Atlas of livestock parasites
digitized collection of microscopical preparations

Atlas of Parasites Contents Information sources Glossary Administration

Amblyomma spp. (sheep, goats)

Category:


Species:
Ectoparasite


Description:
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Amblyomma, Boophilus, Dermacentor, Haemaphysalis, Ixodes, Rhipicephalus
Ticks

General Description:

These six important genera of sheep ticks may be differentiated on the basis of several characteristics. Ambyomma and Dermacentor ticks have ornate (patterned) upper body surfaces, whereas Boophilus, Haemaphysalis, Ixodes, and Rhipicephalus are plain brown in colour. Rectangular divisions on the rear body edge are called festoons and are present only on Ambyomma, Dermacentor, Haemaphysalis, and Rhipicephalus. Ambyomma ticks have long, prominent mouth parts, easily distinguished from the short mouth parts of Dermacentor. Of these ticks, only Haemaphysalis and Ixodes are eyeless.

Life Cycle:
Ambyomma species are three-host ticks. Their life cycle varies in length from 3 months to over 2 years, depending on species, climate, and host availability.
Boophilus a one host-tick genus can complete its life cycle in 1 to 2 months under optimal conditions.
Some species of Dermacentor are one-host ticks, while the rest are three-host species. Depending on species and climate, generation time ranges from 2 months to 3 years.
The life cycle of Haemaphysalis, a three-host tick genus, can be completed in 4 months. Each stage can survive for 8 months or longer before eating a blood meal.
Ixodes is a three-host tick genus with a life cycle that requires about 3 years. Unfed larvae, nymphs, and adult ticks can each survive for 2 years.
Rhipicephalus ticks have two- or three-host life cycles, depending on the tick species. The life cycle takes at least two months.

Location:
Anywhere on the host body.

Geographical Distribution:
Ambyomma parasitizes all domestic livestock species in central and southern Africa, the southern United States, Mexico, and Central and South America to Brazil.
Boophilus occurs on sheep in warm climates throughout the world except the United States, where it has been eradicated.
Species of Dermacentor are found in Asia, Europe, and North and South America, while Ixodes species occur in Europe, North America, and South Africa.
Haemaphysalis species are distributed throughout Europe, Asia, Africa, the Far East, New Zealand, and Australia.
Rhipicephalus species are significant in Africa - South of the equator.

Significance:

Heavy tick infestation can cause great debilitation. Sheep ticks are of major economic importance. Large numbers can cause anemia, but perhaps of even more importance is tick transmission of diseases, including louping ill, rickettsial tick-borne fever, piroplasmosis, Nairobi sheep disease, spirochetosis, heartwater, and Q fever.

Effect on Host:
These parasites cause tick worry, blood loss, and damage at feeding sites and can transmit protozoal diseases. Wounds left from tick bites are susceptible to additional attack by various biting flies and flesh fly larvae. Infested sheep itch, bite, and scratch, causing self-inflicted wool damage and skin trauma which can become infected. Heavy tick burdens may result in anaemia, loss of appetite, and weight loss. Ambyomma, Dermacentor, and Ixodes ticks are associated with tick paralysis, which can be fatal within several days if the parasites are not removed. The paralysis is caused by toxins injected by female ticks while they suck blood.

Diagnosis:

Identification of adult ticks found on host animal.

Control:
Treatment of infested animals and their premises is an integral part of tick control. Chemical agents with residual action are most effective.


Pictures:

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