Vector

1. Class Arachnida
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Arachnida:
• Contains 3 orders of medical importance:
1. Parasitiforms (Ticks)
2. Acarina (Mites)
3. Araneida (Spiders)
Characteristics:
 Body is divided into cephalothorax & abdomen,
 Adults have 4 pairs of legs,
 Wingless, Antennae absent,
 Undergo incomplete metamorphosis,

2. Arachnida . . .
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Order Parasitiforms & Suborder Ixodida,
• Includes three families:
1. Ixodidae (hard ticks),
2. Argasidae (soft ticks),
• There are an estimated 820 species of ticks
in the world, of which over 90 occur in the
continental U.S.
• About 80 species are in the family Ixodidae,
known as “hard ticks,” and
• About 10 species are in the family
Argasidae, known as “soft ticks."
How Many Kinds of Ticks Are There?

3. Arachnida . . .
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• Ticks are chelicerates with 4 pairs of legs,
 Palps & mouth parts form the chelicera,
• Body is divided into two functional units:
 Gnathosoma (Capitulum), which carries
the chelicera, palps & mouth,
 Idiosoma, includes legs, brain, digestive
and reproductive structures,
Morphology

4. Arachnida . . .
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Biological features:
• Obligate parasites where all active instars are blood feeders.
• Non permanent parasites; find a new host every time they feed.
• Many species live for 2-4 years or >10 years,
• Unfed ticks may survive for more than a year; off-host.
• Wide host range with passive host searching strategy,
i.e. waiting, climbing on, attaching and feeding,
Ticks . . .

5. Arachnida . . .
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Biological features . . .
• Life cycle passes through Egg larva  nymph adult stages,
• Deposit eggs in a large batch (# 23,000/female), then female dies,
• Larva search's for a host, climbs, attaches & feeds for 3-7 days,
• The engorged larva drops off & eventually molts to a nymph,
• Nymph searches for a new host and at engorgement drops off;
and then molts to an adult stage,
Ticks . . .

6. Medical & veterinary significance
Direct effects of tick feeding:
• External parasites of humans & almost all other animals,
• Painful bite, general malaise, headaches, etc.
• Allergic nature of materials in saliva & cement,
• Ticks secrete powerful toxins that cause tick paralysis to hosts,
• Tick paralysis ascends from limbs to upper body parts,
 May lead to death from respiratory failure,
• Removing the tick results in a dramatic resolution of paralysis,
Arachnida . . .
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Ticks . . .

7. 1. Forest encephalitis (viral disease),
2. Xinjiang hemorrhagic fever (spirochaetal disease)
3. Lyme disease (spirochaetal disease)
4. Tick-borne relapsing fever(spirochaetal disease)
5. Q-fever (rickettsial disease)
6. North Asia tick-borne typhus (rickettsia disease)
7. Other bacterial diseases (plague, tularemia, etc.)
Arachnida . . .
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Medical & veterinary significance
Ticks as vectors of disease
The indirect impairment:

8. Arachnida . . .
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• Are 2nd only to mosquitoes in the no of diseases vectored,
• Disease transmission by transstadial & transovarial,
• All active instars are vectors of disease,
• Using d/t hosts in d/t instars increasing vectorial capability,
• Great longevity of ticks makes them good reservoir hosts,
• Intracellular digestion easies pathogen entry to the tissue,
Ticks as vectors . . .

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• Human babesiosis & theileriosis are a tick born diseases,
• Human infections are mostly by B. microti & B. bovis,
• Babesia Species invade RBCs causing human babesiosis,
• Theileria species invade T- cells & B- cells causing theileriosis,
 Theileriosis is a disease that displays malaria like symptoms
but without periodicity,
Ticks as vectors of intra-erythrocytic protozoa parasites
Arachnida . . .

10. Arachnida . . .
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• Tick-associated pathogens in Rickettsia group,
e.g., Ehrlichia
• The two main types of human ehrlichiosis:-
I. Human Monocytic Ehrlichiosis (HME),
 has a particular affinity to lymphocytes,
monocytes and macrophages,
II. Human Granulocytic Anaplasmosis (HGA),
 favors neutrophils, basophils & eosinophils,
Ticks as a vector of intracellular bacteria

11. Arachnida . . .
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• The spirochaete genus Borelia, e.g., B. burgdorferi,
 Lyme boreliosis is the most commonly reported,
• Causes human muscle pain or aching,
 Erythema migrans is a rash that appears in the early
stages of Lyme disease,
 Lyme arthritis as oligo-articular relapsing arthritis,
primarily affecting large joints,
 Transmitted through the bites of hard ticks.
Ticks as a vector of intracellular bacteria . . .

12. Arachnida . . .
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Erythema migrans is a rash that appears in the early stages of Lyme disease

13. Arachnida . . .
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Erythema migrans is a rash that appears in the early stages of Lyme disease

14. Arachnida . . .
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Arboviruses
The list of arboviral disease vectored by ticks:
• The Russian spring-summer encephalitis,
• Louping ill and Kyasanur forest disease,
• Crimean Congo hemorrhagic fever,
• Colorado tick fever produce a generalized
systemic infection,
Ticks as a vector of viruses. . .

15. Arachnida . . .
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16. Arachnida . . .
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Ticks have 3 d/t life cycles according to the no of hosts involved

17. Arachnida . . .
 Mites comprise a large group of small to tiny
arthropods,
• less than 1mm long,
 They cause disease themselves & vector disease,
 Important in resurgent & emergent diseases,
(e.g., various rickettsial infections)
 Two body regions an anterior gnathosoma &
posterior idiosoma,
 Idiosoma bears the legs, simple eyes and most
sensory inputs including sight, digestion, excretion
and reproduction,
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Acarina: The Mites

18. Arachnida . . .
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The life cycle of Mites

19. Arachnida . . .
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• Many parasitic mites feed only on body fluids,
• Digestion is external; predigested skin is sucked up,
• The house-dust mite bite off & swallow solid foods,
 Its fecal pellet is a primary source of allergens,
• Mite eggs may be laid singly on or off the host,
Mites . . .

20. Arachnida . . .
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• Human itch mites and scaly leg mites of birds lay their
eggs in the burrow created by the females in the skin.
• Mites have the following developmental stages:
 egg, pre-larvae, larva, protonymph, deutonymph, tritonyph & adult.
• Migration from host to host occurs as mated adult females or
as wandering adult males move,
Mites . . .

21. Arachnida . . .
• Two species of mites infect humans:
1. Demodex folliculorium, the hair follicle mite,
2. D. brevis, the subaceous gland mite,
• Mites are parasites that feed on human epithelial cells
and subaceous gland cells,
 leading to swelling and keratinization of skin,
• Mite infection is common on cheeks, eyelashes and
foreheads of men,
 Cases of scaly skin, granuloma of the eyelid,
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Mites and human disease

22. Arachnida . . .
• Live in our homes & feed on cast skin scales, hair, etc…
• More than 20 species of mites inhabit house dust,
• Affect 50-100 million people worldwide,
• Are the most important source of allergens in house dust,
 Severe allergies,
 Fever-like symptoms,
 Skin inflammation,
 Asthma,
• Mite feces are dry capsules with allergenic enzymes,
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House-Dust mites

23. Arachnida . . .
Scabies mite (Sarcoptes scabie)
The human itch mite & scabies:
 Clinical scabies is characterized
by lesions with burrowing adult
female,
 Scabies mite is the cause of
scabies and is distributed
worldwide.
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24. Arachnida . . .
• Clinical scabies is characterized by lesions with burrowing adult female
Sarcoptes scabiei, which is commonly called egg laying machines.
• Ovigerous females secrete lytic enzymes and dig their way into the skin,
• Transmission occurs when mated mites move from person to person,
• Most infestations are associated with the wrinkled areas of forearms,
hands, wrists & elbows or any susceptible areas that hands may touch.
• Secondary infections are common, and scabies-initiated streptococcal
infections in children may be associated chronic renal disease later in life.
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The human itch mite and scabies:

25. THANKS
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