Parasitology: Ectoparasites Flashcards
What is an ectoparasite
An organism that spends part or all of it’s life on the outside of the host animal from which it benefits (at expense of host)
Either:
Damage host directly
Host causes damage due to irritation
Act as carriers of some other pathogen
Ectoparasite groups
1. Arachnids: Mites Ticks 2. Insects: Flies Lice Fleas
Arachnids
Two body parts
Four pairs of legs
Different lengths
Lifecycle length
Feed on blood, skin debris /cells
Arachnid Lifecycle
Egg >Larvae >Nymph >Adult
Ticks can be one-, two-, or three-host feeders. In one-host species, all stages live and moult on the same host, then eggs are laid on the ground. In two-host species, larvae and nymphs share the same host, but the adult stage reproduces on a separate host. In three-host species, all three stages target different hosts; eggs are laid on the ground.
The life cycle of ixodids can take from 1 to 6 years and involves 4 stages: egg, larva, nymph, and adult. After hatching, the larva seeks a host, feeds and then drops off to moult to the nymphal stage. The nymph then seeks another host, feeds, drops off and moults to the adult stage.
Insects
Three body parts Three pairs of legs \+ / - wings Feed on: Secretions Blood Skin debris / cells
Insect Lifecycles
Egg >Larvae >Pupa> Adult
Effects of ectoparasite infestation
Irritation / annoyance
Damage to skin / hide / fleece
Itching, shaking, bleeding, smell, hair loss / alopecia, infection,
Lesion damage predisposes to blowfly (another ectoparasite!)
Seasonal itching
Bites / wounds (painful!) and possibly anaemia if blood sucking
Disease transmission – vectors and 2ndry bacterial infections
Allergic reactions to saliva / faeces of ectoparasites
Myiasis = Infestation of a living animal with larvae of dipteran flies
Blowfly strike
Eggs laid on host
Larvae hatch and feed on host skin
Additional risk of vector-bourne diseases:
Protozoa e.g. Babesia,
Bacteria e.g. Rickettsia, mastitis, conjunctivitis, Bartonella henselae
Viruses e.g. Louping ill, feline leukaemia virus
Endoparasites
Which endoparasite is transmitted by common insect ectoparasites of dogs and cats?
Zoonotic risks of exoparasites
Humans as: Definitive host Accidental host Vector-bourne diseases: Bartonella henselae Rickettsia Lyme’s Disease Louping Ill Equine encephalitis from biting (not UK yet…)
Chemical control of Ectoparasites
Macrocyclic Lactones Organophosphates (OPs) Synthetic pyrethroids (SPs) Repellents Dipping Showers Weekly bathing with specific product Spot ons and Pour ons Injectables
Resistance to chemical control
Resistance is a selection process that occurs as a result of exposure
More frequent exposure speeds up the process
Need to slow down resistance development:
Reduce use of ectoparasiticides
Target treatments and preventions
Correct dosages applied – sublethal doses speed up development of resistance
Rotation of different classes of ectoparasiticides
Control of Ectoparasites
Isolate affected animals Remove eggs – comb, insecticide Dress lesions with appropriate insecticide Tailing, dagging Endoparasite control Remove manure from grazing and housing areas to remove insects Manure heap fermentation Temperature kills eggs and larvae
Remove breeding sites such as stagnant water or remove animals from breeding area
Insecticide or repellent impregnated ear tags, tail bands and halters
Screens to prevent insect access to housing
Electrocution grids to kill insects within housing
Fans to affect flight
Wash and treat all bedding, grooming tools, equipment, rugs,
Or leave unused for 3 weeks
The future of controlling ectoparacites
Use of natural predators of problem-causing ectoparasites?
Vaccines?
Determining ecto parasite infection
Examine skin
Skin scrape
Biopsy
Environmental traps for flies
summary of ectoparacites
Ectoparasites may inflict damage directly to host or spread other diseases
Lifecycles may involve long periods away from host animals or may be entirely on the host
Often the animals response to infestation exacerbates the condition
Prevention and control programmes essential to maintain health and welfare
