Atlas of livestock parasites
digitized collection of microscopical preparations

Atlas of Parasites Contents Information sources Glossary Administration

Trombicula spp.



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Trombicula spp.
Larvae are "harvest mites" or "chigger mites"

General Description:
Larvae before engorgement are very small, 200 microns in length, reddish in colour. Adults are orange mites, about 1 mm long; bodies are densely covered with hair.

Life Cycle:
Free-living adults deposit eggs on soil. In about 10 days larvae hatch and climb onto animals where they attach and feed for approximately 3 days, causing much inflammation. Larvae drop off and eventually molt to the nymph stage. Adults arise from these, some 50 to 55 days after eggs hatch.

Skin, especially head and neck, is diseased by larvae. Adults and nymphs do not live on host.

Geographical Distribution:
Trombicula spp: Worldwide. Trombicula sarcina - Australia (Queensland, where "black soil" exists).

Trombicula, "chigger mites," are not a major problem in sheep.

Effect on Host:
Lesions are small (about 1 cm. in diameter), raised areas containing pus. Extremely intense itching causes scratching and skin disruption by the host. Larvae on the skin of host secrete enzymes which dissolve outer layers of skin, causing much inflammation in the localized lesions. The intense itching that results causes sheep to scratch heavily, further damaging their own skin. Severe scratching of in flamed red areas, especially on the head and neck. Infested legs and feet may be noticed when the host stamps its feet.

Diagnostic Information:
Scrapings of papules may reveal reddish larvae microscopically.

Insecticide dips may be effective.


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