ingested by IHs (snails and slugs)
- transport host aka paratenic host ingests IH (e.g. given here -> bird: which is not a central host but takes part in this - however can get infected by eating the snail)
- tissues of transport/paratenic host or intermediate host ingested by cat
“no development - just transportation”
IH - some imp. development occurs
HOST, LIFE CYCLE AND MODE OF INFECTION
- Sexual
– Genetic ?
– ? life cycle
– Must have at least ? parasites (M & F) - Asexual
– Lack of genetic ?
– ? life cycle
– ? is enough!
HOST, LIFE CYCLE AND MODE OF INFECTION
- Sexual
– Genetic diversity
– longer life cycle
– Must have at least 2 parasites (M & F) - Asexual
– Lack of genetic diversity
– shorter life cycle
– ONE is enough!
Direct life cycle; sexual reproduction in DH
INDIRECT LIFE CYCLE; a/sexual reproduction in IH
(sexual reproduction inc at, oocysts sporulating and getting into proper IH and essential development in mouse left and can be chronic or acute; some of these behaviors can affect the behavior of the mouse so cats can easily eat a mouse)
Lecture objectives
- Key concepts with parasites
- Mode of infection
- Types of hosts
- Life cycle
- Parasite fitness/survival
– Food
– Life cycle strategies - Host-parasite balance
PARASITE FITNESS - SURVIVAL
Benefits from the host
* ?: ?, food and water, habitat
* ?: blood, mucosal lining, etc.
* Transmission or ?/ reproduction
* ? development / hypobiotic stage
– Hypobiosis is the term most often used for ? development that has a ? basis (nematodes). Can also be caused by host ? responses and an overcrowding effect, high numbers of adults inhibit ?
PARASITE FITNESS - SURVIVAL
** Benefits from the host **
* survival : heat, food and water, habitat
* food: blood, mucosal lining, etc.
* Transmission or maturation/ reproduction
* arrested development / hypobiotic stage
– Hypobiosis is the term most often used for arrested development that has a seasonal basis (nematodes). Can also be caused by host immune responses and an overcrowding effect, high numbers of adults inhibit larvae
Parasite fitness - survival
Habitat and food: where in the host?
- ? * site: preferred site in or on the host
- Food source, able to avoid immune system (for at least some time period)
- Feeding and location related to ?
- ? * site: site in or on a host that is not a normal location
Parasite fitness - survival
Habitat and food: where in the host?
- PREDILECTION * site: preferred site in or on the host
- Food source, able to avoid immune system (for at least some time period)
- Feeding and location related to pathology
- ABERRANT * site: site in or on a host that is not a normal location
causes more problems when in the wrong place (aberrant site)
SITE(S) OF INFECTION/INFESTATION
“Normal and aberrant migration of larvae”
“Oestrus ovis (the sheep botfly)”
Parasite fitness – life cycle strategies
A ? life cycle involving more than one host is a common feature of parasitic animals. This has many advantages but also creates some potential problems – how to get from one host to the other – * ‘ ? ’ *
Some parasites have life cycle stages that are motile and actively seek out hosts, others use ? (vectors) that deliver them, and many use hosts that are linked by a ? ? and are transmitted to the next host when their current one is eaten. This is known as * ? transmission *
Many * ? transmitted parasites * have tricks up their sleeves to enhance the chance that their hosts are eaten; but only once they have developed to a stage capable of infecting the next host.
For example, when infected, their intermediate/paratenic host may lose its ? ? behaviour and even behave in a way that ? predators.
Parasite fitness – life cycle strategies
A complex life cycle involving more than one host is a common feature of parasitic animals. This has many advantages but also creates some potential problems – how to get from one host to the other – * ‘ Transmission ’ *
Some parasites have life cycle stages that are motile and actively seek out hosts, others use hosts (vectors) that deliver them e.g. snail with weird antennas, and many use hosts that are linked by a ** food chain ** and are transmitted to the next host when their current one is eaten. This is known as * TROPHIC transmission *
Many * trophically transmitted parasites * have tricks up their sleeves to enhance the chance that their hosts are eaten; but only once they have developed to a stage capable of infecting the next host.
For example, when infected, their intermediate/paratenic host may lose its * predator avoidance behaviour* and even behave in a way that * attracts * predators.
Parasite fitness – life cycle strategies
- Infected fish behave in an ? or atypical manner
- Due to heavy ? but also ? behavioral traits
- Even showing ? behavior like swimming close to the water ?
Leucochloridium paradoxum – ‘Zombie Snails’
- A parasitic ? (trematode - all have complex life cycles)
- ? is the intermediate host
- The snail (?) consumes bird ? with eggs shed from adult flukes in the bird
- ? develop and migrate to the snail’s eye ?, forming a ? sac
- This attracts the ? bird host, that consumes the unsuspecting zombie snail
Parasite fitness – life cycle strategies
- Infected fish behave in an unsual or atypical manner
- Due to heavy infections but also altered behavioral traits
- Even showing risky behavior like swimming close to the water surface
Leucochloridium paradoxum – ‘Zombie Snails’
- A parasitic flatworm (trematode - all have complex life cycles)
- gastropod is the intermediate host
- The snail (gastropod) consumes bird droppings with eggs shed from adult flukes in the bird
- larvae develop and migrate to the snail’s eye tentacle, forming a pulsating sac
- This attracts the definitive bird host, that consumes the unsuspecting zombie snail
Parasite fitness – life cycle strategies
? gondii,
despite being capable of infecting almost any warm-blooded animal, it can only reproduce ? in cats
Infected rodents appear to lose their ? of cats, a phenomenon dubbed
“ ? Feline ?”
Parasite fitness – life cycle strategies
Toxoplasma gondii,
despite being capable of infecting almost any warm-blooded animal, it can only reproduce sexually in cats
Infected rodents appear to lose their fear of cats, a phenomenon dubbed
“ fatal Feline attraction”
Researchers estimate that as much as 30 percent of the people on earth are carrying T. gondii tachyzoites around in our brains.
Does this affect human behavior?
