Observations on the morphology and life-history of Gaigeria pachyscelis Raill. and Henry, 1910: a hookworm parasite of sheep and goats

Abstract

1. The hookworm, Gaigeria pachyscelis, is a very common parasite of sheep in South Africa; it is also found in the Congo, India and Java. In South Africa it is practically confined to the more arid regions, namely South West Africa, N.-W. Cape and Bechuanaland, where it is one of the most serious parasites affecting the sheep industry. 2. In South Africa the hosts are sheep and goats. It has been reported from cattle in other countries, but this is doubtful; the writer has not found it in cattle, neither was he able to infect calves artificially. Its presence as a natural infection in an Indian antelope is reported. 3. The larvae during their free life pass through three stages, each of which is separated by a moult. The cuticle of the first stage is shed, but that of the second stage is retained by the third stage larva as a protective sheath. 4. Under suitable conditions of aeration, humidity, food and temperature, mature larvae are developed in eight days. These larvae are climbers, skin penetrators, positively photo- and thermotropic, but their resistance to drying is very weak. 5. Infection of the host is shown to be through the skin, and all attempts at bringing about an infection through the mouth have been unsuccessful. 6. After entering the skin, the larvae proceed to the lungs, presumably via the blood stream and heart. In the lungs they remain about 14 days during which time the third stage larvae grow, moult and pass into the fourth stage; this larva possesses a globular provisional mouth capsule provided with a dorsal tooth and two subventral lancets. At first the sexes are not differentiated, but later the females may be recognised by their long pointed tails and the males by their short and stumpy tails. 7. The larvae leave the lungs from the 13th day onwards, and travelling up the bronchi and trachea reach the mouth where they are swallowed and so reach the small intestine. Here the larvae attach themselves to the villi and suck blood. The larvae grow and in about a week prepare to undergo another moult and pass into the final or 6th stage. During this transition the provisional buccal capsule is replaced by that of the adult worm and the details of the male caudal bursa also become differentiated. 8. After moulting, the adolescent parasites continue to grow, the sex organs become mature and the worms become fully grown and begin to pass eggs from about the l0th week after infection. 9. The development of the male and female genital organs is followed, as well as that of the male caudal bursa. 10. A comparison is made with related hookworms of the hatching of the egg, the biology of the infective larva, and the development of the mouth capsules. 11. The morphology of the Cephalic and Cervical glands and of the male and female Genitalia is described. 12. The status of the genus Gaigeria is maintained.