Introduction Flashcards
Why parasitology
Daily (or almost daily)
Major global animal and human health problems
Clinical disease
Subclinical disease/reduced production
Aesthetics/human animal bond
Animal welfare
Many zoonoses; public health
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Impacts of perasites against host animal
Compete for nutrition
Mechanical obstruction
Suck or consume body fluids
Feed on or destroy solid tissues
Pressure atrophy
Allergic reactions
Produce toxic substances
Carry pathogens including other parasites
Reduce hosts resistance to other disease and parasites
How do parasites compete for nutrents
By ingesting intestinal contents- ascarids (roundworms)
Ab absorbing them through body walls- tapeworm
Mechanical obstruction can affect the host where
Of the intestines- ascarids
Of bile ducts- ascarids, trematodes
Of blood vessels- canine heartworm
Of bronchi or trachea- lung worms
Of lymph channels- filarial nematodes
What parasites suck or consume body fluids
Blood- mosquitos, hookworm
Lymph- midges
Exudates- lungworms
How do parasites feed on or destroy solid tissues
Directly- giant kidney worms, liver flukes
After liquefying them- chiggers
What type of allergic reactions can parasites cause
Hypersensitivity, scar tissue
Pig livers
Black flies, mosquitoes, fleas
What toxic substances can parasites produce
Hemolysins, histolysins (break down tissue), anticoagulants
What can parasites carry
Mosquitoes- malaria, heartworm, WEE and WNV
Dog flukes- ‘salmon poisoning’
How does entry and/or migration hurt the host
Creeping eruption
Cutaneous larval migrans
Sarcoptic mange
What does the VT do for parasites
Diagnosis and prognosis
Control and prevention
Treatment
Public health
Client education
COMMUNICATION
A functional definition of parasitism
A parasite is a smaller organism that lives within or on another, generally larger, organism, the host
The parasite causes some degree of harm to the host. This “harm” ranges from mild to severe
The parasite absolutely requires the host to complete its life-cycle
Parasite types
Macroparasites
Helminths and arthropods
Microparasites
Protozoa, bacteria, fungi and viruses
Nematodes are
roundworms, hookworms, pinworms, whipworms, etc
Toxocara canis- dog roundworm
Helminths are
Worms
Types of flatworms
Cestodes- tapeworm
Diphyllobothrium spp.
Tapeworm of fish eating vertebrates
Trematodes- flukes
Fascioloides magna- giant liver fluke of ruminants
Types of Arthropods
Bugs
Flea
Flies
Lice
Mites
Ticks
Examples of protozoas
Amoeboids
Ciliates
Flagellates
Sporozoans
Apicomplexans (coccidia)
Definitive host
Required for all parasites (need host to survive or reproduce)
Adult parasites are in the DH
Parasites undergoes sexual reproduction inside DH
Sometimes asexual reproduction in the DH
Intermediate host is
Required for many parasites (indirect life cycles)
Parasite undergoes development within IH
Never sexual reproduction
Paratenic host (PH)
helpful but not required
PH- infection occurs bu no reproduction, no development
Transport host
helpful but not required
No infection, simply transport (mechanical vector)
Shed stage is
Shed stage- and infection stage
Shed stage is what leaves the infected host (egg, larva, cyst etc.)
Infective stage is
Infective stage is what is infective to the next host- usually takes time in the enviro for a shed stage to become in infective stage
Prepatent period is
(PPP)(infected but not shedding detectable numbers of shed stages- eggs or larvae etc)
Patent period is
infected and shedding detectable numbers of shed stage
Prevalence is
%infected in a population) and intensity( how many parasites in an infected animal
How to acquire parasites
Ingestion of infective stages from a contaminated environment
Ingestion of infective stages in infected intermediate hosts, often regular prey
Skin penetration by infective stages
Inoculation of infective stages by infected arthropod vectors
Transfer of infective stages by direct contact with other infected hosts
Transmammary infection of larvae from mother to offspring
Other
Nematodes are
(roundworm)
Parasitic and free-living species
Tiny (<1mm) to enormous (40cm)
Genders separate (dioecious), sexual reproduction within DH
Eggs or larvated eggs, or larvae (diagnosis; finding these stages)
Direct and indirect life cycles
Live in many hosts and tissues twitch host and tissue specificity
Larvae of some species undergo complicated migrations
Oviparous is
female nematode that passes eggs in the single cell stage or the morula stage (solid mass of cells, clustered together)
Ovoviviparous is
female nematode that passes eggs with a first stage larva contained (and visible)
Larviparous is
female nematode that retains the eggs within the uterus till they mature and hatch and then pass live first-stage larvae
How can nematodes infect hosts
Ingestion of infective eggs or larvae from the environment, contaminated food or water
Ingestion of larvae within intermediate host or paratenic host
Skin penetration by infected larvae
Inoculation of infective larvae from an arthropod vector
Prenatally from mother to fetus
Through the mammary gland from mother to suckling young
Each species of nematode has its own route(s) of infection
How to identify nematodes
Identification of nematode adults requires details such as host, size of worm, morphological features of the worm, usually on the head and tail ends
Egg morphology is more commonly used for diagnosis, this also varies, for example, the presence or absence of larvae in the egg, size, and other morphological features (operculum, polar plugs, color, etc,.)
How to diagnose parasites
Fecal Flotation
Helminth eggs (most), some protozoal oocysts
Baermann larval sedimentation- live larvae in fresh feces submerged in water wiggle out and sink
PCR and antigen based methods of detection and identification of parasites
Cestodes (segmented flatworms)- basic features
All species parasitic
Some tiny (2mm), some enormous (12m)
Hermaphrodite
All have an indirect life cycle with intermediate host(s)
Adults in DH parasitize the GI system, cause few problems and produce eggs immediately infective for the IH
Larval stages in tissues of IH may cause serious problems
Asexual reproduction may occur in IH depending on species
Cestode structure
Have segmented sections
immature segments–> mature segments–> gravid segments
Segment = proglottid
What type of lifestyle does a cestode have
indirect
Diagnostic parasitology for cestode
Fecal float
Trematode (leaf shaped flatworm)- basic features
All parasitic
From tiny (<1mm) to giant (10cm)
Hermaphroditic (veterinary importance)
Sexual reproduction occurs in DH
All have an indirect life cycle with intermediate host(s)
First IH always a gastropod (slug or snail)
Asexual reproduction in gastropod IH
Adults in DH parasitize GIT or lungs; sometimes pathogenic
Larval stages in IH parasitize many tissues; rarely pathogenic
Trematode transmission to the definitive host by
Ingestion of infective metacercariae on vegetation
Ingestion of infective metacercariae in intermediate hosts
Skin penetration by cercariae
Through mammary gland from mother to suckling young
Each species of trematode has its own route of infection
Diagnostics for trematode
Fecal sedimentation
For eggs too dense to float
Primarily trematode eggs
Arthropods- important groups
Arachnida
Insecta
What are included in arachnida
Mites and ticks (acari)
What are included in insecta
Bugs (hemiperta)
Lice (mallophaga and anoplura)
Fleas (siphenoperta)
Flies (diptera)
Mites are
Dorso-ventrally flattened
Six legs as larva
Eight legs as nymph and adult
Variable host specificity
Microscopic
“Hariry”
How to tell the difference b/w a burrowing and surface mite
Burrowing mites
Short legs
Surface mites
Long legs
Mites basic life cycle
adults –> eggs–> larvae–> nymphs
Life cycle complete in about 10-14 days
Note: generally (but not always) the entire life-cycle is on the host
Ticks are
Dorso-ventrally flattened
Six legs as larva
Eight legs as nymph and adult
Not very host specific
Macroscopic
Smooth
Time to complete life cycles highly variable, depending on species and environment
Two types of ticks
Hard ticks
Ixodidae
Soft ticks
Argasidae
Life cycle stages of ticks
Egg→ larva (3 pairs of legs) → nymph (4 pair of legs) → adult
All stages require a blood meal to develop to the next stage
One-host ticks life stage
attach first as larvae, feed and moult to a nymph, feed and moult to an adult and fall off the original animal as adults and lay eggs in the environment- weeks to months later
Two-host ticks life stages
Attach on host 1 as a larva, feed and moult to a nymph on the host. Feed as a nymph and fall off the host 1. Moult to an adult in the environment and then find a new host as an adult. Mate and fall off into the environment to lay eggs.
Three-host ticks life stages
attach to host 1 as a larva, feed fall off and moult to a nymph, attach to the host 2 as a nymph, feed and fall off into the enviro. Moult to an adult. Attach to host 3 and feed and mate on the third host. Fall off into the enviro to lay eggs
They life cycle of a three host tick may take 2 or 3 years or longer depending on host availability
Insect characteristics
Three pair of legs
Three distinct body regions (head, thorax, abdomen)
Head: two eyes, two antennae, and complex mouthparts
Thorax: six legs and anywhere from zero (i.e fleas and lice) to four wings (i.e. beetles and some bugs)
Abdomen: Reproduction eggs or larvae
Bugs are and the two types
Dorso-ventrally flattened
Six legs
Variable host specificity
Cimidae
-Bed bugs
Reduviidae
-Assassin bugs
-Kissing bugs
-Cone-noses
Life cycle of bed bugs- Cimex lectularius
Adults (on host only to feed)–> eggs in the enviro–> nymphs on host only to feed (blood feed)
Lice are
Dorso-ventrally flattened
Six legs
Quite host specific
Mallophaga
Chewing/biting lice
Head wider than thorax
Anoplura
Sucking lice
Head narrower than thorax
Fleas characteristics
Laterally flattened
Six legs
Not host specific
Types of flies
Nematocera
Brachycera
Cyclorhapha
Time to complete life cycle highly variable, depending on species and enviro
Nematocera flies types
Mosquitos
Blackflies
Midges
Brachycera flies are
Horseflies
Deerflies
Cyclorhapha flies are
Faceflies
Hornflies
Botflies
Arthropods can harm the animal host through several means
Annoyance- decreased feeding sleep and poor hair coat
Blood loss- lice can drop a PCV to <10%
Produce venoms and toxins- tix paralysis (ascending flaccid paralysis), spider bites
Dermatosis (skin disease)- mange mites
Miasis (infection of the flesh of the living animals with fly larvae)- cattle warbles
Allergic reactions- flea dermatitis, dust mites (serious allergies in people), anaphylaxis from death of warbles in cattle
Vectors for disease agents
Mechanical vectors (transport hosts)- flies carry Trypanosomes, etc
Biological vectors(intermediate hosts)- mosquitoes carry heartworm, fleas carry Dipylidium caninum
Diagnosis of arthropods
Finding adults or immature stages and identifying them (as boat as one can- e.g. fleas)
Sometimes symptoms
Sometimes test treatment
Protozoa is
Single-celled, eukaryotic organisms
Approximately 64 000 species described of which only 7 000 are parasitic to animals. The rest are free-living
Protozoans infect a variety of tissue sites within the definitive host
The most common sites for protozoal detection
Blood samples- hemoprotozoa
Most are found in the erythrocytes within a stained blood smear
Ticks and blood sucking insects often serve as the IH and transmit RBCs containing the hemoprotozoa
Can also find antigens or antibodies in blood samples
Fecal samples- intestinal protozoa
Tissue samples
Zoite means
body
Trophozoite is
the stage of the protozoan life cycle that is capable of feeding, movement and reproduction; often too fragile to survive transfer to a new host
How do protozoas transmit
Transmission to a new host most often occurs when the protozoan is in the cyst state or oocyst stage
Most metabolic functions are suspended when the parasite is encysted
Cyst wall prevents desiccation and protects it from other enviro damage
Locomotor organelles are and used for
Used to help identify the type of protozoa recovered from an animal
Flagella
Cilia
Pseudopodia “false feet”
Flagella on protozoa is
Long, whiplike structures
Single or multiple
Flagellates Trichomonads, Leishmania, Giardia
Sometimes the flagellum passes backwards along the cell, joined at a few or several points and is thus termed an undulating membrane (Genus Trypanosoma)
Cilia on protozoa are
Short flagella, usually arranged in rows or tufts
Typically found in various arrangements around the mouth and/or rural groove of the ciliates such as Balantidium coli and Ichthyophthirius multifiliis
Pseudopodia “false feet” on protozoa are
Temporary extensions and retractions of the body wall to surround potential food particles or for movement
Typical of amoebas such as Entamoeba histolytica
Protozoa of vet importance
Flagellates
Mucosoflagellates
Direct life cycle
E.g giardia (Direct life cycle)
Tritrichomonas spp. (direct life cycle)
Histomonas (indirect life cycle)
Hemoflagellates
Arthropod-transmitted
E.g. Trypanosoma
Ciliates
Direct life cycles
Asexual reproduction (binary fusion)
E.g. Balantidium coli in swine (rarely zoonotic)
E.g. Ichthyophthirius multifiliis in fish (ich)
Sporozoa/apicomplexans
Coccidia
Direct life cycles (GIT)
E.g. Eimeria
Indirect life cycles (tissue cysts)
E.g. Toxoplasma
Haemosporidia
Arthropod-transmitted
E.g. babesia
Amoebae
Direct life cycle, asexual reproduction
Free-living Amoeba (humans, dogs)
Acanthamoeba spp.
Naegleria fowleri
Apicomplexans: coccidia
Direct (D) or indirect(I) life cycles
Eimeria D
Cystoisospora D/I
Cryptosporidium D
Toxoplasma I
Neospora I
Sarcocystis I
Eimeria spp. – coccidia of ungulate
Problems caused by protozoal infections
Diarrhea
Fevers and flu-like symptoms
Neurological signs
Abortions
Skin lesions
Diagnosing protozoa
Appearance on fecal smear/flotation
Fecal smear- simple, quick, low sensitivity
False - are common
Protozoal trophozoites (esp. If symptomatic) and cyst
Fecal flotation
Various flotation solutions
Protozoal oocysts (Coccidia, sarcocytes)
Immunofluorescent tests
Immunohistochemistry
Serology
Molecular detection and identification
