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
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)
SITE(S) OF INFECTION/INFESTATION
“Normal and aberrant migration of larvae”
“Oestrus ovis (the sheep botfly)”
Parasite - host balance
- Physical presence, activity or production of toxic products
- Size, numbers and behavior of the parasites
- How and how much the parasite feeds
- -iasis = ? of parasite (sub-clinical - not actually causing a problem)
- -osis = ? caused by parasite
Example: Coccidiasis vs Coccidiosis
Parasite - host balance
- Physical presence, activity or production of toxic products
- Size, numbers and behavior of the parasites
- How and how much the parasite feeds
- -iasis = presence of parasite (sub-clinical - not actually causing a problem)
- -osis = disease caused by parasite
Example: Coccidiasis vs Coccidiosis
CLASS MONOGENEA: ectoparasitic flatworms
?: viviparous monogeneans and some species are extremely pathogenic
Udonella spp. have lost their attachment ? during evolution
CLASS “MONOGENEA”: ectoparasitic flatworms
Gyrodactylus: viviparous “monogeneans” and some species are extremely pathogenic
Udonella spp. have lost their attachment hooks during evolution
