dog and cat ectoparasites

flea species

fleas are insects - 6 legs, distinct body regions

adult fleas suck blood

wild animals - all rodents, carnivores, birds, domestic small and companion animals

not ususally a problem for livestock

>95% of flea species are ectoparasitic on mammals

general morphology of flea

dark glossy brown

laterally compressed to fit between hairs

3rd pair legs longer, stout

body spines to prevent removal during grooming

resilin in back legs is compressed to release 

peak acceleration = 100G

clearing and preserving specimens to see characteristics

place flea in 10% potassium hydroxide

water

dehydrate in alcohol series to 100%

xylene to clear

DPX or similar to mount on glass slide

nice clear prep for ID

veterinary importance of fleas 

most common cause of skin problems in cats

intense irritation, anaemia

FAD - flea allergic dermatitis of dogs and cats

skin reactions and dermatitis in people

transmission of tapeworm - dipylidium canium, bacteria - bartonella cat scratch disease

generalised life cycle of fleas 

95% life cycle is hidden in environment 

adult flea survives 21days on host, takes multiple blood meals, several times per day, female begins laying eggs 36h later, later on average, depositing 20-30 eggs per day 

diagnosis of fleas

presence of fleas

pruritis 

presence of flea dirt

• comb hair and put debris on wet paper towl 

• flea dirst appears red

larvae actively move away from light 

• maggot like, distinct brown head

• 13 segments, posterior bristles

• susceptible to desiccation

• looping movement

• can move several meters

diagnosis of FAD

clinical signs = alopecia, excessive grooming, skin damage

hypersensitivty to allergens in flea saliva

one flea can trigger response

secondary infections possible 

transmission of dipylidium canium

mature tapeworms proglottis disintegrate, producing eggs

eggs packet of dipylidium caninum

flea larvae or trichodectes ingest eggs - cysticercoids develop

adult tapeworms develop when infected fleas or lice are swallowed 

segments are mobile - can emerge from anus and crawl onto coat, releasing egg packets onto coat where fleas and lice ingest them 

flea control

adulticides

• isoxazolines

• phenylopyrazole, fipronil spot-on or spray 

• neonicotinoid, imidacloprid spot-on

• other - nitenpyram tablets, flumethrin/imidacloprid collars

enviromental treatments

• kills eggs and larvae - insect growth regulators - chitin synthetase inhibitors - inhibits egg hatch and proper moulting, juvenile hormone analogues - prevents moulting/pupation e.g methropene 

• kills larvae and adults - insecticides - synthetic pyrethroids e.g permethrin - toxic to cats, low efficacy, present in some flea sprays 

owner education

if only adulticide or enviromental treatments used then owners will still see fleas on their pet

if both adulticide and enviromental treatments are used but used inconsistently or just once, then reinfestation will occure by adults emerging from pupae

combined approach targeting fleas on host and enviroment needed for 2-4 months minimium to control fleas in infested houses

continuous coverage needed - owner compliance of paramount importance 

other hygiene measures - vaccuming and washing bedding to kills eggs/ larvae/ pupae 

mites

mites and ticks don’t have distinct body regions like insects. 8 legs in adults 

burrowing and non-burrowing - both can cause mange 

burrowing mites

3 genera, 5 species

• sarcoptes scabei

• notoedres cati

• demodex spp

sarcoptes scabei - sarcoptic mange/ scabies

1 species - host adapted forms

transmitted during physical contact 

highly contagious 

causes mange in dogs, foxes, pigs, camelids

causes severe mange of livestock in warmer countries but rare uk

sarcoptes scabei - morphology 

round flattened with rounded head

stumpy front legs 

dorsal surface has folds of cuticle giving rise to thumb print pattern and is covered scales and prominent spines 

sarcoptes scabei - life cycle

each tunnel contains a single female mite - 3 eggs per day, hatch larvae within tunnels after 3-4 days

larvae exit tunnels and successive moulting to eight-legged protonymph, tritonymph and adults in pockets on skin 

egg to adult in 14 days

sarcoptic mange

intensely pruritic, papular lesions, hair loss and crusting

mange can spread - most severe forms of condition are more often seen on head - periocular skin, pinnal margins - neck elbows and hocks

hypersensitivity 

wildlife - highly pathoegenic in foxes, hedgehogs possible wildlife resevoir of infection for pets

human form - humans - human scabies - distinct and highly contagious, debilitating 

sarcoptes scabei - diagnosis

itchy dog

superficial and broad skin scrapings

dermatitis in household

ELISA

rarely seen in cats

in skin scrapings look for evidence of all life cycle stages

sarcoptes scabei control

macrocyclic lactones: selamectin, moxidectin spot ons

isoxazolines - fluralaner tablets

amitraz washes 

contra-indications - ivermectin not recommended due to CNS signs in collies

notes = treat all in contact with dog

treat all grooming instruments and bedding 

notoedres spp

found on face, head and ears of cat and occasionally other small animals

morphology - like sarcoptes in shape, prominent dorsal striations in form of concentric rings. no scales and spines. very small. dorsal anus(arrow)

life cycle similar to S. scabei

rare but severe notoedric mange can be fatal 

transient human dermatitis

treatment - macrocyclic lactone spot on 

demodex spp - demodicosis/ demodectic mange

many species, host specific - highly evolved to occupy hair follicles, feed on dead skin

dermdex canis - dogs

dermodex cati and demodex gatoi - cats 

life cycle of demodex spp

demodex spp normally commensal

life cycle takes 18-24 days to complete

demodex spp are unable to survive away from hosts body 

in dogs transmission is via mammary skin while suckling 

demodex spp affect all animals, humans too, very host specific

common dermatological condition of dogs 

very rare in cats  

demodex spp significance

when health is compromised

• scaling and alopecia, papules and pustles

• face, shoulder, neck and limbs 

dogs - 2 clinically distinct forms, classified in various ways. can be adult or juvenille in onset. complex pathoegenesis. thickened skin, pustles, crusts 

localised - mainly young dogs - lesions may spontaneously resolve 

generalised - severe disease complicated by secondary bacterial infection 

diagosis = deep skin scrapings, trichograms 

treatment = can be difficult

• macrocyclic lactones

• isoxazoline

• amitrax washes 

non-burrowing mites

3 genera

• otodecetes cynotis

• cheyletiella spp

• trombicula autumnalis

otodectes cynotis

deep in ear, feeding on debris near ear drum

life cycle - transmission is direct by ear contact. life cycle ~ 3 weeks

clinical signs

• in cats often a brownish wacy exudate with crusting

• causes intense itching with head shaking

• secondary bacterial infection can result in purulent otitis externa - dark brown exudate. 50-80% of such cases associated with otodectes cynotis

treatment

• isoxazolines

• various drops

• imidacloprid, selamectin spot ons

treat all in-contact dogs and cats in household

cheyletiella spp

commensal of dogs, cats and rabbits

common cause of mild scaling dermatosis 

mites seen among debris against dark background 

diagnosis - mite shape, palpal claws. eggs also in superficial scrapings

zoonotic - mites will transfer to humans causing papules on arms and abdomen 

cheyletiellosis

lesions typically occur dorsally on rump and shoulders

common in rabbits

in dogs infestations possibly more prevelant in boxers and cocker spaniels 

control = no licensed products, fipronil, ivermectin 

trombicula spp

trombicula autumnalis in europe. only larvae are parasitic, peak abundance in autumn 

significance - puritis, erythema, papules, crusting, self-trauma. possibly associated with seasonal canine illness

diagnosis - difficult - mites often not seen

treatment - fipronil shown to be effective 

lice

order = phthiraptera

obligatory parasites of birds or mammals 

2 sub-orders = mallophaga and anoplura 

mallophaga contain the biting/chewing lice

anoplura contain suckling lice 

3 species = trichodectes canis, linognathus stetosus, felicola subrostrata

dogs - trichodectes canis - biting/chewing louse

small, yellow 1-2mm

dark markings on abdomen

claws for gripping hairs 

life cycle - same as for bovicola spp 

can survive off host for 7 days 

T. canis - pathology

harmful for puppies and old or neglected dogs

clinical signs

• head, neck and tail attached to base of hairs

• intense itching, scratching, biting at these sites feeding on scales and debris 

• matted coat, inflammation and excoriation 

• alopecia and bacterial involvement 

• dog may appear nervous 

vector for tapeworm dipylidium caninum 

transmission of dipylidium caninum

dogs - linognathus stetosus - suckling louse

clinical signs - skin lesions such as excoriation, miliary dermetitis or urticaria-like lesions and even necrtotic skin lesions have been described. may cause anaemia in heavy infestation 

diagnosis - head and neck areas. louse morphology. long eared dog breeds such as spaniel, basset and afghan hounds are particularly susceptible 

cats - felicola subrostrata - biting/ chewing louse

relatively rare

clinically signs 

• face, back and pinnae

• dull ruffled coat

• scaling, crusts and alopecia

distinctive triangular head 

cat and dog louse control

neonicotinoid - imidacloprid spot on

fipronil spray/spot on

sarolaner/ selamectin spot on 

tick classification

class = arachnida

subclass = acari

order = ixodia

family = ixodidae = hard ticks 

family = argasidae = soft ticks

how important are hard ticks

transmit pathogens - vector capacity similar to mosquitos

production losses due to tick-borne diseases in ruminants in developing countries

TBD in companion animals

dogs as resevoir hodtd for TBDs

all tick-borne diseases are zoonoses and/or clinically important in domestic animals

many emerging tick-borne diseases

ticks in UK

Ixodes ricinus

I. hexagonus

dermacentor reticulatus 

ticks in europe

Ixodes ricinus

I. hexagonus

dermacentor reticulatus 

rhipicephalus sanguineus

D. reticulatus

features of ixodes ricinus

ticks start to quest in spring

take refuge in undergrowth on hot days

2 main peaks in activity - spring and autumn 

feed on wide host range - birds, small mammals, deer, sheep, cattle, dogs, humans 

habitat - wooded area, upland pastures, scrub, sometimes urban gardens 

most abundant - transmit lyme disease, louping ill, red water, anaplasma, rickettsias 

3 host life cycles = 3 yrs in uk

blood feeding

female ticks can increase in weight >100-fold following engorgement and mating

ixodes hexagonus

known as hedgehog tick

rhipicephalus sanguineus

known as brown dog tick

highly adapted to feeding on dogs

transmits canine babesiosis and ehrlichiosis

has lateral projections on false head 

adapted to living in dog accomodation 

prefers ears, interdigital spaces, axilla

females drop off at night - thousands eggs deposited in crevices, cracks in dog kennel

huge number infect single dog but most are in environment 

can infest uk homes 

mainly southern europe 

dermacentor reticulatus

meadow tick

in europe transmits canine babesiosis

likes cool wet climates - extend northwards in europe - new populations in germany and southern uk

distinct silvery-grey scutum

club shaped palps

babesia of dogs and their vectors

babesia spp

• b.canis = dermacentor reticulatus

• b.canis(vogeli) = rhipicephalus sanguineus

• Ia = I ricinus - not a vector of canine babesiosis

• Ib = R. sangineus

• Ic = dermacentor spp

distrubution in uk

drivers of range expansion of ticks 

changes in climate throughout europe

vegetation increases support feeding hosts - roe deer to new habitats

new woodland habitat for deer and small animals

impact of connectivity and urban green corridors 

tick control

dogs

• permethrin and imidacloprid spot-on

• impregnated collar

dogs/cats

• imidacloprid(not effective against ticks by itself) and flumethrin collar

• fipronil spot on

• fluralaner 

in place for travelling dogs 

isoxazolines and ticks

latest products with very quick kill and can prevent pathgen transmission

claim = fluralaner prevents transmission of canine babesiosis and borrelia for 12 weeks 

• no product 100% effective

• non prevent all TBDs

• inspect and remove ticks asap