Aids to stockowners / by J. Walker.

  • John Walker
Date:
1930
Catalogue details

Licence: In copyright

Credit: Aids to stockowners / by J. Walker. Source: Wellcome Collection.

    29/198 page 15
    15 when ready for feeding, seeks a host, and after attaching engorges and drops in from three to seven days, and moults on the ground into an adult in about eighteen days' time. The adult male and female after attaching mate, and the adult female drops engorged in from about four to seven days, and commences to lay eggs in about six days’ time. These hatch in about twenty-eight days in the warm season. The black pitted tick (Rliip. Simns), which is also a three-host tick, hatches from the eggs in about thirty days’ time. The larva? do not attach readily to cattle or horses, but to other animals, in particular the dog, and the inter¬ mediate stages are found on smaller animals. The larvae, after engorging, drop and moult into nymphs in about twenty days’ time; the nymphs into adults in about twenty-five days. The red-legged tick (Rliip. evertsi) is a two-host tick. The young larvae are usually to be found inside the ears. They do not drop after engorging, but moult on the host into nymphs. The nymphs engorge and are ready to drop in from ten to fifteen days after attaching as larvae. The moulting (nymphs to adults) takes place on the ground, and occupies about twenty-four days. The adults usually attach to the hairless parts of the body, particularly under the tail. The brown tick (Rliip. appendiculatus) transmits the disease in its nymphal stage after the larva has fed on a sick beast, and in its adult stage after the nymph has fed on an affected animal. The red-legged tick (Rliip. evertsi) transmits in its adult stage after the larva and nymph has fed on a sick beast. Immunisation. This consists of intravenous, subcutaneous and intra- dermal inoculation of spleen pulp mixed with blood of an affected beast which produces a reaction to East Coast fever from about the fourteenth day after inoculation in a varying percentage (30 to 40 per cent) of susceptible cattle, other than calves. To complete the immunity, inoculated cattle require to be exposed to natural infection from about the twenty-first day after inoculation. A percentage of the animals which react to inoculation and a still larger percentage of the non-reactors again react bo East Coast fever on exposure, with some mortality; the death rate being greater amongst those which failed to react to inoculation.
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