Ticks and mites

Ticka and Mites for undergraduates

1. Ticks and Mites ( Acarines )

2. Chiggers Harvest mites Kedany Scrub mite

3. The vector mites belong to the order Acarina and family Trombiculidae which comprises many hundreds of species of world wide distribution They are found in great abundance in areas with hot, humid climate, thick vegetation and presence of small vertebrates like rodents. The foothills in subtropical and temperate regions offer them ideal conditions. Exercise Mites are more prevalent in regions with perennial weather True False

4. Exercise Which of the following is also called as “Chigger” Tromboculid Mites Sarcoptes Scabies Anopheles Aedes Aegypti Tromboculid Mites

5. Morphology Adult is about 3-4mm in size Densely covered with hair and has a figure of eight Mouth parts consist of a pair of chelicerae and a pair of palps . Adult resembles the nymph except that it is larger and more densely covered with hairs. Larva is pale yellow to orange-red in colour with… Circular body bearing Three pairs of legs and Branched hairs on the body and on the legs.

6. Exercise Which is the parasitic stage in mites Egg Larva Nymph Adult All of the above Larva

7. Life Cycle Takes 6 to 12 weeks for its development from egg to adult The stages in the life history of a mite are egg, larva, nymph and adult. The eggs laid singly on the surface of the soil. Larva leaves the egg-shell and becomes very active…. …moving quickly, it seeks a suitable host such as rat, mouse etc. Larva feeds on the lymph and the tissue fluid but not on blood of the host. Larvae feed for 2 to 3 days and then drop off to the ground concealing themselves in loose soil, and here they develop into nymphs and finally into adults. Only the larval stages are parasitic; the nymphs and adults are never parasitic and feed on small insects in the soil or their eggs

8. Exercise The orange red colour of the tromboculid larva mite is due to ingested blood. True False False

9. Bionomics Distributed in areas ideal for their survival called as “Mite Islands”. Mite Islands are patches of ground characterized by Thick vegetation cover, mainly the scrub jungles or other tall grasses offering protection from direct sunrays and desiccation Nearly 100% relative humidity at ground level Ideal ambient temperature of 27± 5°C. Shelters animals like rats, mice etc. are also the reservoirs of rickettsiae for which the trombiculid mites are vectors. Mites are most active during the whole rainy season In dry season, the adults migrate deeper into the soil, the egg laying ceases and the mite islands shrink

10. Exercise Which of the following transmits scrub typhus Mites Tick Flea louse Mites

11. Diseases caused by mites Disease Vector Causal organism Reservoir Scrub typhus L. deliense Orientia tsutsugamushi Rodents Rickettsial pox Allodermanyssus sanguineus R akari Rodents Scabies S scabei Man

12. Vector Potential In India, Leptotrombidium deliense is the vector of Orientia tsutsugamushi causing Scrub typhus Rickettsiae taken up by larvae while feeding on rodents are carried through its nymph, adult stages and then its eggs (trans- stadial transmission). The larvae hatching out of these infected eggs are capable of transmitting the rickettsiae to the next host. The infection is thus trans- ovarially transmitted for some generations and hence the mite also acts as a reservoir of infection. Larvae feed only once during their life time causing transmission of infection occuring in second or subsequent generations. Larva comeing in contact with a human being feeds on lymph; rickettsiae contained in the mouth parts are injected into the lymph of the human being thereby causing scrub typhus.

13. Itch Mite ( Sarcoptes Scabiei ) Found all over the world. Infestation is more common when living is congested. All stages (egg, larva, nymph and adult) are completed in the skin, the development from egg to the adult occurring in about two weeks. The female makes zig-zag burrows and lays eggs deep in the horny layers of the skin. Eggs develop into three legged larvae, which enter hair follicles and grow into nymphs and adult. The adult is 0.4 mm in length and oval in shape with flat ventral and convex dorsal surface. The spines and bristles on its body given it the appearance of a hedgehog .

14. Continue…. The male dies after mating, leaving behind the fertilized female to cause the disease. Interdigital webs, wrists, elbows, feet, penis, scrotum, buttocks and armpits. Face, palms and soles are always free in adults but may be involved in children: Predilection After a month or 2, erythematous patches are seen around the burrows which develop into papules and vesicles. Itching is intense at night, which leads to scratching and secondary infection. Personal contact of prolonged nature, such as sharing the same bed, is needed for infection. Transmission through bedlinen is not likely as mites prefer the warm body. Off the host, the parasite dies within two days.

15. Prevention and Control Direct contact with the infested person, or indirect through undergarments, should be avoided. Proper personal hygiene should be observed including bath with soap and water The infested persons and contacts should be treated thoroughly with 3 to 5% percent sulfur ointment or 20 to 25 percent benzyl benzo ate emulsion. The old clothes should be sterilised by boiling. Second application may be necessary. Tetmosol 5 to 10%in soap is a good prophylactic; apply three times a day. 0.5 to 1 percent BHC or Gamma HCH ( lindane ) in coconut oil applied on the affected parrts 2-3 times at interval of 2-3days.

16. Morphology Distinguished from other acarines by their relatively large size and absence of prominent hairs on the body. Oval in shape and of varying colours and dorsoventrally compressed. Females are larger and are capable of great distention. Both sexes and all other stages thrive on blood alone They are free living on the ground in between various moults during development. Two families, Family Ixodidae which is the HARD TICK and Family Argasidae which is the SOFT TICK . The hard tick is more a jungle tick while the soft tick is a domestic or household tick like a bedbug.

17. Exercise Which is the parasitic stage in Ticks Larva Nymph Adult All of the above All of the above

18. Hard Ticks Dorsum of the adult male is covered by a dark shield, called scutum . This may be ornate with grey or white ‘patterns’. In females and immature males, it covers only the anterior part ‘ Capitulum ’ is the false head, actually formed by the mouthparts anteriorly Soft Ticks Oval with leathery cuticle and devoid of scutum . Mouth parts are placed ventrally and hence not visible from above

19. Exercise False about ticks Cant stand starvation Has a very short life span and always found on host Scutum is present in the entire back of male and in a proportion in females Readily comes out in night for feeding Cant stand starvation

20. Life Cycle Passes through stages egg, larva, nymph and adult taking 6 weeks to 2 years Fertilized female (Fed) drops off to the ground and lays eggs in cracks and crevices. Hard ticks deposit all their eggs in a single act of oviposition after which they die. Eggs take a few weeks to several months to hatch. Larvae are six legged and do not feed for about a week after emergence does QUESTING after this period Nymphs emerge after 1 st moulding with 4 th pair of legs and does Questing, feeds and again drop off. They again moults to adulthood and become sexually mature being parasitic and exhibiting questing Copulation takes place after the last moult and the male dies after fertilizing the female.

21. Exercise Which of these regarding ticks is not true Females are larger than males Both sexes thrive on blood alone They are free living on the ground in between various moults All are true All are true

22. Bionomics Hard ticks are open jungle dwellers and thrive on animal hosts Do not attach themselves to human beings voluntarily but accidentally. Soft tickson although preferentially parasitic on animals and birds attack man voluntarily. Found in human dwellings and cattle sheds and attack man and animals during their sleep. They however, live away from their hosts, in cracks and crevices and only emerge at night to feed on the host . Ticks can survive starvation for a long time

23. Hard and Soft ticks Attributes Hard Tick Soft Tick Life Cycle O->L->N->A O->L->N1->N2->N3->…A Habitat Free range species ; attacks host in the day Burrow inhabiting species ; basically a nocturnal feeder Nymph 1 instar Several (5-7) instars Adult Feeding 1 blood meal Intermittent feeders (5-12 or more) Hosts 1-3 hosts More than 10 hosts Egg laying Tjhousands in a single batch Less than thousand in several batches Life span 2 months – 3 years Long duration ( as long as 16 years)

24. Diseases caused by Ticks Disease Vector Causal organism Reservoir Kyasanur Forest Disease (KFD) Hard ticks species Arbovirus group B Monkeys/Birds Tick typhus Hard ticks species R conorii Dogs Tularaemia Hard ticks species P tularensis Rabbits/ Rodents/cattle Relapsing fever Soft Tick B duttoni Rats

25. Exercise All of the diseases are caused by ticks except Relapsing fever Tularemia Epidemic typhus Tick typhus Epidemic typhus

26. Vector Potential Diseases in man by transmitting the viruses, rickettsiae , spirochaetes and bacilli of infectious diseases and through toxin present in their saliva. Factors which account for high vector potential are that All the stages are haematophagous and are Persistent blood suckers While feeding they attach firmly and cannot be easily removed. They are resistant to varying environmental conditions and relatively protected from natural enemies. Trans- stadial and transovarian transmission of infection helps in maintaining infection for several years. Power to regenerate lost parts such as amputated legs and also the ability to repair mutilated mouth parts, which conserves them for long.

27. Control of Ticks and Mites Area Treatment : “ Malathion 50% EC” (as 5% solution) / “ Cyfluthrin EC” should be sprayed On Vegetation Spraying Malathion , Fenthion , Propoxur and Permethrin are suitable Domestic Animals : Wash or spray containing 2% Malathion , 1% Propoxur , Deltamethrin (0.025%) Personal protection using Dibutyl-phthlate (DBP), Diethyl phenyl acetamide (DEPA) and Diethyltoluamide (DEET). Wearing body covering clothing Walking while on grass Use of Insecticide treated mosquito net Removal of shrubs, trees, or tall grass can be useful in recreational areas. Insecticidal Control Habitat Management Personal Protection Anti-Rodent Measures