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Cephalopod molluscs have attracted little attention as potential hosts for digenetic trematodes. Though none appears to serve as a first intermediate host, many do act as second intermediate, paratenic, or final hosts. Hence, they probably play a more important role in the life history and dissemination of Digenea in the marine environment than is generally recognized.

1.Neodiplostomum intermediumPearson is recorded from four new hosts; as an adult from the water rat,Hydromys chrysogasterGeoffroy, and as a metacercaria (diplostomulum), from tadpole and adult of an undescribed tree frog,Hylasp., tadpole of (Hyla latopalmata(Günther)Mixophyes fasciolatusGünther and frog of an unidentified leptodactylid.2. The life cycle ofNeodiplostomum intermediumwas followed experimentally; the hosts were:Pettancylus assimilis(Petterd), a fresh-water limpet, as first intermediate host; tadpole ofHyla pearsoniCopland as second intermediate host;Hyla caerulea(Shaw) a tree frog, andHemisphaerodon gerrardiPeters, the pinktongued skink, as paratenic hosts; andRattus assimilis(Gould) and laboratory rats as definitive hosts.3. Descriptions are given of the morphology of the miracidium, mother sporocyst, daughter sporocyst, cercaria, and diplostomulum, with special reference to the structure of the miracidium and of the cercarial tail.4. Observations are given on the embryology of the miracidium, hatching of the egg, transformation of the miracidium into the mother sporocyst with special reference to the germinal cells, the route and manner of escape of cercariae from the snail host, the development of the diplostomulum with special reference to the reserve excretory system, and the movements of diplostomula during metamorphosis of the tadpole host.5. The haploid chromosome number is ten, as determined from squashes of testes. One paratype and a series of experimental adults have been compared with and found different fromNeodiplostomum(Fibricola)sarcophilusn.comb. The orthography and formal proposing of the names of the species ofFibricolatransferred toNeodiplostomumby Pearson (1959b) are corrected.The writer wishes to thank Dr M. J. Mackerras, Queensland Institute for Medical Research, for generously supplying water rats; Professor J. F. A. Sprent, University of Queensland Veterinary School, for his criticism of the manuscript; Mr K. Webber and his sons for their assistance in catching rats and for permission to collect snails, frogs and tadpoles from their streams; and Mr R. J. Ballantyne for technical assistance. This study was supported by a grant from the Rural Credits Fund of the Commonwealth Bank of Australia.

0·15% ofOesophagostomumlarvae fed to laboratory rats became encapsulated in the intestinal mucosa. The juvenile nematodes were able to continue their development when the infected rat tissue was eaten by pigs.

Of a total of 240 rats examined on the island of Rarotonga, 85.0% showed lungworm infection. No lungworms were found among 61 rats trapped in and around Auckland, New Zealand, and none among 95 rats trapped in the vicinity of Apia, Western Samoa. Of land mollusks examined on the island of Rarotonga, the following species were found infected with lungworm larvae: (slugs) Deroceras laeve and Vaginalus plebeius, and (snails) Bradybaena similaris and Subulina octona. In addition, a few infective larvae were found among land planarians and freshwater prawns, both of which serve as paratenic hosts. The finding of the rat lungworm on the island of Rarotonga offers an additional example in the Pacific of the occurrence of this parasite in an area where human eosinophilic meningitis occurs.

Observations are reported on the life history of Amplicaecum robertsi, in relation to the mode of infection as it occurs under natural conditions. Some of the natural intermediate hosts are listed, as compiled from observations on natural infection with third-stage larvae in Queensland mammals. Various natural intermediate hosts were experimentally infected by means of eggs, and observations on the growth and development of the larvae are described.It was found that the second-stage larvae have a wide range of hosts, including earthworms, snails, fish, tadpoles, reptiles, birds, and mammals. Development to the third-stage was only observed to occur in birds and mammals. Third-stage larvae exhibited a wide variation in the degree of growth attained in different animals. In birds, growth was slight, not extending beyond 3–4 mm.; in mammals, growth varied considerably in different species; it was greater in the indigenous species, reaching 70–80 mm. No development beyond the third-stage occurred, except in reptiles.Second-stage larvae in the tissues of invertebrates and lower vertebrates could be transferred by feeding to reptiles, birds and mammals. Development proceeded in these hosts to the same extent as occurred following egg infection.Third-stage larvae could be transferred to certain snakes and lizards by feeding liver of infected rodents, but third-stage larvae over 3 mm. could not be transferred to mammals. Third-stage larvae were found to be uninfective at all stages of growth for birds.The third moult occurred in the carpet snake when fed with third-stage larvae in the liver of Trichosurus caninus, Rattus assimilis and Melomys cervinipes infected 1 month previously. This was in contrast to previous findings with laboratory rodents, in which maturation of the third-stage larva took considerably longer.Besides the carpet snake, the third and fourth moult was observed to occur in the goanna (Varanus spp.), the blue-tongued lizard (Tiliqua scincoides) and the bearded dragon (Amphibolurus barbatus). No growth in length was observed and no eggs were evident. As far as is known, none of these lizards is a definitive host of A. robertsi.The results are discussed in relation to the food chain involved in the natural habitat of the carpet snake. The snake is depicted as the apex of a food pyramid, whose base comprises a variety of animals ranging from earthworms to herbivorous mammals. It is concluded that A. robertsi has adapted its life history in such a way as to enable the parasite to ascend the pyramid by transference through a series of predatory episodes, which culminate in the infection of the natural prey of the snake.The life history is thus regarded, not as a life cycle, but as a life pyramid; development proceeds according to a pattern of diminishing host-specificity. Host-specificity is wide at the base of the pyramid, so that second-stage larvae occur in a wide variety of paratenic hosts. Host specificity narrows at the second moult which may occur in birds and mammals. It narrows still further in the third stage, because this larva, though it will survive in reptiles, birds and mammals, will not grow to a length at which it is capable of further development in the snake, except in certain mammals. At the third moult, host specificity shifts to certain reptiles, but becomes eventually restrictive to the carpet snake, because this host alone appears to provide a suitable environment for maturation of the eggs.This work was financed by a research grant from the University of Queensland. The writer's sincere thanks are due to Miss Ann Pritchard and Mr J. Ballantyne for their valuable assistance.

1. Stages in the life-cycle of Azygia acuminata are described and figured. Cystocercous cercariae develop from rediae in the snail, Campeloma decisum. The cercaria is morphologically distinct from other described cystocercous cercariae. Rediae are similar to the same stage described for other members of the genus, but are unique since they develop in the uterus of female Campeloma decisum.2. The excretory system of the cercaria is complex, showing a formula of 2 (11 x 32) or 704 flame cells for the distome portion and 2 (5 x 32) or 320 flame cells in the tail. The excretory formula of the cercariae is thus 2 (16 x 32) or 1,024 flame cells.3. Attempts to experimentally infect small snails, taken from the uterus of a Campeloma decisum, by feeding them eggs of A. acuminata were not successful.4. Various small fishes were utilized as paratenic hosts by the young distomes. Infections in sticklebacks, Eucalia inconstans, and small eels, Anguilla rostrata, resulted in more active and vigorous worms than did infe...

Publisher Summary This chapter discusses experimental results on final host specificity of two species of Neodiplostomum . In the Berlin area, Buteo buteo in naturally infested with Neodiplostomum (N.) attenuatum but Circus aeruginosus and Accipiter gentilis are naturally infested with N. (N.) spathoides Dubois. The life cycle of N. spathoides was completely traced by experiments. The first intermediate host is Planorbis planorhis. Primary hosts of metacercariae are tadpoles; paratenic hosts are Anura, reptiles, birds, and mammals. The life cycle of N. attenuatum was partially traced: up to now, only the development of metacercariae to adults, and the trasmission of metacercariae to further paratenic hosts have been proved experimentally.

Studies were carried out in mice and a monkey (paratenic hosts) and pathological lesions in mice have been described in liver, lung and brain withToxocaralarvae moving actively in the tissues causing damage (haemorrhages and necrosis) with encystment. In both mice and monkey there is essentially an eosinophilic response with lymphocytes and neutrophils also showing rise in the peripheral blood a few days after infection. In mice lymphocytes are the predominant tissue inflammatory cell.

The persistence and precise location of Ancylostoma caninum larvae in tissues of vertebrate paratenic hosts and the nature of host responses were studied in mouse, cat, and monkey. Mice were infected percutaneously and examined at various intervals up to 260 days after exposure. Long-persisting larvae were found only in the muscles. Histologic sections revealed that within 4 hr after exposure some larvae had migrated through the skin and had entered individual fibers of the underlying muscles. After the 1st day nearly all larvae found in muscles were within fibers. Granuloma formation and encapsulation were not observed, suggesting that inside the fibers the larvae produced no direct inflammatory reaction. Only diffuse infiltration of inflammatory cells was observed in muscles and this appeared to be in response to destruction of muscle fibers. Larvae were similarly located in muscles of a cat and a rhesus monkey examined 16 and 17 days, respectively, after cutaneous exposure. The histologic changes observed in muscle fibers invaded by A. caninum larvae are similar to those observed in early Trichinella spiralis infections. The larvae of A. canninum lying coiled within the muscle fibers also bear superficial resemblance to the larvae of T. spiralis. A. caninum larvae were also recovered by tissue digestion from muscles of naturally infected dogs, which suggests that larvae reside in this location in the bitch prior to transfer to the neonate via the milk.

Following the identification of the larval stage of Toxocara canis in the liver of a child in New Orleans (Beaver et al, 1952), numerous confirmatory case reports have shown that infection with larvae of this ascarid of dogs is an important cause of disease in children. Inasmuch as infection is acquired through ingesting soil previously contaminated by infected dogs, children at the dirt-eating stage of development are most frequently and heavily infected. In most of the temperate and warmer regions of the world T. canis infection in dogs is extremely common. It occurs most frequently in young dogs and is more common in the male than in the female adult (Ehrenford, 1957). It has been found prevalent among well-cared-for as well as stray dogs in New Orleans (Vaughn and Jordan, 1960). Infective eggs of T. canis have been found abundantly in door-yard soil (Headlee, 1936; Beaver, 1952). These conditions provide opportunities for young children to acquire various degrees of superinfection. Acquired resistance to nematode infection has been frequently demonstrated. As far as ascarids are concerned, the general conclusion has been that previous infection induces resistance which affects primarily the migration and survival of larvae in the tissues. Studies on the larvae of the pig ascaris have shown that fewer of them can be recovered from the liver and lungs of mice previously infected than from those given equivalent single inoculations (Wagner, 1933) ; single or multiple sublethal inoculations render guinea pigs resistant to otherwise lethal doses of infective eggs (Kerr, 1938); and in mice immunized by previous infections, the larvae are retarded in their growth and migration, remaining for longer periods in the liver before migrating to the lungs (Sprent and Chen, 1949). Comparative studies on the larval migration patterns of various ascarids have shown that Toxocara canis differs fundamentally from Ascaris lumbricoides in that its larvae are adapted to paratenic transfer, i.e., passage through a succession of intermediate cannibal or predator hosts after having reached infectivity for the final host (Sprent, 1952); therefore, the larvae of these 2 species may be affected differently by superinfection.

Studies were made to determine whether chickens and pigeons could serve as paratenic hosts of Toxocara canis. It was found that both types of hosts harbored living infective-stage larvae for at least 142 days after inoculation. At this time, of the number of larvae inoculated, it was possible to recover approximately 30% from chickens and 18% from pigeons. Human infections with larvae of Toxocara canis are known to occur throughout the United States and in Mexico, Europe, Australia, the Philippines, and South Africa (Beaver, 1962). In the majority of cases, the infected individual is a 1to 3-year-old child who acquired the infection by ingesting infective eggs in contaminated soil (Beaver et al., 1952). In some cases, however, especially those in which the eye is invaded, the infected individual is an older child or young adult (Beaver, 1962). Although in such instances the invading larvae possibly have persisted elsewhere in the body since early childhood, it is also possible that they were acquired by eating raw or poorly cooked parts of infected meat animals. T. canis larvae persist for months or years in a wide range of mammalian laboratory hosts (Beaver, 1962), and it is presumed that they are transferred from animal to animal through paratenic hosts in nature (Sprent, 1954). It has been suspected that the eosinophilia observed in persons eating raw liver for the control of pernicious anemia was caused by infection with nematode larvae, possibly Toxocara, harbored in the liver (Beaver, 1956). Done et al. (1960) found that in the experimentally infected pig, many infective-stage Received for publication 21 August 1963. * Supported by grants EF-, EPD-14573, and AI04919 from the National Institutes of Health, U. S. Public Health Service. t Present address: Department of Veterinary Parasitology, Agricultural and Mechanical College of Texas, College Station. larvae of T. canis could be recovered from the liver, brain, lungs, and muscles more than 2 months after inoculation. In a similar study on T. canis in sheep and lambs, Schaeffler (1960) recovered the larvae from liver, muscle, and other tissues 3 months after inoculation. Studies on poultry have been brief and inconclusive. Sprent (1956) recovered six larvae of T. cati from the carcass of an experimentally infected chick at 10 days but none could be found in others at 15, 20, or 25 days. Beaver (1956) found that larvae of T. canis persisted for at least 3 months in the liver of chickens and pigeons. The present study was undertaken to get further information on the persistence and distribution of T. canis larvae in the tissues of chickens and pigeons. MATERIALS AND METHODS T. canis eggs obtained by sedimentation of feces from naturally infected dogs were incubated in 1% formalin at room temperature for 4 to 6 weeks before use. Estimated numbers of infective eggs were injected by pipette directly into the crop of young chickens and pigeons. Recovery of larvae was accomplished by two procedures: by one, the tissues were ground in saline with a Waring blendor and digested in 1% pepsin (pH 1.5) in saline (0.83%) at 37 C for 3 to 4 hr; suitable aliquots were then washed and concentrated by centrifugation in saline and the sediment was examined microscopically for larvae. By the other, tissues were chopped and finely minced with scissors and scalpel, placed in a Baermann apparatus in which the suspending medium was pepsin digest fluid, allowed to stand at 37 C for 3 to 4 hr, after which the sediment was collected and examined in the usual manner. This method, though

Twenty-three of 43 frogs (Hyla aurea) from market gardens in Noumea, New Caledonia were found to harbor infective-stage larvae of Angiostrongylus cantonenisis in their tissues. The larvae were encapsulated in the wall of the alimentary tract, the mesentery, liver, and somatic musculature; they were infective for rats. Sea snakes (Laticauda colubrina) were experimentally infected with third-stage A. cantonensis larvae and in these hosts the larvae survived and remained infective for rats for at least 1 month. The use of paratenic hosts by A. cantonensis and other metastrongyles is discussed. Very little is known as to the extent and significance of the role played by paratenic hosts in the transmission of metastrongylid infections in nature. The Hobmaiers (1935) were the first to note the use of such hosts among the metastrongyles when they demonstrated that amphibians, reptiles, birds, and mammals could serve as experimental hosts for larvae of the cat lungworm, Aelurostrongylus abstrusus. Subsequently, it has been shown that other metastrongyle larvae will enter the tissues of various vertebrates that possibly may serve as paratenic hosts in nature (Gerichter, 1949; Seneviratna, 1959; Anderson, 1962). The discovery that Angiostrongylus cantonensis, a parasite of rats, may infect man and cause eosinophilic meningitis has served to focus attention upon the biology of this nematode in particular, and upon metastrongyles in general. Thus far, infectivestage A. cantonensis larvae have been reported in nature from such paratenic hosts as planarians (Alicata, 1962), shrimp (Alicata and Brown, 1962; Rosen et al., 1967) and land crabs (Alicata, 1964b). In addition to these natural infections there have been successful experimental infections of shrimp (Wallace and Rosen, 1966), fish (Wallace and Rosen, 1967) and pigs and calves (Alicata, 1964a). Observations reported in this paper further extend the paratenic host range for A. cantonensis to amphibians and reptiles. Received for publication 16 February 1968. * Present address: Division of Infectious and Tropical Diseases, School of Public Health, UCLA, Los Angeles, California 90024. RESULTS 1. Natural infection in frogs In the course of surveying market gardens in Noumea, New Caledonia for mollusks and other invertebrates harboring nematode larvae frogs infected with A. cantonensis were found on several occasions. Hyla aurea (Less.) was the frog collected. This species was originally introduced from Australia and is the only known species of frog to occur in New Caledonia. It is relatively small, 5 to 7 cm long, and may weigh from 5 to 27 g. Examination of the stomach contents of these amphibians revealed that while insects probably comprise the bulk of their diet the remnants of mollusk shells as well as the bodies of smaller frogs were not uncommon findings. From mid-1966 to April 1967 a total of 43 frogs (29 females, 14 males) were examined for infection with A. cantonensis. In each instance, except as subsequently noted, the entire frog was examined for the presence of larvae by digestion in 0.5% pepsin in 0.7% HC1 and by pressing the tissues between thick glass slides. The frog was killed, skinned and the mesentery was examined for the presence of encapsulated larvae. Selected organs and tissues were then removed and divided into four groups for digestion: (1) alimentary tract and mesentery, (2) liver, (3) rear legs, and (4) rest of the carcass. Following digestion for 2 to 3 hr the digests were allowed to sediment in a modified Baermann funnel for an additional 2 to 3 hr prior to examination for larvae. Tissues that were examined for larvae

The author rejects the generally accepted view of the terrestrial origin of the Ascaridoidea from the Rhabditoidea by way of the Oxyuroidea, in which the direct life history is regarded as the primitive pattern of transmission. He advocates instead a marine origin and argues that the lips, esophagus, and excretory system of the ascaridoids can be equally well derived from such free-living marine forms as Enoplus, and he regards terrestrial forms as a secondary radiation. According to this view, forms having three hosts (an invertebrate paratenic host, with the second-stage larva in tissues; a small predatory vertebrate with the third-stage larva in its tissues, and a dominant predatory vertebrate harboring the fourth-stage larva and the adult) are the most primitive, and those having two and one are progressively more adaptive. The direct life history of such one-host ascaridoids as those of man, horse, and pig represent adaptations to the absence or loss of the predatory habit on the part of the host. These speculations, as well as the history of the classification of the group, are treated in detail. The starting point of this review is Chitwood's statement (Chitwood, 1950, p. 195), regarding his views on the origin of the Ascaridoidea. In essence this statement proposed that: (a) they arose from a primarily terrestrial stem, probably from the Rhabditoidea through the Oxyuroidea, (b) the marine forms arose as a secondary radiation through fish traveling up rivers from the sea, (c) that the direct (monoxenous) life-history pattern is more primitive than the indirect (heteroxenous) pattern which arose secondarily. It is probably true to say that these views were to some extent influenced by the fact that most of the previous investigations relating to the life history of the ascaridoid nematodes had been directed to the large roundworms of man and domestic animals. These findings had made such an impact on contemporary parasitologists that the direct life history was regarded as an established pattern for the whole group. This may partly explain why the indirect life-history pattern, involving one or more intermediate hosts, as demonstrated for * Dr. Sprent prepared this lecture on the occasion of his receipt of the Henry Baldwin Ward Medal. Because of its length, the address was presented as the first paper on the Symposium: The Future of Nematology, Thursday morning, 14 June 1962, at 8:30 Am. A briefer response, which will be printed later in the Journal, was made at the time of the award. marine ascaridoids by Wiilker (1929), was regarded as a secondary development. In the past 12 years there has been at least a partial change of viewpoint regarding the evolution of the ascaridoids. It is intended in this paper to outline the developments which have influenced this change. Broadly speaking, three main types of investigation have contributed: (1) elucidation of life-history patterns in individual species, (2) morphological observations on the group as a whole, and (3) discussions on the phylogenetic significance of certain morphological features and life-history patterns. In the first category we must acknowledge the contribution of Tiner (1949) who first demonstrated the role of intermediate hosts in the life history of ascaridoids of terrestrial mammals. This discovery focused attention on a number of isolated observations, which together indicated that the indirect life history is much more widespread among the group than was previously realized. Accumulation of this evidence was considerably facilitated by the publication of "The Ascaridata of Animals and Man" by Mozgovoy (1953). This two-volume compilation in Russian, besides being the first comprehensive account of the ascaridoids, included a number of observations on life histories which had been undertaken in the Soviet Union and were not hitherto readily accessible.

The experimental life cycle of Alaria (A.) marcianae (La Rue, 1917) Walton, 1949, involves planorbid snails, Helisoma trivolvis and H. campanulatum, as first intermediate hosts; tadpoles of the leopard frog, Rana pipiens, as second intermediate hosts; mice, rats, and chicks as paratenic hosts; and the domestic cat as definitive host. The life cycle is similar to known cycles in the subgenus Alaria, where avian and mammalian intermediate hosts of the mesocercariae serve as paratenic hosts; but it differs from the only known cycle in the subgenus Paralaria, where the mesocercariae develop into metacercariae in avian and mammalian intermediate hosts. This difference in mesocercarial behavior represents a distinct biological difference between members of the two subgenera and is an additional subgeneric character. Alaria (A.) minnesotae Chandler, 1954, is a synonym of A. (A.) marcianae (new synonymy). Six Alaria spp. belonging to the subgenus Alaria Schrank, 1788, have been described from indigenous North American carnivores: A. americana Hall and Wigdor, 1918; A. arisaemoides Augustine and Uribe, 1927; A. oregonensis La Rue and Barone, 1927; A. canis La Rue and Fallis, 1934; A. minnesotae Chandler, 1954; and A. marcianae (La Rue, 1917) Walton, 1949. Of the first five species, Dubois (1963) considered only A. americana and A. arisaemoides valid. Alaria marcianae, the subject of this study, was not included in his revision. From 1960 to 1964, the writer collected adults of an Alaria (A.) sp. from several different carnivore hosts in Minnesota. Additional specimens collected during 1937 and 1938 were available for study. Morphological studies were made of these worms, and the complete life history was studied in experimental hosts beginning with eggs. These parasites were then identified as A. marcianae.

Previous records of acanthocephalans in man are reviewed. Acanthocephalus bufonis (Shipley, 1903) Southwell et Macfie, 1925, is reported from man for the first time, recovered on autopsy of an Indonesian in Djakarta. Corynosoma strumosum (Rudolphi, 1802) Liihe, 1904, is reported from an Eskimo in Alaska, the first record of this parasite from man. Infections of man with acanthocephalan parasites are rare. Many species in this phylum are known to have low host specificity (Golvan, 1957) but for ecological reasons are not likely to be ingested by humans. The intermediate hosts of all species whose life cycles are known are either crustaceans, myriopods, or insects. However, several species are known to utilize fish, amphibians, or reptiles as paratenic hosts, thereby increasing the chances of accidental parasitism in persons eating such animals raw or undercooked. Lambl (1859) gave the first report of a thorny-headed worm in man when he recovered a Macracanthorhynchus hirudinaceus from a child in Prague. Lindemann (1865) stated the infection was common in Russia, where Schneider (1871) found that scarabaeid beetle grubs, the intermediate host, were commonly eaten raw. Gonzaga (1921) recovered eggs of M. hirudinaceus in two of 1,236 human stools in Brazil. A more recent case of proved chronicity was published by Pradatsundarasar and Pechranond (1965) in Thailand. Moniliformis moniliformis, a parasite of rats and cockroaches, has been reported from man in Italy, Sudan, and British Honduras (Faust and Russell, 1957), and Beck (1959) reported it from a patient in Florida. Grassi and Calandruccio (1888) reported on the symptoms displayed by the second author after voluntarily infecting himself with M. moniliformis. Kuntz (1960) reported acanthocephalan eggs, possibly those of this species, from stools of two children in Dacca, East Pakistan. Moore, Fry, and Englert (1969) made the interesting discovery of acanthocephalan eggs in human coprolites obtained in archeological excavations in Danger Cave, Utah. RadiocarReceived for publication 20 October 1970. bon dating placed the samples at 1869 BC ? 160 years, and AD 20 ? 240 years. The authors suggested that the parasite may have been Moniliformis clarki, which is common in the area. The only acanthocephalan outside the class Archiacanthocephala reported from man is A anthocephalus rauschi, recovered by Dr. Rob rt Rausch from the peritoneum of an Eskimo in Alaska, and described by Golvan (1969). The normal definitive host is probably a fish. The present paper reports the occurrence of two more palaeacanthocephalans in humans. Acanthocephalus bufonis (Shipley, 1903) Southwell et Macfie, 1925 (Syn. Acanthocephalus sinensis Van Cleave, 1937) In 1954, during a routine autopsy by Dr. Lie Kian Joe at the Medical School in Djakarta, Indonesia, four male acanthocephalans were recovered from the small intestine of an Indonesian man by screening the contents of the intestine with a metal sieve routinely used to collect hookworms. No wild animals were dissected in the autopsy room, and there was no chance that the specimens came from an outside source and had become mixed with material from human autopsies. Due to a lack of library facilities in Djakarta it was impossible to identify the worms to species; they were reported as Acanthocephalus sp. by Lie Kian Joe and Tan Kok Siang (1959). One specimen was lost prior to the present study. I now know them to be adult males of Acanthocephalus bufonis, a very common parasite of amphibians in Asia (Yuen and Fernando, 1967). Its life cycle is unknown but probably involves a terrestrial isopod crustacean as intermediate host. I can speculate that the man became infected in one of three ways: (1) by ingesting an infected arthropod; (2) by eating an am

Various helmlinth parasites of dogs and cats are known to develop or live in man (Echinococcus spp., Toxocara spp., Dipylidium caninurm, Ancylostonma braziliense, A. caninum, Uncinaria stenocephala, and possibly Tr'ichuris vulpis) and some are capable of causing very serious pathological conditions. Of the human infections acquired through close association with dogs and cats in the United States, England, Puerto Rico, and undoubtedly other areas, perhaps next to Echinococcus the most significant, widespread, and damaging is that known as visceral larva migrans caused by the roundworn of dogs, Toxocara canis. The roundworm of the cat, T. cati, may also be of some importance in causing this disease in man. Visceral larva migrans is primarily a disease of toddleage children who ingest soil polluted with the eggs of Toxocara. Since Toxocara does not mature in man, a paratenic host, no eggs are produced for easy diagnosis. The second stage larvae may migrate through the organ systems (liver, lungs, brain, kidneys, eyes) for several weeks and remain alive encapsulated for many months, sometimes causing petit mal attacks, blindness, and even death (Beaver, 1956). Dent (1960) and Ashton (1960) indicate that eye infections have been found following mild Toxocara infections in which symptoms were not outstanding. A usual clinical finding, even in the absence of other symptoms, is eosinophilia frequently exceeding 50 percent persisting at a high level usually for a year or more, but which may be absent in eye infections.

Larvae of the dog hookworm, Ancylostoma caninum, can invade and remain infective for more than 1 year in the tissues of various rodents (Nichols, 1956). As these larvae can infect cats and dogs by mouth as well as by skin, it is possible that infected rodents may serve as natural paratenic hosts. The purpose of the present study was to determine whether insects may serve as paratenic hosts in the same manner. Cockroaches were chosen for investigation because they are commonly eaten by cats, they are likely to be in contact with hookworm larvae under natural conditions, and they have been suggested as natural paratenic hosts for other nematode parasites of cats (Sprent, 1956).