NAVLE Veterinary Entomology & Acarology: practice questions

1 · 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

2 · Lice · medium

The dog chewing louse Trichodectes canis is of clinical importance beyond pruritus because it is an intermediate host of:

1. Toxocara canis
2. Dipylidium caninum
3. Hepatozoon canis
4. Dirofilaria immitis

3 · Hard ticks · medium

A dog with canine monocytic ehrlichiosis lives in a kennel with a long-standing tick infestation that persists indoors through winter. The vector is most likely:

1. Rhipicephalus sanguineus
2. Ixodes ricinus
3. Amblyomma americanum
4. Dermacentor reticulatus

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 · Mange mites · easy

A kitten has dark brown, crumbly waxy discharge in both ear canals and shakes its head. The most likely parasite is:

1. Demodex gatoi
2. Cheyletiella blakei
3. Notoedres cati
4. Otodectes cynotis

7 · 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

8 · Vectors of babesiosis and theileriosis · hard

An American pit bull terrier in a region without its usual vector tick is diagnosed with Babesia gibsoni. The most likely route of infection is:

1. Ingestion of an infected tick
2. Mosquito bite
3. Transovarial transmission in fleas
4. Bite wounds or blood exchange during fighting

9 · Ectoparasiticides and resistance · medium

A Collie given a high dose of a macrocyclic lactone for mange develops ataxia, mydriasis, tremors and coma. The underlying reason is:

1. Hypersensitivity to dead mites
2. An inherited deficiency of acetylcholinesterase (AChE) that is common in herding breeds
3. Amitraz contamination of the product causing alpha-2 adrenergic overdose
4. An ABCB1 (MDR1) mutation that removes P-glycoprotein at the blood-brain barrier

10 · 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