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veterinary parasitology, external and protozoa


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flea infestations
fleas general
adult fleas are wingless
body compressed laterally
powerful hind legs allowing them to jump great distances
seven feed on blood
Not host specific
flea life cycle
complete metamorphosis with egg, maggot-like larval stages, pupae, and adults. Adults are parasitic and feed on blood; other stages found in hosts' environments.
Eggs laid on host (drop off) or in the environment.
larvae hatch and feed on flea's feces.
There are three larval stages growing from 2mm to 5mm.
Third larval stage pupates which is most resistant to the environmental stress.
Heat, carbon dioxide, and movement stimulate adults to emerge from pupa.
Fleas tend to survive best in humid conditions
distribution world wide
present in humid areas
life cycle is 3 weeks to 20 months
dog and cat
Ctenocephalidies canis
Ctenocephalidies felis
common name: Human flea
hosts: Humans, dogs, cats, cattle,pigs, rats
Pulex irritans
common name: oriental rat flea/ tropical rat flea
Hosts: rats humans
Distribution: Africa, asia, western USA, South America
Xenopsylla cheopis
Distribution; worldwide
life cycle: one month
Hosts: birds dogs cats rabbits horses humans
Common name: sticktight flea
Echidnophaga gallinacea
veterinary importance of fleas
flea allergic dermatitis
vector of disease
lice infestation
sucking lice
chewing lice
sucking lice of swine and cattle
sucking lice of dogs, cattle, goats, sheep
sucking lice of cattle
chewing lice of cattle, horses, goats, sheep
chewing lice of dogs
Chewing lice of cats
seasonal occurance of lice
permanent parasite on the host all year
in warm countries there is no marked seasonality.
In cold and temperate regions the heaviest infestations are in late winter and early spring in cattle and horses.
little seasonality in dogs and cats
lice life cycle
-incomplete metamorphosis with 3 nymphal stages resembling adults
-spend entire life on the host; if removed from the host, can only live one week
-Transmission primarily by direct contact, but fomites can also play a role
-separate sexes
-females lay eggs which attach to hair (glue)
-Nymphs hatch from eggs (cap on egg from which nymph escapes)
-eggs remain viable on hair for months
-eggs often easier to see than adults
-Life cycle can be completed in as little as 3 week period
Common name for lice eggs
Veterinary importantce of lice
dermal irritation
lower animals resistance
vectors for disease
secondary infections of bite wounds
Non-burrowing mites
Burrowing mites
Follicular mites
mite life cycle
-incomplete metamorphosis with larval and nymphal stages resembleing adults
-seperate sexes with female laying eggs on the host
-Nymph and adults feed on lymph of host and molts to another nymph or adult
-spend entire life on host (except for bird mites)
-spread primarily by direct contact
mite veterinary importantce
-secondary infections
-lower animal's resistance
Hosts: cattle and rabbits
Distribution: worldwide
Oval, all legs projecting beyond body margin
pedicles are long and jointed
Psoroptes bovis (cattle)
Psoroptes cuniculi (rabbits)
seasonal occurrence of Psoroptes bovis
mites are on the animal all year but build up in numbers during the winter
Psoroptes mange in cattle is a _________ disease
foot and tail mange
Hosts: bovine, rabbits, llamas, horses
Distribution: worldwide
pedicels are short and unsegmented
Chorioptes bovis
Chorioptes cuniculli
Chorioptes importance
in cattle, occurs most often housed animals
affects mainly the tail, head, and udder
Ear mite
Dog and cat
Distribution: worldwide
short unsegmented pedicels
Otodectes cynotis
Most common mange in dogs and cats throughout the world
Mites feed in external ear canal, but can be found on the body
Otodectes cynotis
Rabbit fur mite
Hosts: dogs,cats,rabbits, humans
Distribution: worldwide
Cheyletiella yasquri (dogs)
Cheyletiella blakei (cats)
Cheyletiella parasitiovovorax (Rabbits)
body has a waist
palps are enlarged ending in prehensile claw
legs terminate in combs instead of claws
Cheyletiella Veterinary importance
Transmits to humans, therefore has public health significance
In most cases, in dogs and cats only midly pruritic
non-burrowing mite
red mite of poultry
spends most of life cycle off the host
Feeds mostly at night
Can infect other animals and humans
Non-burrowing mite
northern fowl mite
spends entire life on the bird
Non-burrowing mite
nasal mite of dogs
found in nasal cavity and sinuses
life cycle unknown
Pneumonyssus caninum
burrowing mite
Hosts: humans all domestic animals, especially swine and dogs
Distribution: worldwide
Sarcoptes scabiei
Only anterior legs extend beyond body
Pedicle is long and unsegmented
Sarcoptes scabiei
Life cycle of Sarcoptes
-Female creates a winding burrow in the upper layer of the epidermis
-Eggs are laid in these tunnels, and hatch to six-legged larvae
-These larvae crawl onto the skin surface, creating small molting pockets
-entire life cycle is completed in seven to ten days
Sarcoptes veterinary importance
-extremely pruritic
-In dogs, the mite will usually infest all dogs in the same household
-This dog mite will also infect humans, but will only establish for a short period of time
Burrowing mite
Head mange in cats
Distribution: worldwide
resembles Sarcoptes
Notoedres cati
Burrowing mite
scaly leg mite
Hosts:poultry and cage birds
Distribution: worldwide
resmbles Sarcoptes
Knemidocoptes spp.
Red or follicular mange
humans and all domestic animals
Demodex canis
Demodex spp.
Adults are worm-like with short stubby legs
eggs are tapered at both ends
Demodex life cycle
Part of normal skin fauna
all life cycle stages found on host in hair follicles
transmission from bitch to neonates occurs during first two to three days of life
soft ticks
Hard ticks
Hard ticks differnce between
male and female morphology
Hard shell only covers anterior end on female
chitinous covering of dorsal surface of hard ticks
notches on posterior boarder of some hard ticks
Ornate ticks
ticks with a colored pattern to scutum
located posterior to fourth pair of legs on hard ticks
Hard tick life cycle
-Developmental stages: adult, egg, larva, and nymph
-All stages feed on blood,except the egg
-Mating takes place either on or off the host, after taking one blood meal, females drop off host to lay eggs and die
-males reamain on host, take another blood meal and mate with other females
-female ticks require a blood meal prior to egg production
-certain hard ticks can survive for months, even years without feeding
-some hard ticks require more than one year to complete the life cycle
Veterinary importance of ticks
tick worry
vector of disease (most important)
blood loss
tick paralysis
one host tick
-adults feed and females drop to ground, lay eggs and die
-eggs hatch and larval tick crawls onto a host, feeds, then remains on same host and molts to nymphal tick
3 host tick
-adult tick feeds, drops to the ground
-female lays eggs and dies
-larval tick emerges from egg, crawls onto a new host and feeds, then drops to the ground and molts to nymph
-nymphal tick crawls on a third host, feeds and drops to ground and molts to adult
-adult tick crawls ont new host, feeds, and drops to the ground
Rocky mtn. wood tick
scientfic name:
# of hosts
Dermacentor andersoni
American dog tick
Scientific name
# of hosts
Dermacentor variabilus
Winter or Elk tick
scientific name
# of hosts
Dermacentor albipicts
Tropical Horse tick
Scientific name
# of hosts
Dermacentor nitans
Pacific coast tick
Scientific name
# of hosts
Dermacentor occidentalis
Adults on large animals, dogs and humans
larvae on small rodent
Dermacentor andersoni (rocky mtns.)
Dermacentor variabilis (east of rockies and CA
Dermacentor andersoni
Dermacentor variabilis
vectors for:
rocky mtn. spotted fever
tick paralysis
One host tick
Host: equine
Occurs in south east
vector for babesia
Dermacentor nitans
One host tick
Hosts: horse and elk
Dermacentor albpictus
3 host tick
adults on large animals
larval stages on rodents
Dermacentor occidentalis
3 host tick
dogs for all stages
vector for babesia and erlichia
most common tick on worldwide basis
Rhipicephalus sanguineus
3 host tick
adults on all domestic animals
Immature on rodents and birds
southern states and midwest
deep feeder and second infection common
Amblyomma americaniun
Amblyomma maculatum
Amblyomma americaniun and Amblyomma maculatum are vectors for
rocky mtn spotted fever
lyme disease
deer tick
3 hosts
Ixodes dammi
western black legged tick
3 hosts
Ixodes pacificus
black-legged tick
3 host tick
Ixodes scapularis
deep feeding tick
vector for lyme disease and borrelia
N. America
S. Africa
adult on large animals
immuture on rodents and birds
Cattle fever tick
one host tick
soft body
S America
central America
vector for anaplasma and babesia
Booboilus annulatus
Booboilus decoloratus
Fowl tick
Birds mammals humans
Argus persicus
Argus life cycle
one larval stage, 2 nymphal
all stages feed at night
transmits borrelia and aegyptianella
tick can live for years
Spinous ear tick
all domestic and wild animals
only larval and nymphal ticks are parasitic
ticks feed in ear canal
Otobius megnini
Sand tampans
all mammals
only nymphs are parasitic
vector for foothill abortion and
relapsing fever
Ornithodoros spp.
In humans and animals, parasitic __________ are found in every tissue and organ system in the body
protozoa locomotion structures
Protozoa move by means of flagella, cilia, pseudopods, or undulating membrane
a whip like organelle composed of a central axoneme and an outer sheath
Undulating membrane
fin like organelle in which a flagellum may be buried in the organelle membrane along much of its length
used as a means of locomotion and are prolongations of the cytoplasm and movement occurs as the rest of the cyctoplasm flows into the prolongation. pseudopodium also have a phagocytic capability and can function as a cup which closes, enveloping particlate food materials in a vacuole
short hairs, each arising from a basal body. They cover much of the body surface and beat in unison to effect movement. In some species, a mouth or cytosome is present and the ciliary movement is used to move food toward opening
binary fission in protozoa
each individual divides into two. The division may either be longitudinal, as in flagellates, or tansverse, as in ciliates
Multiple fission in protozoa
the nucleus divides several times before the cyctoplasm divides. The dividing cell is known as a meront, schizont, or agamont
Conjugation in protozoa
two individuals come together temporarily and fuse along their length. This type of reproduction is seen in the ciliates
Syngamy in protozoa
sexual reproduction: two gamets fuse to form a zygote. The smaller male gamete is called a microgamete and the larger female a macrogamete. this type of reproduction is common in all parasitic protozoa
The _________ are a diverse group of parasitic organisms.
They have in common a clustering of organelles at the anterior end of the zoites called the _______ ________.

apical complex
apicomplexans are found primarily in?
epithellium of intestines
blood cells
cells of reticuloendothelial system
apicomplexans locomotory organells
internal and not visible to the naked eye
important genera of parasitic apicomplexans of domestic animals
True Coccidia:
Other Coccidia:
True Coccidia:
Eimeria spp.
Isopora spp.
Other Cocidia:
Crytosporidium spp.
Toxoplasma spp.
Sarcocystis spp.
Neospora spp.
Unsporulated oocyst
Sporulated oocyst
Coccidia eimeria sporulated oocyst
each has four sporocysts containging two sporozoites
Coccidia isopora sporulated oocyst
each have two sporocysts containing four sporozoites
Isopora in dogs
Isopora canis
Isopora ohioensis
Isopora in cats
Isopora felis
Isopora rivolta
Isopora in swine
Isopora suis
Isopora is ______ disease.
Coccidia veterinary importantce
-all coccida are very host specific
-younger animals are more susceptible (older animals develop immunity
-Pathology is primarily associated with destruction of intestinal cells
-More commonly seen in stressed animals
sporulated oocyst passed
sporozoites invade brush boarder of enterocytes and trophozoites differentiate to schizonts (meronts) with 4-8 merozoites
Merozoites develop into macro or microgametes
Cryptosporidium life cycle
Oocysts are produced from the macro/microgametes in 72 hours
-oocysts sporulate before leaving the host
-two types of oocysts produced
Two types of cryptosporidium oocyst
Thin walled: break and re-infect host
Thick walled: pass in feces
veterinary importance of crytosporidia
Primarily a disease of calves and kittens
Has public health significance and will transmit to humans
Definitive host: all felids
intermediate hosts: all mammals, including humans, and birds
the cat may also be intermediate host and harbor extraintestinal stages
distribution is worldwide
Toxoplasmosis gondii
extra-intestinal forms of toxoplasmosis
Tachyzoite: cresent shaped
Bradyzoite: lancet-shaped
Intestinal forms of toxoplasmosis
Toxoplasmosis oocysts
sporulated contain two sporocysts, each with four sporozoites/unsporulated oocyte passed in feces
Toxoplasmosis sexual stage
Felidae only
1. cats become infected by ingesting tissue containing bradyzoites (rarely tachyzoites)
2. Microgametocytes and macrogametocytes develop in the epithelial cells of the small intestine
3. Microgametocytes fertilize macrogametocytes
4. zygote develops
5. zygote them matures into an oocyst
6. oocyst is passed in the feces
Toxoplasmosis asexual stage
humans and other animals
1. humans/ other animals become infected by ingesting tissue containing bradyzoites(rarely tachyzoites)
2. Humans/cats/other animals become infected by ingesting the oocyst contained in cat feces and by ingesting tissue with bradyzoites
3. Tachyzoite develops
4. macrophages pick up tachyzoites and carry them (via bloodstream) to all parts in the body (may be carried to the fetus in pregnant animals and humans)
5. Tachyzoite divides in various tissues until the immune system limits the multiplication of the organism
7. Bradyzoite forms a pseudocyst in various tissues of the body
Veterinary importance of toxoplasmosis
primary cause of abortion in sheep in some countries
has public health significance and will transmit to humans infecting the fetus in-utero
In humans, may cause blindness or a flu-like disease
Equine Protozoal Myeloencephalitis vector
Sacrocystis neurona
sexual stages in carnivores
asexual stages in herbivores
oocyst passed in definitive host is sporulated
sarcocystis oocyte
sporulated oocyte
two sporocysts with four sporozoites/sporulated oocyte passed in feces
life cycle of sarcocystis
1. definitive host ingests the bradyzoite cyst (schizonts) from tissue (muscle) of thee intermediate host
2. gametogony occurs in intestinal cells of definitive host
3. sporulated oocysts are passed in the stool
4. Intermediate host ingests oocysts
5. sporozoites are liberated, penetrate intestinal wall, and spread by the hematogenous route
6. Tachyzoites(proliferative stage) multiply in endothelial cells of various tissue
7. bradyzoite cyst form in muscle fibers
Veterinary importance of sacocystis
usually asymptomatic
large number of cysts in birds, rarely in domestic animals, will cause condemnation of the meat
Definitive host: dog
intermediate host: cattle, sheep, deer, horses, rodents, and cats
first identified in dogs in Norway in 1984
major cause of abortion in dairy cows in the early 1990
Neosporosis caninum
Neospora oocyst
Sporulated oocysts cantain two sporocysts, each with four sporozoites
-tissue cysts are round to oval
-unsporulated oocysts can be recovered from dog feces
_______ and _______ cysts can be found in may tissues and organs in the intermediate host.
________ tissue cysts are most commonly found in the _____and other neural tissue
Tachyzoite bradyzoite
bradyzoite brain
Life cycle of neospora
1. Transmitted horizontally through the ingestion of oocysts from infected dogs
2. Transmitted vertically from the cow to the calf
3. Dogs pass only a few oocysts in their feces
4. oocyst becomes sporulated in the environment
5. sporulated oocysts are ingested by the intermediate host
6. Sporozoites are liberated from the sporulated oocyst, then enter cells and become tachyzoites
7.Tachyzoites divide rapidly, cause tissue damage, and spread the infection
8. Tachyzoites eventually enter other cells and become bradyzoites
Note: Only the basic are known about the transmission of Neospora. The dog is the only known definitive host. Sporocysts can live for a considerable time in the environment.
veterinary importantce of Neospora
-can be found in every state in the USA
-most common cause of abortions in Ca dairy cattle
-Accounts for approximately 40000 abortions in California dairy herds annually
-cost the Texas beef industry $37 million in 2001
infects most domestic animals as well as birds and wildlife
-not very host specific and humans can be infected form other animals
-a very difficult disease to treat
Trophozoite stage of Giardia
bilaterally symmetrical
six paired flagella ( 2 anterior 2 lateral 2 caudal)
2 nuclei
2 fused axonemes
Cyst stage of Giardia
oval or football shaped
4 nuclei
central axoneme
cytoplasm retracted from cyst wall
Giardia life cycle
1. Animals are infected by ingestion of the cyst stage in contaminated water or food
2. The cysts divide to form two trophozoites (in the small intestine)
3. The trophozoites attach to the epithelium of the small intestine using a sucker-like disc
4. Encystment occurs in the small intestine and the cyst stage is passed in the stool
backpackers diarrhea
only have one stage
reproduce by binary fission
infertility in cattle
embryonic death of fetus
very common in western beef herds
reportable disease
Trichomonas foetus (bovine)
Trichomonas gallinae (birds)
Trichomonas morphology
Tropozoite stage (only stage)
-3-4 anterior flagella
-undulating membrane
-hyaline rod/axostyle originates at base of flagella, passes down the center of the cell and may project posteriorally as a small spine
-nucleus at anterior end of cell
Trichomonas life cycle
Trichomoniasis in human and cattle is a venereal disease and transmission is usually by sexual contact. Bulls, once infected, remain so permanently
1. The organisms inhabit the preputial cavity of the bull
2. Transmission to the cow occurs during coitus
3. from the vagina, the trichomonads reach the uterus via the cervix to produce a low-grade endometritis
4. Intermittently, organisms are flushed into the vagina, often 2 or 3 days before oestrus
-evident in most parts of the world, except for North America, where it has been eliminated in cattle
-major disease in domestic animals in endemic areas
-in USA it occurs mostly in dogs and sometimes horses
-occurs in RBC
Babesiosis life cycle
definitive host is ixodid ticks
1. Ticks beocme infected while feeding on blood from infected animals
2. sexual development occurs in the gut of the tick, resulting in the production of elongated motile club-shaped bodies called vermicules
3. vermicule migrate to various tissues of the tick, especially the ovary
4. further multiplication of vermicules takes place in the ovary
5. vermicules invade the eggs of the ovary (tarnsovarian transmission)
6. Organisms continue to multiply in newly hatched larval ticks
7. Larvae feed, vermicules enter the salivary acine and form infective sporozoites
8. sporozoites are inoclated into the new host as the tick feeds

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