Hookworms 2 Flashcards by YouWillGet Avirus

Which conditions are most favorable for survival of A. caninum larvae?

Above freezing

Below 37 celcius

Clinical cases are most common in warm weather

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How would you describe the eggs of A. caninum in fresh feces?

Oviparous (morula present)

Typical strongyle-type egg

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Which stage of A. caninum is infective?

How long does it take for this stage to develop?

Sheathed L3

Egg to L3 takes 2-8 days

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What is the prepatent period of A. caninum?

Swallowing: 16 days

Skin penetration: 30 days

Transmammary infection: 10-12 days

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List the modes of infection for A. caninum

Ingestion of L3 in paratenic host

Skin penetration by L3

Transmammary

Transplacental (considered unimportant)

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List the most likely migration pathway for Ancylostoma L3 based on the various modes of infection.

Skin penetration

blood-lung migration
- trachea, coughed up, swallowed
- somatic migration, hypobiotic larvae

Ingestion

mucosal migration
- emerge as adults in the gut lumen

Lactogenic

direct development to adult in gut (has already undergone migration in the mother)

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For what time period can Ancylostoma larvae be detected in the milk of a lactating female?

20 days post-whelping

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Where do hypobiotic Ancylostoma larvae live in the host?

Muscles (from somatic migration)

Small intestine mucosa

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Define “larval leak” as applied to Ancylostoma infections

In persistent infections, hypobiotic larvae are continually reactivated and find their way to the small intestinal lumen.

If the lumen is populated by adults, the larvae will probably pass in the feces.
If no hookworms are present, they will develop into adults.
If adult hookworms are killed by an anthelmintic, the larvae can quickly repopulate the gut.

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Describe the pathogenesis of hookworm infections.

Blood sucking activity

Attach to a mucosal plug and macerate with teeth
Secrete proteolytic enzymes and anticoagulant
Lesions continue to bleed after worms move to new sites

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When you see a puppy with severe anemia, what should your first differential be?

Hookworm infection

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Describe the anemia that results from hookworm infections

Initially normocytic normochromic

Progresses to microcytic hypochromic over time due to iron deficiency

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Describe the factors that influence the severity of hookworm infections.

Dosage of infecting L3’s

Age of host, immunity of host

Iron reserves (low in puppies)

Nutritional status

Stress factors, infections

Position of Jupiter. What you had for breakfast that morning. [JUST KIDDING PLEASE DON’T KILL ME JOSE]

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List the clinical signs associated with canine hookworm infection.

Anemia

pale mucous membranes, decreased stamina, increased CRT

Melena

Unthrifty appearance

Respiratory signs, pneumonia

Larval migration through lungs

Dermatitis, usually interdigital

Inflammation as a reaction to L3 skin penetration

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List the 4 clinical syndromes of canine hookworm disease

Peracute neonatal ancylostomiasis

Acute ancylostomiasis

Compensated ancylostomiasis

Decompensated ancylostomiasis

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Describe peracute ancylostomiasis

Result of lactogenic transmission from the dam

50-100 adults can be fatal
Signs
- appear healthy first week, crash by second week
Worms suck blood as immature adults (may not see eggs)
Often fatal by 10-24 days of age

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In the case of a peracute Ancylostoma infection, when will adults begin to lay eggs?

16 days (prepatent period)

THIS IS IMPORTANT

Puppies may be showing severe clinical signs (anemia, diarrhea, severe weakness), but you may not be able to detect eggs.

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Describe acute ancylostomiasis

Older pups acquires a large number of L3 in a short period of time.

Signs: normocytic, normochromic anemia, melena, weakness.

Will see strongyle-type eggs in feces.

Will often die unless promptly treated.

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Describe compensated ancylostomiasis

Chronic condition

Mature dogs with low number of hookworms

Asymptomatic unless stressed

Low to moderate numbers of strongyle-type eggs in feces

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Describe decompensated ancylostomiasis

Occurs in mature, usually malnourished dogs
Moderate number of eggs + many worms
Will see melena, and may develop diarrhea
Thin, rough hair coat
Can be fatal

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What are the lesions associated with LARVAL hookworms?

Skin penetration
- erythematous papular or vesicular skin rash
Tracheal migration
- petechial to ecchymotic hemorrhages in the lungs

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What are the symptoms associated with ADULT hookworms?

Multifocal hemorrhagic enteritis

Generalized pallor

What is the ONLY basis for antemortem diagnosis of peracute neonatal ancylostomiasis?

Signalment and clinical signs

Recall that in peracute infections, the patient will not yet be shedding eggs. Prompt treatment is important, or the patient may die.

Describe the treatment for peracute neonatal ancylostomiasis.

Anthelmintics

Supportive care, including blood transfusions and CO2.

Poor prognosis.

Describe the treatment for decompensated ancylostomiasis.

Anthelmintics Nutritional support

Which anthelmintics are most effective against ADULT hookworms?

Benzimidazoles Macrocyclic lactones Nicotinic agonists \*these have poor efficacy against hypobiotic larvae

How do you prevent and control hookworms?

* Identify and treat infected dogs * Sanitation: remove feces daily * Avoid keeping dogs on gravel, sand grass, and damp shady areas * Kill larvae in the environment

How can you kill hookworm larvae in the environment?

Spray kennels and runs with 1% bleach Apply sodium borate to grass (note: this will also kill the grass) L3 killed by hard frosts

Describe the drug regimen for a bitch to prevent lactogenic transmission of larvae to her pups.

* Fenbendazole 50mg/kg/day * From 40 days of gestation to 14 days of lactation * Ivermectin 0.5mg/kg * Once 4-9 days before whelping, again 10 days later

Where is *Uncinaria stenocephala* found in the US?

Northern US L3 not killed by freezing

Describe the buccal capsule of *Uncinaria*

Has cutting plates instead of teeth.

Does *Uncinaria* undergo somatic migration?

No evidence for this. Mucosal migration only.

What is the host species of *Ancylostoma tubaeforme*?

Cats

Name the modes of transmission for *Ancylostoma tubaeforme*

Ingestion of L3 Ingestion of paratenic host with L3 Skin penetration by L3 \*No transmammary or transplacental transmission

What are the clinical signs associated with *Ancylostoma tubaeforme*?

Clinical signs uncommon Kittens more likely to show symptoms Regenerative anemia, weight loss, diarrhea

Identify these species

From left to right: *Ancylostoma caninum* (dogs), *Ancylostoma braziliense* (dogs), *Ancylostoma tubaeforme* (cats), *Uncinaria stenocephala* (dogs and cats)

Name the drugs used to treat feline hookworm infection

Febantel Selamectin Milbemycin Pyrantel

What is the primary host of *Bunostomum phlebotomum*?

Cattle

What is the primary host of *Bunostomum trigonocephalum*?

Sheep and goats

Where are *Bunostomum* worms most common? Which mode of infection is most common?

Most common in Southern US. Prefer warm, moist climates.

What is the prepatent period of *Bunostomum*?

4-8 weeks

Describe the path of a *Bunostomum* larva once it penetrates the skin.

Skin penetration - blood stream - lung - trachea - small intestine

Identify this species.

*Bunostomum* sp. Note how the morula nearly completely fills the shell.

Describe the clinical signs associated with *Bunostomum* infection.

* Pruritis and alopecia at L3 entry sites * Progressive iron deficiency anemia * Hypoproteinemia * leads to edema * Anorexia, weight loss, poor growth * Fetid diarrhea, possibly with blood

Describe this condition in this calf.

Bottle jaw This is the result of hypoproteinemia from *Bunostomum* infection. *Haemonchus* is not the only worm that can cause bottle jaw!

How would you DEFINITIVELY diagnose a *Bunostomum* infection?

ID adults at necropsy Culture feces to ID L3

What drugs can you use to treat *Bunostomum* infections?

Benzimidazoles Ivermectin Levamisole

What are the diseases associated with animal hookworms penetrating human skin?

Cutaneous larva migrans Follicular dermatitis Eosinophilic pneumonitis Local myositis Eosinophilic enteritis

Describe cutaneous larva migrans

Animal hookworm L3 penetrates human skin Larva tries to complete its life cycle, but cannot. Cannot penetrate deeper tissues. Larva wanders, tunnels, and produces ridges on the skin.

Which species can cause cutaneous larva migrans (CLM)?

* Ancylostoma* spp. * Uncinaria* * Bunostomum* * Strongyloides* * Hypoderma* (cattle grubs) * Gasterophilus* (stomach bots)

Describe this lesion.

Cutaneous larva migrans (CLM) Lesions are erythematous and intensely pruritic. Can persist for weeks to months. Secondary bacterial infections common. Lesions more severe is person is hypersensitized by prior exposure.

The highest incidences of CLM cases in the U.S. coincide with which hookworm species?

*Ancylostoma braziliense*

Name the two human hookworms

* Ancylostoma duodenale* * Necator americanus* (85% of infections)

Suppose you developed a vaccine against an enzyme that a hookworm uses to digest hemoglobin. Your vaccine causes the host to produce IgG against the antigen. Would it be an effective vaccine?

YES. Hookworms are blood feeders and take in blood proteins with their meals, including IgG. (Don't assume that because hookworms live at mucosal surfaces, only IgA would be effective)