Ticks, Mites, Fleas, Lice as a Vector

TICKS, MITES, FLEAS, &

LICE

Arthropode as vector

By Tri Wulandari K

TICK

Ticks, mite, spider and scorpion belong to the class Arachnida. Tick and mite belong to Order Acarina. The important point that ticks differ from mite in being larger and having toothed hypostome and not having claws on the palps.

Morphology Flatten dorsoventrally of body: capitulum and abdomen; Eyeless or

simple eye; Capitulum containing gnathosoma/mouthparts chelisera (to cut/bite), hypostoma (to attack), palps (to support).

Important Family 1. Argasidae (soft tick) Important species: Ornithodoros moubata 2. Ixodidae (hard tick) Important genera: Ixodes, Dermacentor, Amblyomma.

Haemaphysalis, Hyalomma.

Argasidae (Soft tick)

Morphology : Body: ovale, flatten dorsoventrally, integumen tough and leathery,

wrinkle and has tubercle, no scutum (dorsal shield) and capitulum situated ventrally difficult to sexing. Legs: Nympha and adult: 4 pairs of leg; larvae: 3 pairs.

Male and female has coxal gland osmoregulatory function. Female has Genes organ waxy secretion for eggs protection. Respiratory: by spiracle/stigmata (located on the margin of the body,

behind the last pair of leg).

Life cycle (hemimetabolous: 6-12 months) Eggs (300-500 eggs per laid) larvae nympha adult. Larva, nympha and adult feed blood in many host (multihost ticks). Adult: can live 15 years and 11 years without a blood meal. Breeding place: crack, crevices of wall, floor or furniture, mud, dust

and debris, rodents hole, and sleeping place of wild animal and bird.

Medical importance of soft tick

As vector of tick borne relapsing fever (caused by rickettsia Borrelia duttoni)

As vector of Q-fever (caused by Coxiella burnetti)

Other viruses: 30 arboviruses has known to be transmitted by ticks.

Transmission of tick borne

relapsing fever

Ingested rickettsia multiply in midgut of ticks pass across into haemocoel, multiply and spread in all tissue of ticks body: salivary, coxal organ and ovaries.

Transmission: through saliva, excrete of

coxal organ, trans-ovarial (3-4 generation)

Ixodidae ticks (Hard ticks)

Morphology Body :

ovale, flattened dorsoventrally (3-23 mm), there is festoon (rectangular indentation on margin of posterior abdomen) in Dermacentor, Rhipicephalus, and Haemaphysalis,

sclerotisation of ventral body, capitulum situated anteriorly, has no coxal gland.

Legs: adult and nympha : 4 pairs of leg; larvae 3 pairs

Mouth parts: club shape palps. Hypostome and denticulate chelicera enter to the host body

Sex dimorphism: size of female > male; scutum (dorsal plate) of male covered almost of doral surface, whereas in female small, located anteriorly: behind the capitulum.

capitulum

festoon

Life cycle (hemimetabolous) Eggs (thousands eggs are laid 3-6 days after feed

blood, located on the top of female scutum) larvae nympha adult

Larvae, nympha and adult stages feed blood for long periods (1-4 weeks) on their host.

After feeding blood to the ground and seek shelter under leaves, stone, debris, in the surface root of grasses or scrub, or buries itself in the soil questing (moulting and waiting for a suitable passing host)

Life span: 7 years

Special behavior and habits of hard ticks Multi-host specifics transmission of the

disease.

Larvae & nympha stages more active on feeding blood than adult.

Humidity of soil and vegetation can be important factor in tick survival (not very dry and not very wet soil is suitable condition)

3 types of host specifics : 3 Host (L- N- A) Ixodes, Dermacentor, Rhipicephalus,

Haemaphysalis

2 Host (L,N - A) Hyalomma, Rhipicephalus 1 Host (L,N,A) Boophylus

Note: L=larvae; N=nympha; D=adult; -= different host; ,=same host

Medical Importance of hard ticks

Tick paralysis By biting of Dermacentor, Ixodes and Amblyomma

The symptoms appear 5-7 days after biting (paralysis of motor nerves): acute legs paralysis ascending cannot walk or stand, difficult in speaking, swallowing and breathing recovery in a few weeks or death.

As vector of Arboviruses Russian Spring-Summer Encephalitis (I. persulcatus, H.

concinna)

Tick Borne Encephalitis (I. ricinus, D. marginatus, Haemaphysalis sp)

Omsk Haemorrhagic Fever (Dermacentor, Ixodes) Kyasanur Forest Disease (H. spinigera) Crimean-Congo Haemorrhagic Fever (Hyalomma marginatum,

D. marginatus)

MITES

There are 2 important Families Sarcoptidae & Trombiculidae

SARCOPTIDAE Important species is Sarcoptes scabiei

causes scabies (have discussed in

SENSORY BLOCK)

Trombiculidae (scrub typhus mite)

Parasitic stage larvae also called red bugs/chiggers/scrub typhus mite.

Morphology : size : larvae 0,5-1mm; adult 1-2 mm, capitulum situation anteriorly. (A) : 4 pairs of leg, covered with red feathered hairs velvety

apparence.

(L) : 3 pairs of leg, reddish/orange/ pale yellow, covered with many long hair.

Dorso-anterior: pentagonal/rectangular scutum with 306 setae and a pair of eyes.

Life cycle Eggs (4-7 days) deutovum (ovum containing larvae) (5-7 days)

larvae deutnympha trithonympha (adult) Larvae becomes very active, climb up grasses and suck the lymphatics

fluid of rodents, birds and human.

Preference site : soft and moist skin (ears, genitalia, around anus) Life span usually 40-75 days, but may be 8-10 months

Medical importance of scrub typhus mite

Nuisance Intense irritating and itching due to its biting (harvest bug

itch, autumnal itch, scrub itch) Neotrombicula autumnalis, Eutrombicula alfredugesi

As vector of Scrub typhus Also called mite borne typhus, Japanese river fever,

chigger borne rickettsiosis, tsutsugamushi disease

Caused by Rickettsia tsutsugamushi

Vector : Leptotrombidium deliensis, L. akamushi, L. fletcheri

Transmission the disease was very close association between: Leptotrombidium mite wild rodents vegetation R. tsutsugamushi.

FLEAS

(Siphonaptera)

There are 2500 species, 94% biting mammalia (including human)

Worldwide distribution, some species centered at several area.

Morphology :

Body: Relatively small (1-4 mm); Colour: light dark brown, compressed laterally; Absent of wing, 3 pairs of legs (third legs for jump); almost all of the body covered with bristle and small spines.

Head: triangular, black or eyeless, 3 segments antennae which lie in the sulcus behind the eyes. Suckingblood type of mouthparts which point downwards. There is genal combs or combless.

Thorax : 3 segments: pro-meso-metathorax ; there is pronotal combs or combless. Xenopsylla sp. mesopleuron was devided into 2 by meral rod.

Abdomen : Sexing: The tip of abdomen of female more rounded than male and there is spermatheca in female. It is not important to distinguish of both sexes all suck blood important in transmission of the disease.

Specific Morphology: The available of bulbous proventriculus which provided internally to prevent the regurgitation of blood meal into oesophagus this organ is important in the mechanism of plague transmission.

Life cycle of Flea

eggs (in crack, crevious, debris floor) (2-4 days)

larvae (2-3 moulting) pupae (7-14 days) adult

Medical importance of flea

Flea nuisance Cat and dog flea (Ctenocephalides felis and. Ct. canis), Human flea (Pulex irritans), Chicken flea (Ceratophyllus sp.) Tunga penetrans (tungiasis)

Vector of Plague Xenopsylla cheopis, X. astia, X.brasiliensis, Pulex irritans

Vector of Endemic typhus X. cheopis, Nosopsyllus fasciatus, Ct. felis, Ct. canis, P.

irritans.

Intermediate host of Cestode Xenopsylla sp., Nosopsyllus sp. H. diminuta, D. caninum, may H.

nana Vector of other disease (minute)

Tularemia (Francisella tularensis), Rickettsia conori, Coxiella burnetti.

FLEA AND THE DISEASE

Plague

The disease

caused by Pastuerella pestis also called Yersinia

pestis or Bacillus pestis,

transmitted by Fleas biting,

the main host is Rodents especially rats

See more information about

plague in Textbook of Microbiology

Pattern transmission of plague by flea

Plague bacilli sucked up by blood meal pass to the stomach and multiplication in there extend towards to invade the

proventriculus blocking function of proventriculus regurgitating plague bacilli from previous feed infect to the new host by direct contamination from the fleas mouthparts.

Partially regurgitation makes fleas becomes starved soon get blood meal transmission

Contact between contaminated fleas faeces with mucosa surface or abrasions skin. (Infected flea can remain bacilli as long as 3 years).

Inhalation of droplets (in pneumonic plague: human to human, insect are not involved)

FLEA AND THE DISEASE

Endemic Typhus

Also called murine typhus ; caused by Rickettsia typhi (mooseri).

In this disease: multiplication of bacteria occurs in intestinum of flea, but not cause blocking of proventriculus infection only through direct contact between contaminated faeces of flea and crashing skin or mucose surface. (dry contaminated faeces can remain infected 4-9 years).

Order Anoplura (Pthiraptera): LICE

There are 3 types if human lice:

Pediculus humanus capitis

Pediculus humanus corporis

Pthyrus pubis

Only Pediculus humanus corporis can transmit the disease)

Morphology Body:

small, greyish, wingless insect. Flattened dorso-ventrally body, with soft leathery integument.

Legs: 3 pair of legs

Mouthparts: flexible almost tube-like mouth (haustellum)

Sex differentiation: female: bifurcatio; male: rounded

Life Cycle (hemimetabolous) Eggs (called nit) (6-9 per day, firmly on hairs of bady or

clothes)(7-10 days) nymph (7-12 days) adult

Life span of female is 1 month (laid 200-300 eggs)

Nymph and adult take blood meal at day and night

Spreading direct contact with infested clothes

Medical importance of body lice

Pediculosis Repeated injected saliva of lice to

harbouring person toxic effects: weariness, irritability, pessimistic mood, feel lousy.

Large numbers of body lice infestation vagabonds disease (pigmented and tough skin)

Allergies

As vector of Louse borne typhus/ epidemic typhus

(Rickettsia prowazeki)

Trench fever (Rickettsia quintana) Louse borne relapsing fever (Borrelia

recurrentis)

Feeding Behavior and Transmission of

Disease

Lice are attracted to the host by warmth and odours.

They are permanent ectoparasites, capillary feeders who suck blood about every 23 hours.

The ingested blood is stored and digested in midgut, followed by the hindgut.

The saliva causes itching and the resulting scratches secondary bacterial infections. Louse feces induces the first irritations.

Only P. h. corporis can transmit the disease (experimental is possible using Phthirus pubis).

Epidemic typhus and louse borne

relapsing fever

Classical epidemic typhus (caused by Rickettsia prowazekii ) transmitted only among humans by pathogens present in the deposited

feces

These pathogens invade through skin lesions or are inhalated. The pathogens are infective in the faeces for up to three months.

Interaction of Vector and Parasite If the lice suck blood within the first ten days of illness, R. prowazekii is

transmitted and multiplies in the lumen of the gut and also in the cells of the intestinal wall.

R. prowazekii is pathogenic to lice due to the destruction of gut cells. In the other bacterial infections no pathogenic effects are reported.

Borrelia recurrentis invades the haemocoel of the insect about four days after ingestion, slowly multiplying there.