Helminths (Ascaridida)

Question 1

What are ascarids?

Answer 1

Among the largest and most familiar nematode parasites infecting the intestinal tract of domestic animals

They can range from several inches up to 2 feet in length.

Question 2

How is the mouth of ascarids structured?

Answer 2

Surrounded by three fleshy lips: one dorsal and two subventral

The male tail is usually curved ventrally.

Question 3

What is the significance of the eggshell of ascarids?

Answer 3

Capable of withstanding extremes of harsh environments

Ascarid eggs are remarkably resistant to chemical and physical insults.

Question 4

How do ascaridoids adapt to terrestrial environments?

Answer 4

By changing the typical life history pattern, leading to direct life cycles with or without various migrations

This includes transplacental or transmammary pathways.

Question 5

What is the primary host for Ascaris suum?

Answer 5

Swine

It is considered a distinct species from Ascaris lumbricoides.

Question 6

What happens to the larva of A. suum after hatching?

Answer 6

Migrates extensively through various tissues, entering the liver and lungs

The larva causes both mechanical damage and hypersensitivity reactions.

Question 7

What are the main clinical signs of A. suum infection in pigs?

Answer 7

Severe respiratory distress and diarrhea

Heavily infected pigs fail to make economically profitable gains.

Question 8

What is the role of anthelmintic medication in controlling A. suum?

Answer 8

Used to reduce infection rates, but drugs alone are not sufficient

Hygromycin B, piperazines, and ivermectin are some effective medications.

Question 9

What is the significance of the egg of Parascaris equorum?

Answer 9

Durable and key element in the epidemiology of infection

Eggs accumulate in polluted soils and can adhere to the mare’s udder.

Question 10

What are the effects of heavy P. equorum infection?

Answer 10

Causes moderate enteritis and subnormal growth

The infected individual appears malnourished with dull haircoat and dry skin.

Question 11

How does the life cycle of P. equorum compare to that of Ascaris?

Answer 11

Similar in that larvae migrate through tissues, but they have different epidemiological behaviors

P. equorum can grow up to 2 feet long.

Question 12

What are the challenges in controlling P. equorum?

Answer 12

Eggs are resistant to temperature extremes and most disinfectants

Effective control involves thorough sanitation.

Question 13

Fill in the blank: Ascaris suum is a _______ parasite of swine.

Answer 13

ubiquitous and pathogenic

Question 14

True or False: Ascaris lumbricoides and Ascaris suum can mature in each other’s hosts.

Answer 14

True

However, they typically maintain separate life cycles.

Question 15

What is a common consequence of A. suum larval migration in the lungs?

Answer 15

Mechanical damage leading to eosinophilic inflammation

This can cause respiratory distress and potential death in young pigs.

Question 16

What type of lesions are associated with A. suum infections in pig livers?

Answer 16

Milk spot lesions resulting from fibrosis

These lesions can lead to condemnation during meat inspection.

Question 17

What is the recommended sanitation measure before farrowing?

Answer 17

Treating and cleaning sows with soap and warm water

This reduces contamination for piglets.

Question 18

What is a potential risk when administering anthelmintics to foals with heavy P. equorum burdens?

Answer 18

Impaction or complete obstruction of the bowel

This is due to the paralysis of ascarids.

Question 19

What is the primary method for diagnosing acute ascariasis?

Answer 19

Clinical and necropsy findings

Including discovery of pulmonary hemorrhages and edema.

Question 20

What is the lifespan of ascarid eggs in soil?

Answer 20

Remain infective for many years

This is critical for the epidemiology of ascariasis.

Question 21

What is the recommended cleaning procedure before foaling to control parasites?

Answer 21

Thorough cleaning of the foaling stall and of the mare’s udder and teats is recommended

This helps to prevent contamination by P. equorum eggs, which are highly resistant and can accumulate over time.

Question 22

Name some effective anthelmintic medications against P. equorum.

Answer 22

• Piperazine compounds (100 mg/kg)
• Fenbendazole (10 mg/kg)
• Pyrantel (6.6 mg/kg)
• Ivermectin (0.2 mg/kg)
• Moxidectin (0.4 mg/kg)

Pyrantel tartrate can also prevent ascarid infection when used as a feed additive.

Question 23

True or False: Macrocyclic lactones are effective against P. equorum.

Answer 23

False

Reports indicate that macrocyclic lactones have been ineffective for clearing P. equorum infections in horses.

Question 24

What is the significance of Ann F. Russell’s study on foals?

Answer 24

Her study indicated the natural changes in worm populations in foals over time without modern anthelmintics

It provides a basis for understanding equine parasitology and infection dynamics.

Question 25

At what age do P. equorum eggs first appear in foals?

Answer 25

Around 12 weeks of age ## Footnote This aligns with the prepatent period of the parasite, suggesting infection occurs shortly after birth.

Question 26

What does the curve in Fig. 4.142 represent regarding strongylid egg counts?

Answer 26

It shows a gradual increase in composite strongylid egg counts during the first year of life ## Footnote This increase is primarily due to the predominance of small strongylids.

Question 27

What is Toxascaris leonina?

Answer 27

A parasite of cats and dogs that can be acquired through ingesting infective eggs or paratenic hosts ## Footnote It develops rapidly, usually reaching the infective stage in about one week.

Question 28

What are some hosts for Toxocara species?

Answer 28

* Dogs * Cats * Calves * Elephants * Hippopotami * Bats * Civet cats * Rodents * Coatimundis * Mongooses ## Footnote Toxocara canis and Toxocara cati are the most commonly observed in dogs and cats, respectively.

Question 29

What are the symptoms of heavy Toxocara canis infections in puppies?

Answer 29

* Severe abdominal discomfort * Continuous whimpering and shrieking * Straddle-legged posture when standing or walking * Possible death from intestinal obstruction ## Footnote Immature and adult worms may appear in feces or vomitus.

Question 30

What is the primary mode of transmission of Toxocara canis from mother to pups?

Answer 30

Transplacental transmission ## Footnote Arrested larvae are reactivated during the last trimester and migrate to the pups in utero.

Question 31

Fill in the blank: Toxocara canis larvae may also be found in the tissues of _______.

Answer 31

[paratenic hosts] ## Footnote This includes various animals such as rodents and sheep, and the larvae can remain infective without developing.

Question 32

What does the term 'arrested infective larvae' refer to?

Answer 32

Larvae that remain in a dormant state within the tissues of a host ## Footnote These larvae can be reactivated and migrate to new hosts, contributing to the spread of infection.

Question 33

What is a paratenic host?

Answer 33

A paratenic host is any in which a larval parasite may survive and remain infective for its definitive host without undergoing development ## Footnote Examples include rodents, sheep, pigs, monkeys, humans, earthworms, and adult dogs for Toxocara canis larvae.

Question 34

What is the primary anthelmintic labeled for treating 2-week-old puppies?

Answer 34

Pyrantel pamoate ## Footnote Medication should start as early as the second week of life and be repeated every 2 weeks until the pup is 3 months old.

Question 35

What is the recommended treatment frequency for young puppies infected with Toxocara canis?

Answer 35

Every 2 weeks until the pup is 3 months old

Question 36

At what age can puppies be treated with fenbendazole or ivermectin with pyrantel pamoate?

Answer 36

Older than 6 weeks of age

Question 37

True or False: Transplacental transmission of Toxocara canis is significant in puppies.

Answer 37

True

Question 38

What is the significance of the bitch in the epidemiology of Toxocara canis?

Answer 38

The bitch harbors the majority of the reservoir of infection not contained in the soil

Question 39

What should be done to control Toxocara canis infections in nursing bitches?

Answer 39

Anthelmintic medication and sanitation should be applied effectively and efficiently

Question 40

What does the phrase 'Toxocara canis–free dogs' imply?

Answer 40

Dogs are devoid of both adult and larval parasites

Question 41

What was the outcome of treating bitches with fenbendazole during gestation?

Answer 41

Pups were found free of both Toxocara canis and Ancylostoma caninum

Question 42

What is Toxocara cati?

Answer 42

A parasitic worm slightly smaller than Toxocara canis, affecting cats

Question 43

How does the life history of Toxocara cati differ from Toxocara canis?

Answer 43

Prenatal infection through the placenta does not occur in T. cati

Question 44

What is the role of paratenic hosts in the life cycle of Toxocara cati?

Answer 44

They represent an important reservoir of infection for adult cats

Question 45

What is the primary treatment for kittens under 6 weeks of age?

Answer 45

Pyrantel pamoate

Question 46

Fill in the blank: Toxocara and Toxascaris eggs are highly resistant to _______.

Answer 46

Environmental extremes

Question 47

What is the most effective measure to control Toxocara eggs in the environment?

Answer 47

Entomb them under a concrete or bituminous asphalt slab

Question 48

What is the prevalence of Toxocara eggs in soil samples from public places worldwide?

Answer 48

21%

Question 49

What should be done to clean kennel areas contaminated with Toxocara eggs?

Answer 49

Physically clean all surfaces, then treat with 1% sodium hypochlorite

Question 50

How are ascarid eggs killed?

Answer 50

By heat, specifically by raising the temperature above 60°C (140°F)

Question 51

What is the method used to strip off the outer protein coat of ascarid eggs?

Answer 51

Using sodium hypochlorite after preliminary cleaning ## Footnote Residual organic matter neutralizes sodium hypochlorite, making it ineffective

Question 52

What temperature is required to kill ascarid eggs?

Answer 52

Above 60°C (140°F) for 5 minutes

Question 53

What role do paratenic hosts play in Toxocara and Toxascaris infection?

Answer 53

They may significantly contribute to the epidemiology of the infection

Question 54

What percentage of brown rats examined in a rural England survey were found to have Toxocara larvae?

Answer 54

15%

Question 55

What is visceral larva migrans?

Answer 55

A condition caused by T. canis larvae leading to sustained eosinophilia, pneumonitis, and hepatomegaly

Question 56

What are the typical symptoms of visceral larva migrans in children?

Answer 56

Eosinophilia, pneumonitis, and hepatomegaly

Question 57

What is the typical epidemiologic situation for symptomatic cases of human toxocariasis?

Answer 57

Toddlers eating soil contaminated with infective T. canis eggs

Question 58

What is a significant source of T. canis eggs in urban environments?

Answer 58

Dog feces

Question 59

What is the risk of using dog feces in vegetable gardens?

Answer 59

It must never be used due to potential contamination with T. canis eggs

Question 60

What is the seroprevalence of T. canis infection in a U.S. survey of individuals older than 6 years?

Answer 60

13.9%

Question 61

How can humans become infected with T. canis or T. cati?

Answer 61

By ingesting infective eggs from the environment

Question 62

What is the typical route of infection for larvae in humans after ingestion?

Answer 62

Larvae migrate to the liver and persist for months

Question 63

What type of food is typically associated with human infections of T. canis?

Answer 63

Raw liver

Question 64

What can cause misdiagnosis in cases of granulomatous retinitis in children?

Answer 64

T. canis larvae misdiagnosed as retinoblastoma

Question 65

What species of Toxocara is a threat to cattle and buffalo in the developing world?

Answer 65

Toxocara vitulorum

Question 66

What are the symptoms of T. canis infection in cats?

Answer 66

Elevated eosinophil counts and massive eosinophilic granulomas

Question 67

What is a potential consequence of T. canis infection in pigs?

Answer 67

White-spot disease in the liver

Question 68

What is the common species of Baylisascaris found in North American wildlife?

Answer 68

B. procyonis

Question 69

What serious condition can B. procyonis cause in humans?

Answer 69

Visceral larva migrans

Question 70

What type of migration do B. procyonis larvae undergo that can cause fatal disease?

Answer 70

Neural migration

Question 71

What is the treatment for raccoons infected with B. procyonis?

Answer 71

Anthelmintics active against T. canis

Question 72

What is the size comparison of B. procyonis eggs to T. canis and Trichuris vulpis eggs?

Answer 72

Slightly smaller

Question 73

What is the role of hay, straw, and feedstuffs in the transmission of B. procyonis?

Answer 73

They can be sources of infective eggs

Question 74

True or False: Most cases of Baylisascaris in dogs are reported.

Answer 74

False