Genus Paragonimus Research Articles

Viability of a Self-Fertilizing Strain of Philophthalmus megalurus (Trematoda: Digenea)

A self-fertilizing strain of Philophthalmus megalurus was carried through 3 successive life cycles with little or no deleterious effects when compared with cross-fertilizing strains. No significant differences in the parameters of growth, eggshell formation, and the production of viable miracidia and cercaria were noted. However, significant reductions in recovery rates of adults from monometacercarial infections in the 2nd and 3rd generations were found. The effects of self-fertilization on different species of digenetic trematodes and cestodes and possible evolutionary adaptations for survival of self-fertilizing strains are discussed. The question of whether the hermaphroditic digenetic trematodes reproduce by selfor cross-fertilization has interested parasitologists for many years. Stunkard (1957) asserted that parasitic flatworms do not occur in interbreeding populations and reproduce by self-fertilization. Smyth (1962) suggested that self-fertilization is the most common type of reproductive process in the digenetic trematodes. On the other hand, Martin (1969) stressed the importance of intraspecific cross-fertilization for interpreting the biological species concept based on data from a study with Philophthalmus megalurus by Nollen (1968) and other studies utilizing different species of digenetic trematodes. The importance of cross-fertilization for development of the life cycle is another question to be answered now that it is known cross-insemination takes place in some species of digenetic trematodes. In the genus Philophthalmus the situation seems to vary among different species. Nollen (1971a) found that isolated adults of P. megalurus grow as well as those in multiple infections, and he was able to carry this eye fluke through one complete life cycle with no evidence of deterioration. On the other hand, Fried (1962) found that isolated adults of P. hegeneri stopped growing after 20 days in a chick's eye and never produced fertile eggs. Working with a similar Received for publication 20 May 1971. * This investigation was supported by the United States-Japan Cooperative Medical Sciences Program administered by the NIAID; Grant AI 09330. fluke, Howell and Bearup (1967) noted that single-worm infections of Philophthalmus burrili were infertile and contained no recognizable seminal receptacle. A similar situation in which species of a genus differ as to the viability of isolated adults also seems to occur in the genus Paragonimus. Sogandares-Bemal (1966) found that monometacercarial infections of cats with Paragonimus kellicotti never developed beyond the wandering preadult stage. However, Fan and Chiang (1970) found single infections of Paragonimus westermani in kittens and puppies developed into mature adults producing eggs capable of hatching. Varied results have been obtained with isolated adults of other digenetic trematodes. Bacha (1966) found that eggs produced by a second generation of isolated adults of Zygocotyle lunata in rats hatched less readily than those from multiple infections. Sogandares-Bernal (1965) found a higher percentage of paired adults of Microphallus opacus, which were excysted and maintained in vitro, produced eggs than those maintained in isolation. Viability of these eggs was not determined. Beaver (1937) and Lie (1965) observed normal miracidial development and hatching in single infections with species of Echinostoma. In this study successive life cycles of P. megalurus were investigated because this species grows and develops normally in isolated situations, and has proved viable for at least one self-fertilizing generation. A major drawback was the difficulty of raising the snail intermediate host, Pleurocera acuta. This was partially

A new second intermediat host of genus Paragonimus.

1. Metacercariae were found from 6 samples among 4,382 Parlemon nipponensis which were caught at Podu, Kohung, Korea. 2. The metacercaria was inclined as a larval stage of Paragonimus westermani by following reason; i)Semisulcospira libertina was the only one species which lives in Podu area. ii)No other metacercaria except Paragonimus westermani were found from the craw or cray fish which were caught in the endemic aera. iii)Metacercariae, ovary, testes and cuticular spines resmbled the characteristics of Paragonimus westermani, which have been described by previous workers.

The Distribution of Paragonimus

A brief resume of the results of the study on the distribution of Paragonimus was published in the American Journal of Hygiene by one of us (Ameel, I934). However, it has been deemed advisable to place the complete data at the disposal of those who may be interested in furthering the knowledge of the distribution of this parasite in North America. Though material was secured from many parts of the United States and from several regions in Canada by means of expeditions and purchase, the actual area covered is relatively small. The genus Paragonimus has almost world-wide distribution and for the sake of completeness, the published records are briefly summarized here. Authentic reports for Asia are as follows: Formosa (Manson, I88I; Kubo, 1912), Japan (Baelz, I880), Korea (Kobayashi, I918), New Guinea (Cilento and Backhouse, 1927), Indo-China (Salomon and Neveu, 19I7), Philippine Islands (Musgrave, I907), India (Cobbold, 1859; Vevers, I923), Malay States (Vevers, I923), Sumatra (Weber, 1891), Java (Noto-Soediro, 1930), China (Maxwell, 1931; Wu, 1935 and I936). Faust (1929) also lists Siam. Onorato (1920) published what appears to be an authentic record of a human case of paragonimiasis from Africa. The patient, a resident of Tripoli, had never been further from home than Tunisia. The symptoms described were similar to those of paragonimiasis and the measurements of eggs recovered in the sputum were within the range of Paragonimus. After the onset of the disease, the patient suffered from epileptiform attacks which Onorato believed might be due to the presence of worms in the brain. About 7 years after he first began to suffer from the disease, the patient died, but, unfortunately, no autopsy was performed. Onorato and also Salomon and Neveu (1917) casually mentioned a case of paragonimiasis in an Arab reported by R. Wurtz but no reference was given. A copy of the report which was included in an unpublished thesis by M. Crespin presented in I908 and deposited in the University of Paris was secured through the kindness of Prof. E. Brumpt. The patient, a native of Cayor, had spent io years in Senegal and Dahomey in the military service. In addition, he had resided a year on the ivory coast and 5 years in Madagascar. Attacks of hemoptysis began 4 months

The Lung Flukes of the Genus Paragonimus: A Demonstration

The Lung Flukes of the Genus Paragonimus: A Demonstration

Observations on the genus Paragonimus Braun with a re-description of P. compactus (Cobblold, 1859) 1899

The earliest record of a mammalian lung fluke was made by Diesing in 1850, who described Distomum rude from the lungs of Lutra brasiliense, from Brazil. This species was transferred to the genus Paragonimus by Stiles and Hassall in 1900.