Histomoniasis

Question 1

The genus and species of the protozoan that causes Histomoniasis

Answer 1

Histomonas meleagridis

Question 2

The primary organs affected by Histomoniasis in birds

Answer 2

Ceca and liver

Question 3

In which avian species is Histomoniasis typically most fatal?

Answer 3

Turkeys

Question 4

Histomonas meleagridis can exist in which two morphological forms?

Answer 4

Flagellated and amoeboid

Question 5

The most common mode of transmission of Histomonas meleagridis is via the embryonated eggs of which nematode?

Answer 5

Heterakis gallinarum

Question 6

In turkeys, direct transmission of Histomoniasis within a flock occurs via?

Answer 6

Direct cloacal contact and fresh droppings

Question 7

In chickens, outbreaks of Histomoniasis may cause:
a) High mortality and severe liver lesions
b) Low morbidity and mild lesions
c) High morbidity, moderate mortality, and extensive culling
d) No significant clinical signs

Answer 7

High morbidity, moderate mortality, and extensive culling

Question 8

What are the characteristic clinical signs of Histomoniasis in turkeys in later stages?

Answer 8

Listlessness
Reduced appetite
Drooping wings
Unkempt feathers
Yellow droppings

Question 9

The name “blackhead” for Histomoniasis is considered:
a) An accurate description in most cases
b) Obscure and misleading, with few birds showing a cyanotic head
c) Only seen in young birds
d) A result of secondary bacterial infections

Answer 9

Obscure and misleading, with few birds showing a cyanotic head

Question 10

The primary lesions of Histomoniasis are found in?

Answer 10

Ceca

Question 11

Cecal lesions in Histomoniasis are characterized by:

Answer 11

Marked inflammatory changes and ulcerations, causing thickening

Question 12

The appearance of the liver in some cases of Histomoniasis

Answer 12

Green or tan

Question 13

The combination of lesions in which two organs is considered pathognomonic for Histomoniasis?

Answer 13

Ceca and liver

Question 14

To prevent Histomoniasis, contact should be avoided between turkeys and?

Answer 14

Healthy chickens and gamebirds

Question 15

Arthropods such as which insect may serve as mechanical vectors for Histomonas?

Answer 15

Flies

Question 16

Once established in a turkey flock, Histomoniasis spreads rapidly via?

Answer 16

Direct contact

Question 17

What is the typical outcome of Histomonads shed directly into the environment?

Answer 17

Die quickly

Question 18

The immune response of turkeys to live attenuated Histomonas requires how long to develop?

Answer 18

4 weeks

Question 19

Which drug is currently approved for use as prophylaxis (prevention) of Histomoniasis?

Answer 19

Nitarsone

Question 20

What is the required withdrawal period for nitarsone in animals slaughtered for human consumption?

Answer 20

5 days

Question 21

Name at least three diseases that liver lesions of Histomoniasis must be differentiated from.

Answer 21

Tuberculosis
Leukosis
Avian trichomonosis

Question 22

Where are Histomonads released from Heterakis larvae in the bird?

Answer 22

Ceca

Question 23

Histomonads reach the liver primarily via the?

Answer 23

Vascular system or peritoneal cavity

Question 24

For full virulence, Histomonas depends on interaction with other gut organisms such as?

Answer 24

Bacteria and coccidia

Question 25

Infection with Histomonas has not been shown to spread by direct cloacal contact in: a) Turkeys b) Chickens c) Quail d) Pheasants

Answer 25

Chickens

Question 26

In chickens, liver lesions from Histomoniasis often involve?

Answer 26

Secondary bacterial infections

Question 27

Morbidity due to Histomoniasis can be especially high in young: a) Male broilers b) Older laying hens c) Layer or breeder pullets d) Backyard chickens

Answer 27

Layer or breeder pullets

Question 28

Tissue responses to Histomonas infection may resolve in approximately

Answer 28

4 weeks

Question 29

After resolution of tissue lesions, birds may remain carriers of Histomonas for another?

Answer 29

6 weeks

Question 30

Signs of Histomoniasis are typically apparent in turkeys how many days after infection?

Answer 30

7-12 days

Question 31

Young birds with Histomoniasis tend to have a more: a) Chronic disease course b) Mild form of the disease c) Acute disease and die within a few days after signs appear d) Subclinical infection

Answer 31

Acute disease and die within a few days after signs appear

Question 32

In later stages of Histomoniasis in turkeys, the droppings are often described as?

Answer 32

Yellow

Question 33

Occasionally, cecal ulcers in Histomoniasis can erode the cecal wall, leading to ______

Answer 33

Peritonitis

Question 34

Frequent worming of chickens with benzimidazole anthelmintics helps reduce exposure to?

Answer 34

Heterakid worms that carry the infection

Question 35

Historically, which class of drugs, such as ronidazole and ipronidazole, were highly effective against Histomoniasis?

Answer 35

Nitroimidazoles

Question 36

Nitroimidazoles can still be used by veterinary prescription in?

Answer 36

Non-food-producing birds

Question 37

The intermediate host (vector) for Histomonas meleagridis is primarily

Answer 37

An earthworm carrying Heterakis larvae

Question 38

The route of infection for Histomoniasis is typically?

Answer 38

Ingestion of embryonated Heterakis eggs containing Histomonas

Question 39

Other names of Histomoniasis

Answer 39

Blackhead disease Infectious Enterohepatitis

Question 40

Incubation period of Histomonas meleagridis

Answer 40

7-15 days

Question 41

Clinical signs appear how many days post infection?

Answer 41

7 – 12 days

Question 42

The primary lesions of histomoniasis are in the ceca, where parasite migrates into the _____________

Answer 42

submucosa and muscularis mucosae

Question 43

Clinical signs in the ceca are apparent ________ days after H. meleagridis invasion

Answer 43

3-4 days

Question 44

Liver lesions typical and are strongly suggestive of histomoniasis.

Answer 44

Umbilicated lesions or “target” or “bullseye” lesions

Question 45

In turkeys, liver lesions appear _____ days after infection and may be up to 4 cm in diameter and involve the entire organ.

Answer 45

6-8

Question 46

Lesions of blackhead disease are also seen in which organs, aside from ceca and liver?

Answer 46

Kidneys, bursa of Fabricius, spleen, and pancreas.