Page images

ARABIA: mum (Sanborn and Hoogstraal 1953. Hoogstraal, ms.).


H. leachii leachii, in the adult stage commonly parasitizes domestic dogs. Its local incidence on dogs varies from greater to less than that of the kennel tick, Q. s. sanguineus. Locally, R. simus simus is sometimes also a common parasite 0 dogs. On ?¢i1H'aT11’ma1_—s, H. 1. leachii is frequently numerous on the Canidae (foxes, huting dogs, and jackals). It is, in comparison with the subspecies muhsami, rare on the various families of smaller carnivores such as the viverrids, which are tropical Africa's most common carnivores. On larger Felidae, lions, leopards, cheetahs and the like, the subspecies leachii may occur in either larger and smaller nubers than muhsami Efit present data do not suggest that the large cats are Hosts of preference. Records of H. 1. leachii from smaller cats and from domestic cats are

rare indeed.

Doestic animals, other than dogs, are parasitized only exceptionally. Under a very few local conditions cattle may be attacked. Possibly tribal customs, in which man, cattle, and dogs sleep in the same hut or compound, account for these instances.

Larvae and nymphs usually parasitize common field rodents, especially Arvicanthis and Masto s, in their nests. They are said also to feed on domestic dogs (see BIOLOGY below). RareLy one finds a few nymphs, along with considerably larger numbers of adults, on wild canines. This would indicate that, under the influence of some yet uknown factors, nymphs have left rodent burrows to feed elsewhere, or that an apparently small proper. tion of the nymphal population does not feed on rodents.

Inasmuch as it is impossible to distinguish which of the two subspecies of_§. leachii most authors are referring to, the only data that may be used in this section are from the present observations and those of the very few recent students who have differentiated their material. A more exact study of available data will be presented in a subsequent report.

[merged small][merged small][graphic]

Nuttal1's (1913B) and Nuttall and Warburton's (1915) summary of Nuttall's and of Lounsbury's (l901,l902A,l904A) observations on rearing H. leachii (most likely H. 1. leachii) are essentially as follows:- This tick requires thrge hosts upon which to feed during its larval, nymphal, and adult stages. About a week after molting each stage readily attaches to the host, which under ex rimental conditions may be a number of different BBIEEIE,

J60 a , og, ferret, hedgehog, goat, or rabbit: It appears to be immaterial upon which of these hosts the ticks feed. Larvae and nymphs feed for three to seven days (two to three days: Lounsbury), occasionally longer. Females attach for eight to sixteen days. Males may remain upon the host for many weeks. Air temperature, within the limits observed (9°C. to 23°C.), appears to exert little or no influence upon the time ticks remain upon the host, "the warmth from the animal being doubtless sufficient to keep the ticks active".

The time required for metamorphosis is influenced by temper; ature. Larvae hatch after 26 to 37 days at 20°C. or after 58 to eighty days at 12°C. to 13°C. Nymphs emerge, as a rule, after thirty to forty days. Adults emerge after fifteen or sixteen days at 24°C. to 26°C., but require up to seventy days at 14°C.

The unfed tick survives for long periods under favorable conditions. In small corked bottles maintained at about 12°C., larvae are still active after 169 days, nymphs after 52 days, and adults after about 210 days.

Males and females placed simultaneously upon the host scatter but in two or three days both sexes are found attached in close proximity to each other. Copulation occurs upon the host (HH observation). Lounsbury saw marked males detach and reattach close to females. A male may mate with more than one female.

After a replete female abandons the host, the interval before egglaying commences is markedly influenced by temperature. Females held at 23°C. begin oviposition after three to five days; at 1690. to 21°C. after fourteen to eighteen days; at lower ten;

peratures after 24 to 60 days. Whereas an occasional female dies as soon as oviposition is completed, others may survive for a few days or, exceptionally, for a month. One tick deposits from 2400 to 4800 eggs.

In nature, the yellow dog_tick doubtless may produce two generations a year. Lounsbury reared three generations a year in an incubator. Taking average figures for ticks raised under favorable conditions, the cycle may be completed in l23 days, as follows:

Preoviposition 1. (23°c.)
Oviposition to hatching 30 (2o°c.)
Larval prefeeding period 7
Larva feeds 5
Premolting period 31 (l7°C.)
Nymphal prefeeding period 7
Nymph feeds 5
Premolting period 15 (2A9C.)
Adult prefeeding period 7
Adult (female) feeds 12


The distribution of H. l. leachii has been determined for South Africa by Theiler and Fobinson ll953A). The most important factor in limiting this tick's spread there is increasing aridity. Twenty inches of annual rainfall, irrespective of vegetation type, appears to be the critical level there.

However, in northern Sudan, where rainfall is absent or considerably less than ten inches annually, §. l. leachii is still fairly common on foxes.

In the Nile Valley of Egypt, where rainfall is nil to exceedingly low, the tick thrives. But, it should be stressed, the

microhabitats of its larval and nymphal host, the grass rat, Arvi_ canthis 2. niloticus, are more humid than elsewhere, situated as


they are beside irrigated, cultivated fields or in dykes. we have never found these ticks in burrows in the desert, even on the Mediterranean littoral where burrows are frequently patently damp. Foxes that pick up newly_molted adult ticks, probably from vegeta_ tion near grassrat burrows when they forage in cultivated areas

at night, retreat to very dry desert caves and dens to rest by day. In these situations, evaporation from the host skin may be the factor that allows the parasite's survival.

A comparative study of the survival of Northeast African and South African populations under local conditions of humidity and temperature should be of considerable interest.

Theiler and Robinson (1953A) have also found that H. l. leachii does not occur in those parts of South Africa with over-sixty days of heavy frost per annum. It is generally absent from the arid Karroo except where grasses are present. Altitude does not effect the distribution of the yellow dog_tick within the limits of critical frost days noted above. Variability of incidence in various zones of South Africa is also discussed.

According to Lewis (193911), H. leachii (probably including both subspecies _ HH) occurs in all districts and altitudes of Kenya but seems to prefer the shelter of dense shrub and grassy woodlands. In some areas it is more common on dogs than is §._s.


Theiler and Robinson (loc. cit.) state that the immature stages of H. l. leachii may feed oH'3og§T' Our experience in East Africa, Egpt,-~a indicates that nymphs are very rarely found on roaming wild carnivores such as mongooses, civets, and jackals, but that larvae and nymphs frequent rodent burrows. Onderstepoort records (Theiler, correspondence) show one hunred collections of nymphs from murid rodents, one from cattle, one from shrews, one from Felidae, one from hares, eight from elephant shrews, three from mustelids, five from springhaas, four from squirrels, three from mongooses, and one from civet. It is obvious that many factors governing the life cycle and possible variability in host preference of immature stages remain to be determined from field studies.

Roberts (1935) found larvae and nymphs in the Nairobi area common on various field rodents and in their nests. These are

the same as those listed for R. s. simus (Page 743). The writer's experience in other parts of Kenya in general confirms Roberts‘ findings. However, Roberts observed that nests of Mastogs (= M_us_) coucha near the surface of the ground rather than deeper nests are preferred by H. leachii, but I do have numerous records from deep. er nests of grassrahs. This factor also requires further study (See R. s. simus, page 71.6). It is of some interest to note that all sT)ec':|".mens ‘Ehat have been reared in our laboratories from nymphs from rodent nests in Kenya, the Sudan, and Egypt have been sub. species leachii.

The chalcid wasp parasite Hmterellus hookeri has been bred

from nymphs in South Africa (CooIey I92'9,I9f§Z). This subject is further discussed under H. 2. sanaeus (page 710).

MAN: Boutonneuse fever (Rickettsia conorii).

Ebtperimental evidence indicates efficiency as a. vector of Rocky Mountain spotted fever (Rickettsia rickettsii).


MAN AND ANIMALS: Q fever (Coxiella burnetii).
DCMESTIC DOGS: Canine babesiosis (Babesia canis).

[merged small][graphic][merged small][merged small]

A gynandromorph of H. leachii (probably subspecies leachii) has been described a.nd illushraha by Santos Dias (19530). The misshapen specimen of H. leachii described and illustrated by Nuttall (19ll.A), and wIdeIy quoted by subsequent authors, refers to the Asiatic subspecies indica Warburton, 1910. Very slightly misshapen specimens, due to In} , of both African subspecies have been described and illustrated by Santos Dias (l955A). The measurements and increase in relative size from stage to stage have been studied by Campana.Rouget (1954) , apparently from data in Nutta.ll's Monograph.

« PreviousContinue »