7.
TICKS
1) Introduction: Ticks belong to the order Acarina of the phylum Arthropod. They
are blood-sucking ecto-parasites on vertebrate mammals (Human, dog, cattle,
etc). They are oval in shape and not distinctly separated into head, thorax and
abdomen. They have four pairs of legs, and no antennae. Male are generally
smaller than female.
Ticks are of two types: Hard tick (Ixodidae), Soft tick (Argasidae).
2) Comparison of hard and soft tick:
Characteristic Hard Tick Soft Tick
1) Scutum (chitinous Covers the entire back in Absent.
shield) male; a small portion in
front in female
2) Head Situated at the anterior Lies ventrally; cannot be
end. seen from above
3) Feeding habits Cannot stand starvation; Can stand starvation for a
feed night and day. year or more.
4) Location Always found on their Hides in cracks and
hosts. crevices in day time and
emerge at night to feed on
the host.
5) Important species Dermacentor andersoni, Ornithodorus moubata
Haemophysalis spinigera
6) Diseases - Kyasanur Forest Disease - Kyasanur Forest Disease
transmitted - Tick typhus - Q fever
- Viral encephalitis - Relapsing fever
- Viral fevers
- Tularemia
- Tick paralysis
- Human babesiosis.
3) Life cycle: There are four stages; Egg, Larva, Nymph & Adult.
a) Egg
- Hard ticks lay several hundred to thousand eggs at one sitting, after which the
female is exhausted and dies.
- Soft ticks lay in batches of 20 – 100 over a long period.
- Eggs are deposited on the ground; hatches in 1 – 3 weeks.
b) Larva
- Possesses 3 pairs of legs.
- Lies in wait among grass and herbiage till a suitable host appears to which it
attaches itself and has the blood meal.
- It then drops off the host, moults to become nymph.
- the duration of larval stage is 3 to 13 days
c) Nymph
- Resembles the adult in having 4 pairs of legs, but has no genital pore.
- all are blood suckers; attach to suitable hosts for a blood meal.
- Hard ticks: 1 nymphal stage; Soft ticks: 5 nymphal stages in life history
d) Adult:
- Hard tick: Duration of lifecycle from egg to adult – 2 months; soft tick – 9 to 10
months.
- adult ticks may live for a year or more. Soft ticks live longer than hard ticks.
4) Control of ticks
a) Insecticidal control: 5% DDT, 2.5% Chlordane, Dieldrin, Lindane, Malathion,
Toxaphane at rates of 1 to 2 lbs. per acre. Either dusting or spray formulations can
be employed. Animals may be freed of ticks by treating them with insecticidal
sprays or dusts.
b) Environmental control: Cracks and crevices in grounds to be sealed; particularly
near buildings and paths.
c) Personal protection measures of workers: Protective clothing impregnated with
insect repellents (indolane, diethyltoluamide and 25% benzyl benzoate) to be
used by workers. Persons working in tick infested areas should be trained to
examine themselves for ticks and to remove promptly any ticks found on their
person.
