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VTEC.3100 > Nematodes of Dogs, Cats, and Humans > Flashcards

Nematodes of Dogs, Cats, and Humans Flashcards

1
Q

Toxocara cati

A

Common roundworm of small intestine of kittens

Morphology:
Long, white, straight
Cervical alae arrowhead shaped
Males 6 cm long; females 12 cm long

Egg:
Similar to T. canis, but slightly smaller

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2
Q

Toxocara Cati Life Cycle

A

Transmammary transmission
Primary route of infection for kittens

Direct transmission
Ingestion of infective eggs

Ingestion of paratenic hosts

More important in cats, since they are hunters

Transplacental transmission
DOES NOT OCCUR

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3
Q

Toxocara Cati Clinical Signs

A

Usually asymptomatic
No migration when acquired through milk, so pneumonia rare
May cause pot-bellied appearance, dull hair coat, vomiting, diarrhea or constipation
Rarely, intestinal obstruction or rupture

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4
Q

Toxocara Cati diagnosis and control

A

Diagnosis:
Adult worms in feces or vomitus
Eggs on fecal flotation

Control:
Most feline dewormers effective – deworm at 2-3 weeks of age and repeat at least once

Public health significance:
Same as T. canis, but more rare

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5
Q

Toxascaris Leonina

A

Small intestinal roundworm of dogs/cats
Less common

Morphology:
Smaller than T. cati; lancelet shaped cervical alae

Egg:
Oval, shell smooth on outside, pitted on inside
Lighter in color than Toxocara eggs

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6
Q

Toxascaris Leonina (Life cycle and transmission)

A

Under optimal conditions, eggs embryonate and become infective in 1 week. After ingestion, eggs hatch and larvae migrate into the intestinal wall, where 2 molts occur. No other migration occurs.

Ingestion of paratenic hosts OR intermediate hosts (because a larval molt occurs in them – to L3).
IHs include mice, rabbits and chickens

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7
Q

Toxascaris Leonina (Clinical Signs)

A

Least pathogenic ascarid
Usually no clinical signs
Severely infected may show abdominal pain, vomiting, diarrhea, and occasional death.

Dogs and cats do not develop immunity; therefore, may find adult worms in adult pets.

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8
Q

Toxascaris Leonina (Diagnosis and control)

A

Diagnosis:
Eggs in feces
Worms in feces or vomitus

Control:
Same as for Toxocara sp.

Public Health Significance:
None

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9
Q

Ascaris lumbricoides

A

Largest nematode parasitizing human intestine
Associated with poor socioeconomic conditions
Approximately 25% world’s population infected
Low mortality, but causes about 20,000 deaths/year worldwide

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10
Q

Ascaris Lubricoides (morphology)

A

Morphology:
Typical ascarid
Females up to 50 cm long; males up to 30 cm
Tail of male coils ventrally
Male has a pair of short, curved, distally pointed spicules

Eggs:
Ovoid, thick mamillated shell
Female may lay 200,000 eggs/day – up to 73,000,000 during its lifetime

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11
Q

Ascaris Lumbricoides (clinical signs)

A

Pulmonary signs vary from slight cough to severe pneumonia
May emerge spontaneously from mouth, nose, or anus
May obstruct bile or pancreatic duct
Interfere with host absorption of nutrients
Acute abdominal problems, such as perforated intestinal wall or intestinal obstruction
Allergic reactions result in facial edema, conjunctivitis, and occasionally severe asthma

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12
Q

Hookworm Genuses

A

Ancylostoma, Ucinaria, Necator

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13
Q

Hookworm morphology

A

Morphology
Reddish brown, 6-20 mm long
Females larger; males have bursa
Teeth or cutting plates on ventral rim of mouth opening – up to 4 pairs

Eggs
Oval, thin-shelled, segmented
Release L1 larvae in 24-48 hours
Uncinaria & A. braziliense eggs larger

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14
Q

Hookworm Life Cycle

A

Life Cycle – Routes of Infection

Direct – Ingestion of free-living L3
Develop in small intestine – usually no migration

Percutaneous
Penetrate the skin and migrate through the circulatory system into the lungs, trachea, esophagus, stomach, and small intestine, where they mature
Some larvae encyst in skeletal muscle in dormant stage (hypobiotic larvae)

Transplacental

Transmammary
Via milk for 1st 3 weeks lactation
Primary route for puppies

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15
Q

Hookworm Clinical Signs

A

Bloodsuckers
Take in small plug intestinal mucosa/capillaries
Secrete an anticoagulant
Blood passes thru worms during feeding & is wasted
Feeding sites continue to bleed after worm moves to another site
Signs are related to anemia that develops
Prenatally infected pups – high mortality rate at 2.5 - 4 weeks
Older pups/dogs – poor doers; dark, tarry diarrhea, pale mucous membranes, etc.

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16
Q

Hookworm Control

A

<u>Therapy</u>
Deworming at 2, 4, 6 weeks of age or more often if necessary
Blood transfusion if blood loss severe

<u>Diagnosis</u>
Clinical signs
Eggs in feces

<u>Control</u>
Preventatives
Drying, direct sunlight kill L3s
Dirt pens get heavily contaminated

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17
Q

Hookworms for humans

A

Public health significance
Pet hookworms, especially A. braziliense, cause cutaneous larval migrans in people – called “ground itch.” L3 larvae penetrate skin, but do not develop further

Human hookworms
Hundreds of millions infected
Daily blood loss estimated = total blood volume of 1,500,000 people

Route of infection percutaneous

Control: health education, sanitary latrines, wearing of shoes, and dewormer treatment

18
Q

Whipworms

A

Dogs: Trichuris vulpis
Cats: very rare
Humans: Trichuris trichuria

Morphology:
45-75 mm long
Long, thin anterior end; short, thick posterior end
Males have tightly coiled tails with one long, slender spicule enclosed in a sheath
Anterior end has a small sharp point to penetrate mucosa

19
Q

Whipworm life cycle

A

Direct: Eggs become infective in about 2 weeks under ideal conditions  ingested by host  larvae emerge through operculae  mature in intestine  adults live in cecum (appendix) or colon (large intestine)
Prepatent period approximately 3 months

20
Q

Whipworm diagnosis

A

Diagnosis:
Eggs on fecal flotation
Often requires serial fecal exams – eggs shed intermittently

Clinical signs
Usually mild
Diarrhea (often greenish), emaciation, dehydration, anemia, and occasionally death may be seen in young
In older dogs, intermittent greenish diarrhea with occasional mucus or fresh blood is the most common sign
Rarely rectal prolapse, esp. in humans

21
Q

Threadworms

A

Strongyloides stercoralis
humans, dogs, cats, foxes
Strongyloides tumefaciens
cats

Morphology:
2 mm long
Only females are parasites of small intestines

Eggs:
Small, embryonated
S. stercoralis eggs

22
Q

Threadworm Life Cycle

A

Life Cycle
L1 larvae may
Develop into infective L3s
Develop into non-parasitic male and female free-living nematodes that produce infective larvae

Therefore, “facultative” parasites
Transmission is percutaneous – L3 enters skin  circulation  lung (L4)  trachea  gut (L5); also occasionally oral ingestion of L3s with same migratory route
Young animals – larvae stored in tissue adjacent to mammary glands activated during gestation  milk

23
Q

Threadworm clinical signs

A

Most often seen in tropics, where is a disease of kenneled dogs
Enteritis
GI hemorrhage
Diarrhea
Pruritus from skin penetration
Verminous pneumonia from migration
Diagnosis
L1 larvae in direct smears or flotation for S. stercoralis
Embryonated eggs in fecal exams for S. tumefaciens

24
Q

Threadworm control

A

Control
Larvae susceptible to drying
If possible, clean kennel, vacate, and leave dry for 3 weeks

Public health significance – human infections
Varies from asymptomatic carriers to fatal disseminated infection in immunosuppressed persons, such as those with AIDS; causes “swollen baby (belly) syndrome“ in New Guinea – fatal unless rapidly treated

25
Q

Capillaria aerophila

A

Lundworm
Capillaria aerophila
Found in trachea, bronchi, and nasal passages of dogs, cats, and foxes. Is rare.

Egg
Double-plugged (operculated), resembling Trichuris, but is smaller; usually asymmetric

Life Cycle
Direct transmission by ingestion of infective L3 eggs  adults in trachea and lungs

Clinical Signs
Uncommon; may cause chronic, harsh cough

26
Q

Filaroides osleri and F. hirthi

A

Lungworm

Rare in U.S. - Found in trachea, bronchi and lung parenchyma in fibrous nodules up to 2 cm in diameter, usually around tracheal bifurcation

Life Cycle
L1 larvae passed in saliva or feces – is directly infective to others by ingestion of feces or lung tissue, or from an infected bitch grooming her puppies

Diagnosis
Larvae in sputum or feces
Bronchoscopic examination for nodule formation at the bifurcation of the trachea

Clinical signs
May cause tracheobronchitis, dyspnea, and coughing in young puppies
Control
Isolate and hand-rear pups
Difficult to eradicate
27
Q

Aelurostrongylus abstrusus

A

Cat lungworm; several cases seen in Louisiana
Site
Lung parenchyma and small bronchioles
Life cycle
Indirect – Female lays eggs in lung tissue  L1 larvae (kinked tails) in trachea  swallowed and passed in feces  Ingested by mollusk  possible paratenic host  cat ingests mollusk or paratenic host  worms develop into adult in cat
Clinical signs
Rare; severe infections may cause respiratory difficulty and possible death

28
Q

Capillaria plica (dogs) ; C. feliscati (cats)

A

Bladder worm – usually no clinical signs

Morphology
15 – 60 mm long

Egg
Bipolar; resembles C. aerophila egg

Life Cycle
Indirect – Earthworms are IH
Diagnosis
Bipolar eggs in urine sediment

29
Q

Dioctophyma renale

A

Kidney worm; largest known nematode
Final hosts
Dogs, various wild animals (mink) in temperate, cold areas
Site of infection
Kidney parenchyma
Morphology
Red color; females up to 103 cm long; males up to 35 cm

Egg
Barrel shaped with operculae at both poles; mamillated

30
Q

Dioctophyma renale

life cycle

A

Eggs to water environment in FH urine  annelid (Lumbriculus variegatus)  2 molts  FH infected by ingestion of annelid or paratenic host  L3 migrates to liver  kidney (right kidney more commonly infected because of location adjacent to liver)
Pathology
Eventually occupies entire kidney, leaving only a sac (renal capsule); 2 – 3 worms/ kidney; infection is not patent (producing eggs) unless both sexes are present in same kidney

31
Q

Spirocerca lupi

A

Esophageal Worm
Final hosts
Dogs, wild canids, wild felids

Morphology
Females up to 80 mm; males up to 54 mm long; coiled and reddish in color when fresh

Egg
Small, thick-shelled; embryonated; parallel sides – “paper clip” egg

32
Q

Spirocerca lupi (life cycle)

A

Live in large (up to golf ball size) fibrous nodules in wall of esophagus and stomach (up to 40 worms/nodule)  small fistulae to lumen of gut  eggs pass through fistulae  out in feces  ingested by IH (beetles)  develop to L3  FH infected by ingestion of IH or paratenic host  L3 released in FH stomach  circulation  aorta, where remain about 3 months  then pass through wall to adjacent esophagus  form nodules

33
Q

Spirocerca Lupi (pathology and diagnosis)

A

pathology

Malignant esophageal sarcomas – very close association
Hypertrophic pulmonary osteoarthropathy – incomplete association – thickening of the bones of the extremities

Diagnosis
Eggs on fecal exam – shed intermittently
Radiograph after barium swallow
Endoscopy

34
Q

Physaloptera rara (dogs) & P. preputialis (cats)

A

Stomach worms

Morphology
Similar in size to ascarids; C-shaped

Egg
Small, thick-shelled, embryonated
Life cycle
Indirect – IH beetles, cockroaches, crickets, etc.

Pathology
Attaches to stomach wall; causes ulceration, gastritis, some blood loss

Diagnosis
Eggs in feces

35
Q

Enterobius vermicularis

A

Pinworm of humans
Morphology
Males 2-5 mm long; females 8-13 mm long, light yellowish-white, thin sharply pointed tail

Site of infection
Cecum (appendix) and surrounding small and large intestine; female migrates to anus to lay her eggs

36
Q

Pinworm transmission

A

Reinfection by contamination of hands  ingestion of infective eggs
Contaminated clothing, bedding, etc.
Airborne – eggs survive several days in dry dust; several weeks in high humidity and moderate temperatures
Retroinfection thought possible (eggs hatch and larvae migrate back into rectum)

37
Q

Pinworm symptoms and treatment

A 
Symptoms
None in the majority of those affected
Anal pruritus
Young girls  may invade vagina  local irritation
May interfere with sleep

Treatment
Anthelmintics, such as pyrantel pamoate
Strict sanitation

38
Q

Wuchereria bancrofti

A

Filarial Worms
Morphology
Like heartworms, but smaller (up to 10 cm long)

Site of infection
Major lymphatic ducts, coiled in nodular masses – in afferent lymphatic vessels

Life cycle
Similar to heartworms – prepatent period 6-12 mo.

39
Q

Wuchereria Bancrofti (diagnosis and treatment)

A

Diagnosis

Microfilariae (L1) in blood
Some cases occult

Treatment
Avermectins
Prevention
Preventing mosquito bites

40
Q

Onchocerca sp.

A

Africa/South America
Similar to W. bancrofti
IH – Blackfly

Pathology
Onchocercomas
Dermatitis/depigmentation
Sclerosing keratitis  blindness
Dwarfism

Diagnosis
Microfilariae in skin snips

VTEC.3100 (20 decks)

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