Parasitology 2 Flashcards
Name the juvenile growth hormone analogues
- S-methoprene
- Pyriproxyfen
- Dicyclanil
- Fenoxycarb
What is the mode of action of lufenuron?
Chitin synthesis inhibitor
What is the mode of action of cyromazine?
Triazine derivative
Describe the use of Insect Growth Regulators
- No adulticidal properties
- Interrupt environmental stages of flea life cycle but slow to act
- Important in household flea sprays
Outline the safety of Insect Growth regulators
- Very safe
- Only act at receptors present in insects
Describe the mechanism of action of juvenile hormone analogues
- Mimic activity of juvenile hormone
- Ovicidal activity
- Prevents flea larvae developing
Give examples of uses of juvenile hormone analogues
- Spot-ons e.g. frontline combo (combination with adulticide)
- Environmental sprays e.g. indorex
Explain the mechanism of action of chitin synthesis inhibitors
Prevent normal developing of the exoskeleton, thus stopping larvae developing
Give examples of and use of ectoparasite repellants
- Pyrethrins/pyrethroids
- Diethyltoluamide (DEET)
- Citronella
- Repel flying insects
Give an example of and use of dessicants for ectoparasites
- Sodium polyborate
- Used in environment e.g. carpet powders
Give an example of and use of synergists
- Piperonyl butoxide
- Inhibits insect detoxification pathways and increases available concentration of insecticides
- Used especially with pyrethrins to reduce insecticide content
Outline the use of lime sulphur dip
- Traditional pesticide used especially in cats for control of Demodex cati, Cheyletiella, lice
- Also fungicidal and bactericidal
- Unpleasant odour, may stain light coats, must prevent ingestion
Give examples of topical preparations of ectoparasite drugs
- Spray
- Dip
- Powder
- Spot-on
- Pour-on
- Collar
- Ear tag
Give examples of systemic preparations of ectoparasite drugs
- Injectable
- Oral
- Topically applied
What is a benefit of spot on preparations?
Good compliance
What are some disadvantages of spot-on preparations?
- Human toxicity immediately after application (esp. children)
- Ingestion of product
- Occasional skin lesions at site of application
- Wetting/bathing may compromise action
- Concentration gradient with distance from site of application if not absorbed systemically
What are some disadvantages of dips and sprays?
- Operator exposure
- Dips will be depleted of chemical with use, so need to top up between animals
- Care regarding appropriate storage and disposal (environmental contamination/pollution)
What are some disadvantages of collars for ectoparasite control?
- Remove during swimming/washing to avoid depletion of drug from collar and contamination of aquatic life
- Occasional contact irritation
- Care to prevent animal chewing/swallowing collar
- Use immediately once opened
What is the significance of duration of action?
Shorter duration of action will require more frequent application, which may reduce compliance and increase risk of infection
Outline reasons for lack of efficacy of anti-ectoparasitic drug
- Resistance may occur, but usually other factors account for lack of efficacy
- Inappropriate frequency/dosing
- Incorrect administration
- Depletion due to bathing/wetting
- Failure to control re-infestation from other animals/environment
Give examples of how anti-ectoparasitic drugs may lead to environmental effects
- Sheep dip disposal can contaminate waterways
- Insecticidal material in dung may affect dung beetle and flies
In what species is the use of fipronil contraindicated?
Rabbits (fatalities)
In what species is pyrethrin and pyrethroid use contraindicated?
- Cats
- Pyrethroids contraindicated in fish and birds
In what animals are macrocyclic lactones contraindicated? Explain
- Collies/herding breeds
- More likely to have MDR1 gene (multi-drug resistance), encodes for P-glycoprotein
- Responsible for pumping drugs out o the CNS
- Where there is a mutation in MDR1, drug crosses the BBB and leads to neurological signs/death
In what animals is spinosad contraindicated?
Dogs with epilepsy
In what scenario is use of Advocate contraindicated and why?
- Advocate contains moxidectin/imidacloprid
- Canot be used with any other macrolyclic lactone e.g. Milbemax (milbemycin and praziquantel)
In what scenario is amitraz use contraindicated?
- Should not be applied by people taking monoamine oxidase inhibitors (anti-depressants) or with diabetes mellitus
- Not to be used concurrently with alpha-2 adrenergic agonists e.g. medetomidine
Outline physical methods of ectoparasite control
- Conditions unsuitable for parasite to live/reproduce in, or avoid contact with parasite
- removal of dung, moist bedding, straw, food waste
- Minimise pasture worm burdens, tail docking, dagging (reduces myiasis of sheep)
- Barriers (e.g. fly masks) useful where parasite only spends part of life on host and are harder to control (prevent irritation /infection)
Outline biological control methods for ectoparasites
- Using organisms that are predators, competitors or pathogens of parasites
- Best for those that live or reproduce in the environment
- e.g. parasitoid wasps
Explain the use of trapping and monitoring in the control of ectoparasites
- Can be used to protect (usually enclosed) environments such as stables or milk parlours
- Useful indicator of when additional measures e.g. chemical treatment may be needed
Explain the use of modelling and forecasting in the control of ectoparasites
- Predict seasonal patterns of particular ectoparasites
- Helps vets/farmers to integrate chemical and non-chemical control techniques and use ectoparasciticides prophylactically
Give examples of natural botanical products that have been suggested in ectoparasite control
- Citronella
- Cedarwood
- Lemongrass
- Rosemary
- Sesame
- Lavender
- Tea-tree
- Eucalyptus
What is a disadvantage of using natural botanical products in ectoparasite control?
Little safety and efficacy testing (use of several products with similar active ingredients or interacting agents may lead to toxicity to pet)
Give the life cycle of the flea
- Adult on host
- Eggs laid
- Hatch in environment
- Larvae form pupae in environment
- Can stay in environment for long periods of time
- Adults jump onto host
List the flea adulticides
- Imidacloprid
- Fipronil
- Spinosad
- Pyriprole
- Metaflumizone
- Selamectin
- Indoxacarb
- Isoxazolines
- Nitenpyram (short action)
List the flea larvicidals
- Imidacloprid
- Indoxacarb
- Selamectin
- S-methoprene (IGR)
- Lufenuron (IGR)
List the flea ovicidals
- Spinosad
- Selamectin
- S-methoprene (IGR)
- Lufenuron (IGR)
List products that are effective at treating lice
- Topical organophosphates
- Pyrethroids
- Topical avermectins
- Ivermectin injection (sucking lice)
- Amitraz (cattle and pigs)
- Imidacloprid, fipronil (dogs, cats)
Describe the control of lice
- Killed by most routine flea treatments
- Heavy infestations associated with unsanitary conditions so attend to environment
- Basic hygiene is sufficient
Outline methods of control of blood feeding flies
- Fly avoidance
- Repellants
- Topical insecticides e.g. organophosphates, pyrethrins/pyrethroids
- Barriers
- Insecticidal treatment of environment
- Control of breeding sites
Outline the control of nuisance flies
- Topical organophosphates
- Pyrethroids
- E.g. ear tags
What are the direct effects of tick infection?
- Blood loss
- Local cutaneous damage and inflammation
- Secondary skin infection
- Production loss
What are the indirect effects of tick infection?
Vectors of disease
What diseases are transmitted by Ixodes ricinus?
- Borrelia burgdorferi
- Louping ill virus
- Ehrlichia
- Anaplasma
- Babesia in cattle
What diseases are transmitted by Haemophysalis punctata and where is this tick found?
- S England and Wales, widely in Europe
- Babesia gibsoni
What diseases are transmitted by Dermacentor reticulatus and where is this tick found?
- West Europe, rarely UK
- Babesia canis
What diseases are transmitted by Rhipicephalus sanguineus and where is this tick found?
- S Europe, cannot survive outside of temperate climates (may be found in warm kennels)
- Babesia canis, Babesia vogeli, Ehrlichia canis, Rickettsia, Anaplasma
Describe louping ill
- Infectious ovine encephalomyelitis
- Mainly causes disease in sheep and grouse in upland areas
- Occasionally infects humans and other animals
- Attacks CNS, significant suffering of animal
Outline the control of Louping ill
- No statutory control measures
- Control is voluntary
- Use of acaricides
- Inactivated vaccine against virus
What is babesiosis caused by?
Babesia spp are intraerythrocytic protozoan parasites
Outline infection with Babesia
- Destruction of erythrocytes causing severe anaemia (haematuria may be seen)
- canine cases range from a hyperacute, shock-associated, haemolytic crisis to subclinical infections
- Signs: fever, inappetance, weight loss, mucus membrane pallor, lethargy, jaundice, splenomegaly, lymphadenopathy, haemolytic anaemia, haemoglobinuria
- Severe cases lead to acute collapse, multiple organ failure, death
What are the aims of tick control?
- Prevent attachment
- Prevent transmission of pathogens by prompt killing/removal
What are the strategies of tick control?
- Avoid tick habitats and local tick “hot spots” during late spring and summer
- Destruction of tick habitats and spraying environmental pesticides
- Daily inspection of haircoat, prompt removal of ticks, careful disposal
- Repellent or acaricide with rapid knockdown effect
Describe the method of tick removal
- Tweezers/specials tools, avoid handling with uncovered fingers
- Place instruments around area where mouthparts enter skin
- Slow, steady motion to pull tick away from skin
- Do not damage tick and ensure mouthparts are removed
- Place in sealed container, disinfect area around bite
What factors affect acaricide selection?
- Likely species of tick
- Required duration of action
- Likelihood of swimming/bathing
- Risk of adverse effects (species specific)
- Potential for drug interactions
- Accidental contact
Name the groups of tick control drugs
- Isoxalzolines
- Pyrethroids
- Phenylpyrnazoles
Which isoxazolines are licensed for cats?
Flurolaner and sarolaner
Name the isoxazolines used for ticks, their duration of action, application and the species they are licensed for
- Aloxolaner, tablet: 4 weeks, dogs
- Flurolaner, tablet for dog, spot on for dogs and cats: 8-12 weeks
- Lotilaner, tablet: 4 weeks, dogs
- Sarolaner: 4 weeks, spot on for cats, tablet for dogs
Name the pyrethroids used for ticks, their duration of action, application and the species they are licensed for
- Deltamethrin, collar: 20-24 weeks, dogs
- Flumethrin, collar: 32 weeks, dogs and cats
- Permethrin (imidacloprid) spot on: 3-4 weeks, dogs
- Permethrin (dinotefuncin, pyriproxyfen) spot on: 3-4 weeks, dogs
Name the phenylpyrrazoles used for ticks, their duration of action, application and species they are licensed for
- Pyriprole: spot on, 4 weeks, dog
- Fipronil: spot on, spray, 4 weeks, dog and cat
- S-methoprene (fipronil): spot on, dog 4 weeks, cat 2 weeks
- Firpronil and amitraz: 5 weeks, spot on, dogs
Outline the control of ixodid ticks in cattle and sheep
- Prolonged treatment
- Acaricides topically (dips, spray, shower, spot-on, slow release ear tap of OPs)
- OPs, pyrethroids, amitraz
- Macrocyclic lactones parenterally
- Weekly in tick season
- Removal of stock from infected pasture
Describe the direct effects of mites
- Cutaneous lesions (mange)
- Loss of blood or other tissue fluids
- Immunopathological response
- Zoonotic
Describe the indirect effects of mites
- Secondary bacterial infections
- Transmit pathogens
Describe mange
- Infestation by mites (acariasis)
- Severe dermatitis
- Erythema, pruritus, scale formation, lichenification, crust formation, alopecia
- Significant welfare problems, economic losses
Describe the mite life cycle
- Hatch from eggs, 6 legs
- Larva moult to become 8 legged nymph
- 1-2 nymphal stages
- Nymph moult to become adult
- Adult female lays eggs
Outline how mite life cycle affects treatment
- Some only on host to feed (e.g. Dermanyssus gallinae) and so are difficult to treat
- Need to treat environment
Describe canine sarcoptic mange
- Affects large number of mammalian species
- Strains usually host adapted, but can be zoonotic
- Highly contagious, reservoir in foxes
- Can survive off host for 2-3 weeks
Describe the actions against sarcoptic mange
- Treat affected animals
- Treat all in contacts
- Treat environment
- Drugs for pruritus and secondary infection
- Advise owner re zoonotic risk
- Isolate affected animals
- Prevent future infestation (avoid fox contact, routine use of scabicidal product)
Name the drug options for treatment of sarcoptic mange in dogs
- Moxidectin
- Selamectin
- Sarolaner
- Amitraz
Outline the use of moxidectin in dogs as a sarcoptic mange treatment
- Monthly application for 2 doses
- Also active vs fleas, selected other ectoparasites and endoparasites
Outline the use of selamectin in dogs as a sarcoptic mange treatment
- Monthly appplication for 2 doses
- Also active vs fleas, selected other ecto and endoparasites
Outline the use of sarolaner in dogs as a sarcoptic mange treatment
- Monthly tablet for 2 doses
- Also licensed for fleas, ticks, Demodex, Otodectes in dogs
- Only isoxazylene licensed for sarcoptic mange
Outline the use of amitraz in dogs as a treatment for sarcoptic mange
- Weekly baths
- Very effective but more time consuming treatment
- Side effects to animals/people, physically more demanding
Describe canine demodectic mange
- Present in small numbers as a commensal
- Clinical disease associated with reduced immuno-competence
- Juvenile onset, likely to resolve spontaneously with age
- Do not treat if mild-localised, only if generalised
- Not contagious, no environmental involvement
Outline sheep scab
- P. ovis causes sheep scab
- Economic importance
- Reportable in many countries
Outline the control of sheep scab
- Establish source
- Review quarantine procedures
- Contact neighbours to warn
- Check shared fences for gaps/common rubbing areas, consider double fencing
- Treat sheep with dip or injection
Outline the epidemiology of coccidiosis in chickens and farm animals
- Transmission via contaminated water and food
- Young age of host (esp. where insufficient colostrum)
- Endemic stability of Coccidia
- Overcrowding
- Higher prevalence in spring due to higher prevalence of other endoparasites at this time
Describe the clinical presentation of coccidiosis in chickens
- Loss of appetite and emaciation
- Anaemia, weakness
- Diarrhoea, weight loss
- Death
Explain how Eimeria causes its clinical signs
- Damage to superficial layer of GIT
- Destroys blood vessels leading to haemorrhage
- Anaemia as a consequence
- Malabsorption therefore weight loss and diarrhoea
Describe the characteristic post mortem finding of Eimeria tenella in chickens
Haemorrhage in the caeca
Describe the characteristic post mortem finding of Eimeria in rabbits
Enlarged liver with multi-focal greyish white coalescing lesions/nodules and yellowish liquid caseous pus
Describe the clinical signs of coccidiosis in calves
- Diarrhoea, may be haemorrhagic
- Weight loss and reduced weight gain
Describe the life cycle of Eimeria
- Sporulated oocyst ingested by animal from environment
- Excysts (due to stomach acid)
- Sporozoites released, invades host cell, begins to grow (schizogony)
- Schizont produced, contains merozoites, ruptures, merozoites release
- Merozoites invade host cells, repeat asexual reproduction phase
- 2nd gen merozoites sexually reproduce following meront rupture
- Type 2 merozoites invade host cells, either form macrogametocyte (F) or microgamont (M)
- MIcrogametocytes released from cell, fuse with macrogamont, form zygote (oocyst)
- Oocyst exits cell and excreted
- Oocyst sporulates to become infective
Name the most common Eimeria species causing coccidiosis in chickens
- E. acervulina
- E. nectriz
- E. tenella
Describe the location and pathogenicity of E. acervulina
- Mostly duodenum
- Mild disease
- Upper SI
- Older chickens
- Leads to egg production drop in layers
Describe the location and pathogenicity of E. necatrix
- Mid-small intestine
- Severe disease
- Bloody diarrhoea, death
Describe the location and pathogenicity of E.. tenella
- Only caecum involved
- Severe disease
- especially chicksn less than 6mos old
Which Eimeria species are primarily responsible for coccidiosis in cattle?
- Eimeria bovis
- Eimeria zuernii
What does the finding of Eimeria oocyts in cattle faeces indicate?
- Infection
- Even without clinical disease, may be due to variable susceptibility but reasons largely unknown
Describe the frequency, morbidity, mortality and presence of symptoms of sub-clinical coccidiosis in cattle
- High frequency in adults
- High morbidity
- Low mortality
- Symptoms usually absent
Describe the frequency, morbidity, mortality and presence of symptoms of clinical/overt coccidiosis in cattle
- Low frequency in adults
- High morbidity
- High mortality
- Symptoms usually present
Outline the methods of diagnosis of coccidiosis in cattle
- Clinical diagnosis not very specific
- Pathology: very specific but time consuming
- Laboratory diagnosis: metabolic parameters, faecal smears and flotation, McMaster method, PCR, serology
Describe the pathological lesion scoring of coccidiosis in cattle
- Score intestinal lesions 0-4
- 0: no lesion
- 1: very mild lesion
- 2: mild lesion
- 3: quite severe damage
- 4: severe damage to the intestines
Outline the impact of subclinical coccidiosis
- Significant economic impact
- Treatment expensive
- Production loss due to reduced growth, high morbidity/mortality, egg production drop
- Condemnation of emaciated carcasses
Outline problems in the management of coccidiosis
- Food residues of coccidiostats
- Lasalocid (ionophore group, most common to use) residues in eggs
- Could have adverse effects on health of humans, potent cardiovascular properties
Outline the treatment of coccidiosis
- Usually self-limiting, immunity develops rapidly, maintained by continuous exposure
- Treated animals protected for weeks
- Careful management of young, and to prevent exposure in older animals
- Limit risk of introduction of infected animals into herd
What are the aims of metaphylactic treatment against coccidiosis?
- Prevent disease
- Prevent production losses
- Reduce contamination and thus infection pressure
- Maintenance of productivity
- Target early/various life cycle stages
Outline the principles of the treatment of subclinical coccidiosis
- Widespread subclinical coccidiosis will require aggressive control programs and many years
- Practical control programme and sound management
- Aims to eliminate disease and reduce economic impact of subclinical disease
From what age onwards can coccidiosis occur in calves and why?
Will not occur before 18 days old as the animal is still suckling and the life cycle takes ~3 weeks
(there is no vertical transmission, must be contaminated feed/water)
List the drugs licensed for prevention/treatment of blowfly strike in sheep and give the group they belong to
- Alpha-cypermethrin, cypermethrin and deltamethrin: pyrethroids
- Diazinon (dimpylate): organophosphate
- Cyromazine and dicyclanil: IGRs
