LIVE STOCK AND BREEDING.

42- Investigations on North American Ticks and their Control.

BIBLIOGRAPHY

1. U. S. Department of Agriculture Bureau of Entomology; Bulletin No. 106. 2. U. S. Dept. of Agric.; Farmers' Bulletin, No. 498.

3. U. S. Dept. of Agric. Bureau of Animal Industry, Order 187.

4. U. S. Dept. of Agric. Bureau of Animal Industry, Circular 187.

5. U. S. Dept. of Agric. Bureau of Animal Industry, Bulletin 144.

The first studies made of the life history and habits of the North Ame rican Cattle Tick (Margaropus annulatus Say) were those of Dr. Cooper Curtice (1891, 1892). In 1898 Dixon and Spreull reported studies made on Margaropus decoloratus, and the same year Prof. C. P. Lounsbury in British South Africa began his classic studies of the Ixodoidea; other investigators soon followed with work on several species of ticks and among others Dalrymple, Morgan and Dodson published an account of experiments relating to the North American cattle tick and C. J. Pound published notes on the Australian cattle tick (Margaropus annulatus australis Fuller). Also in Germany, in India, Argentina, Brazil and Jamaica many observations on different species have been made by numerous investigators.

The Bureau of Entomology (U. S. Department of Agriculture) has conducted a course of investigation on all the cattle ticks hitherto found in the United States, and in its Bulletin No. 106 an exhaustive account (including description, host relationship, geographical distribution, life history, economic importance, etc.) of these species of ticks is given. The methods employed in the studies are also given, as well as a series of plates.

From an economic point of view, cattle ticks occupy the most important position among the ticks of North America owing to the part they play in the transmission of Piroplasma bigeminum, the cause of Texas fever in cattle. It has been estimated by Dr. Mohler (1905) that the cattle tick alone is the source of approximately $ 40 000 000 (about £ 8 000 000) annual loss in the United States. Mayer (1906) has estimated the annual loss as nearly $ 100 000 000 (about £ 20 000 000).

Besides the cattle tick, Dermacentor venustus Banks which transmits to man the causative organism of Rocky Mountain spotted fever, and perhaps Argas miniatus which transmits a spirochaete to poultry, are also to be considered. A good many other North American ticks are, hitherto at least, known only as ecto-parasites of man and of domestic and wild animals.

Margaropus annulatus lives usually on cattle, but the tick is often found on horses and mules, and on deer, buffaloes and sheep. But these latter animals, with the exception perhaps of buffaloes and deer, do rot suffer from Texas fever.

Cattle ticks live only a part of their lives on their hosts, the rest being pent on the pastures.

HYGIENE

The tick larvae attach themselves firmly to the skin of their host, where the female larva remains from 21 to 66 days, during which time it moults twice (like the male) and becomes a sexually mature eight-legge p tick. It then mates with a male living on the same host and gorges with blood, attaining a length of about half an inch, after which it drops to the ground and lays its eggs on the pasture.

Egg-laying begins during the spring, summer and autumn months in 2 to 20 days, and during the winter months in from 13 to 98 days, after falling to the ground.

Egg-laying is retarded by low temperatures. It is completed in from 4 days in the summer to 151 days beginning in the autumn. During this time the tick may deposit from a few hundred to more than 5000 eggs. After egg-laying the mother tick dies in the course of a few days.

After a time, ranging from 19 to 188 days, the eggs begin to hatch. From each egg issue small six-legged larvae or seed-ticks which after a few days ascend the nearest vegetation, such as grass, herbs, etc., whence they try to reach a host by means of their long front legs.

The seed tick during its life on the pasture takes no food, and unless it reaches a host it dies of starvation. Its endurance, however, is very great, as it has been found to live without food nearly eight months during the colder part of the year.

The United States Congress in 1906 empowered the United States Secretary of Agriculture to inaugurate a plan of cooperation with the authorities of Southern States for the eradication of the cattle tick. The Federal appropriation for the fiscal year 1907 was $ 82 500 (about £ 16 500) and for 1908 $ 150 000 (about £ 30 000). Annually since then $250 000 (about £50 000) have been appropriated for this object. At first only 7 States cooperated with the Federal Government in the work of tick eradication.. Now all the States interested in the question (with only one exception) have undertaken cooperation with the U. S. Bureau of Animal Industry.

In the eradication of ticks, either the pasture rotation method is used or the ticks are killed by insecticides applied by swabbing, spraying or dipping the cattle.

In the pasture rotation system the cattle are kept between March and September for 20 days in a pasture in which there are no ticks, then for 20 days in another such pasture and lastly for again 20 days in a third enclosure; all these pastures must be free from ticks, so as to avoid the cattle becoming again infested with the parasites. The ticks (females) previously attached to the animals have in the meantime droppet off from their hosts and these are freed from them so long as they keep in tick-free enclosures. The three pastures grazed first must not be restocked with cattle until all the larvae hatched out from the eggs have died of starvation.

The carrying out of this rotation system, however, presents some difficulties, consequently the tick destroying agents, such as oils and arsenic, are becoming increasingly popular. Arsenical dips are very effective and during the past few years have come into much favour.

The cattle and horses are to be bathed in this dip at intervals of not more than 20 days until no more ticks are to be found on the animals.

For dipping purposes vats made of concrete are useful, and they may, in many cases, be built by the cooperation of all the farmers of a community. Up to April 15, 1912, 162 648 square miles have been freed from ticks, and this area is separated from the tick infested country by a strict quarantine. (1)

The accompanying table shows the progress of tick eradication.

43 - The Tick Problem in South Africa (2).

MOORE, WILLIAM (School of Agriculture Potchefstroom) in: Journal of Economic Entomology, Vol. 5, No. 5, pp. 377-384. Concord, N. H., Oct. 1912.

The following is a list of ticks and diseases transmitted by ticks in South Africa.

(2) See: No. 2198, B. July 1911; No. 2425, B. Aug.-Sept.-Oct. 1911; No. 146, B. Jan. 1912; Nos. 358 and 359, B. Feb. 1912; No. 810, B. May 1912; No. 934, B. June 1912. (Ed.).

Besides the ticks which are known to transmit diseases, there are many others which attack domesticated animals. Among these Ixodes pilosus Kock attacks sheep, goats, oxen, horses, etc., and is supposed to be the cause of a paralysis of sheep in Cape Colony, and Hyalomma aegyptium Linn., the Bont leg tick, may be found in the adult state on all domestic animals, and is thought by some to cause abcesses on the animals. Other ticks whose injury may only amount to tick worry, are Ixodes rubicundus Neumann, Rhipicephalus oculatus Neumann, R. sanguineus (Lat.), R. lunulatus Neumann, R. duttoni Neumann, R. bursa Canestrini & Fanzago, R. nitens Neumann, Amblyomma variegatum (Fabr.) and sometimes A. marmoreum Kock.

The life-cycle of many of the common ticks has been worked out by Dr. Theiler, C. P. Lounsbury and C. W. Howard. The eggs of B. decoloratus are laid in about five days or more from the time the engorged female drops from the hosts and hatch in from three to six weeks, in winter a longer period is required. The larvæ may live for six or eight months without feeding. The moult from larva to nymph and from nymph to adult is performed, without leaving the host animal, in about three to four weeks. The eggs of R. evertsi hatch in about 30 days, and the larvæ can exist for seven months without feeding. The moult from larva to nymph is performed upon the animal in about ten to fifteen days. The engorged nymph drops from the animal and moults on the ground, seeking a second host for its adult existence. The adult tick may live for as much as a year, should it not find a suitable host; it remains on the host animal from six to ten days. The life cycle of R. appendiculatus is typical for R. capensis, R. nitens and R. simus and is given for the group. The eggs are laid by the engorged female in about six or more days from the time she drops from the host animal. These hatch in from 28 days to several months, depending upon the temperature. The larva remains on the animal for about three to eight days, after which it too drops to the ground to moult - which is accomplished in about 21 days. The nymph attaches itself to a second host animal and remains for from two to seven days, when it drops off to moult to the adult. The second moult occupies about 18 days. The adult remains on the third host for a period of four to seven days. The larval tick can exist for seven months should it not find a host, the nymph six and one-half months, and the adult nine and one-half months.

A. hebræum also has a life cycle much similar to R. appendiculatus. Three hosts are sought, the larva remains on the animal from 4 to 20 days, the nymph 4 to 20 days, and the adult 10 to 20 days. H. aegyptium differs from the above species in that the larvæ attach themselves to various birds and to hares. The larva moults to the nymph while on the bird, but the engorged nymph drops to the groud to moult to the adult. The adult attacks domesticated animals, being often very abundant upon oxen. A. marmoreum differs from H. aegyptium in that it is the larva or nymph which attacks oxen and goats, while the adult and also the nymph are very common upon tortoises.