6.2 Arthropods 2 Flashcards
Siphonaptera
Fleas
Siphonaptera - Fleas; hosts
- Ctenocephalides (dog and cat fleas)
- Echidnophaga (sticktight flea) - poultry
- Pulex irritans- primarily people
- Tunga penetrans (chigoe flea) - primarily people
Hosts are preferred but some have cosmopolitan tastes
Siphonaptera - Fleas; General Characteristics
- parasites of the skin
- sometimes permanently attached
- wingless, laterally compressed
- long legs - excellent jumpers
- may have genal or pronotal combs (ctenedia)
Siphonaptera - Fleas; General Life Cycle
- complex metamorphosis
- eggs not attached to hosts
- larvae and pupae in environment
- adults may reside on host or move off and on for blood meals
- feed on blood as adults
Ctenocephalides spp.; what are they, what do they infect
Ctenocephalides felis (cat flea)
Ctenocephalides canis (dog flea)
* prefer cats and dogs but …
* surface-feeding ectoparasites of the skin
Ctenocephalides spp.; Morphology - Adults
- wingless, laterally compressed
- golden brown, up to 4 mm
- both genal and pronotal combs
Ctenocephalides spp.; Morphology - Larva
- worm-like (maggot-like) up to 5 mm
- brown head and well developed segments
- possesses anal struts which are two hook processes on the posterior end
- feed primarily on “flea dirt”
“Flea dirt”
- Undigested blood from adult fleas
- Primary food for larvae
Fleas - Ctenocephalides spp.; Morphology - Pupa
- soft, moist cocoon, up to 4 mm
- sticky – accumulates camouflage
Fleas - Ctenocephalides spp.; Morphology - Egg
- glistening, white
- 0.5 mm oval
Ctenocephalides spp.; Life Cycle
- complex metamorphosis
- eggs not attached to hosts, fall to ground
- may produce up to 2000 eggs per female
- larvae and pupae in favourable environment
- large numbers in “source spots”
Ctenocephalides spp.; “Source Spots” - Usually found where…
1) Dog or cat spends considerable time
2) Ample supply of “flea dirt”
3) Little or no human or animal traffic
Ctenocephalides spp.; Common source spots include:
- pet’s bedding
- under chairs or under cushions of chairs
- outdoors in moist, shaded areas without traffic (e.g. below raised decks)
Typical Cat Flea Colony; adults, pupae, larvae, eggs, total
Adults 250 (5%)
Pupae 500 (10%)
Larvae 1750 (35%)
Eggs 2500 (50%)
Total 5000
Ctenocephalides spp.; Pathogenesis and Clinical Signs
- irritation results from frequent bites and injection of salivary secretions
- range of responses
- no reaction to highly allergic with puritis and dermatitis
= Flea Allergy Dermatitis (FAD) - Flea Allergy Dermatitis (FAD)
- Hypersensitivity to bites
- Misery can result from only one or few flea bites
Ctenocephalides spp.; Diagnosis
- clinical signs of irritation - licking, chewing or scratching
- direct observation of fleas or flea dirt in heavy infestations
- brisk combing over a light coloured towel to collect flea dirt and eggs (even larvae and adults)
- “water test” the sample (look for blood in flea dirt) by dampening
the towel – red stains indicate blood in the combed material
Ctenocephalides spp.; Treatment, general
- changes to the infested environment
- insecticides of various sorts
Ctenocephalides spp.; Treatment - Environment
- frequent and thorough vacuuming
- dehumidifier in basement of affected house
- regular cleaning of bedding and other “source spots”
Ctenocephalides spp.; Treatment - Insecticides, 3 major types
- three (3) major types based on type of action
o insect growth regulators (IGR’s)
o quick knock down insecticides
o insecticides with residual activity
o newer adulticides
Ctenocephalides spp.; Treatment - Insect Growth Regulators (IGR’s)
(Insect Development Inhibitors)
- A) artificial hormones that interfere with flea larva pupation – e.g. methoprene
- B) Chitin inhibitor – e.g. lufenuron
- little or no toxicity to vertebrates - safe
- slow acting because it stops multiplication but does not kill existing adult fleas
Ctenocephalides spp.; Treatment - Quick Knock Down Insecticides
- often “botanicals” - pyrethrins and their synthetic counterparts, pyrethroids, sometimes with synergist piperonyl butoxide
- fast killing action
- short effective life - repeated applications
- generally in shampoos and sprays used directly on animals
Ctenocephalides spp.; Treatment - Insecticides with Residual Activity
- often carbamates and organophosphates
- slower killing action
- long effective life - repeated applications are not as necessary
- commonly found in collars as well as animal shampoos, topical spot cutaneous application and, especially, area sprays
Ctenocephalides spp.; Treatment – Newer Adulticides
- Imidacloprid (“Advantage” - an insecticide)
- adulticidal and larvacidal
- monthly topical application
- Selamectin (“Revolution” - endectocide, an avermectin)
- adulticide and prevents eggs from hatching
- monthly topical application
- has activity against a wide range of parasites in addition to fleas
- Nitenpyram (“Capstar”)
- Oral insecticide – neurotoxin
- fleas ingest poison when feeding
- short duration of activity – about 1 day
(no residual activity) - useful in some situations
Arachnida includes
mites, ticks, spiders
Class Arachnida; General Characteristics; hosts
- some parasites of the skin
- mites usually host specific
- ticks may have cosmopolitan tastes
- found on virtually all animals including humans
Life Cycle - Arachnida
Egg ⇒ Larva ⇒ Nymph ⇒ Adults
Class Arachnida; General Characteristics; morphology
*Body compact
*Capitulum or “false head”
o basis capitulum
o mouthparts
*4 pairs of legs
Ticks; Morphology
- Body compact with leathery cuticle
- Capitulum or “false head”
o basis capitulum
o mouthparts
o armed hypostome - 4 pairs of legs as adults
- Larvae look like adults but have 3 pairs of legs
- Nymphs look like adults with 4 pairs of legs but are not sexually mature
Ticks; Capitulum
- armed hypostome
- chelicerate mouthparts
- prominent palps
Ticks; Families
Family Argasidae - the argasids
* soft ticks
* four genera, eg. Argas, Ornithodorus, etc.
Family Ixodidae - the ixodids
* hard ticks
* many genera, eg. Ixodes, Rhipicephalus, Dermacentor, Amblyomma, etc.
Ticks; Family Ixodidae - the hard ticks; identifying factors
-Capitulum
o Terminal
o anterior
-Scutum
o hard dorsal plate
-(hence “hard tick”)
-Live outdoors
-Mammals are usual hosts
-Feeding takes several days
Ticks; Family Argasidae - the soft ticks; identifying factors
- Capitulum
o subterminal
o ventral - No scutum - hard dorsal
- Live in nests, burrows, buildings
- Found on both birds and mammals
- Feeding in minutes to hours by adults and nymphs
Ticks; General Life Cycle
- Eggs laid off of host
- All follow the general plan of egg to larva to nymph to adult but vary in the number of hosts used during the life cycle - simple metamorphosis
- All stages feed on blood
- Repetitive blood feeding makes these potential biological vectors of blood- borne pathogens
Ticks; One-host ticks life cycle
- larva attaches to host A and completes development to adult on the same host then drops off to lay eggs
Ticks; Two-host ticks life cycle
- larva attaches to host A, feeds, molts to nymph, feeds and then drops off to molt to adult; adult attaches to host B, feeds, then drops off to lay eggs
Ticks; Three-host ticks life cycle
- larva attaches to host A, feeds and drops off to molt; nymph attaches to host B, feeds and drops off to molt; adult attaches to host C, feeds and then drops off to lay eggs
Ticks; Multiple host ticks life cycle
- larvae attaches to a host (long feed) then drops off to molt; nymphs and adults return to the host repeatedly to feed
- all soft ticks are multiple host ticks
are multiple host ticks soft or hard?
- all soft ticks are multiple host ticks
Dermacentor spp.
Hard Ticks
Hard Ticks; Dermacentor spp.
Dermacentor andersoni (Rocky Mountain Spotted Wood Tick)
* western North America only
* biological vector of Rocky Mountain Spotted Fever (a rickettsial disease)
Dermacentor variabilis (American Dog Tick)
* North America east of Rockies
Dermacentor spp.; Adult Morphology
- ornate scutum, basis capitulum parallel sided, palps short
- festoons present, except in fed females
Dermacentor spp.; Life Cycle
- 3 host tick, long life cycle
- larvae and nymphs feed on small mammals, adults on dogs and other larger mammals
Rhipicephalus sanguineus; what is it, what does it affect, where is it found on the body
(Brown Dog Tick)
* primarily affects dogs but also other mammals
* adults found between toes and in ears
* larvae and nymphs at back of neck
Rhipicephalus sp.; Adult Morphology
- scutum inornate , basis capitulum angular, palps short
- festoons present, except in fed females
Rhipicephalus sp.; life cycle
- 3 host tick, 2 month from egg to adult
- unfed adults can survive extended periods
- all stages feed upon dogs
Ixodes spp.; hosts
- many animals have distinct Ixodes sp.
Ixodes scapularis; hosts, vector for what
(Deer Tick)
* larvae and nymphs on mice, adults on deer
* all stages will attach to other mammals, including humans
* biological vector for Lyme Disease
Ixodes spp.; Adult Morphology
- scutum inornate , basis capitulum parallel-sided, palps long
- festoons absent, anal groove anterior to anus
Ixodes spp.; Life Cycle
- 3 host tick, long life cycle (2 or more years)
- unfed adults and nymphs can survive extended periods and overwinter
Hard Ticks - All Genera; Pathogenesis/Clinical Signs
- heavy infections can cause blood loss and “tick worry”
- hair loss due to rubbing of affected areas
- “tick paralysis” or tick toxicosis caused by the salivary secretions of female hard ticks (usually Dermacentor or Amblyomma spp. in North America)
Hard Ticks - All Genera; Diagnosis
- finding the attached ticks on the animal
