AVS 4090 Parasitology Exam 2

Reinfection of T. Gondii

If a cat is reinfected it will result in low-grade shedding of oocysts of short duration which is a minor source of infection

Shedding of Oocysts in N. caninum

N. Caninum uses dogs as a definitive host, producing oocysts that are shed in the feces after ingestion of tissue cysts from beef. Coyotes will produce oocysts when fed meat of the white-tailed deer suggesting a potential sylvatic cycle

Seropositive cows and N. caninum

may produce less milk and are more likely to be culled earlier.

Diagnosis of H. americanum

Diagnosis typically requires the examination of muscle tissue collected at biopsy or during necropsy. A large cystic form of the organism occurs in skeletal muscle. You can now also do molecular analysis of blood or biopsy material to get a diagnosis.

Where are the sporozoites of babesia found?

Sporozoites are found in the salivary glands and undergo further multiplication when the tick is feeding; they are then passed in the saliva as the tick continues to feed

Pythium causes disease in what species

Causes disease in horses, cattle, dogs, humans, cats, goats, sheep, birds, and bears

Gastrointestinal pythiosis

persistent vomiting, diarrhea, weight loss, mesenteric lymphadenopathy, mucosal ulceration, and segmental transmural thickening of the stomach, s.i., colon, rectum, esophagus, and pharynx

Treatment for cutaneous pythium

surgical resection and chemotherapy.

Entamoeba histolytica can cause severe disease in

primates

reproduction of Entamoeba histolytica

Usually reproduce asexually, by binary fission

Does Acanthamoeba have a flagellate form

No it does not

digestive tract of Flukes

The digestive tract (if present) has only one opening (the mouth) with digested food being regurgitated from the oral opening. The Cestoidea do not have a digestive tract in any life stage. The excretory system is a tubular network with

clumps of flagellum-bearing cells, flame cells, which propel waste along the collection system to the excretory pore

Where do adult flukes live

in the bile ducts of ruminant and other mammalian hosts

What is the importance of water with F. hepatica

Only if the egg falls into water will a ciliated larva called a miracidium develop inside it.

When does the miracidium exhaust its energy stores and die?

if it fails to find a snail within 24 hours

If the miracidium finds a snail

it will bore into its body, lose its ciliated covering, migrates to the liver, and forms a sporocyst

Fluke cercaria

a tadpole-like larva with a discoidal body and a long tail for swimming

metacercaria

the stage that is infective to sheep and other grazing mammals.

migration of the young fluke

The young fluke penetrates the wall of the intestine and crosses the peritoneal space to the liver, which it penetrates

under favorable conditions how long is the complete life cycle of the fluke

The complete life cycle encompasses 3 or 4 months under favorable conditions.

How do soil characteristics play into the lifecycle of the fluke

Because soil characteristics may vary dramatically within very short distances, it is not uncommon for one "fluky pasture" to contain all of the F. Hepatica snails and metacercaria, whereas the rest of the farm may afford safe grazing

Acute fluke disease

severe inflammation, abdominal pain, lethargy, reluctant to move. Enlarged, friable liver. The animal may die so fast that they hardly have time to be sick.

Chronic fluke disease

adult trematodes are present in the bile duct. Gradual loss of condition, progressive weakness, anemia, hypoproteinemia, edematous subcutaneous swellings

How many flukes required for condemnation of

the liver in slaughtering establishments?

only one fluke

Prevention of aquatic snails

Aquatic snail can be controlled by draining swamps

Treatment timeline for flukes

Treatment must be used to treat animals more than 49 days before slaughter and cannot be used in female dairy cattle of breeding age

is Paragonimus kellicotti zoonotic?

Yes it infects human

Where does Paragonimus localize

Located as pairs or larger numbers in cysts in the lungs of mammals

second intermediate hosts of Paragonimus

Freshwater crabs and crayfish

Paragonimus kellicotti infects what species

Can infect cats, dogs, and many species of wild mammals may become infected by eating crayfish containing the

encysted metacercariae or by eating animals that have recently fed on crayfish.

Where are Paragonimus eggs taken

The large, vase-shaped eggs are eventually swept up the

tracheobronchial tree, swallowed, and passed out with the feces

What happens if the Paragonimus eggs arrive in water?

miracidia develop and hatch in about 2 weeks and enter an operculate snail in which cercariae develop through one sporocyst and two redial stages. The cercariae leave the snail and encyst as metacercariae in freshwater crayfish

When are the lung cysts able to be visualized with radiographs

The lung cysts are visible radiographically at 28 days and eggs are first shed in the feces about 1 month after infection

Can Paragonimus be treated

yes with Praziquantel (droncit), Fenbendazole, Albendazole

What role do snails play in Schistosomiasis

they are the intermediate hosts

Another name for Schistosomiasis

Snail fever

what stage is missing in Schistosomiasis

There is no metacercarial stage

What do the Schistosomiasis cercariae penetrate

the skin of the final host to complete the life cycle

Schistosomiasis eggs lack

an operculum

Schistosome eggs hatch on exposure

to water

Heterobilharzia americana characteristics

The adults are found in the mesenteric veins, and the eggs that are deposited make their way through the

intestinal wall to be passed in the feces. The miracidium hatches soon after the egg comes in contact with water and

then enters a freshwater snail in which cercariae develop in daughter sporocysts

PPP of Heterobilharzia americana

The PPP is about 60 days after which the eggs which were laid in the terminal branches of the mesenteric veins, passively work through the bowel wall to the lumen and escape with the feces

Heterobilharzia americana is also called

Canine Schistosomiasis

Heterobilharzia americana parasites description

elongated and unisexual

Is Schistosomiasis treatable

yes it has 2 treatments: Fenbendazole and Praziquantel

Cestodes are commonly known as

tapeworms

two unmistakable morphological features of cestodes

they all possess flat, ribbon-like bodies and lack an alimentary canal

scolex function of cestodes

help cestodes attach themselves to the mucosa; four radially disposed muscular suckers

Cyclophyllidean oncospheres cestodes

fully developed when passed in the feces of the definitive host and are immediately infective for the intermediate host.

Which cestode stage shows a wide range of habitat

preferences

Larvae show a wide range of habitat preferences, being found in almost any organ of both vertebrate and invertebrate hosts. Though most larval species show a preference for a particular site

cestode rostellum

retractable into the scolex and may be armed with small

hooks. Strong muscles operate these hooks in a concerted and rhythmic clawing motion

Cyclophyllidean that lack rostellar hooks

tend to have more strongly developed suckers

the cestode eggs accumulate until the segment becomes packed full like a ripe seapod then

As they reach the end of the chain, these gravid segments are detached and pass out with the feces or crawl out the anus onto the perianal skin

cestode intermediate host

The intermediate host that contains the metacestode may be

a mammal or an arthropod except for Mesocestoides where the final host is a mammal and the second host can be a mammal, bird, or reptile (the intermediate host has yet to be identified).

Are tapeworms hermaphrodites

Yes

Adult tapeworms inhabit

small intestine

Taenia saginata characteristics

the beef tape worm. It is the most common large tapeworm of humans causing intestinal taeniasis. The infection is acquired orally by ingesting beef infected with the larvae

(Cysticercus bovis) of the parasite

Taenia solium characteristics

pork tapeworm. This tapeworm infects humans.

tapeworm Eggs first appear in the feces

6 to 9 weeks after ingestion of the metacestode

cysticercosis caused by

the cestode larva (Cysticercus cellulosae)

T. solium crucial characteristic

T. solium is the only cestode for which man acts as both the definitive host (harbouring the adult worm) and the intermediate host (harbouring the larva of the

parasite). The tapeworm causes cysticercosis, especially neurocysticercosis, a serious disease in humans

Geographical importance of T. solium

found worldwide. Because pigs are intermediate hosts of the parasite, completion of the life cycle occurs in regions where humans live in close contact with pigs and eat undercooked pork.

Taenia pisiformis

canine taeniid tapeworm where the cysticercus is found

in the liver and peritoneal cavity of rabbits. This is the

most common taeniid tapeworm of dogs in the US. Every

dog that becomes infected must have eaten a rabbit or parts of a rabbit AND that rabbits are grazing near where the segments are being shed.

Taenia hydatigena characteristics

Canine taeniid tapeworm with a cysticercus that migrates

through the liver tissue and encysts on the peritoneal membrane of cattle, sheep, swine, and certain wild ungulates.

Taenia hydatigena results in

acute traumatic hepatitis

Diagnosis of tapeworms

The basic diagnosis is done from a stool sample. Feces are examined microscopically to find parasite eggs. The eggs

look like other eggs from the family Taeniidae, so it is only possible to identify the eggs to the family, not to the species level.

Taenaisis treatment

praziquantel

prevention of Taenaisis

Adequate cooking and Refrigeration, freezing

2 important species of ECHINOCOCCUS

Echinococcus granulosus and Echinococcus multilocularis

characteristics of ECHINOCOCCUS

small adult tapeworms with only four or five segments and only the terminal segment is gravid

Echinococcus granulosus infective stage

eggs in feces

Echinococcus granulosus disease

Hydatid disease

Echinococcus granulosus metacestode characteristics

is a unilocular hydatid cyst that occurs primarily in the livers of sheep, swine, cattle, humans, moose, caribou, and kangaroos

Echinococcus multilocularis is the parasite of

canids, mainly foxes and wolves in artic regions

Dogs infected with D. caninum often

sit downand drag their bottoms from infection

is there a treatment to D. caninum

yes, but for lasting results to be obtained, the source of

infection must also be dealt with, or the segments will reappear, and the client may not. (controlling the fleas)

Hymenolepis diminuta characteristic

parasite of the small intestine principally of rodents but occasionally also of dogs and even humans

Hymenolepis diminuta mode of transmission

ingestion of rat flea containing cysticercoid

health hazard of Hymenolepis diminuta

Because the eggs discharged in feces are infective to humans, infection in laboratory rodent stocks constitutes something of a health hazard for personnel

Where can Hymenolepis diminuta complete its life cycle

within the intestinal tract of a mouse or a human.

Crucial characteristic of Hymenolepis diminuta

autoreinfection: Some of the eggs hatch within the intestine, and the hexacanth embryos burrow into the mucous membrane to form cysticeroids that later reenter the lumen to complete their development as mature tapeworms