Brown ticks: Genus Rhipicephalus

Genus Rhipicephalus

Unfed Rhipicephalus are medium-sized ticks (3 to 5 mm including mouthparts). Their integument (cuticle / outer covering) texture has striations. Rhipicephalus mouthparts are anterior, the palpi are wider than long and the palp article are all small. The basis capituli (basal part of the mouthparts, the 'gnathastome') has a hexagonal shape. Rhipicephalus legs are slender with pulvilli and usually do not have pale rings. A scutum ('dorsal shield') is present in the female with a conscutum in the male. Rhipicephalus are usually not ornate although four species have enamel. Eyes are present and rather flat (except in Rhipicephalus evertsi where they are bulging). Festoons are present in both sexes, but unclear in fed females. Spiracular plates are large and posterior to legs. Ventral plates are present only in males, usually as two pairs. The anal groove is posterior to the anus. The fourth pair of Coxae 4 are of normal size, whilst the first pair 1 have large and equal paired spurs.

There are about 74 known species in the genus Rhipicephalus. The dog tick (Rhipicephalus sanguineus) has a worldwide distribution, but otherwise species of the genus are restricted to the Old World especially Africa. They mainly occupy savanna and open woodland habitats and only feed on mammals. Most species are three host ticks. The genus Rhipicephalus includes important disease vectors. Disease organisms transmitted to domestic animals include Theileria parva, the causative agent of East Coast fever (ECF) in cattle, and Anaplasma spp. which cause bovine anaplasmosis.

Dorsal view of male and female Rhipicephalus evertsi. Photo: Courtesy of Armed Forces Pest Management Board under a Creative Commons Attribution License

Rhipicephalus appendiculatus (Brown Ear Tick)

Both sexes have sparse interstitial punctuation and the punctation size is small to medium. In the male the anterior spurs on the first pair of coxae are prominent and visible dorsally. The cervical fields depression is apparent and wrinkled. The conscutum colour is dark. Posterior grooves are distinct but shallow with wrinkled texture. On the ventral surface the adanal plates are narrow and trapezoid and the accessory adanal plates are very small. In the female Rhipicephalus appendiculatus, the lateral angles of the basis capituli are blunt. The separation of the porose areas is broad and the palp pedicels are short. The cervical fields have wrinkled areas and are large and curved. The scutum is dark with the posterior margin distinctly sinuous. The eyes are slightly convex and the genital aperture has posterior lips forming a broad V shape.

Rhipicephalus appendiculatus is found from southern Sudan, through to the south eastern coast of South Africa. It is not clear how far west it extends, but it has definitely been recorded from Zambia and the Democratic Republic of Congo. It is characteristic of savanna and temperate climatic regions, ranging from hot coastal areas to cool highland plateau as long as the climate is humid.

Male and female Rhipicephalus appendiculatus. Photo: InfluentialPoints (Joel Kanunga)

The picture of the male (above left) shows the lateral groove clearly. The festoons at the posterior edge of the male conscutum and the distinct posterior grooves. The anterior spurs on the first pair of coxae are just are also visible. The pictures of the female (above right and below) show the dark scutum with its posterior margin distinctly sinuous.

Brown ear ticks feed on cattle, goats, and a variety of larger antelopes as well as dogs and sheep. All stages may feed on cattle although immature ticks can feed on smaller antelopes and scrub hares. The immature stages attach mainly on the neck and dewlap, the cheeks, eyelids, muzzle and ears. The preferred feeding site of the adults is the pinna of the ear, with very few in the ear canal, but in heavy infestations adults are also found around the eyelids and horns, on the upper neck, in the tail-brush and around the anus. Heavy infestations on the ears of a cow in Kenya are shown below.

Rhipicephalus appendiculatus on ears of cow in Kenya. Photo: InfluentialPoints (Joel Kanunga)

Rhipicephalus appendiculatus is a three-host tick which has been extensively studied (Perry et al., 1991; Randolph et al., 1994). Under the most favourable conditions the whole life cycle can be completed in three months, but occurrence becomes seasonal where there is a pronounced dry season. The pattern of seasonal occurrence is regulated by the unfed adults, which enter diapause and do not engage in host-seeking until the rains start. Where rainfall is more evenly spread through the year, several overlapping generations are completed annually, and no clear pattern of seasonal abundance is evident.

The brown ear tick transmits Theileria parva that causes East Coast fever in cattle, and also the different strains of Theileria parva that cause Corridor disease. It also transmits Anaplasma bovis causing bovine ehrlichiosis, Rickettsia conorii causing tick typhus in humans, and Nairobi sheep disease virus (in the family Bunyaviridae). There is also evidence of a loss of potential growth of cattle even without any disease transmission. As a result, efforts are usually made to control tick populations. The simplest (albeit most time consuming) method is to simply pick the ticks off, as shown below for a goat kid.

Maasai lady removing Rhipicepalus appendiculatus (brown ear tick) from goat kid in Kenya. Photo: InfluentialPoints (Joel Kanunga)

Whilst hand-picking is commonly done for very young animals, acaricides are widely used for older animals. Traditionally they have been applied using dips for large numbers of animals and sprayers for smaller numbers. The first picture below shows acaricide being applied using a backpack sprayer to goats in Maasailand.

Chemical control of Rhipicephalus appendiculatus in Kenya. Photos: InfluentialPoints (Joel Kanunga)

More recently pour-on formulations of synthetic pyrethroids have become popular. The picture above right shows a pour-on acaricide being applied along the midline of the back of a calf.

Whilst frequent and sustained tick control can certainly reduce the incidence of East Coast Fever, it is expensive and does commit livestock keepers to sustained and sometimes increasing levels of insecticide application. Cessation of treatment can lead to high cattle mortality because of the disruption of enzootic stability. The current recommendation is therefore that an integrated approach is adopted with acaricides to reduce tick numbers, treatment of clinical cases and vaccination using the infection-and-treatment method recently registered in several East African countries (Di Giulio, 2009).

Rhipicephalus praetextatus (Cattle Leg Tick)

Both sexes have sparse interstitial punctuations and the punctation size is minute to small. As a result the dark scutum/conscutum has a smooth shiny appearance. The eyes are slightly convex. In the male, coxae 1 anterior spurs are not visible, and the cervical fields depression is not apparent. Posterior grooves are absent and lateral grooves are indistinct. The adanal plates are triangular in shape with the posterior side concave in profile. As a result three points are formed, one by the accessory adanal plate and two on the lower side of the adanal plate. This characteristic serves to distinguish the male from other species likely to be found on domestic livestock. In the female the lateral angles of the base of the gnathostoma are blunt, and the palp pedicels are long. The posterior margin of the scutum is distinctly sinuous. The cervical fields are large and curved. The posterior lips of the female genital pore have an exceptionally broad U shape.

Rhipicephalus praetextatus is an African species which occurs in a wide range of climatic regions from temperate highland areas through to savanna and steppe to desert climates. It is widespread in most of the eastern countries from northern Egypt down to southern Tanzania.

Two likely Rhipicephalus praetextatus removed from leg of bull in Kenya. Photo: InfluentialPoints (Joel Kanunga)

The picture above shows what appears to be two Rhipicephalus praetextatus that had been feeding just above the foot of a zebu bull. Note the near circular shape of the scutum with no sharp angles. The feeding position and the visible characters strongly suggest this species, but we cannot be certain.

Rhipicephalus praetextatus is a three-host tick whose preferred domestic hosts are cattle, camels, dogs, large wild carnivores, zebras and warthogs. The immature stages prefer murid rodents (mice). On cattle the adults attach mainly around the feet (as shown in the picture below) and in the tail-brush.

Several likely Rhipicephalus praetextatus feeding on leg of bull in Kenya. Photo: InfluentialPoints (Joel Kanunga)

The feeding of this tick species can cause toxicosis in cattle, resulting in paralysis, but is not known to transmit any cattle diseases. It is a known vector of Nairobi sheep disease in sheep, and may transmit the bacterium Rickettsia conorii to humans causing tick typhus.

Rhipicephalus pulchellus (Zebra Tick)

Several Rhipicephalus pulchellus feeding on cow in Kenya. Photo: InfluentialPoints

Preferred wild hosts of adult Rhipicephalus pulchellus include zebra and eland. Preferred domestic hosts are cattle, as well as camels, sheep and goats. Large numbers may attach on the ears and the underside of the body, including the chest, belly, genital and especially around the anus. The immature stages feed on these animals as well as on hares, and will readily attach to humans.

Rhipicephalus pulchellus has a three-host life cycle with adults most active during the rainy season. It can occur in such large numbers that it may affect cattle production through blood loss. Like Rhipicephalus appendiculatus it transmits Nairobi sheep disease virus and tick typhus, but it does not transmit East Coast Fever. Instead Rhipicephalus pulchellus transmits Theileria taurotragi which is pathogenic in eland, but benign in cattle and also Babesia equi to zebra.

Rhipicephalus pulchellus (zebra ticks) around vagina of cow. Photo: InfluentialPoints

Given the absence of disease transmission, it is not usually considered worthwhile to control this species of tick (but see Regassa (2001).) Indeed, one might expect to get a degree of biological control of Rhipicephalus pulchellus by oxpeckers, one of which can be seen below feeding around the anus of a cow. This is the rarer of the two types, the yellow-billed oxpecker.

Yellow-billed Oxpecker feeding on ticks (and blood?) around anus of cow. Photo: InfluentialPoints (Joel Kanunga)

However, oxpeckers may not be as 'helpful' to tick-afflicted mammals as previously thought. Weeks (2000) has shown experimentally that adult tick loads on cattle were unaffected by the presence of red-billed oxpeckers. Direct observation suggested that most of the oxpecker's time was spent feeding on blood at wounds and on ear wax, rather than on ticks. It has been suggested that this is less true for yellow-billed oxpeckers (Naish, 2007), but local Maasai herders where these pictures were taken also regarded the yellow-billed oxpeckers as harmful pests frequently opening wounds on cattle to feed on the blood!

Yellow-billed oxpeckers on Acacia bush after disturbance by Lanner falcon. Photo: InfluentialPoints (Joel Kanunga)

Whatever oxpeckers are eating, one thing they are understandably concerned about is getting eaten themselves. The raptor circling overhead in this image, most likely a Lanner Falcon (Falco biarmicus), caused these oxpeckers to forsake their cattle host in favour of a suitably thorny Acacia bush.

Rhipicephalus sanguineus (Brown Dog Tick)

Photo: Courtesy of Wikipedia/US Federal Government (public domain)

The picture above is a dorsal view of male Rhipicephalus sanguineus. Note especially the reddish-brown colour of the conscutum and the deep posterior grooves enclosing a wrinkled texture.

Because of its veterinary and public health relevance, Rhipicephalus sanguineus is one of the most studied ticks - a good review of this work is given by Dantas-Torres (2010). The main host for all stages of the brown dog tick is the domestic dog. In urban situations everywhere, dogs are virtually the only hosts of immatures and adults. In rural situations in warmer climates, adults can also parasitize any wild or domestic carnivore, most livestock species and various other wild mammals, especially hares and hedgehogs. Immature stages of this tick may also attach to humans.

On dogs adults attach on the ears, neck and shoulders, nymphs are also found on the ears and shoulders, and larvae attach particularly to the belly and flanks. The picture below shows a dense infestation in the ear of a dog which lived with its owner in a Maasai homestead.

Rhipicephalus sanguineus (brown dog ticks) in ear of dog in Kenya. Photo: InfluentialPoints (Joel Kanunga)

The brown dog tick is a three host tick. The engorged female detaches and lays its eggs in cracks and crevices of buildings or under the dog's bedding. The eggs hatch in a few weeks, the resulting larvae attach to their host and engorge over a week. These larvae then detach and moult to nymphs within a few weeks. The nymphs find another host, engorge, detach and moult to adults usually within a few weeks. The adults then engorge and the cycle continues.

All these stages take place around where the dog lives and in temperate climates may be indoors or in a kennel. Under ideal conditions the life cycle can be completed in only 10 weeks. Rhipicephalus sanguineus is active throughout the year in the tropics and subtropics. In temperate zones ticks are only active from spring to autumn, over-wintering as the pre-moulted nymphal stage or as engorged females. The peridomestic behaviour of the tick means that dogs regularly sleeping in the same place may become heavily infested, as was the case for the animal below:

Heavy infestation of Rhipicephalus sanguineus (brown dog tick) on dog in Kenya. Photo: InfluentialPoints (Joel Kanunga)

Rhipicephalus sanguineus is a potent disease vector for dogs and can transmit Ehrlichia canis, the causative agent of canine ehrlichiosis, and Babesia canis, the causative agent of canine babesia. It also transmits Rickettsia conorii, which causes Mediterranean spotted fever (= Boutonneuse fever) in humans and may be a carrier of Coxiella burnetii causing Q-fever and of Crimean-Congo hemorrhagic fever.

Prevention is the best form of management, especially prevention of any tick engorgement. Treatments with fipronil (in sprays and spot-ons), amitraz (often in flea and tick collars), permethrin (sprays and shampoos) and deltamethrin (shampoos) have been reported as effective. Regular treatment will minimize the chances of a dog picking up a tick and the tick successfully feeding. Once an infestation has started, thorough treatment of the dogs is important and may need to be repeated several times. Dogs should be examined regularly and attached ticks removed and disposed of.

Other mammals should be monitored and treated if necessary, but be careful about treatments used on cats. Some tick and flea treatments for dogs are poisonous in cats. The earlier the infestation is discovered and addressed, the easier it will be to control. Monitoring and grooming dogs, particularly upon return from kennels or locations where other dogs are present, is the best way to detect infestations early.

Acknowledgements Whilst we try to ensure that identifications are correct, we do not warranty their accuracy. We have mostly made identifications using Walker (2001). Further information was obtained from Kolonin (2009), Natural History Museum and Lord (2001-2011). We fully acknowledge these authors as the source for the (summarized) taxonomic information we have presented. Any errors in identification or information are ours alone, and we would be very grateful for any corrections.

References  Dantas-Torres, F. (2010). Biology and ecology of the brown dog tick, Rhipicephalus sanguineus. Parasites & Vectors 3:26. Full text  Di Giulio, G. et al. (2009). Live immunization against East Coast fever - current status. Trends in Parasitology 25 (2), 85-92. Abstract  Perry, B.D. et al. (1991). Estimating the distribution and abundance of Rhipicephalus appendiculatus in Africa. Preventive Veterinary Medicine 11 (3-4), 261-268. Abstract  Randolph, S.E. et al. (1994). Population dynamics and density-dependent seasonal mortality indices of the tick Rhipicephalus appendiculatus in eastern and southern Africa. Medical and Veterinary Entomology 8 (4), 351-368.Abstract  Regassa A. (2001). Tick infestation of Borana cattle in the Borana Province of Ethiopia. Onderstepoort Journal of Veterinary Research 68, (1), 41-5. Full text  Walker, A.R. (2001). Ticks of domestic animals in Africa: a guide to identification of species. Bioscience Reports. Full text  Weeks, P. (2000). Red-billed oxpeckers: vampires or tickbirds? Behavioural Ecology 11 (2), 154-160. Abstract  Full text

Last updated 3 January 2013