Page images
PDF

significance of morphological variations such as the lightly punc_ tate forms from Equatoria Province birds in an area where most of those parasitizing mamals are heavily punctate? What “biological strains" or varieties exist in Africa and do some or all of these react with equal facility to domestication? What is the life cycle under field conditions and what are the host predilections of the immature and adult stages away from human and domestic canine habitations? Why does parasitism of persons _ and bou_ tonneuse fever _ a ear to be so much more common in north. western Africa than e sewhere on this continent (and why is boutonneuse fever absent in Egypt)? Just what is there about

a habitation shared by man and dogs, whether it be an African

hut or a Florida mansion, that is so zmich more attractive to

this tick than a fox den in a rocky hillside? Is the greater incidence of parasitism of all domestic non.canine animals in

the Near East, as compared with tropical Africa, mrely a matter of host availability? These are but a few of the innumerable inquiries that suggest themselves as a result of our lack of specific information concerning this common tick.

[merged small][graphic]

The life cycle of R. s. san 'neus has been studied, under laboratory conditions, In Christophers (19070), Hooker, Bishopp, and Wood (19l2)*, Patton and Cragg (1913) with techniques i1_ lustrated, Nuttall (1915), and Regendanz and Reichenow (1931). In the discussion below, less specialized life cycle reports or studies for special purposes are noted following the summary of the above_mentioned papers.

A11 observers agree that this is a three_host tick. Varia_ tion in reports of length of feeding time of each stage may be due to the kind of host used in laboratory experiments (see below). During nonfeeding phases temperature and humidity exert considerable influence on the length of the life cycle. Nuttall concluded that feeding times are constant, irrespective of temperature variations, and that only the nonfeeding phases are affected by these variables (see also discussion of this aspect under R. dromedarii, p. 428).

[graphic]

*The extensive data in this important paper are not reviewed here. In Nuttall's laboratory experiments, larvae fed on dogs and rabbits, nymphs on dogs, jackals, and hedgehogs, and adults on dogs and jackals. Larvae commenced feeding three to seven days after emergence, nymphs began about the same length of time after molting, and adults about a week after molting. Larvae fed for three to eight days (mostly four days) (temperature ranged from 6.500. to 20°C.). Nymphs fed for three to eleven days (mostly four days), on the dog or jackal; but when hedgehogs were used, the feeding time (ten to seventeen days) was about doubled* (temperature ranged from 8°C. to 18°C.). Females fed from one to three weeks (mostly eight das) but males remained attached indefinitely and transferred to another host if the first animal

died.

As already stated, the length of intervals during which ticks are off the host appears to be influenced by temperature (though more exact and extensive research is certainly required). In Nuttall's tests, eggs hatched in from seventeen to nineteen days at 30°C. but required 75 days at 12°C. Larvae melted to n phs from five to eight days after completing feeding (at 30°C.)m and nymphs molted to adults in eleven or twelve days after feeding (at 30°C.). Oviposition commenced three to six days (average three or four days) after females left the host, when maintained at 30°C.~ but at 12°C. they commenced oviposition after 25 days.

9

Egglaying lasted for from nine to fifteen days.

The life cycle, under favorable conditions, may be completed in as little as 63 days. Under unfavorable conditions, it may be

prolonged for many months.

Z?By way of contrast to Nuttall's findings and because the records of Christophers (19070) "are not complete and do not indicate the temperature at which the specimens were reared", Sapre (1945) undertook similar experiments in India at 7500 feet altitude, with dogs said to be the hosts for all stages. Nonfeeding ticks were observed at 22°C. (eight degrees lower

[graphic]

*A similar situation has been reported for Ornithodoros arenicolous

whose females feed on mice for 45 minutes but on nedgehogs for 70 minutes (average), and whose males feed on mice for 45 minutes and on hedgehogs for 57 minutes (average) (Hoogstraal 19530).

than the temperature in Nuttall's experiments) and at 80% to 9Q R.H. Unfortunately for purposes of comparison, Sapre neglected to report how soon after hatching larvae commenced feeding and other such details. In his summary, Sapre stated that feeding periods remain constant irrespective of temperature variation but nonfeeding periods appear to be inversely proportional to an increase or decrease in temperature. In the introduction it was stated that nonfeeding ticks were observed at 22°C. and the report of the experiment shows no comparative data for length of feeding time at different temperatures. The sumary stated all stages were observed at 22°C.; the text stated hosts were maintained at anywhere from 1.490. to 11.696. for larval feedingé at 2.9qC. to 5.l°C. for nymphal feeding, and at ll.0°C. to 14.6 C. for adult feedingi7

Survival of unfed larvae may be as long as 253 days; nymphs appear to be less hardy, for only a few survived for as long as 97 days. Adults may live without food for as long as 568 days, with females appearing to survive longer than males when unfed.

Z_Nuttall;7

Nuttall noted that females may outnuber males by two to one and Sapre reported the sex ratio as three females to two males. Copulation occurs on the host; males may move about on the host and fertilize several females.

Nuttall counted 1400 eggs to 3900 eggs from individual females (Sapre said his females averaged 2140 eggs). Lombardini (1950) counted from 4000 to almost 5000 eggs. Regendanz and Reichenow observed that the number of eggs varies with the size of the female but averages from 3000 to 4000. However, not all eggs are deposited. When the female at last becomes exhausted and senile, some mature eggs remain in the oviducts and egg cells remain in the ovaries. A good egg batch, from an engorged fa. male measuring from 8.0 mm. to 9.5 mm. long, weighs from 0.09 to 0.1 gram.

A classical study on oviposition and survival of eggs and larvae under certain conditions has been reported by Lombardini (1950). Five females laid from 1.000 to almost 5000 eggs each, ovipositing for from 21 to 29 days each. The number of eggs laid in the latter half of the period dropped considerably,

though erratically, from week to week. The mechanism of oviposition in the kennel tick is similar to that reported by Nuttall and War. burton (1915) for Haemaphysalis punctata. The cephalic gland, or - gene's organ, secre es a lquld covering as each egg is emitted. This substance protects the eggs from dessication but absorbs oxygen, even under water. Immersed eggs hatched in 51 days as compared to 38 days in the air (20°C. to 25°C.), althowh some

1 embryos were killed by a Fusarium fungus. Even larvae survived from 30 to 35 days in spring water, while others, unfed, succumbed

in twelve days in moist petri dishes. Larval longivity when immersed in various fluids was also noted. Illustrated with handsome photographs of the egg covering, various glands and organs, the Fusarium which attacked eggs, and details of the larval external structure including integumentary sense organs,

this paper should be studied by anyone seriously interested in tick biology.

Other laboratory hosts reported by various workers have been

hamsters for the larval and nymphal stages (Malamos 1938). Larvae detached engorged in six days from hamsters. Nieschulz and Wawo. Roentoe (1930) used guineapigs for feeding all stages of the tick; mice were also used for larval feeding, although guineapigs were preferred. Feeding time was stated to be 24 hours for larvae and two or three days for nymphs. Dogs were preferred for adult feeding. These experiments, undertaken at 26°C. to 27°C. and

at ordinary (high) humidity (of the Netherlands), are notable

for the rapid feeding of the immature stages (ticks originated from Java). In contrast, Blanc and Caminopetros (1931), when using ground squirrels, or sperophiles, Citellus citellus, in Athens, noted larval feeding times of five to eight das. Kbrshunova and Petrova.Piontkcvskaya (1949) fed all stages on guineapigs in their studies of boutonneuse fever in the Crimea. Blanc and Bruneau (1948) used guineapigs for feeding immature stages and a hedgehog as adult stage host. A brief abstract

of rearing results using white rats and guineapigs for larval

hosts and dogs for nymphal and adult hosts has been presented by Luttermoser (1947).

Ecology

In the preceding section on biology of the kennel tick

the number of queries raised suggest how much information is lacking on the ecology of this parasite.

In Egypt it is certain that there is an urban race, attacking dogs almost without exception, and a field race that parasitizes rodents, hedgehogs, hares, and, when available, domestic animals. The field race occurs only on the Mediterranean littoral, rarely in scattered desert areas and oases, and in conjunction with a. few rodents of cultivated areas. The domestic race is common in urban and settled areas; along with hyalonnnas it is almost the only ixodid ever found in those desert areas that support some grazing. However, the propensity of the domestic race for seeking out favorable niches of human habitations and domestic animals, which are always sheltered from thieves a.nd from pedators in these areas, causes it to be more localized than are its ubiqusl... tous field companions, such as H. excavatum. The actual relations of urban and field races we hope to determine as early as possible.

In tropical and southern Africa, it appears that R. s. neus is generally distributed through the warm and humid zones 0

the continent. In the more arid parts of this area, its presence or absence seems to be dependent largely on human cultural patterns, especially of pastoral tribes (see Cattle Hosts, page 698). Whether urban and field races exist in Africa south of the northern deserts is at present difficult to determine from available data.

[graphic]

Most observations on host parasite relations presented below apply to domestic populations.

Larvae attach to the host mostly in hairy places but may oc_ cur anywhere on the body. Nymphs are found indiscriminately among the fur or elsewhere. Adults are especially common on and in the ears, though they may attach along the nape, between the toes, or

anywhere else. Specimens on birds are usually found on the crown or about the ears, eyes, or bill.

Females often creep upward on walls after leaving the host and may hide tightly wedged in narrow cracks as high as fifteen feet above the ground (Christophers l90’7C). Eggs are deposited, either near the ground or high above it, in crevices in woodwork,

under plaster, whitewash, or paper, or, out.-of..doors, under stones (Lewis 1931+, Roberts 1935, du Toit 1947).

Tremendous infestations frequently occur. In Cairo, one may see houses "crawling with" kennel ticks and mongrel dogs with more

« PreviousContinue »