Experimental infection of Ancylostoma caninum in mice. II. Migration and distribution of larvae in tissues after oral infection

Observations on the feeding behaviour of parasitic third-stage hookworm larvae

The feeding behaviour of parasitic 3rd-stage larvae (L3) of the hookworms Ancylostoma caninum, A. ceylanicum and Necator americanus was examined. Less than 11% of A. caninum L3 recovered from the small intestines of dogs infected orally were feeding at 4-48 h post-infection (p.i.), and none of the A. ceylanicum L3 recovered from the intestines of orally infected hamsters had resumed feeding. All L4 of both species recovered at 36 and 48 h p.i. had resumed feeding. On the other hand, approximately 16% of the A. ceylanicum L3 recovered from the skin of percutaneously infected hamsters at 18 h were feeding, and the percentage feeding increased to nearly 58% at 44 h p.i. Necator americanus L3 recovered from the skin of percutaneously infected neonatal hamsters resumed feeding at 6-12 h p.i. and reached 90-94% by 18 h. Feeding began to decline at 66 h, and reached 29% at 120 h p.i. This decrease was associated with the migration of larvae from the skin to the lungs. By 192 h p.i. over 95% of the larvae had reached the small intestine, and all had moulted to the L4. The results indicate that parasitic L3 resume feeding in the skin during percutaneous infections, and suggest that feeding by hookworm L3 correlates with the resumption of development.

Experimental infection of pups with Ancylostoma caninum larvae from an abnormal host, the chicken

The migration and distribution of Ancylostoma caninum larvae in the tissues of chickens, infected orally with 1,000 larvae, were studied. Larval yield at necropsy from different organs after digestion with artificial gastric juice revealed a 62.9% recovery four hours after inoculation, followed by a sharp decline to 5.4% at 72 hours. Larvae were found in the heart within four hours, the lungs within eight hours and the liver within 12 to 18 hours but no larvae were recovered from the spleen, kidney or brain. Migration in the muscles of head, neck, thorax and abdomen was detected at 12 hours and was maximal at 36 hours. The establishment of patent infection in the definitive host was studied by feeding infected chicks to hookworm-free pups (one chick/pup) 48 hours, 7 days and 14 days after infection. The mean worm burden at necropsy was highest (15) in the pups fed with chicks 48 hours after infection and was three and nil in the other groups respectively.

Experimental infection of pups with Ancylostoma caninum-infected mouse tissues

Migration and distribution of Ancylostoma caninum larvae in the tissues of mice orally infected with 1000 larvae, and establishment of patent infection from the mice to the definitive host, were studied. Larval yield from different organs of mice, after digestion with artificial gastric juice, indicated that the highest recovery was at 4 h post-infection (62.8%), and thereafter a slight decline occurred up until 30 days post-infection (51.5%). Migration of larvae to the lungs occurred within 4 h, to the liver within 12 h and into the heart within 24 h. No larvae were recovered from spleen and kidney tissues. From the 9th day onwards larvae were also recovered from the brain. Migration in the muscles of head and neck occurred within 4 h, in the thoracic and abdominal muscles at 24 h and in lumbosacral and leg muscles at 48 h. The establishment of patent infections in the definitive host was studied by feeding the orally- and percutaneously-infected mice to hookworm-free pups at 10 and 30 days post-infection. The mean necropsy worm burden in the pups fed with the orally-infected mice was comparatively higher than in the pups fed cutaneously-infected mice.

Infectivity of Ancylostoma caninum in dogs by different routes of inoculation

Infectivity of A. caninum in dogs inoculated with 500 larvae by different routes (percutaneous, subcutaneous, intravenous, per os, through a stomach tube and foot pad) was studied by ascertaining the worm burden at necropsy 21-27 days post-infection. Infection through foot-pads yielded the maximum number of worms. The percentage of worm establishment using foot-pad inoculation was 73.8%, followed by subcutaneous (49.0%), percutaneous (45.0%) and per os (35.0%) routes. These results show that active penetration of the larvae through skin and particularly foot-pad is the most favourable mode of infection of dogs.

Pulmonary superoxide dismutase activity in the mouse infected with Ancylostoma caninum larvae

Albino mice were infected per os with 1000 infective larvae of Ancylostoma caninum and pulmonary superoxide dismutase activity was studied after completion of lung migration. The total superoxide dismutase activity per mg of lung protein was elevated by 15% in infected mice. Of the two forms of superoxide dismutases studied, that containing Cu-Zn was elevated by 44%. This suggests that A. caninum in mice may result in histopathological changes leading to transient pulmonary oxygen toxicity.

Experimental ancylostomiasis in chickens: effect of various dose of infective Ancylostoma caninum larvae on their migration and distribution

White leghorn chickens, when infected with repeated doses of Ancylostoma caninum larvae, expel the larvae at a faster rate than when infected with a single dose. This suggests that the initial dose induces some resistance in the host. An initial dose of 1000 and 2000 larvae, followed by a 2nd dose of the same order, induces resistance in the alimentary tract causing the entire larval burden either to migrate to other tissues (organs) or to be expelled in 24 h.

Experimental infection of chickens with Ancylostoma caninum: migration and distribution of larvae in tissues

Two hundred one-day-old male white leghorn chickens (Gallus domesticus) divided into 4 groups were inoculated with a single dose of 500, 1000, 2000 or 4000 filariform larvae of Ancylostoma caninum. Larval recoveries were made from different tissues at intervals from 4 hours to 72 hours after infection. Larval migration in the heart took place within 4 hours in all the groups except group A with 500 larvae and in thoracic muscle at 8 hours. Larvae also migrated into liver, lungs and neck muscle within 12 hours and into leg muscle at 18 hours. No larvae were recovered from the muscles after 72 hours of infection. Larvae did not migrate into kidney, spleen and central nervous system throughout the experimental period.

Intestinal mast cells during experimental ancylostomiasis

The alterations of mast cell counts induced in the gut of swiss albino mice by infection with Ancylostoma caninum larvae have been studied, both in single and multiple infections. It was found that mast cell rise was greater in females than males. In singly infected animals, mast cell increase was influenced by the infective dose of inoculated larvae. In case of repeatedly infected mice, mast cell counts were decreased because of their earlier degranulation.

Experimental infection of Ancylostoma caninum in mice. III. distribution of larvae after repeated exposures to infection

Different groups of mice were infected with various single or repeated doses of larvae of Ancylostoma caninum. Considerable loss of larvae occurred in the immunised groups when compared with their counterpart unimmunised groups. Larval migration and distribution in the different tissues was less in immunised mice, as most larvae were expelled from the gastrointestinal tract. This resulted in a poor onward larval migration to liver, lungs, brain and muscle regions in immunised groups. The heavily immunised group infected five times was most affected and a significant lesser larval distribution in various organs and muscle region observed.

The distribution of Ancylostoma caninum larvae in the central nervous system of the mouse infected with single or repeated doses

The distribution of Ancylostoma caninum larvae in the various regions of the central nervous system of mice of previously uninfected or reinfected groups was studied. Although a dose of 4000 larvae was lethal, the distribution of larvae was not appreciable in the CNS. Many larvae were recovered from the cerebral hemispheres and cerebellum of infected mice whereas no incidence of eye involvement was observed in any mouse. In the reinfected mice groups there was a much lower recovery than in the previously uninfected groups in the latent period of study.