parasitology rest of the nematodes Flashcards
T/F? All ascarid parasites of domestic animals have larval migratory phase in host?
False
T/F? The most pathogenic mechanism on ascarid infections is the intestinal mucosal damage caused when parasites attach
False, they dont attach
they are large, compete for space, nutrients
T/F? Unlike hookworms, toxacara canis does not have importance in public health
False
produces
Visceral larva migrans (VLM): larva anywhere
Ocular larva migrans (OLM): in the eye
in humans
Order Spirurida
Filaroidea very long and thin, Could be confused with ascarids
divided into Filaroidea and non filaroidea
Diverse order: difficult to find general characteristics, but all members have an arthropod as intermediate host (indirect life cycle)
Parasitize a variety of tissues in vertebrate host
Superfamily Filaroidea
order spirurida
Called filarids
Not in the GI tract
Long slender worms
Arthropod, usually insect, intermediate host
Females ovoviviparous: produce microfilariae (sing. microfilaria), generally abbreviated “MF”
MF: pre-L1 stage, in other words: a stage between eggs and L1
microfilariae
larvae of filaroidea (spirurida)
MF: pre-L1 stage, in other words: a stage between eggs and L1
Dirofilaria immitis (Heartworm)
filaroidea (spirurida)
Definitive host
Dogs and wild canids
Parasite of pulmonary arteries primarily
* Sometimes in right heart
Long, thin
Females up to 28 cm in length
Dirofilaria immitis - life cycle
heartworm
1. mosquito ingests microfilariae in blood
2. microfilariae mature from L1-L3 in mosquito
3. infective L3 deposited into dog via mosquito bite
4. most L3 mature to L4 in SQ tissue of dog in 1-3 days
5. L4 migrate and mature to sexually immature aduts 50-70 days
6. sexually immature adults migrate to heart and lungs 70 days post infection
7. worms develop sexual maturity in pulm artery
pre patent period 6 months
patency: 5 years
Dirofilaria immitis - Pathogenesis
Damage roughly proportional to worm numbers
* Probably no clinical signs with lower numbers
Disease components
* Some physical obstruction of vessel by worms
* Worms cause inflammation in vessel wall
* Progressive fibrosis in vessel (sclerosis)
Reduced cardiac output and compensatory right heart disease with severe disease
* Right heart enlargement and failure
Potential thromboembolism
Dirofilaria immitis - Clinical Signs
Dirofilaria immitis - Diagnosis
Annual test recommended
Antigen tests: most sensitive and widely used
Microfilaria check
* Check peripheral blood sample for MF
Dirofilaria immitis - Treatment
Preventives recommended because treatment is harsh and accompanied by risk of thromboembolism
Wolbachia
Many, but not all filarid parasites have symbiotic bacteria, Wolbachia
If bacteria is removed, the reproduction of the worms is blocked, reduces severity of disease
Doxycycline now being used in treatment of heartworm infections
Dirofilaria immitis in cats
Worms less successful in cats
More likely to migrate to abnormal sites than in dogs
Most infected cats show no signs
Worms die soon after infection
Filaroidea other than Dirofilaria immitis
Yes, other filarids occur in the US but they are uncommon
Filarid parasites of subQ tissue of dogs
Filarid parasite of horses can cause dermatitis
Long thin nematode not in GI tract + Microfilariae detected= filarid
non filaroidea
order spirurida
Minor species producing eggs that are clear, elliptical shaped with a smooth, thick shell wall containing a coiled larva
Adults small to medium, but not threadlike
Arthropod Intermediate host
Habronema and Draschia spp
Non-Filaroidea (order spirurida)
Live in nodules in equine stomach
Intermediate host: Stable and house fly
L3 can be deposited by mistake in other locations (usually ingested)
* Mucocutaneous junction
* Wounds
* Larvae invade areas and survive but don’t develop
Causes “summer sore”
Persistent cutaneous granuloma
Can be mistaken for exuberant granulation tissue, neoplasia
order enoplida
A few members of importance in domestic animals
Without many common characteristics
Most in domestic animals produce eggs with 2 polar plugs
Infective larva develops and remains inside the egg
Eggs very resistant to environmental conditions
Trichuris vulpis
whipworm, order enoplida
Large intestine of dogs, worldwide
Whip shaped body
Anterior end entwined within layer of epithelial cells
Direct life cycle
Bipolar eggs passed in feces
Infective larva develops in eggs (at lest 2 weeks): embryonated egg is the infective stage
Diagnosis: egg detection
PPP: 3 months – dont see in puppies
Many infections asymptomatic
Clinical disease
* Diarrhea ± blood: Anemia if severe
Symptomatic cases seen in young and adult dogs
One of the big 3 worms of dogs: about 19% of prevalence in national survey
Trichinella
Order Enoplida
Adult worms in small intestine of warm blooded animals
Larvae produced, penetrate gut, encyst in tissues
Important zoonosis from ingestion of pork
Human disease: Trichinellosis or Trichinosis
Order Oxyurida
Pinworms
Usually small adults in large intestine
Species in horses, rodents, ruminants, reptiles, people
Usually not very pathogenic
Direct life cycle
Egg may have polar plug, often flattened appearance on one side
Diagnosis by detection of eggs in feces of perianal swabs
* ONE polar plug
Oxyuris equi
order oxyurida
Common equine pinworm
Life cycle
* Infection from ingestion of eggs
* Fertilized females migrate from Large intestine and rectum onto skin, glue eggs to hairs in perianal area
Causes pruritus, irritation from worm movement and egg glue
“Rat tailed” appearance
Diagnosis by finding eggs on perianal skin
more common in BARN HORSES
human pinworm
order oxyurida
Common parasite especially in children
Transmission entirely person to person
Causes intense pruritus in perianal area
Order Rhabditida
Most members are free living soil nematodes
Only one animal parasite genus: Strongyloides NOT STRONYLIDS
Tiny adults (about 6 mm) in SI
Species specific for ruminants, horse, dog, pig, human
Strongyloides eggs common in manure samples from young ruminants, rare to see disease
