386
The Ticks of East Africa
Reference has already been made to O. megnini and M. winthemi as
species that have been collected only at Mombasa, so far as is known. These
ticks arrived on stock from South Africa, and the usual veterinary inspection
of imported animals revealed their presence before the animals were permitted
to proceed inland.
It may here be stated that one record of A. hebraeum from the Tana river
area in Kenya has not been confirmed, nor has the species been found in the
Colony within the last 10 years. There is a record of its presence in south
Tanganyika, but this also awaits confirmation.
Whereas it is not possible as yet to define with accuracy the areas and
natural conditions most favourable to the separate species in East Africa, it
has been observed that there are areas and localities where two or three species
predominate over others, which again differ in numerical frequency. These
areas are not always sharply defined, as there are extensions of ticks into
neighbouring zones ; and there is frequent overlapping. A marked change
may take place in the tick-fauna, as illustrated in the case of R. pulchellus in
the Masai Reserve. This species is extremely common in the Ngong district
of the Reserve as far as the Uaso Nyiro river that separates the Ngong from
the Narok district. In the latter no R. pulchellus has been found except on an
occasional animal that has crossed the river. R. appendiculatus also may
cease abruptly. In the West Suk district, this tick is generally abundant on
cattle in the Kapenguria area (5,500 to about 7,500 ft.) but is absent from the
adjoining area of Kacheliba (3,000 to 4,500 ft.) although cattle from both
areas use the common salt-licks in Kacheliba.
Evidence from a few surveys and numerous collections enables most of
the western part of the Colony to be classified according to the groups of domi-
nant species of ticks.
The south-eastern, or Ngong, district of the Masai Reserve is A. variega¬
tum—R. pulchellus country : the Narok district may be termed A. variegatum—
R. neavei country, and the trans-Mara designated as a R. appendiculatus—A.
variegatum area. In the Rift Valley—from Solai through Nakuru to the
Kedong river—the combination is Hyalomma spp. A. variegatum—R. appendi-
culatus, although control measures may have altered the natural abundance.
In Limuru there is the Boophilus—R. capensis predominance ; in Kaimbu and
Fort Hall, R. appendiculatus—A. variegatum. In the Naro-Moru district R.
pulchellus—R. appendiculatus prevails, whereas in the Thompson's Falls area
R. capensis—Boophilus—R. appendiculatus occurs. A. variegatum—R. macula¬
tus—R. simus forms a zone near Malindi on the coast and Hyalomma—A.
gemma—A. variegatum around Marsabit in the Northern Frontier Province.
R. appendiculatus and A. variegatum are the chief ticks in the Kavirondo Re-
serves. Towards, and just within, the north-eastern corner of Uganda, A.
lepidum appears to be the one prevalent tick ; and around Mpwapwa in
Tanganyika is the dominant group of A. variegatum—A. gemma.
This broad—and incomplete—classification has its drawbacks. It is
inadequate as a guide to a programme of tick-eradication and does not assist
the administration, which has to deal with comparatively small foci of infesta-
tion by the most serious vectors of tick-borne diseases. More detailed in-
vestigations in certain districts have shown that there are small areas of R.