Helminths (Trichostrongyloidea) Flashcards
Parasite host and predilection sites (171 cards)
1
Q
What is the maximum length of Trichostrongylus worms?
A
Less than 7 mm long
2
Q
What type of parasites are Trichostrongylus axei?
A
Parasites of the simple stomach or abomasum
3
Q
Which hosts are commonly affected by Trichostrongylus axei?
A
Ruminants, horses, and leporids
4
Q
What is a key characteristic of Trichostrongylus spp. that makes them hard to detect?
A
They are very small and can be overlooked on necropsy
5
Q
How can one improve the detection of Trichostrongylus during necropsy?
A
By examining washings or scrapings of the stomach and small intestine with a hand lens or stereoscopic microscope
6
Q
Which other genera are Trichostrongylus spp. likely to be confused with?
A
Strongyloides spp. and smaller species of Cooperia
7
Q
What is the life stage of Trichostrongylus that survives winter on pasture?
A
Infective third-stage larvae
8
Q
When are ruminants typically exposed to Trichostrongylus infection?
A
When turned out to pasture in spring
9
Q
What happens to the overwintering generation of Trichostrongylus larvae as the weather warms?
A
They die off
10
Q
What condition can result from a heavy infection of Trichostrongylus?
A
Protracted and debilitating watery diarrhea
11
Q
What color does the feces become in cases of severe Trichostrongylus infection?
A
Watery and dark green (‘black scours’)
12
Q
What are ‘dingleberries’ in the context of Trichostrongylus infections?
A
Pea- to egg-sized masses of feces that accumulate in the fleece
13
Q
What is the typical egg count for Trichostrongylus infections?
A
Rarely exceeds 5000 eggs per gram
14
Q
What is a common consequence of protracted diarrhea caused by Trichostrongylus?
A
Weakness and emaciation
15
Q
True or False: Trichostrongylus infections always cause serious illness in well-nourished ruminants.
A
False
16
Q
What should be considered when identifying the causes of Trichostrongylus outbreaks?
A
The quality of the environment and animal husbandry
17
Q
What are the two genera of parasites that are indistinguishable by certain criteria?
A
Ostertagia and Teladorsagia
18
Q
Which host animals are affected by Teladorsagia circumcincta?
A
Sheep and goats
19
Q
Which host animals are affected by Ostertagia ostertagi?
A
Cattle
20
Q
What is the typical length and color of Ostertagia and Teladorsagia parasites?
A
Less than 14 mm long and brownish in color
21
Q
Where are Ostertagia and Teladorsagia parasites found in ruminants?
A
In the abomasum
22
Q
What is a characteristic feature of the mature female’s tail of these parasites?
A
Usually annulated
23
Q
What type of eggs do Ostertagia and Teladorsagia produce?
A
Typical strongylid eggs
24
Q
What is the role of the vulvar flap in female Ostertagia and Teladorsagia?
A
It guards the vulva
25
How do Ostertagia and Teladorsagia larvae overwinter?
By resembling Trichostrongylus larvae
26
What does 'Type I' or 'summer' ostertagiosis refer to?
Worms maturing without first passing through a developmental arrest
27
What is 'Type II' or 'winter' ostertagiosis associated with?
Larvae that have remained in arrested development becoming metabolically active
28
What disease does O. ostertagi cause in young cattle?
Chronic abomasitis
29
What are common clinical signs of chronic abomasitis caused by O. ostertagi?
Profuse watery diarrhea, anemia, hypoproteinemia, submandibular edema
30
What appearance does the abomasal mucosa have in cases of O. ostertagi infection?
Morocco leather appearance
31
What does necropsy reveal in cattle infected with O. ostertagi?
Wasted carcass with depletion of fat deposits
32
What is the economic impact of O. ostertagi on cattle?
Young cattle waste away and die or fail to achieve growth potential
33
True or False: Teladorsagia spp. only cause disease in cattle.
False
34
Fill in the blank: The hydrogen ion concentration of the gastric juice in O. ostertagi infection approaches _______.
neutrality
35
What is the maximum length of Haemonchus spp. parasites?
Up to 30 mm in length
36
Which species of Haemonchus are found in the United States?
* Haemonchus contortus
* Haemonchus placei
* Haemonchus similis
37
What distinctive feature does the male Haemonchus have?
An asymmetric dorsal ray in its bursa and short, wedge-shaped spicules
38
What is the 'barber pole appearance' in female Haemonchus?
The egg-filled uterus spirals around the blood-filled gut
39
What is the characteristic sign of haemonchosis?
Pallor of the skin and mucous membranes
40
What hematocrit reading indicates a grave prognosis in haemonchosis?
Less than 15%
41
What chart is used to measure anemia due to haemonchosis in sheep and goats?
FAMACHA chart
42
What is a common external manifestation of plasma protein loss in haemonchosis?
Submaxillary edema (bottle jaw)
43
What can happen if blood loss exceeds the host's hematopoietic capacity?
Progressive anemia leading to death
44
What species are Mecistocirrus spp. parasites of?
Abomasum of ruminants and stomach of pigs
45
How do Mecistocirrus spp. differ morphologically from Haemonchus spp.?
Vulva is close to the anus and spicules are long and thin
46
What is the maximum length of Cooperia spp. parasites?
Less than 9 mm long
47
What characteristic features are found in the cuticle of Cooperia spp.?
Transversely striated and slightly inflated
48
What is the relationship of Cooperia spp. to disease production?
Similar to Trichostrongylus spp.
49
What was observed in a study comparing infected and uninfected calves with *Cooperia punctata*?
Uninfected calves gained weight 7.4% more rapidly
50
Which species of Nematodirus can grow to a length of 25 mm?
*Nematodirus battus.*
51
What is unique about the life history of Nematodirus spp.?
Larva develops to the infective third stage within the eggshell
52
What environmental condition is needed for Nematodirus battus larvae to hatch?
Freezing followed by warmer weather
53
What is a specific strongylosis caused by Nematodirus battus characterized by?
Severe and debilitating diarrhea
54
What is the average egg count per gram of feces for Nematodirus battus?
600 eggs, rarely exceeding 3000 eggs
55
What significant worm count is considered for Nematodirus battus?
10,000 worms
56
In which state was Nematodirus battus first identified in the United States?
Oregon in 1985
57
What is the scientific name of the parasite that affects the stomach of swine?
Hyostrongylus rubidus
## Footnote
Hyostrongylus kigeziensis is a parasite of the mountain gorilla.
58
What are the key identifying features of Hyostrongylus rubidus?
Less than 9 mm long, small annular buccal collar, short spicules with two points, long narrow gubernaculum.
59
What type of nematode is H. rubidus?
Trichostrongyloid nematode.
60
What is the habitat of H. rubidus?
Stomach of swine.
61
What type of eggs does H. rubidus produce?
Typical strongylid eggs.
62
What is the significance of ensheathed third-stage larvae in H. rubidus?
They develop within a week under optimum conditions and are infective when swallowed by swine.
63
Where does H. rubidus invade in the host?
Gastric glands.
64
What are the clinical signs of hyostrongylosis?
Anemia, inappetence, occasional melena.
65
What type of gastritis does H. rubidus evoke?
Catarrhal, sometimes diphtheritic gastritis with ulceration.
66
During what conditions can transmission of H. rubidus be markedly reduced?
Dry summers.
67
Can transmission of H. rubidus occur under confinement conditions?
Yes.
68
Which medications are approved for the treatment of H. rubidus infection in pigs?
Fenbendazole, ivermectin, doramectin.
69
Fill in the blank: The adult worms of H. rubidus resemble those of _______.
Ostertagia spp.
70
What is the stomach worm of Mountain gorillas?
Hyostrongylus kigeziensis
71
What is Ollulanus tricuspis?
A parasite of the stomach of the pig, dog, cat, and other felids including the cougar, cheetah, and tiger.
72
What is the size of Ollulanus tricuspis?
Less than 1 mm long.
73
Describe the anterior end and vulva location of Ollulanus tricuspis.
The anterior end is rolled up, and the vulva is near the anus.
74
How does the female tail of Ollulanus tricuspis terminate?
It terminates in three or more sharp points.
75
What characterizes the male spicules of Ollulanus tricuspis?
They are short, equal, and bifurcated.
76
How can Ollulanus tricuspis be diagnosed?
Using endoscopy specimens.
77
What is the reproductive strategy of Ollulanus tricuspis?
Ovoviviparous.
78
Where do the larvae of Ollulanus tricuspis develop to maturity?
In the stomach of the host.
79
What is a unique aspect of the life history of Ollulanus tricuspis?
It can complete its life history within a single host.
80
What is the most likely means of transmission for Ollulanus tricuspis?
Ingestion of vomitus from an infected host.
81
What condition can Ollulanus tricuspis cause in cats?
Chronic gastritis.
82
What has been observed in the stomachs of infected cats with *Olllulanus tricuspis*?
A significant increase in mucosal fibrous tissue and mucosal lymphoid aggregates.
83
What is the efficacy of tetramisole against Ollulanus tricuspis?
Efficacious without side effects.
## Footnote
Drug not available in the USA
84
What is the formulation and dosage of tetramisole that has been reported effective?
A 2.5% formulation administered at 5 mg/kg.
## Footnote
Not available in the USA outside of research
85
True or False: Ollulanus tricuspis can only be found in cats.
False.
| Also pigs, dogs, cats & other wild felids (cheetahs, cougars, tigers)
86
Fill in the blank: Ollulanus tricuspis is a parasite that primarily affects the _______ of various felids.
stomach
87
What is the maximum length of adult Dictyocaulus worms?
Up to 80 mm long
88
Which species of Dictyocaulus is found in cattle?
Dictyocaulus viviparus
89
What is the distinguishing feature of the buccal cavity of Dictyocaulus?
The buccal cavity is small
90
Where is the vulva located in Dictyocaulus?
Near the middle of the body
91
What type of larva does the egg of Dictyocaulus contain when laid?
A first-stage larva
92
In which part of the host do adult Dictyocaulus organisms live?
In the lumen of the bronchial tree
93
What condition do Dictyocaulus organisms cause in the respiratory system?
Chronic bronchitis and localized occlusion
94
What is unique about Dictyocaulus viviparus in cattle?
It is the only nematode that reaches maturity in the lungs of cattle
95
How long does it take for Dictyocaulus to reach the infective stage under optimum conditions?
About 5 days
96
What happens to the characteristic 'food granules' in the intestinal cells of the first-stage larva of *Dictyocaulus viviparous* as development proceeds?
They become less conspicuous and finally disappear
97
What is the initial clinical sign of light infections with D. viviparus?
Calves cough occasionally and may breathe slightly faster than normal
98
What occurs during heavier infections of D. viviparus?
Partial or complete obstruction of the air passages
99
At what respiratory rate do respirations become forced in affected calves?
Reach a rate of 100 per minute
100
When do first-stage larvae appear in the feces of infected calves?
During the fourth week
101
What is a common complication in severe clinical illness associated with D. filaria in sheep and goats?
Presence of less obvious but more pathogenic parasites in the alimentary tract
102
What is the host species for D. arnfieldi?
Donkeys (Equus asinus)
103
True or False: D. arnfieldi is non-pathogenic in horses.
False
104
Fill in the blank: Egg-laying starts about ____ after infection for *Dictyocaulus viviparous*.
4 weeks
105
What are the superfamilies mentioned that are applicable to strongylid life history?
* Trichostrongyloidea
* Strongyloidea
* Ancylostomatoidea
106
What is the relationship between environmental contamination with eggs and host infection levels?
The rate of environmental contamination with eggs is in direct proportion to the degree of infection of the host population with adult worms
107
What factors influence the development and survival of the infective stage of strongylids?
Prevailing conditions of temperature and moisture
108
How does host resistance vary?
As a function of age, vigor, genetic constitution, presence or absence of an established infection, and acquired immunity
109
What can temporarily hold back the maturation of fourth-stage larvae?
Poorly understood influences
110
What are the three possibilities for infective larvae ingested by a now-premunized host?
* Rejected
* Replace established adult worms
* Become arrested in development
111
What is premunition?
A state of resistance to infection established after an acute infection has become chronic
112
What is the effect of protein supplementation on the periparturient rise in fecal egg counts?
It can abrogate the rise
113
What is the biotic potential of strongylids dependent on?
* Rate of production of fertile eggs
* Generation time
114
Which strongylid species is noted as the most fecund?
Haemonchus spp.
115
What temperature conditions are necessary for the development and survival of strongylids?
Varies with the species
116
How does age affect resistance to strongylid infection?
General increase in resistance with age
117
What is the significance of the ram named Violet in the context of strongylid resistance?
Progeny of Violet had smaller populations of worms and less reduction in hematocrit
118
What happens to the stable population of adult strongylids when removed by anthelmintic medication?
It vacates an ecological niche that is filled by maturation of arrested larvae or recently ingested infective larvae
119
What is self-cure in the context of strongylid infections?
The phenomenon where hosts expel worms and become protected against further infestation
120
What is the role of the lung nematode D. viviparus in cattle immunity?
It confers durable sterile immunity
121
What is the implication of self-cure for diagnosing haemonchosis in sheep or goats?
Profound anemia may indicate haemonchosis even if H. contortus worms are absent
122
What is the effect of a severe H. contortus burden on a previously infected sheep?
Part or all of the dose of larvae administered experimentally will fail to take
123
What occurs during the 'spring rise' in fecal egg counts?
A substantial increase in strongylid eggs observed in the feces of adult sheep
124
What are the consequences of maintaining stable strongylid populations?
They inhibit further infection or maturation of larvae
125
What is the distribution of D. viviparus infection?
Cosmopolitan in distribution
## Footnote
Clinical parasitic disease tends to be sporadic despite its widespread presence.
126
Where is clinical dictyocaulosis common?
British Isles
## Footnote
This region has shown ready acceptance and effective application of the vaccine.
127
What is the source of the new vaccine developed for H. contortus?
Intestines of harvested worms
## Footnote
This vaccine has been successful in Australia for managing drug resistance.
128
What is the significance of delayed maturation of larvae?
Helps perpetuate certain strongylids and spares the host during winter stress
## Footnote
It reduces biological losses during adverse conditions.
129
What may result from unseasonable maturation of arrested larvae?
Outbreaks of severe strongylidosis
## Footnote
Recognizing the parasitic cause is critical despite the unusual timing.
130
What is the first step in dealing with an outbreak of strongylidosis?
Identify the source of infection and separate the animals from it
## Footnote
Confining the herd in a barn or drylot facilitates observation and nursing.
131
What should be done for animals showing anemia, diarrhea, weakness, or depression?
Segregate them to facilitate therapy
## Footnote
Avoid separating nurslings from their dams unless necessary.
132
What can hasten the death of very sick animals when administering treatment?
Administration of an anthelmintic
## Footnote
Owners should be forewarned of potential further losses.
133
What is the benefit of an effective anthelmintic drench in primary haemonchosis?
Usually dramatic
## Footnote
It is important despite the ongoing infection by strongylid nematodes.
134
On what should the use of anthelmintic drugs be based?
Thorough knowledge of the biology of the worms and climatic conditions
## Footnote
Strategic treatments can help prevent outbreaks.
135
What are strategic treatments aimed to do?
Prevent buildup of infective larvae in pastures
## Footnote
This is crucial to avoid clinical strongylosis outbreaks.
136
When may tactical treatments be necessary?
After a period of moist, warm weather
## Footnote
This weather is particularly favorable for larval development.
137
Fill in the blank: The vaccine developed for H. contortus has proven successful in _______.
Australia
138
True or False: Strongylid nematodes are effectively managed with a variety of safe anthelmintic drugs.
True
139
What are common ruminant anthelmintics?
Fenbendazole, albendazole, ivermectin, doramectin, moxidectin, eprinomectin, levamisole, morantel
## Footnote
Other products are available outside the United States.
140
Which abomasal parasites are more susceptible to anthelmintic medication?
Haemonchus spp., Ostertagia spp., T. axei
## Footnote
These are more susceptible compared to small intestine parasites like Trichostrongylus, Cooperia, and Nematodirus spp.
141
What is the significance of postmortem examination in evaluating anthelmintic efficacy?
It prevents bias in reported results favoring anthelmintic efficacy
## Footnote
Biased results may occur if evaluations do not include the entire small intestine.
142
When should treatment for Ostertagia spp. be ideally carried out?
Fall or early winter
## Footnote
Treatment should target immature, arrested parasitic stages.
143
What are common causes of apparent anthelmintic failure?
Continued exposure to infective larvae, errors in anthelmintic selection and administration
## Footnote
Most cases of failure are not due to actual drug resistance.
144
Which parasites have displayed resistance to ivermectin and benzimidazoles?
H. contortus, T. circumcincta, Trichostrongylus colubriformis
## Footnote
Resistance has been observed in sheep and goats in various regions.
145
In which animal species is resistance to anthelmintics of greatest concern in the United States?
Goats
## Footnote
Resistance has also been reported in sheep and cattle.
146
What treatment is effective against clinical outbreaks of dictyocaulosis?
Fenbendazole, ivermectin, doramectin, levamisole, oxfendazole (not USA), albendazole
## Footnote
These treatments are effective against both adult and immature Dictyocaulus spp.
147
What was the outcome of Herd et al's (1983) trials on treating adult dairy cattle for helminths?
No change in milk production in 14 trials; increase noted in 7 trials; increase in control group in 5 trials
## Footnote
Mixed results indicate variability in treatment effectiveness.
148
What was the average increase in milk production reported in a large trial of 9721 lactations in Britain?
42 kg gain in milk production
## Footnote
Some interpreted this gain as not cost-effective.
149
What effect did oxfendazole treatment have in a New Zealand trial on cows?
2.24 kg more butterfat or 52.9 kg more milk produced
## Footnote
Positive response noted in 36 out of 47 treated herds.
150
What was the impact of ivermectin treatment on milk yield in an Australian trial?
Increased by 74 L during the first 100 days of lactation; 86 L over entire lactation
## Footnote
All herds had a positive response, but significant increase in only one herd.
151
What was observed regarding eprinomectin treatment in pastured dairy cattle in Canada?
Economic increase in milk production
## Footnote
Treatment at calving showed marginally significant improvements in breeding parameters.
152
What is the significance of ELISA technology in dairy cattle management?
Allows sampling of bulk milk for antibodies to monitor herd exposure to nematodes
## Footnote
Useful for diagnosing outbreaks and monitoring treatment effects.
153
What is a common agreement among parasitologists regarding treating young cattle?
Treatment is a profitable undertaking for dairy replacement heifers and beef stocker calves
## Footnote
Young cattle are significantly impacted by parasitism.
154
What were the findings of the study on moderate parasitism in lambs?
No significant differences in average daily gain or feed efficiency observed
## Footnote
Despite administration of high numbers of infective larvae.
155
What are the three main control efforts for strongylid infections?
* Selective breeding for resistant stock
* Rotational grazing
* Anthelmintic medication
## Footnote
Each method has its proponents and detractors.
156
What is the primary criterion for success in control efforts against parasitism?
Net profit that accrues
## Footnote
Not merely the number of worms fatally poisoned.
157
What is the theoretical goal of rotational grazing?
Prevent or limit intake of infective larvae
## Footnote
Grazing on a pasture for no longer than a week aims to reduce larval development.
158
What did Crofton (1958) conclude regarding periodic treatment of livestock?
It merely delayed the full parasite potential
## Footnote
Suggested early treatments to maximize delay in parasite population increase.
159
What is premunition in the context of host resistance?
A condition that prevents maturation of new waves of larvae
## Footnote
It truncates the growth curve of the parasite population.
160
What does the treatment regimen of ivermectin in the study consist of?
Four doses of ivermectin (0.02 mg/kg) administered at 3, 6, 9, and 12 weeks after spring turnout.
161
What is premunition in the context of host resistance?
A type of host resistance that truncates the growth curve of the parasite population by preventing maturation of new larvae.
162
What effect can periodic anthelmintic medication have on premunition?
It may interfere with the development of premunition.
163
What is the purpose of treating only the animals needing therapy in a flock?
To leave the remainder of the sheep shedding feces containing eggs from worms that are still susceptible to treatment.
164
What is the relationship between worm burden and anemia in sheep?
It is well established in the case of haemonchosis.
165
What is the FAMACHA technique used for?
To detect anemia in sheep and goats using the mucous membranes around the eyes.
166
What does the FAMACHA chart system help recognize?
Sheep in need of treatment for haemonchosis.
167
In what type of areas is the FAMACHA system particularly useful?
In warmer areas where haemonchosis is the major disease threatening sheep and goats.
168
What should be noted about the applicability of the FAMACHA system?
It is not designed to work where the major parasites are T. circumcincta or species of Trichostrongylus, Cooperia, or Nematodirus.
169
True or False: The FAMACHA results can be confused in areas where anemia is due to babesiosis or theileriosis.
True.
170
What are the effects of haemonchosis induced anemia visible in?
The mucous membranes around the eyes of sheep.
171
Fill in the blank: The FAMACHA technique combines the ability to detect anemia in sheep using the _______.
mucous membranes around the eyes.
