Ticks and tick borne pathogens

Question 1

Why are ticks not insects?

Answer 1

Arthropods because they have 9 legs not 6

Question 2

How long does it take an Ixodes tick to complete a blood meal?

Answer 2

About a week

Question 3

What do ticks feed on?

Answer 3

Obligate blood feeders, both male and female.

Question 4

Which part of the mouthparts is used to drill into the flesh?

Answer 4

Chelicerae.

Question 5

How does the tick anchor into the dermis?

Answer 5

Hypostome

Question 6

What do the palps do?

Answer 6

Sense and direct the mouthparts.

Question 7

What is the deer tick (UK)?

Answer 7

Ixodes rhicinus

Question 8

How can tick ectoparasites damage animals?

Answer 8

• Holes in hide, decreased productivity
• Tick worry, scratching
• Blood loss, may lead to immunosuppression
• Tick paralysis from toxins (neurotoxins released in late feeding stages)

Question 9

What is tick paralysis?

Answer 9

Where toxins such are released in late stage feeding. Can cause delayed allergic reactions e.g. alpha gal syndrome where alpha -1,3- galactose in tick saliva mimics alpha galactose in meat causing a delayed allergic response to eating red meat.

Question 10

Why are generalist ticks more likely to spread infection compared to host specific ticks.

Answer 10

Having multiple hosts rather than all stages on one host means that more different bloodmeals are taken, enhancing the probability of picking up and transmitting an infection.

Question 11

Name two species causing relapsing fever.

Answer 11

Borrelia duttoni and borrelia recurrentis

Question 12

What transmits borrelia recurrentis?

Answer 12

Body lice (pediculus humanus)

Question 13

What transmits borrelia duttoni?

Answer 13

Soft ticks

Question 14

Why is borrelia duttoni thought to be zoonotic?

Answer 14

Controversial studies suggesting ornuthodoros ticks feed on pigs which act as a reservoir

Question 15

What is eschar necrosis?

Answer 15

A symptom of spotted fever (rickettsia)- slough or piece of dead tissue that is cast off from the surface of the skin

Question 16

How can rickettsia be transmitted?

Answer 16

Can be transovarial. By Rhipicephalusand amblyomma species.

Question 17

What kind of virus is Crimean congo haemorrhagic fever?

Answer 17

Negative sense RNA virus, bunyavirus.

Question 18

What is the presentation of Crimean congo haemorrhagic fever?

Answer 18

Disseminated throughout body and associated with endothelial vessels. Changes permeability of vessels causing leakage and systemic shock (high mortality).

Question 19

How can CCHF be amplified?

Answer 19

Astymptomatically infects livestock which can act as a reservoir for amplification.

Question 20

What causes East Coast fever?

Answer 20

Theileria parva, an apicomplexan haemoparasite

Question 21

What is the presentation fo east coast fever?

Answer 21

• Fever
• Enlarged lymph nodes
• Anorexia
• Nasal discharge

Question 22

How is east coast fever controlled?

Answer 22

Innoculate then treat with vaccine (oxytetracycline treatment at same time as parasite innoculation) –> effective!

Question 23

Which ticks spread Theileria annulata? How is it treated? How are strains spread?

Answer 23

Hyalomma.
An attenuated vaccine.
Strains exchanged between water buffalo and cattle (reside in lymphocyte and erythrocytes).

Question 24

How does heart disease present?

Answer 24

• Decreased blood pressure due to oedema around heart and lungs (heartwater)- vascular endothelial (and lymphocytes) targeted.
• Circulatory failure
• Neurological manifestations

Question 25

What causes heartwater?

Answer 25

Ehrlichia ruminatium

Question 26

How is heart water treated?

Answer 26

Oxytetracycine Vaccine - infected sheep blood injected into cow and treated with oxytetracycline (not good tho- expensive and hard to store)

Question 27

How is African swine fever transmitted? How is it controlled? What are the symptoms?

Answer 27

Directly pig to pig. Maintained by wild bushpig populations (wild pigs don't get sick). No vaccine available but can be controlled through culling. Is a haemorrhagic fever- fever, coughing, difficulty breathing, haemorrhagic etc.

Question 28

How does deer population affect tick abundance?

Answer 28

Thought that increasing deer populations can contribute to the increasing abundance of ticks because they are amplifiers. Deer correlate with tick populations and can move ticks from place to place. Bring ticks to a place and increase their numbers.

Question 29

Why may two areas with similar densities of ticks have different levels of borrelia?

Answer 29

Not always lymes where there are ticks! -Different wildlife capacity to carry borrelia (deer amplify ticks but dont carry borrelia whereas grey squirrels can carry borrelia) -

Question 30

What is the causative agent of Lyme disease?

Answer 30

Borrelia burgdorferi

Question 31

Describe the relationship of density of borrelia with an increasing proportion of incompetent hosts. Explain

Answer 31

Increases to an optimum then decreases. | Crashes when there are too many incompetent hosts.

Question 32

What determines borrelia prevalence?

Answer 32

- Temperature some studies suggest W and S Scotland had increased prevalence due to climatic factors, other studies showed no correlation - Temperature may increase tick questing - Increase in sun temperature and decrease in rain increases ticks which may increase borrelia

Question 33

What is the equation for infection prevalence?

Answer 33

=Inversely proportional to deer prevalence OR nymph density

Question 34

Why is borrelia prevalence hard to predict in an area?

Answer 34

Changes from year to year due to local determinants.

Question 35

Do we need to worry about human exposure hazard if biting is low?

Answer 35

May have an increase in cases if more people start going to areas where there are ticks and exploring.

Question 36

Which stage of ticks are most important for lyme transmission and why?

Answer 36

Nymphs. Blood feed but are small and are therefore often undetected

Question 37

What are the symptoms of acute lymes?

Answer 37

Bullseye rash, flu, fever

Question 38

What are the symptoms of late lymes?

Answer 38

- Arthritis (damage to synovial joints). - Neurological sequelae (similar to MS and often misdiagnosed as Bell's palsy). - Acrodermatitis chronica atrophicans (ACA)- red blue lesions (most common symptom of chronic lyme disease).

Question 39

How do we diagnose lyme disease? Problems?

Answer 39

Need accurate lab diagnosis. ELISA coupled with western blot --> 2 tier serological test. Concern over assay specificity which may cross-react. May not pick up all true positive.s

Question 40

Does borrelia antigen switch?

Answer 40

Has been observed in chronically infected MICE.