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Experiments to Determine Whether Infective Larvae of Wuchereria bancrofti Can Migrate from the Abdomen of the Mosquito Intermediate Host

1945; American Society of Parasitologists; Volume: 31; Issue: 4 Linguagem: Inglês

10.2307/3273002

1937-2345

Walter L. Newton, Ivan Pratt,

Insect symbiosis and bacterial influences

In the course of dissecting mosquitoes experimentally infected with Wuchereria bancrofti, the authors found many specimens containing infective larvae in sites other than the head and proboscis, particularly in the abdominal cavity. It was of practical interest to find out whether or not infective larvae occurring in the abdominal cavity are capable of migrating forward to the proboscis. If free migration within the mosquito could be demonstrated, it could be assumed that infective larvae occurring anywhere within the mosquito could reach the proboscis and thereby be involved in transmission. In the event that infective larvae occurring within the abdominal cavity do not migrate forward, it should be possible to demonstrate one or more of the following phenomena: That there is some anatomical barrier to the forward progress of the larvae once they have reached the abdomen, that there is some physiological reaction on the part of the mosquito which engulfs or kills the larvae, or that migration on the part of the larvae is indifferent; i.e., there is a general migration away from the thorax, but once the larvae have escaped this area there is no impulse to migrate elsewhere. No anatomical barrier has been observed. To the contrary, the open-type circulatory system of the mosquito would seem to provide an excellent passage for forward migration of the larvae from the abdomen. There has been no evidence of encapsulation or death of the larvae within the abdomen of mosquitoes that permit development to the infective stage. Finally, mosquitoes dissected shortly after the larvae have become infective contained most of the larvae in the abdominal cavity; whereas, specimens kept several days longer contained fewer larvae in the abdomen with a greater proportion of them in the thorax, head, and proboscis. This would indicate that larval migration is not aimless and that there is a tendency for larvae in the abdominal cavity to migrate forward toward the head. In view of the above, it was the opinion of the authors that infective larvae of Wuchereria bancrofti were both capable of and inclined to migrate out of the abdominal cavity toward the head and proboscis. There has been little, if any, experimental work to prove or disprove the theories regarding the migration of infective Wuchereria bancrofti larvae in the mosquito host. Yamada (1927) suggested that the infective larvae migrated from the thorax to the abdomen and then to the head. Highby (1943), while working with Dipetalonema arbuta, actually observed the infective larvae migrating freely from one part of the body to another and from the proboscis back to the abdomen. To provide data on this point, an experiment was set up to determine whether the larvae are able to make their way out of the abdomen. The technique consisted of transferring infective larvae to the abdomen of a non-infected mosquito. If the