THE CATTLE-TICK (HAEMAPHYSALIS BISPINOSA).

New Zealand Journal of Agriculture, Volume XXVII, Issue 2, 20 August 1923, Page 67

THE CATTLE-TICK (HAEMAPHYSALIS BISPINOSA).

INVESTIGATION OF ITS LIFE-HISTORY.

J. G. MYERS,

B.Sc., F.E.S., Biological Laboratory, Wellington.

IN February last the writer was sent to the North Auckland tickinfested area for the purpose of studying in as detailed a manner as possible the life-history of the cattle-tick (Haemaphy satis bispinosa

Neumann), which is attracting increasing notice as a pest of cattle, and to a less extent of other stock. The present article is a preliminary note on ..the progress of the investigation, with a view to placing before those concerned a few of the more salient and hitherto unknown facts which will be of assistance in the control of -the pest. It will be perfectly obvious that a complete and definite account of the life-cycle of the tick cannot be obtained until there have been accumulated observations made through every month in the year. Almost all the life-history observations in this case have been made in the field, under conditions as natural as was consistent with the isolation frequently essential for accurate observation. It is now actually demonstrated for the first time that the New Zealand cattle-tick is a “ three-host ” species, in which it resembles such other members of the genus Haemaphysalis as have so far been studied.

LENGTH OF TIME CATTLE-TICK PRESENT IN NEW ZEALAND.

One of the most difficult portions of the investigation was the sifting of evidence from various sources on such aspects of the tick problem as could not be solved by an appeal to the verifiable facts of observation. There is scarcely a person in the tick-infested area who has not some opinion, more or less hazy, but not ' necessarily any the less strongly held, as to the length of time that has elapsed since the cattle-tick was introduced into New Zealand. This tick is a tropical species with its centre of greatest abundance in India and neighbouring regions, and it has therefore almost certainly been introduced accidentally into New Zealand by the agency of man. The probability is the more strong in view of the fact that this tick is essentially a parasite of mammals, and these latter were practically unrepresented in pre-European New Zealand. .

A large part of the “ evidence ” for the existence of cattle-tick in the Dominion for thirty years or more could be rejected at once as utterly unreliable. The only spark of truth in it is based on records of the kiwi-tick (Ixodes anatis Chilton), a totally distinct species which the Maoris rightly assert to have been in the country from time immemorial. Mr. H. Munro, principal Inspector of Stock for the Auckland District, states that when he was inspecting the whole North Auckland Peninsula up to fifteen years ago the tick did not come under his notice in any way. The first occasion on which specimens actually came under the notice of an officer of the Department was in December, 1910. It may be concluded provisionally that there is yet no exact evidence as to the length of time the tick has been present in New Zealand.

There is a very prevalent belief, amounting in places to dogmatic certainty, that the cattle-tick was introduced from South Africa in saddles brought back from the Boer War by members of the New Zealand contingents. This is conclusively negatived by the fact that this tick does not occur in South Africa. Perhaps . the favourite explanation is that it came from Australia when the grass Paspalum dilatatum was first introduced from there into the north of New Zealand. This on the face of it is a more likely theory, especially in view of the close association now observed between the cattle-tick and paspalum in the infested area. Unfortunately, however, for the theory, Haemaphysalis bispinosa is by no means widespread nor common in Australia, and has probably been only recently introduced there.

LIFE-HISTORY OF HAEMAPHYSALIS BISPINOSA.

The Eggs.

The very numerous dark-reddish eggs are laid on the ground in one batch. Their glossiness is due to a liquid secreted over them by a bilobed dorsal organ, the purpose of the secretion being to stick the eggs together. In this tick, as in foreign species, it has been shown that unless the eggs ' are thus kept together in one compact bunch they will not hatch, the failure being perhaps due to resulting desiccation. . Egg clumps are deposited by the engorged female at the bases of grass and weeds, at no great distance from the spot where she fell from the cattle-beast or other host. In about two months the

eggs commence to hatch, but some three weeks before this occurs a conspicuous squarish white patch is visible on one side of the egg. This represents the accumulated excreted matter of embryonic development. '

The Larva, or Seed-ticks.

From the. eggs, now left as empty transparent horn-coloured shells, there swarm the very minute young ticks in the first stage of their active existence. In this stage they are known as “ larvae,” or "seed-ticks.” They are rather less than 5% in. in length and nearly as broad, but very flat, 1 and, in fact, before their first feed, almost transparent. The pale-yellowish almost whitish colour in which they first appear soon deepens to a darker brown, and the seed -ticks, which may be distinguished at once from all succeeding’ stages not only by their minute size but also by their possession of only three pairs of legs, proceed to swarm up the stems of grasses and herbage, by means of which they can clamber on to the hides of cattle or other stock. On such vantage - points as the tall seed-heads of paspalum they will remain day and night ■ until a suitable host should happen to brush past.'

Once on the host the seed-ticks soon thrust in their mouth-parts and commence to feed upon the blood and lymph. In the early stages these minute ticks may be present in incredible numbers on a beast and yet be entirely overlooked. Even when recognized as ticks it is quite a frequent occurrence for their connection with the cattle-tick to be stoutly denied. The writer has known the larval ticks and those of the succeeding or nymph stage to be distinguished as " horse-ticks.” The bestowal of this name is worthy of a little digression. Larval ticks so soon as or a very few hours after they have pierced the skin of a horse raise a small lump, which shows at a considerable distance, by interrupting the sheen of the coat, though the minute seed-tick itself, each one seated on such a lump, is invisibly hidden beneath the hair. Even on parting the hair over a lump there are ten chances to one against the larva being seen, since the lymphatic exudate caused even by this minute irritation soon more or less hides the tick from view beneath a covering of scurf, to the scales of which the tick itself bears a considerable resemblance. On cattle, on the other hand, apparently no lumps are formed, and. as a result an infestation of larvae of as many as six to the square inch over a large part of the animal may be entirely overlooked. The farmer is not in the habit of focussing his attention on objects so small as an unfed larval tick, and he appears to' have some difficulty in seeing them when they are actually pointed out to him. Whenever the horses of a district show a plentiful supply of lumps due to larvae it may be safely assumed that the cattle of the same district have an even greater number of larvae upon them. It must be emphasized that the larvae have no preference whatever for horses, but rather for cattle, but they are seen, even in extremely limited numbers, on the former, while on the latter they are almost always totally overlooked.

In a few days the larvae begin to show an increase in. size and to assume a dark blue-black colour, causing them to resemble, when fully fed, small beads of writing-ink among the white hairs of light-coloured hosts. This process of engorgement, by which the thin larval skin

becomes distended to its utmost capacity, takes on an average about a week, but depends to a certain extent on the position on the host. It is obvious that some portions of the animal might be pierced to better advantage with regard to blood-supply than others. Engorgement proceeds very much more rapidly towards the end, and the replete or full-fed larva disengages its mouth-parts from the skin of the host and drops to the ground.

For about three weeks, on an average, the shining-black full-fed larvae lie upon the ground, hidden among the bases of grass and weeds near where they fell from the host. Early in that period the shiningblack appearance is displaced by a misty almost mouldy look, due to the shrinking of the nymphal or next stage tissues from the distended and still stiff larval cuticle or “ skin.” At the end of the period the larval cuticle splits, and a pale-coloured nymph tick emerges.

The Nymph or Second Stage.

The nymph, although not so small as the larva, is still minute, and much less conspicuous than the replete larva from which it emerged. It may, however, be distinguished from the larva by the possession of four pairs of legs, as in the adult tick. After a longer or shorter period — most a day — nymphs, like the young larva, ascend herbage and thus reach a —the second host of the individual life-history. Most of the remarks concerning the behaviour of larva on horses and cattle respectively apply also to the nymphs. Their period of heaviest infestation is, however, as will be shown in the account of the seasonal cycle, at a different time of the year. Both larvae and nymphs -attack almost any portion of the host, except where the latter happens to be a bird, when the head, for reasons of safety, becomes almost the sole point of attachment. ' .

For a week or perhaps a little longer the nymphs suck the blood of the host until they are engorged. Then, like the larvae, they drop to the ground and lie hidden among rubbish and vegetation, while the internal changes resulting in the conversion of the nymphal tissues and the engorged blood into the structures of the. adult tick are- consummated beneath the passive exterior. In about three weeks from the time of dropping to the ground the nymphal cuticle splits, and the adult tick, at first pale and rather soft, clambers out.

The Adult.

The adult is eventually of a deep rich-brown colour, the female rather larger than the male, but both quite flat and out of all comparison less bulky than the engorged female which corresponds to' the farmer's more familiar conception of a cattle-tick. In this unfed state it is a matter of some difficulty to distinguish the sexes with the naked eye, but the vast majority are females. The males so far have proved very rare indeed. The males feed but little, and never engorge as do the females, so that the former sex keeps approximately the aspect of the female before she has commenced to feed. For this reason unfed females have been repeatedly taken for males and recorded as such.

As soon as possible after leaving the old nymphal slough and hardening its own integument the adult tick climbs herbage just as did the

younger stages, and awaits there the chance passage of a host. This is the third, host of the individual life-history. Once on the animal the female soon settles down in a favourable situation. If the host be a cow the escutcheon and neighbourhood of the udder will be perhaps the most favoured spots. The male is said to wander over the host and to stay there much longer than the female, but the writer is not prepared to say much concerning this sex until more numerous examples have been observed. The female takes, on an average, when the host is a cow, a week in which to engorge, the greater part of the swelling which makes her then so conspicuous taking place during the last few hours. She then drops to the ground and takes such shelter as may be convenient. Observations on this stage are of the utmost value in control work.

For about a fortnight the female lies as well concealed as possible while' the blood engorged is digested and finally elaborated into the substance of the numerous eggs which she then commences to lay in an almost continuous stream. The process of egg-laying may take as long as three weeks. Upon its completionher labours endedthe female dies. This completes the life-cycle.

It should be borne in mind that all the foregoing observations, which are mainly averages from large series, have been made under the conditions prevailing from February to July inclusive. There remains, however, to be considered a seasonal incidence in the lifecycle, which can be definitely worked out in detail only after a year's observations have been completed.

THE SEASONAL LIFE-CYCLE.

The relative abundance of the various stages during February, as gauged by sweeping them from seeding paspalum where they awaited hosts, was approximately 300 larvae, 1 nymph,. and 5 adults. This clearly indicates that, for the present year at any rate, February was distinctly a seed-tick period, where the seed-ticks were derived from adults which were extremely numerous, in the preceding December. If FebruaryMarch, then, could be considered a seed-tick period it became difficult to see how eggs, as popularly assumed, could be the wintering stage. Observations in the field showed that this heavy autumn infestation of larvae had practically all left the hosts by the middle of April. _• On the ground moulting had taken place as usual, and the resulting nymphs were found in May wintering at the bases of the clumps of rushes or wiwi uncus effusus) which are such a conspicuous feature of the northern —rendered all the more noticeable by the close winter grazing. The replete or full-fed larval stage is swollen, smooth, shining, and easily seen, and it must therefore be advantageous for the tick to spend the winter in the far less conspicuous nymph stage. Much of the paspalum which has served as such excellent harbourage for the seedticks in February-March is in winter eaten to a close turf. The rushes, however, remain as compact stiff clumps. In the larger paddocks a few clumps of seeding paspalum are found not yet eaten. The majority of the nymph ticks winter in the clumps of rushes an inch or two above the surface of the ground. The overwhelming number of other wintering arthropods (insects, spiders, woodlice, and their allies) in the bases of these rush clumps, as compared with those in the shorter grass and in

the paspalum tufts, indicates the general suitability of these clumps as winter quarters. It is difficult to see how ticks could survive the winter in any numbers in short, well-grazed turf. The relation of this to the question of control is obvious.

The first ticks to appear in spring are these nymphs, which come forth from their winter quarters and seek hosts about the middle of July. From then until the following winter development apparently proceeds as indicated in the general life-history just described ; but the verification of this will depend upon and guide future field-work.

HOST RELATIONSHIPS.

Although cattle are indubitably .the chief hosts of every stage of this tick, it has already been pointed out that horses may be extensively infested, especially by the earlier stages. The list of-hosts is, however, very much larger than this, and includes most of the larger animals of the North Auckland Peninsula and a few small birds. A few seedticks have been taken on the introduced skylark, thrush, and housesparrow. Probably the most important of the wild hosts, from a control point of view, is the hare, which carries all stages. Man himself is a not infrequent host, the seed-ticks being often quite a serious nuisance to children, who become infested when playing in the grass. The effects of the bite are in most cases little more than a temporary irritation ; but the writer would not dogmatize' from his own limited experience, since the effects would doubtless vary both with individual ticks and with individual men.

One point needs further stressing than it has yet received. It is repeatedly asserted that the kiwi {Apteryx australis var.) and the seagulls {Larus dominicanus Licht, and Bruchigavia novaehollandiae Steph.) are infested with the cattle-tick and act as carriers. In the case of the kiwi this is totally incorrect, being based on the discovery of kiwis infested with Ixodes anatis Chilton, a different species of tick which does not attack stock. To the untrained observer all ticks look somewhat alike. Probably the case of the gulls is open to a similar explanation, since sea-birds of several New Zealand species are infested with Ixodes eudyptidis Mask., another of the bird-ticks. Up . to the present, however, none of the gulls examined has shown any examples of ticks either of this species or of the true cattle-tick,

NATURAL ENEMIES.

In the existing literature on ticks much has been written about the length, of time ticks can exist without food. Ticks have been kept in closed vessels for over two years without apparent harm. So far as the present species is concerned, the writer has a large number of seed-ticks collected from grass-heads six months ago and still quite happy and healthy. The relation of this amazing longevity to the question of control is not so important as is usually imagined,* and the reason can only be that those stragglers which do not find a host before a certain period has elapsed are carred off by natural enemies, thus rendering possible the quite exact delimitation of seed-tick'

periods, nymph periods, and so on, without very serious overlapping. Undoubtedly the most important of these natural means of control are climatic conditions and birds. Among the latter the introduced starling (Sturmis vulgaris L.) stands pre-eminent. During a period when adult ticks are prevalent the starlings make, a speciality of these, picking them from the cattle in the fields. No examination of starlings’ stomachs at such a period has yet been made ; but in Jamaica, where the value of insectivorous birds as tick-destroyers is widely recognized, the stomach of one bird was found to contain no fewer than seventy fully engorged female ticks. Starlings have not yet been shown to carry seed-ticks, but even if they did bear the usually slight smallbird infestation the harm done in this direction would be overwhelmingly more than counterbalanced by the destruction of adult female ticks.

SUMMARY.

Haemaphysalis bispinosa is shown to be a “ three-host ” tick fact which makes its control a more complicated matter than that of the North American or Australian “ fever ” ticks, both of which are "one-host” ticks. Cattle are the chief hosts, but other animals, including some of the introduced small birds, are infested.’ Kiwis certainly, and seagulls almost certainly, do not carry cattle-ticks as is generally supposed. The winter is passed as a nymph hidden at the bases of rushes and clumps of rough grass.

This article is to be considered only a preliminary statement. All acknowledgments to the large number of those who assisted in various ways and all references to literature are deferred until the complete report is ready.

* Possibly the longevity is more important in the matter of the distribution of ticks in agricultural produce.

Note. —Illustrations of Haemaphysalis bispinosa and other ticks will be found accompanying an article by D. Miller in the Journal for January,- 1922. — Editor.