Ticks Flashcards
What is the importance of ticks?
Blood losses (large numbers anaemia)
Tick worry (prevent animals feeding)
Disease transmission
Tick paralysis (ascending motor paralysis)
Secondary infection / blowfly strike (at bite site)
Production losses (farm animals)
Hard ticks
Important in temperate and warmer climates
Hard dorsal covering on scutum
Prominent mouth-parts
Festoons may be present (bulges on posterior edges)
Ornate ticks have coloured patches
Body wall is convoluted to accommodate blood meal (esp. female ticks)
Soft ticks
More important in warmer climates
Absent scutum
Mouthparts not visible from dorsal surface
Do not swell much (feed little and often)
Mouthparts:
Palps - sensory organs
Chelicerae - puncture skin
Hypostome - tube for sucking blood, backward pointing teeth
Ticks feeding
Tick stands upright
Chelicerae cut through skin pool of blood
Hypostome inserted deep into skin
Mouthparts CEMENTED in place
Tick feeds continuously + injects saliva (contains substances that decrease host inflammatory response, ^ permeability of blood vessels -> free flow of blood)
Tick life cycle
eggs -> larva -> larvae -> nymphs -> adult
Hard tick life cycle
Classified according to number of different hosts to which they attach during their life cycle:
ONE-host ticks: each stage (larva + nymph + adult) feed on one host, e.g. Boophilus
TWO-host ticks: larvae + nymphs feed on one host; adult ticks on a second host, e.g. Hyalomma
THREE-host ticks: each stage feeds + develops on a different host, i.e. three hosts, e.g. Ixodes
Soft tick life cycle
NOT classified like hard ticks
Feed little and often on many hosts
Trans-stadial transmission
Infectious agent ingested during feeding by larva
Passed on from one host to the next (in 2- & 3-host ticks) as tick develops to nymph + adult
NOT passed onto next generation via the egg
Trans-ovarial transmission
Infectious agent is passed from one generation to the next through the egg, e.g. Babesia spp.
Ixodes spp. (3-host hard tick)
Worldwide
I. ricinus, most important tick in UK
Distribution: western UK (mainly)
Wide host range
Vector for HUMAN disease: Lyme disease (humans, dogs)
Vector for ANIMAL disease: Bovine babesiosis, louping ill, tickborne fever & tick pyaemia
Paralysis in humans, dogs (warmer climates only)
Ixodes ricinus epidemiology
THREE-host tick
Life cycle: 3 years (range, 2-7 years)
Ticks feed for a few DAYS each year
MOST of the time – on the ground
Need high Relative Humidity (RH) (>90%) – in matted vegetation (e.g. rough grazing, hedgerows)
Tick activity seasonal, e.g. spring
Dependent on temp and rh
Amblyomma spp. (3-host tick)
Warmer climates, worldwide
Vectors for heartwater (Cowdria ruminantium, Africa); also, Q-fever, Rocky Mountain Spotted fever in southern USA
Boophilus spp. (hard 1-host ticks)
Warmer climates worldwide, except Europe
Vectors for Babesia and Anaplasma spp. in cattle
Dermacentor spp. (hard 3-host ticks)
Vectors for:
viral (tickborne encephalitis, Colorado tick fever),
rickettsial (Rocky Mountain Spotted fever, bovine anaplasmosis),
bacterial (tularaemia) and
protozoal (babesiosis) diseases
Hyalomma spp. (hard 2/3-host ticks)
Warmer climates, Old World
Wide host range
Vectors for Theileria and Babesia spp.
H. aegyptium found on tortoises (Africa; pet shops, UK)
Rhipicephalus spp. (hard 2/3-host ticks)
Warmer climates worldwide
Vectors for Theileria parva (East Coast Fever), Babesia bigemina (ruminants, Africa), B. canis, Ehrlichia canis (canine pancytopenia)
Paralysis in livestock
Argas spp. (soft tick)
Infect birds in warmer climates (also humans)
A. persicus, poultry tick (or “tampan”), lives in crevices in poultry houses
Feeds at night production loss + death (large numbers)
Found on migratory birds in temperate regions
Principles of tick control
Integrated parasite control: Parasite control programmes that do not rely solely on drug treatment
Methods of tick control 1
Killing ticks on the ground -
By altering microclimate: pasture improvement, e.g. cultivation, drainage
By starving: “spelling” pasture (livestock removed); useful only if ticks don’t feed on other hosts
By burning: e.g. during dry period before rainy season
Methods of tick control 2
Separate host from infection-
Stock management: remove stock from tick-infected areas when ticks are active
Fencing: fence off infested pastures
Methods of tick control 3
Kill ticks on host-
Acaricides: dipping, spraying, pour-on formulations
Methods of tick control 4
Enhance host resistance-
Stock hybridisation: e.g. Bos indicus (humped breeds) x Bos taurus (European breeds). Heritability of resistance to ticks is higher in humped breeds than European breeds
Vaccination: a vaccine is now used in Australia for Boophilus microplus control -> raises antibodies against “hidden antigens” in the tick’s gut
