Kinds Of Hosts Research Articles

The classification and nomenclature of viruses summary of results of meetings of the International Committee on Taxonomy of Viruses in Madrid, September 1975

The International Committee on the Taxonomy of Viruses (ICTV), which is a committee of the Section on Virology of the International Association of Microbiological Societies (IAMS), completed a round of meetings during the Third International Congress for Virology that was held in Madrid from September 10-17, 1975. Since ICTV only meets during these conferences, which are held every four years, the meetings are important occasions for reviewing the classification and nomenclature of viruses. Decisions on new names, which encapsulate the recognition of natural “groups” of viruses, evolve slowly. Official approval for new names depends upon a series of sequential steps; recommendations by one or more of the subcommittees of the Executive Committee of ICTV (subcommittees on Bacterial, Invertebrate, Plant, and Vertebrate Viruses, respectively, and for some of the larger viral groups which span several kinds of hosts, the Coordination Subcommittee), which are considered by the Executive Committee of ICTV, and may finally be submitted for approval by ICTV itself. Only after this

Host Recognition by the Gypsy Moth1 Larval Parasitoid, Apanteles melanoscelus2

Host recognition in Apanteles melanoscelus Ratzeburg was studied by presenting females with 2 kinds of hosts simultaneously and recording their activities on each host type. An important stimulus which elicited examination and probing behavior by the parasitoid was hairyness of the host. Also important was a chemical(s) in the exuviae of young gypsy moth larvae, Porthetria dispar (L.), which could be removed with various solvents. The nature of the chemical(s), however, was not determined.

Infection with herpes-simplex viruses 1 and 2. 3.

The Infected HostThe effects of HSV on the host can best be appreciated by analysis of both the epidemiologic and the clinicopathological aspects of the infection. In this way, the modes of spread and acquisition of the virus and its distribution in various body sites can be examined in relation to the clinical responses elicited in various kinds of hosts (newborns, immunologically compromised persons, etc.).Epidemiologic PatternsStudies in the "second" period of HSV research (around 1920 to about 1960) brought into relief three important points: that patients experiencing either initial or recurrent HSV infections often fail to have . . .

Studies on the mosquitoes of North Arcot district, Madras State, India. 2. Biting cycles and behavior on human and bovine baits at two villages.

The relative preferences of various mosquito species of southern India for man, bullock or buffalo were determined in the open. Culex pipiens fatigans showed a definite preference for man, C. bitaeniorhynchus was taken in almost equal numbers on the 3 kinds of hosts, and all other species, including those of the C. vishnui group, preferred the animal bait. Several species, including the C. vishnui group, preferred bullock to buffalo, some species showed no preferences, and 2 showed a slight preference for the buffalo. The 7 most common species were all more active before midnight than after. Anopheles hyrcanus was most active just after dark, An. pallidus and C. bitaeniorhynchus showed 2 peaks of activity before midnight and the C. vishnui group and An. subpictus showed increasing activity to a maximum between 2200 and 2400 hr, when numbers began to decline steadily until activity ceased at dawn. An. subpictus was taken in approximately equal numbers on human bait inside a hut, on the porch, and in the open air. All other mosquito species were taken in largest numbers in the open and in smallest numbers in the hut. The C. vishnui group entered the hut to bite in fair numbers. C. pipiens fatigans was uncommon in the village at which these observations were made; its behavior could not be studied. The proportions of the different species taken biting a bullock in the open were similar to the proportions of the same species taken in a bullock-baited stable trap in the same village. The C. vishnui group predominated in both types of collection.

Some Observations on the Development ofSpirocerca lupiin its Intermediate and Definitive Hosts

1. Infective larvae ofS. lupiwere collected in Madras from scarabaeid beetles, (the usual intermediate host), from garden lizards and shrews.2. The structure and relative sizes of the larvae in the 3 kinds of hosts are compared.3. Infective larvae were given orally to 30 dogs which were autopsied at intervals and the developing worms were recovered. Their growth was measured and some observations were made on their development during the prepatent period which was found to be 121 and 124 days.

Endocrinological studies on spermatogenesis in the silkworm, Bombyx mori L.

When embryonic testes 1 or 2 days before hatching were transplanted into 5 kinds of hosts (5th instar larvae, “fresh” pupae just after pupation, isolated pupal abdomens and 3-day-old pupae with and without their original corpora allata), the testes transplanted into 5th instar larvae grew most conspicuously and spermiogenesis began in many cysts. A few spermatidal cysts were observed in the testes transplanted into fresh pupae. No signs of maturation were observed in the testes transplanted into other hosts. It is concluded that prothoracic gland hormone might be responsible for the precocious maturation of young testes. On the other hand, the initiation of spermiogenesis was delayed, in comparing with controls, in the 3rd instar larval testes as follows: the testes transplanted into 3-day-old pupae, the testes transplanted into isolated pupal abdomens together with adult corpora allata and the testis into which corpus allatum of a 3rd instar larva was inserted. It is concluded that corpora allata hormone exerts an inhibitory effect on spermatogenesis.

SOME ASPECTS OF HOST SELECTION BY MANSONIA PERTURBANS (WALK.) (DIPTERA:CULICIDAE)

Blood meals of female Mansonia perturbons (Walk.) collected from farms and wooded areas in southeastern Ontario were identified by the serological precipitin test. The mosquitoes had fed on birds, farm animals, humans, rodents, deer, and raccoons. Preliminary observations on host preferences indicated that birds may constitute a more important group of hosts for M. perturbans than mammals. In experimental trials, attraction of M. perturbans to mammals appeared to be related to the surface area of the host. A rather high proportion of specimens collected in nature contained the blood of more than one kind of host and, in laboratory tests, M. perturbans showed a greater tendency towards multiple feeding than was shown by three species of Aedes mosquitoes.

Einfluss des Wirtsalters auf die Entwicklungsleistung von Sagittalhälften männlicher Genitalscheiben von Drosophila melanogaster

Earlier investigations suggested that the extent of regulation in fragmented genital disks depends upon the age of the host larvae rather than the age of the disks themselves. Thus, a fragmented disk will regulate completely if transplanted into a young host, but partially only if transplanted to a somewhat older larva. The present experiments deal with the question whether or not complete regulation may take place also in an old host, provided a long enough incubation of the fragment before the onset of metamorphosis, or whether the hormonal situation of an old host prevents full regulation. Medially fragmented male genital disks of larvae ready to pupate have been repeatedly transferred to either old larvae or adult flies. Thereby, the growth of the fragments could be followed directly. The regulative capacity of these fragments was tested by removing them from the hosts after various intervals and subsequent transplantation into a final larval host, where they were allowed to finish metamorphosis. The results indicate that full regulation may occur in any kind of host, irrespective of whether it is a younger or older larva or an adult, provided a long enough lapse of time between the fragmentation and the onset of metamorphosis. No supernumerary organs have been formed, however, in fragments cultured as long as 28 days in adult flies. Instead, organ-specific defects are observed in the genitalia that were formed from these fragments. The results are discussed with regard to the humoral control of growth in imaginal disks.

BLOOD-MEAL SOURCES AND NOTES ON HOST PREFERENCES OF SOME AEDES MOSQUITOES (DIPTERA:CULICIDAE)

Blood meals of engorged female Aedes mosquitoes collected from animal dwellings, light traps, and hand catches were identified by serological precipitin tests. The mosquitoes had fed on farm animals, humans, rodents, raccoons, deer, and probably foxes. Very few of the specimens had fed on birds and few contained the blood of more than one kind of host. Preliminary studies in a screened enclosure in a one-room barn that contained various combinations of domestic animals and humans indicated that a preference shown by mosquitoes for a mammalian host is related to the surface area of the host.

Experimental studies in insect parasitism. X. The reactions of some endopterygote insects to an alien parasite

Eggs of an ichneumon fly, Nemeritis canescens , have been injected into endopterygote insects to which this parasite was alien. In larvae, pupae and adults of Tenebrio molitor (Coleoptera) almost all the eggs hatched; and within 24 h haemocytes enveloped the parasite larvae and melanin was deposited over their mouth and anus. The pattern of these reactions was the same in all cases and at all stages. When individuals of Tenebrio were given repeated injections at weekly intervals, they reacted to the last parasite exactly as to a first. Female individuals that had been repeatedly injected were allowed to develop and to lay eggs; when larvae reared from those eggs were injected they made the same characteristic reactions. No trace of increased tolerance or resistance on the part of Tenebrio was observed in either experiment. Larvae and pupae of Diataraxia oleracea (Lepidoptera) rapidly encapsulated parasites injected into them; adults made no visible reaction. Nemeritis larvae fed, grew and ecdysed in these adults, and only the premature death of the moth prevented the parasite’s development. In feeding larvae, resting larvae and adults of Calliphora erythrocephala (Diptera), the haemocytic and melanin reactions to injected parasites were both weak; in pupae the haemocytic reaction was weak but the melanin reaction strong. In the adult blowflies, parasite larvae lived as long as 7 days, but did not grow and seemed unable to use the food they had ingested. Observations recorded in this and the two preceding papers of the series are compared and discussed. The haemocytic reaction to Nemeritis , as observed in several orders of insects, is a true defence reaction and, when strong enough, leads to the death of the parasite. Deposition of melanin acts as a defence reaction only fortuitously, when the deposit is so sited as to prevent a vital activity, such as the hatching or the feeding, of the parasite. The reactions to Nemeritis of the different kinds of hosts so far investigated are distinguishable, but no constant difference has been observed that would serve to distinguish the reactions of exopterygote from those of endopterygote insects.

Distribution of Progeny by Cryptus inornatus Pratt (Hymenoptera: Ichneumonidae)

In a previous paper (Ullyett, 1949). the present writer outlined a tentative classification of insects serving as hosts to entomophagous parasites. This scheme was based upon the more obvious relationships that exist between parasite and host insect and those which might conceivably have some hearing upon the degree of efficiency with which the females of the former distribute their progeny among available hosts. Five main groups were recognized which reflected the differences occurring between the various kinds of hosts and parasites encountered in the field. Of these, examples have already been dealt with from two of the groups, viz., Group II, in which the host is normally active but is paralysed by the parasite before oviposition, as exemplified by the distribution of eggs by the Braconid, Microbracon hebetor Say among the larvae of Ephestia kuehniella Zell. (Ullyett. 1945); Group IIIA, in which the host is stationary and fully exposed as illustrated by the relationship between the eggs of Ephestia and the attack of Chelonus texanus Cress. (Ullyett, 1949).

The Cultivation of Trichomonas augusta (Protozoa) from Frogs

According to the compilations of Walton (1941) and of Morgan (1944), Trichomonas augusta has been reported from 19 species in 7 genera of urodele amphibians, from 33 species in 9 genera of anurans, and from one species of lizard. Trichomonas batrachorum is also fairly common in amphibia, but has not been reported from so many kinds of hosts: 2 species in 2 genera of urodeles, 22 species in 7 genera of anurans, 2 lizards and one snake. From these lists one might assume that T. augusta is the more hardy species, and the more successful in adapting itself to different kinds of hosts. Yet, if one places a frog's rectal contents containing both species into some of the culture media commonly employed for trichomonad flagellates, T. batrachorum will grow in almost any of them while T. augusta usually does not grow at all or, if it does develop for a short time, it will soon be overwhelmed by the more rapidly growing T. batrachorum. This situation has been a challenging one and on several occasions I have assigned to graduate students the problem of trying to cultivate T. augusta. Until recently these efforts have not succeeded in maintaining this species in vitro for more than about 2 weeks. Unexpected success was attained in the winter of 1914 4 5.

STUDIES ON NATURAL IMMUNITY TO PNEUMOCOCCUS TYPE III

AMONG THE EXPERIMENTAL FINDINGS REPORTED IN THIS PAPER TO WHICH WE WISH TO GIVE PARTICULAR EMPHASIS ARE THE FOLLOWING: 1. The results which follow the intravenous injection into rabbits of two strains of Pneumococcus Type III of different degrees of virulence vary with the state of the capsule. Thus when this structure is completely developed both remain in the blood. A culture of either strain begins to become susceptible to the blood-clearing mechanism contemporaneously with the onset of capsular degeneration and the initiation of other concomitant changes at the surface of the organism (cf Paper II), which occur much earlier with the less virulent strain. 2. When, in either case, removal from the blood stream occurs, this is effected by the phagocytic cells of the body. There is no suggestion that a new or unknown mechanism is involved. The greatest share of the burden is borne by the fixed phagocytic cells of the liver and spleen, and to a less extent by those of the lung and bone marrow. Nevertheless, it has been demonstrated that the polymorphonuclear leucocytes may also participate. 3. Phagocytosis by the leucocytes of the normal animal either in intro or in vivo has been observed only at such a time as the capsule has become impaired. Ingestion of the organisms by the fixed tissue cells appears also to be effective only under the same condition and is accordingly observed with much younger cultures of the less virulent strain. 4. Following their removal from the blood and their accumulation within the fixed phagocytes of the organs, destruction of most of the cocci proceeds within 2 to 4 hours. Both strains are destroyed provided they are in the state favorable to phagocytic attack. 5. Evidence has been presented which indicates that just as in vitro, so in a local area of inflammation within the body, aging with attendant capsular loss and increasing susceptibility to phagocytosis may take place. 6. With organisms from either strain a variable period of lag follows their injection into the blood stream, even when they are introduced in a state of active multiplication and complete encapsulation. 7. Differences in virulence for rabbits of two strains of Pneumococcus Type III do not imply that this animal possesses a defensive mechanism which is absent in other species, since it has been possible to demonstrate similar differences when the organisms are injected intravenously into mice. This fact indicates that the factors determining the degree of virulence of these strains are to be sought in the organisms themselves, rather than in the kind of host.

The Egg Production of Ascaris lumbricoides

The daily egg production for several different species of parastic worms has been estimated by a comparison of the number of worms obtained by treatment with the egg output as determined by the dilution egg count. By this method Stoll (1923) obtained a figure of about 9,000 eggs per day for a female of Necator americanus and Sweet (1924) and Cort, Stoll and Grant (1926) estimated the daily output of a female of Ancylostoma duodenale to be several times as large. For Fasciolopsis buski Stoll, Cort and Kwei (1927) have given an estimate of a daily output of about 25,000 eggs per worm. Faust and Khaw (1926) reported that the number of eggs produced by Clonorchis sinensis depended on the kind of host. For infestations in the cat their estimate was 2,400 eggs per day per worm, for the guinea pig 1,600, and for the dog 1,100. An egg output much higher than for any of these species would be expected for Ascaris lunibricoides, since these worms are of such large size and contain so many eggs in their uteri. Cram (1925) has recently estimated that the number of eggs in a single female ascaris may be as high as 27,000,000. We were, therefore, to some extent prepared for the high egg production figures obtained for this parasite from the study of two cases in which one of us (Brown) was able to make an egg-worm correlation in Panama.