Superfamily Ancylostomoidea

Question 1

Strongylid-type eggs

Answer 1

• Eggs all look similar
• -Thin-walled
• -Ellipsoid
• -Contain an embryo in the morula stage of development (multicellular)
• -SF Ancylostomoidea (dogs and cats - hookworm)
• -SF Trichostrongyloidea (ruminants - trichostrongyle-type eggs)
• -SF Strongyloidea (equids - strongyle-type eggs)

Question 2

Superfamily Ancylostomoidea

Answer 2

=Hookworms

• “Plug-feeders” or “Blood-suckers”
• Ancylo = curved, stoma = mouth
• Anterior end is bent dorsally
• Large buccal capsule
• Presence of teeth or cutting plates
• Some are zoonotic
• Located in the small intestinal lumen
• Small worms ~1-1.5 cm long
• Male worms have spicules and bursae
• Ancylostoma caninum (dogs)
• –Three pairs of teeth
• Ancylostoma tubaeforme (cats)
• –Three pairs of teeth
• Ancylostoma braziliense (dogs and cats)
• Uncinaria stenocephala (foxes, dogs, and cats)
• Ruminants, wild canids, humans, pinnipeds, etc. have hookworms too

Question 3

Hookworm eggs

Answer 3

-Key differentiating factor is the egg size

Ancylostoma spp.

• 56-75 x 34-47 um
• Ellipsoidal
• Colorless
• Thin-shelled
• Smooth
• 4-8 cell stage (morula) when passed in the feces

Unicinaria stenocephala

• 72-93 x 37-55 um
• Ellipsoidal
• Colorless
• Thin-shelled
• Smooth
• 4-8 cell stage (morula) when passed in the feces

Question 4

Ancylostoma spp.

Answer 4

• Adults have teeth in buccal capsule
• Blood loss in the host occurs in large quantities
• Worms are dark red
• Prepatent period is variable (~2-4 weeks)
• Transmission by oral ingestion, skin penetration, paratenic host, transmammary (A. caninum in dogs)

Question 5

Uncinaria stenocephala

Answer 5

• Adults have cutting plates in buccal capsule
• Very little blood loss in the host
• Worms are pale
• Prepatent period is 15 days
• Transmission by oral ingestion with direct development in the intestine

Question 6

Ancylostoma spp. life-cycle

Answer 6

• Adults are found in the small intestine
• Eggs, when laid, have a morula inside
• Rapid larval development to L1 in the egg within a week
• L1 hatch and develop into L3 in the environment (infective stage) (usually within 2-10 days)
• L3 survive well in moist, shaded, slightly sandy loam soils; dirt runs (sometimes picked up by humans on the beach)
• Eggs and larvae are killed by freezing and desiccation

Question 7

Ancylostoma spp. routes of transmission

Answer 7

• Ingestion of L3 in the environment
• Skin penetration by L3
• Transmammary (occurs only in A. caninum) - important route for infection of puppies
• Paratenic host
• -PPP ~2-4 weeks

Question 8

A. caninum puppies less than three months of age

Answer 8

• Oral ingestion
• -Most develop directly in the small intestine
• -Some undergo pulmonary tracheal migration
• Skin penetration
• -Pulmonary tracheal migration prior to maturation in small intestine
• Transmammary and paratenic host
• -No migration, direct development of adult in the small intestine

Question 9

A. caninum puppies greater than three months of age

Answer 9

• Oral ingestion and/or skin penetration
• -Large proportion of L3 larvae undergo somatic migration and become arrested in tissues
• –Reactivated at pregnancy
• –Some larvae enter the small intestine to mature
• Transmammary and paratenic host
• -No migration, direct development of adult in the small intestine

Question 10

A. caninum life-cycle

Answer 10

• Larval leak phenomenon (always occurs)
• -Reactivation of arrested L3 in intestinal wall and skeletal muscles
• -Cues:
• –Clearance of adults via deworming
• –Last two weeks of pregnancy
• -Low-level, continuous activation, of arrested L3 larvae in the tissues
• -Migrate in the tissues
• -An important phenomenon as it leads to continuous, life-long reinfections of dogs

Question 11

A. caninum pathology/clinical disease

Answer 11

• Main pathogenesis is due to blood feeding
• Adult dogs - common infection with minimal overt disease
• Puppies - anemia
• Four forms of clinical disease:
• -Peracute - neonatal puppies
• -Acute - older puppies and mature dogs
• -Chronic (compensated)
• -Secondary (decompensated)

Question 12

A. caninum peracute disease

Answer 12

• In nursing pups (transmammary infection)
• Severe blood loss, sudden deterioration, dark-tarry feces (soft/liquid) - digested blood (coming from small intestine)
• 50-100 adult worms may be fatal
• Prepatent disease
• Eggs will not be found in the feces

Question 13

A. caninum acute disease

Answer 13

• In older pups and dogs with heavy infections
• Patent with high egg shedding
• Weakness, lethargy, pale mucus membranes, rough hair coat, soft to liquid, dark, tarry feces (melena)
• Acute normocytic-normochromic anemia, followed by hypochromic-microcytic “iron deficiency” anemia (body trying to compensate with reserves)
• Necropsy: multifocal hemorrhagic enteritis, pale internal organs, watery blood, edema, ascites

Question 14

A. caninum chronic disease

Answer 14

• Compensated
• Occurs without signs
• Chronic ill health (weakness, emaciation, anemia)
• Diagnosis: hookworm eggs in feces, reduced PCV, reduced erythrocyte count and blood hemoglobin

Question 15

A. caninum secondary disease

Answer 15

• Decompensated
• Older animals with malnutrition or other debilitating disease and secondary hookworm disease
• Edema; production of anticoagulants, proteases
• -The wound leaks and takes a long time to heal due to anticoagulants

Question 16

A. caninum diagnosis

Answer 16

• Dark tarry feces (formed/liquid)
• Pale mucus membranes - anemia
• Fecal flotation
• -Easy to find thin-walled, oval, morulated eggs

Question 17

A. caninum control

Answer 17

• Scoop poop
• -L3 can develop in one week
• -Larvae survive weeks/months
• Freezing and sunshine/desiccation kill L3

Question 18

Ancylostoma spp. treatment

Answer 18

• Dogs: pyrantel pamoate, febantel, fenbendazole, moxidectin, milbemycin oxime
• Cats: ivermectin, selamectin, moxidectin, milbemycin oxime, pyrantel pamoate, emodepside, febantel
• Anthelmintic treatment must be combined with supportive therapy
• -Keep patient warm, electrolyte and fluid therapy, iron supplements, high protein diet, and when clinically indicated, blood transfusions
• Post-treatment fecal examination (~4 weeks later)
• Remember the “larval leak” phenomenon (if subclinical, then its not as concerning)

Question 19

Multidrug resistant canine hookworms in the US

Answer 19

• Examination of fecal samples between 2012-2018: steady yearly increase in prevalence (~47%)
• Challenge: determine “larval leak” v. “true drug resistance”
• Benzimidazoles (eg. fenbendazole, febantel), tetrahydropyrimidines (eg. pyrantel pamoate), and macrocyclic lactones (eg. milbemycin oxime, moxidectin)
• -Single drug resistance
• -Multi drug resistance
• Combination of Emodepside and praziquantel may work (use with caution); extra-label for dogs
• Need to make sure only medicating if necessary to avoid drug resistance
• Greyhound breeding farms and racing kennels
• -Long term intensive use of drugs
• -Sand and dirt runs
• -Recently adopted retired greyhounds
• –Risk to general canine population
• –Zoonoses: threat to human health
• Methods used to determine anthelminthic resistance
• -Egg hatch assays (EHA)
• -Larval development assays (LDA)
• -Fecal egg counts
• -Deep amplicon sequencing technology (SNP detection)

Question 20

Hookworm zoonosis

Answer 20

• “Creeping eruption” - cutaneous larval migrans
• -Linear, tortuous, erythematous, intensely pruritic eruptions on skin
• -Ancylostoma braziliense larvae (dogs and cats)
• -Consider epidemiology
• “Eosinophilic enteritis”
• -Abdominal pain (+/- eosinophilia)
• -Ancylostoma caninum (dogs)