Mites & Ticks of Veterinary Significance

Question 1

what is the phylum, class, order of mites and ticks

Answer 1

phylum: arthropoda
class: arachnida
order: mites and ticks (acarina)

Question 2

why are mites and ticks important to health and welfare (6)

Answer 2

1. they cause forms of allergic dermatitis associated with pruritis that is often intense
2. they cause irritation and restlessness
3. their larvae can invade the body of an animal and cause tissue destruction
4. some are obligate blood feeders and can cause anemia
5. they are very effective at transmitting agents of infectious disease so act as vectors (biological or mechanical)
6. they can be difficult to control

Question 3

what are examples of allergic dermatitis

Answer 3

1. mange (mites): psoroptes ovis (sheep scab), sarcoptes scabei (sarcoptic mange, dogs), demodex canis (red mange, dogs)
2. FAD: flea allergic dermatitis (ctenocephalides felis/canis)
3. pediculosis (louse infection, cattle/sheep)

Question 4

what is sheep scab caused by

Answer 4

psoroptes ovis a non-burrowing mite

highly contagious, severe and debilitating form of mange

Question 5

is psoroptic mange notifiable

Answer 5

yes in scotland

Question 6

what is the pathogenesis of psorptes ovis

Answer 6

caused by allergic (type 1 hypersensitivity) reaction to mite anitgens

generates inflammation and serous exudate –> dries to form scab surrounded by moist border and inflammed skin –> mites active in scab border –> population expands & scabs extend

pruritis causes excessive rubbing, loss of wool & exocriation

Question 7

what are the clinical signs of sheep scab

Answer 7

lighter wool is first visible sign (usually over shoulders)

restless, rub and scratch (wool becomes ragged/stained)

large areas of wool loss along with open bleeding wounds and thickened skin

reduce weight gains –> weight loss and sometimes death

Question 8

how is sheep scab diagnosed

Answer 8

when handled –> easily elicit nibbling relfex

part wool and look for: crusty lesions of scab

skin scrapings from edge of lesion (10% KOH and identify mites)

Question 9

what mange is caused by a burrowing mite

Answer 9

demodex canis

Question 10

what is the pathogenesis of demodex

Answer 10

live in sebaceous glands and hair follicles

Question 11

how is demodex diagnosed

Answer 11

deep skin scraping

Question 12

what do demodex look like

Answer 12

elongated/cigar shaped

4 pairs of stumpy legs

Question 13

what does transmission of demodectic mange need

Answer 13

transmission requires prolonged contact

Question 14

what are the features of demodectic mange

Answer 14

most animals get mild localized mange –> slight hair loss/thickened skin

not usually pruritic

may resolve spontaneously

Question 15

what is generalized demodecosis associated with

Answer 15

genetically inherited immunodeficiency

Question 16

what does generalized demodecosis cause

Answer 16

squamous alopecia, desquamation and skin thickening

Question 17

hat occurs when demodecosis is pustular

Answer 17

bacterial invasion of lesions

thickened skin with small pustules

ooze serum, pus, blood, erythema

hyperpigmentation –> red mange

severe disfigurement

requires prolonged treatment

Question 18

what obligate blood feeders cause anemia

Answer 18

heavy infestations required

ticks

dermanyssus gallinae –> non-burrowing, red mite of poultry

horse flies –> intense attacks

keds –> heavy infestations lead to anemia

Question 19

what are examples of

Answer 19

1. many flies –> midges, sandflies, tetse flies
2. fleas
3. ticks –> bacteria, parasites, viruses

Question 20

what is Ixodes ricinus

Answer 20

european sheep tock

I. ricinus is an ectoparasite of all mammals and birds

Question 21

how are different species of ticks identified

Answer 21

morphological features

ixodes has anterior anal groove

desmacentor is ornate

i. ricinus is inornate, overlapping spur
i. canisuga no overlapping spur (vestigal)
i. hexagonus has spur but does not overlap

Question 22

what is the lifecylcle of I. ricinus

Answer 22

an efficient vector because all stages are obligate blood feeders and feed on multiple hosts in the lifecycle

year 1: larvae quest for host attach and feed for 6 days –> drop to ground and moult to nymphs

year 2: nymphs quest, attach and feeds 6-8 days –> drop to ground and moult to adults

year 3: adults quest and attach –> male and female mate on host –> female feeds for 14 days –> females drops to ground and lays thousands of eggs

lifecycle takes 3 years and requires 3 separate hosts

Question 23

what is the pathogenic significance of I. ricinus

Answer 23

secondary infection of lesions can cause disease

1. blow fly strike (sheep) –> tissue destruction/anorexia
2. tick pyameia –> staphylococcus –> septicemia/abscesses/arthritis

Question 24

how does Ixodes ricinus transmit significant microbial pathogens

Answer 24

1. red water (protozoa) –> B. divergens –> fever/anemia/hemoglobinuria
2. tick-borne fever (sheep/cattle/goats/dogs) –> anaplasma (rickettsia) –> fever/abortion
3. louping ill (viral) (sheep/cattle/grouse) –> flavivirus –> encepahalitis/abnormal gait/death
4. lyme disease (bacterial) (dogs/horses/cattle) –> B. burgdorgeri –> persistent fever/arthritis/lameness

Question 25

what is squamous demodecosis

Answer 25

alopecia, desquamation and skin thickening