Parasitology Flashcards
(100 cards)
1
Q
Outline the importance of parasites
A
- Significant production loss
- Welfare
- Death of animal
- Zoonoses
- Force change in management
- Substantial cost (treatment, pasture management, manure management, quarantine, diagnostic testing, biosecurity)
2
Q
What does the method of treatment of endoparasites depend on?
A
The life cycle
3
Q
What is the significance of finding worm eggs or larvae in faeces?
A
- Life cycle completed
- Adult present in animal and able to cause clinical signs
- Damage has occurred, dealing with an ill animal
- Parasite has reached patency stage
- Environmental contamination has occurred
- If animal has been treated, parasite must be resistant to the treatment
4
Q
Describe the clinical signs associated with liver flukes
A
- Jaundice in some cases
- Loss of appetite, diarrhoea, emaciation
- Bottleneck may occur in some cases
5
Q
Describe the clinical signs associated with lungworms
A
- Persistent cough
- Lowering of head and stretching of neck
- Mouth breathing
6
Q
Describe the clinical signs associated with GI worms
A
- Weight loss, reduced appetite, diarrhoea, anaemia
- Bottleneck
7
Q
Outline the laboratory findings associated with liver flukes
A
- y-glutamyl transpeptidase or transferase
- Function of liver affected
- Serological assays
8
Q
Outline laboratory findings associated with lungworms
A
- Eosinophilia in blood and tracheal washes
- Serological assays
9
Q
Outline laboratory findings associated with GI worms
A
Plasma pepsinogen or gastrin (less common) increased
10
Q
Why is plasma pepsinogen increased with GI worms?
A
Pepsinogen cannot be converted to pepsin due to alteration in abomasal pH
11
Q
Outline some risk factors that may increase chance of liver fluke infection
A
- Heavy rains
- Floods
- High number of snails present
12
Q
Outline the typical epidemiology of lungworms
A
- Unpredictable
- Dependent on climate
- Fast development (5 days from first larval stage to infection)
- Typical signs within 1 week of ingestion of larval stage
13
Q
Outline the typical epidemiology of GI worms
A
- Spring rise
- Acute death of lambs 2-3 weeks after turnout onto pasture
14
Q
Give examples of changing patterns of sheep parasitism
A
- Haemonchosis: previously only SE England, now more widespread (Wales and Scotland)
- Nematodirosis: spring problem but now also in Autumn
- Trichostrongylosis: traditionally in autumn in store lambs, now earlier in summer, loss of younger lambs, or in mild winters so problems later than described
15
Q
What is the purpose of NADIS regarding anthelmintic use?
A
- Allows prediction and therefore preventative action
- This minimises the use of anthelmintics and so reduces potential for resistance development
16
Q
What is meant by parasitic load?
A
The amount of parasite infecting the host
17
Q
How can parasitic load be assessed?
A
- Faecal egg count
- Number of parasites in tissue
18
Q
Why might a parasitic infection be undetectable via faecal egg count?
A
- Parasite is in pre-patent stage and not yet shedding eggs/larvae
- Single sex infection (except cestodes and trematodes)
- Strong immune response from host preventing reproduction of parasites
19
Q
What are the goals of helminth control?
A
- Prevention of clinical disease
- Immunisation
- Economic (increase/minimise loss of productivity)
20
Q
What are the options for helminth control?
A
- Biological
- Vaccines
- Anthelmintics
- Pasture management
21
Q
Outline an example of biological control of helminths
A
- Duddingtonia flagrans
- Aerobic fungus that reduces number of infective larvae on pastures to an economically acceptable level
- Broad spectrum, no residues, no withdrawal period, active against drug resistant worms
- Novel mode of action and failed to be commercialised as is impractical to administer to pastures daily
22
Q
Outline the use of vaccines in helminth control
A
- Only 1-2 available
- Antigenes, native or recombinant/synthetic
- Targets include: intestinal protein, transporters, enzymes
- Can achieve high protection rate
- Problems in commercial large scale production
- Failure to commercialise
23
Q
Outline the use of chemotherapy in helminth control
A
- Very high development costs
- Mainstay of parasite control
- Fears of anthelmintic resistance
- e.g. benzimidazoles, imidazothiazoles, macrocyclic lactones
24
Q
How is anthelmintic resistance diagnosed?
A
- Faecal egg count comparison before and after treatment of the same animal
- Larval hatch test (in vitro culture of larvae in presence of anthelmintic compounds)
25
What is the mechanism for anthelmintic resistance?
- Point mutation leading to altered protein sequence and so anthelmintic is ineffective
- Established by selective pressure
26
Outline some treatment strategies to combat anthelmintic resistance
- Treatment frequency as low as possible to reduce selection pressure
- Grazing management
- New anthelmintic classes introduced
- Strict compliance with prescribed treatment regimes
- Change anthelmintic class annually
- Ensure are not underdosing
- no "dose and move"
- Quarantine infected animals
- Combination therapy
- Use plants with anthelmintic activity
- Avoid overstocking of animals
27
What is refugia?
Parasite finding refuge in tissue and so not exposed to anthelmintic
28
List the common abomasal helminth parasites of small ruminants
- Ostertagia ostertagi
- Haemonchus contortus
- Teladorsagia circumcincta
- Trichostrongylus axei
29
What is FAMACHA and how is it used?
- A scale to objectively assess the degree of anaemia due to abomasal worms
- Aids decision of whether to administer anthelmintic dose
30
Describe the classical post mortem signs of Haemochus contortus
- Severe gastroenteritis characterised by extensive submucosal hyperaemia and haemorrhage in the abomasum
- erosions adn ulcers as well as gross thickening of the abomasal wall
- Some degree of haemorrhages in parts of the small intestine
- Visible presence of worms
31
Why is faecal examination a good primary diagnostic tool for endoparasites?
- Eggs in faeces indicates GI worm
- Larvae in faeces indicates lungworm
- Non-invasive
32
How does an animal become infected with lungworm?
L3 larvae, either in intermediate host or free on pasture
33
What causes abdominal bleeding in an Angiostrongylus vasorum infection?
- Migration of larvae from stomach/intestine to lungs
- Secrete anticoagulants
- Parasite immune-mediated thrombocytopaenia, disseminated intravascular coagulation (DIC)
34
Describe the appearance of the heart and lungs of a dog infected with Angiostrongylus vasorum
- Alveolar infiltrates seen
- Interstitial patterning of lung
- Heart axis shifted to the left suggesting right ventricular enlargement
- Cardiac hypertrophy and pathological damages
35
How do sheep become infected with Haemonchus contortus?
Ingestion of L3 larval stage on damp grass
36
How is sudden death of lambs caused by Haemonchus contortus?
- Anaemia as a consequence of worms feeding
| - Loss of appetite
37
List the parasitic worms that can be found in the intestine of pigs
- Hyostrongylus rubidus
- Trichuris suis
- Strongyloides ransomi
- Oesophagostamum spp
- Ascaris suum
- Isospora suis
- Trichinella spiralis (adult)
- Macracanthorhynchus hirudinaceus
38
How do pigs become infected with Trichuris suis?
Ingestion of eggs containing L1 larvae
39
What can be used to treat Trichuris ovis infection?
Common anthelmintics e.g. fenbendazole, benzimidazoles, levamisole
40
What is a proglottid?
A segment of cestode worms, containing an ovary and genital pore. It matures as it moves towards to last segment of the cestode, and is shed as the infective agent
41
What does tapeworm infection in dogs and cats indicate?
Presence of fleas
42
Describe the clinical signs of heartworm infection in dogs
- Exercise intolerance
- Hydrothorax
- Hydroperitoneum
- Chronic cough
- Dyspnoea
- Haemoptysis
- Eosinophillian lung
- Oedema in lung parenchyma
43
Outline the treatment for Dirofilaria immitis
- Kill adult parasite first with adulticide
- Then all circulating microfilariae with microfilaricide
- May require surgery if vena cava syndrome occurs
44
Outline control of Dirofilaria immitis
- Entirely preventable using medication
- Screening and prophylaxis
- Ensure patient if microfilaria and adult free, can start prophylaxis
45
Which 2 species of Taenia can cause human disease?
Taenia saginata, Taenia solium
46
Compare Taenia saginata and solium
- Solium has greater public health implications as it has the capacity to use humans as an intermediate host, develops multiple cysticerci in vital organs often with fatal consequences
- saginata does not do this
47
How is infection with Eimeria spp acquired?
Consumption of food/water contaminated with mature (sporulated) oocysts
48
What dog parasite forms hydatid cysts?
Echinococcus granulosus
49
What is the significance of Fasciola hepatic infections?
- Condemnation of livers
- Emaciation and reduced growth rate
- High mortality in sheep
50
Outline the control of liver flukes in ruminants
- Treat infected animals with flukicides
- Eliminate snails in environment
- Implement sound husbandry measures
51
What is a Baermannn apparatus used for?
Used to isolate and concentrate larvae of lungworms from faeces
52
Compare the appearance of sporulated oocysts of Eimeria, Isospora, Cryptosporidium
- Eimeria: 4 sporocysts, each with 2 sporozoites
- Isospora: 2 sporocysts, each with 4 sporozoites
- Cryptosporidium: no sporocysts, 4 sporozoites
53
Describe the generic life cycle of GI nematodes
- Eggs in faeces
- Hatch
- Moult to L1 to L2 and then L3
- L3 are infective, ingested on damp pasture by host
- free-livingn stages 2-12 weeks to complete
- Host stage 16-21 days to complete (unless L3 arrest in host over winter)
54
Describe the life cycle of Nematodirus
- L1-L3 development occurs in eggs
- L3 hatch
- L3-5 moults occur in the host
55
Describe the life cycle of liver flukes
- Eggs shed in faeces
- Miracidium
- Ingested by snail
- Develop to sporocyst
- Develop to redia
- Develop to cercaria
- Metacercaria shed by snail, ingested by sheep
- Hatch to adult in sheep
56
Describe the clinical signs and seasonality of Haemonchus contortus
- Spring, after rain
- Weight loss, anaemia
- Hypoproteinaemia
- Bottle jaw
- Does not usually cause diarrhoea
57
Describe the clinical signs and seasonality of Trichostrongylus spp
- Traditionally autumn, now also in late summer months
| - Inappetance, diarrhoea, weigh loss, death, black scour
58
Describe the clinical signs and seasonality of Nematodirus battus
- Historically spring, now varying times of year
| - Diarrhoea most prominent sign, dehydration
59
Describe the clinical signs and seasonality of acute Fasciola hepatic infection
- July to December
| - Sudden death, anaemia, dullness, dyspnoea, ascites, abdominal pain
60
Describe the clinical signs and seasonality of sub-acute Fasciola hepatica infection
- October to January
| - Rapid weight loss, anaemia, submandibular oedema, ascites in some cases
61
Describe the clinical signs and seasonality of chronic Fasciola hepatica infection
- January to April
| - Progressive weight loss, anaemia, submandibular oedema, diarrhoea, ascites
62
What is the importance of ectoparasites?
- Animal welfare issue
- Economic impact (large animals)
- Zoonotic potential
63
List the direct effects of ectoparasites
- Pruritus and cutaneous lesions (secondary infection)
- Blood loss
- Myiasis
- Loss of production
- Downgrading of hide
- Allergy
- Zoonosis
64
List the indirect effects of ectoparasites
- Transmission of pathogens
- Transmission of zoonotic pathogens
- Accidental injury (cattle/horses bolting)
- Reduction in feeding due to discomfort
65
What is meant by eradication?
Elimination of a disease or pest without its return
66
Give an example of an ectoparasite that has been eradicated in the UK
Anopheles mosquito
| - but reappeared in some countries such as India
67
Give reasons why eradication programmes may fail
- Insecticide resistance
- Socio-economic factors
- Poor surveillance
68
What is meant by ectoparasite control?
Reduction of population leading to reduced transmission, reduce to acceptable level
69
Give examples of ectoparasite control methods
- Chemical
- Physical
- Biological
- trapping
- Modelling and forecasting
70
What are some considerations when choosing chemical control methods?
- Mode of action of drug
- Spectrum of activity
- Mode of application
- Speed of action required
- Efficacy/duration/frequency of reapplication
- Resistance
- Species to be treated
- Withdrawal periods
- Age restrictions
- Contraindications/drug interactions
- Cost
- Environmental contamination/toxicity to non-target species
71
How might the life cycle of a parasite affect its control?
- Indirect life cycle more difficult to control as have to consider intermediate host
- Not all stages will be susceptible to the same chemical control methods for example
- Some stages may be persistent in the environment
72
List the groups of chemical control methods for ectoparasites
- Neurotoxins
- Insect growth regulators
- Repellants
- Dessicants
- Synergists
- Lime sulphur
73
List the mechanisms of action of neurotoxins for ectoparasite control
- Cholinesterase inhibitors
- Octopamine receptor stimulant
- GABA inhibitor
- Insect nicotininc Ach receptor stimulant (+/- GABA agonist)
- Na channel activator
- Na channel blocker
- Cl channel activators
- Cl and GABA channel inhibitors
74
List the groups of ectoparasite neurotoxins
- Organophosphates
- Carbamates
- Triazepentadienes
- Phenylpyrrazoles
- neonicatinoids
- Pyrethrins
- Pyrethroids
- Semicarbazones
- Macrocyclic lactones
- Isoxalines
- Spinosyns
75
What is the mechanism of action of organophosphates?
Cholinesterase inhibitors
76
Outline the use of organophosphates and give examples
- Used on animal/in environment
- Use reduced due to neurotoxicity concerns
- Fnethion, diazinon, dichlovos, malathion, proprtamphos, dimpylate
77
What is the mechanism of action of carbamates?
Cholinesterase inhibitors
78
Outline the use of carbamates and give examples
- Less toxic than organophosphates
| - Propoxur, carbaryl, methiocarb, butocarb, fenoxycarb
79
What is the mechanism of action of triazepentadienes?
Octopamine receptor stimulant
80
Outline the use of triazepentadienes and give examples
- Broad action vs mites, ticks
- No effect on SA insects, but used for lice in cattle/pigs
- Dip/rinse, spot on
- Contraindicated in horses and cats
- e.g. Amitraz
81
What is the mechanism of action of phenylpyrrazoles?
GABA inhibitor
82
Outline the use of phenylpyrrazoles and give examples
- Action vs felas and ticks
- e.g. Fipronil and pyriprole
- Fipronil active vs Trichodectes canis but toxic to rabbits
83
What is the mechanism of action of neonicatinoids?
Insect nicotinic Ach receptor stimulant
84
Outline the use of neonicatinoids and give examples
- Action vs fleas
- e.g. Imidacloprid, Nitenpyram, dinotefuran
- Imidacloprid active against Trichodectes canis
- Nitenpyram fast acting but short lived effect
85
What is the mechanism of action of pyrethrins?
Na channel activator
86
Outline the use of pyrethrins and give examples
- Rapid knockdown vs insects/fleas
- Poor persistence
- Toxic to cats
- e.g. Dichlorvos, fenitrothion
87
What is the mechanism of action of pyrethroids?
Na channel activator
88
Outline the use of pyrethroids and give examples
- Active vs fleas, flies, keds, lice, ticks
- Repellant +/- knockdown
- Toxic to cats and fish
- e.g. permethrin, cypermethrin, deltamethrin, flumethrin
89
What is the mechanism of action of semicarbazones?
Na channel blocker
90
Outline the use of semicarbazones and give examples
- Active vs fleas
- e.g. Indoxacarb
- Indoxacarb is a pro-druc, activated by insect only and so has low mammalian toxicity
91
What is the mechanism of action of macrocyclic lactones?
Cl channel activators
92
Outline the use of macrocyclic lactones and give examples
- Action vs selected ecto and endoparasites
- Absorbed systemically so ectoparasite effect not affected by bathing
- Especially good for parasites with tissue stages e.g. warbles
- Care re neurotoxicity if MDR1 gene mutation (collies/herding breeds)
- Avermectins and milbemycins
93
Name the avermectins
- Ivermectin
- Selamectin
- Doramectin
94
Name the milbemycins
- Milbemycin oxime
| - Moxidectin
95
What is the mechanism of action of isoxazolines?
GABA and Cl channel inhibitor
96
Outline the use of isoxazolines and give examples
- All licensed for fleas/ticks
- Unaffected by bathing
- Rapid onset - kill fleas before eggs laid
- e.g. Afoxolaner, flurolaner, sarolaner, lotilaner
- Serolaner also licensed for Sarcoptes, demodex, otodectes in dogs
97
What is the mechanism of action of spinosyns?
Nicotinic Ach receptor stimulant and GABA agonist
98
Outline the use of spinosyns and give an example
- Oral tablet for dogs/cats
- Unaffected by bathing, rapid effect
- May vomit after administration although effect usually short-lived
- e.g. Spinosad
99
What is the side effect of neonicatinoids of greatest concern?
May be causing the declining bee population
100
What are the 3 groups of Insect Growth Regulators?
- Juvenile growth hormone analogues
- Chitin synthesis inhibitors
- Triazine derivatives
