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ecology is relatively high rainfall. Within their areas of distribution, these ticks vary in relative prevalence and density, due in part to approaching thresholds or extremes within the range of tolerance. A very definite line of demarcation, uneffected by the movement of cattle along trade routes, exists between these two zones.
Huts of pastoral peoples in which cattle and other domestic animals frequently rest harbor the tropical bont tick. Smith (1955) noted its presence in human habitations and a similar situation may have accounted for Robinson's (1912) remarks concerning parasitism on children by the so called variety nocens.
The red-billed oxpecker or tickbird, Euphagus e. erythrorhynchus (Stanley), which attends all the larger herbivores except the elephant and the hippopotamus, has been shown by Moreau (1933) to be a predator of some importance on A. variegatum and other economically important ticks. Of the 58 tickbirds examined in Tanganyika, 186 specimens of A. variegatum were found in the stomach contents of sixteen; the number of ticks per stomach ranged from one to 109.
In Kenya, van Someren (1951) took specimens of the tropical bont tick from stomachs of a few of the same birds that he examined. He also found unidentified ticks in Tanganyika birds, B. a. africanus. van Someren's interesting biological study of the red-billed oxpecker includes observations on the birds' habit of irritating Sores on domestic animals.
Buphagus erythrorhynchus and B. africanus subspp. range through African savannahs and frequently are seen clinging to the flanks or legs of domestic and wild animals. Lang # noted the tickbird acting as a sentinel for elands. Loveridge (1928) reported specifically unidentified ticks in stomachs of Tanganyika tickbirds and Dr. J. P. Chapin found ticks in their stomachs in the Congo and in Kenya (Bequaert 1930B). I am told that the best account of tick-eating habits of these birds is quoted in Bannerman's Birds of Tropical West Africa (Volume 6, page 105).
Assertions that the white heron, or cattle egret, Bubulcus spp., is a tickivore are not supported by evidence. Dr. Chapin
found no ticks in cattle egret stomachs and their actions do not indicate that they commonly feed on these parasites (Bequaert 1930B, Plowes 1950). In Southern Rhodesia, "Egret" (1938) reported, these birds may pick grasshoppers off grazing cattle but do not search for ticks on them. Colleagues and I have found no ticks in stomachs of many cattle egrets examined in Africa and elsewhere and Kirkpatrick (1925) found none in stomachs of many Egyptian birds of this type.
Special attention is called to the taxonomic and biological status of heavily punctate specimens of A. variegatum, discussed under A. pomposum (page 245).
Remarks by Theiler (1951 correspondence) are of value in understanding distributional factors of this species and in illustrating the care that must be taken in evaluating older literature. She writes: "..... statements made (Theiler 1943B), to the effect that this species is found in the Union of South Africa, were based on records in the literature, i.e. before we had studied the South African tick survey material . . . . . Our abundant material did not produce one specimen from anywhere in the Union or in South-West Africa. Bedford's statements are based on incorrectly identified nymphal material. Robinson's record in the Monograph, I take to be a record of an introduction into the country, which certainly has not been able to maintain itself. Nor does A. variegatum seem to be as widely spread in Southern Rhodesia as one gathered from some of the earlier workers. On the contrary, A. hebraeum seems to be more prevalent than was first thought. When reading reports of earlier workers (1896-1906), one must bear in mind that they are still reporting on a period during which cattle had been, or were being, introduced from East Africa and from Madagascar, bringing A. variegatum and Boophilus fallax with them. Possibly some of EHESE EIGRs come into areas in which they could maintain themselves for a year or two, or possibly even longer."
Brumpt (1922, 1934) reported on gynandromorphic specimens of
A. variegatum. Malformed specimens have been noted by Santos Dias ######. and Tendeiro (1951F). Certain aspects of the chitinization of the exoskeleton and gut and of the musculature of this species have been discussed by Ruser (1933). A. variegatum has been used to illustrate the double oblique-striation # tick musculature by Kruger (1935). Variations in scutal ornamentation among specimens from a restricted area were illustrated by Tendeiro (1949B, 1951F). The eye structure and related sense organs were described and illustrated by Gossel (1935).
MAN and ANIMALS: Q fever (Coxiella burnetii). Larvae and nymphs commonly attack man under local conditions and may cause severe irritation.
CATTLE: Heartwater (Rickettsia ruminantium). Bovine lymphangitis, large septic sores, and severe inflammation of mammae. Possibly transmits a fungus, Cryptococcus (= Actynomyces) farciminosus.
A. variegatum has been mentioned in connection with bovine rickettsiosis (Rickettsia bovis), but the tick's role does not appear to have been defined. This tick does not transmit East Coast fever (Theileria parva).
SHEEP: Nairobi sheep disease (virus). Heartwater (R. ... -- ruminantium).
GOATS: Heartwater (R. ruminantium). Severe secondary infection and lameness.
PIGS: Possibly a vector of porcine piroplasmosis (Babesia trautmanni).
WILD ANIMAL INJURY: In the Sudan I removed a live nymph from a thigh abscess that was almost completely overgrown by the skin of the jackal host.
Males: There is no question of identity of this important
species in the Sudan tick fauna or throughout most of its range. The combination of characters including hemispherical, orbited eyes, long lateral grooves, entirely black festoons, and paucity of large scutal punctations easily distinguishes A. variegatum. The scutal ornamentation is as illustrated (Figure 92) except that in about five percent of specimens an additional coppery spot may be found just inside (not outside) of the lateral grooves at the level of the scutal midlength. Specimens with these spots are readily distinguished from A. lepidum and A.
mposum by their dark festoons and lack of large scutal puncta#
Note: According to Jack (1942) males from eastern parts of Southern Rhodesia approach A. pomposum in that they have coarse scutal punctation. No females were available for comparison. A few confusing specimens such as these from the Sudan, East Africa, and Yemen (Arabia) have been observed (See IDENTIFICATION of
A. pomposum, page 245).
Females: This sex is sometimes more difficult to identify with certainty than the male. Hemispherical, orbited eyes are also found in A. lepidum and A. sum. In the latter, the very rugose, broad, short scutum easily separates it. The posterior margin of A. variegatum is comparatively more broadly rounded than that of A. lepidum. One may have considerable difficulty in deciding whether a female scutum is widely or narrowly pointed posteriorly. There appears to be some variation in this character, but a thorough study has been impossible because, in all available collections, no more than eighty female specimens of A. lepidum have been seen. No large series from any single area has been represented and until such time as more material comes to hand it is preferable to hold the study of this feature in abeyance.
African Aponomma ticks, small, eyeless parasites of large snakes and of monitor lizards (Varanus spp.), are seldom represented in collections. They are markedly host-specific and rarely feed on animals other than their normal hosts.
Originally considered as Amblyomma, species of the genus Aponomma are now treated as a separate generic offshoot from # omma. In this genus the eyeless condition is considered by some to have resulted from disuse since certain members feed under the host's scales. Parallel instances also occur among those Amblyomma ticks that have indistinct or vestigial eyes and that parasitize scaly hosts. This interpretation might hold for those Aponoma species that attach below snakes' scales but may hardly account for the eyeless condition of others attacking only scaleless lizards. Possibly Aponomma ticks became adapted to lizards as a concomitant to the # of vision.
The biology of aponommas is poorly known. Adults and nymphs are frequently found on the same host.
The nomenclature of the few African species has been confused until the recent works of Theiler (1945A,B). Most African specimens are now easily identified to species. More recently, Santos Dias (1955C) has redescribed the type material of A. ochraceum Neumann, 1901, from Tanganyika and Zanzibar, and of A. fraudigerum Schulze, 1935, from a host, Varanus griseus, presumed to have come from North Africa. *
*W. iseus ranges over the entire northern Sahara region, reaching the Mediterranean only in southern Tunisia, Libya, and Egypt, and extends to the Central Provinces of India (Loveridge, correspondenge). The source of the type material of A. fraudigerum, Fuhlsbuttelterrarium, probably refers to the grounds of an animal dealer at Fuhlsbüttel, a suburb of Hamburg, and the collector, Karl Peter, is probably not the famous African explorer but rather the animal dealer (Theiler, correspondence).