ENI - Ticks Flashcards
Outline how ticks feed
- Chelicerae cut hole in skin
- Hypostome enters hole, held in by backwards facing teeth
- Cement produced by some to increase hold
- Inject saliva
- Feed through hypostome
What is contained in the saliva of ticks?
- Vasodilators (leading to swelling)
- Anticoagulant
- Immunosuppressive proteins
- Neurotoxins in some
- Pathogens
What are the direct effects of ticks?
- Inflammation at attachment site
- Anaemia
- Tick paralysis from some ticks (Australia)
What are teh indirect effects of ticks?
- Biological vectors for protozoa, bacteria, viruses
Why are ticks usually biological rather than mechanical vectors?
Pathogen rarely survives moulting between feeds if mechanical transmission
List the most common tick species
- Ixodes ricinus
- I. hexagonus
- I. trianguliceps
- I. canisuga
- Haemaphysalis punctata
- Dermacentor reticulatus
- Rhipicephalus sanguineus
How can ticks be differentiated?
- Size, shape, colour, ornamentation
- Face: shape of head and mouth parts
- Back end: i.e. anal groove
Give a brief overview of Ixodes ricinus
- Most commonly seen in vet practice
- Castor bean tick
- Wide range of hosts incl. humans
Give a brief overview of Ixodes hexagonus
- Common in UK
- Hedgehog tick
- Also found on dogs
- Rarely on humans
- More selective than ricinus
Give a brief overview of Ixodes trianguliceps
- Not of veterinary importance
- Most common tick in UK
- ONly on wild rodents
- Nidiculous
- Important in epidemiology of some infections
Give a brief overview of Ixodes canisuga
- Infrequent and only in south UK
- Dogs and badgers
Give a brief overview of Haemaphysalis punctata
- SE England and Wales, widely in Europe
- Red sheep tick, ruminants, rabbits, humans
Give a brief overview of Dermacentor reticulatus
- W Europe, rarly UK
- W Wales, SW England if anywhere
- Dogs and other large mammals incl man
Give a brief overview of Rhipicephalus sangiuneus
- S Europe, cannot survive outsde in temperate climates
- Most commonly on dogs imported from Med
- May be found where kennels kept particularly warm
What is transstadial transmission?
Transmission between stages i.e. larva to nymph, nymph to adult
What is transovarial transmission?
Vertical transmission via eggs, so larvae are infected and infectious
Describe the life cycle of 1-host ticks
- Female lays eggs (not on host)
- Larvae hatch
- feeding, moulting on host
- Nymph
- Male and female reattach
- Feeding, mating
- Female drops off
- Lays eggs
Describe the life cycle of 2-host ticks
- Female lays eggs (not on host)
- Larvae onto first host
- Feeding, moulting on host
- Onto second host
- Feeding, mating
- Female drops off and lays eggs
Describe the life cycle of 3-host ticks
- Female lays eggs off host
- Larvae feed on first host, drop off
- Nymph moulting
- Feed on second host, drop off
- Adult moulting
- Male and female attach to third host
- Feeding and mating
- Female drops off and lays eggs
Where does mating take place?
On the host
Describe nidiculous ticks
- In the nest of host
- When not feeding, tick stays in teh host’s nest/burrow
- Most Argasid ticks, have multiple nymph stages
Describe non-nidiculous ticks
- When not feeding are in open environment
- Fall off wherever host happens to be when tick finished feeding
- May “quest” to find host, or wait for host to pass by
- Usually long grass, moorland areas, low shrubby terrain
- Each stage in life cyce may have different host species
Compare hard and soft ticks
- Soft: soft leather bodies, legs hidden under tick, usually on birds
- Hard: scutum covers whole of back in males
Compare the scutum of male and female hard ticks
- Female hard tick scutum only covers half of body
- Will cover less as she feeds and swells
- In male covers whole back
Describe soft ticks
- Argasidae
- Most are nest parasites
- Swell when take on blood meal
- Lots of nymph stages
Describe Argas persicus
- Fowl tick
- Soft
- Poultry and wild birds
- Lead to anaemia, debilitation, loss of production, weight loss, paralysis
- Red spots where ticks fed
- transmission of pathogens
Give an example of a pathogen transmitted by Argas persicus
Borrelia anserina
Explain how Argas persicus can be mechanical vectors
- Do not have to moult before feeding
- Feed during night,, drop off host, lie in nest and latch on again at night
Describe teh life cycle of Argas persicus
- Females lay eggs several times during lifetime
- larvae feed on birds for 2-7 days then drop off into nest
- 2-7 nymphal moults before adult stage
- Nymphs and adults feed at night for short period, then drop off
- Feed several times during each life stage
Describe the general life cycle of Ixodidae
- Females feed on host, males not so much
- Male on host for mating
- Single larval stage, single nymphal stage
- Larvae feed on small rodent
- Nymphs feed on larger mammal
- Adults on large mammals e.g. dogs, humans, deer (but may also be rodent at each stage)
Describe questing
- Follow concentrations of CO2 to find hosts
- Crawl up stems of grass or edges of leaves with front legs exteneded
- Ready to climb onto passing host
Give examples of diseases spread by Ixodid ticks
- Tickborne fever
- Tick pyraemia
- Lyme disease
- Louping ill
- Babesiosis
- Theileriosis
Describe Tickborne fever
- Anaplasma phagocytophilum (rickettsia)
- Affects white blood cells
- Transstadial
- Wide range of species affected
- Mostly by Ixodes ricinus
- cauases fever, immunosuppression, occasional haemorrhagic syndrome (and Human granulocytic Ehrlichiosis in North America)
Describe the role of Ixodes trianguliceps in the spread of tickborne fever
- Spreads Anaplasma around rodents
- These then pass it on to Ixodes ricinus
Describe tick pyaemia
- In lambs 2-12 weeks old
- Immunosuppressed by anaplasmosis
- Staphylococcus aureus introduced through bite wounds, umbilicus etc
- Leads to abscesses anywhere (liver, lung etc) incl joints
What is the causative agent of Lyme disease?
Borellia (esp. B. burgdorferi_
Describe Lyme disease
- Distinct circular rash “bullseye”
- Flu like symptoms, tiredness fatigue), muscle pain, joint pain, headaches, high temeprature (fever) chills and neck stiffness
- More serious symptoms can develop long time later
- Readily treated with antibiotics
How can Borrellia spp. be transmitted within ticks?
- Transtadial
- Transovarial
What is Louping ill?
Infectious ovine encephalomyelitis
Describe Louping ill
- Mainly sheep and grouse
- Upland areas
- Closely related to tickborne encephalitis virus
- Infects CNS
- Significant suffering
Describe control of Louping ill
- Voluntary
- Use of acaricides
- licensed inactivated vaccine against virus
Describe tick to tick transmission of Louping ill
- Via dendritic cells of host
- Dendritic cells pick up salivary Igs
- Drawn to neighbouring tick
- Transmit virus to next tick
Describe Babesiosis and Theileriosis
- Similar to protozoans causing malaria and sleeping sickness
- Parasitise red blood cells of vertebrates
- Transovarial and transstadial transmission
Describe the diseases caused by Theileria
- T. annulata (tropical)
- T. parva (East Coast Fever)
- Cattle disease in Africa
- Found in local bovids, cause little disease
- Severe disease in domestic cattle
- lymphadenopathy, fever, haemorrhages, anorexia, collapse, pulmonary oedema, dyspnoea, death
Describe the diseases caused by Babesia
- Pyrexia, severe haemolytic anaemia, haemoglobinuria
- Potentially death of infected animals
- Commonly known as Red Water Fever in cattle
What species of Babesia are spread by Ixodes spp?
- B. divergens (Ixodes ricinus)
- B. microti
What species of tick is reponsible for the spread of B. bovis?
Rhipicephalus sp
What ticks spread B. canis?
- Dermacentor spp.
- Rhipicephalus spp.
Outline the key points of Ixodid tick control
- Dips, sprays, pour ons, collars, ear tags etc
- Long trousers, boots, long sleeved shirts
- Control of ticks on wildlife and environment not practical
- Remove tick asap as pathogens transmitted only after feeding for a while
- vaccination
Which tick borne infections can be vaccinated against?
- Lyme disease in dogs
- Louping ill in sheep
Which types of tick (soft/hard) can have festoons?
Hard
Where are the mouth parts located in hard and soft ticks?
- Hard: dorsal
- Soft: ventral
What makes ticks hard to manage?
- Not host species restricted
- Live longer than flies, can starve for many years
- Good mouth parts with salivary secretions where many components unknown to us
How can the larval and nymphal stages of ticks be distinguished from adults?
- Larval: 3 pairs of legs instead of 4, paler scutum
- Nymph: paler and softer scutum, 4 pairs of legs
Which genus of ticks have festoons?
- Haemaphysalis
- Hyalomma
- Rhipicephalus
- Dermacentor
- i.e. hard ticks except ixodes
Which genus of ticks have anal groove anterior to anus as opposed to posterior?
Ixodes
Which genus of tick have triangular pedipalps?
Haemaphysalis
Which genus’ of tisk have non-triangular pedipalps?
- Ixodes
- Hyalomma
- Dermacentor
Which genus of ticks have long pedipalps?
Hyalomma
Which genus’ of ticks have short pedipalps?
- Haemaphysalis
- Rhipicephlus
- Dermacentor
Which genus of ticks has hexagonal basa capituli?
Rhipicephalus
Which genus of ticks has rectangular basa capituli?
Dermacentor
How can larval stages of ticks be distinguished from insects?
- Both have 3 pairs of legs
- However ticks (all arachnids) have 2 body parts, insects have 3
