Paul C. Beaver

Observations on the epidemiology of ascariasis in a region of high hookworm endemicity.

In regions of the United States where ascariasis is most prevalent, hookworm (Necator americanus) infections are uncommon or absent. Conversely, in regions where hookworm infection is hyperendemic, as in the lower coastal plain of the southeastern United States, the incidence of ascariasis is generally low. Clay and other types of dense soils which predominate in ascaris areas are known to be unsuitable for the development of infective hookworm larvae and thus constitute one of the principal limiting factors (Augustine and Smillie, 1926; Rickard and Kerr, 1926). The factors responsible for the low incidence of ascariasis in regions where conditions are favorable for hookworm infection have not been well established. The

The Standardization of Fecal Smears for estimating Egg Production and Worm Burden.

It has been shown that estimates of hookworm burden can be based on egg counts in direct fecal smears that are made to a uniform density (turbidity) by means of a photoelectric light meter (Beaver, 1949). As originally described, the method is lacking in two respects. Because photoelectric light meters are manufactured in various models and patterns and, therefore, require diverse types of adapters, the standardization of smears requires a reliable method of calibrating the meter assembly; and since the meter may deteriorate or become damaged, some means of checking its accuracy from time to time is needed. The other obstacle to the general application and usefulness of the method is the lack of standardized smears offering a range of densities suitable for diverse needs and preferences. Both problems are dealt with in this study.

Morphology of the advanced-stage larva of Eustrongylides wenrichi Canavan 1929, occurring encapsulated in the tissues of Amphiuma in Louisiana.

Larval nematodes identified as Eustrongylides wenrichi Canavan 1929, from cysts in the tissues of Amphiuma means tridactylum Cuvier in Louisana were redescribed. The extent of differentiation of the sex organs was found to be greater than that of 3rd-stage Dioctophyma renale, or of the infective stage of Trichinella spiralis, and comparable with the late 4th-stage larva of secernentean (phasmid) nematodes.

Studies on the Development of Allassostoma parvum Stunkard

A little over a decade ago not a single life history was known for North American trematodes and up to the present time only ten, none of which concern amphistomes, have been experimentally established. An amphistome life history is here demonstrated through a study of larval and adult forms collected from the Ox-Bow, northeast of Urbana, Illinois. A cercaria from Planorbis trivolvis was found to encyst on crayfish and frog larvae, and when fed to bullfrogs (Rana catesbiana) and snapper turtles (Chelydra serpentina) developed into a known species, Allassostoma parvum Stunkard 1916. The extraordinary size of the terminal organs of the excretory system of the redia stimulated intensive studies on this system in both redia and cercaria stages. Sincere thanks and appreciation are here extended to Professor Henry B. Ward whose guidance and criticisms have made this work possible.

A microfilaria of exceptional size from the ixodid tick, Ixodes dammini, from Shelter Island, New York.

Thirty or more microfilariae 0.70-1.32 mm in length were recovered from the hemocele of an unengorged adult tick, Ixodes dammini, that was collected from vegetation on Shelter Island, New York. Among approximately 500 I. dammini collected from the same area only 1 other was similarly infected. Outstanding features, in addition to size, were absence of a cephalic space and the presence of nuclei in 2 or 3 irregular rows extending to the end of a bluntly rounded tail. The microfilariae apparently were ingested in a blood meal that was taken when the ticks were larvae or nymphs, and had persisted alive without development.

Studies on Protechinostatna mucromsertulatum, n. g., n. n. (Palostowwn reflexae Feldman, 1941), a trematode (Echinostomidae) from the sora rail.

In October, 1939, 12 of 39 Stagnicola palustris elodes (Say) which were collected in a marshy area near Black Creek, Wisconsin, were infected with a species of large echinostome cercaria. It was found that the metacercaria would develop in various species of pulmonate snails, and with further collections in the fall of 1940 and in 1941, the adult stage was cultured in young albino mice. In October, 1941, 6 adult worms were taken from the lower ileum of a field host, Porzana carolina (L.). With a description of those examples from the field host, the study was concluded and a manuscript was nearing completion when a paper by Feldman (1941) was published on the morphology and life cycle of the same species. Comparison of the two studies revealed minor points on which observations differed, and some additional data which Feldmans paper did not contain. The purpose of the present report is to record these supplementary data. The cercaria which Feldman obtained from Stagnicola reflexa was declared to be identical with Cercaria reflexae Cort, 1914, and the adult which was obtained from experimentally infected chicks was thought to be a member of the genus Psilostomum Looss, 1898. Thus this species was introduced into the literature as Psilostomum reflexae. For several reasons to be discussed later, mainly because of its crown of spines, this species cannot be a member of the genus Psilostomum. It represents instead a new genus. Also, there is no justification for declaring the cercaria identical with C. reflexae Cort. It resembles C. reflexae but differs from it markedly, especially in size and spination. For Psilostomum reflexae, the new name Protechinostoma mucronisertulatum, n. g., n. n. is proposed.