RCVS Statutory Membership Examination Veterinary Entomology & Acarology: practice questions

1 · Culicoides midges · easy

Sweet itch (insect bite hypersensitivity) in horses is caused mainly by hypersensitivity to the saliva of:

1. Aedes and Culex mosquitoes
2. Culicoides midges
3. Stomoxys calcitrans
4. Chorioptes pastern mites

2 · Lice · medium

Cattle with chewing lice (Bovicola bovis) and sucking lice were treated with an injectable macrocyclic lactone. Three weeks later the sucking lice have gone but chewing lice remain. The best explanation is:

1. Chewing lice are always resistant to all macrocyclic lactones, whatever the dose or route used
2. The injection killed only louse eggs
3. Chewing lice feed on skin debris and ingest little of a systemically distributed drug
4. Sucking lice live off the host and were not exposed

3 · Fleas · medium

A dog has intense pruritus with papules and crusts over the lumbosacral region, tail base and caudal thighs. The most likely diagnosis is:

1. Sarcoptic mange
2. Otodectic mange
3. Demodicosis
4. Flea allergy dermatitis

4 · Mange mites · medium

A dog with intense pruritus of the ear margins, elbows and hocks kicks with its hind leg when the ear margin is rubbed. Three superficial skin scrapings are negative. The most appropriate interpretation is:

1. Sarcoptic mange is ruled out by three negative scrapings, so the dog should be investigated for food allergy
2. The dog has flea allergy dermatitis, which explains the pinnal-pedal reflex, and needs no further testing
3. Sarcoptic mange remains likely; negative scrapings are common, so a treatment trial or serology is justified
4. The signs indicate demodicosis, which needs no treatment

5 · Mange mites · medium

A heavy horse with feathered lower legs stamps and bites at its pasterns; skin debris shows mites with short unjointed pedicels and cup-shaped suckers. The mite is:

1. Trombicula larvae
2. Chorioptes bovis
3. Psoroptes ovis
4. Sarcoptes scabiei

6 · Myiasis · hard

Why is systemic treatment against cattle warble (Hypoderma bovis) larvae avoided in the period when larvae lie in the spinal canal?

1. Death of many larvae in the epidural fat can cause inflammation and posterior paralysis
2. Larvae in the spinal canal are already dead
3. The larvae are resistant to all drugs at this stage
4. Treatment at this stage usually contaminates milk permanently and makes the carcass unfit for sale

7 · Ectoparasiticides and resistance · medium

Amitraz should not be used on horses because it:

1. Causes severe photosensitisation
2. Is a potent acetylcholinesterase inhibitor
3. Is ineffective against all horse parasites
4. Causes gut stasis and colic